Two-dimensional vector 7-shaped connecting beam multi-purpose sensor and preparation method thereof

Abstract

A two-dimensional vector 7-shaped connecting beam multi-purpose sensor and a preparation method thereof, comprising: a substrate, a mass block suspended in the center of the substrate through a plurality of connecting beams, comb-tooth capacitors as detection parts respectively located at the common ends of the mass block, cilia arranged on the mass block, and electrode layers located above the comb-tooth capacitors and the four corners of the substrate, wherein: four groups of comb-tooth capacitors and the mass block constitute inter-plate differential capacitance, the comb-tooth capacitor pair parallel to the X-axis direction is used to detect the magnitude and direction of the flow field velocity or acceleration in the X-axis direction, and the comb-tooth capacitor pair parallel to the Y-axis direction is used to detect the magnitude and direction of the flow field velocity or acceleration in the Y-axis direction. The present invention captures changes in the air flow field through the cilia on the sensor, and the mass block of the sensor senses changes in acceleration.

Description

Technical Field

[0001] The present invention relates to a technology in the field of semiconductor sensors, in particular to a two-dimensional vector 7-shaped connecting beam multi-purpose sensor and a preparation method thereof. Background Art

[0002] Most of the existing two-dimensional MEMS flow field sensors and two-dimensional MEMS accelerometer sensors are made of silicon. They mainly use elastic connecting beam structures such as crab-leg beams and serpentine beams to achieve the displacement of the mass block, and the displacement depends on the stiffness of the elastic connecting beam. At present, there are more studies and applications on common elastic connecting beams, while there are fewer innovations and improvements on new elastic connecting beam structures. At the same time, the elastic connecting beam structure currently used in two-dimensional devices will have a low sensitivity of the device because the stiffness of the biaxial direction is too large after coupling. Summary of the invention

[0003] Aiming at the problem that the preparation process of the existing SOI process MEMS six-axis force sensor is complicated and the number of lithography times is large, resulting in a very low yield of the manufactured device, the present invention proposes a two-dimensional vector 7-shaped connecting beam multi-purpose sensor and a preparation method thereof. Starting from the structure of the elastic connecting beam, a novel 7-shaped connecting beam is designed, and the cilia on the sensor capture the change of the air flow field. The mass block of the sensor senses the change of acceleration. By measuring the capacitance change corresponding to the comb capacitance in the X or Y direction, the multi-purpose sensing of the flow field velocity and the two-dimensional vector size and direction of the acceleration can be obtained.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a two-dimensional vector 7-shaped connecting beam multi-purpose sensor, comprising: a substrate, a mass block suspended in the center of the substrate through a plurality of connecting beams, comb-tooth capacitors as detection parts respectively located at the common ends of the mass block, cilia arranged on the mass block, and electrode layers located above the comb-tooth capacitors and the four corners of the substrate, wherein: four groups of comb-tooth capacitors and the mass block constitute inter-plate differential capacitors, the comb-tooth capacitor pair parallel to the X-axis direction is used to detect the magnitude and direction of the flow velocity or acceleration of the flow field in the X-axis direction, and the comb-tooth capacitor pair parallel to the Y-axis direction is used to detect the magnitude and direction of the flow velocity or acceleration of the flow field in the Y-axis direction.

[0006] There are eight connecting beams in total, and each group of two is respectively arranged at a corner of the mass block to realize the suspended arrangement of the mass block. The connecting beams in each group are arranged at an acute angle to have a smaller rigidity.

[0007] The cilia are made of SU-8 material and are evenly distributed on the mass block, wherein: one cilia is located in the middle of the mass block, and the other four cilia are symmetrically distributed around it.

