Comb tooth capacitance type Z-axis acceleration sensitive chip with overlapped structure and manufacturing method thereof

Abstract

The invention discloses an overlapping structure comb tooth capacitance type Z-axis acceleration sensitive chip and a manufacturing method thereof, and belongs to the technical field of MEMS sensors. The sensitive chip is formed by overlapping a comb tooth capacitor layer and an elastic beam structure layer, and the comb tooth capacitor layer and the elastic beam structure layer are bonded together through an oxide layer. In addition to the advantage of small damping coefficient, the comb capacitor has the following three advantages: 1, the structure of overlapping the comb capacitor and the elastic beam does not need to occupy extra chip area, which is beneficial to microminiaturization and can reduce chip cost at the same time; secondly, the comb capacitor and the elastic beam are overlapped, so that the elastic beam is prevented from occupying the space for distributing the comb teeth around the mass block when the comb capacitor and the elastic beam are placed in a plane, the number of the comb teeth is greatly increased, and the capacitance of the comb structure is effectively increased; and thirdly, the elastic beams can be symmetrically distributed around the mass block due to the overlapping structure, and the cross coupling influence in the X-axis direction and the Y-axis direction is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to a technical method for improving the performance of a capacitive acceleration sensitive chip and a method for manufacturing the sensitive chip, and belongs to sensor technology in the field of micro-electromechanical system (MEMS). The present invention is a sensitive chip design and a manufacturing method thereof proposed to improve the performance of a comb-tooth capacitive acceleration sensitive chip, which can effectively reduce the area of ​​the comb-tooth capacitive acceleration sensitive chip and has the advantages of high output linearity and small cross coupling. Background Art

[0002] Micro-electromechanical systems (MEMS) are a cutting-edge research field involving electronics, mechanics, physics, biomedicine and other disciplines. MEMS sensors are widely used in aerospace, medical equipment, automotive electronics, smart terminals and other fields due to their miniaturization, low cost, low power consumption, and compatibility with integrated technology and easy intelligence. MEMS sensors can be divided into many types, including accelerometers, temperature sensors, pressure sensors, sound sensors, humidity sensors and gas sensors, etc. Among them, accelerometers can be divided into capacitive, resonant, piezoelectric, piezoresistive and optical accelerometers according to their different detection methods. Capacitive micro-accelerometers are one of the most common micro-accelerometers. Their principle is to reflect the magnitude of acceleration by detecting the change in capacitance caused by the movement caused by the inertial force. Capacitive accelerometers have the characteristics of high sensitivity and measurement accuracy, good stability, small temperature drift and low power consumption. They are widely used in commercial fields such as automotive electronics and consumer electronics. In particular, they are highly valued in the fields of inertial measurement and national defense industry.

[0003] Currently, MEMS capacitive accelerometers can be roughly divided into "sandwich" capacitive accelerometers, torsion pendulum capacitive accelerometers and comb-tooth capacitive accelerometers based on their different structural forms. "Sandwich" capacitive accelerometers generally have complex processing technology, high sensitivity, good detection accuracy, good linearity, little temperature influence, and certain overload resistance. The torsion pendulum capacitive accelerometer has a simple structure, good integration, and can realize multi-axis detection. Its detection sensitivity is weaker than that of the "sandwich" capacitive accelerometer. At the same time, the torsion pendulum structure behaves as an asymmetric sensitive mass block, so the sensitive structure is not conducive to resisting the regional stress formed by large impacts. Compared with the first two structures, based on the characteristics of the comb-tooth structure, the comb-tooth capacitive accelerometer can better eliminate the coupling between different axial accelerations and has lower cross-coupling.

[0004] There are usually two types of comb-tooth accelerometer structures, namely surface structure and bulk silicon structure. Surface structure refers to a structure made by surface MEMS processing technology, including movable comb teeth located on the mass block and fixed comb teeth located on the periphery. Structures that need to be made by bulk silicon MEMS processing technology belong to bulk silicon structure. Surface structure has good compatibility with IC process, but it is difficult to use it to make Z-axis sensitive accelerometers, and generally has large cross coupling. The surface structure also has a weakness. Its measurement is achieved by changing the comb tooth gap, which causes the comb tooth capacitance to change. When the gap changes, the comb teeth are subject to large air damping. To reduce this damping, vacuum packaging is generally required. In the comb-tooth accelerometer with bulk silicon structure, the gap between the comb teeth remains unchanged during measurement. The relative position between the fixed comb teeth and the movable comb teeth slides, resulting in changes in the comb tooth capacitance to achieve measurement. The air damping is small, the thermomechanical noise is low, and the device does not need to be vacuum packaged. However, the elastic beam of the bulk silicon structure is long, and the chip area is large, which is not conducive to miniaturization.

