Diamond piezoresistive effect pressure sensitive structure design method

Abstract

The invention discloses a diamond piezoresistive effect pressure sensitive structure design method, which comprises the following steps of: forming a buried oxide layer through ion implantation by taking a single crystal diamond as a substrate, and processing a three-dimensional gradient cantilever beam array and a hyperboloid diaphragm initial contour on the diamond substrate by utilizing an oxygen plasma anisotropic etching technology; and then, carrying out crystal orientation selective etching by adopting Ar / Cl2 mixed gas to form a V-shaped stress concentration groove. And finally, through an atomic layer deposition technology, an Al2O3 / TiN composite transition layer is deposited on the surface of the double-curved-surface diaphragm, and gradient distribution of carrier mobility is regulated and controlled, so that synergistic enhancement of a piezoresistive effect and structural mechanics is realized. The structure is high in sensitivity, high in stability, excellent in corrosion resistance and abrasion resistance, good in heat dissipation performance and suitable for high-precision pressure measurement scenes.

Description

Technical Field

[0001] This invention relates to a pressure-sensitive structure, and more particularly to a design method for a diamond piezoresistive pressure-sensitive structure. Background Technology

[0002] Diamond, as a superhard material, possesses extremely high Young's modulus and anisotropic piezoresistive properties, making it a potential candidate for pressure-sensitive structure design. However, traditional pressure-sensitive structures often suffer from insufficient sensitivity, poor stability under high pressure, susceptibility to corrosion and wear, and inadequate heat dissipation. Especially in harsh environments, the corrosion resistance and wear resistance of traditional materials may not meet the requirements for long-term stable operation. Furthermore, traditional pressure-sensitive structures also lack synergistic enhancement in terms of piezoresistive effect and structural mechanics, limiting further performance improvements. Summary of the Invention

[0003] This invention overcomes the shortcomings of the prior art and provides a design method for a pressure-sensitive structure based on the diamond piezoresistive effect.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a design method for a diamond piezoresistive pressure-sensitive structure, wherein the pressure-sensitive structure includes: a diamond substrate, a three-dimensional gradient cantilever beam array, and a hyperboloid diaphragm; the design steps include the following:

[0005] S1. A buried oxide layer with a thickness of 200~500nm is formed on the diamond substrate by ion implantation, defining the mechanical isolation region of the diamond substrate;

[0006] S2. The diamond substrate is anisotropically etched using oxygen plasma. By controlling the etching time difference, the three-dimensional gradient cantilever beam array is processed on the front side of the diamond substrate, while the initial contour of the hyperboloid film is formed on the back side of the diamond substrate.

[0007] S3. Use a mixture of Ar / Cl2 gas to selectively etch the initial contour of the hyperboloid film, and process periodic V-shaped stress concentration grooves on the surface of the hyperboloid film.

[0008] S4. Using atomic layer deposition technology, Al2O3 and TiN layers are sequentially deposited on the surface of the hyperboloid film to form an Al2O3 / TiN composite transition layer. By controlling the carrier mobility gradient distribution at the diamond / electrode contact interface, the synergistic enhancement of piezoresistive effect and structural mechanics is achieved.

[0009] In a preferred embodiment of the present invention, the three-dimensional gradient cantilever beam array is radially distributed along the

[110] crystal direction, wherein the beam cross-sectional width of each three-dimensional gradient cantilever beam decreases exponentially from the fixed end to the free end, and the width distribution satisfies the formula: In the formula, The width of the cantilever beam section; Let be the initial width of the fixed end of the cantilever beam; x is the coordinate along the length of the cantilever beam; and .

[0010] In a preferred embodiment of the present invention, the geometric parameters of the groove depth and groove spacing of the V-shaped stress concentration groove satisfy the following relationship: the groove depth is set to 0.35 to 0.45 times the thickness of the hyperboloid membrane at the location; the groove spacing between adjacent V-shaped stress concentration grooves is controlled to be between 0.2 and 0.35 times the effective radius of the hyperboloid membrane.

