CN115207207B - Method for manufacturing high-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure - Google Patents

Abstract

A method for manufacturing a pressure sensor with a nitride and magnetostrictive material composite structure belongs to the field of semiconductor sensors. The technical scheme is as follows: s1, preparing a substrate; s2, epitaxial growth; s3, isolating the table top; s4, etching the grid; s5, making ohmic contact of a source electrode and a drain electrode; s6, depositing a dielectric layer; s7, preparing a gate electrode; and S8, depositing a passivation layer and opening an electrode window. Has the beneficial effects that: the method for manufacturing the high-sensitivity pressure sensor based on the composite nitride and magnetostrictive material structure can manufacture the high-sensitivity pressure sensor with high pressure sensitivity, small volume, high integration level, large range and high response speed, can further manufacture a sensor array to realize two-dimensional or three-dimensional pressure sensing, and is expected to be applied to the fields of medical blood pressure, petrifaction, industrial electronic weighing, river water level monitoring and the like in the future.

Description

High-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure Production Method

technical field

The invention belongs to the field of semiconductor sensors, in particular to a method for manufacturing a high-sensitivity pressure sensor based on a compound nitride and magnetostrictive material structure.

Background technique

A pressure sensor is a device or device that senses a pressure signal and converts the input pressure signal into an output electrical signal according to the law. It is widely used in the fields of medical blood pressure, petrochemical, industrial electronic weighing, and river water level monitoring. Current pressure sensors mainly include piezoresistive pressure sensors, piezoelectric pressure sensors, and capacitive pressure sensors. The piezoresistive pressure sensor uses the piezoresistive effect of metal or semiconductor materials. After being pressed, the resistance of the chip changes, and the bridge loses balance. A constant current source is added to the bridge to output a corresponding electrical signal. The semiconductor processing technology of the sensor is complicated, and additional temperature compensation measures are required to suppress the zero drift, which cannot meet the needs of the petrochemical industry for small temperature drift. Piezoelectric pressure sensors measure the pressure value through the electrode difference generated at both ends of the piezoelectric material after the piezoelectric material is pressed. Since the charge in the piezoelectric effect cannot be saved, the static pressure cannot be measured, and the dynamic response capability is poor, which cannot meet the needs of the market. Electronically weigh static pressure on demand. After the capacitive pressure sensor is pressed, the capacitance difference between the film electrode and the fixed electrode is converted into a voltage signal. The parasitic capacitance has a great influence, and it is difficult to ensure the symmetry of the processing. Therefore, it is an urgent problem to form a pressure sensor that is small in size, easy to process, high in sensitivity, capable of measuring both static and dynamic pressure, and fast in response.

Compared with the traditional first- and second-generation Si and GaAs semiconductors, the third-generation GaN semiconductor material has the characteristics of a bandgap width of 3.45eV, a critical breakdown electric field greater than 3MV/cm, and an electron saturation migration velocity as high as 2×10 ⁷ cm/s. Due to spontaneous polarization and piezoelectric polarization, a high-density two-dimensional electron gas (2DEG) is generated at the AlGaN/GaN heterojunction interface under unintentional doping, and the electron mobility of the conductive channel reaches 2000cm ² /(V · S). The two-dimensional electron gas is sensitive to external gas, magnetic field, phonon, heat and other physical quantities, and the pressure source can also lead to changes in the concentration of the two-dimensional electron gas. Even a small pressure will cause a large concentration of the two-dimensional electron gas. The change.

The giant magnetostrictive material has high compressive strength and short response time; the electromechanical coupling coefficient is as high as 70%, which is much higher than 40% of the piezoelectric ceramic PZT in the electrostrictive material; the magnetostrictive coefficient is large (approximately Fe, Ni Dozens of times), the resulting strain is 15 to 30 times higher than the electrostrictive material piezoelectric ceramic PZT material; it has a △E effect (the strain changes the magnetic permeability and stress state of the magnetostrictive material, and the Young's modulus is very constant ), Young's modulus can be changed by external magnetic field, pressure, temperature and prestress, and is suitable for various extreme harsh environments; the Curie temperature is above 300 ° C, and it can still work stably at a high temperature of 200 ° C when it is made as a pressure sensor; there is no Performance degradation due to aging after prolonged use. Terfenol-D (TbDyFe) is a representative of rare earth giant magnetostrictive materials. Its strain value under the drive of low magnetic field is as high as 1500-2000ppm, which is 5-8 times that of the traditional magnetostrictive material piezoelectric ceramics. , 40 to 50 times that of nickel-based materials. The response speed of the magnetostriction coefficient with the change of the magnetic field is very fast, reaching 10 ^-6 s. At the same time, it has soft magnetic properties, that is, low remanence and coercive force.

