CN118258524A - Resonant pressure sensor and preparation method thereof - Google Patents

Abstract

The invention provides a resonant pressure sensor and a preparation method thereof, comprising the following steps: providing a substrate, and forming vibration pickup resistors and driving resistors which are arranged at intervals on the upper surface layer of the substrate; forming at least one resonance structure comprising a resonance beam and a vibration gap on the upper surface layer of the substrate, wherein the resonance beam comprises a first beam, a second beam and a middle beam which are connected, the driving resistor and the resonance resistor are respectively positioned on the upper surface layers of the first beam and the second beam, and the vibration gap comprises an etching groove surrounding the resonance beam and a bottom cavity positioned below the resonance beam and communicated with the etching groove; forming a sacrificial layer covering the vibration gap opening and the upper surface of the resonant beam on the upper surface of the substrate, wherein the edge of the sacrificial layer is spaced from the vibration gap opening by a first preset distance, and a sealing shell covering the sacrificial layer; forming a groove which is opened from the bottom surface of the substrate right below the resonance structure, wherein the bottom is spaced from the bottom of the vibration gap by a second preset distance; the sealing shell and the vibration gap are surrounded to form a sealing cavity. The preparation method of the pressure sensor reduces the production cost.

Description

Resonant pressure sensor and preparation method thereof

Technical Field

The invention relates to the technical field of silicon micromechanical sensing, in particular to a resonant pressure sensor and a preparation method thereof.

Background

With the development of micro-electro-mechanical system (MEMS) sensor technology, micromachined low-voltage sensors are widely used in industries such as aerospace, wearable equipment, medical treatment, automotive electronics, and the like, due to the advantages of light weight, small volume, and the like. Currently, miniaturization, high precision and cost reduction of sensors are important developments in MEMS technology. Resonant low-voltage sensors have better performance in terms of device sensitivity, stability and accuracy than other mechanisms based low-voltage sensors, such as piezoresistive low-voltage sensors and capacitive low-voltage sensors, by allowing digital output and being less affected by ambient temperature. Therefore, the manufacturing of miniaturized, high-precision, low-cost low-pressure resonant pressure sensors will be a research hotspot.

The resonant pressure sensor operates on the principle that the resonant frequency of a semiconductor resonator is utilized, and the mechanical strain caused by pressure causes a change in the resonant frequency of the resonator, which is converted by a suitable circuit into a measurable signal output to determine the pressure. At present, the detection core component of the resonant pressure sensor mainly comprises a pressure detection sensitive film and a resonant beam. In 1992, a silicon resonant differential pressure sensor manufactured by a three-dimensional micro-machining technology and an intelligent differential pressure transmitter adopting the sensor are designed and manufactured by a Japanese cross-river motor Tokuji Saigusa and the like, the differential pressure transmitter has higher overall environment precision (T.Saigusa and H.Kawayama,"Intelligent differential pressure transmitter using micro-resonators,"in Proceedings of the 1992International Conference on Industrial Electronics,Control,Instrumentation,and Automation,San Diego,CA,USA:IEEE,1992,pp.1634–1639.doi:10.1109/IECON.1992.254354.)., the sensor eliminates the micro temperature coefficients of two resonators through differential structure design, and higher temperature stability is achieved; the resonator is sealed in the vacuum cavity to obtain a high Q value and insensitive to the pollution effect of ions and impurities, however, the sensor forms a diaphragm on the back surface of the substrate by utilizing KOH anisotropic etching, and a great amount of time is required to thin the silicon wafer in a large area and depth by utilizing KOH solution so as to reach the expected thickness of the structural beam, thereby prolonging the production period and increasing the manufacturing cost. Wang Junbo et al in the department of sciences Beijing microelectronics in 2021 designed and fabricated a resonant differential pressure sensor using bulk micromachining and silicon-on-insulator (SOI) processing technology, which could be used in the measuring range (Y.Li et al.,"A High-Sensitivity Resonant Differential Pressure Microsensor Based on Bulk Micromachining,"IEEE Sensors J.,vol.21,no.7,pp.8927–8934,Apr.2021,doi:10.1109/JSEN.2021.3051286.). of hundreds of kilopascals to fabricate pressure sensitive films using silicon Deep Reactive Ion Etching (DRIE), which shortens the processing time compared with KOH etching to fabricate films, but the fabrication of pressure sensors by this method still has the following disadvantages: firstly, the pressure sensor manufactured by the SOI processing technology has the problems of complex manufacturing flow and long production period, which is not beneficial to the reduction of the cost of a single sensor; secondly, the assembly of the resonance beam and the sensitive film is realized through alignment and anodic bonding, so that unnecessary mechanical strain is easily introduced to the device structure, and the yield and the repeatability of the device production are adversely affected; then, using SOI (silicon on insulator) technology to manufacture resistor by heavy doping, and adopting heavy doping to make heat-driven resonance beam; and the size of the film is limited by using the SOI and anode bonding process, so that the pressure sensitive film is difficult to be made into a uniform film with thinner and smaller area, which is not beneficial to miniaturization and improvement of sensitivity of the pressure sensor.

