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    • 专利摘要:
    A vertical Field Effect Transistor (FET) that may be an N-type FET (NFET) or a P-type FET (PFET); a multi-device vertical structure that may be two or more NFETs or two or more PFETS; logic gates including at least one vertical FET or at least one multi-device vertical; a Static Random Access Memory (SRAM) cell and array including at least one vertical FET; a memory array including at least one such SRAM cell; and the process of forming the vertical FET structure, the vertical multi-device (multi-FET) structure, the logic gates and the SRAM cell. The vertical FETs are epitaxially grown layered stacks of NPN or PNP with the side of a polysilicon gate layer adjacent the device's channel layer. The multi-FET structure may be formed by forming sides of two or more gates adjacent to the same channel layer or, by forming multiple channel layers in the same stack, e.g., PNPNP or NPNPN, each with its own gate, i.e., the side of a polysilicon gate layer. The SRAM cell may be radiation hardened by selectively thickening gate layers to increase storage node capacitance, providing high resistance cell wiring or by including a multi-layered gate oxide layer of NO or ONO, or by any combination thereof.
    公开号:US20010002715A1
    申请号:US09/002,399
    申请日:1998-01-05
    公开日:2001-06-07
    发明作者:Michael D. Armacost；Claude L. Bertin；Erik L. Hedberg；Jack A. Mandelman
    申请人:International Business Machines Corp；
    IPC主号:H01L27-11
    专利说明:
    [0001] The present invention is related to U.S. patent application Ser. No. 08/______ (Attorney Docket No. BU9-96-123) entitled “High Performance Direct Coupled FET Memory Cell” to Bertin et al., filed coincident herewith and assigned to the assignee of the present application. [0001] BACKGROUND OF THE INVENTION
    [0002] 1. Field of the Invention [0002]
    [0003] The present invention is related to integrated circuit (IC) chips and more particularly, to IC chips with CMOS SRAM cells and logic. [0003]
    [0004] 2. Background Description [0004]
    [0005] Integrated circuit (IC) chip developers' primary goals are faster, denser, lower power IC chips. Typical, state of the art IC chips are manufactured, currently, in the complementary insulated gate Field Effect Transistor (FET) technology, commonly referred to as CMOS. Normally, each generation of CMOS technology is identified by its minimum feature size, e.g. [0005]
    [0006] Since the active area (channel region) of any given circuit amounts to less than 10% of the entire area of the circuit, designers are acutely aware that, no matter how small a circuit is, circuit area may still be reduced. However, reducing feature size alone may lead to problems that require other, non-geometric solutions, such as enhanced circuit wiring layers. Even using these state of the art non-geometric enhancements, circuit area reduction falls far short of 90%. [0006]
    [0007] Reducing inactive area in an individual logic gate might have an insignificant impact on overall chip density. By contrast, reducing cell size in a Random Access Memory (RAM) array translates to a corresponding chip density improvement. [0007]
    [0008] However, benefits from reducing RAM cell area are often offset by increased radiation sensitivity. Even Static RAM (SRAM) cells become sensitive at some point to alpha particle or cosmic ray radiation. While these effects are exacerbated by reduced SRAM operating voltages, they may be offset by adding selected process features, such as selective cell node capacitance enhancement and increased cell wiring resistance. Unfortunately, these additional features increase SRAM cell size and write time. [0008]
    [0009] Consequently, designers have resorted to other approaches to reducing cell and circuit area, such as vertical devices, e.g., U.S. Pat. No. 5,414,289 to Fitch et al. entitled [0009]
    [0010] Fitch et al. teaches opening a hole through a conductor layer (the gate) that is sandwiched by two dielectric layers. A thin dielectric layer (gate oxide) is grown on the sides of the gate conductor layer in the hole. This gate oxide layer is a rough indicator of when channel growth should begin and when it should end. Consequently, Fitch et al.'s vertical FETs have substantial gate-drain and gate-source overlap with its associated overlap capacitance, which may be undesirable. This overlap capacitance is part of circuit load capacitance and contributes to other performance problems, such as Miller Effects. [0010]
    [0011] CMOS circuit power is largely a function of supply voltage (V[0011] h), circuit load capacitance (CL) and operating frequency (i.e., chip clock frequency fClk). The general CMOS circuit power (P) formula is P=CLVh 2fClk. Thus, improving performance (increasing fClk) and reducing power, requires reducing either CL or Vh or both.
    [0012] Although, with each feature size reduction, usually, there has been a corresponding reduction in V[0012] h, this has not been the case with CL. Furthermore, as feature size shrinks, wiring resistance (i.e., per unit line resistance) increases, increasing RC propagation delays, which offsets some performance gains.
    [0013] Thus, there is a need for CMOS technologies with reduced power supply voltage levels, reduced parasitic capacitance and wiring per unit length resistance, as well as reduced critical CMOS device parameters, such as channel length. [0013] SUMMARY OF THE INVENTION
    [0014] It is a purpose of the invention to improve FET channel length control. [0014]
    [0015] It is a goal of this invention to reduce FET channel length variations. [0015]
    [0016] It is another purpose of the present invention to improve CMOS logic and SRAM cell performance. [0016]
    [0017] It is yet another purpose of the present invention to improve SRAM cell radiation hardness without degrading cell performance. [0017]
    [0018] It is yet another purpose of the present invention to simultaneously achieve high speed and high density CMOS logic circuits, at low power dissipation levels. [0018]
    [0019] The present invention is a vertical Field Effect Transistor (FET) that may be an N-type FET (NFET) or a P-type FET (PFET), a multi-device vertical structure that may be two or more NFETs or two or more PFETs, logic gates including at least one vertical FET or at least one multi-device vertical structure, a Static Random Access Memory (SRAM) cell and array including at least one vertical FET, a memory array including at least one such SRAM cell and the process of forming the vertical FET structure, the vertical multi-device structure, the logic gates and the SRAM cell. [0019]
    [0020] The preferred vertical FETs are epitaxially grown layered stacks of NPN (for a NFET) or PNP (for a PFET). The side of a gate layer, preferably polysilicon, adjacent channel layer(s) in the stack is the gate of the device. The preferred multi-FET structure may be formed from the same channel layer by forming sides of two or more gates or, by stacking multiple channel layers in the same stack, e.g., PNPNP or NPNPN, each channel layer with its own gate, i.e., the side of a polysilicon gate layer. Two of these preferred multi-FET structures may be combined to form a CMOS logic gate by connecting together one end of each stack and connecting corresponding gates together. The preferred SRAM cell, made from the preferred embodiment FETs, may be radiation hardened by selectively thickening gate layers to increase storage node capacitance, providing high resistance cell wiring, including a multi-layered gate oxide layer of NO or ONO, or by any combination thereof. [0020] BRIEF DESCRIPTION OF THE DRAWINGS
    [0021] The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which: [0021]
    [0022] FIG. 1 is a flow diagram for forming FETs according to a preferred embodiment of the present invention; [0022]
    [0023] FIGS. [0023] 2A-B are, respectively, a top view of a wafer and a cross-sectional view through the wafer after the first step in forming an individual vertical FET according to the preferred embodiment of FIG. 1;
    [0024] FIGS. [0024] 3A-F are cross-sectional views illustrating the steps in forming one or more preferred embodiment FETs;
    [0025] FIGS. [0025] 4A-B are cross-sectional views of the above preferred embodiment FET as in FIG. 3F after the optional enhancement steps of forming pass through contacts;
    [0026] FIG. 5 is a cross-sectional view of the above preferred embodiment FET as in FIG. 3F with a thickened gate layer; [0026]
    [0027] FIG. 6 is a cross-sectional view of a high resistance interdevice wiring strap between a device region and a gate for improving SRAM cell radiation hardness; [0027]
    [0028] FIG. 7 is a topographical schematic of a preferred embodiment six device SRAM cell; [0028]
    [0029] FIG. 8 is a plan view of a preferred embodiment cell of FIG. 7 showing the placement of preferred FETs in the cell; [0029]
    [0030] FIG. 9A is a plan view of cell I/O and latch wiring on the surface opposite the surface shown in FIG. 8; [0030]
    [0031] FIG. 9B is a plan view of cell I/O and latch wiring on the surface shown in FIG. 8; [0031]
    [0032] FIGS. [0032] 10A-H are cross-sectional views illustrating the steps in forming a two input logic gate;
    [0033] FIG. 11A is a topographical schematic representation of preferred embodiment logic gate according to FIGS. [0033] 10A-H;
    [0034] FIG. 11B is a plan view of I/O connections in the preferred embodiment logic gate of FIG. 11A; [0034]
    [0035] FIGS. [0035] 12A-C are cross-sectional views illustrating the steps in forming appropriate connections for Ground, Vh, two (2) inputs and an output on the logic gate in FIGS. 10A-H and 11A-B. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
    [0036] FIG. 1 is a flow diagram for forming FETs according to a preferred embodiment of the present invention. [0036]
    [0037] In its simplest form, the preferred embodiment of the present invention is a self-aligned vertical FET having both device characteristics and reduced device parasitic capacitance such as would normally be found in a self-aligned Silicon on Insulator (SOI) device. The preferred embodiment FET may be a short channel (0.1 micrometer (um)) N-type FET (NFET) or P-type FET (PFET). Complementary pairs of preferred self-aligned vertical devices (NFET:PFET) may be combined to provide CMOS equivalent circuits, e.g., a complementary pair of self-aligned preferred vertical devices (an NFET and a PFET) may be used as an invertor. Typical V[0037] h for a preferred embodiment circuit of preferred embodiment devices is <1.5V.
