Capacitive acceleration sensor and preparation method thereof

Abstract

The invention provides a capacitive acceleration sensor and a preparation method thereof, and the method comprises the steps: sequentially forming a first metal layer, a first dielectric layer, a sacrificial layer and a structural layer on the surface of a first substrate, and bonding a second substrate with the surface of the structural layer of the first substrate, a first supporting hole column penetrating through the second substrate to the first dielectric layer and a second supporting hole column penetrating through the second substrate to the first metal layer are formed on the surface of the second substrate, a strain structure is formed on the second substrate, the center of the strain structure is arranged on the second supporting hole column, and a plurality of first recesses are formed in the surface of the strain structure; the bottom of the first recess is etched to form a sacrificial hole, the sacrificial layer is released through the sacrificial hole, and a cavity is formed, so that the sensor can be formed only through one-time bonding, the controllability is high, a supporting hole column is arranged below the center of the formed strain structure, a swing beam of the strain structure can generate large capacitance change under small displacement, and the stability of the sensor is improved. And the precision of the sensor is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to a capacitive acceleration sensor and a preparation method thereof. Background Art

[0002] Acceleration sensors can be realized by micro-electromechanical systems (MEMS) manufactured on silicon wafers. MEMS force balance accelerometers that use capacitive detection and electrostatic force feedback circuits are superior to other types of acceleration sensors in terms of high sensitivity, low noise, DC response and bandwidth.

[0003] At present, capacitive acceleration sensors are generally manufactured by separately manufacturing the substrate layer, the sensing layer and the packaging layer, and bonding these three layers of wafers twice. However, this will lead to the problem that the accuracy of the manufactured sensor is difficult to control.

[0004] Therefore, how to improve the controllability of capacitive acceleration sensors during the manufacturing process while improving the accuracy of the sensors has become a technical problem that the industry urgently needs to solve. Summary of the invention

[0005] The present invention provides a capacitive acceleration sensor and a preparation method thereof, which solves the technical problem of how to improve the controllability of the capacitive acceleration sensor during the manufacturing process while improving the accuracy of the sensor.

[0006] According to a first aspect of the present invention, an embodiment of the present invention provides a method for preparing a capacitive acceleration sensor, comprising:

[0007] S1: providing a first substrate and a second substrate;

[0008] S2: forming a first metal layer, a first dielectric layer, a sacrificial layer and a structural layer in sequence on the surface of the first substrate;

[0009] S3: bonding the second substrate to the surface of the structure layer of the first substrate;

[0010] S4: forming a first supporting hole column on the surface of the second substrate, wherein the first supporting hole column penetrates the second substrate to the first dielectric layer;

[0011] S5: forming a second supporting hole column on the surface of the second substrate, wherein the second supporting hole column penetrates the second substrate to the first metal layer;

[0012] S6: forming a strain structure on the second substrate, wherein the center of the strain structure is arranged on the second supporting hole column, and the surface of the strain structure has a plurality of first depressions;

[0013] S7: using the sacrificial layer as an etching stop layer, etching the bottom of the first recess to form the sacrificial hole;

[0014] S8: releasing the sacrificial layer through the sacrificial hole to form a cavity.

[0015] Optionally, after bonding the second substrate to the surface of the structure layer of the first substrate and before forming a first supporting hole column on the surface of the second substrate, the method further includes:

[0016] The second substrate is thinned.

[0017] Optionally, step S4 includes:

[0018] S41: forming a first mask layer on the second substrate;

[0019] S42: performing a first patterning on the first mask layer to form a first patterned mask layer;

[0020] S43: using the first patterned mask layer as a mask and the interface between the sacrificial layer and the first dielectric layer as an etching stop layer, etching the second substrate, the structural layer, and the sacrificial layer in sequence to form a second recess;

[0021] S44: filling the second recess with a first supporting material to form the first supporting hole column.

[0022] Optionally, the method of filling the second recess with the first supporting material includes:

[0023] Silicon oxide is deposited in the second recess by using a chemical vapor deposition process, and a surface of the silicon oxide is flush with a surface of the first patterned mask layer.

[0024] Optionally, the method of filling the second recess with the first supporting material includes:

[0025] Silicon oxide material, silicon nitride material and silicon oxide material are alternately deposited into the second recess to form a composite support material, wherein a surface of the composite support material is flush with a surface of the first patterned mask layer.

[0026] Optionally, the second supporting hole column includes a second dielectric layer and a metal connection layer, and the step S5 includes:

[0027] S51: performing a second patterning on the first mask layer to form a second patterned mask layer;

[0028] S52: using the second patterned mask layer as a mask and the first metal layer as an etching stop layer, etching the second substrate, the structural layer, the sacrificial layer and the first dielectric layer to form a third recess;

[0029] S53: depositing the second dielectric layer on the sidewall of the third recess;

[0030] S54: filling the metal connection layer into the third recess so that the metal connection layer is connected to the first metal layer;

[0031] S55: removing the second patterned mask layer so that the metal connection layer is flush with the surface of the second substrate.

