奥地利专利AT517792A2 Clamping device for sucking and holding a wafer

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专利摘要:
The invention relates to a jig and method for aspirating and holding a wafer by said jig, the jig comprising: a planar upper surface divided into a plurality of suction segments, the suction segments each being adapted to exhaust a fluid; and a lower surface. The method includes the steps of: approximating wafer and top surface of the chuck within a fluid such that two or more of the suction segments are covered, at least loosely covered, by the wafer; Selecting a suction segment having a minimum distance to the wafer from the not yet activated suction segments; Activating the aspiration segment selected in the previous step; after the wafer in the region of the last-activated suction segment rests tightly on the upper surface of the jig and as long as at least one suction segment is not yet activated: repeating the preceding steps.
公开号:AT517792A2
申请号:T9476/2013
申请日:2013-09-26
公开日:2017-04-15
发明作者:Conradi Matthias；Hansen Sven
申请人:Suss Microtec Lithography Gmbh；
IPC主号:

专利说明:

Clamping device for sucking and holding a wafer
The present invention relates to a jig for sucking and holding a wafer, and to a method of sucking and holding a wafer by this jig. More particularly, the present invention relates to a jig with various suction segments, each suction segment being separately activatable, and to a method of using this jig, wherein a suction segment having a minimum distance from the wafer is selected for the sequence of activation of the suction segments.
Chucks (also known as "chuck") are chuck plates for fixing a substrate or wafer while the wafer is being processed in the course of manufacturing an integrated circuit (IC) or similar micro device. Wafers typically have the shape of a disk. Often, for example, when the thickness of a wafer is relatively low, but also for other reasons such as the manufacturing process of the wafer, the wafer either is not inherently designed as a completely planar disk and / or the wafer is while fixing on the chuck buckles or folds. In addition, the wafer can then warp or deform.
For sucking arched and / or warped wafers seals have been used. These seals may be located at the edge of the wafer / chuck as well as at different positions of the chuck's platen (suction cups). As a result, the seals can be assigned to different vacuum circuits. These vacuum circuits (chuck / suction cup) can be switched or activated simultaneously or one after the other.
WO 2006/072453 describes an end effector (chuck) with at least two vacuum circuits. Such an arrangement can be used for sucking warped wafers, particularly thin and ultra-thin wafers. According to WO 2006/072453, the end effectors are constructed as plates made of a porous material, in particular porous sintered materials.
However, the suction by means of seals or lip seals has disadvantages. For example, it may be that the gaskets or lip seals are not heat resistant / temperature resistant and / or have poor solvent resistance. In addition, the seals or
Lip seals produce particles. Due to the inherent coarseness of the surface of a porous, e.g. As sintered, material cleaning of such end effectors is often difficult, which can also reduce the life of the end effector. In addition, the coarse surface structure of the end effector can unduly affect the surface texture of the wafer as the end effector wafer is pressed against the surface of the end effector. In addition, both vacuum circuits of the end effector described in WO 2006/072453 are pneumatically separated from one another.
As a result, a separate vacuum port must be provided for each of the vacuum circuits. For example, if eight vacuum circuits are used, vacuum generation must be managed by eight corresponding vacuum ports, which could be difficult.
It is an object of the present invention to provide a chuck and a method of using this chuck that allow a wafer to be suctioned so as to avoid distortions, cambers, creases, kinks and / or lopses when the wafer is held by the chuck , Another object of the invention is to overcome the above-described disadvantages of using seals and / or sealing lips and / or the use of an end effector with porous, e.g. B. sintered to avoid surface.
These objects are achieved by the jig and the method having the features according to the present claims.
For sucking a skewed / deformed wafer, it is expedient first to suck the wafer at those points (partial sections) where one of the several suction segments of the chuck sits closest to the wafer or corresponding wafer section. In other words, as far as the chuck is divided into different vacuum areas or suction segments, the wafer must first be sucked into positions with the least loss of pressure. These positions are usually areas where the wafer covers the corresponding suction segment as completely as possible.
These suction segments may have a very smooth surface, for. B. with a flatness of 0.002 mm or better, and thus allow a simplified cleaning, a longer shelf life and improved contact with the applied wafer.
If the skew / deformation of the wafer is due to the previous manufacturing process of the wafer, e.g. For example, if the wafers to be held are convex, the selection of the suction segments and / or the shape of the suction segments can be made so that a maximum volume flow is provided at positions where the wafer rests on the chuck.
Throughout the following text, the term "applying vacuum" refers to the process of aspirating fluid from a particular area. For example, applying vacuum to a suction segment means that fluid, e.g. As air or liquid, is sucked in the region of the Ansaugsegmente from the area above the upper surface (bearing surface) of the chuck. This corresponds to the application of a negative pressure to the corresponding surface area.
Since "suppression" means that the pressure is lower than a reference pressure, e.g. For example, as the pressure of the fluid in the vicinity of the chuck, the assigned value is negative (eg, -1 bar). For the sake of clarity, it should be noted that in the following text reference is always made to the absolute value of the negative pressure, which then in each case appears as a positive value (eg | -11 bar = 1 bar), and also comparative expressions ("higher", " greater "," less than ", etc.) refer to the absolute values. For example, the formulation that a first depression is "higher" than a second depression means that the absolute value of the first negative pressure is greater than the absolute value of the second negative pressure.
Further, the term "fluid" is used as a generic term for both gases (such as air) and liquids.
The term "main vacuum" refers to a squeeze that is strong enough to suck and hold the wafer against the chuck's bearing surface.
The term "auxiliary vacuum" refers to a vacuum that is weaker than a main vacuum, wherein the auxiliary vacuum is only used to measure the spacing of certain portions of the wafer to the chuck contact surface, and wherein the auxiliary vacuum is not for aspirating the wafer to the support surface of the chuck or to the respective suction of the chuck is suitable.