[0011] In a preferred embodiment of the present invention, the diamond substrate is made of single-crystal diamond material, and the surface of the single-crystal diamond material is subjected to hydrogen plasma termination treatment to form... / Hybrid bonding synthesis, with a thickness of 5-15 nm; the connection between the individual three-dimensional gradient cantilever beam and the hyperboloid film is provided with a rounded transition structure, with a radius of curvature of... It is used to eliminate stress singularities.

[0012] In a preferred embodiment of the present invention, the hyperboloid film adopts a variable thickness design, and the thickness distribution satisfies:

[0013] ;

[0014] In the formula, The thickness of a local area of ​​the hyperboloid film; The thickness at the center of the hyperbolic film is 2 to 5. ; R is the thickness gradient coefficient, with a value ranging from 0.1 to 0.3; R is the effective radius of the hyperboloid film, with a value ranging from 100 to 300. ; r is the radial coordinate of a local position of the hyperboloid membrane.

[0015] In a preferred embodiment of the present invention, the sidewall of the V-shaped stress concentration groove forms a

[100] crystal orientation exposed surface, which, together with the

[110] crystal orientation of the three-dimensional gradient cantilever beam array, constitutes a piezoresistive coefficient differential structure, such that the longitudinal piezoresistive coefficient and the transverse piezoresistive coefficient satisfy: ;in, This refers to the longitudinal piezoresistive coefficient; This is the lateral piezoresistive coefficient.

[0016] In a preferred embodiment of the present invention, in step S3, the crystal orientation selective etching employs a two-step process, including:

[0017] Step 1: Use SF6 plasma to etch the

[110] crystal plane, the etching rate is 2 to 3 times higher than that of the

[100] crystal plane;

[0018] Step 2: Use C4F8 passivation to protect the sidewalls of the

[100] crystal plane, and the perpendicularity of the groove sidewalls of the V-shaped stress concentration groove. .

[0019] In a preferred embodiment of the present invention, in step S4, the design parameters of the atomic layer deposition technology are: deposition temperature of 200~300℃; and deposition cycle number of 50~200 times.

[0020] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0021] (1) Single-crystal diamond is used as the substrate material. Its extremely high Young's modulus and anisotropic piezoresistive properties enable it to withstand extremely high pressure without plastic deformation, thus ensuring the stability of the pressure-sensitive structure under high pressure. By designing the crystal orientation, the piezoresistive effect is maximized, thereby improving the sensitivity. It is suitable for pressure measurement applications that require high precision and high reliability.

[0022] (2) Diamond hardly reacts with any chemical substances at room temperature, which enables the diamond pressure-sensitive structure to work stably for a long time in harsh environments, unaffected by corrosion and wear, thus extending its service life, reducing maintenance costs, lowering the replacement frequency, and improving overall reliability.

[0023] (3) Diamond has extremely high thermal conductivity, which is conducive to rapid heat dissipation during operation, avoids the impact of thermal stress on performance, maintains continuous performance stability, reduces performance degradation caused by overheating, and improves working ability in high-temperature environments.

[0024] (4) By designing a three-dimensional gradient cantilever beam array, hyperboloid diaphragm and V-shaped stress concentration groove structure, and combining atomic layer deposition technology to control the carrier mobility gradient distribution, the synergistic enhancement of piezoresistive effect and structural mechanics was achieved, the overall performance was improved, and a larger electrical signal change was generated when subjected to pressure, which improved the sensitivity of signal detection and provided a new solution for high-precision pressure measurement.

[0025] (5) The three-dimensional gradient cantilever beam array is radially distributed along the

[110] crystal direction. The cross-sectional width of each cantilever beam decreases exponentially from the fixed end to the free end. The hyperboloid diaphragm adopts a variable thickness design and is equipped with a periodic V-shaped stress concentration groove. This optimized structural design realizes the directional transmission of stress and signal amplification, further improving the sensitivity and meeting the requirements of high-precision pressure measurement. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the design method of a preferred embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0030] like Figure 1 As shown, the design method for a diamond piezoresistive pressure-sensitive structure includes the following steps:

[0031] S1. Material Selection and Pretreatment

[0032] The main reasons for using single-crystal diamond as the substrate in this embodiment are as follows:

[0033] Single-crystal diamond has an extremely high Young's modulus, enabling it to withstand extremely high pressure without undergoing plastic deformation, thus ensuring the stability of pressure-sensitive structures under high-pressure environments.