[0032] Optionally, the method for forming a strained structure on the second substrate includes:

[0033] S61: forming a second mask layer on the second substrate;

[0034] S62: performing a third patterning on the second mask layer to form a third patterned mask layer, wherein the third patterned mask layer pattern comprises at least one row of skeleton patterns and at least two oppositely arranged comb-shaped patterns, wherein the branch strip patterns of the row of skeleton patterns are arranged in parallel and staggered with the comb teeth of the comb-shaped patterns;

[0035] S63: using the third patterned mask layer as a mask and the structural layer as an etching stop layer, etching the second substrate to form a fourth recess;

[0036] S64: depositing a second metal layer and a third dielectric layer in sequence on the second substrate, wherein the second metal layer and the third dielectric layer cover the fourth recessed surface and cover other areas of the second substrate;

[0037] S65: removing the second metal layer and the third dielectric layer from the first region;

[0038] S66: removing the structural layer in the second area to form a strain structure, wherein the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, wherein the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam.

[0039] Optionally, after forming the strain structure and before step S7, the method further includes:

[0040] A protection layer is deposited on the second substrate, wherein the protection layer covers the fourth concave surface and covers other areas of the second substrate, so that the strain structure surface has a first concave.

[0041] Optionally, the sacrificial layer is an amorphous carbon layer, and step S8 includes:

[0042] The amorphous carbon layer is removed by oxidation, and the generated carbon dioxide gas is released through the sacrificial pores.

[0043] According to a second aspect of the present invention, an embodiment of the present invention provides a capacitive acceleration sensor, comprising:

[0044] a first substrate;

[0045] A first metal layer is formed on a surface of the first substrate;

[0046] A first dielectric layer formed on a surface of the first metal layer;

[0047] a structural layer, which is formed on the surface of the first dielectric layer through a sacrificial layer, wherein the sacrificial layer is an amorphous carbon layer;

[0048] a second substrate bonded to the structural layer of the first substrate;

[0049] A first supporting hole column, penetrating the second substrate to the first dielectric layer and surrounding the capacitive acceleration sensor;

[0050] A second supporting hole column, wherein the second supporting hole column penetrates the second substrate to the first metal layer;

[0051] A second metal layer is located on the surface of the second substrate;

[0052] a third dielectric layer formed on the second metal layer;

[0053] The second substrate, the second metal layer and the third dielectric layer constitute a strain structure, and the center of the strain structure is arranged on the second supporting hole column, and the surface of the strain structure has a plurality of first depressions, so that the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam;

[0054] The sacrificial layer is removed after the first recess is formed to form a cavity between the structural layer and the first dielectric layer.

[0055] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0056] In the capacitive acceleration sensor and preparation method thereof of the technical solution of the present invention, the method sequentially forms a first metal layer, a first dielectric layer, a sacrificial layer and a structural layer on the surface of a first substrate, bonds a second substrate to the surface of the structural layer of the first substrate, forms a first supporting hole column penetrating the second substrate to the first dielectric layer and a second supporting hole column penetrating the second substrate to the first metal layer on the surface of the second substrate, forms a strain structure on the second substrate, the center of the strain structure is arranged on the second supporting hole column, the surface of the strain structure has a plurality of first depressions, the bottom of the first depression is etched to form a sacrificial hole, the sacrificial layer is released through the sacrificial hole to form a cavity, so that the present invention only needs one bonding to form a sensor, and has high controllability. At the same time, the strain structure is of a special shape, is more sensitive to external acceleration, and has a supporting hole column under the center, which can make the swing beam produce a large capacitance change under a very small displacement, thereby improving the accuracy of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 is a schematic flow chart of a method for preparing a capacitive acceleration sensor in one embodiment of the present invention;

[0059] Figure 2 to Figure 5 FIG. 1 is a schematic diagram of a process for preparing a capacitive acceleration sensor according to an embodiment of the present invention. Figure 1 ;

[0060] Figure 6 is a schematic flow chart of a method for preparing a capacitive acceleration sensor in another embodiment of the present invention;

[0061] Figure 7 to Figure 10 FIG. 1 is a schematic diagram of a process for preparing a capacitive acceleration sensor according to an embodiment of the present invention. Figure 2 ;

[0062] Fig.11 is a schematic flow chart of a method for preparing a capacitive acceleration sensor in another embodiment of the present invention;

[0063] Figure 12 to Figure 16 FIG. 1 is a schematic diagram of a process for preparing a capacitive acceleration sensor according to an embodiment of the present invention. Figure 3 ;

[0064] Fig.17is a schematic flow chart of a method for preparing a capacitive acceleration sensor in yet another embodiment of the present invention;

[0065] Figure 18 to Figure 28 FIG. 1 is a schematic diagram of a process for preparing a capacitive acceleration sensor according to an embodiment of the present invention. Figure 4 ;

[0066] Fig.29 FIG. 4 is a top view of a capacitive acceleration sensor according to an embodiment of the present invention.