The term "activate a suction segment" means that the main vacuum is applied to the corresponding suction segment (see definition of "applying a vacuum" above). In particular, the term "activating" refers to the application of a vacuum in such a way that a wafer can be sucked in by the effected volumetric flow of a fluid. That is, fluid flows caused by an "auxiliary vacuum" do not "activate" a suction segment, since an auxiliary vacuum is for metering purposes only and is typically not strong enough to aspirate the wafer. Different definitions are equally possible for the term "distance" between wafer and suction segment. For example, the standard mathematical definition of the distance between two objects may be used: then the distance is given by the minimum of the set of all distances between any two points where one of the points belongs geometrically to the wafer and the other point belongs to the chuck's suction segment. Another definition that can equally be used here is as follows, provided that the surface of the suction segment (opposite to the wafer) is designed geometrically as a plane: the amount of the individual distances between one point of the surface of the suction segment and one point is considered the surface of the wafer, wherein the respective two points lie on a straight line which is perpendicular to the surface of the suction segment. Then, the distance between the wafer and the suction segment can be defined as the mean of all elements of the set, e.g. B. as an arithmetic mean of the amount. (It should be noted that this definition applies even if the wafer does not completely cover the suction segment.) Of course, any other suitable definition of the distance between the wafer and the suction segment may equally be used. Throughout the following text, it can be assumed that the distance between the wafer and the suction segment can be determined at least approximately by measuring the negative pressure (auxiliary vacuum) of the fluid arranged between a suction segment and the wafer.
One aspect of the invention relates to a chuck for sucking and holding a wafer, which comprises a planar upper surface which is subdivided into a plurality of suction segments, wherein the suction segments are each designed for sucking off a fluid; and a bottom surface, wherein the top surface is adapted to be approximated within a fluid to a wafer such that two or more of the suction segments are covered by the wafer, at least loosely covered; and the suction segments are each separately activated.
The phrase that a suction segment is "covered" by the wafer here and in the following means that the wafer (or a part thereof) is in an area on the side of the upper surface of the suction segment where the wafer (or a part thereof ) is attracted by the suction segment when the suction segment is activated. The
Thus, formulation does not necessarily mean that the wafer (or a corresponding portion thereof) contacts the suction segment. However, when the wafer (or a corresponding part thereof) contacts the suction segment, the suction segment is covered by the wafer.
The term "loosely covered" means that a particular suction segment is "covered" by the wafer, but the wafer does not touch the top surface of the suction segment.
The phrase "approaching the top surface of the chuck to the wafer" refers to all movements of the top surface relative to the wafer through which two or more suction segments are covered, or at least loosely covered, by the wafer. In principle, during the approach, any position and / or orientation of the wafer with respect to the upper-side bearing surface of the chuck can be selected. However, it is preferred that the support surface of the chuck approach the wafer so that, for most points on the wafer, the respective tangent vectors are reduced only by a small amount, e.g. B. less than 30 degrees, deviate from a parallel orientation to the upper surface of the chuck.
Preferably, the top surface refers to the surface of a solid material such as a metal or alloys of different metals or a polymer. In particular, this solid material can not on a porous material such. As a sintered material relate.
The chuck may further comprise: means, preferably a throttle, configured to apply an auxiliary vacuum to the individual suction segments; means preferably comprising at least one pressure sensing means or at least one flow rate detecting means and arranged to measure, at each of the suction segments, the depression or flow rate of the volume flow of fluid aspirated from the respective suction segment upon appropriate application of a vacuum; and a means, preferably a mechanical and / or electrical means associated with each of the means for measuring the negative pressure or the flow rate and designed to determine at which of the suction segments of auxiliary vacuum systems a maximum absolute value of the negative pressure or a minimum flow rate of the fluid is measured.
Here, the electrical means z. As an electronic circuit or an integrated circuit (IC) and a microcontroller, a computer, etc. be.
In a preferred embodiment of the chuck, the upper surface of the chuck is a disc; an inner suction segment is disposed around the center of the upper surface; further suction segments are arranged as rings around the inner suction segment; and wherein the individual suction segments are preferably separated from the other suction segments, respectively.
In one embodiment of the chuck, each of the suction segments includes a system of interconnected grooves disposed on the upper surface of the chuck, and preferably each system of interconnected grooves includes one or more grooves formed as concentric circles about the midpoint of the upper one Surface are designed.
In one embodiment of the chuck, the plurality of suction segments are disposed on the top surface such that on the top surface a virtual spiral path extends from a point within one of the suction segments and circumferentially to the edge of the top surface, the path of each of the suction segments being only enters and / or leaves once.
In a preferred embodiment of the chuck, each suction segment is connected to a main vacuum distribution means disposed on the lower surface of the chuck and adapted to apply a vacuum to each individual suction segment; and the application of a vacuum to the individual suction segments, possibly with the exception of a suction segment, can be controlled via a valve.
In one embodiment of the chuck, the means for applying the main vacuum comprises a main vacuum channel having an inlet designed for the application of vacuum (the main vacuum applied via this inlet may also be referred to hereinafter as the "first support vacuum"); each of the suction segments is connected to the main vacuum channel via a side channel having an orifice to the main vacuum channel; in the main vacuum channel, a respective valve is arranged between two adjacent orifices, so that the main vacuum channel has a plurality of sections which are separated by these valves; and the side channels are arranged so that two juxtaposed portions of the main vacuum channel are respectively connected to adjacent suction segments.
In a preferred embodiment of the chuck, each of these valves is a check valve, such as a ball check valve, a diaphragm check valve, a flapper check valve, a tilting disk check valve, a check check valve
