Capacitive semiconductor micro vacuum gauge and vacuum detection method

Abstract

The present invention discloses a capacitive semiconductor miniature vacuum gauge and a vacuum detection method. The vacuum gauge achieves high-precision, miniaturization and low power consumption in vacuum measurement by combining the electrical amplification characteristics of semiconductor devices with the capacitive sensing principle. The vacuum gauge fully utilizes the compatibility of standard CMOS processes and vertically integrates the air pressure sensing module with the signal processing unit. This not only simplifies the manufacturing process and reduces production costs, but also significantly improves the reliability and mass production potential of the device. By adjusting the electrode geometric parameters, the measurement range is further broadened and the sensitivity is optimized. The vacuum gauge has important practical value and broad commercial prospects, and provides an efficient and economical solution for the development of the next generation of miniature vacuum gauges.

Description

Technical Field

[0001] The present invention relates to a miniature vacuum gauge, in particular to a capacitive semiconductor miniature vacuum gauge, and also to a vacuum detection method implemented by using the above vacuum gauge. Background Art

[0002] A vacuum gauge is an instrument used to measure the air pressure or vacuum level within a closed environment. The measurement principle generally exploits the physical changes in gases under varying pressures. Currently, it is widely used in fields such as space exploration, heat treatment processing, and semiconductor precision instrumentation. Capacitive thin-film vacuum gauges are particularly well-received in the chemical and thin-film processing fields due to their excellent repeatability, rapid response, and accurate measurement capabilities over a range of approximately five orders of magnitude, from low vacuum to medium and high vacuum, independent of gas composition.

[0003] Many current vacuum gauges suffer from various drawbacks. For example, traditional vacuum gauges rely on mechanical or thermal principles, resulting in weak output signals and requiring complex signal amplification and processing circuitry. This not only increases system complexity but also introduces additional noise and errors, impacting measurement accuracy and stability. Traditional capacitive or thermal conductivity vacuum gauges, due to their complex structures and large size, struggle to meet the miniaturization demands of modern microelectronic systems, MEMS devices, or chip-level applications. Their large size limits their application in highly integrated environments (such as semiconductor manufacturing equipment and portable instruments), hindering seamless integration with micro- and nano-devices. Furthermore, the measurement range of existing vacuum gauges is often limited by their structural design or material properties, making them inflexible to adapt to varying vacuum requirements. For example, the sensitivity of Pirani vacuum gauges decreases significantly at extremely low pressures, while the measurement range of capacitive vacuum gauges is limited to the linear range of membrane deformation, lacking dynamic adjustability. Even miniature vacuum gauges (such as those based on MEMS technology) typically rely on complex micromachining processes, resulting in high manufacturing costs, long processing cycles, and difficulties in large-scale mass production. Furthermore, the low integration density of CMOS limits its widespread application in miniaturized systems. While some vacuum gauges utilize CMOS processes to integrate MEMS structures, these only exploit the ease of semiconductor integration at the packaging level, failing to fully utilize the electrical amplification properties of semiconductor devices (such as MOSFETs).

[0004] Currently, some vacuum gauges that integrate MEMS and CMOS processes, while offering certain miniaturization advantages, generally suffer from two key technical limitations: First, the sensing portion and signal processing unit are often physically isolated, failing to form effective electrical signal coupling. This results in a long signal path, and capacitance changes cannot directly drive the response device, leading to transmission losses and slow responses, making efficient electrical amplification difficult. Second, although some solutions integrate MEMS structures on a CMOS platform, most remain limited to structural integration, failing to fully exploit the electrical amplification capabilities of semiconductor devices such as MOSFETs. This results in them being relegated to peripheral auxiliary units rather than core sensing and conversion components. There is an urgent need to develop miniature vacuum gauges with significantly improved miniaturization, sensitivity, and accuracy. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to address the technical defects of existing vacuum gauges, such as insufficient accuracy and sensitivity, limited degree of miniaturization, fixed measurement range, high manufacturing cost, and insufficient utilization of the electrical characteristics of semiconductor devices. The present invention provides a capacitive semiconductor miniature vacuum gauge based on a semiconductor device structure, which combines the electrical amplification characteristics of semiconductor devices and the capacitive sensing principle, and significantly improves the sensitivity and accuracy of vacuum measurement while achieving high miniaturization of the device, as well as a vacuum detection method implemented by using the above vacuum gauge.