The device formed by the nitride material has tensile stress inside due to the nature of the material itself. When combining the nitride and the magnetostrictive material, a magnetoelectric effect is generated, and the magnetostrictive layer is subjected to a magnetic field to generate a magnetostrictive strain (ie, a magnetostrictive coefficient). , resulting in further deformation of the barrier layer of the nitride heterojunction, which greatly increases the repetition rate of the ground state wave function of electrons and holes after being transmitted to the channel layer, increases the recombination probability of the two, and the overall polarization intensity will change, and finally As a result, the concentration of 2DEG changes greatly, and the performance of the pressure sensor device is improved. Therefore, 2DEG is more sensitive to the strain caused by pressure at this time, and the sensitivity is greatly increased. Therefore, the present invention proposes a high-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure and its manufacturing method.

Most of the piezoresistive pressure sensors, piezoelectric pressure sensors, and capacitive pressure sensors on the market require multiple power supplies, are bulky, difficult to process, slow in response, and poor in sensitivity. The traditional giant magnetostrictive material passive pressure sensor uses the Wheatstone bridge to convert the deformation change of the magnetostrictive rod after the pressure change into a voltage signal output to work. The upper and lower permanent magnets and the trapezoidal yoke Although the structure does not require an additional power supply, it has low sensitivity, large size, large footprint, greater influence by temperature, influence by parasitic capacitive effects, and poor repeatability.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a high-sensitivity pressure sensor with a composite material structure that is small in size, easy to process and integrate, high in sensitivity, large in range, and fast in response. After the magnetostrictive strain is transmitted to the channel layer, the piezoelectric polarization intensity at the heterojunction interface decreases, the 2DEG concentration changes, the channel carriers accumulate or deplete, and the external pressure makes the magnetostrictive film and the heterojunction The overall strain at the interface is greater, and the strain causes the resistance of the sensor strain gauge to change. The change in the resistance of the strain gauge makes the originally balanced Wheatstone bridge port have a voltage signal output, and the strain generated by the pressure is converted into a voltage signal for output.

The technical solution is as follows:

A method for manufacturing a high-sensitivity pressure sensor based on a composite nitride and magnetostrictive material structure, the steps are as follows:

S1. Substrate preparation: prepare the substrate, clean the substrate material, and remove pollutants on the substrate surface;

S2. Epitaxial growth: IBSD deposited by metal-organic compound chemical vapor deposition, molecular beam epitaxy, hydride vapor phase epitaxy, magnetron sputtering, pulsed laser deposition PLD, ion beam sputtering, any one of them Epitaxial growth of III-V nitride heterojunction structures, buffer layers and magnetostrictive layers;

S3. Mesa isolation: After photolithography, use plasma etching method or ion implantation method or chemical solution wet etching method to electrically isolate the device;

S4. Gate etching: after photolithography, the magnetostrictive layer in the gate region is etched by a plasma etching method;

S5. Fabrication of source and drain ohmic contacts: After photolithography, use electron beam evaporation method or thermal evaporation method or magnetron sputtering method to grow multi-layer metal stacks, and form ohmic contacts after high-temperature thermal annealing;

S6. Dielectric layer deposition: growing the dielectric layer by chemical vapor deposition, atomic layer deposition, magnetron sputtering, or thermal evaporation;

S7. Preparing the gate electrode: after photolithography, a metal thin layer is grown by electron beam evaporation method, thermal evaporation method or magnetron sputtering method to form a gate electrode;

S8. Deposition of passivation layer and opening of electrode window: use chemical vapor deposition method or atomic layer deposition method or magnetron sputtering method or thermal evaporation method to grow dielectric passivation layer, after photolithography, use dry method or wet method on each electrode area The passivation layer is removed by the method, the window is opened for wiring, the metal layer is grown by the electron beam evaporation method or the thermal evaporation method or the magnetron sputtering method, and the welding pad is made and the wiring is carried out.

