CN116448290B - High-frequency dynamic MEMS piezoresistive pressure sensor and preparation method thereof - Google Patents
High-frequency dynamic MEMS piezoresistive pressure sensor and preparation method thereof Download PDFInfo
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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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
- B81B3/0018—Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
- B81B3/0021—Transducers for transforming electrical into mechanical energy or vice versa
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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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
- B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
- B81B2201/0264—Pressure sensors
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention relates to the technical field of pressure sensors, and particularly discloses a high-frequency dynamic MEMS piezoresistive pressure sensor and a preparation method thereof, wherein the high-frequency dynamic MEMS piezoresistive pressure sensor comprises a substrate, a first substrate and a pressure sensitive film, the pressure sensitive film is arranged on the first substrate, and the first substrate is arranged on the substrate; the pressure sensitive film comprises a piezoresistor, an ohmic contact area, a first passivation layer, a second passivation layer, a pressure sensitive electrode layer, a third passivation layer, a first driving electrode layer, a first dielectric layer, a second driving electrode layer, a fourth passivation layer, a fifth passivation layer, a first stress electrode layer and a second dielectric layer. The high-frequency dynamic MEMS piezoresistive pressure sensor provided by the invention can effectively improve the high-frequency dynamic characteristic of the MEMS piezoresistive pressure sensor, reduce or even eliminate the impact of the external environment on the sensor, reduce the zero offset and temperature drift of the pressure sensor, and improve the precision of the pressure sensor.
Description
Technical Field
The invention relates to the technical field of pressure sensors, in particular to a high-frequency dynamic MEMS piezoresistive pressure sensor and a preparation method thereof.
Background
The pressure is one of important physical parameters which need to be concerned by the modern measurement and control technology, and with the development of the modern measurement and control technology, the dynamic measurement requirement for the high-frequency environment is improved, and the requirement of the high-frequency dynamic pressure measurement is difficult to be met by the traditional pressure sensor. In the face of more specific situations, such as aerospace, medical electronics, weapon control, artificial intelligence, etc., in a fast, high frequency environment, very fast changing transient pressure signals are required to be tested.
MEMS (Micro-Electro-Mechanical System ) piezoresistive pressure sensors utilize the piezoresistive effect of semiconductor materials, and convert mechanical signals into electrical signals by interconnecting the semiconductor materials to form a Wheatstone bridge, thereby realizing pressure measurement. Compared with other traditional pressure sensors, the MEMS piezoresistive pressure sensor has better high-frequency dynamic characteristics, but with the high-speed of a post-processing circuit, the dynamic measurement capability of the MEMS piezoresistive pressure sensor is gradually a short plate in a system, so that the increasing commercial requirements are not met, and the problem of long setup time and recovery time still exists, so that the high-frequency dynamic characteristics need to be taken into consideration in design.
In addition, different fields of use have a corresponding influence on the measurement accuracy of the pressure sensor. Such as temperature changes or shock exposure. Temperature changes in the environment can cause changes in stress due to thermal expansion. Significant temperature variations, measurement nonlinearities become extremely severe, limiting the measurement accuracy and range of use of the pressure sensor. The existing solutions generally compensate the results by adding a temperature sensing device and adopting an empirical formula, but correspondingly, the designs put some tests on the size of the sensor, meanwhile, the discrete measurement can only infer the influence of thermal stress through a temperature value, the nonlinearity of the functional relation of the discrete measurement can be changed along with the change of external pressure, and when the thermal stress and the external pressure coexist, certain errors exist in measurement, so that certain influence is generated on the measurement precision of the sensor.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a high-frequency dynamic MEMS piezoresistive pressure sensor and a preparation method thereof, which can effectively improve the high-frequency dynamic characteristic of the MEMS piezoresistive pressure sensor, reduce or even eliminate the impact of the external environment on the sensor, reduce zero offset and temperature drift of the pressure sensor and improve the accuracy of the pressure sensor.
As one aspect of the present invention, there is provided a high frequency dynamic MEMS piezoresistive pressure sensor, comprising a base, a first substrate and a pressure sensitive membrane, the pressure sensitive membrane being disposed on the first substrate, the first substrate being disposed on the base;
wherein the pressure sensitive film comprises a piezoresistor, an ohmic contact area, a first passivation layer, a second passivation layer, a pressure sensitive electrode layer, a third passivation layer, a first driving electrode layer, a first dielectric layer, a second driving electrode layer, a fourth passivation layer, a fifth passivation layer, a first stress electrode layer and a second dielectric layer, four piezoresistors and eight ohmic contact areas are arranged on a first substrate, the eight ohmic contact areas are respectively positioned at two ends of the short sides of the four piezoresistors, the first passivation layer is formed on the upper surfaces of the first substrate and the piezoresistors, the second passivation layer is formed on the upper surface of the first passivation layer, holes are formed on the positions, corresponding to the ohmic contact areas, of the first passivation layer and the second passivation layer so as to expose the ohmic contact areas, forming a pressure-sensitive electrode layer on the upper surfaces of the ohmic contact area and the second passivation layer through photoetching and magnetron sputtering of a layer of copper so as to connect four piezoresistors into a Wheatstone bridge, forming a third passivation layer on the upper surfaces of the second passivation layer and the pressure-sensitive electrode layer, forming a first driving electrode layer on the upper surfaces of the third passivation layer and the first driving electrode layer, forming a first dielectric layer on the upper surfaces of the third passivation layer and the first driving electrode layer, forming a second driving electrode layer on the upper surfaces of the first dielectric layer, forming a fourth passivation layer on the upper surfaces of the first dielectric layer and the second driving electrode layer, sequentially forming a first groove and a second groove on the back surface of the first substrate, and sequentially forming a fifth passivation layer, a first strain electrode layer and a second dielectric layer on the lower surfaces of the first groove;
the substrate comprises a second substrate, a sixth passivation layer, a second strain electrode layer and a third dielectric layer, wherein the sixth passivation layer is formed on the upper surface of the central part of the second substrate, the second strain electrode layer is formed on the upper surface of the sixth passivation layer, the third dielectric layer is formed on the upper surfaces of the sixth passivation layer and the second strain electrode layer, the first substrate and the second substrate are connected through anodic bonding, and the central part of the second substrate, the sixth passivation layer, the second strain electrode layer and the third dielectric layer are all located in the second groove.
