MEMS sensor and method for manufacturing the same

Abstract

To provide an MEMS sensor capable of simplifying a manufacturing process and improving sensitivity.SOLUTION: The MEMS sensor comprises: a first substrate 10 including on a front face 10a a cavity 12 with a part thereof exposed; an electrode 13 of a sensor element provided on the first substrate 10 and arranged in the cavity 12; a support part 14 provided on the first substrate 10 and supporting the electrode 13; an element separation part 15 formed on the first substrate 10 so as to cover the support part 14 and electrically separating the electrode 13 from the support part 14; an epitaxial growth layer 50 formed on the electrode 13 and the element separation part 15 of the first substrate 10; and a second substrate 20 bonded to the first substrate 10 to cover the sensor element. The epitaxial growth layer 50 includes a single crystal part 51 arranged on the electrode 13 and a polycrystalline part 52 arranged on the element separation part 15.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to MEMS sensors and methods for manufacturing MEMS sensors. [Background technology]

[0002] MEMS (Micro Electro Mechanical System) sensors manufactured using semiconductor microfabrication technology are known. For example, Patent Document 1 discloses a capacitance-type MEMS acceleration sensor as an example of a MEMS sensor. The capacitance-type MEMS acceleration sensor includes fixed and movable electrodes that are interdigitated with each other and formed on a semiconductor substrate, and is configured to detect acceleration by detecting a change in capacitance between the fixed and movable electrodes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-88083 Summary of the Invention [Problem to be solved by the invention]

[0004] In MEMS sensors such as a capacitive MEMS acceleration sensor having a fixed electrode and a movable electrode, a sensor element having a fixed electrode and a movable electrode is formed on the surface of a first substrate, a second substrate is bonded to the first substrate so as to cover the sensor element, and electrical signals from the electrodes of the sensor element are extracted from the second substrate.

[0005] In this case, it is conceivable that the electrode of the sensor element formed on the surface of the first substrate is electrically insulated from the support portion supporting the electrode by an element isolation portion, the electrode of the sensor element is connected to wiring arranged on the element isolation portion via a contact, the wiring formed on the first substrate is joined to a joint portion formed on the second substrate, and the electrical signal of the electrode of the sensor element is extracted from the second substrate.

[0006] However, in a MEMS sensor formed in this manner, wiring and contacts for extracting electrical signals from the electrodes of the sensor element are required on the first substrate, which complicates the manufacturing process, and simplifies the manufacturing process. Also, it is desirable to improve the sensitivity of the MEMS sensor.

[0007] An object of the present disclosure is to provide a MEMS sensor and a method for manufacturing a MEMS sensor that can improve sensitivity while simplifying the manufacturing process. [Means for solving the problem]

[0008] The present disclosure provides a MEMS sensor comprising: a first substrate having a cavity with a portion of the cavity exposed at its surface; an electrode of a sensor element provided on the first substrate and disposed within the cavity; a support portion provided on the first substrate and supporting the electrode; an element isolation portion formed on the first substrate to cover the support portion and electrically isolate the electrode from the support portion; an epitaxial growth layer formed on the electrode and the element isolation portion of the first substrate; and a second substrate bonded to the first substrate and covering the sensor element, wherein the epitaxial growth layer has a single crystal portion disposed on the electrode and a polycrystalline portion disposed on the element isolation portion.

[0009] According to the present disclosure, the electrode of the sensor element formed on the surface of the first substrate and the epitaxial growth layer formed on the element isolation portion have a single crystal portion disposed on the electrode and a polycrystalline portion disposed on the element isolation portion. Therefore, by bonding the bonding portion of the second substrate to the polycrystalline portion, the electrode of the sensor element can be electrically connected to the bonding portion of the second substrate through the single crystal portion and the polycrystalline portion of the epitaxial growth layer. This simplifies the manufacturing process compared to forming wiring and contacts for bonding to the bonding portion of the second substrate. The single crystal portion and the polycrystalline portion can be simultaneously formed on the electrode and the element isolation portion, respectively, during the formation of the epitaxial growth layer, further simplifying the manufacturing process. Furthermore, the single crystal portion of the epitaxial growth layer formed on the electrode of the first substrate can be used as an electrode, thereby improving the sensitivity of the sensor. Therefore, the sensitivity can be improved while simplifying the manufacturing process.

[0010] The present disclosure also provides a method for manufacturing a MEMS sensor, comprising: forming an element isolation portion on a surface of a first substrate that electrically isolates an electrode of a sensor element from a support portion that supports the electrode; forming an epitaxial growth layer on the surface of the first substrate on which the element isolation portion is formed; etching the surface of the first substrate on which the epitaxial growth layer is formed to form a cavity that exposes a portion of the cavity on the surface of the first substrate; and forming the electrode of the sensor element arranged in the cavity and the support portion that supports the electrode so as to be isolated by the element isolation portion; bonding a second substrate to the first substrate so as to cover the sensor element; and forming the epitaxial growth layer so as to have a single crystal portion that is arranged on the electrode portion and a polycrystalline portion that is arranged on the element isolation portion.

[0011] According to the present disclosure, an epitaxial growth layer is formed on the surface of a first substrate on which an element isolation portion is formed, and the surface of the first substrate on which the epitaxial growth layer is formed is etched to form a cavity on the surface of the first substrate, exposing a portion of the cavity. The electrode of a sensor element disposed in the cavity is then formed so as to separate the electrode from the support portion supporting the electrode by the element isolation portion. The epitaxial growth layer is formed to have a single-crystal portion on the electrode and a polycrystalline portion on the element isolation portion. By bonding a bonding portion of a second substrate to the polycrystalline portion, the electrode of the sensor element can be electrically connected to the bonding portion of the second substrate through the single-crystal portion and polycrystalline portion of the epitaxial growth layer. This simplifies the manufacturing process compared to forming wiring and contacts for bonding to the bonding portion of the second substrate. The single-crystal portion and polycrystalline portion can be simultaneously formed on the electrode and the element isolation portion, respectively, during the formation of the epitaxial growth layer, further simplifying the manufacturing process. Furthermore, the single-crystal portion of the epitaxial growth layer formed on the electrode of the first substrate can be used as an electrode, thereby improving the sensitivity of the sensor. Therefore, the manufacturing process can be simplified while improving the sensitivity. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic plan view of a MEMS sensor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the MEMS sensor taken along line II-II in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the MEMS sensor taken along line III-III in FIG. [Figure 4] FIG. 4 is a plan view of the first substrate assembly. [Figure 5] FIG. 5 is a plan view of the second substrate assembly. [Figure 6] FIG. 6 is an enlarged view of a main part of the first substrate assembly shown in FIG. [Figure 7] FIG. 7 is a diagram illustrating a method for manufacturing the first substrate assembly. [Figure 8]FIG. 8 is a diagram illustrating a method for manufacturing the first substrate assembly. [Figure 9] FIG. 9 is a diagram illustrating a method for manufacturing the first substrate assembly. [Figure 10] FIG. 10 is a diagram illustrating a method for manufacturing the first substrate assembly. [Figure 11] FIG. 11 is a diagram illustrating a method for manufacturing the first substrate assembly. [Figure 12] FIG. 12 is a diagram illustrating a method for manufacturing the first substrate assembly. [Figure 13] FIG. 13 is a diagram illustrating a method for manufacturing the second substrate assembly. [Figure 14] FIG. 14 is a diagram illustrating a method for manufacturing the second substrate assembly. [Figure 15] FIG. 15 is a diagram illustrating a method for manufacturing the second substrate assembly. [Figure 16] FIG. 16 is a diagram illustrating a method for manufacturing the second substrate assembly. [Figure 17] FIG. 17 is a diagram illustrating a method for manufacturing the second substrate assembly. [Figure 18] FIG. 18 is an enlarged view of a main part of the MEMS sensor shown in FIG. [Figure 19] FIG. 19 is a diagram illustrating a MEMS sensor in which electrode wiring and contacts are formed on a first substrate assembly. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0014] Fig. 1 is a schematic plan view of a MEMS sensor according to an embodiment of the present disclosure. As shown in Fig. 1, the MEMS sensor 1 according to the embodiment of the present disclosure is a capacitance-type acceleration sensor, and has a capacitance-type acceleration sensor element as a sensor element 2. The MEMS sensor 1 includes a first substrate assembly 11 including a first substrate 10 having the sensor element 2, and a second substrate assembly 21 including a second substrate 20 that covers the sensor element 2 and has a pad portion 3 formed thereon for extracting electrical signals from the sensor element 2.

