JP2011152592A - Mems structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MEMS structure in which the machining accuracies of functionally effective portions are increased. <P>SOLUTION: This MEMS structure 1 includes a movable part 40 and fixed parts 50 which are formed by etching a semiconductor substrate 3 joined to a support substrate 2. The movable part 40 and the fixed parts 50 has respective movable electrodes 41 and fixed electrodes 51 which are disposed so as to face each other through first gaps 62. The MEMS structure 1 detects a physical quantity based on the displacement of the movable electrodes 41 relative to the fixed electrodes 51. Net-like groove parts 10 are formed in the area of the semiconductor substrate 3 which is brought into contact with the support substrate 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MEMS structure.

  2. Description of the Related Art Conventionally, a MEMS structure in which a comb-shaped movable electrode and a comb-shaped fixed electrode that are opposed to each other with a gap in an engaged state is formed by etching a semiconductor substrate bonded to a support substrate is known. (For example, refer to Patent Document 1).

  In Patent Document 1, a dummy pattern for adjusting the etching time in the depth direction is provided in the vicinity of a long and narrow pattern arranged in a comb shape, thereby preventing the long and narrow pattern portion from being excessively side-etched. .

JP 2000-77681 A

  By the way, when a plurality of gaps having different widths are formed by etching, that is, when etching is performed using an etching mask in which patterns having different etching widths are mixed, a microloading effect may occur. The microloading effect refers to a phenomenon in which the progress of etching is slower in a narrow gap than in a wide gap. As described above, when the microloading effect occurs, the stress generated in the semiconductor substrate due to the difference in linear expansion coefficient between the support substrate and the semiconductor substrate immediately before the etching of the narrow portion is completed at the bottom of the narrow gap. Concentration and cracks at the bottom may cause damage.

  That is, in the above-described conventional technology, there is a possibility that the processing accuracy of a functionally effective part may be lowered.

  Then, an object of this invention is to obtain the MEMS structure which can improve the processing precision of a functionally effective site | part.

  In the present invention, a movable part and a fixed part formed by etching a semiconductor substrate bonded to a support substrate are provided, and the movable part and the fixed part are arranged to face each other with a first gap. And a MEMS structure for detecting a physical quantity based on the relative displacement of the movable electrode with respect to the fixed electrode, and forming a mesh-like groove in a region of the semiconductor substrate that contacts the support substrate. The most important feature.

  According to the present invention, since the mesh-like groove is formed in the region of the semiconductor substrate that contacts the support substrate, the stress generated in the semiconductor substrate can be absorbed by the mesh-like groove. As a result, when etching is performed, stress can be prevented from concentrating on a functionally effective portion, and the processing accuracy of the functionally effective portion can be increased.

FIG. 1 is a plan view schematically showing a MEMS structure according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the steps of dry etching the semiconductor substrate of the MEMS structure according to the first embodiment of the present invention in order from (a) to (c). FIG. 3 is a plan view schematically showing a MEMS structure according to the second embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view schematically showing a groove portion according to the second embodiment of the present invention. FIG. 5 is a plan view schematically showing a MEMS structure according to the third embodiment of the present invention. FIG. 6 is a plan view schematically showing a MEMS structure according to the fourth embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view schematically showing a groove portion according to the fourth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, as the MEMS structure, a biaxial acceleration sensor capable of detecting accelerations in the X-axis and Y-axis directions perpendicular to each other will be exemplified.

  Moreover, the same component is contained in the following several embodiment. Therefore, in the following, common reference numerals are given to those similar components, and redundant description is omitted.

(First embodiment)
As shown in FIGS. 1 and 2, an acceleration sensor 1A according to the present embodiment includes a substantially square silicon substrate (semiconductor substrate) 3 on which a semiconductor element device is formed, and one side of the silicon substrate 3 (lower surface in FIG. 2). ) And a substantially square glass substrate (support substrate) 2. In the present embodiment, the silicon substrate 3 and the glass substrate 2 are bonded by anodic bonding.

  Then, by forming a plurality of gaps 60 having different widths in the silicon substrate 3 by a known semiconductor process, a substantially rectangular frame portion 30, a movable portion 40, a fixed portion formed on the peripheral portion of the silicon substrate 3. 50, a stopper portion 7, a beam (spring portion) 43, and a support portion 44 that supports the movable portion 40 via the beam (spring portion) 43.

