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    • 专利摘要:
    Encapsulation structure comprising at least: - a hermetically sealed cavity in which a micro-device is encapsulated, - a substrate (102) whose one face (115) delimits one side of the cavity, - at least two trenches (116) formed through said face of the substrate, interior volumes of each of the trenches communicating with one another, - first portions of getter material (112) covering at least part of the side walls of the trenches.
    公开号:FR3014241A1
    申请号:FR1361827
    申请日:2013-11-29
    公开日:2015-06-05
    发明作者:Xavier Baillin
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    [0001] The invention relates to an encapsulation structure comprising a hermetically sealed cavity in which at least one micro-device, also called microsystem or microcomponent, for example of the type, is encapsulated. MEMS (electromechanical microsystem), NEMS (electromechanical nano-system), MOEMS (optoelectromechanical microsystem), NOEMS (opto-electromechanical nano-system), or infrared micro-detector type, or more generally any device intended to be encapsulated in a controlled atmosphere, possibly with one or more electronic components, forming for example an integrated circuit, and a getter material.
    [0002] The invention also relates to a method for encapsulating at least one micro-device for producing such an encapsulation structure. PRIOR ART Certain micro-devices, such as those of the MEMS, NEMS, MOEMS or infrared micro-detector type, require for their proper functioning to be enclosed, or encapsulated, hermetically in a cavity whose atmosphere is controlled ( control of the nature of the gas (s) and pressure in the cavity). Such encapsulation can be performed collectively for several micro-devices made on the same substrate (or wafer), called first substrate. Each of the micro-devices is then encapsulated in a cavity formed by transfer and hermetic sealing of a cover, for example formed by a second silicon or glass substrate, on the first substrate. This hermetic assembly between the first substrate and the second substrate, called "wafer-to-wafer" (W2W) and collectively forming the encapsulation cavities of micro-devices, protects the atmosphere in the cavities by preventing gas leaks between the interior of the cavities and the external environment. Alternatively, the cavities may be formed by encapsulation type TFP ("Thin Film Packaging"), or PCM (Thin Film Packaging), the covers being in this case formed of one or more thin layers superimposed and made on the first substrate via the use of a sacrificial material on which the thin layer or layers are deposited. The addition of non-evaporable getters (NEG) in the cavities, for example in the form of solid portions of getter material disposed in these cavities, makes it possible to control the characteristics of the atmosphere within the cavities via a gaseous pumping performed by these cavities. getters. The portions of getter material may be made from a thin layer deposition of the getter material made on one or the other of the two substrates, prior to the W2W assembly operation between the two substrates, or from a deposit on the first substrate in the case of encapsulation type TFP. A shaping of the portions of getter material in the plane of the surface of the substrate on which the getter material is deposited is then carried out by implementing photolithographic technological operations and etching of the thin layer of getter material. In the case of encapsulation of the TFP type, the getter material can be produced in the form of a thin layer corresponding to the first layer of the thin film stack of the cover, thus forming the inside wall of the cover defining the cavity. . Alternatively, it is possible to deposit the getter material discretely, directly in the desired form. For this, the getter material can be deposited directly on one or the other of the two substrates either through a stencil or by lift-off through a photoresist film previously photolithographically formed, this resin film. being removed after depositing the getter material therethrough. In general, during a W2W type assembly, the deposited getter is monolithic, of square or rectangular shape and only the face opposite to that in contact with the substrate on which the getter is deposited is in contact with the atmosphere of the cavity. The getter may be deposited on the substrate which accommodates the device, that is to say the first substrate, or on the second substrate serving as a cover. In the case of an encapsulation of the TFP type, the getter can be deposited either in an identical manner to the preceding case, that is to say on the first substrate, or on the sacrificial layer which makes it possible to construct the cover in thin layers. In all cases, only the face opposite to that in contact with the host substrate or the thin layers of the cap is capable of performing absorption and / or gas adsorption. In addition, in such a configuration, the area necessary for producing the portion of getter material is important. US 5,921,461 discloses an encapsulation structure in which light sensors are encapsulated in a cavity defined between a base and a cover assembled to each other after the deposition of the getter. The getter is deposited on the base, in an area that does not include the sensors and not lying opposite transparent windows formed in the hood. The getter can in particular be made in the form of a grid, which allows the sensors to be made between the portions of getter material forming the grid. Although such a configuration makes it possible to precisely position the portions of getter material on the base without disturbing the operation of the sensors, and thus reduce the constraints related to the area necessary for producing the getter material with respect to a portion of monolithic getter material the surface of getter material thus obtained may in certain cases prove to be insufficient, such as for example to reach a high vacuum of the order of 10-4 to 10-3 mbar within the cavity.
    [0003] In order to increase the area of getter material exposed in the cavity, document FR 2 976 933 describes an encapsulation structure comprising a getter material deposited on a gas-permeable material. Thus, the face of the getter material in contact with the gas-permeable material is accessible and capable of carrying out adsorption and / or gaseous absorption, in addition to the other faces of the getter material.