Piston check valve, a sleeve check valve or a lip check valve; each of the check valves is designed to automatically open when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum channel is equal to or greater than a predetermined value; and each of the check valves is preferably configured to open only when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum channel is a value corresponding to a state in which the wafer is tight abuts the suction segment, which is connected to the adjacent to the direction of the channel inlet to the check valve portion.
Another aspect of the invention relates to a method for sucking and holding a wafer by a chuck, the chuck comprising: a planar upper surface divided into a plurality of suction segments, each of the suction segments being adapted to exhaust a fluid; and a lower surface. The method comprises the following steps: (9a) approximating the wafer and upper surface of the chuck within a fluid such that two or more of the suction segments are covered, at least loosely covered, by the wafer; (9b) selecting a suction segment having a minimum distance to the wafer from the not yet activated suction segments; (9c) activating the aspiration segment selected in step (9b); (9d) after the wafer in the region of the last activated suction segment is in close contact with the upper surface of the chuck and as long as at least one suction segment has not yet been activated:
Repeat steps (9b) to (9d).
To step (9b): If a plurality of suction segments have a minimum distance to the wafer, "selecting" includes a decision as to which one of the plurality of suction segments having a minimum distance to the wafer is selected. For example, this algorithm may include a decision step such that of a plurality of suction segments having a minimum distance to the wafer, the one closest to the center of the upper surface of the chuck is selected. Alternatively, the algorithm may include a step of randomly selecting one of the suction segments having a minimum distance to the wafer.
In a preferred embodiment of the method, step (9b) of selecting a suction segment having a minimum distance to the wafer comprises the steps of: (10a) measuring the distance from each of the suction segments to the surface of the wafer opposite the respective suction segment; (10b) determining a suction segment, which has a minimum distance to the wafer, from the not yet activated suction segments.
In one embodiment of the method, the step (10a) of the distance measurement comprises the following steps: (11a) applying an auxiliary vacuum to the not yet activated intake segments, preferably via a throttle; (llb) for each of the suction elements to which the auxiliary vacuum has been applied in step (11a): measuring the negative pressure or the flow rate of the volume flow of the extracted fluid, preferably via a pressure detecting means or a flow amount detecting means; and
Step (10b) of determining a minimum distance comprises the following step: (llc) determining at which of the suction elements to which the auxiliary vacuum has been applied a maximum absolute value of the negative pressure or a minimum flow rate of the fluid is measured, preferably via a mechanical and or electrical means connected to each of the pressure sensing means or each of the flow rate detection means.
Here, the electrical means z. As an electronic circuit or an integrated circuit (IC) and a microcontroller, a computer, etc. be.
In an alternative embodiment of the method, the sequence of the suction segments selected in step (9b) is predefined according to a known shape of the wafer.
In a preferred embodiment of the method, the upper surface of the chuck is a disc; an inner suction segment is disposed around the center of the upper surface; further suction segments are arranged as rings around the inner suction segment. Preferably, the individual Ansaugsegmente are each separated from the other Ansaugsegmenten.
In one embodiment of the method, each of the suction segments comprises a system of interconnected grooves disposed on the upper surface of the chuck. Preferably, each system of interconnected grooves includes one or more grooves configured as concentric circles about the center of the top surface.
In one embodiment of the method, the plurality of suction segments are disposed on the top surface such that at the top surface a virtual spiral path extends from a point within one of the suction segments and circumferentially to the top surface edge, the path of each of the suction segments being only enters and / or leaves once; and the sequence of the aspiration segments selected in step (9b) follows the virtual spiral path, the first aspiration segment being the aspiration segment with the origin of the virtual spiral path.
Preferably, each suction segment is connected to a main vacuum distribution means disposed on the lower surface of the chuck and adapted to apply vacuum to each individual suction segment; and the application of vacuum to the individual suction segments, possibly with the exception of a suction segment, can be controlled via a valve. Then, the method may include the steps of: (16a) applying a vacuum to the main vacuum distribution means, which step is started before or together with step (9c) and performed as long as the wafer is to be kept away from the chuck; and wherein step (9c) of activating a suction segment comprises the step of: (16b) if the suction segment is controllable via a valve: opening the valve designed to control the corresponding suction segment, otherwise: starting step (16a).
In one embodiment of the method, the means for applying the main vacuum comprises a main vacuum channel having an input designed to apply a vacuum; each of the suction segments is connected to the main vacuum channel via a side channel having an orifice to the main vacuum channel; between two adjacent orifices, a respective valve is arranged in the main vacuum channel, so that the main vacuum channel has a plurality of sections which are separated by these valves; the side channels are arranged so that two adjacent sections of the main vacuum channel each with adjacent
Suction segments are connected; and step (9b) of selecting a suction segment comprises: if step (9b) is performed for the first time during the performance of the method: selecting the suction segment connected to the portion of the main vacuum adjacent to the inlet; otherwise: selecting the suction segment connected to that portion of the main channel adjacent to the portion connected to the suction segment previously selected in step (9b).
Preferably, each of these valves is a check valve, for example, a ball check valve, a diaphragm check valve, a flapper check valve, a tilting disc check valve, a check check valve, a piston check valve, a sleeve check valve or a lip check valve; wherein each of the check valves is adapted to automatically open when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum channel is equal to or greater than a predetermined value; and wherein each of the check valves is preferably configured to open only when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum passage is a value corresponding to a state in which the wafer is sealed abuts the suction segment which is connected to the adjacent to the direction of the channel entrance to the check valve portion.
In a preferred embodiment, the method further comprises the following further step: (19a) when the wafer is completely held by the chuck: applying an additional vacuum (also referred to as "second apply vacuum") to the main vacuum channel from the opposite side of the inlet.
