CN114061797B - MEMS piezoresistive pressure sensor with double-bridge structure and preparation method thereof - Google Patents
MEMS piezoresistive pressure sensor with double-bridge structure and preparation method thereof Download PDFInfo
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- CN114061797B CN114061797B CN202111361809.3A CN202111361809A CN114061797B CN 114061797 B CN114061797 B CN 114061797B CN 202111361809 A CN202111361809 A CN 202111361809A CN 114061797 B CN114061797 B CN 114061797B
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- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000002184 metal Substances 0.000 claims abstract description 29
- 229910052751 metal Inorganic materials 0.000 claims abstract description 29
- 239000000758 substrate Substances 0.000 claims description 82
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 20
- 238000011049 filling Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 11
- 238000001259 photo etching Methods 0.000 claims description 10
- 235000012239 silicon dioxide Nutrition 0.000 claims description 10
- 239000000377 silicon dioxide Substances 0.000 claims description 10
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 9
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000000206 photolithography Methods 0.000 claims description 7
- 238000001020 plasma etching Methods 0.000 claims description 7
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 6
- 229910052796 boron Inorganic materials 0.000 claims description 6
- 238000005468 ion implantation Methods 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 5
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 4
- 238000000708 deep reactive-ion etching Methods 0.000 claims description 4
- 229910052737 gold Inorganic materials 0.000 claims description 4
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 3
- 230000004888 barrier function Effects 0.000 claims description 3
- 238000009713 electroplating Methods 0.000 claims description 3
- 238000005530 etching Methods 0.000 claims description 3
- 230000003647 oxidation Effects 0.000 claims description 3
- 238000007254 oxidation reaction Methods 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 238000007517 polishing process Methods 0.000 claims description 2
- 238000001459 lithography Methods 0.000 claims 1
- 230000035945 sensitivity Effects 0.000 abstract description 6
- 230000010354 integration Effects 0.000 abstract description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 230000009977 dual effect Effects 0.000 description 14
- 230000008569 process Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000002955 isolation Methods 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
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- 230000008092 positive effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/06—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of piezo-resistive devices
Abstract
The invention discloses a MEMS piezoresistive pressure sensor with a double-bridge structure and a preparation method thereof, wherein four piezoresistors are respectively prepared on the upper surface and the lower surface of a sensitive film, and the piezoresistors on the upper surface and the lower surface are respectively arranged opposite to each other and are mutually orthogonally distributed; the four piezoresistors on the same surface are respectively opposite to the center positions of the edges of the sensitive film. Two ends of the four piezoresistors on the lower surface of the sensitive film are respectively and electrically connected with the electrode layer on the upper surface of the structure through metal leads, and the metal leads are provided with insulating layers. The upper and lower piezoresistors form two sets of wheatstone bridges. The invention effectively improves the sensitivity of the sensor on the premise of not reducing the thickness of the sensitive film of the sensor and not increasing the area of the sensitive film of the sensor, is beneficial to improving the reliability of the sensor, improves the integration level of the sensor, reduces the area and the cost of the sensor, and ensures that the accuracy of the sensor is not affected by simple wiring.
Description
Technical Field
The invention relates to a MEMS (Micro-Electro-Mechanical System ) piezoresistive pressure sensor and a preparation method thereof.
Background
The MEMS piezoresistive pressure sensor utilizes the piezoresistive effect of semiconductor materials, and utilizes the piezoresistors to form a Wheatstone bridge to convert ambient pressure into an electric signal so as to realize pressure measurement. Compared with other types of MEMS pressure sensors such as capacitive pressure sensors, piezoelectric pressure sensors and the like, the MEMS piezoresistive pressure sensors have good linearity and reliability, and therefore, the MEMS piezoresistive pressure sensors are widely applied to the fields of aerospace, industrial control, environmental monitoring, medical electronics and the like. The current common MEMS piezoresistive pressure sensor mainly takes a sensitive film structure, and piezoresistors are distributed on the surface of the film. In order to improve the sensitivity of the sensor, the thickness of the sensitive film is designed to be thinner and the area is designed to be larger and larger, so that larger deformation and stress are ensured to be obtained under the same pressure condition, and the resistance change and the electrical output of the piezoresistor are further increased. However, reducing the thickness of the sensitive film and increasing the area of the sensitive film reduces the measuring range of the sensor, reduces the service life and reliability of the sensor, and reduces the integration level of the sensor and increases the cost of the sensor. Besides the problems, the interconnection lines are required to be used for connecting the piezoresistors to form a Wheatstone bridge, the existing interconnection lines are complicated to arrange, the stress distribution on the surface of the sensitive film can be influenced, the accuracy of the sensor is influenced, and in addition, the complexity of the interconnection line arrangement can be obviously improved along with the increase of the number of the piezoresistors.