Further, in step S2, the thickness of the generated magnetostrictive layer is 50-900 nm, the thickness of the channel layer is 0.1-5 μm, the thickness of the barrier layer is 2-100 nm; the thickness of the buffer layer is 10-300 nm.

Further, the buffer layer is any one of AlN, GaN, and superlattice structures.

Further, the channel layer and the barrier layer of the group III-V nitride heterojunction structure are formed, and the contact interface between the two is induced by polarized charges to generate a two-dimensional electron gas.

Further, the barrier layer is any one of AlN, AlGaN and AlGaAs.

Further, the magnetostrictive layer is any one of Fe, TbDyFe, FeGaB, SmPrFe, and ferrite.

Further, the magnetostrictive layer adopts the method of magnetron sputtering or ion beam sputtering to deposit IBSD to prepare a film with a thickness of 50-900nm, wherein the magnetron sputtering power is 50-300W, and the sputtering pressure is 1-1.5 Pa, after the thin film is prepared, thermal anneal in an O ₂ atmosphere at 400-475°C for 1-3 hours; the sputtering pressure of ion beam sputtering IBSD is 2.0×10 ^-2 ～3×10 ^-2 Pa, and the ion beam current is 19 ～21mA, thermal annealing in O ₂ atmosphere at 150～250℃ for 1～3h after the film preparation is completed.

Further, in step S4, the remaining thickness of the magnetostrictive layer in the gate region after etching is 5-20 nm.

The beneficial effects of the present invention are: the high-sensitivity pressure sensor produced by the high-sensitivity pressure sensor manufacturing method based on the composite nitride and magnetostrictive material structure described in the present invention is more efficient due to the transmission of the magnetoinduced strain to the heterojunction barrier layer If the piezoelectric polarization is changed to a large extent, the 2DEG concentration will change greatly. On this basis, the high concentration of 2DEG is more sensitive to the external pressure to be measured, thereby effectively improving the pressure sensitivity; at the same time, due to the direct combination of the magnetostrictive film and III- The group IV nitride heterojunction avoids the problem of large volume of magnetostrictive rod-shaped materials in traditional magnetostrictive pressure sensors. Therefore, this miniaturized pressure sensor is small in size and highly integrated. It can also be used to make sensor arrays to realize two-dimensional or three-dimensional pressure sensing. It is expected to be used in medical blood pressure, petrochemical, industrial electronic weighing, river water level monitoring and other fields in the future.

The characteristics of the high-sensitivity pressure sensor technical solution based on III-V nitride heterojunction combined with magnetostrictive materials proposed by the technology of the present invention are: 1) High integration: using nitride heterojunction semiconductor and magnetostrictive film compound As a sensitive material, the planar device produced is small in size and highly integrated, and array devices can be produced to realize two-dimensional or three-dimensional pressure detection; 2) Large measurement range: the detection types include compressive pressure and tensile pressure, and the detection pressure can be greater than ±100kPa; 3) High sensitivity: The magnetostrictive material produces a large strain under low magnetic field, and the magnetostrictive strain is transmitted to the heterojunction interface to a greater extent to change the band bending caused by the piezoelectric polarization of the channel layer , so the 2DEG is more sensitive to the magneto-induced strain induced by pressure and magnetic field.

The key of the invention lies in sensor innovation and preparation technology. In order to improve the pressure range and sensitivity of the measurement, the key of the present invention is to combine the magnetostrictive film and the III-IV nitride heterojunction together. On the basis of the magnetic strain, the external pressure is more sensitive to the change of the 2DEG concentration, thereby Effectively improve the sensitivity of the pressure sensor. The strain current change is converted into a voltage signal output by using Wheatstone bridge. This solution greatly reduces the size of the traditional magnetostrictive pressure sensor, significantly improves the sensitivity, and detects a wider range of pressure.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in conjunction with the accompanying drawings and detailed embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. Technical personnel can also obtain other drawings based on these drawings without paying creative labor. in:

Fig. 1 is the schematic cross-sectional view of the structure of the high-sensitivity pressure sensor proposed in the application of the present invention;

Fig. 2 is a schematic diagram of a process flow of a specific embodiment of the present invention;