Other aspects, features, and advantages will be apparent from the foregoing summary, as well as from the following description, including the figures and claims.
Fig. 1: Chuck with vacuum manifold
Fig. 2: Functional principle
Fig. 3: Procedure for the sequential activation of Ansaugsegmenten and thereby generating a maximum volume flow rate for applying a sufficiently strong pressure to the wafer
Fig. 4: Illustration of the pressure drop across different suction segments
Fig. 5: Avoiding a pressure drop by applying an additional vacuum
Fig. 6: Illustration of the caused by an additional vacuum constant pressure
Fig. 7: Sketch of a circuit for measuring the distance between the wafer and the suction segments
Fig. 8: Possible subdivision of a bearing surface of a chuck in several suction segments
9: Image of an embodiment of the chuck (upper surface)
10: Image of an embodiment of the chuck (lower area with main vacuum channel and non-return valves)
Cascade connection with check valves
In order to achieve the highest possible volume flow in the individual intake segments, these intake segments can each be separated by check valves, for example ball check valves. In one embodiment of the chuck according to the invention, the chuck comprises a main vacuum channel having an input designed to apply a vacuum (negative pressure). The main vacuum channel is then subdivided into a plurality of subsections, wherein a check valve is installed in each case between two adjacent subsections. For example, typically N-1 check valves are required to divide the main vacuum channel into N sections. Each of the sections is then connected to one of the suction segments via a side channel. This arrangement is referred to as "cascade connection" throughout this document.
In the following, the numbering of the check valves and the sections of the main channel - for simplicity and clarity - respectively corresponds to the position relative to the channel entrance: the first section of the main vacuum channel is connected directly to the input without an interposed check valve. Then, the first check valve separates the first section from the second section of the main vacuum channel. The second section is then separated via the second check valve from the third section, etc.
The numbering of a particular suction segment also corresponds to the numbering of the subsection to which the suction segment is connected via the side channel.
In order to suck in a wafer via the chuck, a vacuum is applied to the cascade circuit via the input. Since the first check valve is still closed, the "full" fluid flow (eg, air flow) from the first aspiration segment enters via the corresponding side channel and the first subsection of the main vacuum channel to the vacuum supply connected to the input The wafer finally closes off the first suction segment in the direction of the chuck, ie it is completely sucked in the area of the first suction segment.
Ideally, the (first) check valve opens only when the wafer is completely sucked in the first suction segment. Subsequently, the "complete" volume flow is applied to the second intake segment. Only when the wafer is completely fixed on the second suction segment and this completely seals, then the next suction segment is activated by opening the next check valve. This procedure is repeated (automatically) until the last check valve is open and the "complete" volume flow is applied to the last suction segment. In the end, the wafer is sucked and held by each of the suction segments (provided that the wafer is large enough to cover each of the suction segments).
Since each check valve causes a pressure loss, it is possible that the vacuum (negative pressure, measured as absolute value of the negative pressure) in the last suction segment is relatively low compared to the vacuum (negative pressure) of the first suction segment. For compensation, an additional vacuum can be applied to the last suction segment after the wafer has been completely sucked in and held by the chuck.
Activation sequence of the suction segments
As already discussed above, the wafer is conveniently sucked first in the region of the aspiration segment that is covered most closely by the wafer (or by a portion thereof). In one embodiment of the chuck according to the invention, an auxiliary vacuum is used to determine this area.
For example, the following arrangement can be considered. A main vacuum duct, having an inlet designed to apply a vacuum to the duct, splits into a plurality of branches, each of which branches to one on an upper surface of the duct
Chuck arranged suction segment is connected. Each of the branches comprises a switch (valve) designed to switch on and off the connection of the corresponding suction segment to the main vacuum channel. Thus, each of the suction segments can be independently activated / deactivated by turning on or off the switch at the corresponding branch, thereby applying or not applying a vacuum (negative pressure) to the suction segment from the main vacuum channel. Further, each of the suction segments is connected to a channel system which is adapted to apply an auxiliary vacuum to the suction segments. For example, the auxiliary vacuum channel system is connected to the main vacuum channel and includes a throttle.
By means of the throttle, the volume flow of the auxiliary vacuum is then reduced in relation to the volume flow (eg air flow) caused by the main vacuum. The auxiliary vacuum is connected to the multiple suction segments via check valves and pressure gauges. That is, the more a suction segment is covered by a wafer, the more the pressure (or in other words, the greater the absolute value of the negative pressure) on this suction segment decreases. At the suction segment, where the wafer is closest to the wafer in comparison with the other suction segments, the negative pressure has a maximum (in absolute value).
After determining the suction segment most closely covered by the wafer, the corresponding check valve is activated and the wafer is partially sucked in this area until the wafer seals the corresponding suction segment.
The respective (sub) pressure of the auxiliary vacuum is then measured for each of the remaining intake segments and the intake segment is again determined with the (in absolute value) maximum negative pressure. This suction segment is activated by opening the corresponding switch to apply vacuum to the suction segment from the main vacuum channel. The wafer is then aspirated in the region of this aspiration segment and the procedure repeated until each of the aspiration segments is activated and the wafer is fully aspirated.
Spiralansaugung
If wafers, z. B. due to previous production processes, repeatedly have the same or similar deformations, the shape of the Ansaugsegmente and / or the sequence of applying the vacuum in the chuck can be adapted to this deformation.
In the case of concave wafers, it may be expedient, for example, to aspirate a wafer, starting from the inner region of the contact surface of the chuck, to the outer edges of the contact surface.
This can be accomplished by a high volume vacuum channel located below an upper surface of the chuck and spiraling from a center point to the edge of the upper surface of the chuck. In addition, vacuum grooves are arranged on the upper surface of the chuck. The vacuum grooves or different systems (groups) of vacuum grooves are separated. In addition, the chuck can be subdivided into different intake areas or intake segments. This is necessary for sucking heavily deformed / warped wafers.