Further, the material of the first substrate is monocrystalline silicon, and the thickness of the first substrate is 50-300 mu m; the piezoresistor is made of silicon with shallow doping B; the eight ohmic contact areas are made of silicon heavily doped with B; the material of the first passivation layer is silicon dioxide, and the thickness of the first passivation layer is 100nm-1 mu m; the second passivation layer is made of silicon nitride, and the thickness of the second passivation layer is 100nm-1um; the pressure-sensitive electrode layer is made of copper, and the thickness of the pressure-sensitive electrode layer is 100nm-300nm; the third passivation layer is made of silicon dioxide, and the thickness of the third passivation layer is 1-5um; the first driving electrode layer is made of metal and has a thickness of 50nm-200nm; the material of the first dielectric layer is a material with high dielectric constant, and the thickness is 50-150nm; the second driving electrode layer is made of metal and has a thickness of 50nm-200nm; the fourth passivation layer is made of silicon dioxide, and the thickness of the fourth passivation layer is 1-5um; the fifth passivation layer is made of silicon dioxide, and the thickness of the fifth passivation layer is 1-6um; the first strain electrode layer is made of metal and has a thickness of 50-200nm; the second dielectric layer is made of a material with a high dielectric constant and has a thickness of 50-200nm.
Further, the first driving electrode layer, the first dielectric layer and the second driving electrode layer constitute a driving capacitor for providing an electrostatic force.
Further, the depth of the first groove is 45-270 um, and the depth of the second groove is 43-258 um.
Further, the second substrate is made of glass, and the thickness of the second substrate is 50-300 mu m; the sixth passivation layer is made of silicon nitride, and the thickness of the sixth passivation layer is 1um-6um; the second strain electrode layer is made of metal and has a thickness of 50-200nm; the material of the third dielectric layer is a material with high dielectric constant, and the thickness is 50-200nm.
Further, the second strained electrode layer comprises a plurality of metal blocks that are not connected to each other to determine the strain of the different regions.
Further, the first strain electrode layer, the second dielectric layer, the third dielectric layer and the second strain electrode layer form a strain detection capacitor, wherein the position of the second strain electrode layer is unchanged, and the first strain electrode layer changes position due to pressure, so that a capacitance value is changed, and strain measurement is realized.
As another aspect of the present invention, there is provided a method of manufacturing a high frequency dynamic MEMS piezoresistive pressure sensor, wherein the method of manufacturing a high frequency dynamic MEMS piezoresistive pressure sensor includes:
providing a first substrate and a base;
preparing a pressure sensitive film on the first substrate;
the upper surface of the base and the lower surface of the first substrate are bonded by anodic bonding.
Further, the method further comprises the following steps:
further comprises:
step a: selecting an N-type <100> silicon chip with the thickness of 300mm as a first substrate, and forming a piezoresistor with shallow doping B on the first substrate through photoetching and ion implantation;
step b: forming ohmic contact regions of heavy doping B on the two sides of the piezoresistor on the first substrate through photoetching and ion implantation;
step c: growing 100nm silicon oxide and 100nm silicon nitride on the upper surface of the first substrate by Low Pressure Chemical Vapor Deposition (LPCVD) to serve as a first passivation layer and a second passivation layer respectively;
step d: etching the first passivation layer and the second passivation layer by photoetching and Reactive Ion Etching (RIE) to expose the ohmic contact region, and forming a pressure-sensitive electrode layer on the upper surfaces of the ohmic contact region and the second passivation layer by photoetching and magnetron sputtering of copper with the thickness of 100-300 nm so as to connect the four piezoresistors into a Wheatstone bridge;
step e: growing a layer of silicon oxide with the thickness of 2um on the upper surfaces of the second passivation layer and the pressure sensitive electrode layer by photoetching and Low Pressure Chemical Vapor Deposition (LPCVD) to serve as a third passivation layer;
step f: sputtering a layer of copper with the thickness of 100nm on the upper surface of the third passivation layer by photoetching and magnetron sputtering to serve as a first driving electrode layer;
step g: growing a hafnium-zirconium composite oxide layer with the thickness of 50-150nm on the upper surfaces of the third passivation layer and the first driving electrode layer by atomic layer deposition ALD to serve as a first dielectric layer;
step h: sputtering a layer of copper with the thickness of 100nm on the upper surface of the first dielectric layer by photoetching and magnetron sputtering to serve as a second driving electrode layer;
step i: growing a layer of silicon oxide with the thickness of 2um on the upper surfaces of the first dielectric layer and the second driving electrode layer by Low Pressure Chemical Vapor Deposition (LPCVD) method to be used as a fourth passivation layer;
step j: etching ICP (inductively coupled plasma) through photoetching and inductively coupled plasma, and etching a first groove with the depth of 270um on the back surface of the first substrate;
step k: growing a layer of silicon oxide with the thickness of 1um on the lower surface of the first groove by photoetching and low-pressure chemical vapor deposition (LPCVD) to be used as a fifth passivation layer;
step l: sputtering a layer of copper with the thickness of 100nm on the lower surface of the fifth passivation layer through photoetching and magnetron sputtering to serve as a first variable electrode layer;