Fig. 3 is the pressure and magnetostrictive coefficient, output voltage relation experimental result schematic diagram that the present invention proposes;

4 is a system block diagram of a circuit device according to an embodiment of the present invention;

5 is a schematic circuit diagram of a signal acquisition and signal amplification module in an embodiment of the present invention;

6 is a schematic diagram of a power module circuit according to an embodiment of the present invention;

FIG. 7 is a schematic circuit diagram of a data interface module according to an embodiment of the present invention;

Fig. 8 is the STM32 single-chip microcomputer main control module circuit schematic diagram in the embodiment of the present invention;

Fig. 9 is a test schematic diagram of Wheatstone 1/4 bridge and Wheatstone half bridge.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The fabrication method of the high-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure will be further described below in conjunction with accompanying drawings 1-9.

Example 1

The application of the present invention proposes a manufacturing method of a high-sensitivity pressure sensor with a composite nitride and magnetostrictive material structure. The invention utilizes that under the action of an external magnetic field, after the magnetoinduced strain is transmitted to the channel layer, the piezoelectric polarization intensity decreases at the heterojunction interface, the 2DEG concentration changes, the channel carriers accumulate or deplete, and the external pressure makes the magnetoinduced The overall strain at the interface between the stretch film and the heterojunction is greater, and the strain causes the resistance of the sensor strain gauge to change. The change in the resistance of the strain gauge makes the originally balanced Wheatstone 1/4 bridge port have a voltage signal output, and the strain caused by the pressure converted into a voltage signal for output.

The schematic diagram of the device structure of the technical solution of the present invention application is shown in Figure 1: the substrate is made of silicon, sapphire, silicon carbide, gallium nitride, gallium oxide, and diamond materials, on which an epitaxial growth buffer layer and a III-V heterojunction structure are formed. The magnetostrictive layer is prepared by magnetron sputtering, and the atomic layer deposition dielectric layer, in which the buffer layer can be AlN or GaN or AlGaN (thickness 10-300nm), the channel layer is GaN or GaAs (thickness 0.1-5μm), potential The barrier layer is AlN or AlGaN or AlGaAs (thickness 2-100nm), the material composition in the barrier layer is not limited, and the magnetostrictive layer is any one of Fe, TbDyFe, FeGaB, SmPrFe, ferrite. (thickness is 50-900nm), the source electrode and the drain electrode are composite metal structure ohmic contact, the gate electrode is Schottky contact or metal/dielectric/semiconductor (MIS) structure. The electrode shape is not particularly limited, and may be rectangular, circular, or the like. The source electrode and the drain electrode are arranged on both sides of the barrier layer, and they are respectively in contact with the magnetostrictive layer and the dielectric layer, and the gate is arranged on the dielectric layer.

The technical scheme of the present invention is as follows: the drains and sources of the pressure sensor devices R ₁ , R ₂ , R ₃ , and R ₄ are connected end to end to form a Wheatstone bridge circuit, wherein R ₂ , R ₃ , and R ₄ are covered with magnetic shielding. The two ends of the pressure sensor strain resistance lead are respectively connected to the two input lines of the Wheatstone bridge, and the potentiometer is adjusted to balance the bridge. The coil provides a bias magnetic field for the sensor, and the sensor is strained by the combined action of the magnetic field and the pressure. The external input power supply is 12V. After being pressed, a voltage signal is generated at the output of the bridge. The bridge converts the measured pressure signal into a corresponding voltage signal. After processing the electrical signal, the single-chip computer displays the pressure and the corresponding voltage value on the display screen middle.

The Wheatstone bridge is a balanced bridge composed of 4 pressure sensor resistors. When there is no external force, the 4 resistors are balanced. When the sensor is deformed due to external pressure, the resistance of _R1 changes, the bridge loses balance, and a voltage signal is output at the output terminal.

The circuit system includes a signal acquisition module, a signal amplification module, a power supply module, a data interface module, and a single-chip microcomputer main control module. The signal acquisition module and the signal amplification module amplify the voltage signal of the Wheatstone bridge; the power supply module supplies power for the data interface module and the main control module; the data interface module includes a USB interface and a USB-to-serial port; the single-chip main control module includes a main control chip , storage, button, reset, and display. After continuous detection, the pressure and corresponding voltage are displayed on the OLED display according to the calibration value of the pressure and the magnetostrictive coefficient.

