A MEMS pressure sensor chip and a preparation method thereof

Abstract

The application discloses a MEMS pressure sensor chip and a preparation method thereof, and belongs to the technical field of pressure sensors.The MEMS pressure sensor chip comprises a chip substrate layer, an acceleration sensitive layer is bonded on the chip substrate layer, and the acceleration sensitive layer and the chip substrate layer form an intermediate bonding body; a pressure sensitive layer is arranged on the top of the intermediate bonding body; a second electrode area is arranged on the chip substrate layer, an acceleration sensitive diaphragm and a first electrode area are arranged on the acceleration sensitive layer, and a pressure sensitive diaphragm is arranged on the pressure sensitive layer; the second electrode area and the first electrode area form a variable capacitance structure; the MEMS pressure sensor chip in the application adopts a double-layer sensitive diaphragm design, improves the output precision of a silicon piezoresistive pressure sensor, realizes integrated design of pressure testing and acceleration testing, forms integrated packaging, can reduce the occupied space and the number of use of the sensor, and has high economic value.

Description

Technical Field

[0001] This invention belongs to the field of pressure sensor technology, specifically relating to a MEMS pressure sensor chip and its fabrication method. Background Technology

[0002] Pressure sensors made using the piezoresistive effect of semiconductor material (silicon) are called piezoresistive pressure sensors. They employ semiconductor processes to form piezoresistive strips on a silicon substrate, which are then arranged in a Wheatstone bridge. Under pressure, the bridge outputs a signal, converting the pressure signal into an electrical signal, thus enabling pressure measurement. These sensors are characterized by high frequency response, good stability, small size, and high accuracy, and are widely used in aerospace, meteorological measurement, petrochemical, and other fields.

[0003] Currently, the sensitive diaphragm structures used in silicon piezoresistive pressure sensors mainly include flat diaphragm and island diaphragm structures. Flat diaphragm structures are simple and easy to manufacture, primarily used for medium to high measurement ranges. However, to improve sensor sensitivity, the thickness of the sensitive diaphragm must be sacrificed. This results in greater deformation of the sensitive diaphragm under the same external pressure, leading to a sharp increase in nonlinearity and decreased stability. Compared to flat diaphragm structures, island diaphragm structures can significantly reduce central deflection and nonlinear error while maintaining high sensitivity. However, for island diaphragm structures, the central silicon island is equivalent to a mass block, making it highly susceptible to acceleration. When subjected to external acceleration impacts, the silicon island generates additional stress on the sensitive diaphragm, causing unnecessary electrical signal output and resulting in decreased sensor measurement accuracy. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a MEMS pressure sensor chip and its fabrication method, which solves the problem that current silicon piezoresistive pressure sensors, due to their island membrane structure, are greatly affected by acceleration, thus reducing the sensor's measurement accuracy.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] A MEMS pressure sensor chip is provided, which includes a chip substrate layer, an acceleration-sensitive layer bonded on the chip substrate layer, and an intermediate bond between the acceleration-sensitive layer and the chip substrate layer; a pressure-sensitive layer is disposed on the top of the intermediate bond.

[0007] A first vacuum cavity is provided between the acceleration-sensitive layer and the chip substrate; a second vacuum cavity is provided between the pressure-sensitive layer and the intermediate bond;

[0008] An acceleration-sensitive diaphragm is disposed on the acceleration-sensitive layer, and a first mass block located in the first vacuum cavity and multiple first piezoresistive strips and a first electrode area are disposed on the acceleration-sensitive diaphragm.

[0009] A pressure-sensitive diaphragm is disposed on the pressure-sensitive layer, and a second mass block and multiple second piezoresistive strips are disposed on the pressure-sensitive diaphragm; the second mass block is located inside the second vacuum chamber;

[0010] A second electrode region is provided on the chip substrate layer;

[0011] Multiple first piezoresistive strips, a first electrode region, multiple second piezoresistive strips, and a second electrode region are all electrically connected to an external processor via metal leads and metal pads; metal pads are provided on the chip substrate, acceleration-sensitive layer, and pressure-sensitive layer; the second electrode region and the first electrode region form a variable capacitor structure.