[0067] Description of reference numerals:

[0068] 101- first substrate;

[0069] 102- a first metal layer;

[0070] 103- a first dielectric layer;

[0071] 104-sacrificial layer;

[0072] 105-structural layer;

[0073] 201- second substrate;

[0074] 301-first mask layer;

[0075] 401-first depression;

[0076] 402-first supporting material;

[0077] 403-first supporting hole column;

[0078] 500-Second support hole column

[0079] 501- third depression;

[0080] 502-a second dielectric material layer;

[0081] 503- second dielectric layer;

[0082] 504-metal connection layer;

[0083] 601-second mask layer;

[0084] 701-the fourth depression;

[0085] 702- second metal layer;

[0086] 703- third dielectric layer;

[0087] 704-third mask layer;

[0088] 705- fourth mask layer;

[0089] 801-strain structure;

[0090] 8011-rib-shaped swing beam;

[0091] 8012-comb fixing beam;

[0092] 901-protective layer;

[0093] 1001 - Fixed beam lead capacitor. DETAILED DESCRIPTION

[0094] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0095] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series or unit is not necessarily limited to those or units clearly listed, but may include other or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0096] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0097] As described in the background art, it is difficult to improve the controllability of capacitive acceleration sensors during the manufacturing process while improving the accuracy of the sensors in the prior art.

[0098] To solve the above problems, please refer to Figure 1 The present invention provides a method for preparing a capacitive acceleration sensor, comprising:

[0099] S1: providing a first substrate and a second substrate;

[0100] S2: forming a first metal layer, a first dielectric layer, a sacrificial layer and a structural layer in sequence on the surface of the first substrate;

[0101] S3: bonding the second substrate to the surface of the structure layer of the first substrate;

[0102] S4: forming a first supporting hole column on the surface of the second substrate, wherein the first supporting hole column penetrates the second substrate to the first dielectric layer;

[0103] S5: forming a second supporting hole column on the surface of the second substrate, wherein the second supporting hole column penetrates the second substrate to the first metal layer;

[0104] S6: forming a strain structure on the second substrate, wherein the center of the strain structure is arranged on the second supporting hole column, and the surface of the strain structure has a plurality of first depressions;

[0105] S7: using the sacrificial layer as an etching stop layer, etching the bottom of the first recess to form the sacrificial hole;

[0106] S8: releasing the sacrificial layer through the sacrificial hole to form a cavity.

[0107] Therefore, the formation method provided by the present invention only requires one bonding to form a sensor, and has high controllability. At the same time, there is a supporting hole column under the center of the strain structure, which can make the swing beam produce a large capacitance change under a very small displacement, thereby improving the accuracy of the sensor.

[0108] Figures 2 to 28 is a schematic cross-sectional structure diagram of a capacitive acceleration sensor manufacturing process according to an embodiment of the present invention, Fig.29 It is a top view of a capacitive acceleration sensor in an embodiment of the present invention, wherein two mutually perpendicular capacitive acceleration sensors and a first supporting hole column surrounding the two capacitive acceleration sensors are shown, and the two mutually perpendicular capacitive acceleration sensors are respectively used to detect acceleration components in different directions, thereby realizing acceleration detection in a two-dimensional plane.

[0109] Please continue to refer to Fig.29 It can be seen that for a single capacitive acceleration sensor, the strain structure of the present invention includes a swinging beam in the middle and fixed beams on both sides. When the swinging beam moves or deforms, the distance between the swinging beam and the fixed beam will change, thereby changing the capacitance value between them. The capacitance value will be used for subsequent further signal processing or data acquisition.

[0110] It should be understood that the present invention does not limit the number and position of the capacitive acceleration sensors, which can be flexibly configured according to actual needs. For example, multiple capacitive acceleration sensors can be arranged in different positions and directions to achieve more comprehensive acceleration component detection.

[0111] To facilitate understanding of the structure, the cross-sectional structure schematic diagram provided by the present invention is as follows Fig.29 On this basis, please refer to Figure 1 , and combined with reference Figure 2 to Figure 28 , the preparation process of the capacitive acceleration sensor provided by the embodiment of the present invention is described.

[0112] Please refer to Figure 2 , providing a first substrate 101 and a second substrate 201.

[0113] As an example, the first substrate 101 or the second substrate 201 may be an SOI substrate, a silicon substrate, etc., and the present invention is not limited thereto. Those skilled in the art may select a suitable substrate as needed.