step m: growing a hafnium-zirconium composite oxide layer with the thickness of 50nm on the lower surface of the first strain electrode layer by photoetching and atomic layer deposition ALD to serve as a second dielectric layer;
step n: etching ICP (inductively coupled plasma) through photoetching and inductively coupled plasma, and etching a second groove with the depth of 258um on the back surface of the first substrate, wherein the cross section area of the second groove is larger than that of the first groove;
step o: a glass sheet with the thickness of 300um is taken, and is subjected to photoetching and inductively coupled plasma etching ICP to obtain a stepped structure as a second substrate, wherein the size of the middle part of the second substrate is smaller than that of the first groove, and the height of the middle part of the second substrate is 258um higher than that of the edge part of the second substrate;
step p: growing a layer of silicon nitride with the thickness of 1um on the upper surface of the thicker part in the middle of the second substrate by photoetching and low-pressure chemical vapor deposition (LPCVD) as a sixth passivation layer;
step q: sputtering a layer of copper with the thickness of 100nm on the upper surface of the sixth passivation layer by photoetching and magnetron sputtering to form a second strain electrode layer;
step r: growing a hafnium-zirconium composite oxide layer with the thickness of 50nm-100nm on the upper surfaces of the sixth passivation layer and the second strain electrode layer by photoetching and atomic layer deposition ALD to serve as a third dielectric layer;
step s: and bonding the first substrate and the second substrate through anodic bonding to finish the preparation of the high-frequency dynamic MEMS piezoresistive pressure sensor.
The invention has the following beneficial effects:
1. the invention provides electrostatic force for the pressure sensitive film by using the driving electrode, and can apply auxiliary force in corresponding direction and magnitude when deformation is generated, recovered and oscillated, thereby shortening the movement time of the pressure sensitive film and further improving the high-frequency dynamic characteristic of the pressure sensor;
2. the invention constructs a measuring-controlling feedback system through the driving electrode and the strain detecting electrode, and can realize the detection and control of the movement and deformation of the sensitive film, thereby reducing the unexpected deformation of the film, such as the bias caused by zero bias, temperature drift or impact acceleration, and improving the bias performance of the device;
3. according to the invention, the additional stress and strain conditions brought by temperature can be obtained in time through the measurement feedback system and are compensated, on one hand, compared with the traditional pressure-sensitive device, the temperature sensor is added, the size of the device is reduced, on the other hand, the temperature sensor can only measure and correct in later data, and the invention can realize control through electrostatic force;
4. the deformation condition of the pressure sensitive film can be timely known and fed back through the measurement feedback system, so that the device is prevented from being damaged by overlarge input, and the overload resistance of the device is improved;
5. according to the invention, by supplementing one strain detection electrode, the resistance change of the piezoresistor due to geometry can be obtained through the film strain data, so that the accuracy of the pressure sensor is improved;
6. 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
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain, without limitation, the invention.
FIG. 1 is a top view of a piezoresistive pressure sensor of a high frequency dynamic MEMS piezoresistive pressure sensor according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a Wheatstone bridge connection of piezoresistors of a high frequency dynamic MEMS piezoresistive pressure sensor in accordance with an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a high frequency dynamic MEMS piezoresistive pressure sensor according to an embodiment of the present invention, taken along the AA' line of FIG. 1.
Fig. 4 is a schematic structural diagram corresponding to the preparation step a in the embodiment of the present invention.
Fig. 5 is a schematic structural diagram corresponding to the preparation step b in the embodiment of the present invention.
Fig. 6 is a schematic structural diagram corresponding to the preparation step c in the embodiment of the present invention.
Fig. 7 is a schematic structural diagram corresponding to the preparation step d in the embodiment of the present invention.
Fig. 8 is a schematic structural diagram corresponding to the preparation step e in the embodiment of the present invention.
Fig. 9 is a schematic structural diagram corresponding to the preparation step f in the embodiment of the present invention.
Fig. 10 is a schematic structural diagram corresponding to the preparation step g in the embodiment of the present invention.
Fig. 11 is a schematic structural diagram corresponding to the preparation step h in the embodiment of the present invention.
Fig. 12 is a schematic structural diagram corresponding to the preparation step i in the embodiment of the present invention.
Fig. 13 is a schematic structural diagram corresponding to the preparation step j in the embodiment of the present invention.
Fig. 14 is a schematic structural diagram corresponding to the preparation step k in the embodiment of the present invention.
Fig. 15 is a schematic structural diagram corresponding to the preparation step i in the embodiment of the present invention.
Fig. 16 is a schematic structural diagram corresponding to the preparation step m in the embodiment of the present invention.
Fig. 17 is a schematic structural diagram corresponding to the preparation step n in the embodiment of the present invention.