[0008] Technical Effects

[0009] The present invention realizes a 7-shaped connecting beam structure with an acute angle through a simple process. Compared with a crab-leg-shaped beam, the structure has smaller rigidity and can have a larger displacement response under the same external input, which is more conducive to sensor detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a three-dimensional schematic diagram of the present invention;

[0011] Figure 2 It is a side view of the present invention;

[0012] Figure 3 Schematic diagram of electrode layer;

[0013] Figure 4 and Figure 5 It is a partial enlarged schematic diagram of the present invention;

[0014] Figure 6 is a schematic diagram of the connecting beam;

[0015] Figure 7 It is a schematic diagram for comparing the effects of the embodiments;

[0016] Figure 8 It is a schematic diagram of displacement size after the present invention improves the design based on the serpentine beam and the folded beam;

[0017] Fig. 9 The radiation diagram of the capacitance value and angle relationship of the embodiment;

[0018] In the figure: comb-tooth capacitors 1 to 4, parts a and b at both ends of the comb-tooth capacitor, mass block 5, cilia 6, substrate 7, electrode layer 8, connecting beam 9, array recessed holes 10, and anchor block 11. DETAILED DESCRIPTION

[0019] like Figure 1 to Figure 3 As shown, this embodiment involves a two-dimensional vector 7-shaped connecting beam multi-purpose sensor, including: a substrate 7, a mass block suspended in the center of the substrate 7 through a plurality of connecting beams 9, comb-tooth capacitors 1, 2, 3, 4 as detection parts respectively located at the common ends around the mass block 5, cilia 6 arranged on the mass block 5, and an electrode layer 8 located above the comb-tooth capacitors and the four corners of the substrate 7, wherein: the four groups of comb-tooth capacitors 1, 2, 3, 4 and the mass block 5 constitute inter-plate differential capacitors, which are convenient for amplifying the detection amount.

[0020] In the inter-plate differential capacitor, the comb-tooth capacitor pair parallel to the X-axis direction is used to detect the magnitude and direction of the flow velocity or acceleration of the flow field in the X-axis direction, and the comb-tooth capacitor pair parallel to the Y-axis direction is used to detect the magnitude and direction of the flow velocity or acceleration of the flow field in the Y-axis direction.

[0021] The comb-tooth capacitors 1, 2, 3, 4, the mass block 5 and the connecting beam 9 are made of conductive silicon.

[0022] like Figure 4 and Figure 5 As shown, the cilia 6 are evenly distributed on the mass block 5, wherein: one SU-8 cilia is located in the middle, and the other four SU-8 cilia are symmetrically distributed around it.

[0023] The symmetrical distribution is preferably at the four equal points on the diagonal of the mass block 5.

[0024] The substrate 7 is made of glass material, and is anodic bonded to the device main body silicon. The glass material can reduce the parasitic capacitance of the device and avoid the influence on the measurement.

[0025] The electrode layer 8 is obtained by sputtering Cr / Au metal, specifically: Cr metal is sputtered first, and then Au metal is sputtered, the purpose of which is to make Au metal better connected with silicon and prevent Au metal from falling off.

[0026] like Figure 5 and Figure 6 As shown, there are eight connecting beams 9, and each group of two is respectively arranged at a corner of the mass block 5 to realize the suspended setting of the mass block. Each group of connecting beams 9 is arranged at an acute angle to have a smaller rigidity. The specific rigidity is Where: L a and L b is the length of the two parts of the 7-shaped connecting beam, E is the Young's modulus of silicon, t is the thickness of the beam, w is the width of the beam, and θ is the angle between the two parts.

[0027] The mass block 5 is provided with an array of concave holes 10 to reduce the mass of the mass block and reduce the influence of gravity on the sensor.

[0028] The present embodiment relates to the above-mentioned two-dimensional vector 7-shaped connecting beam multi-purpose sensor, whose working mode includes capacitive sensing, specifically: when the mass block / cilia is subjected to external force or acceleration changes, it will produce a certain displacement, causing the gap between the comb tooth capacitor pair to change, thereby measuring the comb tooth capacitance to obtain the two-dimensional vector size and direction of the external force and acceleration, that is, capacitive sensing.

[0029] The sensor improves the measurement sensitivity by performing differential processing on the output signal through the comb capacitance in the X or Y axis direction.