[0015] In the following, a predetermined direction along the surfaces of the first substrate 10 and the second substrate 20 is defined as the X direction, a direction perpendicular to the X direction is defined as the Y direction, and a thickness direction of the first substrate 10 and the second substrate 20 perpendicular to the X direction and the Y direction is defined as the Z direction. Fig. 1 shows the MEMS sensor 1 in which the first substrate 10 is joined to the upper side of the second substrate 20 in the Z direction.

[0016] The sensor element 2 has an X-axis sensor element 4 that detects acceleration acting in the X direction, and a Y-axis sensor element 5 that detects acceleration acting in the Y direction. The Y-axis sensor element 5 is disposed spaced apart from the X-axis sensor element 4 in the Y direction.

[0017] The sensor element 2 provided on the first substrate 10 is covered and sealed by the second substrate 20 when the second substrate 20 is bonded to the first substrate 10. A plurality of pad portions 3, specifically five pad portions 3, are formed on the second substrate 20 and spaced apart from each other in the Y direction. The pad portions 3 are configured to be connected to external electronic components or the like and to extract electrical signals from the sensor element 2 to the external electronic components or the like.

[0018] The Y-axis sensor element 5 has the same configuration as the X-axis sensor element 4 rotated 90 degrees in a plan view, so only the X-axis sensor element 4 will be described and a description of the Y-axis sensor element 5 will be omitted.

[0019] Fig. 2 is a cross-sectional view of the MEMS sensor taken along line II-II in Fig. 1. Fig. 3 is a cross-sectional view of the MEMS sensor taken along line III-III in Fig. 1. Fig. 4 is a plan view of a first substrate assembly. Fig. 5 is a plan view of a second substrate assembly. Fig. 6 is an enlarged view of a main part of the first substrate assembly shown in Fig. 4.

[0020] 2 to 4, the first substrate assembly 11 includes a first substrate 10 having a first main surface 10a, which is the front surface, and a second main surface 10b, which is the back surface opposite to the first main surface 10a. In a plan view, the first substrate 10 is formed in a rectangular shape that is long in the Y direction, with two sides extending parallel to the X direction and two sides extending parallel to the Y direction. The first substrate 10 is made of a conductive single-crystal silicon substrate that has been doped with impurities to give it conductivity and has a resistivity of, for example, 1 Ω·m to 5 Ω·m.

[0021] 4, the first substrate 10 has an X-axis sensor element 4 and a Y-axis sensor element 5 at its center. The first substrate 10 has cavities 12, parts of which are exposed to the first main surface 10a, corresponding to the X-axis sensor element 4 and the Y-axis sensor element 5, respectively. The cavity 12 is recessed from the first main surface 10a in a substantially rectangular parallelepiped shape in the thickness direction of the first substrate 10, and has a bottom wall portion 12a and a side wall portion 12b extending from the bottom wall portion 12a in the thickness direction of the first substrate 10. The cavity 12 is formed in at least a portion of the first substrate 10 excluding a support portion 14, which will be described later.

[0022] 2 and 3, the first substrate 10 has an electrode 13 of the X-axis sensor element 4 arranged in the cavity 12 and a support portion 14 that supports the electrode 13. The electrode 13 includes a fixed electrode 30 fixed to the first substrate 10 and a movable electrode 40 that is displaceable relative to the fixed electrode 30.

[0023] The support portion 14 is formed so as to extend in a substantially quadrangular prism shape from the bottom wall portion 12a of the cavity 12 in the thickness direction of the first substrate 10 to the first main surface 10a of the first substrate 10. The support portion 14 has a support portion 14 for the fixed electrode and a support portion 14 for the movable electrode. The fixed electrode 30 and the movable electrode 40 are each supported by the support portion 14 in a state where they are floating relative to the bottom wall portion 12a within the cavity 12. The electrode 13 and the support portion 14 are formed by a part of the first substrate 10.

[0024] An element isolation portion 15 is formed on the first substrate 10 to cover the support portion 14 and electrically isolate the electrode 13 from the support portion 14. The element isolation portion 15 has a sidewall portion 15a that extends between the electrode 13 and the support portion 14 in the thickness direction of the first substrate 10 and separates the electrode 13 from the support portion 14, and an upper wall portion 15b that extends parallel to the first main surface 10a of the first substrate 10 and is disposed on the sidewall portion 15a and the support portion 14. The sidewall portion 15a of the element isolation portion 15 extends in a substantially rectangular cylindrical shape along the periphery of the support portion 14 from the bottom wall portion 12a of the cavity 12 to the first main surface 10a of the first substrate 10 in the thickness direction of the first substrate 10, and the upper wall portion 15b of the element isolation portion 15 is formed in a rectangular shape in a plan view. The element isolation portion 15 contains silicon oxide and is formed of a polycrystalline silicon oxide film, which is an insulating film.

[0025] The electrode 13 is supported by the support portion 14 via an element isolation portion 15. The fixed electrode 30 is supported by the support portion 14 via an element isolation portion 15 for the fixed electrode, as shown in Fig. 3. The movable electrode 40 is supported by the support portion 14 via an element isolation portion 15 for the movable electrode, as shown in Fig. 2.

[0026] The first substrate 10 includes a fixed electrode 30 and a movable electrode 40 formed in a comb-like shape that interdigitate with each other as electrodes 13 of the X-axis sensor element 4. The fixed electrode 30 and the movable electrode 40 are formed to have the same thickness in the thickness direction of the first substrate 10.

[0027] 6, the fixed electrode 30 has an anchor portion 31 connected to the support portion 14, a base portion 32 connected to the anchor portion 31, and a plurality of electrode portions 33 connected to the base portion 32 and formed in a comb-like shape. The anchor portion 31, the base portion 32, and the plurality of electrode portions 33 are integrally formed by a part of the first substrate 10.

[0028] The anchor portion 31 is provided in a substantially rectangular tubular shape along the periphery of the fixed electrode support portion 14 via the element isolation portion 15, and is connected to the support portion 14 via the element isolation portion 15. The base portion 32 has a first straight portion 32a connected to the anchor portion 31 and extending linearly in the X direction, a second straight portion 32b extending linearly in the Y direction from the first straight portion 32a, and a third straight portion 32c, a fourth straight portion 32d, and a fifth straight portion 32e extending linearly from the second straight portion 32b in the X direction on the opposite side to the first straight portion 32a and spaced apart in the Y direction. The base portion 32 is supported by the support portion 14 via the element isolation portion 15 and the anchor portion 31.