[0034] Diamond crystals exhibit anisotropic piezoresistive properties, with their piezoresistive coefficient varying significantly depending on the crystal orientation. By rationally designing the crystal orientation, the piezoresistive effect can be maximized, thereby improving sensitivity.

[0035] Diamonds hardly react with any chemicals at room temperature, have excellent corrosion resistance and wear resistance, and are suitable for various harsh environments.

[0036] Diamond has extremely high thermal conductivity, about 2000 W / m·K, which is beneficial for the sensor to dissipate heat quickly during operation and avoid the impact of thermal stress on the sensor performance.

[0037] Before performing micro / nano fabrication on diamond substrates, pretreatment is required to improve processing quality and efficiency. The pretreatment steps mainly include:

[0038] The diamond substrate is ultrasonically cleaned using organic solvents (such as acetone and ethanol) and deionized water to remove organic contaminants and particulate impurities from the surface.

[0039] The cleaned diamond substrate was placed in a hydrogen plasma reaction chamber for hydrogen plasma termination treatment. During the treatment, the hydrogen plasma reacted with the carbon atoms on the diamond surface to form a sp² / sp³ mixed bonding layer. This layer not only improves the hydrophilicity of the diamond surface, which is beneficial for subsequent photoresist coating, but also passivates the dangling bonds on the diamond surface to a certain extent, reducing the surface state density and improving the performance and stability of the device. The treatment parameters are as follows: hydrogen flow rate: 20~50 sccm; reaction chamber pressure: 10~30 mTorr; RF power: 100~300 W; treatment time: 5~15 minutes.

[0040] S2, Preparation of buried oxide layer

[0041] Ion implantation is a process in which oxygen ions are implanted into a diamond substrate to form a buried silicon dioxide (SiO2) oxide layer. This oxide layer not only serves as the release interface for subsequent diaphragm structures but also effectively isolates the electrical connection between the substrate and the diaphragm, improving sensor performance. The ion implantation parameters are as follows: Ion type: oxygen ions; Implantation energy: 50~150 keV. The implantation energy determines the implantation depth of oxygen ions in the diamond substrate, thus affecting the thickness of the buried oxide layer. Higher energy results in greater implantation depth and a thicker oxide layer. Implantation dose: 1×10¹⁶~1×10¹⁷ ions / cm². The implantation dose determines the number of oxygen ions implanted per unit area, thus affecting the density and quality of the oxide layer. Higher doses result in a denser oxide layer, but excessive doses may damage the diamond surface. Implantation angle: 0°. Vertical implantation ensures a uniform distribution of oxygen ions in the diamond substrate, which is beneficial for forming a flat oxide layer interface.

[0042] After ion implantation, the diamond substrate needs to undergo annealing to repair lattice damage caused during ion implantation and promote the reaction of oxygen ions with carbon atoms in the diamond to form silicon dioxide. Annealing is performed at high temperatures, typically using rapid annealing (RTA) to minimize the impact of thermal stress on the diamond substrate. Annealing parameters are as follows: Annealing temperature: 800~1000℃. The selection of the annealing temperature needs to balance oxide layer formation and the thermal stability of the diamond substrate. Too low a temperature will result in incomplete oxidation; too high a temperature may lead to graphitization and other adverse reactions in the diamond substrate. Annealing time: 5~30 minutes. The annealing time affects the thickness and density of the oxide layer. Longer times result in a thicker oxide layer, but excessively long annealing times may lead to overgrowth of the oxide layer, or even delamination from the diamond substrate. Using an inert gas such as nitrogen or argon for protection during annealing can prevent oxidation and other adverse reactions of the diamond substrate at high temperatures.

[0043] S3, Cantilever beam array and diaphragm are formed simultaneously.