In view of the above, there is an urgent need for a method for manufacturing a resonant pressure sensor with low process cost, high sensitivity and high anti-interference capability.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a resonant pressure sensor and a method for manufacturing the same, which are used for solving the problems of high manufacturing process cost, low sensitivity and weak anti-interference capability of the resonant pressure sensor in the prior art.

To achieve the above and other related objects, the present invention provides a method for manufacturing a resonant pressure sensor, comprising the steps of:

providing a substrate, and forming at least one vibration pickup resistor and a driving resistor which is arranged at intervals with the vibration pickup resistor on the upper surface layer of the substrate;

Forming at least one resonance structure on the upper surface layer of the substrate, wherein the resonance structure comprises a resonance beam and a vibration gap, the resonance beam comprises a first beam, a second beam and a middle beam, the first beam and the second beam are arranged at intervals, the driving resistor is positioned on the upper surface layer of the first beam, the resonance resistor is positioned on the upper surface layer of the second beam, and the vibration gap comprises an etching groove surrounding the resonance beam and a bottom cavity positioned below the resonance beam and communicated with the etching groove;

Forming a sacrificial layer on the upper surface of the substrate, wherein the sacrificial layer covers the vibration gap opening and the upper surface of the resonant beam, and the edge of the sacrificial layer is spaced from the vibration gap opening by a first preset distance, and forming a sealing shell covering the exposed surface of the sacrificial layer;

forming a groove which is opened from the bottom surface of the substrate right below the resonance structure, wherein the bottom of the groove is separated from the bottom of the vibration gap by a second preset distance;

And removing the sacrificial layer, and forming a sealing cavity by surrounding the sealing shell and the vibration gap.

Optionally, the substrate comprises a monocrystalline silicon substrate.

Optionally, before forming the resonant structure, the method further includes forming a plurality of lead areas electrically connected to the driving resistor and the vibration pickup resistor, respectively.

Optionally, after the sealing cavity is formed, a step of forming a bonding pad in ohmic contact with the lead area at one end of the lead area away from the driving resistor and the vibration pickup resistor is further included.

Optionally, before forming the vibration pickup resistor, the method further comprises a step of forming a barrier layer in the substrate, wherein the upper surface of the barrier layer is coincident with the upper surface of the substrate, and the bottom of the barrier layer is not higher than the bottom of the vibration gap.

Optionally, forming the resonant structure includes the steps of: forming a patterned mask layer on the upper surface of the substrate, forming an etching groove in the substrate based on the patterned mask layer, defining a resonance beam region by the etching groove, forming a bottom cavity penetrating through the resonance beam region at the bottom of the etching groove, and taking the rest part of the resonance beam region above the bottom cavity as the resonance beam.

Optionally, the dimension of the projection of the groove in the vertical direction is not smaller than the dimension of the projection of the area where the resonant structure is located in the vertical direction.

Optionally, after forming the sealed shell, the step of forming a release hole in the sealed shell is further included before removing the sacrificial layer.

Optionally, after removing the sacrificial layer, a step of forming a vacuum sealing plug on the sealing shell to fill the release hole is further included.

The invention also provides a resonant pressure sensor, which is prepared by adopting the preparation method of the resonant pressure sensor, and comprises the following steps:

A substrate;

the vibration pickup resistor and the driving resistor are positioned on the upper surface layer of the substrate, and the vibration pickup resistor and the driving resistor are arranged at intervals;

The resonant structure is positioned on the upper surface layer of the substrate and comprises a resonant beam and a vibration gap, the resonant beam comprises a first beam, a second beam and a middle beam, the first beam and the second beam are arranged at intervals, the driving resistor is positioned on the upper surface layer of the first beam, the resonant resistor is positioned on the upper surface layer of the second beam, the vibration gap comprises an etching groove surrounding the resonant beam and a bottom cavity positioned at the bottom of the etching groove, and the bottom cavity is communicated with the etching groove;

the sealing shell covers the vibration gap opening and the upper surface of the resonant beam, and the inner side wall of the sealing shell is spaced from the vibration gap opening by a first preset distance;

the groove is positioned right below the resonance structure and is opened from the bottom surface of the substrate, and the bottom of the groove and the bottom of the vibration gap are separated by a second preset distance;

And the sealing shell and the vibration gap are surrounded to form a sealing cavity.

As described above, the resonant pressure sensor and the method for manufacturing the same of the present invention have the following beneficial effects: the substrate based on monocrystalline silicon material utilizes single-silicon single-sided silicon micromachining technology to solve the processing problem of controllable structural size of the resonant beam structure on a non-SOI silicon wafer, combines the traditional double-sided silicon micromachining technology on the basis to successfully prepare the sensitive film, the shape and size of the sensitive film are controllable, the sealing cavity surrounding the resonant structure is formed by utilizing a surface technology, and the integrated integration of a plurality of in-plane differential type resonant structures and the sealing cavity on a single chip is realized.

Drawings

Fig. 1 is a schematic flow chart of a method for manufacturing a resonant pressure sensor according to the present invention.

FIG. 2 is a schematic diagram showing the structure of the resonant pressure sensor of the present invention after forming a barrier layer.