Disclosure of Invention
The invention aims to: aiming at the prior art, the MEMS piezoresistive pressure sensor with the double-bridge structure and the preparation method thereof are provided, and the sensitivity and the precision of the MEMS piezoresistive pressure sensor are effectively improved on the premise of guaranteeing the measuring range and the reliability of the sensor.
The technical scheme is as follows: the MEMS piezoresistive pressure sensor with the double-bridge structure comprises a first substrate, wherein a second substrate is arranged below the first substrate, a cavity is arranged in the center of the upper surface of the second substrate, and a sensitive film is formed on the part of the first substrate which is aligned above the cavity; four first piezoresistors are arranged on the lower surface of the first substrate, the four first piezoresistors are respectively opposite to the center positions of the four edges of the cavity, and the arrangement directions of the four first piezoresistors are consistent; four second piezoresistors are arranged on the upper surface of the first substrate, the four second piezoresistors are respectively opposite to the four first piezoresistors on the lower surface along the thickness direction of the sensitive film, and the arrangement direction of the four second piezoresistors is respectively orthogonal with the first piezoresistors; the upper surface of the first substrate is provided with an electrode layer, two ends of the four second piezoresistors are respectively and electrically connected with the corresponding electrode layers, two ends of the four first piezoresistors are respectively and electrically connected with the corresponding electrode layers through metal leads, and the metal leads are provided with insulating layers; four first piezoresistors positioned on the lower surface of the first substrate form a first Wheatstone bridge, and four second piezoresistors positioned on the upper surface of the first substrate form a second Wheatstone bridge.
Further, the metal lead is formed by connecting a lead layer below the first substrate and a metal filling layer vertically penetrating through the first substrate.
Further, the upper surface of the first substrate is also covered with an insulating layer.
Further, the thickness and the material of the insulating layer between the lead layer and the first substrate are the same as those of the insulating layer on the upper surface of the first substrate.
The preparation method of the MEMS piezoresistive pressure sensor with the double-bridge structure comprises the following steps:
step 1: selecting an N-type (100) silicon wafer as a first substrate;
step 2: forming eight blind holes in the first substrate by photoetching and deep reactive ion etching;
step 3: preparing a layer of silicon dioxide on the inner surface of the blind hole as a first insulating layer by thermal oxidation, and preparing a layer of silicon dioxide on the upper surface of the first substrate as a second insulating layer;
step 4: etching a piezoresistor area and an anode bonding area on the second insulating layer through photoetching and reactive ion etching, and completing preparation of four first piezoresistors in the piezoresistor area through boron ion implantation;
step 5: preparing Ti and Cu on the first insulating layer in each blind hole by magnetron sputtering to serve as a barrier layer and a seed layer respectively, and filling the blind holes by electroplating Cu to form a metal filling layer;
step 6: preparing Cr and Au connected to each first piezoresistor on the second insulating layer by photoetching and magnetron sputtering as lead layers;
step 7: preparing silicon nitride as a third insulating layer on the outer surface of each lead layer through photoetching and plasma enhanced chemical vapor deposition;
step 8: selecting a BF33 glass sheet as a second substrate, and forming a groove in the center of the upper surface of the second substrate through photoetching and reactive ion etching;
step 9: tightly attaching the second substrate and the inverted first substrate in an anode bonding mode to form a cavity;
step 10: thinning the inverted first substrate by a chemical mechanical polishing process until the metal in the metal filling layer is exposed;
step 11: preparing four second piezoresistors on the upper surface of the inverted first substrate through boron ion implantation;
step 12: preparing silicon dioxide on the upper surface of the inverted first substrate by plasma enhanced chemical vapor deposition to serve as a fourth insulating layer;
step 13: and forming a contact hole on the fourth insulating layer by photoetching, and preparing Cr and Au on the fourth insulating layer by magnetron sputtering to serve as electrode layers, thereby completing the preparation of the device.