  These gaps 60 are formed so that the side wall surfaces are perpendicular to the surface of the silicon substrate 3 by performing vertical etching processing such as reactive ion etching (RIE). Thus, the side walls of the gap 60 formed by the vertical etching process face each other substantially in parallel. As reactive ion etching, for example, ICP processing by an etching apparatus provided with inductively coupled plasma (ICP) can be used.

  The frame portion 30 and the support portion 44 are extended in a frame shape with a substantially constant width along the four peripheral edges (four sides) of the silicon substrate 3. The support portion 44 is disposed on the inner peripheral side of the frame portion 30 in a state of being separated with a substantially frame-shaped gap 61. The frame portion 30 and the support portion 44 are fixed to the glass substrate 2 by bonding the back surface side (the lower side in FIG. 2) to the surface of the glass substrate 2. That is, the frame portion 30 and the support portion 44 are regions that contact the glass substrate 2 of the silicon substrate 3. In addition, the fixed portion 50 and the stopper portion 7 are also bonded to the surface of the glass substrate 2 and are regions that contact the glass substrate 2 of the silicon substrate 3.

  Inside the support portion 44, four beams 43 are provided extending from the four corners of the support portion 44 in parallel to each side of the support portion 44 and in a spiral shape toward the center while being bent at right angles in the middle. . Each of the beams 43 extends over two sides of the support portion 44 without interfering with each other, and is connected to a corner portion of the movable portion 40 at the inner end portion. It functions as a spring element (spiral spring) that elastically moves and supports 40.

  That is, in this embodiment, the movable part 40 is given a function as a mass element (mass) that is movably supported by the beam 43 as a spring element, and a spring-mass system is configured by these spring elements and mass elements. The acceleration and angular acceleration can be obtained from the displacement of the movable part 40 as a mass element.

  And in order to detect the displacement of this movable part 40, in this embodiment, the movable electrode provided in the movable part 40 and the fixed electrode provided in the fixed part 50 are arranged opposite to each other with a first gap 62. The detection unit 6 is configured. By detecting the electrostatic capacitance between the movable electrode and the fixed electrode in the detection unit 6, the change of the first gap 62, that is, the displacement of the fixed electrode with respect to the movable electrode is detected.

  Specifically, as shown in FIG. 1, the movable portion 40 is movable in a comb-like shape extending in a strip shape in a direction substantially perpendicular to the side from the central portion 40 a toward the central portion of each side of the support portion 44. An electrode 41 is provided. In the present embodiment, the plurality of movable side comb teeth 41a are provided in parallel to each other at a constant pitch.

  On the other hand, the fixed portion 50 includes an anchor portion 53 provided adjacent to the corner portion 40 b of the movable portion 40, and the anchor portion 53 is an edge portion 54 that extends in a strip shape along each side of the support portion 44. It has. A comb-like fixed electrode 51 extending toward the central portion 40a side of the movable portion 40 is connected to the edge portion 54. In the present embodiment, the plurality of fixed-side comb teeth 51a are provided in parallel with each other at a constant pitch (the same pitch as the movable-side comb teeth 41a of the movable portion 40). The comb teeth 41a and the gap 62 are engaged with each other.

  In the detection unit 6, the first gap 62 between the movable comb teeth 41a and the fixed comb teeth 51a is narrower on one side (gap 62a) and wider on the other side (gap 62b) than the movable comb teeth 41a. ) And a capacitance between the comb teeth 41a and 51a facing each other through the gap 62a, that is, a capacitance between the fixed electrode and the movable electrode, with the narrow gap 62a as a detection gap. Is supposed to be detected.

  As shown in FIG. 1, the detection unit 6 is provided corresponding to the center of each side of the frame 30, and the detection unit 6 for detecting the X direction (upper and lower detection units 6 in FIG. 1) and Y Two detection units 6 for detecting the direction (left and right detection units 6 in FIG. 1) are provided.

  In FIG. 1, 4E is a first conductive layer electrically connected to the comb-like movable electrode 41 of the movable part 40 via the beam 43, and 5E is a comb-like fixed of the fixed part 50. This is a second conductive layer electrically connected to the electrode 51. The potentials of the movable portion 40 and the fixed portion 50 can be detected from the first and second conductive layers.