[0044] Utilizing the anisotropic etching properties of oxygen plasma on diamond, three-dimensional gradient cantilever beam arrays and hyperboloid films can be fabricated simultaneously. Oxygen plasma etching is a dry etching process with advantages such as high etching rate, good selectivity, and strong anisotropic etching capability. During the etching process, oxygen plasma reacts chemically with carbon atoms in diamond to generate volatile gaseous products (such as CO and CO2), thereby achieving diamond etching. The anisotropic etching parameters of oxygen plasma are as follows: Gas flow rate: Oxygen flow rate is 20~50 sccm. The oxygen flow rate affects the concentration of oxygen plasma and the etching rate. The higher the flow rate, the higher the oxygen plasma concentration and the faster the etching rate. Reaction chamber pressure: 10~30 mTorr. The reaction chamber pressure affects the mean free path and energy distribution of the oxygen plasma. The lower the pressure, the longer the mean free path of the oxygen plasma, the higher the energy, the faster the etching rate, and the stronger the anisotropic etching capability. Radio frequency power: 100~300W. The radio frequency power affects the excitation efficiency and density of the oxygen plasma. Higher power results in higher oxygen plasma density and a faster etching rate. The etching rate is determined based on the geometry of the cantilever beam array and the diaphragm. Precise control of the etching time allows for the accurate shaping of the cantilever beam array and the diaphragm.

[0045] The cantilever beam array is radially distributed along the

[110] crystal direction, and the cross-sectional width of each cantilever beam decreases exponentially from the fixed end to the free end. This design can achieve directional stress transmission and signal amplification, improving the sensitivity of the sensor. The design parameters of the cantilever beam array are as follows: Crystal direction:

[110] crystal direction. The

[110] crystal direction is chosen as the extension direction of the cantilever beam because diamond has a large piezoresistive coefficient in the

[110] crystal direction, and the etching rate of the

[110] crystal plane by oxygen plasma is fast, which is conducive to forming a cantilever beam structure with an exponentially decreasing cross-sectional width. Radial distribution: The radial distribution of the cantilever beam array can expand the sensing area of ​​the sensor and improve the response capability to external pressure. Exponentially decreasing cross-sectional width: The cross-sectional width of the cantilever beam decreases exponentially from the fixed end to the free end.

[0046] The hyperboloid diaphragm is the core component of the pressure-sensitive structure, and its design directly affects the sensor's sensitivity and measurement range. The design parameters of the hyperboloid diaphragm are as follows: Shape: Hyperbolic. When subjected to external pressure, the hyperboloid diaphragm can undergo significant bending deformation, thereby improving the sensor's sensitivity. Thickness Distribution: The diaphragm thickness is distributed hyperbolically from the center to the edge. Stress Concentration Grooves: Periodic V-shaped stress concentration grooves are incorporated into the surface of the hyperboloid diaphragm. This further amplifies the diaphragm's bending deformation under external pressure, improving the sensor's sensitivity. The design parameters of the stress concentration grooves include groove depth, groove spacing, and groove angle.

[0047] S4, Stress Concentration Groove Machining

[0048] Ar / Cl2 mixed gas etching can be used to selectively etch diamond to create periodic V-shaped stress concentration grooves on hyperboloid films. Ar / Cl2 mixed gas etching is a reactive ion etching (RIE) process that combines the advantages of physical and chemical etching, offering high etching rates, good selectivity, and strong anisotropic etching capabilities. During etching, Ar ions bombard the diamond surface for physical etching, while Cl2 gas reacts chemically with carbon atoms in the diamond to generate volatile gaseous products (such as CCl4), achieving chemical etching. By adjusting the flow rate ratio of Ar to Cl2, different etching rates can be achieved for diamonds with different crystal orientations, thus realizing crystal orientation selective etching. The parameters for Ar / Cl2 mixed gas crystal orientation selective etching are as follows: Gas flow rate ratio: Ar:Cl2 flow rate ratio is 3:1~5:1. The Ar flow rate is higher than the Cl2 flow rate to ensure sufficient physical etching capability, while the Cl2 flow rate is sufficient for chemical etching. Reaction chamber pressure: 10~30 mTorr. The reaction chamber pressure affects the mean free path and energy distribution of the plasma, thus influencing the etching rate and anisotropic etching capability. RF power: 100~300 W. RF power affects the plasma excitation efficiency and density, which in turn affects the etching rate. The etching rate is determined based on the geometry of the stress concentration trench and the etching rate. Precise machining of the stress concentration trench can be achieved by precisely controlling the etching time.