Fig. 18 is a schematic structural diagram corresponding to the preparation step o in the embodiment of the present invention.
Fig. 19 is a schematic structural diagram corresponding to the preparation step p in the embodiment of the present invention.
Fig. 20 is a schematic structural diagram corresponding to the preparation step q in the embodiment of the present invention.
Fig. 21 is a schematic structural diagram corresponding to the preparation step r in the embodiment of the present invention.
Fig. 22 is a schematic structural diagram corresponding to the preparation step s in the embodiment of the present invention.
In the drawings, the list of components represented by the various numbers is as follows: 1-a first substrate; 2-piezoresistors; a 3-ohmic contact region; 4-a first passivation layer; 5-a second passivation layer; 6-a pressure sensitive electrode layer; 7-a third passivation layer; 8-a first drive electrode layer; 9-a first dielectric layer; 10-a second drive electrode layer; 11-a fourth passivation layer; 12-a first groove; 13-a fifth passivation layer; 14-a first strain electrode layer; 15-a second dielectric layer; 16-a second groove; 17-a second substrate; 18-a sixth passivation layer; 19-a second strained electrode layer; 20-a third dielectric layer.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate in order to describe the embodiments of the invention herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In the embodiment of the invention, as shown in fig. 1-3, a high-frequency dynamic MEMS piezoresistive pressure sensor is provided, wherein the high-frequency dynamic MEMS piezoresistive pressure sensor comprises a base, a first substrate 1 and a pressure sensitive film, the pressure sensitive film is arranged on the first substrate 1, and the first substrate 1 is arranged on the base;
wherein the pressure sensitive film comprises a piezoresistor 2, an ohmic contact area 3, a first passivation layer 4, a second passivation layer 5, a pressure sensitive electrode layer 6, a third passivation layer 7, a first driving electrode layer 8, a first dielectric layer 9, a second driving electrode layer 10, a fourth passivation layer 11, a fifth passivation layer 13, a first stress electrode layer 14 and a second dielectric layer 15, four piezoresistors 2 and eight ohmic contact areas 3 are arranged on a first substrate 1, the eight ohmic contact areas 3 are respectively positioned at two ends of the short sides of the four piezoresistors 2, the first passivation layer 4 is formed on the upper surfaces of the first substrate 1 and the piezoresistors 2, the second passivation layer 5 is formed on the upper surface of the first passivation layer 4, holes are formed on the positions, corresponding to the ohmic contact areas 3, of the first passivation layer 4 and the second passivation layer 5 so as to expose the ohmic contact areas 3, forming the pressure-sensitive electrode layer 6 on the upper surfaces of the ohmic contact region 3 and the second passivation layer 5 by photoetching and magnetron sputtering a layer of copper so as to connect the four piezoresistors 2 into a Wheatstone bridge, forming the third passivation layer 7 on the upper surfaces of the second passivation layer 5 and the pressure-sensitive electrode layer 6, forming the first driving electrode layer 8 on the upper surface of the third passivation layer 7, forming the first dielectric layer 9 on the upper surfaces of the third passivation layer 7 and the first driving electrode layer 8, forming the second driving electrode layer 10 on the upper surface of the first dielectric layer 9, forming the fourth passivation layer 11 on the upper surfaces of the first dielectric layer 9 and the second driving electrode layer 10, sequentially forming a first groove 12 and a second groove 16 on the back surface of the first substrate 1, the fifth passivation layer 13, the first strained electrode layer 14, and the second dielectric layer 15 are sequentially formed on the lower surface of the first recess 12.
Preferably, the base includes a second substrate 17, a sixth passivation layer 18, a second strained electrode layer 19 and a third dielectric layer 20, the sixth passivation layer 18 is formed on the upper surface of the central portion of the second substrate 17, the second strained electrode layer 19 is formed on the upper surface of the sixth passivation layer 18, the third dielectric layer 20 is formed on the upper surfaces of the sixth passivation layer 18 and the second strained electrode layer 19, the first substrate 1 and the second substrate 17 are connected by anodic bonding, and the central portion of the second substrate 17, the sixth passivation layer 18, the second strained electrode layer 19 and the third dielectric layer 20 are all located in the second groove 16.
Preferably, the material of the first substrate 1 is monocrystalline silicon, and the thickness is 50-300 μm; the plane position of the piezoresistor 2 is positioned at the edge of the first groove 12, the material is silicon with shallow doping B, B refers to boron, and the aim is to realize higher sensitivity; the eight ohmic contact areas 3 are made of heavily doped B silicon, so as to lead out electrodes of the piezoresistor 2; the material of the first passivation layer 4 is silicon dioxide, and the thickness is 100nm-1 mu m; the second passivation layer 5 is made of silicon nitride, and the thickness is 100nm-1um; the pressure-sensitive electrode layer 6 is made of copper and has a thickness of 100nm-300nm, so as to form a Wheatstone bridge connection of the piezoresistor.
Preferably, the material of the third passivation layer 7 is silicon dioxide, and the thickness is 1-5um; the material of the first driving electrode layer 8 is metal, preferably at least one of Cu, ti, ni, cr, au, W, etc., and the thickness is 50nm-200nm.
Preferably, the material of the first dielectric layer 9 is a material with a high dielectric constant, such as hafnium zirconium composite oxide, hafnium aluminum composite oxide, composite PVDF (nano fiber or nano sheet doped with barium titanate or titanium dioxide), etc., or a multi-layer composite structure composed of such materials, because it has a higher dielectric constant and better mechanical properties, and the total thickness is 50-150nm.