The device preparation method steps of the application of the present invention are as follows:

1) Substrate preparation: prepare the substrate, clean the substrate material, and remove pollutants on the substrate surface.

2) Epitaxial growth: using metal organic compound chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), magnetron sputtering, pulsed laser deposition PLD, ion beam sputtering deposition IBSD , any of which epitaxially grows the III-V nitride heterojunction structure, buffer layer and magnetostrictive layer, the thickness of the generated magnetostrictive layer is 50-900nm, the thickness of the channel layer is 0.1-5μm, and the barrier The thickness of the layer is 2-100nm, the buffer layer can be AlN, GaN or super lattice structure, and the thickness is 10-300nm. The magnetostrictive film with a thickness of 50-900nm is sputtered by ion beam sputtering IBSD, in which the sputtering working pressure is 2×10 ^-2 Pa, the background pressure is 5×10 ^-5 Pa, the discharge voltage is 55V, and the discharge current 0.3mA, beam current voltage 1KV, ion beam current 20mA, filament current 5A, acceleration voltage 300V, acceleration current 0.5A. Vacuum annealing was performed at 200°C for 30 min after the film was prepared.

3) Mesa isolation: After photolithography, the device is electrically isolated by plasma etching or ion implantation or chemical solution wet etching.

4) Gate etching: after photolithography, the magnetostrictive layer in the gate area is etched by plasma etching technology, and the remaining thickness after etching is 5-20 nm.

5) Fabrication of source and drain ohmic contacts: After photolithography, use electron beam evaporation or thermal evaporation or magnetron sputtering to grow multi-layer metal stacks, and form ohmic contacts after high-temperature thermal annealing.

6) Dielectric layer deposition: the dielectric layer is grown by chemical vapor deposition, atomic layer deposition, magnetron sputtering or thermal evaporation.

7) Preparing the gate electrode: after photolithography, a thin metal layer is grown by electron beam evaporation or thermal evaporation or magnetron sputtering to form the gate electrode.

8) Deposition of passivation layer and opening of electrode window: use chemical vapor deposition or atomic layer deposition or magnetron sputtering or thermal evaporation to grow dielectric passivation layer, after photolithography, use dry method or wet method to remove in each electrode area Passivation layer, open window lead, use electron beam evaporation or thermal evaporation or magnetron sputtering method to grow metal layer, make pad and lead.

Example 2

A schematic diagram of the device structure of a high-sensitivity pressure sensor based on a composite nitride and magnetostrictive material structure is shown in Figure 1, including: substrate, buffer layer, channel layer, barrier layer, magnetostrictive layer, and dielectric layer , source, drain and gate, and grow a 2nm AlN buffer layer, a 4μm GaN channel layer and a 25nm Al _0.25 Ga _0.75 N barrier layer sequentially on the 6-inch Si substrate, and the channel layer and the barrier layer form a different The contact interface between the two is induced by polarized charges to generate a two-dimensional electron gas, and the 810nm thick Tb _0.3 Dy _0.7 Fe _1.9 magnetostrictive layer and 20nm Al ₂ O ₃ dielectric layer are sequentially arranged above the barrier layer; The source and the drain are arranged on both sides of the barrier layer, and they are respectively in contact with the dielectric layer and the magnetostrictive layer, and the gate is arranged on the dielectric layer. The distance between the drain electrode and the gate electrode was 4 μm, and the width was 500 μm.

The implementation process of the target device of this patent application is described as follows:

1) Substrate preparation: prepare a 6-inch Si substrate material, perform ultrasonic cleaning in acetone (MOS grade) for 2 minutes, cook in a positive glue stripping solution at 60°C for 10 minutes, and ultrasonicate the sample for 3 minutes in acetone and ethanol For cleaning, use a hydrofluoric acid solution of HF:H ₂ O=1:5 for 30 seconds, clean with deionized water and blow dry with pure N ₂ .