[0005] In order to improve the performance of capacitive acceleration sensors and reduce the problem of excessive chip volume occupied by bulk silicon structures, the present invention proposes an overlapping structure comb-tooth capacitive Z-axis acceleration sensitive chip, which has the advantage of small air damping. It is characterized in that the elastic beam is located under the comb-tooth capacitor to form an overlapping structure, which does not require additional chip area, is conducive to miniaturization and can also reduce chip costs. Summary of the invention

[0006] In order to solve the above problems, an overlapping structure comb-tooth capacitive Z-axis acceleration sensitive chip and a manufacturing method thereof are provided. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0007] The technical solution of the present invention:

[0008] An overlapping structure comb-tooth capacitor type Z-axis acceleration sensitive chip comprises a comb-tooth capacitor layer and an elastic beam structure layer, which are bonded to form an integral structure; the integral structure comprises a mass block and a frame, the comb-tooth capacitor layer is made of n-type or p-type single crystal silicon, a first region is distributed on the comb-tooth capacitor layer, fixed comb teeth connected to the frame are made on the first region, movable comb teeth connected to the mass block are made on the first region, a region with a metal layer is distributed on the comb-tooth capacitor layer, through holes communicating with the SOI top silicon layer on the elastic beam structure layer are etched on the region and on the elastic beam structure layer; an elastic beam is made on the elastic beam structure layer, and the mass block is connected to the frame through the elastic beam; the fixed comb teeth and the movable comb teeth are connected to an external circuit through the region with the metal layer evaporated to form an acceleration detection circuit, and the acceleration signal is converted into an electrical signal for output.

[0009] Preferably, the first region is a p-type or n-type region.

[0010] Preferably: an area of ​​a vapor-deposited metal layer is distributed on the comb-teeth capacitor layer.

[0011] Preferably: symmetrically distributed elastic beams are manufactured on the elastic beam structure layer.

[0012] Preferably, the comb-teeth capacitor layer and the elastic beam structure layer are bonded together via an oxide layer.

[0013] The manufacturing method of the overlapping structure comb-tooth capacitor Z-axis acceleration sensitive chip mainly includes the following steps and sequence:

[0014] Step 1: using an SOI substrate and a single crystal silicon wafer A to manufacture an elastic beam structure layer, and manufacturing an elastic beam on the top silicon layer of the SOI substrate by etching technology;

[0015] Step 2: perform silicon-silicon bonding on one side of the elastic beam of the SOI substrate through an oxide layer and a single crystal silicon wafer A, thin the silicon wafer A to a desired thickness after bonding, and then make a groove above the elastic beam by etching technology to expose the elastic beam;

[0016] Step 3: Use a single crystal silicon wafer B to make a comb-tooth capacitor layer, bond the single crystal silicon wafer B to the grooved side of the elastic beam structure layer through the oxide layer, and thin it to a required thickness;

[0017] Step 4: Based on step 3, local doping is performed to form a first region;

[0018] Step 5: Based on step 4, the back surface of the corresponding area of ​​the mass block is thinned to leave a suitable movement gap for the mass block to move downward;

[0019] Step 6: After backside thinning in step 5, release the elastic beams by etching technology;

[0020] Step 7: using wet etching technology to etch through holes, so that the single crystal silicon layer where the elastic beam is located is exposed at the through holes, and then etching the lead holes on the first area;

[0021] Step 8: Vapor-deposit a layer of metal on the structure with the through-hole formed in step 7, and etch out the metal area. Then, an alloy process is used to form a good ohmic contact between the metal layer and the semiconductor thereunder;

[0022] Step 9: Based on step 8, the back side of the overall structure is anodic bonded to a suitable glass sheet;

[0023] Step 10: Using etching technology, fixed comb teeth and movable comb teeth are manufactured on the first area.

[0024] Preferably, it also includes step eleven: using a single crystal silicon wafer C to make a cover plate, etching an opening on the cover plate to release the metal layer area, and etching a thinning area to provide a suitable movement gap for the upward displacement of the mass block; finally, the cover plate and the main structure are BCB bonded to complete the main process production.

[0025] Preferably: in step three, an n-type or p-type single crystal silicon wafer B is used to make the comb-tooth capacitor layer.

[0026] The present invention has the following beneficial effects:

[0027] The sensitive chip of the present invention adopts a bulk silicon structure and has the advantages of Z-axis sensitivity and low damping coefficient;

[0028] The present invention adopts a structure in which the comb-tooth capacitor and the elastic beam are placed in an overlapping manner, so that the elastic beam does not need to occupy additional chip area, which is beneficial to miniaturization and can also reduce chip costs;

[0029] The structure of the comb-tooth capacitor and the elastic beam being placed overlappingly in the present invention avoids the elastic beam occupying the space of the comb teeth distributed around the mass block when placed in a plane, so that the distribution space of the comb-tooth capacitor around the mass block is larger, the number of comb teeth is greatly increased, and the capacitance of the comb-tooth structure is effectively increased;

[0030] The overlapping structure of the present invention enables the elastic beams to be symmetrically distributed around the mass block, thereby significantly reducing the cross-coupling effects in the X-axis and Y-axis directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 .Schematic diagram of the structure of the overlapping structure comb-tooth capacitor z-axis acceleration sensitive chip of the present invention;

[0032] Figure 2 The present invention is attached Figure 1 Exploded diagram of

[0033] Figure 3 The present invention is attached Figure 1 A partial enlarged view of point I in the middle;

[0034] Figure 4. (a) Structural schematic diagram of step 1 of the preparation method of the present invention;

[0035] Figure 4. (b) AA' cross-sectional view of step 1 of the preparation method of the present invention;

[0036] Figure 5 . AA' cross-sectional schematic diagram after bonding and thinning in step 2 of the preparation method of the present invention;

[0037] FIG6. (a) A schematic diagram of the structure of the elastic beam exposed after etching in step 2 of the preparation method of the present invention;