Preferably, the material of the second driving electrode layer 10 is metal, preferably at least one of Cu, ti, ni, cr, au, W, etc., and the thickness is 50nm-200nm.
Preferably, the material of the fourth passivation layer 11 is silicon dioxide, and the thickness is 1-5um, so as to be used as a protection layer; the fifth passivation layer 13 is made of silicon dioxide and has a thickness of 1-6um, so as to form electrical isolation and passivation protection and avoid substrate leakage current; the material of the first strain electrode layer 14 is metal, preferably metal with a high melting point, such as Cu, W, cr, ti, and the thickness is 50-200nm.
Preferably, the material of the second dielectric layer 15 is a material with a high dielectric constant, such as hafnium zirconium composite oxide, hafnium aluminum composite oxide, composite PVDF (barium titanate or titanium dioxide doped nanofiber or nanosheet), etc., or a multilayer composite structure thereof, because of its higher dielectric constant and better mechanical properties, and the total thickness is 50-200nm.
In particular, the purpose of the third passivation layer 7 is to form an electrical isolation between the pressure sensitive electrode layer 6 and the first drive electrode layer 8.
Preferably, the first drive electrode layer 8, the first dielectric layer 9 and the second drive electrode layer 10 constitute a drive capacitance for providing an electrostatic force. By controlling the frequency and the phase of the applied voltage, the movement condition of the film can be influenced and controlled, so that the set-up time and the recovery time of the pressure sensor are reduced, and the dynamic measurement capability of the pressure sensor is improved.
In particular, the thickness of the first dielectric layer 9 is much smaller than the thickness of the third passivation layer 7 in order to ignore as much as possible the electrostatic forces between the pressure sensitive electrode layer 6 and the first driving electrode layer 8.
In particular, the first dielectric layer 9 is intended to form an electrical isolation between the first drive electrode layer 8, the second drive electrode layer 10 and to act as a dielectric for the drive capacitance.
Preferably, the depth of the first groove 12 is 45um to 270um, and the depth of the second groove 16 is 43um to 258um.
Preferably, the material of the second substrate 17 is glass, and the thickness is 50-300 μm; the sixth passivation layer 18 is made of silicon nitride and has a thickness of 1um-6um, and is used as a protection layer; the material of the second strain electrode layer 19 is metal, preferably metal with high melting point, such as Cu, W, cr, ti, and the thickness is 50-200nm; the material of the third dielectric layer 20 is a material having a high dielectric constant, such as hafnium zirconium composite oxide, hafnium aluminum composite oxide, composite PVDF (barium titanate or titanium dioxide doped nanofiber or nanosheet), etc., or a multilayer composite structure thereof, because it has a higher dielectric constant and better mechanical properties, and the total thickness is 50-200nm.
Preferably, the second strain electrode layer 19 includes a plurality of metal blocks that are not connected to each other to measure strain in different regions, thereby achieving higher measurement accuracy.
Further, the first strained electrode layer 14, the second dielectric layer 15, the third dielectric layer 20 and the second strained electrode layer 19 constitute a strain detecting capacitor. According to the theoretical formula of capacitance, the capacitance value and the distance between the first strained electrode layer 14 and the second strained electrode layer 19 satisfy a certain mathematical relationship (the capacitance value is proportional to the reciprocal of the electrode spacing). The position of the second strained electrode layer 19 is unchanged, the first strained electrode layer 14 is forced to be pressed down by pressure, the distance between the first strained electrode layer 14 and the second strained electrode layer 19 is reduced, so that the capacitance value of the strain detection capacitor is changed, the voltage change can be obtained by a related C-V (capacitance-to-voltage) conversion circuit, and the strain measurement can be realized by mathematical model analysis.
Further, the purpose of the second dielectric layer 15, the third dielectric layer 20 is to act as a protective layer for the first strained electrode layer 14, the second strained electrode layer 19, and as a dielectric for the strain sensing capacitor.
The working principle of the high-frequency dynamic MEMS piezoresistive pressure sensor in the embodiment of the invention is as follows:
the pressure sensitive film deforms under the action of external pressure, the resistance value of the piezoresistor 2 positioned on the pressure sensitive film correspondingly changes based on the piezoresistive effect, and the change of the resistance value of the piezoresistor 2 is converted into voltage output through the Wheatstone bridge, so that the conversion from a pressure signal to an electrical signal is realized.
For the invention, the first driving electrode layer 8 and the second driving electrode layer 10 are added to supply electrostatic force, when the pressure sensitive film is deformed, the acting force in the same direction as the external pressure is applied by the electrostatic force, so that the acceleration of the movement of the pressure sensitive film is increased and the pressure sensitive film reaches the balance position more quickly; when the external pressure is removed and the pressure sensitive film needs to be recovered, the direction of the driving voltage is changed, so that the recoverable acceleration is increased, and the reduction of the establishment time and the recovery time is realized. On the other hand, according to the principle of mechanical vibration, when the pressure sensitive membrane moves to the equilibrium position, it will make a continuously decreasing oscillation in the equilibrium position due to its still velocity, which also affects the accuracy of the sensor and the repeatability of the test to a certain extent, while the method of controlling the electrostatic force by means of the electrode can well attenuate this effect.