[0114] Please refer to Figure 3 A first metal layer 102 , a first dielectric layer 103 , a sacrificial layer 104 and a structural layer 105 are sequentially formed on the surface of the first substrate 101 .

[0115] As an example, the material of the first metal layer 102 can be a metal material with good conductivity such as Al, Au, etc., the material of the first dielectric layer 103 can be silicon oxide, silicon nitride, etc., and the structural layer 105 can be silicon oxide, etc. Technicians in this field can select appropriate materials according to specific process requirements and conditions.

[0116] In one implementation, the sacrificial layer 104 is a carbon structure layer. For example, the carbon structure layer may be an amorphous carbon layer or a graphite layer.

[0117] In the case where the carbon structure layer is an amorphous carbon layer, an amorphous carbon layer with a preset thickness may be sequentially formed on the surface of the first dielectric layer 103 by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0118] Please refer to Figure 4 , bonding the second substrate 201 to the surface of the structural layer 105 of the first substrate 101 , so that the first substrate 101 and the second substrate 201 are bonded.

[0119] In a preferred embodiment, after the first substrate 101 and the second substrate 201 are bonded, please refer to Figure 5 , the second substrate 201 is thinned.

[0120] As an example, the thickness of the second substrate 201 can be controlled at 20um to 200um. Of course, the required thickness of the second substrate 201 is related to the device capacitance value and the final sensitivity. The present invention is not limited to this, and technicians in this field can select a suitable thickness as needed.

[0121] Please continue to refer to Figure 1 , perform step S4: forming a first supporting hole column on the surface of the second substrate 201 , wherein the first supporting hole column penetrates the second substrate 201 to the first dielectric layer 103 .

[0122] In one implementation, please refer to Figure 6 , Figure 6 The flowchart of step S4 includes:

[0123] S41: forming a first mask layer on the second substrate;

[0124] S42: performing a first patterning on the first mask layer to form a first patterned mask layer;

[0125] S43: using the first patterned mask layer as a mask and the interface between the sacrificial layer and the first dielectric layer as an etching stop layer, etching the second substrate, the structural layer, and the sacrificial layer in sequence to form a second recess;

[0126] S44: filling the second recess with the supporting material to form the first supporting hole column.

[0127] Subsequent combination Figure 7 to Figure 10 Provide explanation.

[0128] Please refer to Figure 7 , forming a first mask layer 301 on the second substrate 201; and patterning the first mask layer 301 for the first time to form a first patterned mask layer.

[0129] Please refer to Figure 8 , using the first patterned mask layer as a mask and the interface between the sacrificial layer 104 and the first dielectric layer 103 as an etching stop layer, etching the second substrate 201, the structural layer 105, and the sacrificial layer 104 in sequence to form a second recess 401;

[0130] Please refer to Fig. 9 , filling the second recess 401 with a first supporting material 402 .

[0131] In one implementation, the first support material 402 may be filled into the first recess 401 by a high density plasma process (HDP), a high aspect ratio process (HARP), a flowable chemical vapor deposition process (FCVD), or the like.

[0132] In a specific implementation manner, the method of filling the first support material 402 into the first recess 401 includes:

[0133] Silicon oxide is deposited in the first recess 401 by using a chemical vapor deposition process, and the surface of the silicon oxide is flush with the surface of the first patterned mask layer.

[0134] In another specific embodiment, the method of filling the first support material 402 into the first recess 401 includes:

[0135] Silicon oxide material, silicon nitride material and silicon oxide material are alternately deposited into the first recess 401 to form a composite first supporting material, and a surface of the composite first supporting material is flush with a surface of the first patterned mask layer.

[0136] In this way, the first supporting hole column surrounds the area where the sensor is formed and is connected to the structural layer 105, so as to form a support for the subsequent formation of the fixed beam structure, thereby improving the supporting strength of the fixed beam.

[0137] As a specific implementation, in step S44, the method for forming the first supporting hole column includes:

[0138] The first mask layer 301 is used as an etching stop layer, and the first supporting material 402 on the surface of the second substrate 201 is removed by chemical mechanical polishing and planarization to form the first supporting hole column 403.

[0139] Specifically, please refer to Fig.10 , using the first mask layer 301 as an etching stop layer, the first supporting material 402 on the surface of the second substrate 201 is removed by chemical mechanical polishing and planarization treatment to form the first supporting hole column 403.

[0140] Please continue to refer to Figure 1 , execute step S5 to form a second supporting hole column on the surface of the second substrate, and the second supporting hole column penetrates the second substrate to the first metal layer.