  Here, in the present embodiment, the first mesh-like groove portion 10 is formed in a lattice shape in the support portion 44. In the present embodiment, the first mesh-like groove portion 10 is provided over substantially the entire area of the support portion 44 in a plan view, and is a through groove penetrating in the thickness direction of the support portion 44.

  In addition to the gaps 62a and 62b, a gap 63 is provided between the anchor part 53 and the movable part 40 between the movable part 40 and the fixed part 50, and between the movable part 40 and the beam 43, A gap 64 is provided between the beams 43 and between the beam 43 and the support portion 44. Note that these gaps 60 (gap 61, 62a, 62b, 63, 64) may have different widths in the X-axis direction and the Y-axis direction.

  In the present embodiment, the first gap 62 between the comb-like movable electrode 41 and the comb-like fixed electrode 51 is formed to be narrower than the other gaps 61, 63, 64. One gap 62a of one gap 62 is formed to be narrower than the other gap 62b. In other words, in the present embodiment, the narrower gap 62 a of the first gaps 62 has the smallest width among the gaps 60. The first gap 62 has been described as being narrower than the other gaps 61, 63, 64. However, both the narrow gap 62a and the wide gap 62b are other gaps. It is not necessary to form narrower than 61, 63, 64. That is, it is sufficient that the narrow gap 62 a has the smallest width among the gaps 60, and the wide gap 62 b of the first gaps 62 has the same width as the other gaps 61, 63, 64. It may be wider than any of the widths.

  Here, in this embodiment, the sacrificial gap 70 s is formed in the silicon substrate 3 so as to be narrower than the narrowest gap 62 a. Specifically, the concave portion 8 is provided in the movable portion 40, and the bar-shaped protrusion 7 a is protruded from the stopper portion 7 into the concave portion 8. Forming.

  In the present embodiment, the rod-shaped protrusion 7 a is in the vicinity of the comb-like movable electrode 41 and the comb-like fixed electrode 51 from the stopper portion 7 and parallel to the comb-like movable electrode 41 and the comb-like fixed electrode 51. So as to protrude.

  Thus, in the present embodiment, the sacrificial gap 70 s is provided in the vicinity of the comb-like movable electrode 41 and the comb-like fixed electrode 51 in parallel. The width of the sacrificial gap 70 s is narrower than the first gap 62 a between the comb-shaped movable electrode 41 and the comb-shaped fixed electrode 51 that is the narrowest. For example, when the width of the gap 62a is 3 μm, the width of the sacrifice gap 70s is suppressed to 2 μm or less. Note that the sacrificial gap 70s is also formed by performing vertical etching, and it goes without saying that the width of the sacrificial gap 70s is a width that allows etching. At this time, the sacrificial gap 70s provided on both sides of the rod-like projection 7a may have different widths on both sides of the rod-like projection 7a. It is sufficient if the width is narrower than the width of the first gap 62a.

  Next, an example of a manufacturing process of the acceleration sensor 1A described above will be described.

  First, a silicon oxide film and a photoresist layer (not shown) are formed on the back surface (lower surface in FIG. 2) of the silicon substrate 3, and the photoresist layer is patterned to anisotropically etch the silicon oxide film. Then, after removing the photoresist layer, anisotropic etching is performed using the silicon oxide film as a mask to form the recess 3a. Next, the back surface side of the silicon substrate 3 and the front surface side (upper surface in FIG. 2) of the glass substrate 2 are overlapped and anodic bonded to each other, thereby forming the cavity 3C shown in FIG. To do. The displacement of the movable portion 40 is allowed by the hollow portion 3C. The cavity may be formed by providing a recess on the surface of the glass substrate 2, or the cavity may be formed by providing a recess on both the back surface of the silicon substrate 3 and the surface of the glass substrate 2.

  Thereafter, the photoresist layer applied and formed on the surface side (upper surface in FIG. 2) of the silicon substrate 3 is patterned by a photolithography technique. This patterning is performed along the shapes of the gap 60 and the sacrificial gap 70s described above, and the silicon substrate 3 is anisotropically etched using this photoresist layer as a mask, and after considering the stage of FIG. 2B, As shown in FIG. 2C, the movable portion 40, the fixed portion 50, the first mesh-like groove portion 10 and the like are formed. The anisotropic etching at this time is performed by, for example, reactive ion etching (RIE) using an inductive coupling method (ICP).