[0029] The multiple electrode portions 33 extend linearly in the Y direction from the third linear portion 32c, the fourth linear portion 32d, and the fifth linear portion 32e of the base portion 32, respectively, and are formed in a comb shape at equal intervals in the X direction. The multiple electrode portions 33 extend from the fifth linear portion 32e to one side in the Y direction, extend from the fourth linear portion 32d to both sides in the Y direction, and extend from the third linear portion 32c to the other side in the Y direction.

[0030] The movable electrode 40 has an anchor portion 41 connected to the support portion 14, a spring portion 44 that is expandable and contractible in the X direction, which is the acceleration detection direction, a base portion 42 that is connected to the anchor portion 41 via the spring portion 44, and a plurality of electrode portions 43 that are connected to the base portion 42 and formed in a comb-like shape. The anchor portion 41, the spring portion 44, the base portion 42, and the plurality of electrode portions 43 are integrally formed by a part of the first substrate 10.

[0031] The anchor portion 41 is provided in a substantially rectangular cylindrical shape along the periphery of the movable electrode support portion 14 via the element isolation portion 15, and is connected to the support portion 14 via the element isolation portion 15. The spring portion 44 has a straight portion 44a connected to the anchor portion 41 and extending linearly in the X direction, and an annular portion 44b connected to the straight portion 44a and formed in a rectangular shape with the Y direction as its longitudinal direction. The spring portion 44 is configured so that the annular portion 44b can expand and contract in the X direction in response to acceleration acting in the X direction.

[0032] The base portion 42 has a first straight portion 42a connected to the spring portion 44 and extending linearly in the X direction, a second straight portion 42b extending linearly in the Y direction from the first straight portion 42a, and a third straight portion 42c and a fourth straight portion 42d extending linearly from the second straight portion 42b in the X direction on the opposite side to the first straight portion 42a and spaced apart in the Y direction.

[0033] The plurality of electrode portions 43 extend linearly in the Y direction from the third linear portion 42c and the fourth linear portion 42d of the base portion 42, respectively, and are formed in a comb shape at equal intervals in the X direction. The plurality of electrode portions 43 extend on both sides in the Y direction from the third linear portion 42c and the fourth linear portion 42d, respectively.

[0034] The multiple electrode portions 43 of the movable electrode 40 are arranged to mesh with the multiple electrode portions 33 of the fixed electrode 30 without contacting each other. The electrode portions 43 of the movable electrode 40 and the electrode portions 33 of the fixed electrode 30 are arranged opposite to each other with a gap in the X direction.

[0035] When acceleration in the X direction acts on the X-axis sensor element 4, which has the fixed electrode 30 and the movable electrode 40, the electrode portion 43 of the movable electrode 40 moves relative to the electrode portion 33 of the fixed electrode 30 in response to the acceleration, changing the distance between the electrode portion 33 and the electrode portion 43, and thereby changing the capacitance between the fixed electrode 30 and the movable electrode 40. The X-axis sensor element 4 is able to detect the acceleration by extracting the change in capacitance between the fixed electrode 30 and the movable electrode 40 as an electrical signal.

[0036] 2 and 3, an epitaxial growth layer 50 made of the same silicon material as the first substrate 10 is formed on the electrodes 13 and element isolation portions 15 of the X-axis sensor element 4 of the first substrate 10. The epitaxial growth layer 50 is formed to a predetermined thickness from the first main surface 10a of the first substrate 10. The epitaxial growth layer 50 is formed as a single crystal on the electrodes 13 and as a polycrystal on the element isolation portions 15, and has a single crystal portion 51 arranged on the electrodes 13 and a polycrystal portion (region surrounded by a dashed line) 52 arranged on the element isolation portions 15.

[0037] The epitaxial growth layer 50 has a single crystal portion 51 formed on the anchor portion 31, base portion 32 and multiple electrode portions 33 of the fixed electrode 30 in the same shape as the anchor portion 31, base portion 32 and multiple electrode portions 33 in a planar view, and a polycrystalline portion 52 formed on the element isolation portion 15 for the fixed electrode in the same shape as the element isolation portion 15 in a planar view.

[0038] The single crystal portion 51 of the epitaxial growth layer 50 formed on the fixed electrode 30 has a single crystal structure made of the same material as the fixed electrode 30, and can therefore be used as an electrode together with the fixed electrode 30. The single crystal portion 51 of the epitaxial growth layer 50 formed on the electrode portion 33 can be used as an electrode portion. The polycrystalline portion 52 of the epitaxial growth layer 50 formed on the element isolation portion 15 constitutes the terminal portion 18 for the fixed electrode that extracts an electrical signal from the fixed electrode 30.

[0039] The epitaxial growth layer 50 also has a single crystal portion 51 formed on the anchor portion 41, spring portion 44, base portion 42 and multiple electrode portions 43 of the movable electrode 40 in the same shape as the anchor portion 41, spring portion 44, base portion 42 and multiple electrode portions 43 in a planar view, and a polycrystalline portion 52 formed on the element isolation portion 15 for the movable electrode in the same shape as the element isolation portion 15 in a planar view.

[0040] The single crystal portion 51 of the epitaxial growth layer 50 formed on the movable electrode 40 has a single crystal structure made of the same material as the movable electrode 40, and can therefore be used as an electrode together with the movable electrode 40. The single crystal portion 51 of the epitaxial growth layer 50 formed on the electrode portion 43 can be used as an electrode portion. The polycrystalline portion 52 of the epitaxial growth layer 50 formed on the element isolation portion 15 constitutes the terminal portion 18 for the movable electrode that extracts an electrical signal from the electrode portion of the movable electrode 40.

[0041] The first substrate 10 also has a sealing insulating portion 16 formed on the peripheral portion of the first main surface 10a so as to surround the electrodes 13 of the sensor element 2. The sealing insulating portion 16 contains silicon oxide and is formed of a polycrystalline silicon oxide film, which is an insulating film. The first substrate 10 also has an epitaxial growth layer 50 formed on the sealing insulating portion 16. The epitaxial growth layer 50 is formed polycrystalline on the sealing insulating portion 16 and has a polycrystalline portion 53 (region surrounded by a dashed line) disposed on the sealing insulating portion 16. The polycrystalline portion 53 of the epitaxial growth layer 50 is formed in the same shape as the sealing insulating portion 16 in a plan view and constitutes a sealed portion 17 that is joined to and sealed with the second substrate 20.

[0042] 4, in the first substrate assembly 11, an element region E1 where the sensor element 2 is formed and a sealing region E2 where the sealed portion 17 is formed are respectively formed inside and outside the first boundary line L1. In the element region E1, the Y-axis sensor element 5 is formed in the same manner as the X-axis sensor element 4, rotated 90 degrees in a plan view.

[0043] 2 and 3, the second substrate assembly 21 includes a second substrate 20 having a first main surface 20a, which is the front surface, and a second main surface 20b, which is the back surface opposite to the first main surface 20a. In a plan view, the second substrate 20 is formed into a rectangular shape that is long in the Y direction, with two sides extending parallel to the X direction and two sides extending parallel to the Y direction, and is longer in the X direction than the first substrate 10. The second substrate 20 is made of a conductive single-crystal silicon substrate that has been doped with impurities to give it conductivity and has a resistivity of, for example, 1 Ω·m to 5 Ω·m.