2) Epitaxial growth: AlGaN/GaN heterojunction structure, buffer layer AlN and magnetostrictive layer TbDyFe are epitaxially grown by metal organic compound chemical vapor deposition (MOCVD) and magnetron sputtering. The channel layer is unintentionally doped GaN with a thickness of 4 μm, the barrier layer Al _0.25 Ga _0.75 N with a thickness of 25 nm, and the buffer layer is AlN with a thickness of 2 nm. A Tb _0.3 Dy _0.7 Fe _1.9 film with a thickness of 810nm was prepared by radio frequency magnetron sputtering above the heterojunction, in which the terbium-dysprosium-iron alloy target was 99.9% (Tb:Dy:Fe=0.3:0.7:1.9)φ50.8 ×3mm, magnetron sputtering power 150W, sputtering Ar ₂ gas pressure 1Pa, target distance 60mm, background vacuum 1.5×10 ^-5 Pa, and thermal annealing in 475℃ O ₂ atmosphere for 3h after film preparation.

3) Mesa isolation: After the epitaxially grown sample is photolithographically etched by reactive ion etching (RIE), the Cl ₂ flow rate is controlled at 15 sccm, the cavity pressure is 10 mTorr, the etching power is 50 W, and the etching time is 2.5 min. The two-step method combining power etching and low power etching has an etching depth of 120nm to completely isolate the conductive channel.

4) Gate etching: After the photolithographic development of the sample, use inductively coupled plasma (ICP) to etch the gate area to a depth of 800nm with Cl-based gas, and optimize the parameters of the etching process to reduce etching damage.

5) Fabrication of source-drain ohmic contacts: After photolithography and development, electron beam evaporation is used to deposit Ti/Al/Ni/Au (22/140/55/45nm) four-layer alloy structure, and rapid thermal annealing (RTA) in nitrogen at 830°C 30s to form an ohmic contact.

6) Deposition of dielectric layer: Atomic layer deposition (ALD) is used to deposit Al 2 O 3 at 200° C. for 1 hour to generate 20 nm Al ₂ O ₃ .

7) Preparation of gate electrode: Ag (100 nm) is deposited by electron beam evaporation, the distance between the drain electrode and the gate electrode is 4 μm, and the width is 500 μm.

8) Deposition of passivation layer and opening of electrode window: Deposit 400nm SiO ₂ passivation layer by PECVD method, after photolithography, open holes and etch the gate dielectric layer to expose the electrode contact metal, after coating (using AZp4620 positive photoresist) , uniform glue (forward rotation 600rpm-3s, back rotation 1000rmp-20s, final photoresist thickness is 1μm), photolithography, development (80 seconds), use ICP etching to etch the window at the surface electrode, and then magnetic Controlled sputtering and deposition of 400nm Al on the lead pads.

Fig. 3 shows the relationship between the pressure of the sensor designed in the present invention, the magnetostriction coefficient and the output voltage. The pressure range that the device (2.5mm×2.5mm) can detect reaches -70kPa～70kPa (the negative sign is the tensile pressure). When there is only a 0.4T magnetic field, the sensor's magnetostriction coefficient is 15.98×10 ^-6 , and under the action of a 0.4T magnetic field and a tensile pressure of 70KPa, the sensor's stretching coefficient reaches a maximum of 312×10 ^-6 , and the magnetostriction coefficient It has increased by 18.5%, the output voltage has increased by 1.8mV, and the sensitivity has reached 2.13mV/N.

The key of the present invention is to combine the magnetostrictive film and the III-IV nitride heterojunction, and on the basis of the magneto-induced strain, the external pressure is more sensitive to the change of the 2DEG concentration, thereby effectively improving the sensitivity of the pressure sensor. This solution greatly reduces the size of the traditional magnetostrictive pressure sensor, significantly improves the sensitivity, and detects a wider range of pressure. The manufacturing process of the device not only reduces the degree of lattice matching, but also ensures that the electrodes have good ohmic contact, which greatly improves the performance of the device product. The application of the present invention mainly protects the proposed sensor structure design innovation and device process preparation technology.

Example 3

This embodiment provides the sensor device testing process as follows:

1) Process to manufacture pressure sensor devices with III-IV nitrides combined with magnetostrictive materials; 2) After passing current to the excitation coil, a bias magnetic field parallel to the surface of the sensor device is generated, and the wire is connected to the pressure source and the device. Under the action of pressure, the sensor device produces magneto-induced strain; 3) The USB interface is connected to the computer PC, and the PC will import the program including the set value of pressure, magnetic field strength, magnetostriction coefficient, voltage and duration, and the voltage and the set value of the duration can be a range value, the main control chip will calibrate and compensate the detected pressure and the detected value of the output voltage with the imported voltage and the set value of the voltage, and the pressure and the corresponding output The voltage value is displayed in the 0LED display.