[0049] The design of stress concentration grooves significantly impacts sensor sensitivity. The design parameters for stress concentration grooves are as follows: the ratio of groove depth to local diaphragm thickness is 0.4. The selection of groove depth must consider both sensor sensitivity and measurement range. If the groove depth is too shallow, the stress concentration effect is insignificant, and the sensitivity improvement is limited; if the groove depth is too deep, it may lead to a decrease in diaphragm strength and a reduction in measurement range. The ratio of groove spacing to the effective radius of the diaphragm is 0.2~0.35. The selection of groove spacing must consider both sensor sensitivity and spatial resolution. If the groove spacing is too small, the interaction between stress concentration grooves is enhanced, potentially leading to uneven diaphragm deformation; if the groove spacing is too large, the stress concentration effect is weakened, and the sensitivity improvement is limited. The groove angle of a V-groove is generally 60°~90°. The choice of groove angle affects the stress concentration effect and manufacturing difficulty. The smaller the groove angle, the more pronounced the stress concentration effect, but the greater the manufacturing difficulty; the larger the groove angle, the weaker the stress concentration effect, but the easier the manufacturing.

[0050] S5, Interface carrier mobility modulation

[0051] Atomic layer deposition (ALD) is a thin film deposition technique based on self-limiting surface reactions, offering advantages such as low deposition temperature, precise controllable film thickness, and good step coverage. This embodiment utilizes ALD to sequentially deposit Al2O3 and TiN layers on a hyperboloidal film surface, forming an Al2O3 / TiN composite transition layer. This allows for the regulation of the carrier mobility gradient distribution at the diamond / electrode contact interface, thereby improving sensor performance.

[0052] The Al2O3 layer is primarily used to regulate the interfacial density of states, reduce interfacial scattering, and improve carrier mobility. Trimethylaluminum (TMA) and deionized water (H2O) are used as precursors for Al2O3 layer deposition. The deposition parameters are as follows: TMA pulse time: H2O pulse time = 1:3. The pulse time ratio affects the deposition rate and stoichiometry of the Al2O3 layer. The deposition temperature is 200–300 °C. The deposition temperature affects the reactivity of the precursors and the crystallinity of the Al2O3 layer. The number of deposition cycles is 50–200. The number of deposition cycles determines the thickness of the Al2O3 layer. By adjusting the number of deposition cycles, the thickness of the Al2O3 layer can be precisely controlled between 2 and 5 nm.

[0053] The TiN layer is mainly used to optimize the carrier mobility gradient distribution and improve the interfacial conductivity. The TiN layer deposition uses tetratetra(dimethylamino)titanium (TDMAS) and ammonia (NH3) as precursors, and the deposition parameters are as follows: Precursors: tetratetra(dimethylamino)titanium (TDMAS) and ammonia (NH3).

[0054] The pulse time ratio of TDMAS to NH3 is 1:2. This pulse time ratio affects the deposition rate and stoichiometry of the TiN layer. The deposition temperature is 200–300 °C. The deposition temperature affects the reactivity of the precursor and the crystallinity of the TiN layer. The number of deposition cycles is 0–100. The number of deposition cycles determines the thickness of the TiN layer. By adjusting the number of deposition cycles, the thickness of the TiN layer can be precisely controlled between 0 and 3 nm. When the TiN layer thickness is 0, it indicates that no TiN layer is deposited, only an Al2O3 layer is deposited.

[0055] S6, Post-processing and Packaging

[0056] After the cantilever beam array and diaphragm are fabricated, the diaphragm needs to be released from the diamond substrate to form a suspended structure. Diaphragm release is achieved using a wet etching process, which utilizes hydrofluoric acid (HF) solution to etch the buried oxide layer, thereby releasing the diaphragm. The wet etching process parameters are as follows:

[0057] The concentration of hydrofluoric acid (HF) solution, ranging from 5% to 10%, is determined at room temperature based on the thickness of the buried oxide layer and the etching rate. Precise control of the etching time allows for accurate release of the film, avoiding over-etching or under-etching.