FIG. 3 is a schematic diagram showing the structure of the resonant pressure sensor of the present invention after forming the lead resistive region.

Fig. 4 is a schematic structural diagram of the method for manufacturing the resonant pressure sensor according to the present invention after forming the mask layer and the first protection layer.

Fig. 5 is a schematic diagram showing a structure of the resonant pressure sensor according to the present invention after forming an etched groove.

Fig. 6 is a schematic diagram showing a structure of the resonant pressure sensor according to the present invention after forming the gap portion.

Fig. 7 is a schematic structural view of a resonant beam formed by the method for manufacturing a resonant pressure sensor according to the present invention.

FIG. 8 is a schematic diagram of the structure of the resonant pressure sensor of the present invention after forming a first sacrificial material layer.

Fig. 9 is a schematic diagram showing a structure of the resonant pressure sensor according to the present invention after forming a sacrificial layer.

Fig. 10 is a schematic structural view of the method for manufacturing the resonant pressure sensor of the present invention after forming the sealed housing.

Fig. 11 is a schematic diagram showing a structure of the resonant pressure sensor according to the present invention after forming grooves.

Fig. 12 is a schematic structural view of the method for manufacturing the resonant pressure sensor of the present invention after forming a vacuum sealing plug.

Fig. 13 is a schematic diagram showing a structure of a resonant pressure sensor according to the present invention after bonding pads are formed.

Fig. 14 is a schematic structural view of a resonant pressure sensor according to the present invention.

Fig. 15 is a schematic view showing a part of the structure of the resonant pressure sensor of the present invention.

Description of element reference numerals

1. Substrate and method for manufacturing the same

11. Mask layer

111. First passivation layer

112. First low stress layer

113. Second passivation layer

12. First protective layer

121. Third passivation layer

122. Second low stress layer

123. Fourth passivation layer

13. A first isolation layer

14. A second isolation layer

15. Sixth passivation layer

2. Barrier layer

21. Barrier groove

22. Insulating layer

23. Filling layer

3. Lead resistor area

4. Resonant structure

41. Resonant beam

411. First beam

412. Second beam

413. Intermediate beam

42. Vibration gap

421. Etching groove

421A second protective layer

422. Bottom cavity

423. Gap part

43. Resonance beam region

5. Sacrificial layer

51. A first sacrificial material layer

52. A second sacrificial material layer

6. Sealing shell

61. Release hole

62. Vacuum sealing plug

7. Groove

8. Sensitive film

9. Sealed cavity

10. Bonding pad

Detailed Description

Further advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure of the present invention, which is described by the following specific examples.

Please refer to fig. 1 to 15. It should be understood that the structures, proportions, sizes, etc. shown in the drawings are for illustration purposes only and should not be construed as limiting the invention to the extent that it can be practiced, since modifications, changes in the proportions, or otherwise, used in the practice of the invention, are not intended to be critical to the essential characteristics of the invention, but are intended to fall within the spirit and scope of the invention. Also, the terms such as "upper," "lower," "left," "right," "middle," and "a" and the like recited in the present specification are merely for descriptive purposes and are not intended to limit the scope of the invention, but are intended to provide relative positional changes or modifications without materially altering the technical context in which the invention may be practiced.

Example 1

The embodiment provides a method for preparing a resonant pressure sensor, as shown in fig. 1, which is a schematic flow chart of the method for preparing the resonant pressure sensor, and includes the following steps:

s1: providing a substrate, and forming at least one vibration pickup resistor and a driving resistor which is arranged at intervals with the vibration pickup resistor on the upper surface layer of the substrate;

S2: forming at least one resonance structure on the upper surface layer of the substrate, wherein the resonance structure comprises a resonance beam and a vibration gap, the resonance beam comprises a first beam, a second beam and a middle beam, the first beam and the second beam are arranged at intervals, the driving resistor is positioned on the upper surface layer of the first beam, the resonance resistor is positioned on the upper surface layer of the second beam, and the vibration gap comprises an etching groove surrounding the resonance beam and a bottom cavity positioned below the resonance beam and communicated with the etching groove;

S3: forming a sacrificial layer on the upper surface of the substrate, wherein the sacrificial layer covers the vibration gap opening and the upper surface of the resonant beam, and the edge of the sacrificial layer is spaced from the vibration gap opening by a first preset distance, and forming a sealing shell covering the exposed surface of the sacrificial layer;

s4: removing the sacrificial layer, and forming a sealing cavity by surrounding the sealing shell and the vibration gap;

S5: and forming a groove which is opened from the bottom surface of the substrate right below the resonance structure, wherein the bottom of the groove is separated from the bottom of the vibration gap by a second preset distance.

Specifically, referring to fig. 2-3, the step S1 is performed, a substrate 1 is provided, and at least one vibration pickup resistor (not shown) and a driving resistor (not shown) disposed at a distance from the vibration pickup resistor are formed on an upper surface of the substrate 1.

By way of example, the substrate 1 comprises a monocrystalline silicon substrate or other suitable substrate.

Specifically, the crystal plane of the substrate 1 is oriented (111).

Specifically, the thickness of the substrate 1 ranges from 400 μm to 500 μm. In this embodiment, the thickness of the substrate 1 is 450 μm.