[0012] The basic principle of a MEMS pressure sensor chip in this solution is as follows: By setting an acceleration-sensitive layer and a pressure-sensitive layer on the chip substrate, the pressure-sensitive layer detects the pressure change felt by the sensitive diaphragm through the silicon piezoresistive effect and outputs the signal to the processor. After data compensation, a pressure signal is generated for output. The acceleration-sensitive layer uses a variable capacitor structure to convert the received acceleration change into an independent acceleration signal output under acceleration and impact conditions. Usually, the acceleration experienced by the sensor changes during its movement, which generates additional stress output and reduces the test accuracy. By monitoring this acceleration in real time, the signal output of the pressure sensor can be compensated in real time to improve the sensor accuracy. At the same time, the dual-layer composite structure design of the acceleration-sensitive layer and the pressure-sensitive layer realizes the integration of pressure and acceleration parameter testing, reduces the number of sensors used, saves equipment space, and has high economic benefits.

[0013] Furthermore, the acceleration-sensitive diaphragm is provided with four first piezoresistive strips connected in parallel, and the four first piezoresistive strips correspond to resistors R5, R6, R7 and R8 respectively.

[0014] Furthermore, the pressure-sensitive diaphragm is provided with four second piezoresistive strips connected in parallel, and the four second piezoresistive strips correspond to resistors R1, R2, R3 and R4 respectively.

[0015] Furthermore, the pressure-sensitive diaphragm and the acceleration-sensitive diaphragm have the same length, width, and thickness; the first mass block and the second mass block have the same length, width, and thickness; and the first piezoresistive strip and the second piezoresistive strip have the same size and doping concentration.

[0016] This solution also provides a method for fabricating a MEMS pressure sensor chip, which includes the following steps:

[0017] S1. Preparation of pressure-sensitive layer: Select a silicon substrate of a predetermined thickness and use a doping process to process a predetermined number of second piezoresistive strips on the front side of the silicon substrate.

[0018] Metal leads and metal pads are formed on a silicon substrate using magnetron sputtering, and a second piezoresistive strip is connected to the metal pads.

[0019] A back cavity and a second mass block are etched on the back side of a silicon substrate using a wet etching process. The area etched on the back side of the silicon substrate is a pressure-sensitive film, and a pressure-sensitive layer is prepared for backup.

[0020] S2. Preparation of acceleration-sensitive layer: Select a silicon substrate of a predetermined thickness and use a doping process to process a predetermined number of first piezoresistive strips on the front side of the silicon substrate.

[0021] A first electrode region is formed on a silicon substrate using magnetron sputtering or chemical vapor deposition. Metal leads and metal pads are formed on the silicon substrate using magnetron sputtering, and the first piezoresistive strip and the first electrode region are connected to the metal pads.

[0022] A back cavity and a first mass block are etched on the back side of a silicon substrate using a wet etching process. The etched area on the back side of the silicon substrate is an acceleration-sensitive film, and an acceleration-sensitive layer is prepared for backup.

[0023] S3. Fabrication of chip substrate: Select a silicon substrate of a predetermined thickness, and form a second electrode region on the silicon substrate using magnetron sputtering or chemical vapor deposition. Then, form metal leads and metal pads using magnetron sputtering and connect the second electrode region to the metal pads; the resulting chip substrate is then prepared for later use.

[0024] S4. Fabrication of MEMS pressure sensor chip: The acceleration-sensitive layer and the chip substrate are bonded together using a vacuum bonding process at a temperature of 1100℃ and an axial pressure of 50MPa for 3 hours to form an intermediate bond. Then, the pressure-sensitive layer and the intermediate bond are bonded together again using a vacuum bonding process to form a MEMS pressure sensor chip.

[0025] Furthermore, the doping concentration of the first and second piezoresistive strips is 1×10⁻⁶. 15 / cm 3 ~5×10 18 / cm 3 .

[0026] Furthermore, the materials used in the first and second electrode regions can be metallic materials such as aluminum and tantalum, or novel thin film materials such as graphene and 1T-MoS2. The aluminum and tantalum materials can be prepared using magnetron sputtering, while the novel thin film materials can be prepared using chemical vapor deposition.