[0006] Technical solution: The capacitive semiconductor micro vacuum gauge of the present invention is composed of a signal conversion module on the bottom layer and an air pressure sensing module on the top layer, wherein the signal conversion module is composed of a substrate and a source and a drain arranged on the upper surface, and an air pressure sensing module is arranged between the source and the drain. The air pressure sensing module is composed of a dielectric isolation layer, a lower electrode, a sealing structure and a deformable upper electrode from bottom to top. The lower electrode, the deformable upper electrode and the sealing structure of the side wall package surround to form a vacuum cavity.

[0007] Among them, the materials of the deformable upper electrode and lower electrode are materials with good elasticity and conductivity, specifically aluminum, titanium, tantalum, copper, graphene conductive film or ceramic composite material film with a metallized surface, such as aluminum nitride film or zirconium oxide film; the selection of different materials can be customized according to the target sensitivity, mechanical stress requirements and temperature stability, thereby improving the adaptability and reliability of the device under extreme working conditions.

[0008] The inner height of the vacuum chamber is 0.1~1.5μm, and the vacuum degree is 0.9×10 -3 ~1.1×10 -3 Pa, with submicron packaging capabilities, can effectively shield external gas penetration and mechanical interference, and maintain internal pressure stability for a long time. The internal pressure of the cavity can be set to different reference values ​​according to application requirements (such as 10 -3 , 10 -2, 10 -1 Pa, etc.), to support absolute vacuum detection capabilities in different ranges. By adjusting the thickness of the sealing layer (range: 100~500nm) and the deposition method (such as LPCVD, PECVD, etc.), customized packaging can be achieved at various airtight levels, and the cavity leakage rate can be stably controlled at 10 -14 mbar·L / s or less, thus ensuring the device has excellent zero point stability and long-term repeatability in high vacuum or medium and low vacuum environments.

[0009] The deformable upper electrode is a single-layer membrane structure with a thickness of 10-50 nm and an area of ​​1.28-10 μm 2 , with rectangular or ring-shaped electrode structures. Different structures enable customized designs with varying ranges and sensitivities. For example: a ring electrode (radius 0.5-0.8μm, electrode-to-substrate area ratio 0.2-0.3:1).

[0010] The material of the sealing structure is a thin film material with high density and low permeability, specifically silicon nitride Si3N4 material, silicon dioxide SiO2, silicon oxynitride SiON, polyimide PI, glass or low-temperature deposited ceramic film, so as to adapt to the packaging stability requirements under different temperature, humidity or mechanical stress environments, and be compatible with multiple microelectronics manufacturing platforms.

[0011] The dielectric isolation layer is a silicon dioxide SiO2 insulating layer with a thickness of 20-30 nm.

[0012] The substrate is a silicon-based substrate with a length of 3 to 5 μm, a width of 1 to 2 μm, and a height of 0.7 to 0.9 μm. The area ratio of the deformable upper electrode to the silicon-based substrate is 0.42 to 0.5:1.

[0013] The signal conversion module is an enhancement MOSFET, the MOSFET static operating point is set in the saturation region, the drain voltage is set to 10V, and the dielectric isolation layer forms a voltage coupling with the lower electrode.

[0014] The capacitive semiconductor micro vacuum gauge can also adopt an array arrangement design. The capacitive semiconductor micro vacuum gauge is arranged in an array on a silicon substrate and shares a common drain or signal readout electrode; the response speed is improved, the error tolerance is increased, and the capacitance response sensitivity of the edge area is enhanced to adapt to a wider range of air pressure change environments.

[0015] The vacuum degree detection method for the capacitive semiconductor microvacuum gauge utilizes the current amplification characteristics of semiconductor devices to convert the charge disturbance caused by tiny capacitance changes into a significant output current signal, thereby achieving the amplification and mapping process of the signal from pico-farad capacitance changes to milliampere current. The method includes the following steps:

[0016] Step 1: Place the capacitive semiconductor micro vacuum gauge in a vacuum environment to be measured, so that a pressure difference is formed between the external air pressure and the internal reference air pressure of the vacuum chamber;

[0017] Step 2: The pressure difference causes the deformable upper electrode to elastically deform;

[0018] Step 3: The deformation changes the distance between the deformable upper electrode and the lower electrode, causing a change in the sensing capacitance;

[0019] Step 4: The dielectric isolation layer forms a voltage coupling with the lower electrode, and the capacitance change is coupled to the lower electrode through the dielectric isolation layer, thereby changing the voltage of the lower electrode;

[0020] Step 5: The drain voltage is set to 3.3-10V. Under a fixed drain voltage V_DS, the gate voltage change produces a significant drain current change through the MOSFET's transconductance gain g_m.