Combination of cascade connection and spiral suction
The spiral suction can be combined with the cascade connection described above. This allows a reduction in the number of vacuum check valves. For example, it is possible to suck heavily warped wafers with only two check valves instead of three or more check valves.
This may be particularly advantageous, for example, to save check valves for economic reasons and / or because the Chuck controlling software on any configuration, d. H. an alignment of channels, check valves, etc., this chuck needs to be adjusted.
FIG. 1 shows two parts of an embodiment of the chuck according to the invention. The upper surface 10 of the chuck is formed as a disc. On the disc several grooves are arranged. Circular grooves 11 are arranged around the center of the upper surface of the chuck so as to form a system of concentric circles. In addition, grooves are arranged in the radial direction (relative to the center of the upper surface 10) on the upper surface 10 of the chuck. For example, radially directed grooves 12a, 12b, 12c and 12d extend in a star shape from the center of the upper surface 10 to the third circular groove (counting direction from the center to the edge). With this, the radial grooves 12a to 12d connect the system of the three inner circular grooves. Likewise, the fourth to seventh circular grooves are connected to each other via radially directed grooves, but these grooves are not connected to the system of the three inner circular grooves and radial grooves 12a to 12d. The eighth to eleventh grooves are connected to each other via radial grooves. Finally, the twelfth to fifteenth grooves are interconnected via radially aligned grooves. In this way, there are four independent (i.e., unconnected) groove systems located on the upper surface of the chuck. Each of these systems can be considered as an independently activatable suction segment.
Figure 1 also shows a housing 16 comprising a cascade circuit. Housing 16 includes an inlet 18 adapted for connection to a main vacuum supply, and four outlets 17a, 17b, 17c, and 17d, each of these outlets for connection to one of the groove systems described above disposed on the upper surface of the chuck is designed.
Figure 2 shows a section through the upper surface of the chuck and a section through the housing 16 of Figure 1. The housing 216 includes a skin vacuum channel 250 through which the fluid can be passed. The fluid can be withdrawn via the inlet 218 from this channel 250. Within the channel 250, three check valves 220a, 220b and 220c are provided. The three check valves 220a, 220b and 220c divide the channel 250 into four sections. Each of the sections is connected via a side channel to one of the outputs 217a to 217d. Another input 219 is provided on the opposite side of the channel 250 to the input 218. The further input 219 allows additional application of an additional vacuum to the main vacuum channel 250.
Taken in Figure 2, a section through an exemplary check valve 200 is shown. The check valve 200 includes a housing 201. Within the housing 201, a piston or plunger 202 is arranged, which is held by a coil spring 203 in position to keep the check valve 200 closed. However, when the pressure on the opposite side of the piston 202 from the coil spring 203 is greater than the pressure exerted on the piston 202 by the spring 203, the check valve 200 opens and the fluid can pass through the check valve 200.
At the top surface 210 of the chuck, four systems 211, 212, 213, 214 of grooves are arranged. These groove systems can be independently activated by applying vacuum via inputs 221, 222, 223, and 224. Each of these inputs 221 to 224 is connected to one of the groove groups via a side channel. For example, the entrance 221 is connected via side channel 230 to the groove system 211, which includes the three innermost circular grooves. The innermost groove system forming a first suction segment of the chuck may then be connected via the input 221 and the output 217a to that portion of the channel 250 of the cascade circuit which is closest to the input 218. The second groove system 212 (counted from the center of the upper surface 210 towards the edge) may also be connected via the inlet 222 and the outlet 217b to that portion of the channel 250 that is separated from the inlet 218 by only one check valve 220a. The third groove system 213 may equally be connected to the third subsection of the channel 250 and, finally, the outer (fourth) groove system 214 may be connected via the input 224 and the exit 217d to a subsection of the channel 250 which is above all the check valves from the entrance 218 is disconnected.
By virtue of this structure, when a vacuum is applied via the inlet 218, a check valve would not be opened as long as fluid is sucked out of the inner suction segment 211. However, if a wafer (not shown) is tightly attached to the inner suction segment 211, the first check valve 220a would open as long as the second suction segment 212 is not sealed by a portion of the wafer, thereby establishing a volume flow on the second suction segment 212. However, the second check valve 220b is still in a closed state. Then, the "full" vacuum is applied to the second suction segment 212 and exerts the strongest (under) pressure on the wafer in the region of the second suction segment 212. Only after the wafer (or a portion of the wafer) tightly seals the second suction segment 212 does the second check valve 220b open and the complete main vacuum is applied to the third suction segment 213. After the third suction segment 213 is tightly covered by a portion of the wafer, the third check valve 220c opens, and then the complete vacuum is applied to the outermost suction segment 214 of the top surface 210 of the chuck. In this way, a wafer starting from the inside of the top surface 210 of the chuck to the outside can be easily sucked.
Finally, if the wafer is in each case completely held by the suction segments, an additional vacuum is applied starting from the further inlet 219 of the cascade circuit in order to apply sufficient negative pressure to each of the suction segments and thus fix the wafer in a stable manner.
This procedure is further illustrated by FIG. First, a wafer 36 having the shape 36a is located on the upper surface 39 of the chuck, i. H. the wafer 36 contacts the upper surface 39 only in the area around the center of the upper surface 39. Then, a main vacuum 30 is applied to the cascade circuit 38. First, a vacuum 31 a is applied to the suction segment 32 a around the center of the upper surface 39. Accordingly, the wafer 36 is firmly sucked in the region of the suction segment 32a, so that no fluid can be sucked off within this range. The wafer is then in a state of shape 36b. As a result, the check valve 33a opens, and it becomes a
Vacuum 31b applied to the second suction segment 32b. Fluid is then drawn off in the region of the suction segment 32b, and the wafer is pulled toward the second suction segment 32b until the wafer covers and tightly seals the suction segment 32b. The wafer is then in a state of the mold 36c. Thereafter, the procedure is repeated by opening check valve 33b and sucking the wafer in the region of suction segment 32c and finally by opening check valve 33c and sucking the wafer in the region of suction segment 32d. Thereafter, the wafer is completely sucked by check valve and in a flat state 36d.