[0038] FIG6. (b) A schematic diagram of the AA' cross section of the elastic beam exposed after etching in step 2 of the preparation method of the present invention;

[0039] Figure 7 . AA' cross-sectional schematic diagram after bonding and thinning in step 3 of the preparation method of the present invention;

[0040] Figure 8. (a) Structural schematic diagram of step 4 of the preparation method of the present invention;

[0041] Figure 8. (b) AA' cross-sectional view of step 4 of the preparation method of the present invention;

[0042] Fig. 9 . AA' cross-sectional schematic diagram after thinning in step 5 of the preparation method of the present invention;

[0043] Fig.10 . AA' cross-sectional schematic diagram of the preparation method of the present invention after releasing the elastic beam in step 6;

[0044] Figure 11. (a) Structural schematic diagram of step 7 of the preparation method of the present invention;

[0045] Figure 11. (b) BB' cross-sectional view of step 7 of the preparation method of the present invention;

[0046] Figure 12. (a) Structural schematic diagram of step 8 of the preparation method of the present invention;

[0047] Figure 12. (b) BB' cross-sectional view of step 8 of the preparation method of the present invention;

[0048] Fig.13 . BB` cross-sectional view of the preparation method of the present invention after step 9 of anodically bonding the glass sheet;

[0049] Figure 14. (a) Structural schematic diagram of step 10 of the preparation method of the present invention;

[0050] Figure 14. (b) BB' cross-sectional view of step 10 of the preparation method of the present invention;

[0051] Fig.15 . Schematic diagram of the structure after etching the back side of the cover plate in step 11 of the preparation method of the present invention;

[0052] FIG. 16. (a) A schematic diagram of the structure after bonding the cover plate in step 11 of the preparation method of the present invention;

[0053] FIG. 16. (b) BB' cross-sectional view after bonding the cover plate in step 11 of the preparation method of the present invention;

[0054] Fig.17 . Schematic diagram of dimensioning of the elastic beam structure layer of the present invention;

[0055] Figure 18. (a) Schematic diagram of dimension marking of the present invention;

[0056] Figure 18. (b) CC' cross-sectional dimensioning diagram of the sensitive structure of the present invention;

[0057] Fig.19 . The measuring range in the embodiment of the present invention is ±5g (g = 9.8m / s 2 )Sensitive capacitor C 1 The simulation output characteristic curve of

[0058] Fig. 20 . The measuring range in the embodiment of the present invention is ±5g (g = 9.8m / s 2 )Sensitive capacitor C 2 The simulation output characteristic curve of

[0059] Fig.21 . The measuring range in the embodiment of the present invention is ±5g (g = 9.8m / s 2 )Sensitive Capacitor (C 1 -C 2 )’s simulation output characteristic curve.

[0060] In the figure: 1-comb-tooth capacitor layer; 2-elastic beam structure layer; 3-mass block; 4-frame; 5-first area; 6-fixed comb teeth; 7-movable comb teeth; 8-first metal electrode; 9-second metal electrode; 10-third metal electrode; 11-first through hole; 12-second through hole; 13-elastic beam; 14-lead hole; 31-first mass block; 32-second mass block; 33-third mass block; 41-first frame; 42-second frame; 43-third frame; 111-first frame through hole; 113-third frame through hole; 121-first mass block through hole; 123-third mass block through hole. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0062] Specific implementation method 1: Combination Figure 1-2The present embodiment is described. The overlapping structure comb-tooth capacitor Z-axis acceleration sensitive chip of the present embodiment is composed of a comb-tooth capacitor layer 1 and an elastic beam structure layer 2. The comb-tooth capacitor layer 1 is arranged on the elastic beam structure layer 2. The two are connected by an oxide layer to form an integral structure. The mass block 3 and the frame 4 are manufactured on the integral structure by bulk silicon MEMS processing technology. The comb-tooth capacitor layer 1 is made of n-type or p-type single crystal silicon, and a p-type or n-type region (first region 5) is distributed thereon. A solid connected to the frame 4 is manufactured on the p-type or n-type region. The fixed comb teeth 6 and the movable comb teeth 7 connected to the mass block 3, the comb teeth capacitor layer 1 is also distributed with areas 8, 9 and 10 with evaporated metal layers, and through holes 11 and 12 communicating with the SOI top silicon on the elastic beam structure layer 2 are etched on the areas 9 and 10; symmetrically distributed elastic beams 13 are made on the elastic beam structure layer 2, and the mass block 3 is connected to the frame 4 through the elastic beams 13; the fixed comb teeth 6 and the movable comb teeth 7 are connected to the external circuit through the areas 8 and 9 with evaporated metal layers to form an acceleration detection circuit, which converts the acceleration signal into an electrical signal for output.