[0021] Step 6: The external vacuum degree can be calculated by detecting the drain current, achieving high-sensitivity measurement.

[0022] The capacitive semiconductor microvacuum gauge can be designed using a CMOS process platform or a lightweight MEMS-assisted process, eliminating the need for additional masks or non-mainstream materials. It offers excellent process compatibility, manufacturability, and process migration capabilities, facilitating direct deployment on existing chip platforms. The main process steps include:

[0023] (1) Set the substrate to 1×10 17 cm -3 The acceptor doping concentration (P type) is completed on the substrate. The ion implantation of the source and drain regions is completed on the substrate. The concentration is 1×10 20 cm -3 Donor doping (N-type);

[0024] (2) Deposit a gate dielectric layer (silicon dioxide, thickness: 20-30 nm) and smooth it by chemical mechanical polishing (CMP) to construct a dielectric isolation region;

[0025] (3) Forming the lower electrode through the metal interconnect layer (Al, thickness: 100-200 nm);

[0026] (4) Spin-coating a sacrificial layer material (such as polyimide PI), photolithography to form a cavity template (height: 0.1-1.5 μm), and depositing a metal film on top to form a deformable top electrode structure (Al, thickness: 10-50 nm);

[0027] (5) Use dry etching (such as RIE) to remove the sacrificial layer and release the vacuum cavity;

[0028] (6) Form a sealing structure (silicon nitride, thickness: 100~500nm) through methods such as LPCVD or PECVD to achieve the packaging of the vacuum cavity.

[0029] Principle of the Invention: The capacitive semiconductor microvacuum gauge of the present invention achieves high-precision, miniaturized, and low-power vacuum measurement by combining the electrical amplification characteristics of semiconductor devices with the principle of capacitive sensing. The device of the present invention utilizes the principle of coupling the compressive deformation of a diaphragm with a semiconductor amplifier element to achieve highly sensitive detection of the external vacuum level. When the device is in the test environment, a stable pressure differential forms between the external air pressure and a preset vacuum reference cavity within the device. This pressure differential acts on the upper electrode diaphragm, causing it to elastically deform, thereby changing the distance between the diaphragm and the fixed electrode, resulting in a change in capacitance. This capacitance change is coupled to the control terminal (e.g., gate) of a semiconductor device such as a MOSFET through a dielectric isolation structure disposed underneath, causing a small perturbation in the control terminal voltage. Within the operating range of the semiconductor device, this perturbation is effectively amplified into a significant current change, thereby converting small fluctuations in external air pressure into a readable electrical signal output.

[0030] This detection mechanism features fast response, strong output signal, and robust anti-interference capabilities, making it suitable for high-precision, low-power micro vacuum sensing applications. Furthermore, by collaboratively optimizing the diaphragm structure, capacitor unit, dielectric thickness, and semiconductor device parameters, the measurement sensitivity and response range can be flexibly adjusted according to application requirements, meeting the monitoring needs of various vacuum environments. This design leverages the compatibility of standard CMOS processes to vertically integrate the pressure sensing module with the signal processing unit. This not only simplifies the manufacturing process and reduces production costs, but also significantly improves device reliability and mass production potential. Its innovative structural design, including adjustable electrode geometry, further broadens the measurement range and optimizes sensitivity. The adjustable electrode here refers to the top electrode. Optimization methods primarily involve increasing the top electrode's area; a larger area results in more pronounced deformation at the same pressure, resulting in greater sensitivity; and modifying the top electrode's thickness; a thinner thickness increases the deformation at the same pressure, improving sensitivity. This increased thickness increases the maximum pressure the membrane can withstand, broadening the measurement range.