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
1. compared with the traditional MEMS piezoresistive pressure sensor, the MEMS piezoresistive pressure sensor with the double-bridge structure has the advantages that four piezoresistors are respectively distributed on the upper surface and the lower surface of the sensitive film to form two Wheatstone bridges, the sensitivity of the sensor is effectively improved on the premise that the thickness of the sensitive film of the sensor is not reduced and the area of the sensitive film of the sensor is not increased, the reliability of the sensor is improved, the integration level of the sensor is improved, and the area and the cost of the sensor are reduced.
2. According to the MEMS piezoresistive pressure sensor with the double-bridge structure, the electrode of the first piezoresistor positioned below the sensitive film is led out by the metal filling layer, so that interconnection wiring is facilitated, electric connection between piezoresistors is simplified, and the precision of the sensor is further ensured not to be affected by the concise wiring.
3. The sensor is prepared by adopting the MEMS technology and has the advantages of small size, high precision, good consistency, easiness in batch manufacturing and low cost.
Drawings
FIG. 1 is a schematic top view of a piezoresistor arrangement of a dual bridge structure MEMS piezoresistive pressure sensor of the present invention;
FIG. 2 is a schematic diagram of a Wheatstone bridge connection of piezoresistors of a dual bridge structure MEMS piezoresistive pressure sensor of the present invention;
FIG. 3 is a cross-sectional view of the MEMS piezoresistive pressure sensor in a double bridge structure according to the present invention, taken along the A-A' direction in FIG. 1;
FIG. 4 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the manufacturing step 1;
FIG. 5 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor in accordance with the present invention, obtained in the step 2;
FIG. 6 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the manufacturing step 3;
FIG. 7 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the process of manufacturing step 4;
FIG. 8 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the process 5;
FIG. 9 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the manufacturing step 6;
FIG. 10 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the process 7;
FIG. 11 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the process 8;
FIG. 12 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the process 9;
FIG. 13 is a cross-sectional view of a dual bridge structure MEMS piezoresistive pressure sensor according to the present invention, obtained in a fabrication step 10;
FIG. 14 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor of the present invention obtained in the process 11;
FIG. 15 is a cross-sectional view of the dual bridge structure MEMS piezoresistive pressure sensor according to the present invention, obtained in the process 12.
Detailed Description
The invention is further explained below with reference to the drawings.
As shown in fig. 1 and 3, the MEMS piezoresistive pressure sensor with a double-bridge structure comprises a first substrate 1, a second substrate 8 is arranged below the first substrate 1, a cavity 9 is arranged in the center of the upper surface of the second substrate 8, and a sensitive film 13 is formed on a part of the first substrate 1 opposite to the upper part of the cavity 9. Four first piezoresistors 4 are arranged on the lower surface of the first substrate 1, R1', R2', R3 'and R4', the four first piezoresistors 4 are opposite to the center positions of the four edges of the cavity 9, and the arrangement directions of the four first piezoresistors 4 are consistent. Four second piezoresistors 10, namely R1, R2, R3 and R4, are arranged on the upper surface of the first substrate 1, the four second piezoresistors 10 are respectively opposite to the four first piezoresistors 4 on the lower surface along the thickness direction of the sensitive film 10, and the arrangement direction of the four second piezoresistors 10 is respectively orthogonal to the first piezoresistors 4. The upper surface of the first substrate 1 is provided with an electrode layer 12, two ends of the four second piezoresistors 11 are respectively and electrically connected with the corresponding electrode layers 12, two ends of the four first piezoresistors 4 are respectively and electrically connected with the corresponding electrode layers 12 through metal leads, and the metal leads are provided with insulating layers. Four first piezoresistors 4 located on the lower surface of the first substrate 1 form a first wheatstone bridge, and four second piezoresistors 10 located on the upper surface of the first substrate 1 form a second wheatstone bridge, as shown in fig. 2.