    [0038] Preferred embodiment FETs are formed on the surface of a semiconductor wafer, preferably a silicon wafer. A layered dielectric is formed on a surface of the silicon wafer. Thus, in step [0038] 50 the wafer is prepared, first by doping the silicon wafer with impurities to form a heavily doped buried layer. Preferably, the wafer is implanted with Boron to a concentration of 1.0×1020cm−3. Then, a layered dielectric is formed on the silicon wafer by depositing an oxide layer, a 0.5-1.0 micrometer (um) thick SiO2 layer, on the silicon wafer using chemical vapor deposition (CVD). Then a surface layer of nitride is formed on the oxide layer.
    [0039] Having prepared the wafer in step [0039] 50, slots are formed in the layered dielectric in step 52. FIG. 2A is a top view of a wafer after step 52 in forming a first preferred embodiment FETs. In this embodiment, individual devices are formed in each location, although two or more individual FETs may share a common gate. FIG. 2B is a cross-sectional view of the wafer area in FIG. 2A through A-A. The layered wafer is a silicon wafer 100 covered with an oxide layer 102, and a nitride (SiN) surface layer 104 on the oxide layer 102.
    [0040] First, trenches [0040] 106 are opened through the nitride surface layer 104, exposing the oxide layer 102 therebelow. The trenches 106 define slots 108 that are opened through the oxide layer 102 to the silicon wafer 100. The slots may be minimum features sized or any appropriately larger size. Preferably, the slots 108 are oriented along the wafer's <100>plane to maximize carrier mobility and minimize surface state density.
    [0041] Next, in step [0041] 54 as represented in FIG. 3A, nitride sidewall spacers 110, 112 are formed in the slots 108. A conformal nitride layer is deposited over the trench 106 and into the slots 108. The nitride layer is then etched using a Reactive Ion Etch (RIE) to remove the horizontal portions of the nitride layer from the surface, leaving sidewall spacers 110, 112 standing, lining the oxide in the slots 108. Then the oxide is selectively removed between adjacent slots 108, leaving nitride sidewall spacers 110, 112 behind. For the preferred embodiment individual device, sidewall spacer 112 is selectively removed to form vertical device region 114 and gate region 116, in FIG. 3B.
    [0042] In step [0042] 56, vertical silicon columns, which include layers 118 and 120, are grown epitaxially from silicon base layer 100 in regions 114 and 116. If the vertical device is to be an NFET, layer 118 is P-type silicon and layer 120 is N-type. Otherwise, if the vertical device is to be a PFET, layer 118 is N-type and layer 120 is P-type.
    [0043] The thickness of channel layer [0043] 118 determines the device channel length. Thus, because epitaxial layer thickness can be controlled precisely, preferred embodiment FETs, have much less channel length variation than prior art FETs form using conventional methods.
    [0044] So, for example, a 0.1 um nominal channel length, formed using a conventional technique would exhibit a variation of ±30 nm, which corresponds to a channel length ranging from 0.07 um to 0.13 um, nearly a 2× channel length variation. By contrast, the preferred epi technique provides a much tighter variation of ±5 nm, with a corresponding tight channel length range of from 0.95 um to 0.105 um, only a 1.1× variation. The preferred embodiment channel length design point may be reduced beyond the point where short channel effects would typically become a yield concern because of this improved channel length control. Thus, performance, power and density are improved, significantly over conventional techniques. [0044]
    [0045] Before completing epitaxial growth, a tetra-ethyl-oxy-silane (TEOS) plug [0045] 122 is formed in the gate region 116. TEOS is deposited on layer 118, planarized and, then, selectively removed from vertical device region 114, using an etch that is selective to nitride and silicon. After forming the TEOS plug 122, a final device layer 124 is grown epitaxially on layer 118 in device region 114. The final device layer 124 has the same conductivity type as layer 120, i.e., either both are P-type or, both are N-type. Thus, the preferred embodiment FET's source and drain are in layers 120 and 124.
    [0046] TEOS plug [0046] 122 is removed, exposing nitride sidewall spacer 110. The exposed portion of nitride sidewall spacer 110 is removed in gate region 116, leaving partial spacers 110′ in FIG. 3C and, partially exposing the sidewall of device region 114. An oxide spacer 126 is formed along the exposed sidewall of device region 114. Then, the upper surface 128 is planarized.
    [0047] After forming layered epi in device regions [0047] 114 and 116 for one device type in step 58, second device type layered epi columns are formed in identical device regions (not shown), essentially as described above for step 56. Thus, if the layered epi formed in step 56 is for NFETS, then, the layered epi formed in step 58 is for PFETs. Optionally, if only one device type is to be formed, step 58 may be omitted.
    [0048] A handle wafer [0048] 130 in FIG. 3D is attached to planarized surface 128 and the wafer is inverted to remove the semiconductor base wafer 100. The base wafer 100 is removed in two steps, using both Chem-Mech Polishing (CMP) and etching. The preferred two step removal utilizes the heavily doped layer (not shown), implanted into the base wafer in preparation step 50, as an etch stop layer. So, the bulk of the base layer 100 is removed at a relatively rapid rate (using etch and CMP) down to the etch stop layer. Then, the remainder is removed at a slower, more controlled rate until essentially the entire base layer 100 is removed to expose surface 133 in FIG. 3D. In an alternate embodiment, the base layer is etched using RIE until oxide by-products are detected.
    [0049] After removing the base layer [0049] 100, in step 60, gates are formed for the first type devices. Silicon layers 118 and 120 are removed in the gate region 116 to re-expose sidewall spacers 110′. Then, the re-exposed sidewall spacers 110′ are removed, preferably by isotropic etching, to expose the vertical channel surface 132, i.e., the side of layer 118. Next a gate oxide layer 134 is grown on the exposed silicon and a gate layer 136, preferably of polysilicon, is formed on the gate oxide layer 134. The gate layer 136 is, preferably, the same thickness as, or slightly thicker than, channel layer 118 to assure slight gate overlap from the channel 132 into the source/drain diffusion layer 120.
    [0050] In the preferred embodiment FET, the gate layer [0050] 136 is, preferably, a doped polysilicon layer 136, directionally deposited by collimated sputtering from a silicon target. As a result of collimated sputtering, the deposited silicon exhibits a
    [0051] Thus, the sidewall areas of gate layer [0051] 136 may be removed using an isotropic chemical dry etching (CDE), leaving polysilicon only on horizontal surface 133, oxide spacer 126, and in gate regions 116. The resulting FET gate 136′ in FIG. 3E is thick enough to span the entire channel 132 without excessive overlap. Insulating material, preferably TEOS, is deposited on the wafer. Excess insulating material and surface polysilicon are removed from the wafer's surface, preferably using CMP, which replanarizes surface 133 and leaving an insulating plug 138 above the gate 136′.
    [0052] Next, in step [0052] 62, gates are formed for the second type FETs, essentially as described for the first type FETs. If the step 58 of growing the second type layered epi was omitted, then this step is also omitted.