[0063] Specific implementation method 2: Combination Figure 1-1 6. This embodiment is described. The manufacturing method of the overlapping structure comb-teeth capacitor Z-axis acceleration sensor chip of this embodiment is used to prepare the overlapping structure comb-teeth capacitor Z-axis acceleration sensor chip described in the specific embodiment 1. The main process steps and order are as follows:

[0064] Step 1: using an SOI substrate and a single crystal silicon wafer A to manufacture an elastic beam structure layer 2, and using an etching technique to manufacture an elastic beam 13 on the top silicon layer of the SOI substrate;

[0065] Step 2: perform silicon-silicon bonding on one side of the elastic beam of the SOI substrate through an oxide layer and a single crystal silicon wafer A, thin the silicon wafer A to a desired thickness after bonding, and then make a groove above the elastic beam by etching technology to expose the elastic beam 13;

[0066] Step 3: Use n-type (or p-type) single crystal silicon wafer B to make the comb-tooth capacitor layer 1, bond the silicon wafer B to the grooved side of the elastic beam structure layer 2 through the oxide layer, and thin it to the required thickness;

[0067] Step 4: Based on step 3, local doping is performed to form a first region 5;

[0068] Step 5: Based on step 4, the back surface of the corresponding area of ​​mass block 3 is thinned to leave a suitable movement gap for the downward displacement of mass block 3;

[0069] Step 6: After the back side is thinned in step 5, the elastic beam 13 is released by etching technology;

[0070] Step 7: using wet etching technology, etching through holes 11 and 12 to expose the single crystal silicon layer where the elastic beam 13 is located, and then etching out the lead hole 14 on the first area 5;

[0071] Step 8: vapor-deposit a layer of metal on the structure with through holes formed in step 7, and etch out metal regions 8, 9 and 10. Then, an alloy process is performed to form a good ohmic contact between the metal layer and the semiconductor thereunder;

[0072] Step 9: Based on step 8, the back side of the overall structure is anodic bonded to a suitable glass sheet;

[0073] Step 10: Using etching technology, a fixed comb tooth 6 and a movable comb tooth 7 are manufactured on the first area 5;

[0074] Step 11: Use the single crystal silicon wafer C to make a cover plate, on which openings for releasing the metal layer regions 8 and 9 are etched, and a thinning area is etched to leave a suitable movement gap for the mass block 3 to move upward; finally, the cover plate is bonded to the main structure by BCB bonding to complete the main process;

[0075] In addition to the advantage of a small damping coefficient, the present invention also has the following three advantages: first, the structure in which the comb-tooth capacitor and the elastic beam are placed overlappingly does not require additional chip area, which is conducive to miniaturization and can also reduce chip costs; second, the structure in which the comb-tooth capacitor and the elastic beam are placed overlappingly avoids the elastic beam occupying the space of the comb teeth distributed around the mass block when placed in a plane, greatly increases the number of comb teeth, and effectively increases the capacitance of the comb-tooth structure; third, the overlapping structure allows the elastic beam to be symmetrically distributed around the mass block, significantly reducing the cross-coupling effects in the X-axis and Y-axis directions.

[0076] Embodiment 1:

[0077] Combination Figure 1-21As shown: an overlapping structure comb-tooth capacitor Z-axis acceleration sensitive chip refers to the acceleration sensitive chip or a similar chip and its manufacturing method shown in the accompanying drawings of the present invention, the chip includes a comb-tooth capacitor layer 1 and an elastic beam structure layer 2, the two are connected through an oxide layer to form an integral structure; the integral structure includes a mass block 3 and a frame 4; a p-type or n-type region (first region 5) is made on the comb-tooth capacitor layer 1 by a doping process, and a fixed comb 6 connected to the frame 4 and connected to the mass block 3 are made on the p-type or n-type region. The movable comb teeth 7 are arranged on the comb teeth capacitor layer 1, and regions 8, 9 and 10 on which metal layers are evaporated are also distributed. Through holes 11 and 12 communicating with the top silicon layer of SOI on the elastic beam structure layer 2 are etched on the regions 9 and 10; symmetrically distributed elastic beams 13 are made on the elastic beam structure layer 2, and the mass block 3 is connected to the frame 4 through the elastic beams 13; the fixed comb teeth 6 and the movable comb teeth 7 are connected to the external circuit through the regions 8 and 9 on which metal layers are evaporated to form an acceleration detection circuit, so as to convert the acceleration signal into an electrical signal for output;

[0078] The overlapping structure comb capacitive Z-axis acceleration sensitive structure proposed in the present invention is used to design two ranges of ±5g (g = 9.8m / s 2 ) acceleration sensitive structure chip, the capacitance of the two are C 1 and C 2 Among them, C 1 The fixed comb teeth are set to low comb teeth, and the movable comb teeth are set to high comb teeth; C 2 The fixed comb teeth are set to high comb teeth, and the movable comb teeth are set to low comb teeth; the other dimensions of the two are exactly the same; (C 1 -C 2 ), that is, the difference between the two capacitances, this difference changes linearly with the acceleration of the load, and the present invention measures the acceleration by measuring this difference; by 1 and C 2 The difference between the output capacitance values ​​of the two complementary structures can effectively offset the nonlinear error, thereby greatly improving the linearity of the output characteristic curve;

[0079] C 1 The dimensions of the acceleration sensitive structure are as follows: Fig.17 As shown in Figure 18, where l 1 、w 1 and h 1 is the length, width and height of the overall structure, h 2 is the height of the elastic beam structure layer, l 2 and w 2 is the length and width of the border connection, l 3 and w 3 is the length and width of the mass block connection, l 4 、w 4 and h4 are the length, width and height of the elastic beam, h 5 is the distance from the bottom surface of the elastic beam to the bottom surface of the sensitive structure, l 5 is the length of the elastic beam at the fold, w 5 is the width of the mass block, w 6 is the distance between the elastic beam and the frame, w 7 is the distance between the elastic beam and the mass block, w 8 is the width of the comb teeth, h 6 and h 7 h is the height of the fixed and movable comb teeth. 8 is the thickness of the oxide layer, h 9 is the depth of thinning at the bottom of the mass block, w 9 is the width of the doped region, h 3 is the thickness of the metal layer, w 10 is the width of the through-hole electrode of the mass block, w 11 is the width of the mass block through hole, l 6 and w 12 is the length and width of the frame electrode, w 13 is the width of the frame hole, w 14 is the width of the doped region electrode. Its main structural parameters are shown in Table 1:

