High-precision silicon resonance pressure sensor and manufacturing process thereof

Abstract

The invention discloses a high-precision silicon resonance pressure sensor and a manufacturing process thereof, and belongs to the technical field of semiconductor micro electro mechanical systems. The dual-mass-block coupling structure comprises a first mass block and a second mass block; the first mass block is connected with the second mass block through an H-shaped coupling beam; the first mass block is externally connected with a first cantilever beam and a fourth cantilever beam; the first cantilever beam and the fourth cantilever beam are respectively connected with the fourth supporting block and the first supporting block in an anchoring manner; the second mass block is externally connected with a second cantilever beam and a third cantilever beam; and the second cantilever beam and the third cantilever beam are respectively connected with the supporting block and the supporting block in an anchoring manner. According to the invention, the resonator with the dual-mass-block coupling structure is used for replacing a traditional beam-type resonator, and the problem of modal crosstalk of the beam-type resonator is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor micro-electromechanical systems, and in particular relates to a high-precision silicon resonant pressure sensor and a manufacturing process thereof. Background Art

[0002] With the development of micro-electromechanical technology, MEMS silicon resonant pressure sensors are increasingly widely used in aerospace, industrial control, meteorological measurement and other fields due to their high precision, high stability, mass production, small size, low power consumption and other characteristics. Silicon resonant pressure sensors are usually composed of a pressure-sensitive diaphragm and a resonator. When external pressure acts on the sensitive diaphragm, the sensitive diaphragm will bend and deform, causing the stiffness of the resonator on the diaphragm to change, and ultimately causing the resonant frequency of the resonator to change. The value of the external pressure can be obtained by detecting the change in the resonant frequency.

[0003] At present, the resonator structure of silicon resonant pressure sensors usually adopts the form of resonant beams, including single beam structure, double beam structure, double H beam structure, etc. This beam structure is simple and easy to be processed and manufactured. However, there are still some technical problems that have not been solved in these beam-type silicon resonant pressure sensors. For example, the relevant silicon resonant pressure sensors disclosed in Chinese patent publications CN109485011A, CN109879239A, and CN109883579A are all resonant structures in the form of resonant beams. The stiffness of the resonant beam is relatively small, and the working modal frequency is generally low, usually in the range of 20KHz to 60KHz. Its adjacent interference mode is usually also in this frequency range, which is easy to cause crosstalk between working modes and affect the pressure measurement accuracy. In addition, the detection comb teeth and driving comb teeth of the silicon resonant pressure sensor in the form of a resonant beam are usually located on both sides of the resonant beam. Under the influence of the micro-nano size effect, the electrical signal output by the driving comb teeth will directly pass through the resonant beam to the detection comb teeth, so that the electrical signal at the output end contains not only the detection signal but also the driving signal, which greatly affects the stability of the output signal and the Q value. Summary of the invention

[0004] The purpose of the present invention is to provide a high-precision silicon resonant pressure sensor and its manufacturing process in view of the above-mentioned deficiencies in the prior art, so as to solve the problems of low stiffness and severe modal crosstalk of traditional beam-type structures, which affect the measurement accuracy.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, a high-precision silicon resonant pressure sensor includes a dual-mass block coupling structure; the dual-mass block coupling structure includes a first mass block and a second mass block; the first mass block is connected to the second mass block via an H-shaped coupling beam; the first mass block is externally connected to a first cantilever beam and a fourth cantilever beam, and the first cantilever beam and the fourth cantilever beam are respectively anchored to a fourth support block and a first support block; the second mass block is externally connected to a second cantilever beam and a third cantilever beam; the second cantilever beam and the third cantilever beam are respectively anchored to a support block and a support block.

[0007] Furthermore, the first mass block and the second mass block are symmetrically distributed on both sides of the H-shaped coupling beam.

[0008] Furthermore, a first driving comb tooth is arranged on the outer side of the first mass block, and a first detecting comb tooth is arranged on the inner side of the first mass block.

[0009] Furthermore, second driving comb teeth are arranged on the outer side of the second mass block, and second detecting comb teeth are arranged on the inner side of the second mass block.

[0010] Furthermore, the differential capacitor of the first detection comb teeth and the differential capacitor of the second detection comb teeth are both externally connected to a differential operational amplifier.