    [0053] After forming the preferred individual FETs, in step [0053] 64, contacts may be formed selectively to the FET's source, drain and gate. In preparation for forming these contacts, a second handle wafer 140 in FIG. 3F is attached to planarized surface 133 and the first handle wafer 130 is removed. The wafer is inverted, patterned and contacts 142 are formed through oxide fill 126, preferably using RIE to open vias to gates 136′. Then, the open vias are filled with a conductor, preferably Tungsten, and the surface 128 is re-planarized, using an appropriate CMP technique.
    [0054] A metal wiring pattern is formed on the planarized surface [0054] 128. The wiring pattern includes conductors 144 to gate contacts 142 and conductors 146 to device source/drain diffusions 124. Oxide is formed on the surface 128 filling spaces between wiring lands, e.g., between 144 and 146. The oxide is planarized forming planar surface 148.
    [0055] Finally, in step [0055] 66, supply, ground and external I/O connections are made to complete the preferred embodiment vertical FETs.
    [0056] As described hereinabove, the length of such a device is the thickness of the channel layer [0056] 118, nominally 0.1 um. The device width is determined by slot width and varies from a minimum, as determined by minimum feature size, to any selected maximum width. Thus, it can be seen that even for a quarter micron process, with a 0.25 um minimum feature size, the width to length (w/l) ratio of a minimum device is 2.5 and increases rapidly with slot width.
    [0057] It can be readily appreciated that, by providing appropriate wiring to six such preferred embodiment FETs, a SRAM cell may be formed. Four minimum w/l devices are connected to form a latch with two wider pass gate devices between the latch and a pair of bit lines. However, without additional gate contacts/wiring, including pass through contacts, optimum SRAM cell density, performance and stability is still not achievable. [0057]
    [0058] Thus, FIGS. [0058] 4A-B represent an above preferred embodiment FET as in FIG. 3F including the additional optional pass through contacts or contact vias. These optional pass through contacts are formed after the structure of FIG. 3F. A third handle wafer 150 is attached to planar surface 148 and the second handle wafer 140 is removed. Again, the wafer is inverted and vias 152, in FIG. 4A, are formed through plugs 138. The vias 152 are filled with an appropriate conducting material and surface 133 is replanarized. As with surface 128 in FIG. 3F, a wiring layer may be applied to surface 133. Thus, having added the capability of contacting the gate layer 136′ from above or below, or both, these top and bottom contacts may be selectively omitted from individual devices to provide added wiring flexibility.
    [0059] Optionally, in FIG. 4B, prior to filling vias [0059] 152 with conducting material, a second via 154 may be opened through gate layer 136′ to contact 142. Then, both vias 152 and 154 are filled with conducting material and surface 133 is re-planarized.
    [0060] Further enhancements may be added to the preferred embodiment FETs to improve SRAM radiation hardness. For example, in FIG. 5 gate [0060] 136″ is selectively thickened to increase gate overlap capacitance. Inclusion of such a device in an SRAM cell increases storage node capacitance, which increases the charge required for a transient, such as an alpha particle, to upset the cell. Selective thickening of the gate layer 136″ in FIG. 5 is accomplished when the gate layer is deposited in step 60 and/or step 62. Typically, the gates of all vertical FETs, all vertical PFETs or all vertical NFETs are thickened to increase gate-source capacitance. Preferably, individually selected FETs would have their gates thickened.
    [0061] Another enhancement, in FIG. 6, is a high resistance interdevice wiring strap [0061] 160 that may be used to connect the drain or source 162 of one device through contact 164 to the gate 166 of another. A conductive barrier layer 168 is required between drain/source 162 and the high resistance strap 160 to prevent dopant in drain/source 162 from contaminating high resistance strap 160, lowering its resistance. Such an alternate embodiment SRAM, with cells including either of these variations would have improved radiation hardness, at a penalty of only a slightly longer cell write time.
    [0062] Additionally, radiation protection may be further enhanced by forming a multi-layered gate oxide of a high permittivity material. For example, instead of SiO[0062] 2, the gate layer may be a Nitride-Oxide layer or an Oxide-Nitride-Oxide layer.
    [0063] FIG. 7 is a topographical schematic of a preferred embodiment six device SRAM cell [0063] 170. FIG. 8 represents the placement of the six vertical transistors 172, 174, 176, 178, 180 and 182 in the preferred embodiment SRAM cell 170 of FIG. 7. Each transistor 172-182 includes a vertical layered epi stack 170 s-180 s and gate 170 g-180 g. Low resistance straps 184 and 185, preferably a metal such as W, Al, Cu, a silicide or a laminate thereof, connect the source of cell pass gates 180 and 182 to the cell latch's internal nodes through the gates of corresponding latch devices 172, 174 and 176, 178, respectively. Gates 180 g and 182 g are shared with adjacent cells (not shown).
    [0064] FIGS. [0064] 9A-B represent the cell 170 including the cell wiring in FIG. 7 not shown in FIG. 8. Internal straps 186, 188, which complete latch wiring, are on the surface opposite that shown in FIG. 8. Internal straps 186, 188 are low resistance wiring or, optionally, are high resistance straps of FIG. 6. Gates 180 g and 182 g are connected to word line 190. The drains of devices 180 and 182 are connected to a complementary bit line pair 192, 194. The word line 190 and complementary bit line pair 192, 194 are shared with adjacent cells (not shown).
    [0065] In FIG. 9B, the source of devices [0065] 174 and 178 are connected to ground 196 and the sources of devices 172, 176 are connected to an array supply voltage 198. Ground line 196 and supply line 198 are shared with adjacent cells (not shown). An array of such preferred embodiment SRAM cells 170 is much denser than prior art SRAM arrays.
    [0066] In yet another preferred embodiment, the individual vertical device of the first preferred embodiment is expanded and adapted for forming very dense logic devices, e.g., CMOS NAND and NOR gates. In this preferred embodiment, two or more vertical devices are formed in the same device region or stack. Thus, two or more vertical devices may be stacked in a single stack, effectively connected in series, for further density improvement; or, two or more gates may be provided to the same channel of a single vertical device region, e.g., at opposite sides, to form two or more parallel FETs. Thus, by combining series connected stacked devices of one type with parallel FETs of the other type, very compact CMOS gates (NAND, NOR) are formed. [0066]
    [0067] FIGS. [0067] 10A-H represent forming a two input gate according to the steps in FIG. 1. In this example a two input NAND gate is formed, as represented schematically in FIG. 11A. FIG. 10A is a top view after step 52, analogous to FIG. 2A. FIGS. 10B-H are cross-sectional views through B-B and are analogous to stages of the individual transistor preferred embodiment in FIGS. 2B and 3A-3F.
    [0068] Unless specifically indicated otherwise, all materials, dimensions and other parameters are identical for the multiple transistor example of FIGS. [0068] 10A-H as for the individual transistor embodiment of FIGS. 2A-B and 3A-3F. So, the wafer in FIGS. 10A and 10B, includes a semiconductor base layer 200, preferably silicon, an oxide layer 202 on the base layer 200 and a surface nitride layer 204.
    [0069] An N device trench [0069] 206 and a P device trench 208 are opened through the nitride surface layer 204, exposing the oxide layer 202 therebelow. Slots 210 are opened through the oxide layer 202 to the silicon wafer 200 in the trench 206. Preferably, as in the individual vertical embodiment, slots 210 are oriented along the wafer's <100> plane to maximize carrier mobility and minimize surface state density.
    [0070] Next, in step [0070] 54 as represented in FIG. 10C, nitride sidewall spacers 212 are formed in the slots 210. A conformal nitride layer is deposited over the trenches 206, 208 and into the slots 210. The nitride layer is then reactive ion etched to remove it from horizontal surfaces, leaving sidewall spacers 212 standing in the slots 210, lining the oxide. Then, the oxide is selectively removed between adjacent slots 210, leaving only nitride sidewall spacers 212 behind. Unlike FIG. 3A above, none of the sidewall spacers 212 are removed for the multiple device embodiment. Thus, the sidewall spacers 212 form vertical device regions 214 and gate regions 216.
    [0071] Next, in step [0071] 56 as represented in FIG. 10D, a layered epi is formed for the two stacked N-type FETs. Layers 218, 220, 222, 224 and 226, are grown epitaxially in N-type device region 228 and, selectively in gate regions 230, 232. However, P-type device region 234 and gate region 236 are filled with TEOS to avoid prematurely forming the epi layers there. The PFET regions are protectively masked during NFET formation.