Further, a strain sensing capacitor is added to the back cavity of the pressure sensor in combination with and by utilizing the principle of the strain type pressure sensor. Its action mainly has two points. First, the strain of the first strain electrode layer 14 is brought about by the strain of the pressure sensitive thin film, thereby changing the capacitance value of the strain-sensing capacitor. The displacement data of the sensitive film can be obtained through the value, and then a feedback circuit can be formed by the processing circuit and the driving electrode, so that more accurate control and measurement are realized. In addition, the feedback circuit for displacement detection-control can reduce a plurality of unexpected membrane deformation conditions, such as membrane deformation caused by zero drift, temperature drift, external impact and the like, and further improves the overload resistance and zero bias performance of the device. Secondly, the resistance change of the piezoresistor 2 caused by deformation can be obtained through calculation by designing a strain detection electrode corresponding to the position of the piezoresistor 2 and a corresponding algorithm, so that the measurement precision is further improved.
The embodiment of the invention also provides a preparation method of the high-frequency dynamic MEMS piezoresistive pressure sensor, which comprises the following steps:
providing a first substrate 1 and a base;
preparing a pressure sensitive film on the first substrate 1;
the upper surface of the base and the lower surface of the first substrate 1 are bonded by anodic bonding.
In order to further explain the implementation of the high-frequency dynamic MEMS piezoresistive pressure sensor according to the present invention, fig. 4 to 22 are schematic diagrams illustrating the process of forming the high-frequency dynamic MEMS piezoresistive pressure sensor according to the embodiment of the present invention, and as shown in fig. 4 to 22, the preparation method of the high-frequency dynamic MEMS piezoresistive pressure sensor specifically includes:
step a: as shown in fig. 4, an N-type <100> silicon wafer with the thickness of 300mm is selected as a first substrate 1, and a piezoresistor 2 with shallow doping B is formed on the first substrate 1 through photoetching and ion implantation;
step b: as shown in fig. 5, heavily B-doped ohmic contact regions 3 are formed on the first substrate 1 on both sides of the varistor 2 by photolithography and ion implantation;
step c: as shown in fig. 6, 100nm of silicon oxide and 100nm of silicon nitride are grown on the upper surface of the first substrate 1 as the first passivation layer 4 and the second passivation layer 5, respectively, by LPCVD (Low Pressure Chemical Vapor Deposition low pressure chemical vapor deposition);
step d: as shown in fig. 7, the first passivation layer 4 and the second passivation layer 5 are etched by photolithography and RIE (Reactive Ion Etching reactive ion etching) to expose the ohmic contact region 3, and a layer of copper having a thickness of 100nm to 300nm is sputtered by photolithography and magnetron to form a pressure sensitive electrode layer 6 on the upper surfaces of the ohmic contact region 3 and the second passivation layer 5 to connect the four piezoresistors 2 into a wheatstone bridge;
step e: as shown in fig. 8, a layer of silicon oxide having a thickness of 2um is grown on the upper surfaces of the second passivation layer 5 and the pressure sensitive electrode layer 6 by photolithography and Low Pressure Chemical Vapor Deposition (LPCVD) to serve as a third passivation layer 7;
step f: as shown in fig. 9, a layer of copper with a thickness of 100nm is sputtered on the upper surface of the third passivation layer 7 as the first driving electrode layer 8 by photolithography and magnetron sputtering;
step g: as shown in fig. 10, a layer of hafnium-zirconium composite oxide (Hf-Zr-O) having a thickness of 50-150nm is grown on the upper surfaces of the third passivation layer 7 and the first driving electrode layer 8 by ALD (Atomic Layer Deposition ) as the first dielectric layer 9;
step h: as shown in fig. 11, copper with a thickness of 100nm is sputtered on the upper surface of the first dielectric layer 9 by photolithography and magnetron sputtering as the second driving electrode layer 10;
step i: as shown in fig. 12, a layer of silicon oxide having a thickness of 2um is grown on the upper surfaces of the first dielectric layer 9 and the second driving electrode layer 10 by low pressure chemical vapor deposition LPCVD as a fourth passivation layer 11;
step j: as shown in fig. 13, a first groove 12 having a depth of 270um is etched in the back surface of the first substrate 1 by photolithography and ICP (Inductively Couple Plasma, inductively coupled plasma etching);
step k: as shown in fig. 14, a layer of silicon oxide having a thickness of 1um is grown on the lower surface of the first recess 12 as a fifth passivation layer 13 by photolithography and Low Pressure Chemical Vapor Deposition (LPCVD);
step l: as shown in fig. 15, a layer of copper having a thickness of 100nm is sputtered on the lower surface of the fifth passivation layer 13 as the first strained electrode layer 14 by photolithography and magnetron sputtering;
step m: as shown in fig. 16, a layer of hafnium zirconium composite oxide having a thickness of 50nm is grown on the lower surface of the first strained electrode layer 14 as the second dielectric layer 15 by photolithography and atomic layer deposition ALD;
step n: as shown in fig. 17, a second groove 16 with a depth of 258um is etched on the back surface of the first substrate 1 by photoetching and inductively coupled plasma etching ICP, and the cross-sectional area of the second groove 16 is larger than that of the first groove 12;
step o: as shown in fig. 18, another glass sheet with a thickness of 300um is taken, and ICP is etched by photolithography and inductively coupled plasma to obtain a stepped structure as a second substrate 17, wherein the size of the middle portion of the second substrate 17 is slightly smaller than the size of the first recess 12, and the height of the middle portion of the second substrate 17 is 258um higher than the height of the edge portion;
step p: as shown in fig. 19, a layer of silicon nitride having a thickness of 1um is grown as a sixth passivation layer 18 on the upper surface of the second substrate 17 at a thicker portion in the middle by photolithography and Low Pressure Chemical Vapor Deposition (LPCVD);
step q: as shown in fig. 20, copper with a thickness of 100nm is sputtered on the upper surface of the sixth passivation layer 18 as a second strained electrode layer 19 by photolithography and magnetron sputtering;
step r: as shown in fig. 21, a layer of hafnium-zirconium composite oxide having a thickness of 50nm to 100nm is grown on the upper surfaces of the sixth passivation layer 18 and the second strained electrode layer 19 by photolithography and atomic layer deposition ALD as the third dielectric layer 20;
step s: as shown in fig. 22, the fabrication of the high frequency dynamic MEMS piezoresistive pressure sensor is completed by bonding the first substrate 1 and the second substrate 17 by anodic bonding.