[0044] The second substrate 20 is bonded to the first substrate 10 so as to cover the X-axis sensor element 4 and the Y-axis sensor element 5. As shown in Fig. 5, the second substrate 20 is formed with bonding portions 22 bonded to the electrode terminal portions 18 formed on the first substrate 10, pad portions 3 for extracting electrical signals from the electrodes 13, wiring 23 electrically connecting the bonding portions 22 and the pad portions 3, and a sealing portion 24 bonded to and sealing the sealed portion 17 formed on the first substrate 10.

[0045] The sealing portion 24 is formed in a ring shape in plan view corresponding to the sealed portion 17 of the first substrate 10. The bonding portion 22 is formed inside the sealing portion 24, and the pad portion 3 is formed outside the sealing portion 24. The wiring 23 includes four wirings 23 that electrically connect the bonding portion 22 and the pad portion 3 to extract electrical signals from the X-axis sensor element 4 and the Y-axis sensor element 5, respectively, and one wiring 23 that electrically connects the sealing portion 24 and the pad portion 3 to ground the first substrate 10.

[0046] As shown in FIG. 2, a first insulating film 81 is formed on the first main surface 20a of the second substrate 20. The first insulating film 81 is formed of a silicon oxide film, which is a thermally oxidized film. Wiring 23 that electrically connects the bonding portion 22 and the pad portion 3 is formed on the first insulating film 81. The wiring 23 is formed on a barrier layer formed on the first insulating film 81. The wiring 23 is formed of an AlCu layer that is an alloy of Al and Cu. The barrier layer is formed of a Ti / TiN layer in which a Ti layer and a TiN layer formed on the Ti layer are stacked.

[0047] A second insulating film 83 is formed on the second substrate 20 so as to cover the wiring 23. The second insulating film 83 is formed of a silicon oxide film. Contact holes are formed in the second insulating film 83 at positions corresponding to the bonding portion 22, the pad portion 3, and the sealing portion 24, and the contact holes are filled with tungsten to form contacts 25.

[0048] In the second substrate 20, a bonding portion 22, a pad portion 3, and a sealing portion 24 are formed on a second insulating film 83. The bonding portion 22 and the pad portion 3 are formed in a quadrangular shape in a plan view, and the sealing portion 24 is formed in a rectangular ring shape in a plan view. The bonding portion 22, the pad portion 3, and the sealing portion 24 are each formed on an adhesion layer 84 formed on the second insulating film 83.

[0049] The pad portion 3 is formed of an AlCu layer, which is an alloy of Al and Cu. The bonding portion 22 is formed of an AlGe layer, which is formed by laminating an Al layer and a Ge layer formed on the Al layer. The sealing portion 24 is formed of an AlGe layer, which is formed by laminating an Al layer and a Ge layer formed on the Al layer. The adhesion layer 84 is formed of a Ti / TiN layer, which is formed by laminating a Ti layer and a TiN layer formed on the Ti layer.

[0050] 2 and 3, the bonding portions 22 formed on the second substrate 20 are bonded to the terminal portions 18, which are polycrystalline portions 52 of the epitaxial growth layer 50 formed on the first substrate 10. The terminal portions 18 for the fixed electrode and the movable electrode are bonded to the bonding portions 22 for the fixed electrode and the movable electrode, respectively.

[0051] 2 and 3, the sealing portion 24 formed on the second substrate 20 is bonded to the sealed portion 17, which is the polycrystalline portion 53 of the epitaxial growth layer 50 formed on the first substrate 10. As a result, the X-axis sensor element 4 and the Y-axis sensor element 5 provided on the first substrate 10 are covered and sealed by the second substrate 20.

[0052] 5, in the second substrate assembly 21, the element region E1 where the bonding portion 22 is formed and the seal region E2 where the seal portion 24 is formed are formed on the inside and outside of the second boundary line L2, respectively. The pad region E3 where the pad portion 3 is formed and the seal region E2 are formed on one side and the other side in the X direction of the third boundary line L3, respectively. On the second substrate 20, the bonding portion 22 and the pad portion 3 for the Y-axis sensor element 5 are formed in the same manner as the bonding portion 22 and the pad portion 3 for the X-axis sensor element 4.

[0053] In the MEMS sensor 1 thus formed, the electrode portions 33, 43 of the fixed electrode 30 and the movable electrode 40 of the X-axis sensor element 4 are electrically connected to the pad portion 3, respectively, and the change in capacitance between the electrode portions 33, 43 of the fixed electrode 30 and the movable electrode 40 is extracted as an electrical signal to detect acceleration in the X direction. The MEMS sensor 1 is also configured to detect acceleration in the Y direction by the Y-axis sensor element 5, which is configured similarly to the X-axis sensor element 4.

[0054] Next, a method for manufacturing the MEMS sensor 1 thus formed will be described.

[0055] 7 to 12 are diagrams illustrating a method for manufacturing a first substrate assembly. In manufacturing a first substrate assembly 11, first, as shown in Fig. 7, a first substrate 10, which is a single-crystal conductive silicon substrate, is prepared, and the entire first main surface 10a of the first substrate 10 is thermally oxidized by thermal oxidation to form a silicon oxide film, which is a thermally oxidized film, on the first main surface 10a of the first substrate 10. Next, the silicon oxide film is patterned by photolithography and etching to open portions of the silicon oxide film that correspond to the sidewall portions 15a of the element isolation portion 15.

[0056] Then, using the silicon oxide film as a mask, anisotropic etching is performed to remove the portion of the first main surface 10a of the first substrate 10 that corresponds to the side wall portion 15a of the element isolation portion 15, thereby forming a trench 61 that corresponds to the side wall portion 15a of the element isolation portion 15.

[0057] After the trenches 61 are formed, the silicon oxide film formed on the first main surface 10a of the first substrate 10 is removed by etching. Then, the entire first main surface 10a of the first substrate 10, including the inner surfaces of the trenches 61, is thermally oxidized by thermal oxidation, and a silicon oxide film 71, which is a thermal oxide film, is formed on the entire first main surface 10a of the first substrate 10, including the inner surfaces of the trenches 61.

[0058] 8, the silicon oxide film 71 is patterned by photolithography and etching to form the element isolation portion 15 and the sealing insulating portion 16. The element isolation portion 15 and the sealing insulating portion 16 are formed of a polycrystalline silicon oxide film.

[0059] 9, an epitaxial growth layer 50 is formed on the first main surface 10a of the first substrate 10 by epitaxial growth using a CVD (Chemical Vapor Deposition) method using a silicon material so as to completely cover the element isolation portion 15 and the sealing insulator 16. The epitaxial growth layer 50 is formed as a single crystal on the first main surface 10a of the first substrate 10, which is single crystal, and as a polycrystal on the element isolation portion 15 and the sealing insulator 16 formed of the silicon oxide film 71, so as to have a single crystal portion 51 formed as a single crystal and polycrystal portions 52, 53 formed as a polycrystal. After the formation of the epitaxial growth layer 50, it is planarized by a CMP (Chemical Mechanical Polish) process.

[0060] 10, a silicon oxide film 72 is formed as an insulating film on the epitaxial growth layer 50 by a CVD method. Then, the first main surface 10a of the first substrate 10 and the epitaxial growth layer 50 are patterned by photolithography and anisotropic etching, and trenches 62 are formed so as to leave the shape of the electrode 13. The shape of the electrode 13 is formed on the first main surface 10a of the first substrate 10, and the trenches 62 are also formed in the epitaxial growth layer 50 so as to form portions corresponding to the shape of the electrode 13.