However, each check valve causes a drop in the (absolute) value of the (sub-pressure in the vacuum channel 41. FIG. 4 shows a situation where a wafer 45 is completely sucked by the chuck so that all the suction segments 42a, 42b, 42c and 42d from the wafer At the first suction segment 42a, which is directly connected to the main vacuum supply, there is then a negative pressure of minus 1 bar, but at the second suction segment 42b, which is connected to the main vacuum via the first non-return valve 40a, there is a reduced ( At the third suction segment 42c, the negative pressure (in absolute value) has dropped even further and is at -0.5 bar, which is due to the fact that the third suction segment 42c Finally, the absolute value of the negative pressure is at the last (outer) suction segment 42d, which exceeds three R check valves 40a to 40c is connected to main vacuum supply, only at Ά from the corresponding value of the inner Ansaugsegments 42a, d. H. the negative pressure at the suction segment 42d is -0.25 bar. As a result, the pressure at which the wafer 45 is held on the top surface of the chuck is not constant across the top surface but decreases from the center to the edge of the chuck. Accordingly, the wafer 45 may be more unstably fixed in the outer regions of the chuck support surface (suction segment 42d) than in the inner regions of the support surface (suction segment 42a).
In order to stabilize the wafer 55 on the upper surface of the chuck 56, an additional vacuum 52, 53 may be applied to the cascade circuit. FIG. 5 again shows a situation where the wafer 55 has already been completely sucked in by the chuck and firmly seals all the suction segments of the upper surface 56. A main vacuum 50 is applied to the cascade circuit and distributed via the vacuums 51a, 51b, 51c and 51d to the individual suction segments 57a, 57b, 57c and 57d. As explained with reference to FIG. 4, the strongest vacuum 51 a is applied to the inner suction segment 57 a. To the edge of the upper
Face 56 of the chuck decreases the vacuum applied to the suction segments 57b to 57d. To compensate for this effect, an additional vacuum can be applied. For example, an additional vacuum 52 may be applied to the cascade circuit from the side opposite the main vacuum supply 50. Then, the outer suction segment 57d is directly (i.e., not via a check valve) connected to the auxiliary vacuum 52, the thickness of which may be selected to provide sufficient suction at the suction segment 57d to keep the wafer 55 stable in that region. In addition, in addition thereto, an additional vacuum 53 may be applied to each of the remaining suction segments 57a to 57c or to regions located between the suction segments. Then, a constant and sufficient depression is applied to each of the suction segments, and the wafer 55 is stably fixed by the upper surface 56 of the chuck.
This situation is also illustrated by FIG. Similar to the situations described above, a main vacuum 61 and an auxiliary vacuum 62 are applied to the cascade circuit 63. As illustrated by the pressure gauges outlined below the suction segments 66a to 66d, the vacuum (negative pressure) applied to each of the suction segments 66a to 66d is -1 bar.
FIG. 7 shows an embodiment of a measuring circuit for determining at which of the suction segments 71a, 71b and 71c a wafer closes off the corresponding suction segment most densely. For this purpose, an auxiliary vacuum 76 is provided, which is branched off via a throttle 75 from the main vacuum 77. The auxiliary vacuum is applied to each of the suction segments 71a to 71c via the check valves 73a to 73c. The depression on the individual suction segments is then measured by the measuring means 72a, 72b and 72c, respectively. Subsequently, it is determined at which of the suction segments the absolute value of the negative pressure is maximum. Thereafter, the corresponding switch 74a, 74b and 74c is actuated to apply the main vacuum 77 to the corresponding suction segment. After suction of the wafer in this suction segment, the procedure is repeated, d. H. it is again checked in which of the (remaining) suction segments the absolute value of the negative pressure has a maximum, and the main vacuum is applied by switching the corresponding switch to this suction segment.
Figure 8 shows a possible division of the upper surface 80 of a chuck according to an embodiment of the invention. The upper surface 80 is formed as a circular disk. Due to the division, the upper surface 80 is divided into several suction segments. For example, a circular suction segment 81 is arranged around the center of the disc. Similarly, around the center of the upper
Surface 80 a larger circular area arranged, which is divided by three with respect to the center of the upper surface 80 radially extending straight lines that divide this larger circular area in three equal-sized suction segments 82a, 82b and 82c. Of course, the area of these suction segments does not overlap with the surface of the inner suction segment 81; in other words, the surface of the inner suction segment 81 is separated from the surfaces of the suction segments 82a to 82c. Another area is between the suction segments 82a-82c and the rim radius of the upper surface 80 of the chuck. This area is divided into four equal suction segments 83a, 83b, 83c and 83d by four straight lines which are radially aligned with respect to the center of the upper surface 80.
FIG. 9 shows an image of the embodiment of the upper surface already illustrated in FIGS. 1 and 2 and already discussed there. In this image, through-holes 91 can be seen at several locations in the grooves 92 connecting the grooves 92 to inputs (not shown) provided below the upper surface 93 of the chuck to apply the vacuum, as described in relation to the figures 1 and 2 is described.
Figure 10 shows an image of the bottom surface 100 of one embodiment of the chuck. A main vacuum channel 101 is spirally arranged on the lower surface 100. The vacuum channel 101 is subdivided into several sections, which are separated by check valves 102 from each other. The arrangement forms an embodiment of the cascade circuit, as illustrated and described with reference to FIGS. 2 and 3. While the invention has been illustrated and described in detail in the figures and the foregoing description, this illustration and description are to be considered illustrative or exemplary rather than limiting. It should be understood that changes and modifications may be made by those skilled in the art within the scope of the following claims. In particular, the present invention encompasses further embodiments with any combination of features from various embodiments described above and below.
Moreover, in the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit may perform the functions of several features listed in the claims. In particular, the terms "substantially," "about," "approximately," and the like, with respect to an attribute or value, mean an exact determination of the corresponding attribute or value. "" Reference numerals contained in the claims are not to be construed as limiting.