It is to be understood that the above embodiments are merely illustrative of the application of the principles of the present invention, but not in limitation thereof. Various modifications and improvements may be made by those skilled in the art without departing from the spirit and substance of the invention, and are also considered to be within the scope of the invention.
Claims (8)
1. The high-frequency dynamic MEMS piezoresistive pressure sensor is characterized by comprising a base, a first substrate (1) and a pressure sensitive film, wherein the pressure sensitive film is arranged on the first substrate (1), and the first substrate (1) is arranged on the base;
wherein the pressure sensitive film comprises a piezoresistor (2), an ohmic contact area (3), a first passivation layer (4), a second passivation layer (5), a pressure sensitive electrode layer (6), a third passivation layer (7), a first driving electrode layer (8), a first dielectric layer (9), a second driving electrode layer (10), a fourth passivation layer (11), a fifth passivation layer (13), a first stress electrode layer (14) and a second dielectric layer (15), four piezoresistors (2) and eight ohmic contact areas (3) are arranged on a first substrate (1), the eight ohmic contact areas (3) are respectively positioned at two short sides of the four piezoresistors (2), the upper surfaces of the first substrate (1) and the piezoresistors (2) are provided with the first passivation layer (4), the upper surface of the first passivation layer (4) is provided with the second passivation layer (5), the positions corresponding to the ohmic contact areas (3) on the first passivation layer (4) and the second passivation layer (5) are provided with holes for exposing the ohmic contact areas (3) to form a magnetic bridge (6) through the contact areas, the upper surfaces of the second passivation layer (5) and the pressure-sensitive electrode layer (6) are provided with the third passivation layer (7), the upper surface of the third passivation layer (7) is provided with the first driving electrode layer (8), the upper surfaces of the third passivation layer (7) and the first driving electrode layer (8) are provided with the first dielectric layer (9), the upper surface of the first dielectric layer (9) is provided with the second driving electrode layer (10), the upper surfaces of the first dielectric layer (9) and the second driving electrode layer (10) are provided with the fourth passivation layer (11), the back surface of the first substrate (1) is provided with a first groove (12) and a second groove (16) in sequence, and the lower surface of the first groove (12) is provided with the fifth passivation layer (13), the first strained electrode layer (14) and the second dielectric layer (15) in sequence;
the substrate comprises a second substrate (17), a sixth passivation layer (18), a second strain electrode layer (19) and a third dielectric layer (20), wherein the sixth passivation layer (18) is formed on the upper surface of the central part of the second substrate (17), the second strain electrode layer (19) is formed on the upper surface of the sixth passivation layer (18), the third dielectric layer (20) is formed on the upper surfaces of the sixth passivation layer (18) and the second strain electrode layer (19), the first substrate (1) and the second substrate (17) are connected through anodic bonding, and the central part of the second substrate (17), the sixth passivation layer (18), the second strain electrode layer (19) and the third dielectric layer (20) are all located in the second groove (16).
2. The high frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that the material of said first substrate (1) is monocrystalline silicon, with a thickness of 50-300 μm; the piezoresistor (2) is made of silicon with shallow doping B; the material of the eight ohmic contact areas (3) is silicon heavily doped with B; the material of the first passivation layer (4) is silicon dioxide, and the thickness is 100nm-1 mu m; the second passivation layer (5) is made of silicon nitride, and the thickness of the second passivation layer is 100nm-1um; the pressure-sensitive electrode layer (6) is made of copper, and the thickness is 100nm-300nm; the material of the third passivation layer (7) is silicon dioxide, and the thickness is 1-5um; the first driving electrode layer (8) is made of metal and has a thickness of 50-200nm; the material of the first dielectric layer (9) is a material with high dielectric constant, and the thickness is 50-150nm; the second driving electrode layer (10) is made of metal and has a thickness of 50-200nm; the fourth passivation layer (11) is made of silicon dioxide, and the thickness is 1-5um; the fifth passivation layer (13) is made of silicon dioxide, and the thickness is 1-6um; the first strain electrode layer (14) is made of metal and has a thickness of 50-200nm; the second dielectric layer (15) is made of a material with a high dielectric constant and has a thickness of 50-200nm.
3. The high frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that said first driving electrode layer (8), first dielectric layer (9) and second driving electrode layer (10) constitute a driving capacitance for providing electrostatic forces.
4. The high frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, wherein the depth of said first recess (12) is 45um-270um and the depth of said second recess (16) is 43um-258um.