    [0072] First, N-type layer [0072] 218 and P-type layer 220 are epitaxially grown in N-type regions 228, 230 and 232. TEOS is deposited in all three regions and, then, selectively removed from regions 228 and 230, leaving gate region 232 filled with a TEOS plug 240 above layer 220.
    [0073] Next, N-type layer [0073] 222 and P-type layer 224 are epitaxially grown in N-type regions 228 and 230. TEOS is deposited in both regions 228 and 230 and, then, selectively removed from device region 228, leaving gate region 230 filled with a TEOS plug 242 above layer 224. Finally, N-type layer 226 is epitaxially grown in N-type device region 228 to complete the series NPNPN structure of the stacked N-type FETs.
    [0074] Next, in step [0074] 58, the second type (PFET) layered epi is grown for a pair of parallel PFETs. A mask 244 in FIG. 10E, is formed over N-type regions 228, 230 and 232 and oxide 238, 238′ is removed from the P-type gate regions 236 and from P-type device region 234. P-type layer 246 and N-type layer 248 are formed in device region 234 and gate areas 236. Next, PFET regions 234, 236 are filled with TEOS, which is removed from device region 234, leaving plugs 250 in the gate regions 236. Finally, P-type device layer 252 is grown epitaxially in device region 234.
    [0075] Plugs [0075] 240, 242 and 250 are removed, partially exposing nitride sidewall spacers 212. The exposed potions of each nitride sidewall spacer 212 is removed leaving partial spacers 212′ in FIG. 10F in gate regions 230, 232 and 236, and partially exposing device regions 228 and 234. Oxide fill 254 is formed along the exposed sides of device regions 228 and 234 and the wafer is planarized leaving planar surface 256.
    [0076] The wafer is inverted and the semiconductor base wafer [0076] 200 is removed. So, a handle wafer 258 is attached to planarized surface 256 and, then, base wafer 200 is removed using CMP and etching to expose surface 260. The buried etch stop layer allows removing the bulk of the base layer 200 using etching and CMP at a relatively rapid rate until the etch stop layer is exposed and the remaining base layer is removed at a slower more controlled rate thereafter. Etchants such as ethylenediamine-pyrocatecho-water (EPW) or potassium hydroxide (KOH) are known to stop at a boron doped buried layer such as was formed above when the wafer was prepared by implanting the heavily doped layer. Alternatively, the base layer 200 is etched using RIE until oxide by-products are detected.
    [0077] Gates are formed for the first type devices in step [0077] 60, after removing the base layer 200. A non-erodible mask (NEM) 262, 264 (sometimes referred to in the art as a
    [0078] Next, a gate oxide layer [0078] 270 in FIG. 10G, is grown on the exposed silicon and a gate layer 272 is formed on the gate oxide layer 270. Preferably, the gate layer 272 is the same thickness as, or slightly thicker than channel layers 220 and 224 to assure sufficient channel overlap by the gate. As in the individual device preferred embodiment FET, the gate layer 272 is a directionally deposited doped polysilicon layer, deposited by collimated sputtering from a silicon target to achieve the
    [0079] Unwanted areas of gate layer [0079] 272 are etched isotropically using CDE to leave polysilicon only on horizontal surfaces, with gates 272′ and 272″ in FIG. 10H, thick enough to span each respective channel 266 and 268 without excessive overlap. Remaining mask 264 is removed and TEOS is deposited over the wafer to fill spaces 274 above the gates 272′, 272″ of the stacked N-type transistors. Excess TEOS and surface polysilicon is removed.
    [0080] In step [0080] 62, gates are formed for the vertical P-type transistors, repeating the steps as described for the N-type devices. So, first, the N-type devices and the P-type device region 234 are masked and silicon layers 246 and 248 are removed from P-type gate areas 234 to expose sidewall spacers 212′. Then, the sidewall spacers 212′ and remaining mask structures may be removed. A gate oxide layer 276 is formed on exposed silicon and a polysilicon gate layer is sputtered onto the gate oxide layer 276. Excess polysilicon is removed to form gates 278, 280. TEOS plugs 282, 284 plug the spaces above the gates 278, 280. The structure thus formed is similar to the individual device stack structure of FIG. 3E.
    [0081] I/O connections are formed for the logic gate example of FIGS. [0081] 10A-H as represented in FIG. 11B and schematically represented in FIG. 11A, which is, in this example, a two input NAND gate 286. The connections of FIG. 11B may be formed on either surface. Besides the ground connection and supply connection 288 in FIG. 11A, NAND gate 286 has a pair of input straps 290 and an output strap 292. The output strap 292 couples NFET device region 228 with PFET device region 234. The input straps 290 couple NFET gates 272′ and 272″ in gate regions 230 and 232 with PFET gates 278 and 280, respectively, in gate regions 236. In the preferred embodiment, ground and supply connections are made prior to step 64 of forming straps 290, 292 instead of as part of step 66.
    [0082] Traditional chip wiring, on a single chip surface, is inadequate for such a vertical logic gate as it is with the preferred embodiment SRAM cell. Thus, appropriate connections for Ground, V[0082] h, as well as to the two (2) inputs 290 and output 292 are formed in steps 64 and 66 as represented in FIGS. 12A-C, which provide a cross-sectional view of the two input NAND gate formed in FIGS. 10A-H. The NAND gate includes a pair of stacked NFETs 228 and a pair of parallel PFETs 234.
    [0083] First, as noted above, the ground and supply layers are formed. With the handle layer [0083] 258 still attached, a metal layer 300 in FIG. 12A is deposited on the surface 302 of the wafer to provide Vh to the P-type device area 234. Thus, the supply layer 300 contacts the source 304 of the parallel PFETs 234. The supply layer 300 is patterned using any appropriate photolithographic patterning technique.
    [0084] Preferably, ground lines are formed above the supply layer [0084] 300 to maximize decoupling capacitance. So, a layer 306 of high dielectric material, such as Barium-Strontium-Titanate oxide (BST) or Tantalum Pentoxide is deposited on the patterned supply layer 300. Ground contacts 308 are opened through the dielectric layer 306 and supply layer 300 to the source 310 of the NFET transistor stack 228. A ground layer 312 of metal is deposited on the high dielectric layer 306, contacting the exposed source 310 in device region 228. An insulating layer 314, preferably SiO2, is formed over the ground layer 312. The insulating layer 314 is planarized using CMP or any appropriate planarization technique. It should be appreciated that the ground layer 312 could be formed on surface 302 prior to forming supply layer 300 without departing from the present invention.
    [0085] A silicon wafer [0085] 316 is attached to the planarized surface 318 of layer 314 and the wafer is inverted for step 64. The handle wafer 258 is removed and contact vias 320 in FIG. 12B are etched, preferably using RIE, through oxide fill 254 to gates 272′, 272″, 278 and 280 in gate regions 230, 232, and 236 respectively. Then, the contact vias 320 are filled with a conductor, preferably Tungsten, and the surface 322 is planarized, preferably using any well known CMP technique.
    [0086] The NAND gate wiring, [0086] 290, 292 of FIGS. 11A-B is formed in step 64 on the planarized surface 322 to gate contacts 320 and drains 324 and 326. An oxide layer 328 is deposited on the surface 322 filling spaces between wiring lands 290, 292. The oxide layer 328 is planarized forming planar surface 330.
    [0087] Chip wiring, connecting the logic gate to other logic gates, is formed on the planarized surface [0087] 330 in step 66. An insulating layer 332 in FIG. 12C is formed on surface 322 and patterned to open contact vias to inputs 290. Alternatively, oxide layer 328 may be formed to a thickness sufficient to omit this insulating layer 332. A conducting layer, preferably a metal, is deposited on the insulating layer 332 and patterned to form the first interconnection layer, including input connections 334, 336 to inputs 290.
    [0088] Next, an insulating layer [0088] 338 is formed on the first interconnection layer. Preferably, both insulating layers 332 and 338 are of a low dielectric material such as SiO2, an insulating polymer or air to reduce wiring capacitance. Contacts are opened through both insulating layers 332 and 338 as required to output 290. A final layer of conducting material is deposited on the patterned insulating layer 338. The final metal layer is patterned to form the second interconnection layer, including connection 340 to output 290 and wiring land 342.
    [0089] Once the final metal layer has been formed in step [0089] 66, if desired, the wafer may be further passivated with an appropriate passivation layer (not shown) and provided with suitable terminal metal layers (not shown) for off chip connection.