[0141] In one embodiment, the second supporting hole column includes a second dielectric layer and a metal connection layer. In this case, please refer to Fig.11 , Fig.11 The flowchart of step S5 includes:

[0142] S51: performing a second patterning on the first mask layer to form a second patterned mask layer;

[0143] S52: using the second patterned mask layer as a mask and the first metal layer as an etching stop layer, etching the second substrate, the structural layer, the sacrificial layer and the first dielectric layer to form a third recess;

[0144] S53: depositing the second dielectric layer on the sidewall of the third recess;

[0145] S54: filling the metal connection layer into the third recess so that the metal connection layer is connected to the first metal layer;

[0146] S55: removing the second patterned mask layer so that the metal connection layer is flush with the surface of the second substrate.

[0147] In one embodiment, the method of depositing the second dielectric layer on the sidewall of the third recess in step S53 includes:

[0148] Depositing a second dielectric material layer on the second substrate, wherein the second dielectric material layer covers the third recessed surface and covers other areas of the second substrate;

[0149] The second dielectric material layer on the surface of the second substrate and the second dielectric material layer at the bottom of the third recess are etched to form the second dielectric layer.

[0150] Subsequent combination Figure 12 to Figure 16 Provide explanation.

[0151] Please refer to Fig.12 , the first mask layer 301 is patterned for a second time to form a second patterned mask layer; using the second patterned mask layer as a mask and the first metal layer 102 as an etching stop layer, the second substrate 201, the structural layer 105, the sacrificial layer 104 and the first dielectric layer 103 are etched to form the third recess 501.

[0152] Please refer to Fig.13 , depositing a second dielectric material layer 502 on the second substrate 201 , wherein the second dielectric material layer 502 covers the surface of the third recess 501 and covers other areas of the second substrate 201 .

[0153] Please refer to Fig.14 , the second dielectric material layer 502 on the surface of the second substrate 201 and the second dielectric material layer 502 at the bottom of the third recess 501 are etched to form the second dielectric layer 503 .

[0154] In a specific implementation manner, the second dielectric material layer 502 on the surface of the second substrate 201 and the second dielectric material layer 502 at the bottom of the third recess 501 are dry-etched to form the second dielectric layer 503 .

[0155] For example, the material of the second dielectric layer 503 may be silicon oxide, silicon nitride, etc., and the present invention is not limited thereto, and those skilled in the art may select a suitable material as needed.

[0156] Please refer to Fig.15 , filling the metal connection layer 504 into the third recess 501 , so that the metal connection layer 504 is connected to the first metal layer 102 .

[0157] As an example, the material of the metal connection layer 504 can be a metal layer, a doped polysilicon layer, etc. The present invention is not limited to this, and those skilled in the art can select a suitable material as needed.

[0158] Please refer to Fig.16 , remove the second patterned mask layer 301 so that the metal connection layer 504 is flush with the surface of the second substrate 201 .

[0159] Please continue to refer to Figure 1 , executing step S6: forming a strain structure on the second substrate, the center of the strain structure is set on the second supporting hole column, and the surface of the strain structure has a plurality of first depressions.

[0160] Regarding the method for forming a strained structure on the second substrate, in one embodiment, please refer to Fig.17 , Fig.17 The flowchart of step S6 includes:

[0161] S61: forming a second mask layer on the second substrate;

[0162] S62: performing a third patterning on the second mask layer to form a third patterned mask layer, wherein the third patterned mask layer pattern comprises at least one row of skeleton patterns and at least two oppositely arranged comb-shaped patterns, wherein the branch strip patterns of the row of skeleton patterns are arranged in parallel and staggered with the comb teeth of the comb-shaped patterns;

[0163] S63: using the third patterned mask layer as a mask and the structural layer as an etching stop layer, etching the second substrate to form a fourth recess;

[0164] S64: depositing a second metal layer and a third dielectric layer in sequence on the second substrate, wherein the second metal layer and the third dielectric layer cover the fourth recessed surface and cover other areas of the second substrate;

[0165] S65: removing the second metal layer and the third dielectric layer from the first region;

[0166] S66: removing the structural layer in the second area to form a strain structure, wherein the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, wherein the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam.

[0167] Subsequent combination Figure 18 to Figure 21 Provide explanation.

[0168] Please refer to Fig.18 , forming a second mask layer 601 on the second substrate 201; the second mask layer 601 is patterned for a third time to form a third patterned mask layer, the third patterned mask layer pattern includes at least one row of skeleton patterns and at least two oppositely arranged comb patterns, and the branch strip patterns of the row of skeleton patterns are parallel and staggered with the comb teeth of the comb patterns; using the third patterned mask layer as a mask and the structural layer 105 as an etching stop layer, the second substrate 201 is etched to form a fourth recess 701.

[0169] As an example, the size of the fourth recess 701 may be between 5 nm and 10 nm. Of course, the present invention is not limited to this, and the specific size depends on design requirements.

[0170] After this step, the second mask layer 601 is removed.