As an example, as shown in fig. 2, before forming the vibration pickup resistor and the driving resistor, the method further includes a step of forming the barrier layer 2 in the substrate 1, wherein an upper surface of the barrier layer 2 coincides with an upper surface of the substrate 1, and a bottom of the barrier layer 2 is not higher than a bottom of the vibration gap 42.

As an example, forming the barrier layer 2 comprises the steps of: a patterned oxide layer (not shown) is formed on the upper surface of the substrate 1, a barrier trench 21 is formed in the substrate 1 based on the patterned oxide layer, and an insulating layer 22 and a filling layer 23 filling the barrier trench 21 are sequentially formed in the barrier trench 21 to obtain the barrier layer 2.

Specifically, the material of the oxide layer includes silicon dioxide or other suitable materials.

Specifically, the method of forming the oxide layer includes thermal oxidation or other suitable methods.

Specifically, the thickness of the oxide layer is in the range ofIn this embodiment, the oxide layer has a thickness of

Specifically, patterning the oxide layer is a conventional technical means, and will not be described herein.

Specifically, the method of forming the barrier trench 21 includes deep reactive ion etching or other suitable method.

Specifically, the method of forming the insulating layer 22 includes low pressure chemical vapor deposition or other suitable method.

Specifically, the material of the insulating layer 22 includes silicon nitride or other suitable material.

Specifically, the insulating layer 22 is formed to cover the inner wall of the barrier groove 21.

Specifically, the method of forming the filling layer 23 includes low pressure chemical vapor deposition or other suitable method.

Specifically, the material of the filling layer 23 includes polysilicon or other suitable materials.

Specifically, the barrier layer 2 is formed to have a thickness of not less than 20 μm. In this embodiment, the thickness of the barrier layer 2 is 25 μm.

In particular, in the case of satisfying the performance of the resonant pressure sensor, the number of the barrier layers 2 may be selected according to actual conditions, which is not limited herein. In this embodiment, the number of the barrier layers 2 is two.

As an example, before forming the resonant structure 4, a step of forming a plurality of lead areas electrically connected to the driving resistor and the vibration pickup resistor, respectively, is further included.

Specifically, as shown in fig. 3, to form the lead resistor area 3, the forming of the vibration pickup resistor, the driving resistor and the lead area includes the following steps: a patterned hard film layer (not shown) is formed on the upper surface of the substrate 1 to define the lead resistor area 3 where the vibration pickup resistor, the driving resistor and the lead 21 are located, and the vibration pickup resistor, the driving resistor and the lead area are formed in the lead resistor area 3.

Specifically, the method for forming the vibration pickup resistor comprises ion implantation or other suitable methods; methods of forming the drive resistor include ion implantation or other suitable methods; methods of forming the lead regions include ion implantation or other suitable methods.

Specifically, the ion implantation method forms the vibration pickup resistor, the driving resistor and the implantation ions adopted by the lead area, including boron ions or other suitable ions.

Specifically, after the vibration pickup resistor, the driving resistor and the lead area are formed by adopting boron ion implantation, the method further comprises the step of performing boron main expansion in an oxygen environment so as to repair damage of the ion implantation to a crystal lattice and activate boron ions.

Specifically, in the case of satisfying the performance of the resonant pressure sensor, the energy and concentration of ion implantation may be selected according to the actual situation, and are not limited herein.

Specifically, referring to fig. 4-7, the step S2 is performed, at least one resonant structure 4 is formed on the upper surface layer of the substrate 1, the resonant structure 4 includes a resonant beam 41 and a vibration gap 42, the resonant beam 41 includes a first beam 411, a second beam 412 and a middle beam 413 connected to the first beam 411 and the second beam 412, the driving resistor is located on the upper surface layer of the first beam 411, the resonant resistor is located on the upper surface layer of the second beam 412, and the vibration gap 42 includes an etching groove 421 surrounding the resonant beam 41 and a bottom cavity 422 located below the resonant beam 41 and in communication with the etching groove 421.

As an example, as shown in fig. 4 to 7, the structure schematic after forming the mask layer 11, the structure schematic after forming the etching groove 421, the structure schematic after forming the gap portion 423, and the structure schematic after forming the resonance beam 41, respectively, and the forming of the resonance structure 4 includes the following steps: a patterned mask layer 11 is formed on the upper surface of the substrate 1, the etching groove 421 is formed in the substrate 1 based on the patterned mask layer 11, meanwhile, the etching groove 421 defines a resonance beam region 43, the bottom cavity 422 penetrating the resonance beam region 43 is formed at the bottom of the etching groove 421, and the remaining part of the resonance beam region 43 above the bottom cavity 422 is used as the resonance beam 41.

Specifically, before forming the bottom cavity 422, a step of forming a gap portion 423 having an opening size smaller than that of the etched groove 421 from the bottom opening of the etched groove 421 is further included.

Specifically, the bottom cavity 422 is obtained by further etching the substrate 1 located under the resonance beam region 43 based on the gap portion 423.

Specifically, the mask layer 11 is formed and a first protection layer 12 is formed to cover the lower surface of the substrate 1.