[0080] Table 1 Sensitive structural parameters using high and low misalignment distribution

[0081]

[0082]

[0083] C 2 The size of the acceleration sensitive structure and C 1 is exactly the same as the 5 ) and movable comb height (h 6 ) by C 1 The 50 and 62 are swapped to become 62 and 50; 1 and C 2 The thickness of the oxide layer contained in the sensitive structure is 1μm;

[0084] For the two acceleration sensitive chips with the above size parameters, the finite element software was used to perform simulation analysis, and the response characteristic curve of the capacitance changing with the loading acceleration was obtained; Fig.19 For sensitive chip C 1 (fixed comb teeth are low comb teeth, movable comb teeth are high comb teeth) simulation output characteristic curve diagram; Fig. 20 For sensitive chip C 2(fixed comb teeth are high comb teeth, movable comb teeth are low comb teeth) simulation output characteristic curve diagram; the present invention is to measure the difference (C 1 -C 2 ) is used to measure acceleration, and its output characteristic curve can be obtained by Fig.19 and Fig. 20 Get, such as Fig.21 As shown; using the difference (C 1 -C 2 ) When measuring acceleration, the output difference capacitance and acceleration show a good linear relationship, the nonlinearity is about 0.126% FS, the sensitivity is about 0.364pF / g, and the lateral cross coupling coefficient is about 0.1923%; Fig.21 and Fig.19 and Fig. 20 By comparison, it can be seen that the difference method effectively offsets C 1 and C 2 Non-linear error greatly improves the linearity of the output characteristic curve;

[0085] The method for manufacturing the overlapping structure comb-tooth capacitive Z-axis acceleration sensitive chip proposed in the present invention is used to manufacture C 1 and C 2 The method is as follows:

[0086] Step 1: Referring to FIG. 4 , an elastic beam structure layer 2 is manufactured using an SOI substrate and a double-polished single crystal silicon wafer A, and an elastic beam 13 is manufactured on the top silicon layer of the SOI substrate by etching technology;

[0087] Step 2: Reference Figure 5 6 , the elastic beam side of the SOI substrate is silicon-silicon bonded to the single crystal silicon wafer A through the oxide layer, and after bonding, the silicon wafer A is thinned to a desired thickness, and then a groove is opened above the elastic beam by etching technology to expose the elastic beam 13;

[0088] Step 3: Reference Figure 7 , using an n-type (or p-type) double-polished single-crystal silicon wafer B to make the comb-tooth capacitor layer 1, bonding the silicon wafer B to the grooved side of the elastic beam structure layer 2 through the oxide layer, and thinning it to the required thickness;

[0089] Step 4: Referring to FIG. 8 , based on step 3, local doping is performed to form a p-type (or n-type) region;

[0090] Step 5: Reference Fig. 9 On the basis of step 4, the back surface of the corresponding area of ​​mass block 3 is thinned to a depth of about 8 μm, leaving a suitable movement gap for the downward displacement of mass block 3;

[0091] Step 6: Reference Fig.10 , after the back side is thinned in step 5, the elastic beam 13 is released by etching technology;

[0092] Step 7: Referring to FIG. 11 , using a wet etching technique, the through holes 11 and 12 are etched to expose the single crystal silicon layer where the elastic beam 13 is located, and then the lead hole 14 on the p-type (or n-type) region is etched;

[0093] Step 8: Referring to FIG. 12 , a layer of metal (Au / Al) is evaporated on the structure in which the through hole is formed in step 7, and metal regions 8, 9 and 10 are etched out. After that, a good ohmic contact is formed between the metal layer and the semiconductor thereunder through an alloy process;

[0094] Step 9: Reference Fig.13 , on the basis of step (8), the back side of the overall structure is anodically bonded to the electrostatically bonded glass sheet;

[0095] Step 10: Referring to FIG. 14 , using etching technology, a fixed comb tooth 6 and a movable comb tooth 7 are manufactured on the p-type (or n-type) region, and the height difference between the fixed comb tooth 6 and the movable comb tooth 7 is 12 μm;

[0096] Step 11: Reference Fig.15 As shown in FIG16 , a double-polished single-crystal silicon wafer C is used to make a cover plate, openings corresponding to metal layer regions 8 and 9 are etched on the cover plate, and a thinning area is etched with a thinning depth of about 8 μm to provide a suitable movement gap for the upward displacement of the mass block 4; finally, the cover plate is bonded to the main structure by BCB glue to complete the main process;

[0097] The overlapping structure comb-teeth capacitive Z-axis acceleration sensitive structure and its manufacturing method proposed in the present invention can design structural parameters that meet the performance requirements of different application fields and manufacture sensitive chips. The prepared overlapping structure comb-teeth capacitive acceleration sensitive chip can be used in various fields such as automobiles, consumer electronics, industry, geological exploration, earthquake monitoring and national defense.