    [0004] Although such a structure makes it possible to obtain an increased gas pumping capacity for a given portion of getter material, this structure is not suitable when the available surface area for achieving the getter is reduced and / or irregular, given the structure monolithic portion of getter material made.
    [0005] SUMMARY OF THE INVENTION An object of the present invention is to propose an encapsulation structure that makes it possible to have both a large area of getter material exposed in the cavity of the encapsulation structure while requiring only one surface. reduced occupancy in the cavity for producing the getter material and / or which is compatible with an irregular receiving surface. For this, it is proposed an encapsulation structure comprising at least: - a hermetically sealed cavity in which a micro-device is encapsulated, a substrate, a face of which defines one side of the cavity, one or more trenches formed through said face; substrate, first portions of getter material covering at least partially side walls of the trench or trenches.
    [0006] The present invention furthermore proposes an encapsulation structure comprising at least: a hermetically sealed cavity in which a micro-device is encapsulated, a substrate whose one face delimits one side of the cavity, at least two trenches formed through said face; substrate, interior volumes of each of the trenches communicating with each other, - first portions of getter material at least partially covering the side walls of the trenches. The realization of the portions of getter material within trenches formed in the substrate (this substrate may correspond to a first substrate on which the micro-device is made and / or to a second substrate forming the hood of the cavity in the case of a W2W assembly between the first substrate and the second substrate) thus makes it possible to meet the need for a getter having a small footprint as regards the occupancy surface on the substrate by using the surfaces of the side walls of the trenches on which are arranged portions of getter material. Thus, for a given surface of the substrate corresponding to the surface occupied by the trenches, the surface of the first portions of getter material disposed on the side walls of these trenches may be greater than the surface of the substrate occupied by these trenches. In addition, for a given area of occupation on the substrate, the pumping capacity of the getter material obtained with such an encapsulation structure may be greater than that which would be obtained with a portion of getter material deposited directly on this surface. occupation without trench. The production of the first portions of getter material at least on the side walls of the trenches also makes it possible to produce these first portions of getter material on irregular reception surfaces because these first portions of getter material do not require having, at the level of of the substrate, a large, flat and even surface. Indeed, the fact that the trenches are distributed evenly or not in the substrate does not affect the gaseous pumping capacity of the getter material portions formed on the side walls of these trenches. The use of the sidewalls of the trenches to dispose portions of getter material makes it possible to judiciously locate the getter material in areas that can be narrow and so as not to disrupt the operation of the encapsulated micro-device or devices.
    [0007] Moreover, with such an encapsulation structure, apart from the trenches, it is not necessary to structure the substrate at which the getter material portions are made, which facilitates the implementation of subsequent technological operations on this substrate. . The geometry of the trenches produced is also easily adjustable as a function of the absorption and / or gas adsorption needs in the encapsulation structure, and therefore as a function of the deposition area required for the getter material portions to achieve this absorption and or this gas adsorption. Finally, such an encapsulation structure is compatible with a W2W type assembly, that is to say via the assembly of two substrates together, or with a TFP type encapsulation.
    [0008] The encapsulation structure also makes it possible to reach a high vacuum of the order of 10-4 to 10-3 mbar within the cavity. Because the internal volumes of each of the trenches communicate with each other, it is possible to access these interior volumes via, for example, a single opening forming a direct access to the interior volume of one of the trenches. The trenches can be made in the substrate in a grid pattern such that each trench crosses at least one other trench. The encapsulation structure may further comprise one or more second portions of getter material disposed at one or more bottom walls of the trenches. This configuration makes it possible to take advantage also of the bottom wall or walls of one or more of the trenches, and thus to have, for the same occupation surface on the substrate, a larger surface of getter material making it possible to achieve absorption and / or adsorption of gas.