[0011] In a second aspect, a manufacturing process of a high-precision silicon resonant pressure sensor comprises the following steps:

[0012] S1. Substrate layer etching: using deep silicon etching to etch the silicon support column of the double-sided polished silicon wafer, and oxidizing the upper surface of the etched substrate layer;

[0013] S2, device layer bonding: bonding the device layer silicon and the substrate layer silicon;

[0014] S3, device layer etching: etching the device layer to form a dual-mass block coupling structure;

[0015] S4, cap layer etching: using deep silicon etching to etch the cap cavity on the double-sided polished N-type silicon wafer, and oxidizing the lower surface of the etched cap layer;

[0016] S5, vacuum bonding: vacuum bonding the device layer silicon and the cap layer silicon;

[0017] S6, P-type doping: Use solid-state diffusion method to locally dope the upper surface of the cap layer silicon with P-type to form a PN junction;

[0018] S7, lead hole etching: deep silicon etching is performed on the cap layer silicon, and then the oxide layer formed after oxidation treatment is removed to expose the device layer silicon at the pad position;

[0019] S8, etching the pressure sensitive membrane: etching the substrate layer silicon to obtain the pressure sensitive membrane;

[0020] S9, glass sheet bonding: bonding the substrate layer silicon and the glass sheet;

[0021] S10, metallized pad: titanium tungsten gold is deposited at the pad position of the device layer silicon and the heavily doped position of the cap layer silicon, and the titanium tungsten gold is annealed to form an ohmic contact.

[0022] Furthermore, the thickness of the double-sided polished silicon wafer in S1 is 400 microns, and the etching depth of the silicon support column is 200 microns.

[0023] Furthermore, the etching depth of the cap cavity in S4 is 50 microns.

[0024] Furthermore, the etching depth of the substrate layer silicon in S8 is 150 microns, and the thickness of the pressure sensitive membrane is 50 microns.

[0025] Furthermore, the thickness of the glass sheet in the S9 is 3 mm.

[0026] The high-precision silicon resonant pressure sensor and its manufacturing process provided by the present invention have the following beneficial effects:

[0027] The present invention adopts a dual-mass coupling structure as the resonator component of the resonant pressure sensor, and uses multiple cantilever beams as the motion support components of the resonator component. The overall structural stiffness is much greater than that of the single resonant beam structure, so that the frequency interval between adjacent interference modes and working modes is large, avoiding the phenomenon of modal interference. At the same time, the resonator structure based on the dual-mass coupling structure is provided with differential detection comb teeth, and the electrical signal output by the drive comb teeth is offset by differential subtraction, thereby achieving the purpose of eliminating the drive interference signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of the high-precision silicon resonant pressure sensor in Example 1 of the present invention.

[0029] Figure 2 This is a detection state diagram of the high-precision silicon resonant pressure sensor in Example 1 of the present invention.

[0030] Figure 3 This is the etching diagram of the substrate layer in Example 2 of the present invention.

[0031] Figure 4 This is a device layer bonding diagram in Example 2 of the present invention.

[0032] Figure 5 This is the device layer etching diagram in Example 2 of the present invention.

[0033] Figure 6This is the etching diagram of the capping layer in Example 2 of the present invention.

[0034] Figure 7 This is a vacuum bonding diagram in Example 2 of the present invention.

[0035] Figure 8 This is the P-type doping diagram in Example 2 of the present invention.

[0036] Fig. 9 This is the lead hole etching diagram in Example 2 of the present invention.

[0037] Fig.10 This is an etching diagram of the pressure sensitive membrane in Example 2 of the present invention.

[0038] Fig.11 This is a glass sheet bonding diagram in Example 2 of the present invention.

[0039] Fig.12 This is a diagram of a metallized pad in Example 2 of the present invention.

[0040] Among them, 1. first driving comb teeth; 2. second driving comb teeth; 3. first detection comb teeth; 4. second detection comb teeth; 5. first mass block; 6. second mass block; 7. H-shaped coupling beam; 8. first cantilever beam; 9. second cantilever beam; 10. third cantilever beam; 11. fourth cantilever beam; 12. first support block; 13. second support block; 14. third support block; 15. fourth support block. DETAILED DESCRIPTION

[0041] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0042] Example 1

[0043] This embodiment provides a high-precision silicon resonant pressure sensor. Based on the high stiffness of the dual-mass coupling structure, this embodiment improves the operating modal frequency of the silicon resonant pressure sensor, increases the frequency interval of adjacent interference modes, avoids the phenomenon of modal interference, and eliminates the influence of the driving interference signal based on the detection method of differential comb teeth, further improving the measurement accuracy. Figure 1 , which specifically include:

[0044] The dual-mass block coupling structure includes a first driving comb tooth 1, a second driving comb tooth 2, a first detection comb tooth 3, a second detection comb tooth 4, a first mass block 5, a second mass block 6, an H-shaped coupling beam 7, a first cantilever beam 8, a second cantilever beam 9, a third cantilever beam 10, a fourth cantilever beam 11, a first support block 12, a second support block 13, a third support block 14 and a fourth support block 15.