In one example of the present invention, the circuit system includes a signal acquisition module, a signal amplification module, a power supply module, a data interface module, and an STM32 single-chip microcomputer main control module. The signal acquisition module uses the Wheatstone 1/4 bridge in Figure 6 to convert the pressure change into a voltage change; the signal amplification module uses the AD620 in Figure 6 to process the signal, including filtering and amplification, and the magnification is adjusted by adjusting the AD620 Set the external gain control resistor R _g , set R _g to 5KΩ to amplify the signal 10 times; the power supply module uses the USB5V power supply in Figure 7, and converts the 5V voltage to 3.3V voltage through the step-down chip TPS73633, which is the main control chip and serial port program The download circuit is powered; at the same time, the LM2663 negative voltage conversion chip is used to convert the 5V voltage to -5V voltage to provide negative voltage power supply for the signal amplification circuit; the data interface module adopts the one-key download circuit in Figure 8 and the USB to serial port unit CH340C; the STM32 single-chip microcomputer host The control module model adopts STM32F103RCT6 in Figure 9 as the main control chip, including crystal oscillator circuit, data storage FLASH and EEPROM, buttons BOOT and Key, reset circuit RESET, and OLED display pins. The main control module converts the amplified analog signal into The digital signal is displayed on OLED to complete the pressure detection.

The target device realization process of this patent application:

1) Epitaxial growth: AlGaN/GaN heterojunction structure and AlN buffer layer are epitaxially grown on a 6-inch silicon substrate by metal-organic compound chemical vapor deposition (MOCVD), and the epitaxial layer is 2nm in thickness from bottom to top. AlN buffer layer, 4μm GaN channel layer, 25nm thick Al _0.25 Ga _0.75 N barrier layer. The 810nm magnetostrictive film is prepared by radio frequency magnetron sputtering above the heterojunction, where the sputtering power is 50-300W, the sputtering _Ar2 pressure is 1-1.5Pa, and the film is prepared at 400-475°C Thermal annealing in O ₂ atmosphere for 1~3h.

2) Mesa isolation: After the epitaxially grown sample is etched by reactive ion etching (RIE), the flow rate of Cl ₂ is controlled at 20sccm, the chamber pressure is 10mTorr, the etching power is 50W, and the etching time is 2.5min. The two-step method combining power etching and low power etching has an etching depth of 120nm to completely isolate the conductive channel.

3) Gate etching: After the photolithographic development of the sample, use inductively coupled plasma (ICP) to etch the gate area to a depth of 800nm with Cl-based gas, and optimize the parameters of the etching process to reduce etching damage.

4) Fabrication of source-drain ohmic contact: After photolithography and development, electron beam evaporation is used to deposit Ti/Al/Ni/Au (22/140/55/45nm) four-layer alloy structure, and rapid thermal annealing (RTA) in nitrogen at 850°C 20s to form an ohmic contact.

5) Deposition of dielectric layer: Atomic layer deposition (ALD) is used to deposit Al 2 O 3 at 200° C. for 1 hour to generate 20 nm Al ₂ O ₃ .

6) Preparation of the gate electrode: after photolithography and development, the gate electrode Ag (100 nm) was deposited by electron beam evaporation, the distance between the drain electrode and the gate electrode was 4 μm, and the width was 900 μm.

7) Deposition of passivation layer and opening of electrode window: Deposit 300nm SiO ₂ passivation layer by PECVD method, after photolithography, use ICP etching technology to open holes to expose electrode contact metal, and then deposit 400nm Al on the electrode by magnetron sputtering The lead wires are used to make pads.