[0061] 11 , a silicon oxide film is formed as a protective film by CVD on the entire surface of first substrate 10, including the entire inner surface of trench 62 and on which epitaxial growth layer 50 is formed. Then, the protective film is removed by etch-back except for protective film 73 formed on the side surface of trench 62, and protective film 73 is formed only on the side surface of trench 62.

[0062] 12, using the silicon oxide film 72 formed on the epitaxial growth layer 50 as a mask, the bottom portion of the trench 62 is removed by etching, specifically anisotropic etching, to form the trench 62 deeper so that the bottom of the trench 62 is deeper than the protective film 73. An exposed space is formed at the bottom of the trench 62 below the protective film 73, where the crystal plane of the first substrate 10 is exposed.

[0063] Following the anisotropic etching, reactive ions and etching gas are supplied to the exposed spaces of the trenches 62 by isotropic etching, and etching is performed in the thickness direction of the first substrate 10 starting from each exposed space by the action of the reactive ions, etc., while also performing etching in a direction parallel to the first main surface 10a of the first substrate 10. As a result, all of the adjacent exposed spaces are integrated, forming a cavity 12 in which a portion of the cavity 12 is exposed on the surface of the first substrate 10, and the electrode 13 is disposed in a floating state within the cavity 12. After the isotropic etching, the silicon oxide film 72 and protective film 73 formed on the epitaxial growth layer 50 are removed, and the first substrate assembly 11 is manufactured.

[0064] In this way, the electrode 13 of the sensor element 4 to be placed in the cavity 12 and the support portion 14 that supports the electrode 13 are provided on the first substrate 10 having the cavity 12 with part of the cavity 12 exposed on the surface. The first substrate 10 is formed with an element isolation portion 15 that electrically isolates the electrode 13 from the support portion 14 so as to cover the support portion 14, and an epitaxial growth layer 50 is formed on the electrode 13 and the element isolation portion 15 so as to have a single crystal portion 51 placed on the electrode 13 and a polycrystalline portion 52 placed on the element isolation portion 15. The epitaxial growth layer 50 is formed so as to have a polycrystalline portion 53 also on the sealing insulating portion 16.

[0065] 13 to 17 are diagrams illustrating a method for manufacturing a second substrate assembly. In manufacturing a second substrate assembly 21, first, as shown in Fig. 13, a second substrate 20, which is a single-crystal conductive silicon substrate, is prepared, and the entire first main surface 20a of the second substrate 20 is thermally oxidized by thermal oxidation, so that a silicon oxide film, which is a thermally oxidized film, is formed as a first insulating film 81 on the first main surface 20a of the second substrate 20.

[0066] Next, a barrier layer is formed on the first insulating film 81 by a PVD (Physical Vapor Deposition) method, and a wiring layer 82 is formed on the barrier layer. As the barrier layer, a Ti / TiN layer is formed by laminating a Ti layer formed on the first insulating film 81 and a TiN layer formed on the Ti layer. As the wiring layer 82, an AlCu layer, which is an alloy of Al and Cu, is formed on the barrier layer. Then, the barrier layer and wiring layer 82 are patterned by photolithography and etching, and wiring 23 is formed.

[0067] 14, a silicon oxide film is formed as a second insulating film 83 by a CVD method on the first insulating film 81 and the wiring 23 formed on the first main surface 20a of the second substrate 20. After the second insulating film 83 is formed, it is planarized by a CMP process.

[0068] 15, contact holes for wiring are formed in the second insulating film 83 by photolithography and etching. The contact holes for wiring are formed at positions corresponding to the bonding portions 22, the pad portions 3, and the sealing portions 24. Thereafter, the contact holes are filled with tungsten by a tungsten selective CVD method, thereby forming contacts 25.

[0069] After the contact 25 is formed, an adhesion layer 84 is formed by PVD on the second insulating film 83, and a pad layer 85 is formed on the adhesion layer 84. As the adhesion layer 84, a Ti / TiN layer is formed in which a Ti layer formed on the second insulating film 83 and a TiN layer formed on the Ti layer are stacked. As the pad layer 85, an AlCu layer, which is an alloy of Al and Cu, is formed on the adhesion layer 84.

[0070] Then, the adhesion layer 84 and the pad layer 85 are patterned by photolithography and etching to form the pad portion 3, and the adhesion layer 84 and the pad layer 85 are formed so as to retain the shapes of the portions corresponding to the joint portion 22 and the seal portion 24.

[0071] 16, a resist pattern 86 is formed by photolithography so as to cover the pad portion 3. Then, using the resist pattern 86 as a mask, portions of the pad layer 85 corresponding to the bonding portion 22 and the sealing portion 24 are removed by wet etching. Thereafter, the resist pattern 86 is removed.

[0072] 17, a bonding portion and sealing portion layer 87 is formed by PVD on portions of the adhesion layer 84 that correspond to the bonding portion 22 and the sealing portion 24. The bonding portion and sealing portion layer 87 is also formed on the second insulating film 83 and the pad portion 3 formed on the first main surface 20a of the second substrate 20. As the bonding portion and sealing portion layer 87, an AlGe layer is formed in which an Al layer and a Ge layer formed on the Al layer are stacked.

[0073] After forming the bonding and sealing portion layer 87, the bonding and sealing portion layer 87 is patterned by photolithography and etching to form the bonding portion 22 and the sealing portion 24, and the bonding and sealing portion layer 87 formed on the second insulating film 83 and the pad portion 3 is removed, thereby manufacturing the second substrate assembly 21.

[0074] In this way, the second substrate 20 is formed with a junction 22 that is joined to the polycrystalline portion 52 of the epitaxial growth layer 50, a pad portion 3 that extracts an electrical signal from the electrode 13, wiring 23 that electrically connects the junction 22 and the pad portion 3, and a sealing portion 24 that is joined to and seals the polycrystalline portion 53 of the epitaxial growth layer 50.

[0075] After manufacturing the first substrate assembly 11 and the second substrate assembly 21, the second substrate assembly 21 is bonded to the first substrate assembly 11, and the second substrate 20 is bonded to the first substrate 10 so as to cover the sensor element 2. A bonding portion 22 formed on the second substrate 20 is bonded to a terminal portion 18 made of a polycrystalline portion 52 of the epitaxial growth layer 50 formed on the first substrate 10, and a sealing portion 24 formed on the second substrate 20 is bonded to a sealed portion 17 made of a polycrystalline portion 53 of the epitaxial growth layer 50 formed on the first substrate 10.

[0076] The first substrate assembly 11 and the second substrate assembly 21 are bonded together by stacking the first substrate assembly 11 and the second substrate assembly 21 and heating them to a predetermined temperature, such as 440 to 450 degrees Celsius, while applying a predetermined pressure. As a result, AlGe undergoes a eutectic reaction in the AlGe layer that forms the bonding portion 22 and the sealing portion 24, and AlGeSi undergoes a eutectic reaction at the bonding surface between the bonding portion 22 and the polycrystalline portion 52 of the epitaxial growth layer 50 and at the bonding surface between the sealing portion 24 and the polycrystalline portion 53 of the epitaxial growth layer 50, thereby eutectic bonding the bonding portion 22 and the sealing portion 24 to the polycrystalline portions 52 and 53 of the epitaxial growth layer 50, respectively, via the AlGe layer.