    [0009] The getter materials of the first and / or second portions of getter material may be chosen for example from zirconium and / or titanium and / or any other metallic material having gas absorption and / or adsorption properties and / or by a combination of these materials. The first portions of getter material may partially cover at least one of the trenches at said surface of the substrate. Thus, the surfaces of the first portions of getter material, and optionally the surfaces of one or more second portions of getter material when such second portions of getter material are formed at the bottom walls of one or more of the trenches, allowing gas pumping can be directly accessible from one or more free spaces between the first portions of getter material disposed on the side walls of a trench. As a variant, the first portions of getter material can completely cover the trenches at the level of said substrate face, and in which at least one opening is made through one of the first portions of getter material or through the substrate and makes contact the interior volumes of the trenches with an interior volume of the cavity. In this case, the surfaces of the first portions of getter material for gas pumping can be accessed from this opening. In addition, because the internal volumes of each of the trenches communicate with each other, a single opening may, for example, make it possible to bring the first portions of getter material into contact with the atmosphere in the cavity via this opening. In this case, the opening may be blocked by a plugging material. Such a plugging material, corresponding for example to a fusible material, can be used to put the internal volumes of the trenches in communication with the atmosphere of the cavity subsequently to the encapsulation of the micro-device, by releasing the opening of this material. capping (for example by melting the fuse material) after encapsulation. This may for example make it possible to release a volume of vacuum (or a particular pressure) or of a particular gas stored in the interior volumes of the trenches at a desired moment, for example to restore a certain level of vacuum or a particular gas pressure during the life of the micro-device, or to activate the pumping function of the portions of getter material at the desired time, after the completion of the encapsulation structure. In particular, it is possible to release a rare gas such as argon or krypton stored in the interior volumes of the trenches. In this case, the getter material can be used to pump the gases other than the rare gases present in the cavity, to arrive at a controlled rare gas atmosphere. Such a configuration is advantageous when a resonant micro-device operating under a partial pressure of gas is encapsulated in the cavity. The first portions of getter material may cover portions of said substrate face around the trenches. It is thus possible to use the parts of the surface of the substrate to increase the area of getter material exposed to the atmosphere of the cavity. The first portions of getter material may comprise columnar grains oriented in a direction forming a non-zero angle and less than 90 ° with the side walls of the trenches. Such an arrangement of the columnar grains of the getter material of the first portions makes it possible to increase the capacity of absorption and / or gas adsorption of the first portions of getter material. Dimensions of at least one of the trenches at said substrate face may be smaller than dimensions of said at least one of the trenches at a bottom wall of said at least one of the trenches. Such a configuration may advantageously be used when at least one of the trenches is also used as a vacuum or gas reserve to be released later to the realization of the encapsulation structure because with such dimensions, a larger volume of vacuum or gas can be stored in this or these trenches. The section of said at least one of the trenches, in a plane perpendicular to said face of the substrate, may be of trapezoidal type. At least a portion of at least one of the trenches may comprise a plurality of secondary trenches formed across said substrate face, arranged next to each other and whose internal volumes communicate with each other, the first portions of getter material being able to cover at least partly side walls of secondary trenches. Such secondary trenches may, for example, be used to increase the area of getter material produced by making the best use of the free surfaces of the substrate, these secondary trenches being for example made at regions of the substrate having a larger free surface than those of the other regions. of the substrate in which the remainder of the trench or trenches without secondary trenches is made. The invention also relates to a method for encapsulating at least one micro-device, comprising at least the implementation of the steps of: - producing at least two trenches through a face of a substrate such as volumes interiors of each trench communicate with each other; - Making first portions of getter material covering at least partially side walls of the trenches; hermetic closure of a cavity in which the micro-device is disposed and such that said face of the substrate delimits one side of the cavity.
    [0010] Such an encapsulation process may advantageously be implemented to achieve collective encapsulation of several micro-devices in different cavities to produce a packaging of these micro-devices under a controlled atmosphere.
    [0011] BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood on reading the description of exemplary embodiments given purely by way of indication and in no way limiting, with reference to the appended drawings in which: FIGS. 1 to 3 show diagrammatically structures of FIG. encapsulation, objects of the present invention, according to different embodiments; FIGS. 4 to 16 schematically represent exemplary embodiments of trenches of encapsulation structures, objects of the present invention, in which portions of getter material are produced. Identical, similar or equivalent parts of the different figures described below bear the same numerical references so as to facilitate the passage from one figure to another. The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable. The different possibilities (variants and embodiments) must be understood as not being exclusive of each other and can be combined with one another. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS Referring firstly to FIG. 1 which schematically represents an encapsulation structure 100 according to a first embodiment.
    [0012] This encapsulation structure 100 is of the W2W type, that is to say is formed by the assembly of a first substrate 102 with a second substrate 104 forming the cover of the encapsulation structure 100, for example every two based on a semiconductor such as silicon, these two substrates 102 and 104 being assembled to one another via a sealing bead 106. A cavity 108 is formed by the space obtained between the first substrate 102 and the second substrate 104, the sealing bead 106 forming the side walls of the cavity 108. A micro-device 110, for example of the MEMS, NEMS, MOEMS, NOEMS or infrared detector type such as a micro-bolometer, is encapsulated in the cavity 108. In addition, a getter material 112, for example zirconium and / or titanium or any other metallic material having absorption and / or gas adsorption properties, is also present in the cavity 108, at the level of a hood wall formed by a fac e 113 of the second substrate 104, this face 113 forming an inner wall of the cavity 108.
    [0013] FIG. 2 diagrammatically represents the encapsulation structure 100 according to a variant of the first embodiment. In this variant embodiment, the getter material 112 is formed not on the face 113 of the second substrate 104, but on a face 115 of the first substrate 102, at which the micro-device 110 is also located and also forming an inner wall of the cavity 108. The getter material 112 is here formed at the periphery of the micro-device 110. According to another variant of the first embodiment, the encapsulation structure may comprise getter material both on the face 113 of the second substrate 104 and on the face 115 of the first substrate 102. FIG. 3 schematically represents the encapsulation structure 100 according to a second embodiment. In this second embodiment, the encapsulation structure 100 is not of the W2W type, but of the TFP or PCM type, that is to say has a cover 114 formed of one or more thin layers. As in the variant described with reference to FIG. 2, the getter material 112 is formed on the face 115 of the first substrate 102 on which the micro-device 110 is also located.