Specifically, the mask layer 11 includes a first passivation layer 111, a first low stress layer 112, and a second passivation layer 113 that are sequentially stacked; the first protection layer 12 includes a third passivation layer 121, a second low stress layer 122, and a fourth passivation layer 123, which are sequentially stacked.

Specifically, the method for forming the mask layer 11 includes chemical vapor deposition, physical vapor deposition, or other suitable methods; the method of forming the first protective layer 12 includes chemical vapor deposition, physical vapor deposition, or other suitable method.

Specifically, the material of the first passivation layer 111 includes tetraethoxysilane or other suitable materials; the material of the first low stress layer 112 includes silicon nitride or other suitable material; the material of the second passivation layer 113 includes tetraethoxysilane or other suitable materials; the material of the third passivation layer 121 includes tetraethoxysilane or other suitable materials; the material of the second low stress layer 122 includes silicon nitride or other suitable material; the material of the fourth passivation layer 123 includes tetraethoxysilane or other suitable materials.

Specifically, the thickness of the first passivation layer 111 ranges fromThe first low stress layer 112 has a thickness in the range ofThe thickness of the second passivation layer 113 ranges fromThe thickness of the third passivation layer 121 ranges fromThe second low stress layer 122 has a thickness in the range ofThe fourth passivation layer 123 has a thickness in the range ofIn this embodiment, the thickness of the first passivation layer 111 isThe first low stress layer 112 has a thickness ofThe second passivation layer 113 has a thickness ofThe thickness of the third passivation layer 121 isThe second low stress layer 122 has a thickness ofThe fourth passivation layer 123 has a thickness in the range of

Specifically, the method of forming the etched trench 421 includes reactive ion etching, deep reactive ion etching, or other suitable method.

Specifically, the depth of the etched groove 421 is formed in a range of 4 μm to 8 μm. In this embodiment, the depth of the etched groove 421 is 6 μm, where the depth refers to the vertical distance between the opening of the etched groove 421 and the bottom.

Specifically, forming the gap portion 423 includes the steps of: the second protective layer 421a covering the inner wall of the etching groove 421 is formed, the second protective layer 421a located at the bottom of the etching groove 421 is removed, and the gap portion 423 communicating with the etching groove 421 is formed from the bottom opening of the etching groove 421.

Specifically, the second protective layer 421a includes a third low stress layer and a fifth passivation layer that sequentially cover the inner wall of the etched trench 421.

Specifically, the material of the third low stress layer includes silicon nitride or other suitable materials; the fifth passivation layer may be made of tetraethoxysilane or other suitable materials.

Specifically, the thickness of the third low stress layer is in the range ofThe thickness of the fifth passivation layer is in the range ofIn this embodiment, the thickness of the third low stress layer isThe fifth passivation layer 411b has a thickness of

Specifically, the method for removing the second protective layer 421a includes reactive ion etching or other suitable method.

Specifically, the method of forming the gap portion 423 includes deep reactive ion etching or other suitable method.

Specifically, the depth of the gap 423 is in the range of 2 μm to 4 μm. In the present embodiment, the depth of the gap portion 423 is 3 μm, where the depth refers to a vertical distance between the opening of the gap portion 423 and the bottom.

Specifically, the method of forming the bottom cavity 422 based on the gap portion 423 includes anisotropic wet etching or other suitable method.

Specifically, the etching solution used to form the bottom cavity 422 by anisotropic wet etching includes tetramethylammonium hydroxide, potassium hydroxide, or other suitable etching solution.

Specifically, the temperature range used to form the bottom cavity 422 using anisotropic wet etching is 70-90 ℃. In this example, the temperature used was 80 ℃.

Specifically, the removing of the mask layer 11 includes removing the first protection layer 12.

Specifically, the method for removing the mask layer 11 includes dry etching, wet etching, chemical mechanical polishing, or other suitable methods; the method of removing the first protective layer 12 includes dry etching, wet etching, chemical mechanical polishing, or other suitable methods.

Specifically, the etched trenches 421 are arranged along the <211> crystal direction.

Specifically, in the case of satisfying the performance of the resonant pressure sensor, the size of the first beam 411 may be selected according to practical situations, which is not limited herein; the dimensions of the second beam 412 may be selected according to the actual situation, and are not limited herein; the size of the intermediate beam 413 may be selected according to practical situations, and is not limited herein.

Specifically, the driving resistor and the vibration pickup resistor are respectively located on the upper surfaces of the first beam 411 and the second beam 412, and the two ends of the driving resistor and the vibration pickup resistor are respectively electrically connected with the bonding pad by using the lead area doped with boron ions with high concentration.

In particular, in the case of satisfying the performance of the resonant pressure sensor, the number of the resonant structures 3 may be selected according to the actual situation, which is not limited herein. In this embodiment, the number of the resonant structures 4 is two, and the two resonant structures 4 are arranged in parallel on the upper surface layer of the substrate 1, where the two resonant structures 4 are respectively located at two sides of the center point of the substrate 1, and the two resonant structures 4 respectively detect the tensile stress in a specific area and the compressive stress in a corresponding area on the substrate 1, so as to implement differential pressure detection output.