Specifically, the material of the first substrate 1 is monocrystalline silicon, and the thickness is 10-50 μm. The material of the second substrate 8 is monocrystalline silicon or glass, preferably a sheet of BF33 type glass, with a thickness of 200-1000 μm. The cavity 9 in the center of the upper surface of the second substrate 8 is set to a depth of 1-50 μm. Four first piezoresistors 4 are arranged on the lower surface of the first substrate 1 and are opposite to the edge center of the cavity 9, and the purpose of this is to arrange the piezoresistors at the position where the stress of the sensitive film 13 is maximum, so that the sensitivity of the pressure sensor is improved as much as possible.
The metal leads are formed by connecting a lead layer 6 under the first substrate 1 and a metal filling layer 5 vertically penetrating through the first substrate 1. The eight metal filling layers 5 are symmetrically arranged on two sides of the edge of the sensitive film 13 relative to the four first piezoresistors 4 respectively, in order to facilitate electroplating of a filling hole structure, the material is preferably Cu, the thickness is the same as that of the first substrate 1, and the width is set to be 2-10 μm by combining the capability of the current deep groove etching and hole filling process.
The periphery of the metal filling layer 5 is wrapped with a first insulating layer 2, a second insulating layer 3 is arranged between the lead layer 6 and the first substrate 1, a third insulating layer 7 is arranged on the lower surface of the lead layer 6, and the materials of the first insulating layer 2, the second insulating layer 3 and the third insulating layer 7 are silicon dioxide or silicon nitride, and the thickness is 50-200nm. The first insulating layer 2 and the second insulating layer 3 function to achieve electrical isolation between the lead layer 6 and the metal filling layer 5 and the first substrate 1. The third insulating layer 7 serves to electrically isolate the lead layer 6 from the second substrate 8.
The upper surface of the first substrate 1 is further covered with a fourth insulating layer 11. The fourth insulating layer 11 is used for realizing electrical isolation between the electrode layer 12 and the first substrate 1, and is also used as a passivation layer of the second piezoresistor 10 for protecting the second piezoresistor 10 and improving the stability of the sensor. The thickness and material of the second insulating layer 3 between the lead layer 6 and the first substrate 1 are the same as those of the fourth insulating layer 11 on the upper surface of the first substrate 1, so that the effect of stress compensation can be achieved to improve the mechanical strength and reliability of the sensor.
The material of the lead layer 6 is preferably one of Al, ti, au, cu, pt and has a thickness of 100-500nm. The lead layer 6 and the metal filling layer 5 are electrically interconnected, and the function is to lead out the electrode of the first piezoresistor 4. The electrode layer 12 is arranged above the metal filling layer 5 and the second varistor 10, and is made of metal, preferably one of Al, ti, au, cu, pt, and has a thickness of 100-500nm. The electrode layer 12 serves to realize electrode extraction of the metal filling layer 5 and the second varistor 10.
The working principle of the high-sensitivity MEMS piezoresistive pressure sensor is as follows:
the sensitive film 13 deforms under the action of external pressure, the deformation of the sensitive film 13 causes the piezoresistors on the upper surface and the lower surface of the sensitive film to generate strain, the resistance values of the piezoresistors correspondingly change based on the piezoresistive effect, the stress directions of the upper surface and the lower surface of the sensitive film 13 are opposite, the piezoresistors corresponding to the upper surface and the lower surface of the sensitive film are mutually distributed to 90 degrees, the piezoresistance coefficient signs corresponding to the piezoresistors playing a leading role are opposite, the negative effect is achieved, the positive effect is achieved, the size and the direction of the resistance value change of the piezoresistors at the corresponding positions of the upper surface and the lower surface of the sensitive film 13 are the same, the upper surface and the lower surface respectively form two identical Wheatstone bridges, and double electrical output can be obtained compared with the single Wheatstone bridge formed by single piezoresistors, so that the sensitivity of the sensor is effectively improved on the premise that the film structure is not changed and other performances of the sensor are not reduced.