[0045] Specifically, the first mass block 5 is connected to the second mass block 6 via the H-shaped coupling beam 7 , and the first mass block 5 and the second mass block 6 are symmetrically distributed on both sides of the H-shaped coupling beam 7 .

[0046] The first mass block 5 is externally connected to the first cantilever beam 8 and the fourth cantilever beam 11, and the first cantilever beam 8 and the fourth cantilever beam 11 are respectively anchored to the fourth support block 15 and the first support block 12; the second mass block 6 is externally connected to the second cantilever beam 9 and the third cantilever beam 10, and the second cantilever beam 9 and the third cantilever beam 10 are respectively anchored to the support block and the support block.

[0047] In order to eliminate the driving interference signal, in this embodiment, a first driving comb tooth 1 is set on the outer side of the first mass block 5, and a first detection comb tooth 3 is set on the inner side of the first mass block 5; and a second driving comb tooth 2 is set on the outer side of the second mass block 6, and a second detection comb tooth 4 is set on the inner side of the second mass block 6.

[0048] In addition, the differential capacitor of the first detection comb teeth 3 and the differential capacitor of the second detection comb teeth 4 are both externally connected to the differential operational amplifier.

[0049] In a specific application of this embodiment, when external pressure acts on the silicon resonant pressure sensor, the first support block 12, the second support block 13, the third support block 14, and the fourth support block 15 are compressed and flexurally deformed, and the first cantilever beam 8, the second cantilever beam 9, the third cantilever beam 10, and the fourth cantilever beam 11 are subjected to axial compressive stress, and then the stiffness of the first cantilever beam 8, the second cantilever beam 9, the third cantilever beam 10, and the fourth cantilever beam 11 will change, thereby changing the stiffness of the dual-mass resonator, i.e., the dual-mass coupling structure, resulting in a change in the resonant frequency of the dual-mass resonator, and by loading electrostatic force on the first drive comb teeth 1 and the second drive comb teeth 2, the first mass block 5 and the second mass block 6 are driven to perform resonant working mode motion in opposite directions, such as Figure 2 The resonance frequency of the dual-mass resonator is detected by the differential capacitance change of the first detection comb teeth 3 and the second detection comb teeth 4, and the influence of the driving interference signal can be eliminated by an external differential operational amplifier. In this way, the value of the external pressure can be obtained by detecting the change of the resonance frequency.

[0050] Example 2

[0051] This embodiment provides a manufacturing process of a high-precision silicon resonant pressure sensor, comprising the following steps:

[0052] Step S1: Reference Figure 3 , substrate layer etching: using deep silicon etching to etch the silicon support column of the double-sided polished silicon wafer, and oxidizing the upper surface of the etched substrate layer;

[0053] In this embodiment, the thickness of the double-sided polished silicon wafer is preferably 400 microns, and the etching depth of the silicon support column is 200 microns.

[0054] Step S2: Reference Figure 4 , Device layer bonding: bonding the device layer silicon to the substrate layer silicon;

[0055] In this embodiment, the preferred device layer silicon thickness is 50 microns.

[0056] Step S3: Reference Figure 5 , device layer etching: etching the device layer to form a dual-mass block coupling structure;

[0057] In this embodiment, the DRIE process is used to etch the device layer to produce the first drive comb teeth 1, the second drive comb teeth 2, the first detection comb teeth 3, the second detection comb teeth 4, the first mass block 5, the second mass block 6, the H-shaped coupling beam 7, the first cantilever beam 8, the second cantilever beam 9, the third cantilever beam 10, the fourth cantilever beam 11, the first support block 12, the second support block 13, the third support block 14 and the fourth support block 15.

[0058] Step S4: Reference Figure 6 , Cap layer etching: deep silicon etching is used to etch the cap cavity on the double-sided polished N-type silicon wafer, and the lower surface of the etched cap layer is oxidized;

[0059] In this embodiment, the etching depth of the cap cavity is preferably 50 microns.

[0060] Step S5: Reference Figure 7 , Vacuum bonding: vacuum bonding the device layer silicon and the cap layer silicon.

[0061] Step S6: Reference Figure 8 , P-type doping: The solid-state diffusion method is used to locally dope the upper surface of the cap layer silicon with P-type heavy doping to form a PN junction.