[0171] Please continue to refer to Fig.19 , a second metal layer 702 and a third dielectric layer 703 are sequentially deposited on the second substrate 201 , and the second metal layer 702 and the third dielectric layer 703 cover the surface of the fourth recess 701 and cover other areas of the second substrate 201 .

[0172] For example, the thickness of the second metal layer 702 may be 1 nm to 100 nm, and the thickness of the third dielectric layer 703 may be 10 nm to 1000 nm. The present invention is not limited thereto, and those skilled in the art may select a suitable thickness as needed.

[0173] In practical applications, in a specific implementation manner, the material of the third dielectric layer 703 can be silicon oxide, silicon nitride, silicon oxynitride, etc., and the present invention is not limited thereto.

[0174] On this basis, continue to execute step S66: remove the second metal layer 702 and the third dielectric layer 703 in the first area; remove the structural layer 105 in the second area to form a strain structure, the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam.

[0175] The strain structure formed can be Fig.29 As shown, in Fig.29 In the example, the strain structure 801 includes a rib-shaped swing beam 8011 and a comb-shaped fixed beam 8012, the fixed beam 8012 is located on both sides of the swing beam 8011, and the comb teeth of the fixed beam 8012 are parallel and staggered with the branches of the swing beam 8011.

[0176] Subsequent combination Figure 20 to Figure 22 Provide explanation.

[0177] Please refer to Fig. 20 , a patterned third mask layer 704 is formed on the second metal layer 703; the area outside the patterned third mask layer 704 is the first area, and the second metal layer 702 and the third dielectric layer 703 in the first area can be removed by dry etching.

[0178] The first region corresponds to the surface of the second substrate 201 other than the portion of the rib-shaped swing beam corresponding to the second supporting hole column;

[0179] Please refer to Fig.21 , a patterned fourth mask layer 705 is formed on the second substrate 201 and the retained second metal layer 703, the area outside the patterned fourth mask layer 705 corresponds to the second area, and the structural layer of the second area is removed by dry etching.

[0180] The second area corresponds to the gap between the branch bars of the rib-shaped swing beam, the gap between the comb teeth of the comb-shaped fixed beam, and the gap between the rib-shaped swing beam and the comb-shaped fixed beam, that is, corresponding to Fig.29 The white part outside the strain structure (801) is formed by removing the second metal layer 703, the third dielectric layer 702 and the structural layer in the second region; the side wall of the rib-shaped swing beam structure and the side wall of the comb-shaped fixed beam are provided with the second metal layer 703 and the third dielectric layer 702, such as Figure 25-28 shown.

[0181] Please refer to Fig. 22 , remove the third mask layer 704 and the fourth mask layer 705.

[0182] exist Fig. 22In the example, the second metal layer 702 and the third dielectric layer 703 of the portion of the rib-shaped swing beam corresponding to the second supporting hole column, the second metal layer 702 and the third dielectric layer 703 of the side wall of the rib skeleton swing beam and the side wall of the comb-shaped fixed beam are not removed. This is because the second metal layer 702 and the third dielectric layer 703 there serve as the plates of the capacitor to realize the transmission of electrical signals, and at the same time, the second metal layer 702 and the third dielectric layer 703 of the portion of the swing beam corresponding to the second supporting hole column are to achieve electrical conduction between the structural layer and the second supporting hole column.

[0183] Please continue to refer to Fig.23 , a protective layer 901 is deposited on the second substrate 201, and the protective layer 901 covers the surface of the fourth recess 701 and covers other areas of the second substrate 201, so that the surface of the strained structure has a first recess.

[0184] As an example, the material of the protective layer 901 may be a silicon nitride layer, a silicon oxide layer, or a composite layer of silicon oxide and silicon nitride, and the present invention is not limited thereto.

[0185] Please continue to refer to Fig.24 , using the sacrificial layer 104 as an etching stop layer, etching the bottom of the first recess to form the sacrificial hole.

[0186] In a specific implementation manner, the sacrificial hole may be formed by etching the bottom of the first recess by dry etching.

[0187] Please refer to Fig.25 , the sacrificial layer 104 is released through the sacrificial hole to form a cavity.

[0188] When the sacrificial layer 104 is an amorphous carbon layer, in a specific implementation manner, the step S8 includes:

[0189] The amorphous carbon layer is removed by oxidation, and the generated carbon dioxide gas is released through the sacrificial pores.

[0190] To understand the structure of other parts after the cavity is formed, please refer to Figure 26 to Figure 28 .

[0191] in, Fig.26 Shown along Fig.28 A schematic diagram of a cross-sectional structure taken along the BB' line in FIG.

[0192] Fig. 27 Shown along Fig.28 A schematic diagram of a cross-sectional structure taken along the C-C' line in FIG.

[0193] Fig.28 Shown along Fig.29 Schematic diagram of the cross-sectional structure viewed along the D-D' line.