5. The high frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that the material of said second substrate (17) is glass, with a thickness of 50-300 μm; the sixth passivation layer (18) is made of silicon nitride and has a thickness of 1um-6um; the second strain electrode layer (19) is made of metal and has a thickness of 50-200nm; the material of the third dielectric layer (20) is a material with high dielectric constant and the thickness is 50-200nm.
6. The high frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, wherein said second strained electrode layer (19) comprises a plurality of metal blocks not connected to each other to determine the strain of different areas.
7. The high frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, wherein said first strain electrode layer (14), second dielectric layer (15), third dielectric layer (20) and second strain electrode layer (19) constitute a strain detection capacitance, wherein the position of said second strain electrode layer (19) is unchanged, said first strain electrode layer (14) changes position due to pressure, thereby causing a capacitance value change, enabling a measurement of strain.
8. A method of manufacturing a high frequency dynamic MEMS piezoresistive pressure sensor according to any of claims 1-7, wherein the method of manufacturing a high frequency dynamic MEMS piezoresistive pressure sensor comprises:
step a: selecting an N-type <100> silicon chip with the thickness of 300mm as a first substrate (1), and forming a piezoresistor (2) with shallow doping B on the first substrate (1) through photoetching and ion implantation;
step b: forming heavily-doped B ohmic contact regions (3) on the first substrate (1) at two sides of the piezoresistor (2) through photoetching and ion implantation;
step c: growing 100nm silicon oxide and 100nm silicon nitride on the upper surface of the first substrate (1) by Low Pressure Chemical Vapor Deposition (LPCVD) to serve as a first passivation layer (4) and a second passivation layer (5) respectively;
step d: etching the first passivation layer (4) and the second passivation layer (5) through photoetching and Reactive Ion Etching (RIE) to expose the ohmic contact region (3), and forming a pressure-sensitive electrode layer (6) on the upper surfaces of the ohmic contact region (3) and the second passivation layer (5) through photoetching and magnetron sputtering to form copper with the thickness of 100nm-300nm so as to connect the four piezoresistors (2) into a Wheatstone bridge;
step e: growing a silicon oxide layer with the thickness of 2um on the upper surfaces of the second passivation layer (5) and the pressure sensitive electrode layer (6) by photoetching and Low Pressure Chemical Vapor Deposition (LPCVD) to serve as a third passivation layer (7);
step f: sputtering a layer of copper with the thickness of 100nm on the upper surface of the third passivation layer (7) by photoetching and magnetron sputtering to serve as a first driving electrode layer (8);
step g: growing a hafnium-zirconium composite oxide layer with the thickness of 50-150nm on the upper surfaces of the third passivation layer (7) and the first driving electrode layer (8) by atomic layer deposition ALD to serve as a first dielectric layer (9);
step h: sputtering a layer of copper with the thickness of 100nm on the upper surface of the first dielectric layer (9) by photoetching and magnetron sputtering to serve as a second driving electrode layer (10);
step i: growing a silicon oxide layer with the thickness of 2um on the upper surfaces of the first dielectric layer (9) and the second driving electrode layer (10) by Low Pressure Chemical Vapor Deposition (LPCVD) to be used as a fourth passivation layer (11);
step j: etching a first groove (12) with the depth of 270um on the back surface of the first substrate (1) by photoetching and inductively coupled plasma etching ICP;
step k: growing a layer of silicon oxide with the thickness of 1um on the lower surface of the first groove (12) by photoetching and low-pressure chemical vapor deposition (LPCVD) to serve as a fifth passivation layer (13);
step l: sputtering a layer of copper with the thickness of 100nm on the lower surface of the fifth passivation layer (13) by photoetching and magnetron sputtering to serve as a first variable electrode layer (14);
step m: growing a hafnium-zirconium composite oxide layer with the thickness of 50nm on the lower surface of the first strain electrode layer (14) by photoetching and atomic layer deposition ALD to serve as a second dielectric layer (15);
step n: etching a second groove (16) with a depth of 258um on the back surface of the first substrate (1) by photoetching and Inductively Coupled Plasma (ICP), wherein the cross section area of the second groove (16) is larger than that of the first groove (12);
step o: a glass sheet with the thickness of 300um is taken, and is subjected to photoetching and inductively coupled plasma etching ICP to obtain a stepped structure, wherein the size of the middle part of the second substrate (17) is smaller than that of the first groove (12), and the height of the middle part of the second substrate (17) is 258um higher than that of the edge part;
step p: growing a layer of silicon nitride with a thickness of 1um on the upper surface of the thicker part in the middle of the second substrate (17) by photoetching and low-pressure chemical vapor deposition (LPCVD) as a sixth passivation layer (18);
step q: sputtering a layer of copper with the thickness of 100nm on the upper surface of the sixth passivation layer (18) by photoetching and magnetron sputtering to form a second strain electrode layer (19);
step r: growing a hafnium-zirconium composite oxide layer with the thickness of 50nm-100nm on the upper surfaces of the sixth passivation layer (18) and the second strain electrode layer (19) by photoetching and atomic layer deposition ALD to serve as a third dielectric layer (20);
step s: and bonding the first substrate (1) and the second substrate (17) through anodic bonding, so as to complete the preparation of the high-frequency dynamic MEMS piezoresistive pressure sensor.
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| CN1511252A (en) * | 2001-05-25 | 2004-07-07 | ÷ | High sensitivity pressure sensor with long term stability |
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