    [0090] While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. [0090]
    权利要求:
    Claims (55)
    [1" id="US-20010002715-A1-CLM-00001] 1. A Field Effect Transistor (FET) comprising:
    a layered semiconductor stack having a channel layer of a first conduction type between a pair of layers of a second conduction type;
    a gate insulator layer on a sidewall of said semiconductor stack; and
    a gate layer, a side of said gate layer adjacent said gate insulator layer extending along said channel layer, said side forming a gate of the FET.
    [2" id="US-20010002715-A1-CLM-00002] 2. The FET of
    claim 1 wherein semiconductor stack is a silicon stack.
    [3" id="US-20010002715-A1-CLM-00003] 3. The FET of
    claim 2 wherein the silicon stack is an epitaxially grown silicon stack.
    [4" id="US-20010002715-A1-CLM-00004] 4. The FET of
    claim 3 wherein the first conduction type is P-type and the second conduction type is N-type.
    [5" id="US-20010002715-A1-CLM-00005] 5. The FET of
    claim 3 wherein the first conduction type is N-type and the second conduction type is P-type.
    [6" id="US-20010002715-A1-CLM-00006] 6. The FET of
    claim 3 wherein the gate insulator layer comprises a layer of SiO2.
    [7" id="US-20010002715-A1-CLM-00007] 7. The FET of
    claim 6 wherein the gate insulator layer further comprises a nitride layer.
    [8" id="US-20010002715-A1-CLM-00008] 8. The FET of
    claim 7 wherein the gate insulator layer comprises a layer of ONO.
    [9" id="US-20010002715-A1-CLM-00009] 9. The FET of
    claim 3 wherein the gate layer is a layer of polysilicon.
    [10" id="US-20010002715-A1-CLM-00010] 10. The FET of
    claim 9 wherein the polysilicon gate layer is as thick as the channel layer.
    [11" id="US-20010002715-A1-CLM-00011] 11. The FET of
    claim 9 wherein the polysilicon gate layer is substantially thicker than the channel layer.
    [12" id="US-20010002715-A1-CLM-00012] 12. An integrated circuit (IC) including a plurality of Field Effect Transistors (FETs), at least one said FET comprising:
    a layered epitaxial semiconductor stack having a channel layer of a first conduction type between first and second layers of a second conduction type;
    a gate insulator layer on a sidewall of said epitaxial semiconductor stack; and
    a gate layer, a side of said gate layer adjacent said gate insulator layer extending along said channel layer, said side forming a gate of the FET.
    [13" id="US-20010002715-A1-CLM-00013] 13. The IC of
    claim 12 wherein the epitaxial semiconductor stack is an epitaxially grown silicon stack.
    [14" id="US-20010002715-A1-CLM-00014] 14. The IC of
    claim 13 wherein said at least one FET is at least two FETs, the second FET of said at least two FETs further comprising:
    a second channel of a third conduction type in a channel layer between third and fourth conduction layers of a fourth conduction type;
    a second gate insulator layer on a sidewall of said channel layer; and
    a second gate layer, a side of said second gate layer adjacent said gate insulator layer extending along said second channel and forming said second FET's gate.
    [15" id="US-20010002715-A1-CLM-00015] 15. The IC of
    claim 14 wherein the third and fourth conduction layers are the first and second layers, the third conduction type is the first conduction type, the fourth conduction type is the second conduction type, said second sidewall is opposite said first sidewall, said second channel is in said channel layer and said second gate layer is coplanar with said first gate layer.
    [16" id="US-20010002715-A1-CLM-00016] 16. The IC of
    claim 14 wherein the third conduction layer is the second conduction layer, said second channel is in a second channel layer, the second conduction layer is between the first and second channel layer, the third conduction type is the first conduction type, and the fourth conduction type is the second conduction type.
    [17" id="US-20010002715-A1-CLM-00017] 17. The IC of
    claim 14 further comprising:
    a second epitaxial silicon stack, wherein the second FET is in the second epitaxial silicon stack.
    [18" id="US-20010002715-A1-CLM-00018] 18. The IC of
    claim 17 , wherein the at least two FETs are cross coupled FETs in a SRAM cell, the first and third conduction types are P-type and the second and fourth conduction types are N-type.
    [19" id="US-20010002715-A1-CLM-00019] 19. The IC of
    claim 17 , wherein the at least two FETs are cross coupled FETs in a SRAM cell, the first and third conduction types are N-type and the second and fourth conduction types are P-type.
    [20" id="US-20010002715-A1-CLM-00020] 20. The IC of
    claim 17 , wherein the at least two FETs are complementary FETs in an invertor, the first and fourth conduction types are P-type and the second and N-type conduction types are N-type.
    [21" id="US-20010002715-A1-CLM-00021] 21. A logic gate including at least one pair of Field Effect Transistors (FETs), said at least one pair of FETs comprising:
    a layered epitaxial silicon stack having a first channel and a second channel of a first conduction type, said first channel being between first and second layers of a second conduction type and said second channel being between a said second layer and a third layer of said second conduction type;
    a first gate insulator layer on a first sidewall of said epitaxial semiconductor stack;
    a second gate insulator layer on a second sidewall of said epitaxial semiconductor stack;
    a first gate layer, a side of said first gate layer adjacent said first gate insulator layer extending along said first channel, said side of said first gate layer forming a first FET's gate; and
    a second gate layer, a side of said second gate layer adjacent said second gate insulator layer extending along said second channel, said side of said second gate layer forming a second FET's gate.
    [22" id="US-20010002715-A1-CLM-00022] 22. The logic gate of
    claim 21 wherein at least one pair is at least two pair,
    the first and third conduction layers of a first said pair being the same layer, said first and second channels being first and second sidewalls of said channel layer,
    the second channel of a second pair of said at least two pair being in a second channel between said second and third conduction layer, said second conduction being between the first and second channel layers, and
    a strap, said second layer of said first pair being connected by said strap to said third layer of said second pair.
    [23" id="US-20010002715-A1-CLM-00023] 23. The logic gate of
    claim 21 being a NAND gate wherein the first said pair of FETs is a pair of P-type FETs and the second said pair of FETs is a pair of N-type FETs, a first input being connected to the first gate of each said pair, a second input being connected to the second gate of each said pair and the strap being the NAND gate's output.
    [24" id="US-20010002715-A1-CLM-00024] 24. The logic gate of
    claim 21 being a NOR gate wherein the first said pair of FETs is a pair of N-type FETs and the second said pair of FETs is a pair of P-type FETs, a first input being connected to the first gate of each said pair, a second input being connected to the second gate of each said pair and the strap being the NOR gate's output.
    [25" id="US-20010002715-A1-CLM-00025] 25. An array of SRAM cells, each of said SRAM cells comprising:
    a pair of cross coupled invertors, each said invertor including a pair of vertical FETs, each of said vertical FETs comprising:
    a layered epitaxial silicon stack, said layered epitaxial silicon stack comprising a source layer, a channel layer on said source layer and a drain layer on said channel layer,
    a gate insulator layer at a sidewall of said channel layer, and
    a polysilicon gate layer, a side of said gate forming said FET's gate; and
    a pair of pass gates, each said pass gate being an individual said vertical FET and coupled to one side of said cross coupled invertors.
    [26" id="US-20010002715-A1-CLM-00026] 26. The array of
    claim 25 wherein the pair FETs in the of cross coupled invertors is a PFET and a NFET and the pass gates are NFETs.
    [27" id="US-20010002715-A1-CLM-00027] 27. The array of
    claim 26 wherein the gate insulator layer comprises a layer of SiO2.
    [28" id="US-20010002715-A1-CLM-00028] 28. The array of
    claim 27 wherein the gate insulator layer further comprises a nitride layer.
    [29" id="US-20010002715-A1-CLM-00029] 29. The array of
    claim 28 wherein the gate insulator layer comprises a layer of ONO.
    [30" id="US-20010002715-A1-CLM-00030] 30. The array of
    claim 26 wherein the polysilicon gate layer is as thick as the channel layer.
    [31" id="US-20010002715-A1-CLM-00031] 31. The array of
    claim 26 wherein the polysilicon gate layer of the PFETs is substantially thicker than the channel layer.
    [32" id="US-20010002715-A1-CLM-00032] 32. The array of
    claim 26 further comprising at least one resistive strap connecting the output of one of said invertors to the other invertor's input, whereby a level change at said output is delayed from reaching said input.