[0058] To improve the stability and reliability of the sensor, it needs to be encapsulated. The encapsulation material needs to have good chemical stability, thermal stability, and mechanical strength, while also requiring good compatibility with diamond materials. This embodiment uses silicon-based encapsulation technology to encapsulate the sensor chip on a silicon substrate and uses gold wire bonding technology to achieve electrical connections between the chip and external circuits. During the encapsulation process, the sensor also needs to be vacuum-sealed or oil-filled to protect it from the influence of the external environment.

[0059] Furthermore, this embodiment aims to investigate the influence of different groove depths and groove spacings of V-shaped stress concentration grooves on the sensitivity of diamond piezoresistive pressure-sensitive structures. Single-crystal diamond was selected as the substrate material for the experiment, and hydrogen plasma termination treatment was performed. In terms of structural design, following the original method, a buried oxide layer was formed on the diamond substrate, and a three-dimensional gradient cantilever beam array radially distributed along the

[110] crystal direction was fabricated. On the surface of the hyperboloid diaphragm, multiple sets of V-shaped stress concentration grooves with different groove depths and groove spacings were designed and fabricated. The groove depths were set to 0.35 times, 0.4 times, and 0.45 times the local thickness of the diaphragm, respectively, and the groove spacings were set to 0.2 times, 0.275 times, and 0.35 times the effective radius of the diaphragm, respectively. In terms of fabrication technology, anisotropic etching using oxygen plasma was employed to form the initial contours of the cantilever beam array and hyperboloid diaphragm. Then, crystal orientation-selective etching using an Ar / Cl2 mixed gas was used to fabricate V-shaped stress concentration grooves. Finally, atomic layer deposition (ALD) was used to deposit an Al2O3 / TiN composite transition layer on the hyperboloid diaphragm surface. For performance testing, the fabricated pressure-sensitive structure was placed in a pressure testing device, and the pressure was gradually increased. The resistance changes under different pressures were recorded, and the sensitivity of the structure under different combinations of groove depth and groove spacing were calculated and compared. It was found that the structure exhibited the highest sensitivity when the groove depth was 0.4 times the local thickness of the diaphragm and the groove spacing was 0.275 times the effective radius of the diaphragm. Analyzing the influence mechanism of different parameter combinations on sensitivity verified the accuracy of the theoretical model.

[0060] This embodiment can also be used to study the effect of different thickness combinations of Al2O3 and TiN layers on the carrier mobility at the diamond / electrode contact interface. Single-crystal diamond was used as the substrate material in the experiment, and pretreatment was performed. In terms of structural design, a buried oxide layer was formed on the diamond substrate, and a three-dimensional gradient cantilever beam array and a hyperboloid film were fabricated. Multiple Al2O3 / TiN composite transition layers of different thicknesses were designed and deposited on the surface of the hyperboloid film. The Al2O3 layer thicknesses were set to 2 nm, 3.5 nm, and 5 nm, respectively, and the TiN layer thicknesses were set to 0 nm (i.e., no TiN layer deposited), 1.5 nm, and 3 nm, respectively. In terms of processing technology, anisotropic etching was performed using oxygen plasma to form the initial contours of the cantilever beam array and the hyperboloid film. Then, crystal orientation selective etching was performed using an Ar / Cl2 mixed gas to fabricate V-shaped stress concentration grooves (the groove depth and spacing can be set to fixed values ​​in this step). Finally, atomic layer deposition (ALD) technology was used to deposit Al2O3 and TiN layers of specified thicknesses on different samples. During performance testing, the carrier mobility at the diamond / electrode interface under different composite transition layer thicknesses was measured using a four-probe method or a Hall effect meter, and the effects of different thickness combinations on carrier mobility were compared. It was found that the highest interfacial carrier mobility was achieved when the Al₂O₃ layer thickness was 3.5 nm and the TiN layer thickness was 1.5 nm. By analyzing the mechanism by which different thickness combinations affect carrier mobility, the role of the composite transition layer in regulating carrier mobility can be explored, and the parameters of the atomic layer deposition technique can be optimized based on the experimental results to improve the overall performance of the pressure-sensitive structure.