The preparation method of the MEMS piezoresistive pressure sensor with the double-bridge structure comprises the following steps:
step 1: as the first substrate 1, a 300 μm thick N-type (100) silicon wafer was selected as shown in fig. 4.
Step 2: eight blind holes 5 μm wide and 40 μm deep were formed in the first substrate 1 by photolithography and DRIE (Deep Reactive Ion Etching ), as shown in fig. 5.
Step 3: a layer of silicon dioxide with a thickness of 200nm was prepared as the first insulating layer 2 on the inner surface of the blind via hole by thermal oxidation, and a layer of silicon dioxide with a thickness of 200nm was prepared as the second insulating layer 3 on the upper surface of the first substrate 1, as shown in fig. 6.
Step 4: the varistor regions and the anodic bonding regions are etched on the second insulating layer 3 by photolithography and RIE (Reactive Ion Etching ), and the preparation of the four first piezoresistors 4 is completed in the varistor regions by boron ion implantation, as shown in fig. 7.
Step 5: and preparing 20nm Ti and 100nm Cu serving as a barrier layer and a seed layer respectively on the first insulating layer 2 in each blind hole through magnetron sputtering, filling the blind holes with electroplated Cu to form a metal filling layer 5, and removing redundant Cu through a CMP (Chemical Mechanical Polishing ) process to improve the flatness of the upper surface of the first substrate 1, as shown in fig. 8.
Step 6: 20nm Cr and 180nm Au connected to each of the first piezoresistors 4 were prepared as lead layers 6 on the second insulating layer 3 by photolithography and magnetron sputtering, as shown in FIG. 9.
Step 7: silicon nitride having a thickness of 200nm was prepared as the third insulating layer 7 on the outer surface of each lead layer 6 by photolithography and PECVD (Plasma Enhanced Chemical Vapor Deposition, plasma-enhanced chemical vapor deposition), as shown in fig. 10.
Step 8: a BF33 type glass sheet having a thickness of 500 μm was selected as the second substrate 8, and a recess having a depth of 50 μm was formed in the center of the upper surface of the second substrate 8 by photolithography and RIE, as shown in FIG. 11.
Step 9: the second substrate 8 is closely attached to the inverted first substrate 1 by means of anodic bonding to form a cavity 9, as shown in fig. 12.
Step 10: the inverted first substrate 1 is thinned to 40 μm by a CMP process, exposing the metal in the metal filling layer 5, as shown in fig. 13.
Step 11: four second piezoresistors 10 are prepared on the upper surface of the inverted first substrate 1 by boron ion implantation, as shown in fig. 14.
Step 12: silicon dioxide is prepared as the fourth insulating layer 11 on the upper surface of the inverted first substrate 1 by PECVD, as shown in fig. 15.
Step 13: the device was completed by forming a contact hole on the fourth insulating layer 11 by photolithography, and preparing Cr of 20nm and Cr of 180nm as the electrode layer 12 on the fourth insulating layer 11 by magnetron sputtering, as shown in fig. 3.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (2)
1. The preparation method of the double-bridge structure MEMS piezoresistive pressure sensor is characterized in that the double-bridge structure MEMS piezoresistive pressure sensor comprises a first substrate (1), a second substrate (8) is arranged below the first substrate (1), a cavity (9) is arranged in the center of the upper surface of the second substrate (8), and a sensitive film (13) is formed on the part, opposite to the upper part of the cavity (9), of the first substrate (1); four first piezoresistors (4) are arranged on the lower surface of the first substrate (1), the four first piezoresistors (4) are respectively opposite to the center positions of the four edges of the cavity (9), and the arrangement directions of the four first piezoresistors (4) are consistent; four second piezoresistors (10) are arranged on the upper surface of the first substrate (1), the four second piezoresistors (10) are respectively opposite to the four first piezoresistors (4) on the lower surface along the thickness direction of the sensitive film (10), and the arrangement directions of the four second piezoresistors (10) are respectively orthogonal to the first piezoresistors (4); the upper surface of the first substrate (1) is provided with an electrode layer (12), two ends of the four second piezoresistors (11) are respectively and electrically connected with the corresponding electrode layers (12), two ends of the four first piezoresistors (4) are respectively and electrically connected with the corresponding electrode layers (12) through metal leads, and the metal leads are provided with insulating layers; four first piezoresistors (4) positioned on the lower surface of the first substrate (1) form a first Wheatstone bridge, and four second piezoresistors (10) positioned on the upper surface of the first substrate (1) form a second Wheatstone bridge;