[0031] This invention, for the first time, utilizes MOSFET gate voltage perturbations as the core sensing mechanism. By incorporating a tightly coupled "pressure-sensing capacitor-gate-controlled input-drain amplification" mechanism into the device structure, it converts diaphragm deformation caused by tiny voltage differentials into capacitance changes. The capacitance signal, coupled through the dielectric layer, acts directly on the MOSFET gate, causing a small perturbation in the lower electrode voltage. This, when the device operates in the saturation region, drives an order of magnitude increase in the drain current, achieving an integrated "signal conversion-amplification" response path from pico-farad capacitance changes to milliampere current output. This mechanism effectively overcomes the technical bottlenecks of traditional solutions, such as lengthy signal chains, slow response times, and high external dependencies, significantly improving the device's response speed, sensitivity, and signal strength. Its structural design fully considers compatibility with existing integrated circuit manufacturing processes. Both the capacitance sensing unit and the semiconductor amplification module can be implemented through fine-tuning and reconfiguration of the metal interconnect layer, via structure, and dielectric layer thickness within a standard CMOS process flow. This eliminates the need for additional masks or specialized materials, allowing device manufacturing to be completed on existing production lines. This solution is not only applicable to 0.18μm and below node processes, but can also be expanded to SoC or MEMS-CMOS hybrid integration platforms. It boasts excellent manufacturability and cross-platform process migration capabilities. It can be widely used in process chamber monitoring of semiconductor manufacturing equipment, in-cabin vacuum state management of space probes, miniature mass spectrometers, online feedback control of vacuum coating systems, and integrated chip-level environmental monitoring modules. It is particularly well-suited for applications with limited size or extremely high requirements for response speed and sensitivity. It has significant practical value and broad commercial prospects, providing an efficient and economical solution for the development of next-generation miniature vacuum gauges.

[0032] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0033] (1) The capacitive semiconductor micro vacuum gauge of the present invention has high sensitivity and high precision, which can convert small capacitance changes (deformation of the upper electrode caused by pressure difference) into significant drain current changes (milliampere level), and can achieve 1×10 -4 High-precision measurement in the vacuum range of Pa to 100 Pa, with output signal strength up to milliampere level and sensitivity improved by 1~2 orders of magnitude;

[0034] (2) The vacuum gauge also has dynamic adjustment capabilities: by adjusting the diaphragm material parameters and geometric dimensions, the measurement range and sensitivity can be flexibly customized to suit different application requirements;

[0035] (3) The vacuum gauge also has miniaturization and system integration capabilities. The device size is controlled within the submicron range. The MOSFET amplification unit and the capacitive sensing structure adopt a vertical integration layout, which is suitable for CMOS chip-level integration and has excellent miniaturization characteristics and system compatibility.

[0036] (4) The vacuum gauge also has low power consumption and high stability: it only needs to apply voltage (V_DS) to the drain to drive it, without the need for additional excitation signals or complex peripheral circuits, and its power consumption is significantly lower than that of the traditional Pirani vacuum gauge;

[0037] (5) The vacuum gauge also has the potential for low-cost and mass production: all process steps are compatible with standard CMOS processes, do not require special materials or complex micromachining technology, are suitable for large-scale mass production, and significantly reduce manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the structure of the capacitive semiconductor micro vacuum gauge of the present invention;

[0039] Figure 2 is a three-dimensional diagram of a capacitive semiconductor micro vacuum gauge of the present invention;

[0040] Figure 3 A three-dimensional diagram of the annular electrode structure of the capacitive semiconductor micro vacuum gauge of the present invention;

[0041] Figure 4 A three-dimensional diagram of the array structure of a capacitive semiconductor micro vacuum gauge according to the present invention;

[0042] Figure 5 Schematic diagram of the structural deformation of the micro vacuum gauge under the action of external air pressure;

[0043] Figure 6 is the doping concentration diagram;

[0044] Figure 7 This is the electron concentration diagram of the micro vacuum gauge under working conditions;

[0045] Figure 8 This is the pressure-drain current curve under high vacuum pressure;

[0046] Figure 9 This is the pressure-drain current curve under medium vacuum range pressure;

[0047] Among them, 1-signal conversion module, 11-substrate, 12-source, 13-drain, 2-air pressure sensing module, 21-dielectric isolation layer, 22-lower electrode, 23-sealing structure, 24-vacuum cavity, 25-deformable upper electrode. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below with reference to the examples. The test materials used in the examples can all be purchased through conventional channels.

[0049] Example 1

[0050] The capacitive semiconductor micro vacuum gauge of the present invention is as follows Figure 1 and Figure 2 As shown, it consists of a signal conversion module 1 at the bottom layer and an air pressure sensing module 2 at the top layer, wherein the signal conversion module 1 consists of a substrate 11 and a source 12 and a drain 13 arranged on the upper surface, and an air pressure sensing module 2 is arranged between the source 12 and the drain 13. The air pressure sensing module 2 is composed of a dielectric isolation layer 21, a lower electrode 22, a sealing structure 23 and a deformable upper electrode 25 from bottom to top. The lower electrode 22, the deformable upper electrode 25 and the sealing structure 23 encapsulated by the side wall surround a vacuum cavity 24.