[0027] The beneficial effects of this invention are as follows: Compared with the prior art, the MEMS pressure sensor chip of this invention adopts a double-layer sensitive diaphragm design. This design offers the following advantages: on the one hand, it detects pressure changes sensed by the sensitive diaphragm through the silicon piezoresistive effect; on the other hand, the lower sensitive diaphragm utilizes the capacitance testing principle to detect the electrical signal output of the island membrane structure under acceleration and impact conditions. This structural design of the MEMS pressure sensor chip in this invention achieves two major technical effects: First, it improves the output accuracy of the silicon piezoresistive pressure sensor. Typically, during sensor movement, the acceleration it experiences changes, generating additional stress output and reducing test accuracy. By monitoring this acceleration in real time, the signal output of the pressure sensor can be compensated in real time to improve sensor accuracy. Second, the composite structure design of the upper and lower sensitive diaphragms integrates the testing of both pressure and acceleration parameters, reducing the number of sensors used, saving equipment space, and resulting in higher economic benefits. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of a MEMS pressure sensor chip.

[0029] Figure 2 This is a schematic diagram of the multilayer structure of a MEMS pressure sensor chip.

[0030] Figure 3 This is a schematic diagram of the circuit connection of a MEMS pressure sensor chip.

[0031] The components are as follows: 1. Chip substrate; 2. Acceleration-sensitive layer; 3. Intermediate bond; 4. Pressure-sensitive layer; 5. First vacuum chamber; 6. Second vacuum chamber; 7. Acceleration-sensitive diaphragm; 8. First mass block; 9. First piezoresistive strip; 10. First electrode area; 11. Pressure-sensitive diaphragm; 12. Second mass block; 13. Second piezoresistive strip; 14. Metal pad; 15. External processor; 16. Variable capacitor structure; 17. Second electrode area. Detailed Implementation

[0032] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0033] like Figures 1-3As shown, the present invention provides a MEMS pressure sensor chip, which includes a chip substrate layer 1, an acceleration sensitive layer 2 bonded on the chip substrate layer 1, the acceleration sensitive layer 2 and the chip substrate layer 1 forming an intermediate bond 3; a pressure sensitive layer 4 is disposed on the top of the intermediate bond 3.

[0034] A first vacuum chamber 5 is provided between the acceleration-sensitive layer 2 and the chip substrate layer 1; a second vacuum chamber 6 is provided between the pressure-sensitive layer 4 and the intermediate bond 3.

[0035] An acceleration-sensitive diaphragm 7 is disposed on the acceleration-sensitive layer 2. The acceleration-sensitive diaphragm 7 is provided with a first mass block 8 located in the first vacuum cavity 5, a plurality of first piezoresistive strips 9 and a first electrode area 10 on the acceleration-sensitive diaphragm 7.

[0036] A pressure-sensitive diaphragm 11 is provided on the pressure-sensitive layer 4, and a second mass block 12 and a plurality of second pressure resistance strips 13 are provided on the pressure-sensitive diaphragm 11; the second mass block 12 is located in the second vacuum chamber 6.

[0037] A second electrode region 17 is provided on the chip substrate layer 1.

[0038] Multiple first piezoresistive strips 9, first electrode area 10, multiple second piezoresistive strips 13, and second electrode area 17 are all electrically connected to the external processor 15 through metal leads and metal pads 14; multiple metal pads 14 are provided on the chip substrate layer 1, acceleration sensitive layer 2, and pressure sensitive layer 4, and the leads are connected to the external circuit through the metal pads 14 to form a closed loop by wire bonding. The input voltage of the pressure sensitive layer 4 and the acceleration sensitive layer 2 should be consistent. The output voltage is compensated after being processed by the circuit, and finally output as a compensated pressure signal.

[0039] like Figure 2 and Figure 3 As shown, the second electrode region 17 and the first electrode region 10 form a variable capacitor structure 16. The variable capacitor structure 16 is independently connected to the external processor 15. After the external processor 15 detects the capacitance, the capacitor output is converted into an acceleration value, and the output is an acceleration signal.

[0040] Specifically, such as Figure 2 As shown, the acceleration-sensitive diaphragm 7 is provided with four first piezoresistive strips 9 connected in parallel, and the four first piezoresistive strips 9 correspond to resistors R5, R6, R7 and R8 respectively.

[0041] The pressure-sensitive diaphragm 11 is provided with four parallel second piezoresistive strips 13, which correspond to resistors R1, R2, R3 and R4 respectively.