    [0014] With reference to FIGS. 4 to 16, the details of embodiment of the getter material 112 in the encapsulation structure 100 are described. In fact, in all the embodiments or variants of the encapsulation structure 100, the material getter 112 is made at least partly in trenches, or channels, formed through the face of the substrate at which the getter material 112 is located, that is to say through the face 113 of the second substrate 104 and or the face 115 of the first substrate 102. In the examples of FIGS. 4 to 16, the trenches are made through the face 115 of the first substrate 102, around the micro-device 110. The characteristics described below in connection with the FIGS. 4 to 16 also apply when the getter material 112 is formed in trenches made through the face 113 of the second substrate 104. FIG. 4 is a view from above of a portion of the first substrate 102 of the structure encapsulation 100 previously described in conjunction with Figure 2 or Figure 3. The getter material is formed as portions of getter material 112 covering at least in part (a portion of the height) of the side walls of trenches 116 (The portions of getter material 112 are deposited on upper portions of the side walls of the trenches 116) made through the face 115 of the first substrate 102, in a portion of the thickness of the first substrate 102. These trenches 116 are made under the in the form of a network which corresponds here, in a plane parallel to the face 115 of the first substrate 102 (plane (X, Y) in FIG. 4), to a grid pattern. In the example of FIG. 4, this grid pattern is formed by vertical trenches 116a, parallel to the Y axis, perpendicularly crossing horizontal trenches 116b parallel to the X axis. In a variant, the trenches 116 can intersect by forming a different pattern, for example a mesh of any shape, polygonal or not. It is also possible to make the trenches 116 as they do not intersect, or to make a single trench 116 for example formed around the micro-device 110. Figure 5 shows a profile view of a first embodiment trenches 116, here corresponding to one of the vertical trenches 116a. The dimension along the X axis of the trench 116 shown in Figure 5 corresponds to the width of this trench 116. The portions of getter material 112 are deposited on a portion of the side walls of the trench 116. These side walls of the trench 116 are substantially perpendicular to the face 115 of the first substrate 102. In this first embodiment, the getter material portions 112 deposited on the side walls of the trench 116 meet at the face 115 and thus completely cover the trench 116. wherein the portions of getter material 112 are formed. The interior of the trench 116 is not accessible from the portions of the trench 116 which are completely covered by the getter material portions 112. The getter material portions 112 also cover portions of the face 115 of the first substrate 102. lying around the trench 116.
    [0015] Deposition of the portions of getter material 112 along the side walls of the trenches 116 provides a getter material having columnar grains oriented in a direction forming a non-zero angle with the side walls of the trenches. Such an arrangement of the columnar grains of the getter material makes it possible to increase the capacity of absorption and / or gas adsorption of the first portions of getter material relative to a getter material conventionally deposited in the form of a monolithic portion on the substrate. Access to the interior of the trench 116, in order to communicate the interior of the trench 116 with the cavity 108, is obtained for example via at least a portion of at least one of the trenches 116 which is not covered by the portions of getter material 112 (not visible in FIG. 4). This access inside the trench 116 can be obtained as soon as the portions of getter material 112 are deposited by not depositing the getter material on this part of at least one of the trenches 116, for example via a "lift" type process. -off "with a dry film, or else subsequent to the deposition of the getter material by making an opening through one of the getter material portions 112. Because the trenches 116 made in the first substrate 102 intersect, the interior volumes trenches 116 communicate with each other. Access to the interior of one of the trenches 116 therefore makes it possible to communicate the interior volumes of all the trenches 116 with the atmosphere of the cavity 108. Thus, in the encapsulation structure 100 comprising such trenches 116, the side walls are covered at least in part by the portions of getter material 112 and whose interior volumes communicate with the cavity 108, absorption and / or gas adsorption is performed in the cavity 108 both by a first outer surface 118 portions of getter material 112 which is directly exposed in the cavity 108 at the face 115 of the first substrate 102, but also by a second surface 120 of the getter material portions 112 located inside the trenches 116, the sidewalls of the trenches 116 and exposed to the atmosphere of the cavity 108 via the previously described access, thus forming a large surface of mate getter material exposed to the atmosphere of the cavity 108 while minimizing the area occupied by the getter material at the face 115 of the first substrate 102. Figure 6 shows a side view of a second embodiment of the trenches 116 , corresponding here to one of the vertical trenches 116a. In this second exemplary embodiment, the getter material portions 112 do not completely cover the trenches 116 on which the getter material portions 112 are formed. Thus, the interior of the trenches 116 is accessible from a space 122 formed between the portions of getter material 112 over the entire length of the trenches 116. The portions of getter material 112 also cover portions of the face 115 of the first substrate 102 located around the trenches 116. In addition, the portions of getter material 112 are also deposited on a portion of the inner side walls of the trenches 116, and more precisely on the upper parts of these side walls. In this second exemplary embodiment, thanks to the spaces 122 formed between the portions of getter material 112, the surfaces 118 and 120 of the getter material portions 112 are directly exposed to the atmosphere of the cavity 108 without it being necessary to form subsequently an opening through one or more of the getter material portions 112. Figure 7 shows a profile view of a third embodiment of the trenches 116, here corresponding to one of the vertical trenches 116a. With respect to the second embodiment previously described with reference to FIG. 6, second portions of getter material 124 are arranged at the bottom walls of the trenches 116, which makes it possible to further