Specifically, the resonant structure 4 further includes a step of fixing a fixing beam (not shown) for fixing the resonant beam 41.

Specifically, referring to fig. 8-10, the step S3 is performed, a sacrificial layer 5 is formed on the upper surface of the substrate 1 to cover the opening of the vibration gap 42 and the upper surface of the resonant beam 41, and the edge of the sacrificial layer is spaced from the opening of the vibration gap 42 by a first predetermined distance, and a sealing case 6 is formed to cover the exposed surface of the sacrificial layer 5.

Specifically, as shown in fig. 8 to fig. 9, the structure schematic after the first sacrificial material layer 51 is formed and the structure schematic after the sacrificial layer 5 is formed, and the forming of the sacrificial layer 5 includes the following steps: a first sacrificial material layer 51 covering the opening of the vibration gap 42 and the upper surface of the resonant beam 41, and a second sacrificial material layer 52 covering the exposed surface of the first sacrificial material layer 51 and having an edge spaced from the sidewall of the first sacrificial material layer 51 by a third predetermined distance are sequentially formed on the upper surface of the substrate 1, so as to obtain the sacrificial layer 5, wherein the edge of the second sacrificial material layer 52 is spaced from the opening of the vibration gap 42 by the first predetermined distance.

Specifically, before forming the sacrificial layer 5, the method further includes a step of forming the first isolation layer 13 on the upper surface of the substrate 1 and forming the second isolation layer 14 on the lower surface of the substrate 1.

Specifically, the first isolation layer 13 and the first sacrificial layer 61 also fill the vibration gap 42.

Specifically, the material of the first isolation layer 13 includes silicon nitride or other suitable materials; the material of the second isolation layer 14 includes silicon nitride or other suitable material.

Specifically, the step of forming the second sacrificial material layer 52 is performed while forming the sixth passivation layer 15 covering the surface of the second isolation layer 14.

Specifically, the thickness of the first isolation layer 13 is in the range ofThe thickness of the first sacrificial material layer 51 ranges fromThe thickness of the second isolation layer 13 is in the range ofThe thickness of the second sacrificial material layer 52 ranges fromIn the present embodiment, the first isolation layer 13 has a thickness ofThe thickness of the first sacrificial material layer 51 isThe thickness of the second isolation layer 14 isThe thickness of the second sacrificial material layer 52 ranges from

Specifically, as shown in fig. 10, to form the seal housing 6, a method of forming the seal housing 6 includes chemical vapor deposition, physical vapor deposition, or other suitable method.

Specifically, the material of the sealing shell 6 includes polysilicon or other suitable materials.

Specifically, the thickness of the seal housing 6 is in the range ofIn this embodiment, the thickness of the seal housing 6 is

Specifically, referring to fig. 11, the step S5 is performed, a groove 7 is formed right under the resonant structure 4 and is opened from the bottom surface of the substrate 1, and the bottom of the groove 7 is spaced from the bottom of the vibration gap 32 by a second predetermined distance.

As an example, the dimension of the projection of the recess 7 in the vertical direction is not smaller than the dimension of the projection of the area of the resonant structure 4 in the vertical direction. The region where the resonant structure 4 is located here refers to a region where all of the resonant structures 4 formed in the resonant pressure sensor are located.

Specifically, the step of etching the second isolation layer 14 and the sixth passivation layer 15 to define the region where the groove 7 is located is further included before forming the groove 7.

Specifically, the method of removing the second isolation layer 14 includes reactive ion etching or other suitable method; the method of removing the sixth passivation layer 15 includes reactive ion etching or other suitable method.

Specifically, the substrate 1 (shown as a broken line portion in fig. 11) of the portion surrounding the resonant structure 4 remaining after the formation of the recess 7 serves as a sensitive film 8 of the resonant pressure sensor.

Specifically, the recess 7 is formed in the substrate 1 to obtain the sensitive film 8, so that the thickness and shape of the formed sensitive film 8 are controllable, the formation process of the resonant pressure sensor is simplified, and the sensitivity and anti-interference capability of the device are improved.

Specifically, as shown in fig. 11, to form the recess 7, the method of forming the recess 7 includes deep reactive ion etching or other suitable method.

Specifically, referring to fig. 12-13, the step S5 is performed to remove the sacrificial layer 5, and the seal housing 6 and the vibration gap 32 enclose a seal cavity 9.

As an example, after forming the hermetic shell 6, a step of forming a release hole 61 on the hermetic shell 6 is further included before removing the sacrificial layer 5.

Specifically, the release hole 61 is used for removing the sacrificial layer 5.

Specifically, the method for removing the sacrificial layer 5 includes dry etching or other suitable method.

Specifically, the method of forming the release hole 61 includes dry etching or other suitable method.

As an example, after the sacrificial layer 5 is removed, a step of forming a vacuum sealing plug 62 filling the release hole 61 on the sealing case 6 is further included.

Specifically, as shown in fig. 12, to form the vacuum sealing plug 62, the method of forming the vacuum sealing plug 62 includes chemical vapor deposition, physical vapor deposition, or other suitable method.

Specifically, the vacuum sealing plug 62 is made of tetraethoxysilane or other suitable materials.