[0042] The pressure-sensitive diaphragm 11 has the same length, width, and thickness as the acceleration-sensitive diaphragm 7; the first mass block 8 and the second mass block 12 have the same length, width, and thickness; and the first piezoresistive strip 9 and the second piezoresistive strip 13 have the same size and doping concentration.

[0043] By setting an acceleration-sensitive layer 2 and a pressure-sensitive layer 4 on the chip substrate layer 1, the pressure-sensitive layer 4 detects the pressure change felt by the sensitive diaphragm through the silicon piezoresistive effect and outputs the signal to the processor. After data compensation, a pressure signal is generated for output. The acceleration-sensitive layer 2 uses a variable capacitor structure 16 to convert the received acceleration change into an independent acceleration signal output under acceleration and impact conditions. Usually, the acceleration experienced by the sensor changes during the movement process. This acceleration will generate additional stress output, reducing the test accuracy. By monitoring this acceleration in real time, the signal output of the pressure sensor can be compensated in real time to improve the sensor accuracy. At the same time, the dual-layer composite structure design of the acceleration-sensitive layer 2 and the pressure-sensitive layer 4 realizes the integration of pressure and acceleration parameter testing, reduces the number of sensors used, saves equipment space, and has high economic benefits.

[0044] This invention also provides a method for fabricating a MEMS pressure sensor chip, which includes the following steps:

[0045] S1. Preparation of pressure-sensitive layer 4: Select a silicon substrate of a preset thickness and use a doping process to process a preset number of second piezoresistive strips 13 on the front side of the silicon substrate.

[0046] Metal leads and metal pads 14 are formed on a silicon substrate using magnetron sputtering, and the second piezoresistive strip 13 is connected to the metal pads 14.

[0047] A back cavity and a second mass block 12 are etched on the back side of a silicon substrate using a wet etching process. The area etched on the back side of the silicon substrate is a pressure-sensitive film 11, and a pressure-sensitive layer 4 is prepared for backup.

[0048] S2. Preparation of acceleration-sensitive layer 2: Select a silicon substrate of a predetermined thickness and use a doping process to process a predetermined number of first piezoresistive strips 9 on the front side of the silicon substrate.

[0049] A first electrode region 10 is formed on a silicon substrate using magnetron sputtering or chemical vapor deposition. Metal leads and metal pads 14 are formed on the silicon substrate using magnetron sputtering, and the first piezoresistive strip 9 and the first electrode region 10 are connected to the metal pads 14.

[0050] A back cavity and a first mass block 8 are etched on the back side of a silicon substrate using a wet etching process. The area etched on the back side of the silicon substrate is an acceleration-sensitive film 7, and an acceleration-sensitive layer 2 is prepared for backup.

[0051] S3. Fabrication of chip substrate 1: Select a silicon substrate of a predetermined thickness; form a second electrode region 17 on the silicon substrate using magnetron sputtering or chemical vapor deposition; form metal leads and metal pads 14 using magnetron sputtering; and connect the second electrode region 17 to the metal pads 14; thus, prepare chip substrate 1 for later use.

[0052] S4. Fabrication of MEMS pressure sensor chip: The acceleration sensitive layer 2 and the chip substrate layer 1 are bonded to each other at a temperature of 1100℃ and an axial pressure of 50MPa for 3 hours using a vacuum bonding process to form an intermediate bond 3. Then, the pressure sensitive layer 4 and the intermediate bond 3 are bonded to each other again using a vacuum bonding process to form a MEMS pressure sensor chip.

[0053] Specifically, the first piezoresistive strip 9 and the second piezoresistive strip 13 have the same doping concentration, both being 1×10⁻⁶. 15 / cm 3 ~5×10 18 / cm 3 .

[0054] The materials used in the first electrode region and the second electrode region can be metallic materials such as aluminum and tantalum, or novel thin film materials such as graphene and 1T-MoS2. The metallic aluminum and tantalum can be prepared by magnetron sputtering, and the novel thin film materials can be prepared by chemical vapor deposition.

[0055] The MEMS pressure sensor chip is fabricated using the above method. The signal output of the acceleration sensitive layer 2 can be independently connected to the data processor to realize the independent output of the acceleration signal. This further realizes the integrated design of pressure testing and acceleration testing, forming an integrated package, which can reduce the space occupied by the sensor and the number of sensors used, and has high economic value.