increase the surfaces of getter material exposed to the surface. In the three embodiments previously described in connection with FIGS. 5 to 7, the portions of getter material 112 are made by depositing above the trenches 116. Thus, the fact that the portions of material getter 112 deposited correspond to one or the other of these three exemplary embodiments depends in particular on the width L with which the trenches 116 are made as well as the thickness e of the deposited portions of getter material 112. In these three examples, the width L of the trench 116 shown in FIG. 5 is smaller than that of the trench 116 shown in FIG. 6 which itself is smaller than that of the trench 116 shown in FIG. first example shown in Figure 5, the width L of the trenches 116 is for example equal to about 2 times the thickness e of the portions of getter material 112, this thickness e being for example greater than or equal to about 100 nm, and preferably between about 100 nm and 2 μm. In the second example shown in FIG. 6 and the third example shown in FIG. 7, the width L of the trenches 116 is, for example, greater than approximately twice the thickness e of the portions of getter material 112. In these three exemplary embodiments , the trench shape ratio 116, corresponding to the depth / width ratio of the trenches 116, may be equal to approximately 30 and for example between approximately 15 and 25. FIG. 8 represents a profile view of a fourth exemplary embodiment a trench 116, here corresponding to one of the vertical trenches 116a. As for the first example previously described with reference to FIG. 5, the thickness e of the portions of getter material 112 and the width L1 of the trenches 116 are chosen such that the portions of getter material 112 completely cover the trenches 116 on which the portions of getter material 112 are formed. One or more of the trenches 116, or each of the trenches 116, has a lower portion 126 of width L2 greater than the width L1 of the rest of the trench 116. The dimensions of the trench 116, at the face 115 of the first substrate 102 , are therefore smaller than the dimensions of the trench 116 at a bottom wall of the trench 116, that is to say at the lower part 126.
    [0016] Thus, if the portions of getter material 112 are deposited under a particular atmosphere, for example under vacuum, and access to the interior volumes of the trenches 116 is achieved only after the hermetic encapsulation of the micro-device 110, via the realization of an opening as described above, the lower portions 126 of the trenches 116 then form reserves of this particular atmosphere whose contents are added to the atmosphere of the cavity 108 after sealing during the realization of the opening , for example vacuum reserves to be added later to the vacuum with which the cavity 108 is hermetically sealed. Such trenches 116 are for example made from an SOI substrate (semiconductor on insulator), the trenches 116 being formed firstly through the entire thickness of the upper semiconductor layer of the SOI substrate, the lower portions 126 being then produced by etching the buried insulator layer of the SOI substrate. Such trenches 116, that is to say having lower portions 126 of greater width than the remainder of the trenches 116, may also serve for deposits of getter material portions 112 similar to those previously described in connection with FIGS. 7. Figure 9 shows a side view of a fifth embodiment of trenches 116, here corresponding to one of the vertical trenches 116a. The trench 116 is formed of several secondary trenches made substantially parallel to each other. In the example of FIG. 9, the trench 116 is formed of three secondary trenches 116.1 to 116.3 on which and in which the portions of getter material 112 are deposited (here, as in the first example previously described with reference to FIG. 5, that is, completely covering the secondary trenches and covering part of the side walls of the secondary trenches). This subdivision of the trench 116 into several secondary trenches can be done over at least a part of the length of the trench 116. Such a configuration has the particular advantage of further increasing the surface of getter material finally exposed in the cavity 108, while increasing the "reserve" of atmosphere, in terms of gas and / or pressure, that represents the internal volume of the trenches 116. The secondary trenches can communicate with each other, for example by joining one another at the level of a portion of the trench 116, as shown in Figure 10 which corresponds to a partial top view of such a trench 116. Alternatively, such secondary trenches may be made over the entire length of one or more of trench 116, or only part of the length of one or more of the trenches 116 as is the case in Figure 10. It is also possible that the trenches ndaires do not communicate with each other. In this case, each secondary trench comprises an independent access making it possible to communicate the interior of each of the secondary trenches with the cavity 108. These accesses are advantageously made at different times, for example depending on the needs in terms of absorption / gaseous adsorption and / or atmospheric reserve in the cavity 108. Such an embodiment of the trenches 116 may be applied for example for a deposition of portions of getter material 112 similar to those previously described in connection with Figure 5. It is it is also possible for one or more of the secondary trenches to have a lower part that is wider than the rest of the secondary trench, as previously described with reference to FIG. 8. In the previously described embodiments, the trenches 116 and / or the trenches secondary are rectilinear. Alternatively, trenches 116 and / or secondary trenches may not be straight. Figure 11 is a top view of an exemplary embodiment of a trench 116, a portion is connected to three secondary trenches 116.1, 116.2 and 116.3 each substantially circular or elliptical shape. Such an embodiment of the trenches 116 may be applied for deposits of getter material portions 112 similar to those previously described in connection with FIGS. 5 to 7. It is also possible for one or more of these secondary trenches to comprise a lower portion. wider than the rest of the secondary trench, as previously described in connection with Figure 8. When the portions of getter material 112 are deposited on the face of the substrate around the trenches 116 (as is the case for all previously described embodiments), a flattening and / or electrical isolation of the face 113 or 115 of the substrate on which the getter material portions 112 are deposited can be made by covering the portions of getter material 112 and the remainder of the face 113 or 115 of the substrate by a