    [33" id="US-20010002715-A1-CLM-00033] 33. The array of
    claim 32 wherein at least one resistive strap is two resistive straps, each of said resistive straps connecting the output of one of said invertors to the other invertor's input, whereby a level change at one said output is delayed from reaching the other said input.
    [34" id="US-20010002715-A1-CLM-00034] 34. A method of forming Field Effect Transistors (FETs), said method comprising the steps of:
    a) growing layered epitaxial stacks on a surface of a semiconductor substrate, said layered epitaxial stacks having a channel layer between a pair of conduction layers, a plurality of said layered epitaxial stacks being in device regions;
    b) growing a gate insulator layer along at least one sidewall of each of said plurality layered epitaxial stacks in device regions;
    c) forming a gate layer on said gate insulator layer; and
    d) selectively removing said gate layer from said gate insulator layer, said gate layer remaining in gate regions and laterally extending from said gate insulator layer at said channel, the side of said gate layer in each said gate region forming the gate of a FET.
    [35" id="US-20010002715-A1-CLM-00035] 35. The method of
    claim 34 wherein the step (a) of growing the epitaxial stack comprises the steps of:
    1) growing a layered dielectric on a semiconductor wafer;
    2) opening a plurality of trenches through a surface layer of said layered dielectric;
    3) opening a plurality of slots in each of said trenches to said semiconductor wafer;
    4) forming a plurality of sidewall spacers in said slots;
    5) removing any remaining dielectric from between said slots, said sidewall spacers defining said device regions and said gate regions; and
    6) growing said epitaxial stack in said slots on said semiconductor wafer.
    [36" id="US-20010002715-A1-CLM-00036] 36. The method of
    claim 35 further comprising, before the step (6) of growing the epitaxial stack, the step of:
    5a) selectively removing one or more sidewall spacers from said slots.
    [37" id="US-20010002715-A1-CLM-00037] 37. The method of
    claim 35 wherein the step (b) of growing the gate insulator layer comprises the steps of:
    1) selectively removing portions of said epitaxial stack in said gate regions to expose one or more stack sidewall; and
    2) forming said gate insulator layer on each said exposed stack sidewall.
    [38" id="US-20010002715-A1-CLM-00038] 38. The method of
    claim 37 , wherein one or more stack sidewall is two sidewalls of each epitaxial stack in one of said device regions and said gate insulator is formed on said two sidewalls.
    [39" id="US-20010002715-A1-CLM-00039] 39. The method of
    claim 37 , wherein the step (b1) of selectively removing epitaxial stack portions comprises the steps of:
    i) selectively removing a first of said pair of conduction layers to expose said channel layer and upper portions of sidewall spacers in said gate regions;
    ii) removing said upper portions of said sidewall spacer;
    iii) filling said gate regions with an insulating material;
    iv) removing said semiconductor substrate to expose the other conduction layer of said pair;
    v) selectively removing said other conduction layer and said channel layer in said gate regions to expose remaining portions of said sidewall spacers and said insulating material filling said gate regions;
    vi) removing said remaining sidewall spacer portions to expose sidewalls of said layered epitaxial stacks in device regions; and
    vii) forming a gate insulator layer on said exposed sidewalls.
    [40" id="US-20010002715-A1-CLM-00040] 40. The method of
    claim 37 wherein the step (c) of forming the gate layer comprises directionally depositing a layer of conductive material by collimated sputtering from a target of said conductive material.
    [41" id="US-20010002715-A1-CLM-00041] 41. The method of
    claim 40 , further comprising after the step (d) of selectively removing the gate layer, the step of:
    e) filling said gate regions with an insulating material;
    f) opening contacts through said insulating material in said gate regions to said gate layer; and
    g) filling said contacts with conducting material.
    [42" id="US-20010002715-A1-CLM-00042] 42. The method of
    claim 41 , wherein at least two of said FETs are FETs in a FET stack of two or more FETs, said FET stack having a layered epitaxial stack of alternating channel layers and conduction layers.
    [43" id="US-20010002715-A1-CLM-00043] 43. The method of
    claim 42 wherein two or more FETs is two FETs, said first conduction layer of said pair being removed in two gate regions adjacent to said FET stack and further comprising after the step (1(i)) the step of:
    iA) selectively removing, in one of said two gate regions, one of two said channel layers and a conduction layer between said two channel layers.
    [44" id="US-20010002715-A1-CLM-00044] 44. The method of
    claim 43 , further comprising the step of:
    h) strapping one of said pair of conduction layers of said FET stack to one of said pair conduction layers in a second device region; and
    j) strapping each gate contact of said two FETs to a corresponding gate contact to a gate adjacent said second device region.
    [45" id="US-20010002715-A1-CLM-00045] 45. The method of
    claim 41 , further comprising the step of:
    h) strapping one of said pair of conduction layers of said FET stack to one of said pair conduction layers in a second device region; and
    j) strapping each gate of said two FETs to a corresponding gate adjacent said second device region.
    [46" id="US-20010002715-A1-CLM-00046] 46. A method of forming an array of SRAM cells, said method comprising the steps of:
    a) forming a plurality of sidewall spacers on a surface of a semiconductor wafer, said sidewall spacers defining said device regions and said gate regions; and
    b) growing layered epitaxial stacks on said semiconductor wafer between said sidewall spacers, said layered epitaxial stacks having a channel layer between a pair of conduction layers;
    c) selectively removing a first of said pair of conduction layers to expose said channel layer and upper portions of sidewall spacers in said gate regions;
    d) removing said upper portions of said sidewall spacer and filling said gate regions with an insulating material;
    e) removing said semiconductor wafer to expose the other conduction layer of said pair;
    f) selectively removing said other conduction layer and said channel layer in said gate regions to expose remaining portions of said sidewall spacers and said insulating material and removing said remaining sidewall spacer portions to expose sidewalls of said layered epitaxial stacks in device regions;
    g) forming a gate insulator layer on said exposed sidewalls;
    h) forming a gate layer on said gate insulator layer;
    j) selectively removing said gate layer from said gate insulator layer, said gate layer remaining in gate regions and laterally extending from said gate insulator layer at said channel, the side of said gate layer in each said gate region forming the gate of a FET;
    k) filling said gate regions with an insulating material;
    l) opening contacts through said insulating material in said gate regions to said gate layer; and
    m) filling said contacts with conducting material.
    [47" id="US-20010002715-A1-CLM-00047] 47. The method of
    claim 46 , wherein the array of SRAM cells is an array of CMOS SRAM cells and wherein the step (a) of forming sidewall spacers comprises the steps of:
    1) forming trenches in a plurality of cell areas through a surface layer of a layered dielectric on said semiconductor wafer, at least one trench in each said cell area being wider than other said trenches in said each cell area;
    2) forming a plurality of slots to said semiconductor wafer in said trenches;
    3) conformally depositing a layer of the same material as said surface layer over said surface layer and into said slots; and
    4) reactive ion etching said conformally deposited layer such that sidewalls of said deposited material are left in said slots.
    [48" id="US-20010002715-A1-CLM-00048] 48. The method of
    claim 47 wherein the step (g) of forming the gate layer comprises:
    directionally depositing a first layer of conductive material by collimated sputtering from a target of said conductive material.
    [49" id="US-20010002715-A1-CLM-00049] 49. The method of
    claim 48 , wherein the epitaxial stack grown in steps (b) forms FETs of a first type and, after the step (d) of removing upper portions of said first type stack, further comprising:
    growing layered epitaxial stacks of a second type on said semiconductor wafer.
    [50" id="US-20010002715-A1-CLM-00050] 50. The method of
    claim 49 after the step (k) of filling the gate regions, further comprising the steps of:
    k1) exposing sidewalls of said second type stacks and forming a gate insulator layer on said exposed second type stack sidewalls;
    k2) directionally depositing a second gate layer of conductive material by collimated sputtering from a target of said conductive material;
    k3) selectively removing said second gate layer from said gate insulator layer, said second gate layer remaining in gate regions and laterally extending from said gate insulator layer on said second type stack, the side of said second gate layer in each said gate region forming the gate of a second type FET; and
    k4) filling said gate regions above said second type FET gates with an insulating material.
    [51" id="US-20010002715-A1-CLM-00051] 51. The method of
    claim 50 , wherein said second gate layer is thicker than the first said gate layer.