[0077] Thereafter, the portion of the second substrate assembly 21, which is an extension of the first substrate assembly 11, facing the pad region E3 is removed by dicing along cutting lines L4 shown in FIG. 12, and the MEMS sensor 1 is manufactured.

[0078] In manufacturing the MEMS sensor 1, an element isolation section 15 is formed on the surface of the first substrate 10 to electrically isolate the electrode 13 of the sensor element 4 from the support section 14 that supports the electrode 13, an epitaxial growth layer 50 is formed on the surface of the first substrate 10 on which the element isolation section 15 is formed, the surface of the first substrate 10 on which the epitaxial growth layer 50 is formed is etched to form a cavity 12 on the surface of the first substrate 10, exposing a portion of the cavity 12, and the electrode 13 and the support section 14 are formed so that the electrode 13 of the sensor element 4 arranged in the cavity 12 and the support section 14 that supports the electrode 13 are separated by the element isolation section 15, a bonding section 22 is formed on the second substrate 20 to be bonded to the polycrystalline section 52 of the epitaxial growth layer 50 formed on the first substrate 10, and the second substrate 20 is bonded to the first substrate 10 so as to cover the sensor element 4. The epitaxially grown layer 50 is formed to have a single crystal portion 51 disposed on the electrode 13 and a polycrystalline portion 52 disposed on the element isolation portion 15 .

[0079] Fig. 18 is an enlarged view of a main part of the MEMS sensor shown in Fig. 2. As shown in Fig. 18, in the MEMS sensor 1 according to this embodiment, the electrode 13 and the support portion 14 of the sensor element 4 are provided on the first substrate 10, and the first substrate 10 is formed with an element isolation portion 15 that covers the support portion 14 and electrically isolates the electrode 13 from the support portion 14, and an epitaxial growth layer 50 having a single crystal portion 51 arranged on the electrode 13 and a polycrystalline portion 52 arranged on the element isolation portion 15 is formed.

[0080] The second substrate 20 is formed with a junction 22 that is joined to the polycrystalline portion 52 of the epitaxial growth layer 50, a pad portion 3 that extracts an electrical signal from the electrode 13 of the sensor element 4, and wiring 23 that electrically connects the junction 22 and the pad portion 3.

[0081] Then, the second substrate 20 is bonded to the first substrate 10 so as to cover the sensor element 4, and the bonding portion 22 formed on the second substrate 20 is bonded to the polycrystalline portion 52 of the epitaxial growth layer 50 formed on the first substrate 10. As a result, an electrical signal of the sensor element 4 is extracted from the electrode of the sensor element 4 including the single crystal portion 51 of the epitaxial growth layer 50 to the pad portion 3 through the polycrystalline portion 52 of the epitaxial growth layer 50 formed on the element isolation portion 15, the bonding portion 22 formed on the second substrate 20, the contact 25, and the wiring 23.

[0082] 19 is an explanatory diagram illustrating a MEMS sensor in which electrode wiring and contacts are formed on a first substrate assembly. The MEMS sensor 100 shown in FIG. 19 has electrode wiring 101 and contacts 102 formed thereon. The MEMS sensor 100 is configured such that the electrode 13 of the sensor element formed on the surface of the first substrate 10 is electrically insulated from the support portion 14 supporting the electrode 13 by an element isolation portion 15, the electrode 13 is connected to the wiring 101 disposed on the element isolation portion 15 via the contact 102, the wiring 101 formed on the first substrate 10 is joined to a joint portion 22 formed on the second substrate 20, and an electrical signal from the electrode 13 is extracted from the second substrate 20. In manufacturing the MEMS sensor 100, the element isolation portion 15 is formed, followed by the formation of the contact 102 and the wiring 101, and then the formation of the insulating portion 103 surrounding the wiring 101.

[0083] In the MEMS sensor 1 according to this embodiment, an epitaxial growth layer 50 is formed on the electrode 13 and the element isolation portion 15 of the first substrate 10, and the polycrystalline portion 52 of the epitaxial growth layer 50 is joined to the joint 22 formed on the second substrate 20. This simplifies the manufacturing process compared to a MEMS sensor in which wiring and contacts for the electrode are formed on the first substrate 10 and the wiring is joined to the joint formed on the second substrate 20. Furthermore, the single crystal portion 51 of the epitaxial growth layer 50 formed on the electrode 13 of the first substrate 10 can be used as an electrode, thereby improving the sensitivity of the sensor.

[0084] In the above-described embodiment, the fixed electrode 30 may be configured so that the base portion 32 is supported by the support portion 14 via the element isolation portion 15 without providing the anchor portion 31. Also, the movable electrode 40 may be configured so that the base portion 42 is supported by the support portion 14 via the spring portion 44 without providing the anchor portion 41. In this embodiment, the epitaxial growth layer 50 is formed on the fixed electrode 30 and the movable electrode 40, but it is also possible to form the epitaxial growth layer 50 on one of the movable electrode 40 and the fixed electrode 30.

[0085] As such, the MEMS sensor 1 of this embodiment comprises a first substrate 10 having a cavity 12 with a portion of the cavity 12 exposed on its surface 10a, an electrode 13 of a sensor element 4 provided on the first substrate 10 and arranged within the cavity 12, a support portion 14 provided on the first substrate 10 and supporting the electrode 13, an element isolation portion 15 formed on the first substrate 10 to cover the support portion 14 and electrically isolate the electrode 13 from the support portion 14, an epitaxial growth layer 50 formed on the electrode 13 and the element isolation portion 15 of the first substrate 10, and a second substrate 20 joined to the first substrate 10 and covering the sensor element 4, and the epitaxial growth layer 50 has a single crystal portion 51 arranged on the electrode 13 and a polycrystalline portion 52 arranged on the element isolation portion 15.

[0086] As a result, the epitaxial growth layer 50 formed on the electrode 13 and the element isolation portion 15 of the sensor element 4 formed on the surface 10a of the first substrate 10 has a single crystal portion 51 arranged on the electrode 13 and a polycrystalline portion 52 arranged on the element isolation portion 15. Therefore, by bonding the bonding portion 22 of the second substrate 20 to the polycrystalline portion 52, the electrode 13 of the sensor element 4 can be electrically connected to the bonding portion 22 of the second substrate 20 through the single crystal portion 51 and the polycrystalline portion 52 of the epitaxial growth layer 50. This simplifies the manufacturing process compared to the case where a contact and wiring are formed for bonding to the bonding portion 22 of the second substrate 20. The single crystal portion 51 and the polycrystalline portion 52 can be simultaneously formed on the electrode 13 and the element isolation portion 15, respectively, during the formation of the epitaxial growth layer 50, further simplifying the manufacturing process. Furthermore, the single crystal portion 51 of the epitaxial growth layer 50 formed on the electrode 13 of the first substrate 10 can be used as an electrode, thereby improving the sensitivity of the MEMS sensor 1. Therefore, the manufacturing process can be simplified while improving the sensitivity.

[0087] Furthermore, the element isolation section 15 has a sidewall section 15a that extends in the thickness direction of the first substrate 10 and separates the electrode 13 from the support section 14, and an upper wall section 15b that extends parallel to the surface 10a of the first substrate 10 and is disposed above the sidewall section 15a and the support section 14. This allows the support section 14 inside the element isolation section 15 to be electrically separated from the electrode 13 outside the element isolation section 15, making element isolation relatively easy.