  According to the above embodiment, since the first mesh-like groove 10 is formed in the support portion 44 (the region in contact with the support substrate of the semiconductor substrate) that supports the movable portion 40 via the beam (spring portion) 43, The stress existing in the silicon substrate (semiconductor substrate) 3 can be absorbed by the first mesh-shaped groove 10. As a result, when the silicon substrate 3 is etched, it is possible to prevent stress from concentrating on the gap 60 (functionally effective part) in the middle of formation, and to process functionally effective parts such as electrodes. Accuracy can be increased. As described above, it is possible to increase the detection accuracy of the acceleration sensor 1A by suppressing the finish accuracy of the gap 60 from being lowered.

  Further, according to the present embodiment, the silicon substrate 3 is formed between the comb-like movable electrode 41 and the comb-like fixed electrode 51 which are the narrowest gap among the gaps 60 having different widths. A sacrificial gap 70s that is narrower than the gap (first gap) 62a is formed. Therefore, when the silicon substrate 3 is etched, the etching in the sacrifice gap 70s is the slowest due to the microloading effect. As a result, the stress generated in the silicon substrate 3 can be applied to the sacrificial gap 70s, and the stress can be prevented from being concentrated in the gap 60 (functionally effective part) in the middle of formation. The processing accuracy of functionally effective parts such as electrodes can be increased.

  In particular, in this embodiment, the sacrificial gap 70 s is formed in the vicinity of the comb-like movable electrode 41 of the movable part 40 and the comb-like fixed electrode 51 of the fixed part 50. For this reason, it is possible to more effectively suppress the stress generated in the silicon substrate 3 from being applied to the gap 60. As a result, the processing accuracy of the comb-shaped movable electrode 41 and the comb-shaped fixed electrode 51 can be further increased, and the detection accuracy of the acceleration sensor 1A can be further increased.

(Second Embodiment)
As shown in FIG. 3, the acceleration sensor 1B according to the present embodiment has a support portion 44 (support substrate for a semiconductor substrate) that supports the movable portion 40 via a beam (spring portion) 43, as in the first embodiment. 10A of 1st mesh grooves are formed in the area | region which contact | abuts.

  Here, this embodiment is mainly different from the second embodiment in that the first mesh groove 10A is on the side where the support portion 44 faces the glass substrate 2 as shown in FIG. 4 (in FIG. 4). The bottom 10b is left on the lower side. In other words, the first mesh groove portion 10A according to the present embodiment is a bottomed groove portion having a bottom portion 10b on the side of the support portion 44 that contacts the glass substrate 2.

  Also according to this embodiment described above, the same operations and effects as those of the first embodiment can be achieved.

  In addition, according to the present embodiment, since the first mesh-like groove portion 10A is a bottomed groove portion having the bottom portion 10b on the side of the support portion 44 that contacts the glass substrate 2, the first mesh-like groove portion 10A provides silicon. While absorbing the stress generated in the substrate 3, it is possible to prevent a decrease in the bonding area between the support portion 44 and the glass substrate 2 and to ensure high bonding strength.

(Third embodiment)
In the acceleration sensor 1 </ b> C according to the present embodiment, the fixed portion 50 has the anchor portion 53 as in the first embodiment.

  Here, this embodiment is mainly different from the first embodiment in that the second mesh-like groove portion 11 is formed in the anchor portion 53. In the present embodiment, the second mesh-like groove portion 11 is provided over substantially the entire edge portion 54 of the anchor portion 53, and is a through groove that penetrates in the thickness direction of the anchor portion 53.

  Also according to this embodiment described above, the same operations and effects as those of the first embodiment can be achieved.

  Further, according to the present embodiment, since the second mesh groove 11 is formed in the anchor portion 53 that fixes the comb-like fixed electrode 51 to the glass substrate 2, the second mesh groove 11 forms the silicon substrate 3. The generated stress can be absorbed. As a result, when the silicon substrate 3 is etched, it is possible to prevent stress from concentrating on the gap 60 (functionally effective part) in the middle of formation, and to process functionally effective parts such as electrodes. The accuracy can be further increased.