    [52" id="US-20010002715-A1-CLM-00052] 52. The method of
    claim 50 , wherein FETs formed in said wider slots are cell pass gates, said method further comprising the steps of:
    n) forming a wiring strap between each device area in each of said pass gates and a pair of stacks, said pair of stacks being one first type stack and one second type stack; and
    m) forming a strap between each said wiring strap and the gates of a second pair of stacks.
    [53" id="US-20010002715-A1-CLM-00053] 53. The method of
    claim 50 , wherein FETs formed in said wider slots are cell pass gates, said method further comprising the steps of:
    n) forming a wiring strap between each device area in each of said pass gates and a pair of stacks, said pair of stacks being one first type stack and one second type stack; and
    m) forming a high resistance strap between each said wiring strap and the gates of a second pair of stacks, the resistance of said high resistance strap being high than said wiring strap.
    [54" id="US-20010002715-A1-CLM-00054] 54. The method of
    claim 50 , wherein the step (g) of forming the gate insulator comprises the steps of:
    1) forming an oxide layer on said stack sidewall; and
    2) forming a nitride layer on said oxide layer.
    [55" id="US-20010002715-A1-CLM-00055] 55. The method of
    claim 54 , wherein the step (g) of forming the gate insulator further comprises the step of:
    3) depositing an oxide layer on said nitride layer.
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US6750487B2|2002-04-11|2004-06-15|International Business Machines Corporation|Dual double gate transistor|
    JP2008205168A|2007-02-20|2008-09-04|Fujitsu Ltd|Semiconductor device and method of manufacturing the same|
    US7517758B2|2004-09-01|2009-04-14|Micron Technology, Inc.|Method of forming a vertical transistor|
    US20100308422A1|2009-06-05|2010-12-09|Unisantis ElectronicsLtd.|Semiconductor device|
    US20110089496A1|2009-08-11|2011-04-21|Unisantis ElectronicsLtd.|Semiconductor device and production method|
    US8642426B2|2009-03-25|2014-02-04|Unisantis Electronics Singapore Pte Ltd.|Semiconductor device and production method therefor|
    US20160180821A1|2014-12-23|2016-06-23|Intel Corporation|Distributed memory panel|
    US10332833B2|2013-08-08|2019-06-25|Invensas Corporation|Ultra high performance interposer|
    US10468525B1|2018-05-23|2019-11-05|International Business Machines Corporation|VFET CMOS dual epitaxy integration|
    WO2020099962A1|2018-11-16|2020-05-22|International Business Machines Corporation|Microelectronic device utilizing stacked vertical devices|
    US10833089B2|2018-11-16|2020-11-10|International Business Machines Corporation|Buried conductive layer supplying digital circuits|
    US11018235B2|2016-06-13|2021-05-25|Imec Vzw|Vertically stacked semiconductor devices having vertical channel transistors|
    US11164879B2|2018-11-16|2021-11-02|International Business Machines Corporation|Microelectronic device with a memory element utilizing stacked vertical devices|
    US11171142B2|2018-11-16|2021-11-09|International Business Machines Corporation|Integrated circuit with vertical structures on nodes of a grid|US3761782A|1971-05-19|1973-09-25|Signetics Corp|Semiconductor structure, assembly and method|
    US3884733A|1971-08-13|1975-05-20|Texas Instruments Inc|Dielectric isolation process|
    US3986196A|1975-06-30|1976-10-12|Varian Associates|Through-substrate source contact for microwave FET|
    US4462040A|1979-05-07|1984-07-24|International Business Machines Corporation|Single electrode U-MOSFET random access memory|
    US4296428A|1979-06-28|1981-10-20|Rockwell International Corporation|Merged field effect transistor circuit and fabrication process|
    US4466173A|1981-11-23|1984-08-21|General Electric Company|Methods for fabricating vertical channel buried grid field controlled devices including field effect transistors and field controlled thyristors utilizing etch and refill techniques|
    US4507674A|1982-06-07|1985-03-26|Hughes Aircraft Company|Backside illuminated blocked impurity band infrared detector|
    US4554570A|1982-06-24|1985-11-19|Rca Corporation|Vertically integrated IGFET device|
    JPH0527262B2|1984-05-04|1993-04-20|Nippon Electric Co||
    US4692791A|1984-07-13|1987-09-08|Texas Instruments Incorporated|Monolithic IMPATT with stripline leads|
    US4675717A|1984-10-09|1987-06-23|American Telephone And Telegraph Company, At&T Bell Laboratories|Water-scale-integrated assembly|
    US4624004A|1985-07-15|1986-11-18|Eaton Corporation|Buried channel MESFET with backside source contact|
    JPS6252969A|1985-08-30|1987-03-07|Nippon Texas Instr Kk|Insulated gate field effect semiconductor device|
    US4810906A|1985-09-25|1989-03-07|Texas Instruments Inc.|Vertical inverter circuit|
    US4767722A|1986-03-24|1988-08-30|Siliconix Incorporated|Method for making planar vertical channel DMOS structures|
    US4956687A|1986-06-26|1990-09-11|Santa Barbara Research Center|Backside contact blocked impurity band detector|
    JPS63239973A|1986-10-08|1988-10-05|Texas Instruments Inc|Integrated circuit and manufacture of the same|
    US5072276A|1986-10-08|1991-12-10|Texas Instruments Incorporated|Elevated CMOS|
    US4794093A|1987-05-01|1988-12-27|Raytheon Company|Selective backside plating of gaas monolithic microwave integrated circuits|
    US4927784A|1987-05-01|1990-05-22|Raytheon Company|Simultaneous formation of via hole and tube structures for GaAs monolithic microwave integrated circuits|
    US4807022A|1987-05-01|1989-02-21|Raytheon Company|Simultaneous formation of via hole and tub structures for GaAs monolithic microwave integrated circuits|
    US5034347A|1987-10-05|1991-07-23|Menlo Industries|Process for producing an integrated circuit device with substrate via hole and metallized backplane|
    JPH01125858A|1987-11-10|1989-05-18|Fujitsu Ltd|Semiconductor device and manufacture thereof|
    US4982266A|1987-12-23|1991-01-01|Texas Instruments Incorporated|Integrated circuit with metal interconnecting layers above and below active circuitry|
    US4889832A|1987-12-23|1989-12-26|Texas Instruments Incorporated|Method of fabricating an integrated circuit with metal interconnecting layers above and below active circuitry|
    US5032529A|1988-08-24|1991-07-16|Harris Corporation|Trench gate VCMOS method of manufacture|
    US4951102A|1988-08-24|1990-08-21|Harris Corporation|Trench gate VCMOS|
    US5027189A|1990-01-10|1991-06-25|Hughes Aircraft Company|Integrated circuit solder die-attach design and method|
    US5134448A|1990-01-29|1992-07-28|Motorola, Inc.|MOSFET with substrate source contact|
    FR2663784B1|1990-06-26|1997-01-31|Commissariat Energie Atomique|PROCESS FOR PRODUCING A STAGE OF AN INTEGRATED CIRCUIT.|
    US5449930A|1990-08-01|1995-09-12|Zhou; Guo-Gang|High power, compound semiconductor device and fabrication process|
    US5063177A|1990-10-04|1991-11-05|Comsat|Method of packaging microwave semiconductor components and integrated circuits|
    US5057450A|1991-04-01|1991-10-15|International Business Machines Corporation|Method for fabricating silicon-on-insulator structures|
    US5292686A|1991-08-21|1994-03-08|Triquint Semiconductor, Inc.|Method of forming substrate vias in a GaAs wafer|
    JPH05206394A|1992-01-24|1993-08-13|Mitsubishi Electric Corp|Field effect transistor and its manufacture|
    US5252849A|1992-03-02|1993-10-12|Motorola, Inc.|Transistor useful for further vertical integration and method of formation|
    US5208172A|1992-03-02|1993-05-04|Motorola, Inc.|Method for forming a raised vertical transistor|
    US5324673A|1992-11-19|1994-06-28|Motorola, Inc.|Method of formation of vertical transistor|
    US5322816A|1993-01-19|1994-06-21|Hughes Aircraft Company|Method for forming deep conductive feedthroughs|