[0061] This invention achieves a synergistic enhancement of piezoresistive effect and structural mechanics by optimizing the diamond substrate processing technology, designing a three-dimensional gradient cantilever beam array and hyperboloid diaphragm structure, and combining atomic layer deposition technology to control the carrier mobility gradient distribution. This not only improves the sensitivity and stability of the pressure-sensitive structure but also enhances its corrosion resistance and wear resistance, while improving heat dissipation performance, providing a new solution for high-precision pressure measurement.

[0062] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A design method for a pressure-sensitive structure based on the diamond piezoresistive effect, characterized in that, The pressure-sensitive structure comprises a diamond substrate, a three-dimensional gradient cantilever beam array, and a hyperboloid diaphragm; the design steps include the following: S1. A buried oxide layer with a thickness of 200~500nm is formed on the diamond substrate by ion implantation, defining the mechanical isolation region of the diamond substrate; S2. The diamond substrate is anisotropically etched using oxygen plasma. By controlling the etching time difference, the three-dimensional gradient cantilever beam array is processed on the front side of the diamond substrate, while the initial contour of the hyperboloid film is formed on the back side of the diamond substrate. S3. Use a mixture of Ar / Cl2 gas to selectively etch the initial contour of the hyperboloid film, and process periodic V-shaped stress concentration grooves on the surface of the hyperboloid film. S4. Using atomic layer deposition technology, Al2O3 and TiN layers are sequentially deposited on the surface of the hyperboloid film to form an Al2O3 / TiN composite transition layer. By controlling the carrier mobility gradient distribution at the diamond / electrode contact interface, the synergistic enhancement of piezoresistive effect and structural mechanics is achieved.

2. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: The three-dimensional gradient cantilever beam array is radially distributed along the [110] crystal direction, wherein the beam cross-sectional width of each three-dimensional gradient cantilever beam decreases exponentially from the fixed end to the free end, and the width distribution satisfies the formula: In the formula, The width of the cantilever beam section; Let be the initial width of the fixed end of the cantilever beam; x is the coordinate along the length of the cantilever beam; and .

3. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: The geometric parameters of the groove depth and groove spacing of the V-shaped stress concentration groove satisfy the following relationship: the groove depth is set to 0.35 to 0.45 times the thickness of the hyperboloid diaphragm at the location; the groove spacing between adjacent V-shaped stress concentration grooves is controlled to be between 0.2 and 0.35 times the effective radius of the hyperboloid diaphragm.

4. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: The diamond substrate is made of single-crystal diamond material, and the surface of the single-crystal diamond material is subjected to hydrogen plasma termination treatment to form... / Hybrid bonding synthesis, with a thickness of 5-15 nm; the connection between the individual three-dimensional gradient cantilever beam and the hyperboloid film is provided with a rounded transition structure, with a radius of curvature of... It is used to eliminate stress singularities.

5. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: The hyperbolic membrane adopts a variable thickness design, and the thickness distribution satisfies: ； In the formula, The thickness of a local area of ​​the hyperboloid film; The thickness at the center of the hyperbolic film is 2 to 5. ; R is the thickness gradient coefficient, with a value ranging from 0.1 to 0.3; R is the effective radius of the hyperboloid film, with a value ranging from 100 to 300. ; r is the radial coordinate of a local position of the hyperboloid membrane.

6. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: The sidewall of the V-shaped stress concentration groove forms a [100] crystal orientation exposed surface, which, together with the [110] crystal orientation of the three-dimensional gradient cantilever beam array, constitutes a piezoresistive coefficient differential structure, such that the longitudinal piezoresistive coefficient and the transverse piezoresistive coefficient satisfy: ;in, This refers to the longitudinal piezoresistive coefficient. This is the lateral piezoresistive coefficient.

7. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: In step S3, the crystal orientation selective etching employs a two-step process, including: Step 1: Use SF6 plasma to etch the [110] crystal plane, the etching rate is 2 to 3 times higher than that of the [100] crystal plane; Step 2: Use C4F8 passivation to protect the sidewalls of the [100] crystal plane, and the perpendicularity of the groove sidewalls of the V-shaped stress concentration groove. .

8. The design method for a diamond piezoresistive pressure-sensitive structure according to claim 1, characterized in that: In step S4, the design parameters for the atomic layer deposition technology are: deposition temperature of 200~300℃; The deposition cycle is 50 to 200 times.

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