[0062] Step S7: Reference Fig. 9 , Lead hole etching: deep silicon etching is performed on the cap layer silicon, and then the oxide layer formed after oxidation treatment is removed to expose the device layer silicon at the pad position.

[0063] Step S8: Reference Fig.10, pressure sensitive membrane etching: etching the substrate layer silicon to obtain the pressure sensitive membrane.

[0064] In this embodiment, the substrate layer silicon is preferably etched to a depth of 150 microns, and the thickness of the pressure sensitive membrane is 50 microns.

[0065] Step S9: Reference Fig.11 , Glass sheet bonding: Bond the substrate layer silicon and the glass sheet, the thickness of the glass sheet is 3 mm.

[0066] Step S10, reference Fig.12 , Metallized pads: Titanium tungsten gold is deposited at the pad position of the device layer silicon and the heavily doped position of the cap layer silicon, and the titanium tungsten gold is annealed to form an ohmic contact.

[0067] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A high-precision silicon resonant pressure sensor, characterized in that: It includes a dual-mass block coupling structure; the dual-mass block coupling structure includes a first mass block and a second mass block; the first mass block is connected to the second mass block through an H-shaped coupling beam; the first mass block is externally connected to a first cantilever beam and a fourth cantilever beam, and the first cantilever beam and the fourth cantilever beam are respectively anchored to a fourth support block and a first support block; the second mass block is externally connected to a second cantilever beam and a third cantilever beam; the second cantilever beam and the third cantilever beam are respectively anchored to a support block and a support block.

2. The high-precision silicon resonant pressure sensor according to claim 1, characterized in that: The first mass block and the second mass block are symmetrically distributed on both sides of the H-shaped coupling beam.

3. The high-precision silicon resonant pressure sensor according to claim 1, characterized in that: The first driving comb teeth are arranged on the outer side of the first mass block, and the first detecting comb teeth are arranged on the inner side of the first mass block.

4. The high-precision silicon resonant pressure sensor according to claim 3, characterized in that: The second driving comb teeth are arranged on the outer side of the second mass block, and the second detecting comb teeth are arranged on the inner side of the second mass block.

5. The high-precision silicon resonant pressure sensor according to claim 4, characterized in that: The differential capacitor of the first detection comb teeth and the differential capacitor of the second detection comb teeth are both externally connected to a differential operational amplifier.

6. A manufacturing process for the high-precision silicon resonant pressure sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Substrate layer etching: using deep silicon etching to etch the silicon support column of the double-sided polished silicon wafer, and oxidizing the upper surface of the etched substrate layer; S2, device layer bonding: bonding the device layer silicon and the substrate layer silicon; S3, device layer etching: etching the device layer to form a dual-mass block coupling structure; S4, cap layer etching: using deep silicon etching to etch the cap cavity on the double-sided polished N-type silicon wafer, and oxidizing the lower surface of the etched cap layer; S5, vacuum bonding: vacuum bonding the device layer silicon and the cap layer silicon; S6, P-type doping: Use solid-state diffusion method to locally dope the upper surface of the cap layer silicon with P-type to form a PN junction; S7, lead hole etching: deep silicon etching is performed on the cap layer silicon, and then the oxide layer formed after oxidation treatment is removed to expose the device layer silicon at the pad position; S8, etching the pressure sensitive membrane: etching the substrate layer silicon to obtain the pressure sensitive membrane; S9, glass sheet bonding: bonding the substrate layer silicon and the glass sheet; S10, metallized pad: titanium tungsten gold is deposited at the pad position of the device layer silicon and the heavily doped position of the cap layer silicon, and the titanium tungsten gold is annealed to form an ohmic contact.

7. The manufacturing process of the high-precision silicon resonant pressure sensor according to claim 6, characterized in that: The thickness of the double-sided polished silicon wafer in S1 is 400 microns, and the etching depth of the silicon support column is 200 microns.

8. The manufacturing process of the high-precision silicon resonant pressure sensor according to claim 6, characterized in that: The etching depth of the cap cavity in S4 is 50 microns.

9. The manufacturing process of the high-precision silicon resonant pressure sensor according to claim 6, characterized in that: The depth of etching the substrate layer silicon in S8 is 150 microns, and the thickness of the pressure sensitive membrane is 50 microns.

10. The manufacturing process of the high-precision silicon resonant pressure sensor according to claim 6, characterized in that: The thickness of the glass sheet in the S9 is 3 mm.

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