[0194] In summary, in the preparation method of the technical solution of the present invention, a first metal layer, a first dielectric layer, a sacrificial layer and a structural layer are formed in sequence on the surface of a first substrate, and a second substrate is bonded to the surface of the structural layer of the first substrate. A first supporting hole column penetrating the second substrate to the first dielectric layer and a second supporting hole column penetrating the second substrate to the first metal layer are formed on the surface of the second substrate. A strain structure is formed on the second substrate, and the center of the strain structure is set on the second supporting hole column. The surface of the strain structure has a plurality of first depressions. The bottom of the first depression is etched to form a sacrificial hole. The sacrificial layer is released through the sacrificial hole to form a cavity, so that the present invention only needs one bonding to form a sensor, and has high controllability. At the same time, the strain structure is a comb-shaped fixed beam and a rib-shaped swinging beam interlaced with each other, which is more sensitive to external acceleration, and there is a supporting hole column under the center, which can make the swinging beam produce a large capacitance change under a very small displacement, thereby improving the accuracy of the sensor.

[0195] Accordingly, the embodiment of the present invention further provides a capacitive acceleration sensor, please continue to refer to Fig.25 ,include:

[0196] A first substrate 101;

[0197] A first metal layer 102, formed on the surface of the first substrate 101;

[0198] A first dielectric layer 103, formed on a surface of the first metal layer 102;

[0199] A structural layer 105, which is formed on the surface of the first dielectric layer 103 through a sacrificial layer 104, wherein the sacrificial layer 104 is an amorphous carbon layer;

[0200] A second substrate 201, bonded to the structural layer 105 of the first substrate 101;

[0201] A first supporting hole column 403 passes through the second substrate 201 to the first dielectric layer 103 and surrounds the capacitive acceleration sensor;

[0202] A second supporting hole column 500, wherein the second supporting hole column 500 penetrates the second substrate 201 to the first metal layer 102;

[0203] A second metal layer 702, located on the surface of the second substrate 201;

[0204] A third dielectric layer 703 is formed on the second metal layer 702;

[0205] The second substrate 201, the second metal layer 702 and the third dielectric layer 703 constitute a strain structure, and the center of the strain structure is set on the second supporting hole column 500, and the surface of the strain structure has a plurality of first depressions, so that the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam;

[0206] The sacrificial layer 104 is removed after the first recess is formed, so as to form a cavity between the structural layer 105 and the first dielectric layer 103 .

[0207] exist Fig.25 In the example, the capacitive acceleration sensor also includes a protective layer 901, which covers the surface of the strain structure and the surface of the swing beam support column structure to protect the surface of the capacitive acceleration sensor and prevent subsequent processes from causing damage to the sensor.

[0208] Please refer to Fig.29 , Fig.29 for Fig.25 Corresponding top view. In practical applications, the sensitivity of the sensor can be adjusted by adjusting the size of the swing beam; moreover, the swing beam can have one or more supporting columns, and the specific number design depends on the design requirements.

[0209] exist Fig.29 In the example, the capacitive acceleration sensor further includes a fixed beam lead capacitor 1001, and the metal wire at the bottom of the swing beam support column is another lead electrode of the capacitor.

[0210] The fixed beam lead capacitor 1001 is used as the signal output terminal of the capacitive sensor. When the swing beam moves or deforms, the distance between the swing beam and the fixed beam will change, thereby changing the capacitance value between them. The fixed beam lead capacitor 1001 will capture this change and convert it into an electrical signal, which is transmitted to the back-end electronic circuit for further signal processing or data acquisition.

[0211] It can be seen that in the capacitive acceleration sensor of the technical solution of the present invention, since only one bonding is required to form the sensor, the controllability is relatively high. At the same time, the strain structure is a comb-shaped fixed beam and a rib-shaped swinging beam interlaced with each other, which is more sensitive to external acceleration, and there is a supporting hole column under the center, which can make the swinging beam produce a larger capacitance change under a very small displacement, thereby improving the accuracy of the sensor.

[0212] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a capacitive acceleration sensor, characterized in that: include: S1: providing a first substrate and a second substrate; S2: forming a first metal layer, a first dielectric layer, a sacrificial layer and a structural layer in sequence on the surface of the first substrate; S3: bonding the second substrate to the surface of the structure layer of the first substrate; S4: forming a first supporting hole column on the surface of the second substrate, wherein the first supporting hole column penetrates the second substrate to the first dielectric layer; S5: forming a second supporting hole column on the surface of the second substrate, wherein the second supporting hole column penetrates the second substrate to the first metal layer; S6: forming a strain structure on the second substrate, wherein the center of the strain structure is arranged on the second supporting hole column, and the surface of the strain structure has a plurality of first depressions; S7: using the sacrificial layer as an etching stop layer, etching the bottom of the first recess to form the sacrificial hole; S8: releasing the sacrificial layer through the sacrificial hole to form a cavity.