    US5447871A|1993-03-05|1995-09-05|Goldstein; Edward F.|Electrically conductive interconnection through a body of semiconductor material|
    US5343071A|1993-04-28|1994-08-30|Raytheon Company|Semiconductor structures having dual surface via holes|
    US5455064A|1993-11-12|1995-10-03|Fujitsu Limited|Process for fabricating a substrate with thin film capacitor and insulating plug|
    US5719409A|1996-06-06|1998-02-17|Cree Research, Inc.|Silicon carbide metal-insulator semiconductor field effect transistor|
    DE19839970C2|1998-09-02|2000-11-02|Siemens Ag|Edge structure and drift area for a semiconductor component and method for their production|
    US6392271B1|1999-06-28|2002-05-21|Intel Corporation|Structure and process flow for fabrication of dual gate floating body integrated MOS transistors|US6903411B1|2000-08-25|2005-06-07|Agere Systems Inc.|Architecture for circuit connection of a vertical transistor|
    US6649476B2|2001-02-15|2003-11-18|Micron Technology, Inc.|Monotonic dynamic-static pseudo-NMOS logic circuit and method of forming a logic gate array|
    US6690040B2|2001-09-10|2004-02-10|Agere Systems Inc.|Vertical replacement-gate junction field-effect transistor|
    US6759730B2|2001-09-18|2004-07-06|Agere Systems Inc.|Bipolar junction transistor compatible with vertical replacement gate transistor|
    US20030052365A1|2001-09-18|2003-03-20|Samir Chaudhry|Structure and fabrication method for capacitors integratible with vertical replacement gate transistors|
    US6686604B2|2001-09-21|2004-02-03|Agere Systems Inc.|Multiple operating voltage vertical replacement-gatetransistor|
    US6709904B2|2001-09-28|2004-03-23|Agere Systems Inc.|Vertical replacement-gate silicon-on-insulator transistor|
    US6773994B2|2001-12-26|2004-08-10|Agere Systems Inc.|CMOS vertical replacement gatetransistors|
    US7045844B2|2002-06-21|2006-05-16|Micron Technology, Inc.|Memory cell and method for forming the same|
    US6756625B2|2002-06-21|2004-06-29|Micron Technology, Inc.|Memory cell and method for forming the same|
    US20070034909A1|2003-09-22|2007-02-15|James Stasiak|Nanometer-scale semiconductor devices and method of making|
    US6762094B2|2002-09-27|2004-07-13|Hewlett-Packard Development Company, L.P.|Nanometer-scale semiconductor devices and method of making|
    US6759699B1|2003-04-22|2004-07-06|Taiwan Semiconductor Manufacturing Company|Storage element and SRAM cell structures using vertical FETS controlled by adjacent junction bias through shallow trench isolation|
    US6992354B2|2003-06-25|2006-01-31|International Business Machines Corporation|FinFET having suppressed parasitic device characteristics|
    US6909125B2|2003-07-08|2005-06-21|Texas Instruments Incorporated|Implant-controlled-channel vertical JFET|
    US7262099B2|2004-08-23|2007-08-28|Micron Technology, Inc.|Methods of forming field effect transistors|
    US7132355B2|2004-09-01|2006-11-07|Micron Technology, Inc.|Method of forming a layer comprising epitaxial silicon and a field effect transistor|
    US7531395B2|2004-09-01|2009-05-12|Micron Technology, Inc.|Methods of forming a layer comprising epitaxial silicon, and methods of forming field effect transistors|
    US8673706B2|2004-09-01|2014-03-18|Micron Technology, Inc.|Methods of forming layers comprising epitaxial silicon|
    KR100702011B1|2005-03-16|2007-03-30|삼성전자주식회사|CMOS SRAM cells employing multiple gate transistors and methods fabricating the same|
    US7372092B2|2005-05-05|2008-05-13|Micron Technology, Inc.|Memory cell, device, and system|
    US7462534B2|2005-08-02|2008-12-09|Micron Technology, Inc.|Methods of forming memory circuitry|
    US7504277B2|2005-10-12|2009-03-17|Raytheon Company|Method for fabricating a high performance PIN focal plane structure using three handle wafers|
    US7941309B2|2005-11-02|2011-05-10|Microsoft Corporation|Modeling IT operations/policies|
    US7709341B2|2006-06-02|2010-05-04|Micron Technology, Inc.|Methods of shaping vertical single crystal silicon walls and resulting structures|
    US7625776B2|2006-06-02|2009-12-01|Micron Technology, Inc.|Methods of fabricating intermediate semiconductor structures by selectively etching pockets of implanted silicon|
    US7628932B2|2006-06-02|2009-12-08|Micron Technology, Inc.|Wet etch suitable for creating square cuts in si|
    TWI305669B|2006-07-14|2009-01-21|Nanya Technology Corp|Method for making a raised vertical channel transistor device|
    US8735990B2|2007-02-28|2014-05-27|International Business Machines Corporation|Radiation hardened FinFET|
    US7772668B2|2007-12-26|2010-08-10|Fairchild Semiconductor Corporation|Shielded gate trench FET with multiple channels|
    JP5623005B2|2008-02-01|2014-11-12|ピーエスフォー ルクスコ エスエイアールエルＰＳ４ Ｌｕｘｃｏ Ｓ．ａ．ｒ．ｌ．|Semiconductor device and manufacturing method thereof|
    US7755107B2|2008-09-24|2010-07-13|Skyworks Solutions, Inc.|Bipolar/dual FET structure including enhancement and depletion mode FETs with isolated channels|
    US9230810B2|2009-09-03|2016-01-05|Vishay-Siliconix|System and method for substrate wafer back side and edge cross section seals|
    JP5623068B2|2009-12-07|2014-11-12|キヤノン株式会社|Method for manufacturing solid-state imaging device|
    US8283715B2|2010-08-12|2012-10-09|Rexchip Electronics Corporation|Method and apparatus for buried word line formation|
    FR2989218A1|2012-04-10|2013-10-11|St Microelectronics Sa|METHOD FOR PRODUCING AN ELECTRONIC DEVICE BY ASSEMBLING SEMICONDUCTOR BLOCKS AND DEVICE THEREOF|
    KR20150054885A|2012-09-07|2015-05-20|유니버시티 오브 버지니아 페이턴트 파운데이션|Low power clock source|
    KR101695708B1|2014-01-09|2017-01-13|한국전자통신연구원|Semiconductor device and method of fabricating the same|
    US9646973B2|2015-03-27|2017-05-09|Taiwan Semiconductor Manufacturing Company, Ltd.|Dual-port SRAM cell structure with vertical devices|
    US9472558B1|2015-11-13|2016-10-18|Globalfoundries Inc.|Semiconductor structures with stacked non-planar field effect transistors and methods of forming the structures|
    US9799655B1|2016-04-25|2017-10-24|International Business Machines Corporation|Flipped vertical field-effect-transistor|
    US10453844B2|2017-12-06|2019-10-22|International Business Machines Corporation|Techniques for enhancing vertical gate-all-around FET performance|
    US10439045B1|2018-05-09|2019-10-08|International Business Machines Corporation|Flipped VFET with self-aligned junctions and controlled gate length|
    US10388569B1|2018-06-26|2019-08-20|International Business Machines Corporation|Formation of stacked nanosheet semiconductor devices|
    US10483166B1|2018-06-26|2019-11-19|International Business Machines Corporation|Vertically stacked transistors|
    US10741456B2|2018-10-10|2020-08-11|International Business Machines Corporation|Vertically stacked nanosheet CMOS transistor|
    法律状态:
    1998-01-05| AS| Assignment|Owner name: INTERNATIONAL BUSINESS MACHINES CORPORATION, NEW Y Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ARMACOST, MICHAEL D.;BERTIN, CLAUDE L.;HEDBERG, ERIK L.;AND OTHERS;REEL/FRAME:008923/0670;SIGNING DATES FROM 19971024 TO 19971103 |
    2005-01-24| FPAY| Fee payment|Year of fee payment: 4 |
    2009-04-13| REMI| Maintenance fee reminder mailed|
    2009-10-02| LAPS| Lapse for failure to pay maintenance fees|
    2009-11-02| STCH| Information on status: patent discontinuation|Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
    2009-11-24| FP| Expired due to failure to pay maintenance fee|Effective date: 20091002 |
    优先权:
    申请号 | 申请日 | 专利标题
    US09/002,399|US6297531B2|1998-01-05|1998-01-05|High performance, low power vertical integrated CMOS devices|US09/002,399| US6297531B2|1998-01-05|1998-01-05|High performance, low power vertical integrated CMOS devices|
    US09/899,262| US6518112B2|1998-01-05|2001-07-06|High performance, low power vertical integrated CMOS devices|
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