passivation layer 128 adapted to achieve such a planarization and / or such an electrical insulation However, the SiO 2 or SiO 2 deposited at a thickness greater than that of the portions of getter material 112, for example between about 1 μm and 10 μm (see Figure 12). The material of the passivation layer 128 is chosen from the materials which are the least favorable for degassing after deposition and during a rise in temperature of this material. Distribution layers (RDL for "redistribution layer") forming several insulating metal levels may also be produced above the face 113 or 115 on which are the portions of getter material 112, or above the layer of passivation 128. When the portions of getter material 112 are covered by another material, the gaseous pumping function is performed by the portions of the getter material portions 112 on the side walls of the trenches 116, from the faces 120 of the portions of the getter material 112. According to another variant, it is possible to carry out, after the deposition of the portions of getter material 112, a chemical-mechanical planarization of the getter material with a stop on the face 113 or 115 of the substrate. Such an alternative embodiment is shown in FIG. 13. The plane surface thus obtained can then be used for the implementation of other steps such as the production of a passivation layer or distribution layers. Such a planarization can be applied for deposits of portions of getter material 112 similar to those previously described in connection with FIGS. 6 and 7. FIG. 14 represents a view from above of a portion of the first substrate 102 of the structure of FIG. encapsulation 100 previously described in connection with Figure 2 or Figure 3, and wherein the getter material portions 112 completely cover the trenches 116. In this figure, an opening 130 is formed through the getter material portions 112 formed on one of the trenches 116, thereby communicating the atmosphere of the cavity 108 with the interior volumes of the trenches 116, these internal volumes communicating with each other because the trenches 116 intersect.
    [0017] As a variant, the opening 130 could be made through the face 115 of the first substrate 102. Such an opening could in particular be made when the substrate comprising the trenches 116 is of the SOI type, this opening being able to communicate the inside of the trenches 116. with the atmosphere of the cavity 108 via an etching of a portion of the buried dielectric layer thus making it possible to join the interior of one of the trenches 116 with the opening 130 made through the substrate. Such a variant can be implemented by selectively etching the buried dielectric material with respect to the getter material. In the example shown in FIG. 15, a localized deposit of a plugging material 132, for example corresponding to a fusible material such as a metal or a metal alloy comprising, for example, indium and / or tin and / or AuSn and / or AuSi, is made on the face 115 of the first substrate 102 near the opening 130. Thus, after the encapsulation of the micro-device 110, it is possible to no longer expose the interior of the trenches 116 to the atmosphere of the cavity 108 by melting the plugging material 132 which, by capillarity, will come to plug the opening 130.
    [0018] The amount of sealing material 132 deposited is chosen such that this material can form a plug of sufficient size to hermetically seal the opening 130. FIG. 16 represents another embodiment in which the opening 130 is plugged with a material of FIG. capping 134, corresponding for example to a fusible material, before the hermetic encapsulation of the micro-device 110 in the cavity 108. This plugging material 134 is made such that the surface of the opening 130 is slightly smaller than the surface of the material stopper 134 deposited. The thickness of the capping material 134 is preferably minimized while remaining sufficient to seal the opening 130. After encapsulation, it is possible to melt the capping material 134 which then releases the opening 130 in that the plugging material 134 will then spread out by wetting on the getter material, thus exposing the internal volumes of the trenches 116 to the atmosphere of the cavity 108. The nature of the plugging material 134 is chosen in particular as a function of the temperature at which the encapsulation is performed, and corresponds for example to a eutectic alloy such as AuSi, AuSn, or AIGe. Thus, the surfaces 120 of the getter material portions 112 in the trenches 116 are protected from the ambient atmosphere throughout the implementation of the encapsulation process. In addition, if the deposition of the sealing material 134 is carried out under vacuum or under a particular gaseous atmosphere, the interior volumes of the trenches 116 then form vacuum reserves or that particular atmosphere which can be released at any time after encapsulation of the micro-device 110 in the cavity 108, the amount of these reserves can be adjusted according to the dimensions, and in particular the depth, of the trenches 116. After the hermetic closure of the cavity 108, the portions of getter material 112 are thermally activated by exposing the encapsulation structure 100 to a temperature triggering absorption and / or gas adsorption of the getter material. This thermal activation temperature of the getter material depends in particular on the nature of the getter material. In all the previously described embodiments and embodiments, it is possible to produce, between the portions of getter material 112 and the material of the substrate on which the portions 112 are made, an underlayer of material enabling the temperature of the substrate to be adjusted. thermal activation of the getter material. Such an adjustment sub-layer corresponds for example to a layer of chromium and / or platinum and / or aluminum, with a thickness of between approximately 10 nm and 100 nm. The presence of such an adjustment sub-layer under the portions of getter material 112 makes it possible to modify the temperature at which the getter material of the portions 112 is thermally activated, and advantageously makes it possible to lower this temperature of thermal activation. A titanium and / or chromium and / or zirconium bonding underlayer, the thickness of which is for example between about 10 nm and 100 nm, can be produced under the adjustment underlayer in order to to improve the adhesion between the material of the first substrate 102 or the second substrate 104 and the material of the adjustment sub-layer. Details of the realization of such a sublayer for adjusting the thermal activation temperature of the getter material and of such an underlayer for adhesion are described in document FR 2 922 202.