2. The method for preparing a capacitive acceleration sensor according to claim 1, wherein: After bonding the second substrate to the surface of the structure layer of the first substrate and before forming a first supporting hole column on the surface of the second substrate, the method further includes: The second substrate is thinned.

3. The method for preparing a capacitive acceleration sensor according to claim 1, wherein: The step S4 comprises: S41: forming a first mask layer on the second substrate; S42: performing a first patterning on the first mask layer to form a first patterned mask layer; S43: using the first patterned mask layer as a mask and the interface between the sacrificial layer and the first dielectric layer as an etching stop layer, etching the second substrate, the structural layer, and the sacrificial layer in sequence to form a second recess; S44: filling the second recess with a first supporting material to form the first supporting hole column.

4. The method for preparing a capacitive acceleration sensor according to claim 3, wherein: The method of filling the first supporting material into the second recess comprises: Silicon oxide is deposited in the second recess by using a chemical vapor deposition process, and a surface of the silicon oxide is flush with a surface of the first patterned mask layer.

5. The method for preparing a capacitive acceleration sensor according to claim 3, characterized in that: The method of filling the first supporting material into the second recess comprises: Silicon oxide material, silicon nitride material and silicon oxide material are alternately deposited into the second recess to form a composite support material, wherein a surface of the composite support material is flush with a surface of the first patterned mask layer.

6. The method for preparing a capacitive acceleration sensor according to claim 3, characterized in that: The second supporting hole column includes a second dielectric layer and a metal connection layer, and the step S5 includes: S51: performing a second patterning on the first mask layer to form a second patterned mask layer; S52: using the second patterned mask layer as a mask and the first metal layer as an etching stop layer, etching the second substrate, the structural layer, the sacrificial layer and the first dielectric layer to form a third recess; S53: depositing the second dielectric layer on the sidewall of the third recess; S54: filling the metal connection layer into the third recess so that the metal connection layer is connected to the first metal layer; S55: removing the second patterned mask layer so that the metal connection layer is flush with the surface of the second substrate.

7. The method for preparing a capacitive acceleration sensor according to claim 1, wherein: The method for forming a strained structure on the second substrate comprises: S61: forming a second mask layer on the second substrate; S62: performing a third patterning on the second mask layer to form a third patterned mask layer, wherein the third patterned mask layer pattern comprises at least one row of skeleton patterns and at least two oppositely arranged comb-shaped patterns, wherein the branch strip patterns of the row of skeleton patterns are arranged in parallel and staggered with the comb teeth of the comb-shaped patterns; S63: using the third patterned mask layer as a mask and the structural layer as an etching stop layer, etching the second substrate to form a fourth recess; S64: depositing a second metal layer and a third dielectric layer in sequence on the second substrate, wherein the second metal layer and the third dielectric layer cover the fourth recessed surface and cover other areas of the second substrate; S65: removing the second metal layer and the third dielectric layer from the first region; S66: removing the structural layer in the second area to form a strain structure, wherein the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, wherein the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam.

8. The method for preparing a capacitive acceleration sensor according to claim 7, wherein: After forming the strain structure and before step S7, the method further includes: A protection layer is deposited on the second substrate, wherein the protection layer covers the fourth concave surface and covers other areas of the second substrate, so that the strain structure surface has a first concave.

9. The method for preparing a capacitive acceleration sensor according to claim 1, wherein: The sacrificial layer is an amorphous carbon layer, and the step S8 comprises: The amorphous carbon layer is removed by oxidation, and the generated carbon dioxide gas is released through the sacrificial holes.

10. A capacitive acceleration sensor, characterized in that: include: a first substrate; A first metal layer is formed on a surface of the first substrate; A first dielectric layer formed on a surface of the first metal layer; a structural layer, which is formed on the surface of the first dielectric layer through a sacrificial layer, wherein the sacrificial layer is an amorphous carbon layer; a second substrate bonded to the structural layer of the first substrate; A first supporting hole column, penetrating the second substrate to the first dielectric layer and surrounding the capacitive acceleration sensor; A second supporting hole column, wherein the second supporting hole column penetrates the second substrate to the first metal layer; A second metal layer is located on the surface of the second substrate; a third dielectric layer formed on the second metal layer; The second substrate, the second metal layer and the third dielectric layer constitute a strain structure, and the center of the strain structure is arranged on the second supporting hole column, and the surface of the strain structure has a plurality of first depressions, so that the strain structure includes a rib-shaped swing beam and a comb-shaped fixed beam, the fixed beam is located on both sides of the swing beam, and the comb teeth of the fixed beam are parallel and staggered with the branches of the swing beam; The sacrificial layer is removed after the first recess is formed to form a cavity between the structural layer and the first dielectric layer.

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