[0098] Embodiment 2:

[0099] Combination Figure 1-21 As shown:

[0100] The overlapping structure comb-tooth capacitor Z-axis acceleration sensitive chip includes a comb-tooth capacitor layer 1, an elastic beam structure layer 2, a first metal area 8, a second metal area 9 and a third metal area 10. The lower part of the comb-tooth capacitor layer 1 is connected to the upper part of the elastic beam structure layer 2. The right side of the comb-tooth capacitor layer 1 has a first area 5. The center of the first area 5 of the comb-tooth capacitor layer 1 is provided with the third metal area 10. The left side of the upper part of the comb-tooth capacitor layer 1 is provided with the second metal area 9 and the first metal area 8 arranged front and back. The first metal area 8 is connected to the first area 5. The second metal area 9 and the first metal area 8 are connected to the first area 5. A first through hole 11 is provided at the metal region 9, and a second through hole 12 is provided at the third metal region 10; the comb-tooth capacitor layer 1 is made of n-type (or p-type) single crystal silicon, and a p-type (or n-type) first region 5 is distributed thereon, and the first region 5 is made with fixed comb teeth 6 connected to the frame 4 and movable comb teeth 7 connected to the mass block 3, and the comb-tooth capacitor layer 1 is also distributed with regions 8, 9, and 10 where a metal layer is evaporated, and a first through hole 11 and a second through hole 12 communicating with the SOI top silicon layer on the elastic beam structure layer 2 are etched on the regions 9 and 10;

[0101] The comb-tooth capacitor layer 1 adopts silicon wafer B (single crystal silicon wafer), and the comb-tooth capacitor layer 1 includes a third mass block 33, a third frame 43, fixed comb teeth 6 and movable comb teeth 7. The third mass block 33 is arranged in the inner third mounting opening of the third frame 43, and the third mounting opening is located inside the first area 5. The fixed comb teeth 6, the movable comb teeth 7, the third mass block 33, and the edge of the third mounting opening of the third frame 43 form the first area 5. The movable comb teeth 7 are evenly arranged on the four sides of the square third mass block 33. The inner side wall of the third frame 43 is correspondingly provided with fixed comb teeth 6, and the movable comb teeth 7 are arranged crosswise with the fixed comb teeth 6.

[0102] The first metal area 8 is connected to the edge of the third mounting opening of the third frame 43, and a lead hole 14 is provided at the connection portion;

[0103] The elastic beam structure layer 2 includes a silicon wafer A (single crystal silicon wafer) and an SOI substrate, and the comb-tooth capacitor layer 1, the silicon wafer A, and the SOI substrate are connected in sequence from top to bottom;

[0104] The silicon wafer A comprises a first mass block 31 and a first frame 41, wherein the first frame 41 has a first mounting opening corresponding to the third mounting opening of the third frame 43, the first mass block 31 is arranged in the first mounting opening of the first frame 41, the first frame 41 is connected to the third frame 43 correspondingly, and the third mass block 33 is connected to the first mass block 31 correspondingly;

[0105] The SOI substrate includes a second mass block 32, a second frame 42 and an elastic beam 13. The second mass block 32 is arranged in the second mounting opening of the second frame 42. The upper side of the second frame 42 is connected to the upper side of the second mass block 32 through the elastic beam 13. The second frame 42 is correspondingly connected to the first frame 41, and the second mass block 32 is correspondingly connected to the first mass block 31. The elastic beam structure layer 2 is made with symmetrically distributed elastic beams 13, and the mass block 3 is connected to the frame 4 through the elastic beam 13. The fixed comb teeth 6 and the movable comb teeth 7 are connected to the external circuit through the areas 8 and 9 where the metal layer is evaporated to form an acceleration detection circuit, and the acceleration signal is converted into an electrical signal for output;

[0106] The four corners of the second mounting opening of the second frame 42 are provided with first protrusions, the middle parts of the four sides of the second mass block 32 are provided with second protrusions, the elastic beam 13 is a broken line structure (similar to a Z shape), and the elastic beam 13 is arranged between the adjacent first protrusions and the second protrusions, and the thickness of the elastic beam 13 is less than the thickness of the second mass block 32 or the second frame 42;

[0107] A third mass block through hole 123 is processed on the third mass block 33, a first mass block through hole 121 is processed on the first mass block 31, the third mass block through hole 123 and the first mass block through hole 121 are arranged correspondingly to form a second through hole 12, a third frame through hole 113 is processed on the third frame 43, a first frame through hole 111 is processed on the first frame 41, and the third frame through hole 113 and the first frame through hole 111 are arranged correspondingly to form a first through hole 11; the third mass block 33, the first mass block 31, and the second mass block 32 are arranged in sequence to form a mass block 3, the third frame 43, the first frame 41, and the second frame 42 are arranged in sequence to form a frame 4, the comb-tooth capacitor layer 1 is arranged on the elastic beam structure layer 2, and the two are connected by an oxide layer to form an integral structure; the mass block 3 and the frame 4 are manufactured on the integral structure by bulk silicon MEMS processing technology;

[0108] The inner walls of the second through hole 12 and the first through hole 11 have a metal layer, the second mass block 32 has a metal layer at a position corresponding to the second through hole 12, the second frame 42 has a metal layer at a position corresponding to the first through hole 11, the metal plating layer of the second through hole 12 is connected to the third metal region 10, and the metal plating layer of the first through hole 11 is connected to the second metal region 9;

[0109] The second through hole 12 and the first through hole 11 are both trapezoidal in shape with a narrow upper width;

[0110] The present invention improves the performance of the capacitive acceleration sensor and reduces the problem that the bulk silicon structure occupies too large a chip volume. The present invention proposes an overlapping structure comb-tooth capacitor Z-axis acceleration sensitive chip, which has the advantage of small air damping. The elastic beam is located under the comb-tooth capacitor to form an overlapping structure, which does not require additional chip area, is conducive to miniaturization, and can also reduce chip costs.