the method comprises the following steps:
step 1: an N-type (100) silicon wafer is selected as a first substrate (1);
step 2: forming eight blind holes in the first substrate (1) by lithography and deep reactive ion etching;
step 3: preparing a layer of silicon dioxide serving as a first insulating layer (2) on the inner surface of the blind hole through thermal oxidation, and preparing a layer of silicon dioxide serving as a second insulating layer (3) on the upper surface of the first substrate (1);
step 4: etching a piezoresistor area and an anode bonding area on the second insulating layer (3) through photoetching and reactive ion etching, and completing the preparation of four first piezoresistors (4) in the piezoresistor area through boron ion implantation;
step 5: ti and Cu are prepared on the first insulating layer (2) in each blind hole by magnetron sputtering to serve as a barrier layer and a seed layer respectively, and the blind holes are filled with Cu by electroplating to form a metal filling layer (5);
step 6: preparing Cr and Au connected to each first piezoresistor (4) on the second insulating layer (3) by photoetching and magnetron sputtering as lead layers (6);
step 7: preparing silicon nitride as a third insulating layer (7) on the outer surface of each lead layer (6) by photolithography and plasma-enhanced chemical vapor deposition;
step 8: selecting a BF33 glass sheet as a second substrate (8), and forming a groove in the center of the upper surface of the second substrate (8) through photoetching and reactive ion etching;
step 9: the second substrate (8) is tightly attached to the inverted first substrate (1) in an anode bonding mode to form a cavity (9);
step 10: thinning the inverted first substrate (1) by a chemical mechanical polishing process to expose the metal in the metal filling layer (5);
step 11: preparing four second piezoresistors (10) on the upper surface of the inverted first substrate (1) through boron ion implantation;
step 12: preparing silicon dioxide on the upper surface of the inverted first substrate (1) by plasma enhanced chemical vapor deposition as a fourth insulating layer (11);
step 13: and forming a contact hole on the fourth insulating layer (11) by photoetching, and preparing Cr and Au on the fourth insulating layer (11) as electrode layers (12) by magnetron sputtering to complete the preparation of the device.
2. The method for manufacturing a double bridge structure MEMS piezoresistive pressure sensor according to claim 1, characterized in that the thickness and material of the insulating layer (3) between the lead layer (6) and the first substrate (1) are the same as the insulating layer (11) on the upper surface of the first substrate (1).
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|---|---|---|---|---|
| CN104764547A (en) * | 2015-03-24 | 2015-07-08 | 西安交通大学 | Relief-type island film stress concentration structure micro-pressure sensor chip and preparing method |
| CN105181217A (en) * | 2015-05-05 | 2015-12-23 | 苏州曼普拉斯传感科技有限公司 | MEMS pressure sensor and preparation method thereof |
| CN113639902A (en) * | 2020-04-27 | 2021-11-12 | 中国科学院微电子研究所 | Pressure sensor and manufacturing method thereof |
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| CN104764547A (en) * | 2015-03-24 | 2015-07-08 | 西安交通大学 | Relief-type island film stress concentration structure micro-pressure sensor chip and preparing method |
| CN105181217A (en) * | 2015-05-05 | 2015-12-23 | 苏州曼普拉斯传感科技有限公司 | MEMS pressure sensor and preparation method thereof |
| CN113639902A (en) * | 2020-04-27 | 2021-11-12 | 中国科学院微电子研究所 | Pressure sensor and manufacturing method thereof |
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| Design and Characterization of Temperature-Robust Piezoresistive Micro-Pressure Sensor with Double-Wheatstone-Bridge Structure;Hsun-Heng Tsai等;《DTIP 2009》;全文 * |
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