权利要求:
Claims (19)
[1]
claims
A jig for sucking and holding a wafer, comprising a planar upper surface divided into a plurality of suction segments, each of the suction segments being adapted to exhaust a fluid; and a bottom surface, wherein the top surface is adapted to be approximated within a fluid to a wafer such that two or more of the suction segments are covered by the wafer, at least loosely covered; and the suction segments are each separately activated.
[2]
2. The jig of claim 1, wherein the jig further comprises: means, preferably a throttle, configured to apply an auxiliary vacuum to the individual suction segments, respectively; means preferably comprising at least one pressure sensing means or at least one flow rate detecting means and arranged to measure at each of the suction segments the depression or flow rate of the volume flow of fluid aspirated from the respective suction segment upon application of the auxiliary vacuum; and a means, preferably a mechanical and / or electrical means associated with each of the means for measuring the negative pressure or the flow rate and is adapted to determine at which of the suction segments when applying the auxiliary vacuum, a maximum absolute value of the negative pressure or a minimum flow rate of the fluid is measured.
[3]
3. A tensioner according to claim 1 or 2, wherein the upper surface of the jig is a disc; an inner suction segment is disposed around the center of the upper surface; further suction segments are arranged as rings around the inner suction segment; and wherein the individual suction segments are preferably separated from the other suction segments, respectively.
[4]
The jig of claim 3, wherein each of the suction segments comprises a system of interconnected grooves disposed on the upper surface of the jig, and wherein preferably each system of interconnected grooves comprises one or more grooves arranged as concentric circles around the Center of the upper surface are designed.
[5]
5. The jig of claim 1, wherein the plurality of suction segments are disposed on the top surface such that on the top surface a virtual spiral path extends from a point within one of the suction segments and circumferentially to the edge of the top surface, the path each the suction segments enters and / or leaves only once.
[6]
6. The jig of claim 1 to 5, wherein each suction segment is connected to a main vacuum distribution means disposed on the lower surface of the jig and adapted to apply a vacuum to each suction segment; and wherein the application of vacuum to the individual Ansaugsegmente, possibly with the exception of a suction segment, is controllable via a valve.
[7]
A jig as claimed in claim 6 when dependent on claim 5, wherein the means for applying the main vacuum comprises a main vacuum channel having an inlet adapted to apply vacuum; each of the suction segments is connected to the main vacuum channel via a side channel having an orifice to the main vacuum channel; a respective valve is arranged between two adjacent orifices in the main vacuum channel, so that the main vacuum channel has a plurality of sections which are separated by these valves; the side channels are arranged such that two adjacent sections of the main vacuum channel are respectively connected to adjacent suction segments.
[8]
8. A jig according to claim 7, wherein each of these valves is a check valve, for example, a ball check valve, a diaphragm check valve, a flapper check valve, a Kippscheibenrückschlagventil, Absperrrückschlagventil, a piston check valve, a sleeve check valve or a lip check valve; wherein each of the check valves is adapted to automatically open when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum channel is equal to or greater than a predetermined value; and wherein each of the check valves is preferably configured to open only when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum passage is a value corresponding to a state in which the wafer is sealed abuts the suction segment which is connected to the adjacent to the direction of the channel entrance to the check valve portion.
[9]
9. A method of aspirating and holding a wafer by a jig, the jig comprising: a planar upper surface divided into a plurality of suction segments, the suction segments each being adapted to exhaust a fluid; and a lower surface; the method comprising the steps of: (9a) approximating wafer and top surface of the chuck within a fluid so that two or more of the suction segments are covered, at least loosely covered, by the wafer; (9b) selecting a suction segment having a minimum distance to the wafer from the not yet activated suction segments; (9c) activating the aspiration segment selected in step (9b); (9d) after the wafer in the region of the last activated suction segment is tight against the upper surface of the jig and as long as at least one suction segment is not yet activated: repeating steps (9b) to (9d).
[10]
10. The method of claim 9, wherein step (9b) of selecting a suction segment having a minimum distance to the wafer comprises the steps of: (10a) measuring the distance from each of the suction segments to the surface of the wafer opposite the respective suction segment; (10b) determining a suction segment, which has a minimum distance to the wafer, from the not yet activated suction segments.
[11]