    [0019] In all the previously described embodiments and embodiments, it is possible to temporarily cover and protect the portions of getter material 112 by a protective layer such as a layer of chromium with a thickness of between approximately a few nanometers and 100 nm, or by a nitride or oxide layer obtained by the dry route, as described in document FR 2 950 876. This protective layer may be removed when the getter material is thermally activated.
    [0020] We now describe a method of encapsulation of the micro-device 110, realizing the encapsulation structure 100. The trenches 116 are first made through the face 115 of the first substrate 102 and / or through the face 113 of the second substrate 104, these substrates being for example based on silicon. These trenches 116 are for example made via the implementation of photolithography and etching steps of the DRIE (deep reactive ion etching) type. A hard SiO 2 mask, for example with a thickness of between about 100 nm and 10 μm, makes it possible, for example, to engrave trenches 116 whose aspect ratio (depth / width) is equal to about 30.
    [0021] The portions of getter material 112 are then made on a portion of the lateral flanks of the trenches 116 and completely or partially covering the trenches 116 at the face 113 and / or 115 of the substrate in which the trenches 116 are made. The getter material is, for example, zirconium and / or titanium deposited to a thickness of between about 100 nm and 2 μm. Any underlays hooking and adjustment are performed prior to the realization of the portions of getter material 112. It is also possible to deposit a thick adjustment sub-layer, that is to say thick greater than about 100 nm, so as to increase the aspect ratio, or form factor, of the trench and thus promote the closure of the trench by depositing the getter. Such a case can be applied to the configuration previously described in connection with FIG. 5, with in this case the implementation of two deposits: one for the adjustment sub-layer and the other for the getter material. . These portions of getter material 112 may be made by lift-off, that is to say by deposition through a resin mask previously produced by photolithography and etching on the face 115 of the first substrate 102 and / or the face 113 of the second substrate 104. To produce the resin mask, a dry film of photosensitive resin having a thickness of between approximately 1 and 10 μm is advantageously used, this thickness possibly being even less than approximately 1 μm in order to obtain the best possible resolution for the film. photolithography implemented. When the width of the trenches 116 is small and close to about 1 .mu.m, a standard resin can be used to make the mask. After the deposit of the getter material, the resin mask and the getter material on the resin mask are removed. In a variant, the getter material portions 112 may be made by a deposition of the getter material on the assembly of the face 115 of the first substrate 102 and / or of the face 113 of the second substrate 104, and then photolithography and etching steps. getter material deposited to form the portions 112. Depending on the nature of the getter material, the etching can be carried out by wet see, or by dry route such as an RIE (reactive ion etching) etching. When the portions of getter material 112 are intended to be covered with a passivation layer such as the layer 128 described above, this passivation layer 128 is formed for example via a deposition by evaporation of SiO 2, this deposition may be carried out in the same frame as that used for depositing the portions of getter material 112. It is thus possible to create a vacuum reserve because the deposition by evaporation can be performed at a pressure of the order of 10-6 mbar. On the other hand, an oxide deposition by sputtering under a partial pressure of a carrier gas such as argon or krypton makes it possible to create a reserve of gas. When an opening 130 has been made, it is then possible to carry out the localized deposition of the closure material 132 near the opening 130. When the closure material 132 comprises gold, this deposit corresponds for example to a PVD deposit (Physical vapor deposition) made on the face of the substrate. When the capping material 132 comprises indium or tin, this deposit corresponds for example to a PVD deposited in part on the face of the substrate and on the getter material or on the adjustment sub-layer or on the underlayer grip. Alternatively, the opening 130 can be directly plugged by the sealing material 134.