Claims

1. A MEMS pressure sensor chip, characterized in that, The chip includes a chip substrate layer, on which an acceleration-sensitive layer is bonded, and the acceleration-sensitive layer and the chip substrate layer form an intermediate bond; a pressure-sensitive layer is disposed on the top of the intermediate bond; A first vacuum cavity is provided between the acceleration-sensitive layer and the chip substrate; a second vacuum cavity is provided between the pressure-sensitive layer and the intermediate bond; An acceleration-sensitive membrane is disposed on the acceleration-sensitive layer, and a plurality of first piezoresistive strips, a first electrode area, and a first mass block located in the first vacuum cavity are disposed on the acceleration-sensitive membrane. A pressure-sensitive diaphragm is disposed on the pressure-sensitive layer, and a second mass block and a plurality of second piezoresistive strips are disposed on the pressure-sensitive diaphragm; the second mass block is located inside the second vacuum cavity; A second electrode region is provided on the chip substrate layer; Multiple first piezoresistive strips, a first electrode region, multiple second piezoresistive strips, and a second electrode region are all electrically connected to an external processor via metal leads and metal pads; the metal pads are provided on the chip substrate, acceleration-sensitive layer, and pressure-sensitive layer; the second electrode region and the first electrode region form a variable capacitor structure.

2. The MEMS pressure sensor chip according to claim 1, characterized in that, The acceleration-sensitive diaphragm has four first piezoresistive strips connected in parallel, and the four first piezoresistive strips correspond to resistors R5, R6, R7 and R8 respectively.

3. The MEMS pressure sensor chip according to claim 1, characterized in that, The pressure-sensitive diaphragm is provided with four second piezoresistive strips connected in parallel, and the four second piezoresistive strips correspond to resistors R1, R2, R3 and R4 respectively.

4. The MEMS pressure sensor chip according to claim 1, characterized in that, The pressure-sensitive diaphragm and the acceleration-sensitive diaphragm have the same length, width, and thickness; the first mass block and the second mass block have the same length, width, and thickness; the first piezoresistive strip and the second piezoresistive strip have the same size and doping concentration.

5. A method for fabricating a MEMS pressure sensor chip according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Preparation of pressure-sensitive layer: Select a silicon substrate of a predetermined thickness and use a doping process to process a predetermined number of second piezoresistive strips on the front side of the silicon substrate. Metal leads and metal pads are formed on a silicon substrate using magnetron sputtering, and a second piezoresistive strip is connected to the metal pads. A back cavity and a second mass block are etched on the back side of a silicon substrate using a wet etching process. The area etched on the back side of the silicon substrate is a pressure-sensitive film, and a pressure-sensitive layer is prepared for backup. S2. Preparation of acceleration-sensitive layer: Select a silicon substrate of a predetermined thickness and use a doping process to process a predetermined number of first piezoresistive strips on the front side of the silicon substrate. A first electrode region is formed on a silicon substrate using magnetron sputtering or chemical vapor deposition. Metal leads and metal pads are formed on the silicon substrate using magnetron sputtering, and the first piezoresistive strip and the first electrode region are connected to the metal pads. A back cavity and a first mass block are etched on the back side of a silicon substrate using a wet etching process. The etched area on the back side of the silicon substrate is an acceleration-sensitive film, and an acceleration-sensitive layer is prepared for backup. S3. Fabrication of chip substrate: Select a silicon substrate of a predetermined thickness, and form a second electrode region on the silicon substrate using magnetron sputtering or chemical vapor deposition. Then, form metal leads and metal pads using magnetron sputtering and connect the second electrode region to the metal pads; the resulting chip substrate is then prepared for later use. S4. Fabrication of MEMS pressure sensor chip: The acceleration-sensitive layer and the chip substrate are bonded together using a vacuum bonding process at a temperature of 1100℃ and an axial pressure of 50MPa for 3 hours to form an intermediate bond. Then, the pressure-sensitive layer and the intermediate bond are bonded together again using a vacuum bonding process to form a MEMS pressure sensor chip.

6. The method for fabricating a MEMS pressure sensor chip according to claim 5, characterized in that, The doping concentration of the first and second piezoresistive strips is 1×10⁻⁶. 15 / cm 3 ~5×10 18 / cm 3 .

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