11. The method of claim 10 wherein step (10b) of measuring the distance comprises the steps of: (la) applying an auxiliary vacuum to the not yet activated intake segments, preferably via a throttle; (llb) for each of the suction elements to which an auxiliary vacuum has been applied in step (11a): measuring the negative pressure or the flow rate of the volume flow of the extracted fluid, preferably via a pressure detecting means or a flow amount detecting means; and wherein step (10b) of determining a minimum distance comprises the following steps: (11c) determining which of the suction elements to which an auxiliary vacuum is applied, a maximum absolute value of the negative pressure or a minimum flow rate of the fluid is measured, preferably via a mechanical one and / or electrical means connected to each of the pressure sensing means or each of the flow rate detecting means.
[12]
12. The method of claim 9, wherein the sequence of the suction segments selected in step (9b) is predefined according to a known shape of the wafer.
[13]
13. The method according to any one of claims 9 to 12, wherein the upper surface of the jig is a disc; an inner suction segment is disposed around the center of the upper surface; further suction segments are arranged as rings around the inner suction segment; and wherein the individual suction segments are preferably separated from the other suction segments, respectively.
[14]
14. The method of claim 13, wherein each of the suction segments comprises a system of interconnected grooves disposed on the upper surface of the jig, and wherein preferably each system of interconnected grooves comprises one or more grooves arranged as concentric circles around the Center of the upper surface are designed.
[15]
15. The method of claim 12, wherein the plurality of suction segments are disposed on the upper surface such that on the upper surface a virtual spiral path extends from a point within one of the suction segments and circumferentially to the edge of the upper surface Enters and / or leaves intake segments only once; and wherein the sequence of suction segments selected in step (9b) follows the virtual spiral path, wherein the first suction segment is the suction segment having the origin of the virtual spiral path.
[16]
A method according to any one of claims 9 to 15, wherein each suction segment is connected to a main vacuum distribution means disposed on the lower surface of the jig and adapted to apply a vacuum to each individual suction segment; wherein the application of a vacuum to the individual suction segments, optionally with the exception of a suction segment, is controllable via a valve; the method comprising the step of: (16a) applying a vacuum to the main vacuum distribution means, which step is started before or together with step (9c) and carried out as long as the wafer is to be held by the jig; and wherein step (9c) of activating a suction segment comprises the step of: (16b) if the suction segment is controllable via a valve: opening the valve designed to control the corresponding suction segment, otherwise: starting step (16a).
[17]
17. A method according to claim 16 as dependent on claim 12, wherein the means for applying the main vacuum comprises a main vacuum channel having an input for applying vacuum; each of the suction segments is connected to the main vacuum channel via a side channel having an orifice to the main vacuum channel; a respective valve is arranged between two adjacent orifices in the main vacuum channel, so that the main vacuum channel has a plurality of sections which are separated by these valves; the side channels are arranged such that two adjacent sections of the main vacuum channel are respectively connected to adjacent suction segments; and wherein step (9b) of selecting a suction segment comprises: if step (9b) is performed during the performance of the method for the first time: selecting the suction segment connected to the portion of the main vacuum adjacent to the inlet; otherwise: selecting the suction segment connected to that portion of the main channel adjacent to the portion connected to the suction segment previously selected in step (9b).
[18]
18. The method of claim 17 wherein each of these valves is a check valve, for example, a ball check valve, a diaphragm check valve, a flapper check valve, a Kippscheibenrückschlagventil, Absperrrückschlagventil, a piston check valve, a sleeve check valve or a lip check valve; wherein each of the check valves is adapted to automatically open when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum channel is equal to or greater than a predetermined value; and wherein each of the check valves is preferably configured to open only when the absolute value of the negative pressure in the portion adjacent to the check valve in the direction of the entrance of the main vacuum passage is a value corresponding to a state in which the wafer is sealed abuts the suction segment which is connected to the adjacent to the direction of the channel entrance to the check valve portion.
[19]
The method of claim 17 or 18, comprising the further step of: (19a) holding the wafer completely by the jig: applying an additional vacuum to the main vacuum channel from the side opposite the entrance.

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同族专利:

公开号 | 公开日

DE112013007462T5|2016-06-30|

WO2015043638A1|2015-04-02|

JP2016532282A|2016-10-13|

AT517792A3|2018-04-15|

CN105765708A|2016-07-13|

KR20160062057A|2016-06-01|

TW201526151A|2015-07-01|

US20160240414A1|2016-08-18|

CN105765708B|2018-08-31|

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法律状态:
2018-09-15| REJ| Rejection|Effective date: 20180915 |

优先权:

申请号 | 申请日 | 专利标题

PCT/EP2013/070092|WO2015043638A1|2013-09-26|2013-09-26|Chuck for suction and holding a wafer|

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