    [0022] The micro-device 110 can be made on the first substrate 102 before or after the implementation of the various steps above. When the portions of getter material 112 are intended to be arranged next to the micro-device 110, the portions of getter material 112 are preferably made before the production of the micro-device 110 and protected in particular by not communicating the interior of the trenches 116 with the ambient atmosphere, for example by first blocking an opening with a sealing material as previously described in connection with FIG. 16, and possibly protecting the surfaces 118 of the portions of getter material 112 with a protective layer such as previously described. Although the encapsulation method previously described is carried out for the encapsulation of a single micro-device 110, this method is advantageously used to achieve a collective encapsulation of several micro-devices in different cavities arranged next to the micro-devices. others on the same substrate.
    权利要求:
    Claims (11)
    [0001]
    REVENDICATIONS1. An encapsulation structure (100) comprising at least: a sealed cavity (108) in which a micro-device (110) is encapsulated; - a substrate (102, 104) having a face (113, 115) delimiting a side of the cavity (108), - at least two trenches (116) formed through said face (113, 115) of the substrate (102, 104), interior volumes of each of the trenches (116) communicating with each other, - first portions of getter material (112) at least partially covering sidewalls of the trenches (116).
    [0002]
    The encapsulation structure (100) according to claim 1, wherein the trenches (116) are formed in the substrate (102, 104) in a grid pattern such that each of the trenches (116) intersects with at least one other trench (116).
    [0003]
    3. Encapsulation structure (100) according to one of the preceding claims, further comprising one or more second portions of getter material (124) disposed at one or more bottom walls of the trenches (116).
    [0004]
    4. Encapsulation structure (100) according to one of the preceding claims, wherein the first portions of getter material (112) partially cover at least one of the trenches (116) at said face (113, 115). substrate (102, 104).
    [0005]
    5. encapsulation structure (100) according to one of claims 1 or 3, wherein the first portions of getter material (112) completely cover the trenches (116) at said face (113, 115) of the substrate ( 102, 104), and wherein at least one opening (130) is formed through one of the first portions of getter material (112) or across the substrate (102, 104) and communicates the interior volumes of the trenches (116). ) with an interior volume of the cavity (108).
    [0006]
    The encapsulation structure (100) of claim 5, wherein the opening (130) is occluded by a plugging material (132, 134).
    [0007]
    The encapsulation structure (100) according to one of the preceding claims, wherein the first portions of getter material (112) cover portions of said face (113, 115) of the substrate (102, 104) lying around the trenches (116).
    [0008]
    8. Encapsulation structure (100) according to one of the preceding claims, wherein the first portions of getter material (112) comprise columnar grains oriented in a direction forming a non-zero angle and less than 90 ° with the side walls trenches (116).
    [0009]
    9. encapsulation structure (100) according to one of the preceding claims, wherein dimensions of at least one of the trenches (116), at said face (113, 115) of the substrate (102, 104), are smaller than dimensions of said at least one of the trenches (116) at a bottom wall of said at least one of the trenches (116).
    [0010]
    The encapsulation structure (100) according to one of the preceding claims, wherein at least a portion of at least one of the trenches (116) has a plurality of secondary trenches (116.1 - 116.3) formed through said face (113, 115) of the substrate (102, 104), arranged next to one another and whose internal volumes communicate with one another, the first portions of getter material (112) covering at least part of the side walls of the secondary trenches (116.1 - 116.3 ).
    [0011]
    11. A method for encapsulating at least one micro-device (110), comprising at least the implementation of the steps of: producing at least two trenches (116) through a face (113, 115) of a substrate (102, 104) such that interior volumes of each of the trenches (116) communicate with each other; producing first portions of getter material (112) at least partially covering sidewalls of the trenches (116); sealing a cavity (108) in which the micro-device (110) is disposed and such that said face (113, 115) of the substrate (102, 104) delimits a side of the cavity (108).
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    同族专利:
    公开号 | 公开日
    US9327963B2|2016-05-03|
    US20150151959A1|2015-06-04|
    FR3014241B1|2017-05-05|
    EP2897162B1|2016-08-17|
    EP2897162A1|2015-07-22|
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    法律状态:
    2015-11-30| PLFP| Fee payment|Year of fee payment: 3 |
    2016-11-30| PLFP| Fee payment|Year of fee payment: 4 |
    2018-08-31| ST| Notification of lapse|Effective date: 20180731 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1361827A|FR3014241B1|2013-11-29|2013-11-29|ENCAPSULATION STRUCTURE COMPRISING PARTIALLY FILLED TRENCHES OF MATERIAL GETTER|FR1361827A| FR3014241B1|2013-11-29|2013-11-29|ENCAPSULATION STRUCTURE COMPRISING PARTIALLY FILLED TRENCHES OF MATERIAL GETTER|
    EP14195216.8A| EP2897162B1|2013-11-29|2014-11-27|Encapsulation structure including trenches partially filled with getter material|
    US14/555,913| US9327963B2|2013-11-29|2014-11-28|Encapsulation structure comprising trenches partially filled with getter material|
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