[0030] The output signal is obtained by applying carrier waves with opposite phases to both ends of the four comb-tooth capacitors 1, 2, 3, and 4 to measure the X or Y axis direction; then connecting to the CV conversion circuit, which is a capacitive mode. When the external input force is constant, by changing the direction of the external force, the values ​​of the four comb-tooth capacitors are as follows: Fig. 9 As shown in the radiation diagram, it can be seen that the values ​​of the four groups of comb capacitances can uniquely reflect the direction of the external force, thereby realizing the measurement of the two-dimensional vector.

[0031] This embodiment relates to a method for preparing the above-mentioned two-dimensional vector 7-shaped connecting beam multi-purpose sensor, which is to integrate the substrate 7 and the anchor block 11 by wet etching on the glass substrate 7 or by anodic bonding technology on the silicon wafer substrate, specifically comprising:

[0032] Step 1) spin coating photoresist and photolithography anchor block pattern;

[0033] Step 2) using the photoresist after photolithography as a mask, DRIE or wet etching to form anchor blocks, and then removing the photoresist;

[0034] Step 3) Anodic bonding the glass to the back side of the etched silicon wafer, or anodic bonding the back side of the silicon wafer to the front side of the etched glass;

[0035] Step 4) grinding the front side of the silicon wafer to a specific thickness;

[0036] Step 5) sputtering Cr and Au;

[0037] Step 6) Spin-coating photoresist and photolithography electrode pattern;

[0038] Step 7) using the photoresist after photolithography as a mask, etching Cr and Au, and removing the resist;

[0039] Step 8) Spin-coating photoresist and photolithography device main body pattern;

[0040] Step 9) using the photoresist after photolithography as a mask, DRIE etches out the device body and removes the resist;

[0041] Step 10) attaching SU-8 dry film;

[0042] Step 11) Photolithography of cilia pattern and degumming;

[0043] Step 12) laser slicing to finally obtain the sensor structure.

[0044] After specific simulation, when the two parts of the 7-shaped connecting beam are set at 1000μm and the acute angle is 45 to 90 degrees as the test condition, the experimental data that can be obtained are: at about 80.8 degrees, the 7-shaped connecting beam has the largest displacement size.

[0045] The stiffness of the 7-shaped connecting beam is derived. Under the same external flow field force input and the two parts of the 7-shaped connecting beam are 1000μm long, 40μm wide and 40μm thick, the experimental data that can be obtained is: the mass block has the largest displacement at about 73.1 degrees. This result is somewhat different from the formula derivation. The reason is that there are many other factors that affect the displacement size during the simulation process. However, the derived stiffness formula is roughly consistent with the trend of the simulation, such as Figure 7 As shown, it shows that the derived stiffness formula is roughly consistent with the actual situation.

[0046] The 7-shaped connecting beam in this device has a smaller stiffness than the crab-leg beam. In the same size design, the 7-shaped connecting beam can have a larger displacement response under the same external input, which can bring 1.3 times the displacement of the crab-leg beam. At the same time, as a two-dimensional sensor, such as Figure 8 As shown, the use of a 7-shaped connecting beam improvement in the design of serpentine beams and folded beams can also have a smaller stiffness size.

[0047] Compared with the existing MEMS flow field velocity or acceleration sensor, the present invention has the following advantages: 1) the sensor of the present invention can realize the vector measurement of the velocity or acceleration of the two-dimensional flow field; 2) the sensor of the present invention can perform vector measurement, and the sensing type is flow velocity and acceleration; 3) the sensor of the present invention adopts a sharp-angle 7-shaped connecting beam design, which makes it easier for the mass block to produce displacement, thereby realizing the amplification of the measurement sensitivity.