Specifically, the vacuum sealing plug 62 has a thickness in the range ofIn this embodiment, the vacuum sealing plug 62 has a thickness of

In particular, the vacuum sealing plug 62 is used to seal the sealed cavity 9.

As an example, after forming the sealed cavity 9, the method further includes a step of forming a bonding pad 10 in ohmic contact with the lead area at an end of the lead area away from the driving resistor and the vibration pickup resistor.

Specifically, as shown in fig. 13, to form the bonding pad 10, a method of forming the bonding pad 10 includes magnetron sputtering or other suitable methods.

Specifically, before forming the bonding pad 10, the method further includes a step of etching the first isolation layer 13 on the upper surface of the substrate 1 to expose the external window of the bonding pad 10.

Specifically, the material of the pad 10 includes aluminum or other suitable material.

Specifically, in the case of satisfying the performance of the resonant pressure sensor, the number of pads 10 may be selected according to the actual situation, and is not limited herein.

Specifically, the method for manufacturing the resonant pressure sensor according to the embodiment is suitable for processing the pressure sensor based on the in-plane differential type resonant structure 4, and is also suitable for processing the pressure sensor based on the in-plane differential type resonant structure 4, and can be selected according to actual process requirements.

The preparation method of the resonance type pressure sensor of the embodiment is based on the substrate 1 made of monocrystalline silicon, solves the processing difficulty of controllable structural size of the resonance structure 4 on a non-SOI silicon wafer by utilizing a single-wafer single-sided silicon micromachining technology, successfully prepares the sensitive diaphragm 8 with controllable shape and thickness by combining the traditional double-sided silicon micromachining technology on the basis, and forms the sealed cavity 9 sealing the resonance structure 4 by utilizing a surface technology.

Example two

The present embodiment provides a resonant pressure sensor, as shown in fig. 14-15, which are a schematic structural diagram of the resonant pressure sensor and a schematic structural diagram of a part of the resonant pressure sensor, where the resonant pressure sensor is prepared by using the preparation method of the resonant pressure sensor in the first embodiment, and the resonant pressure sensor includes: a substrate 1, a vibration pickup resistor, a driving resistor, a resonant structure 4, a sealing shell 6, a sealing cavity 9 and a groove 7, wherein,

The vibration pickup resistor and the driving resistor are positioned on the upper surface layer of the substrate 1 and are arranged at intervals; the resonant structure 3 is located on the upper surface layer of the substrate 1, the resonant structure 4 includes a resonant beam 41 and a vibration gap 42, the resonant beam 41 includes a first beam 411, a second beam 412 and a middle beam 413 connecting the first beam 411 and the second beam 412, the driving resistor is located on the upper surface layer of the first beam 411, the resonant resistor is located on the upper surface layer of the second beam 412, the vibration gap 42 includes an etching groove 421 surrounding the resonant beam 41 and a bottom cavity 422 located at the bottom of the etching groove 421, and the bottom cavity 422 is communicated with the etching groove 421;

the sealing shell 6 covers the opening of the vibration gap 42 and the upper surface of the resonant beam 41, and the inner side wall of the sealing shell 6 is spaced from the opening of the vibration gap 321 by a first preset distance; the sealing shell 6 and the vibration gap 42 are surrounded to form a sealing cavity 9; the groove 7 is located right below the resonant structure 4 and is opened from the bottom surface of the substrate 1, and the bottom of the groove 7 is spaced from the bottom of the vibration gap by a second preset distance.

Specifically, the resonant pressure sensor further comprises a barrier layer 2.

Specifically, the blocking layer 2 is configured to block excessive vibration deformation of the resonant beam 41 in the vibration gap 42.

Specifically, the resonant pressure sensor further comprises a plurality of lead areas which are respectively and electrically connected with the driving resistor and the vibration pickup resistor.

Specifically, the bonding pad 10 is electrically connected to the resonant beam 41 through the lead area, the vibration pickup resistor and the driving resistor, and is used for transmitting and detecting vibration excitation and vibration pickup signals of the resonant beam 41.

Specifically, the substrate 1, which is the part surrounding the resonant structure 4 remaining after the formation of the recess 7, acts as a sensitive membrane 8 of the resonant pressure sensor.

Specifically, the sealing shell 6 is further provided with a release hole 61 and a vacuum sealing plug 62 filling the release hole 61.

Specifically, a fixing beam (not shown) for fixing the resonance beam 41 is also formed in the resonance structure 4.

The resonant pressure sensor of this embodiment is manufactured by the manufacturing method of the resonant pressure sensor of the first embodiment, and the resonant structure 4, the sealed cavity 9 and the sensitive film 8 are integrally formed by the substrate 1 based on monocrystalline silicon, so that compared with the conventional process of manufacturing the resonant pressure sensor by using an expensive SOI silicon wafer and bonding technology, the size of a sensor chip is effectively reduced, and the performance of a device is improved.