[0088] Furthermore, the epitaxial growth layer 50 is formed from the same material as the first substrate 10. This allows the single crystal portion 51 and the polycrystalline portion 52 to be formed simultaneously on the electrode 13 and the element isolation portion 15, respectively, when the epitaxial growth layer 50 is formed, thereby simplifying the manufacturing process compared to when the single crystal portion 51 and the polycrystalline portion 52 are formed separately.

[0089] Furthermore, the first substrate 10 is a single-crystal silicon substrate, and the element isolation portion 15 has silicon oxide. This allows element isolation to be performed relatively easily by forming trenches 61 corresponding to the element isolation portion 15 in the first substrate 10, which is a single-crystal silicon substrate, and forming a silicon oxide film such as a thermal oxide film so as to fill the trenches 61.

[0090] The electrode 13 also has base portions 32, 42 supported by the support portion 14 and comb-shaped electrode portions 33, 43. This allows the single crystal portion 51 of the epitaxial growth layer 50 formed on the electrode 13 to be used as the electrode portion, and the size of the electrode portion can be increased to improve sensitivity.

[0091] The electrode 13 is at least one of the movable electrode 40 and the fixed electrode 30 of the sensor element 4. This allows the single crystal portion 51 of the epitaxial growth layer 50 formed on at least one of the movable electrode 40 and the fixed electrode 30 to be used as an electrode.

[0092] The sensor element 4 is a capacitance type acceleration sensor element, which simplifies the manufacturing process and improves the sensitivity of the MEMS sensor 1 having the capacitance type acceleration sensor element.

[0093] Furthermore, the second substrate 20 has formed thereon a bonding portion 22 that is bonded to the polycrystalline portion 52 of the epitaxial growth layer 50 located on the element isolation portion 15, and the bonding portion 22 is formed of an AlGe layer. By bonding the bonding portion 22 formed of the AlGe layer on the second substrate 20 to the polycrystalline portion 52 of the epitaxial growth layer 50 formed on the first substrate 10, the electrode 13 of the sensor element 4 can be electrically connected to the bonding portion 22 of the second substrate 20 through the single crystal portion 51 and polycrystalline portion 52 of the epitaxial growth layer 50. Because the bonding portion 22 formed of the AlGe layer is bonded to the polycrystalline portion 52 of the epitaxial growth layer 50, AlGe can be diffused into the polycrystalline portion 52 of the epitaxial growth layer 50 to bond the polycrystalline portion 52, thereby achieving better bonding, compared to bonding to the single crystal portion 51 of the epitaxial growth layer 50.

[0094] In addition, the second substrate 20 is formed with a pad portion 3 that extracts an electrical signal from the electrode 13, and wiring 23 that electrically connects the joint portion 22 and the pad portion 3. This allows electrical connection from the joint portion 22 of the second substrate 20 to the pad portion 3 through the wiring 23, and allows electrical connection from the electrode 13 provided on the first substrate 10 to the pad portion 3 of the second substrate 20.

[0095] Furthermore, the MEMS sensor 1 has a sealing insulator 16 formed on the first substrate 10 so as to surround the electrode 13, and the epitaxial growth layer 50 has a polycrystalline portion 53 disposed on the sealing insulator 16. This allows the sensor element 2 to be hermetically sealed by joining the sealing portion 24 formed on the second substrate 20 to the polycrystalline portion 53 of the epitaxial growth layer 50 on the sealing insulator 16. When the epitaxial growth layer 50 is formed, the polycrystalline portions 52, 53 can be formed on the element isolation portion 15 and the sealing insulator 16 simultaneously, simplifying the manufacturing process.

[0096] Furthermore, a sealing portion 24 is formed on the second substrate 20, the sealing portion 24 being bonded to the polycrystalline portion 53 of the epitaxial growth layer 50 on the sealing insulating portion 16, and the sealing portion 24 is formed of an AlGe layer. As a result, the sealing portion 24 formed of the AlGe layer on the second substrate 20 side is bonded to the polycrystalline portion 53 of the epitaxial growth layer 50 on the sealing insulating portion 16, and thus AlGe can be diffused into the polycrystalline portion 53 of the epitaxial growth layer 50 to achieve good bonding.

[0097] In addition, the manufacturing method of the MEMS sensor 1 according to this embodiment includes forming an element isolation portion 15 on the surface 10a of the first substrate 10 to electrically isolate the electrode 13 of the sensor element 4 from the support portion 14 that supports the electrode 13, forming an epitaxial growth layer 50 on the surface 10a of the first substrate 10 on which the element isolation portion 15 is formed, etching the surface 10a of the first substrate 10 on which the epitaxial growth layer 50 is formed to form a cavity 12 on the surface 10a of the first substrate 10, exposing a portion of the cavity 12, and forming the electrode 13 and the support portion 14 so as to isolate the electrode 13 of the sensor element 4 arranged in the cavity 12 from the support portion 14 that supports the electrode 13 by the element isolation portion 15, bonding a second substrate 20 to the first substrate 10 so as to cover the sensor element 4, and forming the epitaxial growth layer 50 to have a single crystal portion 51 arranged on the electrode 13 and a polycrystalline portion 52 arranged on the element isolation portion 15.

[0098] As a result, an epitaxial growth layer 50 is formed on the surface 10a of the first substrate 10 on which the element isolation portion 15 is formed, and the surface 10a of the first substrate 10 on which the epitaxial growth layer 50 is formed is etched to form a cavity 12 on the surface 10a of the first substrate 10, exposing a portion of the cavity 12, and the electrode 13 and the support portion 14 are formed so that the electrode 13 of the sensor element 4 arranged in the cavity 12 and the support portion 14 that supports the electrode 13 are separated by the element isolation portion 15. The epitaxial growth layer 50 is formed to have a single crystal portion 51 disposed on the electrode 13 and a polycrystalline portion 52 disposed on the element isolation region 15. By bonding the bonding region 22 of the second substrate 20 to the polycrystalline portion 52, the electrode 13 of the sensor element 4 can be electrically connected to the bonding region 22 of the second substrate 20 through the single crystal portion 51 and polycrystalline portion 52 of the epitaxial growth layer 50. This simplifies the manufacturing process compared to forming contacts and wiring for bonding to the bonding region 22 of the second substrate 20. The single crystal portion 51 and polycrystalline portion 52 can be simultaneously formed on the electrode 13 and the element isolation region 15, respectively, during the formation of the epitaxial growth layer 50, further simplifying the manufacturing process. Furthermore, the single crystal portion 51 of the epitaxial growth layer 50 formed on the electrode 13 of the first substrate 10 can be used as an electrode, thereby improving the sensitivity of the MEMS sensor 1. This improves sensitivity while simplifying the manufacturing process.

[0099] Furthermore, the element isolation section 15 has a sidewall section 15a that extends in the thickness direction of the first substrate 10 and separates the electrode 13 from the support section 14, and an upper wall section 15b that extends parallel to the surface 10a of the first substrate 10 and is disposed above the sidewall section 15a and the support section 14. This allows the support section 14 inside the element isolation section 15 to be electrically separated from the electrode 13 outside the element isolation section 15, making element isolation relatively easy.