[0048] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A two-dimensional vector 7-shaped beam multi-purpose sensor, characterized in that: include: A substrate, a mass block suspended in the center of the substrate through a plurality of connecting beams, comb-tooth capacitors as detection parts respectively located at the common ends of the mass block, cilia arranged on the mass block, and electrode layers located above the comb-tooth capacitors and four corners of the substrate, wherein: four groups of comb-tooth capacitors and the mass block constitute inter-plate differential capacitors, the comb-tooth capacitor pair parallel to the X-axis direction is used to detect the magnitude and direction of the flow velocity or acceleration of the flow field in the X-axis direction, and the comb-tooth capacitor pair parallel to the Y-axis direction is used to detect the magnitude and direction of the flow velocity or acceleration of the flow field in the Y-axis direction; There are eight connecting beams in total, and each group of two is respectively arranged at a corner of the mass block to realize the suspended setting of the mass block. Each group of connecting beams is arranged at an acute angle to have a smaller rigidity. The specific rigidity is Where: L a and L b is the length of the two parts of the 7-shaped connecting beam, E is the Young's modulus of silicon, t is the thickness of the beam, w is the width of the beam, and θ is the angle between the two parts.

2. The two-dimensional vector 7-shaped beam multi-purpose sensor according to claim 1 is characterized in that: The cilia are made of SU-8 material and are evenly distributed on the mass block, wherein: one cilia is located in the middle of the mass block, and the other four cilia are symmetrically distributed around it.

3. The two-dimensional vector 7-shaped beam multi-purpose sensor according to claim 1 is characterized in that: The substrate is made of glass material, and is anode-bonded to the device main body silicon to reduce the parasitic capacitance of the device.

4. The two-dimensional vector 7-shaped beam multi-purpose sensor according to claim 1 is characterized in that: The electrode layer is obtained by sputtering Cr / Au metal, specifically: Cr metal is sputtered first, and then Au metal is sputtered, the purpose of which is to make Au metal better connected with silicon and prevent Au metal from falling off.

5. The two-dimensional vector 7-shaped beam multi-purpose sensor according to claim 1 is characterized in that: The mass block is provided with an array of concave holes to reduce the mass of the mass block and reduce the influence of gravity on the sensor.

6. A sensing method according to any one of claims 1 to 5, characterized in that: It includes capacitive sensing and resonant sensing. Specifically, when the mass block is subjected to external force or acceleration changes, it will produce a certain displacement, causing the gap between the comb-tooth capacitor pair to change. By measuring the comb-tooth capacitance, the two-dimensional vector size and direction of the external force and acceleration can be obtained, which is capacitive sensing.

7. The method according to claim 6, characterized in that: The sensor improves the measurement sensitivity by performing differential processing on the output signal through the comb capacitance in the X or Y axis direction.

8. The method according to claim 7, characterized in that: The output signal is obtained in the following manner: carrier waves with opposite phases are applied to both ends of the four groups of comb-tooth capacitors to measure the X or Y axis direction; then the CV conversion circuit is connected, i.e., the capacitive type; when the external input force is constant, by changing the direction of the external force, the four groups of comb-tooth capacitors uniquely reflect the direction of the external force, thereby realizing the measurement of the two-dimensional vector.

9. A method for preparing the sensor according to any one of claims 1 to 5, characterized in that: The substrate and the anchor block are integrated by wet etching on the substrate or by anodic bonding technology on the silicon wafer substrate, specifically including: Step 1) spin coating photoresist and photolithography anchor block pattern; Step 2) using the photoresist after photolithography as a mask, DRIE or wet etching to form anchor blocks, and then removing the photoresist; Step 3) Anodic bonding the glass to the back side of the etched silicon wafer, or anodic bonding the back side of the silicon wafer to the front side of the etched glass; Step 4) grinding the front side of the silicon wafer to a specific thickness; Step 5) sputtering Cr and Au; Step 6) Spin-coating photoresist and photolithography electrode pattern; Step 7) using the photoresist after photolithography as a mask, etching Cr and Au, and removing the resist; Step 8) Spin-coating photoresist and photolithography device main body pattern; Step 9) using the photoresist after photolithography as a mask, DRIE etches out the device body and removes the resist; Step 10) attaching SU-8 dry film; Step 11) Photolithography of cilia pattern and degumming; Step 12) laser slicing to finally obtain the sensor structure.

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