In summary, the resonant pressure sensor and the preparation method thereof of the invention are based on the substrate made of monocrystalline silicon, the processing difficulty of controllable structural dimension of the resonant beam structure on the non-SOI silicon wafer is solved by utilizing the single-silicon single-sided silicon micromachining technology, the sensitive film is successfully prepared by combining the traditional double-sided silicon micromachining technology, the shape and dimension of the sensitive film are controllable, the sealed cavity surrounding the resonant structure is formed by utilizing the surface technology, the integrated integration of the in-plane differential resonant structure and the sealed cavity on the single chip is realized, and compared with the technology of the resonant pressure sensor structure prepared by combining the expensive SOI silicon wafer with the bonding technology, the size of the sensor chip is effectively reduced, the technological process is simplified, the technological cost is reduced, and the sensitivity and the anti-interference capability of the resonant pressure sensor are improved. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (10)

1. The preparation method of the resonant pressure sensor is characterized by comprising the following steps of:

providing a substrate, and forming at least one vibration pickup resistor and a driving resistor which is arranged at intervals with the vibration pickup resistor on the upper surface layer of the substrate;

Forming at least one resonance structure on the upper surface layer of the substrate, wherein the resonance structure comprises a resonance beam and a vibration gap, the resonance beam comprises a first beam, a second beam and a middle beam, the first beam and the second beam are arranged at intervals, the driving resistor is positioned on the upper surface layer of the first beam, the resonance resistor is positioned on the upper surface layer of the second beam, and the vibration gap comprises an etching groove surrounding the resonance beam and a bottom cavity positioned below the resonance beam and communicated with the etching groove;

Forming a sacrificial layer on the upper surface of the substrate, wherein the sacrificial layer covers the vibration gap opening and the upper surface of the resonant beam, and the edge of the sacrificial layer is spaced from the vibration gap opening by a first preset distance, and forming a sealing shell covering the exposed surface of the sacrificial layer;

forming a groove which is opened from the bottom surface of the substrate right below the resonance structure, wherein the bottom of the groove is separated from the bottom of the vibration gap by a second preset distance;

And removing the sacrificial layer, and forming a sealing cavity by surrounding the sealing shell and the vibration gap.

2. The method of manufacturing a resonant pressure sensor of claim 1, wherein: the substrate comprises a monocrystalline silicon substrate.

3. The method of manufacturing a resonant pressure sensor of claim 1, wherein: before forming the resonance structure, the method further comprises the step of forming a plurality of lead areas which are respectively and electrically connected with the driving resistor and the vibration pickup resistor.

4. A method of manufacturing a resonant pressure sensor according to claim 3, characterized in that: after the sealed cavity is formed, the method further comprises the step of forming a bonding pad in ohmic contact with the lead area at one end, far away from the driving resistor and the vibration pickup resistor, of the lead area.

5. The method of manufacturing a resonant pressure sensor of claim 1, wherein: before forming the vibration pickup resistor and the driving resistor, the method further comprises the step of forming a barrier layer in the substrate, wherein the upper surface of the barrier layer is overlapped with the upper surface of the substrate, and the bottom of the barrier layer is not higher than the bottom of the vibration gap.

6. The method of manufacturing a resonant pressure sensor of claim 1, wherein: forming the resonant structure comprises the steps of: forming a patterned mask layer on the upper surface of the substrate, forming an etching groove in the substrate based on the patterned mask layer, defining a resonance beam region by the etching groove, forming a bottom cavity penetrating through the resonance beam region at the bottom of the etching groove, and taking the rest part of the resonance beam region above the bottom cavity as the resonance beam.

7. The method of manufacturing a resonant pressure sensor of claim 1, wherein: the projected size of the groove in the vertical direction is not smaller than the projected size of the area where the resonant structure is located in the vertical direction.

8. The method of manufacturing a resonant pressure sensor of claim 1, wherein: after the sealed shell is formed, the step of forming a release hole on the sealed shell is further included before the sacrificial layer is removed.

9. The method of manufacturing a resonant pressure sensor of claim 8, wherein: after the sacrificial layer is removed, the method further comprises the step of forming a vacuum sealing plug on the sealing shell to fill the release hole.

10. A resonant pressure sensor, wherein the resonant pressure sensor is prepared by the method for preparing the resonant pressure sensor according to any one of claims 1 to 9, and comprises:

A substrate;

the vibration pickup resistor and the driving resistor are positioned on the upper surface layer of the substrate, and the vibration pickup resistor and the driving resistor are arranged at intervals;

The resonant structure is positioned on the upper surface layer of the substrate and comprises a resonant beam and a vibration gap, the resonant beam comprises a first beam, a second beam and a middle beam, the first beam and the second beam are arranged at intervals, the driving resistor is positioned on the upper surface layer of the first beam, the resonant resistor is positioned on the upper surface layer of the second beam, the vibration gap comprises an etching groove surrounding the resonant beam and a bottom cavity positioned at the bottom of the etching groove, and the bottom cavity is communicated with the etching groove;

the sealing shell covers the vibration gap opening and the upper surface of the resonant beam, and the inner side wall of the sealing shell is spaced from the vibration gap opening by a first preset distance;

the groove is positioned right below the resonance structure and is opened from the bottom surface of the substrate, and the bottom of the groove and the bottom of the vibration gap are separated by a second preset distance;

And the sealing shell and the vibration gap are surrounded to form a sealing cavity.