[0111] The method for preparing an overlapping structure comb-tooth capacitive Z-axis acceleration sensitive chip comprises the following steps:

[0112] Step 1: Referring to FIG. 4 , an elastic beam structure layer 2 is manufactured using an SOI substrate and a double-polished single crystal silicon wafer A, and an elastic beam 13 is manufactured on the top silicon layer of the SOI substrate by etching technology;

[0113] Step 2: Reference Figure 5 6 , the elastic beam of the SOI substrate is bonded to the single crystal silicon wafer A through an oxide layer by silicon-silicon bonding. After bonding, the single crystal silicon wafer A is thinned to a desired thickness, and then a groove is formed at the single crystal silicon wafer A corresponding to the elastic beam 13 above the elastic beam 13 by etching technology to expose the elastic beam 13;

[0114] In step 2, the silicon wafer A is divided into an outer first frame 41 and an inner first mass block 31 which are not connected to each other;

[0115] Step 3: Reference Figure 7 , using a double-polished single-crystal silicon wafer B to make the comb-tooth capacitor layer 1, bonding the single-crystal silicon wafer B to the grooved side of the elastic beam structure layer 2 through the oxide layer, and thinning the single-crystal silicon wafer B to a required thickness;

[0116] In step 3, the double-polished single-crystalline silicon wafer B is an n-type or p-type double-polished single-crystalline silicon wafer B;

[0117] Step 4: Referring to FIG. 8 , based on step 3, local doping is performed to form a first region 5;

[0118] In step 4, the double-polished single-crystal silicon wafer B is locally doped, and the formed first region 5 is an n-type region or a p-type region corresponding to step 3;

[0119] Step 5: Reference Fig. 9 , based on step 4, thinning the back side of the SOI substrate in the area corresponding to the mass block 3;

[0120] In step 5, the thinning depth is about 8 μm, leaving a suitable movement gap for the mass block 3 to move downward;

[0121] Step 6: Reference Fig.10 , after the back side is thinned in step 5, the elastic beam 13 is released by etching technology;

[0122] In step 6, a groove is formed on the bottom silicon of the SOI substrate at a position corresponding to the elastic beam 13 to expose the elastic beam 13, and then the top silicon of the SOI substrate is separated from the frame portion of the SOI substrate. In this step, the SOI substrate is divided into an outer second frame 42 and an inner second mass block 32. The second frame 42 and the second mass block 32 are connected by the elastic beam 13, and the elastic beam 13 is elastic.

[0123] Step 7: Referring to FIG. 11 , the first through hole 11 and the second through hole 12 are etched by wet etching technology to expose the single crystal silicon layer where the elastic beam 13 is located, and then the lead hole 14 on the first region 5 is etched;

[0124] In step seven, through holes are processed on the single crystal silicon wafer B and the single crystal silicon wafer A to form a first through hole 11 and a second through hole 12;

[0125] Step 8: Referring to FIG. 12 , a layer of metal is evaporated on the structure of the first through hole 11 and the second through hole 12 formed in step 7, and a first metal region 8, a second metal region 9, and a third metal region 10 are etched on the comb capacitor layer 1. After that, a good ohmic contact is formed between the metal layer and the semiconductor thereunder through an alloy process, and the first metal region 8 is connected to the lead hole 14 of the first region 5;

[0126] In step eight, the metal is Au / Al, which is evaporated on the inner wall of the first through hole 11 and the second through hole 12 and the position corresponding to the through hole on the SOI substrate;

[0127] Step 9: Reference Fig.13 On the basis of step eight, the back side of the overall structure (the back side of the SOI substrate) is anodically bonded to the electrostatically bonded glass sheet;

[0128] Step 10: Referring to FIG. 14 , using etching technology, fixed comb teeth 6 and movable comb teeth 7 are manufactured on the second area;

[0129] In step ten, similar to steps three and four, the second region is a p-type or n-type region, the height difference between the fixed comb teeth 6 and the movable comb teeth 7 is 12 μm, the height of the fixed comb teeth 6 is less than the height of the movable comb teeth 7, and the second region divides the comb-tooth capacitor layer 1 into an outer third frame 43 and an inner third mass block 33 which are not connected to each other, the inner wall of the third frame 43 is uniformly processed with fixed comb teeth 6, the outer wall of the third mass block 33 is uniformly processed with movable comb teeth 7, and the fixed comb teeth 6 and the movable comb teeth 7 are arranged crosswise; the third mass block 33, the first mass block 31, and the second mass block 32 are sequentially arranged to form a mass block 3, and the third frame 43, the first frame 41, and the second frame 42 are sequentially arranged to form a frame 4;

[0130] Step 11: Reference Fig.15As shown in FIG16 , a double-polished single crystal silicon wafer C is used to make a cover plate, openings corresponding to the first metal region 8 and the second metal region 9 are etched on the cover plate, and a thinning area corresponding to the mass block 3 is etched at the bottom; finally, the cover plate is bonded to the main structure (comb-tooth capacitor layer 1) by BCB glue to complete the main process;

[0131] In step 11, the depth of the thinning area is about 8 μm, which provides a suitable movement gap for the upward displacement of the mass block 3;

[0132] The present invention relates to a technical method for improving the performance of a capacitive acceleration sensitive chip and a method for manufacturing the sensitive chip, and belongs to sensor technology in the field of micro-electromechanical system (MEMS). The present invention improves the performance of a comb-tooth capacitive acceleration sensitive chip, can effectively reduce the area of ​​the comb-tooth capacitive acceleration sensitive chip, and has the advantages of high output linearity and low cross-coupling.