  In particular, in the present embodiment, the second mesh-like groove portion 11 is provided in the anchor portion 53 closer to the gap (the narrowest gap among the plurality of gaps having different widths) 62a than the support portion 44. There is also an advantage that it is possible to more effectively suppress stress concentration in the gap 60 (particularly, the gap 62a) in the middle of formation.

(Fourth embodiment)
As shown in FIG. 6, the acceleration sensor 1 </ b> D according to the present embodiment has a second mesh groove 11 </ b> A formed in the anchor portion 53, as in the third embodiment.

  Here, this embodiment is mainly different from the third embodiment in that the second mesh groove 11A has a bottom portion 11b on the side where the support portion 44 faces the glass substrate 2 as shown in FIG. It is to be left. That is, the second mesh-like groove portion 11A according to the present embodiment is a bottomed groove portion having the bottom portion 11b on the side of the support portion 44 that contacts the glass substrate 2.

  Also according to the present embodiment described above, the same operations and effects as those of the third embodiment can be achieved.

  In addition, according to the present embodiment, the second mesh-shaped groove portion 11A is a bottomed groove portion having the bottom portion 11b on the side contacting the glass substrate 2 of the support portion 44. While absorbing the stress generated in the substrate 3, it is possible to prevent a decrease in the bonding area between the anchor portion 53 and the glass substrate 2 and to ensure high bonding strength.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in each of the above-described embodiments, the biaxial acceleration sensor is exemplified as the MEMS structure. However, a uniaxial acceleration sensor or a triaxial acceleration sensor may be used. In addition to the acceleration sensor, an angular velocity sensor or a vibration sensor may be used. The present invention can be implemented even in other MEMS structures.

  Moreover, in each said embodiment, although what provided the groove part in any one of a support part and an anchor part was illustrated, you may make it provide in both. At this time, whether the groove portion is a through groove or a bottomed groove can be appropriately selected.

  Moreover, movable parts, fixed parts, and other detailed specifications (shape, size, layout, etc.) can be changed as appropriate.

1A, 1B, 1C, 1D Acceleration sensor (MEMS structure)
2 Glass substrate (support substrate)
3 Silicon substrate (semiconductor substrate)
40 movable part 50 fixed part 10, 10A first mesh groove part 10b bottom part 11, 11A second mesh groove part 11b bottom part 41 comb-like movable electrode 44 support part 51 comb-like fixed electrode 53 anchor part 60 gap 62 first 1 gap 62a narrowest gap 70s sacrificial gap

Claims (7)

A movable part and a fixed part formed by etching a semiconductor substrate bonded to a support substrate are provided, and each of the movable part and the fixed part has a movable electrode and a fixed electrode that are opposed to each other with a first gap. In the MEMS structure for detecting a physical quantity based on the relative displacement of the movable electrode with respect to the fixed electrode,
A MEMS structure, wherein a mesh groove is formed in a region of the semiconductor substrate that contacts the support substrate.   2. The MEMS structure according to claim 1, wherein the semiconductor substrate has a support portion that supports the movable portion via a spring portion, and a first mesh-like groove portion is formed in the support portion.   The MEMS structure according to claim 2, wherein the first mesh-shaped groove is a bottomed groove having a bottom.   The said fixing | fixed part has an anchor part fixed to the said support substrate, and formed the 2nd mesh-like groove part in the said anchor part, The any one of Claims 1-3 characterized by the above-mentioned. MEMS structure.   The MEMS structure according to claim 4, wherein the second mesh-shaped groove portion is a bottomed groove portion having a bottom portion.   The semiconductor substrate has a plurality of gaps with different widths, and the first gap has the narrowest gap among the plurality of gaps with different widths. 6. The MEMS structure according to claim 1, wherein a sacrificial gap narrower than a narrowest gap among the plurality of gaps having different widths is formed.   The movable electrode and the fixed electrode are a comb-shaped movable electrode and a comb-shaped fixed electrode facing each other with the first gap, and the sacrificial gap is located near the first gap. The MEMS structure according to claim 6, wherein the MEMS structure is formed substantially in parallel with the MEMS structure.

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