Example 4

In order to further improve the sensitivity of the sensor and the measurement voltage range, and increase the value of the output voltage, further, the Wheatstone 1/4 bridge is changed to a Wheatstone half bridge. Utilizing the principle of converting the strain generated by the pressure into the resistance change of the sensor device, R ₁ and R ₃ in the Wheatstone half-bridge are the resistance of the deformation sensor device that feels the pressure to be measured, and the four resistances are equal in balance and are R, R The resistance increments of ₁ and _R3 are both △R. Among them, formula 1 is the output voltage formula of Wheatstone 1/4 bridge, and formula 2 is the formula of output voltage of Wheatstone half bridge. It is easy to get the output voltage of Wheatstone half bridge is twice the output voltage of 1/4 bridge, and the sensitivity is corresponding is also increased by 2 times.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (7)

1. A method for making a high-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure, characterized in that the steps are as follows: S1. Substrate preparation: prepare the substrate, clean the substrate material, and remove pollutants on the substrate surface; S2. Epitaxial growth: IBSD deposited by metal-organic compound chemical vapor deposition, molecular beam epitaxy, hydride vapor phase epitaxy, magnetron sputtering, pulsed laser deposition PLD, ion beam sputtering, any one of them Epitaxial growth of III-V nitride heterojunction structure, buffer layer and magnetostrictive layer, the III-V nitride heterojunction structure is formed by channel layer and barrier layer, the contact interface between the two is formed by pole Electron charge induced two-dimensional electron gas; S3. Mesa isolation: After photolithography, use plasma etching method or ion implantation method or chemical solution wet etching method to electrically isolate the device; S4. Gate etching: after photolithography, the magnetostrictive layer in the gate region is etched by a plasma etching method; S5. Fabrication of source and drain ohmic contacts: After photolithography, use electron beam evaporation method or thermal evaporation method or magnetron sputtering method to grow multi-layer metal stacks, and form ohmic contacts after high-temperature thermal annealing; S6. Dielectric layer deposition: growing the dielectric layer by chemical vapor deposition, atomic layer deposition, magnetron sputtering, or thermal evaporation; S7. Preparing the gate electrode: after photolithography, a metal thin layer is grown by electron beam evaporation method, thermal evaporation method or magnetron sputtering method to form a gate electrode; S8. Deposition of passivation layer and opening of electrode window: use chemical vapor deposition method or atomic layer deposition method or magnetron sputtering method or thermal evaporation method to grow dielectric passivation layer, after photolithography, use dry method or wet method on each electrode area The passivation layer is removed by the method, the window is opened for wiring, the metal layer is grown by the electron beam evaporation method or the thermal evaporation method or the magnetron sputtering method, and the welding pad is made and the wiring is carried out. 2. The method for manufacturing a high-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure as claimed in claim 1, characterized in that, in step S2, the thickness of the generated magnetostrictive layer is 50-900nm, and the channel layer The thickness is 0.1-5 μm, the barrier layer has a thickness of 2-100 nm; the buffer layer has a thickness of 10-300 nm. 3. The method for manufacturing a high-sensitivity pressure sensor based on composite nitride and magnetostrictive material structure as claimed in claim 1, characterized in that, in step S4, the remaining thickness of the magnetostrictive layer in the grid area is 5-5% after being etched. 20nm. 4. the high-sensitivity pressure sensor manufacturing method based on composite nitride and magnetostrictive material structure as claimed in claim 1, is characterized in that, described buffer layer is any one in AlN, GaN or superlattice structure . 5. The method for manufacturing a high-sensitivity pressure sensor based on a compound nitride and magnetostrictive material structure according to claim 1, wherein the barrier layer is any one of AlN, AlGaN, and AlGaAs. 6. the high-sensitivity pressure sensor manufacturing method based on composite nitride and magnetostrictive material structure as claimed in claim 2, is characterized in that, described magnetostrictive layer is Fe, TbDyFe, FeGaB, SmPrFe, ferrite any of the 7. the high-sensitivity pressure sensor manufacturing method based on compound nitride and magnetostrictive material structure as claimed in claim 1, it is characterized in that, the specific steps of the growth method of magnetostrictive layer in step S2 are as follows: A magnetostrictive film with a thickness of 50-900nm is prepared by magnetron sputtering above the heterojunction, where the sputtering power is 50-300W and the sputtering pressure is 1-1.5Pa. Thermal annealing in O ₂ atmosphere at ℃ for 1~3h; A magnetostrictive film with a thickness of 50-900nm is prepared by ion beam sputtering deposition of IBSD above the heterojunction, where the sputtering pressure is 2.0×10 ^-2 to 3×10 ^-2 Pa, and the ion beam current is 19 to 21mA, thermal annealing in an O ₂ atmosphere at 150-250°C for 1-3 hours after the film is prepared.

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