[0133] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Overlapping structure comb capacitive Z-axis acceleration sensitive chip, characterized by: The invention comprises a comb-tooth capacitor layer (1) and an elastic beam structure layer (2), wherein the comb-tooth capacitor layer (1) and the elastic beam structure layer (2) are bonded to form an integral structure; the integral structure comprises a mass block (3) and a frame (4); the comb-tooth capacitor layer (1) is made of n-type or p-type single crystal silicon, a first region (5) is distributed on the comb-tooth capacitor layer (1), fixed comb teeth (6) connected to the frame (4) are made on the first region (5), movable comb teeth (7) connected to the mass block (3) are made on the first region (5), and the comb-tooth capacitor layer (1) is provided with a plurality of movable comb teeth (8) connected to the mass block (3). The regions (8, 9, 10) are provided with metal layers, and through holes (11, 12) are etched on the regions (9) and (10) and communicate with the top silicon layer of SOI on the elastic beam structure layer (2); an elastic beam (13) is made on the elastic beam structure layer (2), and the mass block (3) is connected to the frame (5) through the elastic beam (13); the fixed comb teeth (6) and the movable comb teeth (7) are connected to an external circuit through the regions (8, 9) provided with the metal layers by evaporation to form an acceleration detection circuit, and the acceleration signal is converted into an electrical signal for output.

2. The overlapping structure comb-teeth capacitive Z-axis acceleration sensitive chip according to claim 1, characterized in that: The first region (5) is a p-type or n-type region.

3. The overlapping structure comb-teeth capacitive Z-axis acceleration sensitive chip according to claim 1, characterized in that: Regions (8, 9, 10) of a vapor-deposited metal layer are distributed on the comb-tooth capacitor layer (1).

4. The overlapping structure comb-teeth capacitive Z-axis acceleration sensitive chip according to claim 1, characterized in that: Symmetrically distributed elastic beams (13) are manufactured on the elastic beam structure layer (2).

5. The overlapping structure comb-teeth capacitive Z-axis acceleration sensitive chip according to claim 1, characterized in that: The comb-tooth capacitor layer (1) and the elastic beam structure layer (2) are bonded via an oxide layer.

6. The method for manufacturing the overlapping structure comb-tooth capacitive Z-axis acceleration sensitive chip according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: using an SOI substrate and a single crystal silicon wafer A to manufacture an elastic beam structure layer (2), and using an etching technique to manufacture an elastic beam (13) on the top silicon layer of the SOI substrate; Step 2: perform silicon-silicon bonding on one side of the elastic beam of the SOI substrate through an oxide layer and a single crystal silicon wafer A, thin the silicon wafer A to a desired thickness after bonding, and then create a groove above the elastic beam by etching technology to expose the elastic beam (13); Step 3: Using a single crystal silicon wafer B to make a comb-tooth capacitor layer (1), bonding the single crystal silicon wafer B to the grooved side of the elastic beam structure layer (2) through an oxide layer, and thinning it to a desired thickness; Step 4: Based on step 3, local doping is performed to form a first region (5); Step 5: Based on step 4, the back surface of the corresponding area of ​​the mass block (3) is thinned to leave a suitable movement gap for the mass block (3) to move downward; Step 6: After the back side is thinned in step 5, the elastic beam (13) is released by etching technology; Step 7: using wet etching technology to etch through holes (11, 12) so that the single crystal silicon layer where the elastic beam (13) is located is exposed at the through holes, and then etching a lead hole (14) on the first area (5); Step 8: vapor-depositing a layer of metal on the structure with the through hole formed in step 7, and etching out metal areas (8, 9, 10), and then, through an alloying process, forming a good ohmic contact between the metal layer and the semiconductor thereunder; Step 9: Based on step 8, the back side of the overall structure is anodic bonded to a suitable glass sheet; Step 10: Using etching technology, fixed comb teeth (6) and movable comb teeth (7) are manufactured on the first area (5).

7. The method for manufacturing the overlapping structure comb-teeth capacitive Z-axis acceleration sensitive chip according to claim 6, characterized in that: The method further comprises step eleven: using a single crystal silicon wafer C to manufacture a cover plate, etching an opening on the cover plate to release the metal layer area (8, 9), and etching a thinning area to provide a suitable movement gap for the mass block (3) to move upward; finally, performing BCB bonding on the cover plate and the main structure to complete the main process manufacturing.

8. The method for manufacturing the overlapping structure comb-teeth capacitive Z-axis acceleration sensitive chip according to claim 6, characterized in that: In step three, an n-type or p-type single crystal silicon wafer B is used to manufacture a comb-tooth capacitor layer (1).

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