[0100] Furthermore, the first substrate 10 is a single-crystal silicon substrate, and the element isolation portion 15 has silicon oxide. This allows element isolation to be performed relatively easily by forming trenches 61 corresponding to the element isolation portion 15 in the first substrate 10, which is a single-crystal silicon substrate, and forming a silicon oxide film such as a thermal oxide film so as to fill the trenches 61.

[0101] Furthermore, the second substrate 20 is formed with a bonding portion 22 that is bonded to the polycrystalline portion 52 of the epitaxial growth layer 50 located on the element isolation portion 15, and the bonding portion 22 is formed of an AlGe layer. By bonding the bonding portion 22 formed of the AlGe layer of the second substrate 20 to the polycrystalline portion 52 of the epitaxial growth layer 50 formed on the first substrate 10, the electrode 13 of the sensor element 4 can be electrically connected to the bonding portion 22 of the second substrate 20 through the single crystal portion 51 and polycrystalline portion 52 of the epitaxial growth layer 50. Because the bonding portion 22 formed of the AlGe layer is bonded to the polycrystalline portion 52 of the epitaxial growth layer 50, AlGe can be diffused into the polycrystalline portion 52 of the epitaxial growth layer 50 to bond the polycrystalline portion 52, thereby achieving better bonding, compared to bonding to the single crystal portion 51 of the epitaxial growth layer 50.

[0102] Furthermore, a sealing insulator 16 is formed on the first substrate 10 so as to surround the electrode 13, and the epitaxial growth layer 50 is formed to have a polycrystalline portion 53 disposed on the sealing insulator 16. This allows the sensor element 2 to be hermetically sealed by joining the sealing portion 24 formed on the second substrate 20 to the polycrystalline portion 53 of the epitaxial growth layer 50 on the sealing insulator 16. When the epitaxial growth layer 50 is formed, the polycrystalline portions 52, 53 can be formed on the element isolation portion 15 and the sealing insulator 16 simultaneously, simplifying the manufacturing process.

[0103] Furthermore, the second substrate 20 is provided with a sealing portion 24 that is bonded to the polycrystalline portion 53 of the epitaxial growth layer 50 on the sealing insulating portion 16, and the sealing portion 24 is formed of an AlGe layer. As a result, the sealing portion 24 formed of the AlGe layer on the second substrate 20 side is bonded to the polycrystalline portion 53 of the epitaxial growth layer 50 on the sealing insulating portion 16, so that AlGe is diffused into the polycrystalline portion 53 of the epitaxial growth layer 50 to achieve good bonding, thereby enabling the sensor element 2 to be tightly sealed.

[0104] In this embodiment, a capacitance type acceleration sensor is described as the MEMS sensor 1, but the present invention can also be applied to other MEMS sensors that have sensor elements with fixed electrodes and movable electrodes formed in a mutually interlocking comb shape.

[0105] The present invention is not limited to the exemplified embodiments, and various improvements and design modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0106] 1 MEMS sensor 2, 4, 5 Sensor elements 3 Pad section 10 First board 12 Cavity 13 electrodes 14 Support part 15 Element isolation section 15a Side wall part 15b Upper wall 16 Sealing insulation part 20 Second board 22 Joint 23 Wiring 24 Seal part 30 Fixed electrode 32,42 Base 33,43 Electrode part 40 Movable electrode 50 Epitaxial growth layer 51 Single crystal section

Claims

1. a first substrate having a cavity with a portion of the cavity exposed on a surface; an electrode of a sensor element provided on the first substrate and disposed within the cavity; a support portion provided on the first substrate and supporting the electrode; an element isolation portion formed on the first substrate so as to cover the support portion and electrically isolate the electrode from the support portion; an epitaxially grown layer formed on the electrode and the element isolation portion of the first substrate; a second substrate bonded to the first substrate and covering the sensor element; the epitaxial growth layer has a single crystal portion disposed on the electrode and a polycrystalline portion disposed on the element isolation portion; MEMS sensor.

2. the element isolation portion has a sidewall portion extending in a thickness direction of the first substrate and separating the electrode and the support portion, and an upper wall portion extending parallel to a surface of the first substrate and disposed on the sidewall portion and the support portion; The MEMS sensor of claim 1 .

3. the epitaxially grown layer is formed from the same material as the first substrate; The MEMS sensor according to claim 1 or 2.

4. the first substrate is a single crystal silicon substrate; the element isolation portion includes silicon oxide. The MEMS sensor according to any one of claims 1 to 3.

5. The electrode has a base portion supported by the support portion and an electrode portion formed in a comb-teeth shape. The MEMS sensor according to any one of claims 1 to 4.

6. The electrode is at least one of a movable electrode and a fixed electrode of the sensor element. The MEMS sensor according to any one of claims 1 to 5.

7. The sensor element is a capacitance type acceleration sensor element. The MEMS sensor according to any one of claims 1 to 6.

8. a bonding portion bonded to a polycrystalline portion of the epitaxial growth layer located on the element isolation portion is formed on the second substrate; the junction is formed by an AlGe layer. The MEMS sensor according to any one of claims 1 to 7.

9. The second substrate is provided with a pad portion for extracting an electrical signal from the electrode and a wiring for electrically connecting the bonding portion and the pad portion. The MEMS sensor of claim 8 .

10. a sealing insulating portion formed on the first substrate so as to surround the electrode; the epitaxial growth layer has a polycrystalline portion disposed on the sealing insulating portion; The MEMS sensor according to any one of claims 1 to 9.

11. a sealing portion is formed on the second substrate to be bonded to the polycrystalline portion of the epitaxial growth layer on the sealing insulating portion; The sealing portion is formed of an AlGe layer. The MEMS sensor of claim 10.

12. forming an element isolation portion on the surface of the first substrate to electrically isolate an electrode of the sensor element from a support portion that supports the electrode; forming an epitaxial growth layer on the surface of the first substrate on which the element isolation portion is formed; etching the surface of the first substrate on which the epitaxial growth layer is formed to form a cavity in which a part of the cavity is exposed on the surface of the first substrate, and forming the electrode of the sensor element arranged in the cavity and the support portion that supports the electrode so as to be separated by the element isolation portion; a second substrate is bonded to the first substrate so as to cover the sensor element; the epitaxial growth layer is formed to have a single crystal portion disposed on the electrode portion and a polycrystalline portion disposed on the element isolation portion; A method for manufacturing a MEMS sensor.

13. the element isolation portion has a sidewall portion extending in a thickness direction of the first substrate and separating the electrode and the support portion, and an upper wall portion extending parallel to a surface of the first substrate and disposed on the sidewall portion and the support portion; The method for manufacturing a MEMS sensor according to claim 12.

14. the first substrate is a single crystal silicon substrate; the element isolation portion includes silicon oxide. The method for manufacturing a MEMS sensor according to claim 12 or 13.

15. forming a junction portion on the second substrate that is bonded to a polycrystalline portion of the epitaxial growth layer located on the element isolation portion formed on the first substrate; the junction is formed by an AlGe layer; A method for manufacturing a MEMS sensor according to any one of claims 12 to 14.

16. a sealing insulating portion is formed on the first substrate so as to surround the electrode; the epitaxial growth layer is formed to have a polycrystalline portion disposed on the sealing insulating portion; A method for manufacturing the MEMS sensor according to any one of claims 12 to 15.

17. forming a sealing portion on the second substrate, the sealing portion being bonded to the polycrystalline portion of the epitaxial growth layer on the sealing insulating portion; The sealing portion is formed by an AlGe layer. The method for manufacturing a MEMS sensor according to claim 16.

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