[0051] The deformable upper electrode 25 and lower electrode 22 are aluminum films. The interior height of the vacuum chamber 24 is 0.1 μm. The thickness of the deformable upper electrode 25 is 10 nm. The sealing structure 23 is made of silicon nitride (Si3N4). The dielectric isolation layer 21 is a 20 nm thick silicon dioxide (SiO2) insulating layer. The substrate 11 is a silicon-based substrate with a length of 5 μm, a width of 2 μm, and a height of 0.9 μm. The area ratio of the deformable upper electrode to the silicon-based substrate is approximately 0.5:1.

[0052] The signal conversion module 1 is an enhancement-mode MOSFET; the operating point is set in the saturation region, the drain voltage is 10V, and the dielectric isolation layer 21 and the lower electrode 22 form a voltage coupling.

[0053] Example 2

[0054] The capacitive semiconductor micro vacuum gauge of the present invention is as follows Figure 3 As shown, the deformable upper electrode 25 is a ring electrode structure with a radius of 0.8 μm and an area ratio of 0.3:1 to the substrate. Its inner diameter is 0.5 μm and the outer diameter is 0.8 μm. The area ratio of the entire electrode to the silicon substrate is 0.3:1.

[0055] The ring-shaped electrode structure redistributes the capacitive response weight across the electrode area on the diaphragm, increasing the contribution of deformation in the edge region to overall capacitance changes, helping to improve sensitivity to small pressure differentials. Furthermore, compared to solid electrodes, this structure offers greater geometric adjustability and can be optimized for different diaphragm materials and sizes, adapting to a variety of sensing scenarios requiring high accuracy and linearity.

[0056] Example 3

[0057] The capacitive semiconductor micro vacuum gauge of the present invention is as follows Figure 4As shown, the capacitive semiconductor microvacuum gauge utilizes an arrayed structure, with multiple independent vacuum detection units evenly distributed on a single silicon substrate 11. Each unit shares a common drain or signal readout electrode. This design allows for simultaneous sampling by multiple vacuum gauges and establishes a redundant fault-tolerant mechanism, maintaining overall measurement stability in the event of sudden atmospheric pressure changes or localized failures. Furthermore, the multi-point layout improves spatial sampling accuracy, enabling faster pressure response times and higher error tolerance.

[0058] Example 4

[0059] The capacitive semiconductor microvacuum gauge of the present invention supports multi-dimensional implementation plans. It can use standard CMOS processes to carry out device tape-out and physical testing, and can also perform virtual modeling and performance prediction based on multi-physics field simulation platforms (such as COMSOL and ANSYS), thereby realizing the unification of theoretical analysis and engineering implementation.

[0060] COMSOL Multiphysics software was used to conduct multi-physics coupling simulation analysis to verify the working mechanism and performance of the high-sensitivity capacitive semiconductor micro vacuum gauge based on MOSFET structure proposed in this paper:

[0061] Modeling and studying the device's electrical response, structural deformation, and its coupling relationship with capacitance changes under different vacuum environments include the following steps:

[0062] Step 1. Simulation model construction

[0063] The COMSOL Multiphysics 6.2 software platform was selected, with the Semiconductor Module, Solid Mechanics Module, Electrostatics Module, and Dynamic Mesh Module activated to achieve coupled simulation of electric fields, force fields, and structural deformation.

[0064] The simulation structure includes:

[0065] Bottom layer: Si-based substrate and MOSFET main structure (source, drain, gate and its contact layer);

[0066] Top layer: SiO2 insulating layer and metal fixed electrode (lower electrode); deformable aluminum film (upper electrode), vacuum cavity and silicon nitride sidewall sealing layer;

[0067] The structural dimension parameters are set as follows: silicon oxide layer thickness 30 nm, vacuum chamber height 0.1 μm, leakage voltage 10 V, substrate width 0.7 μm, etc.

[0068] The material model includes silicon (Si), silicon dioxide (SiO2), aluminum (Al), silicon nitride (Si3N4) and a relative vacuum layer, which are given corresponding thermal, mechanical and electrical properties respectively.

[0069] Step 2. Material parameter setting and multiphysics coupling setup

[0070] Material selection type

[0071] The material model includes silicon (Si), silicon dioxide (SiO2), aluminum (Al), silicon nitride (Si3N4) and a relative vacuum layer, which are given corresponding electrostatic, mechanical and semiconductor properties respectively;

[0072] Key physical parameters

[0073] To adapt to multi-physics coupling analysis, the following key parameters need to be defined in the material:

[0074] Table 1. Silicon material parameters

[0075]

[0076] Table 2. Silica material parameters

[0077]

[0078] Table 3. Aluminum material parameters

[0079]

[0080] Table 4. Vacuum material parameters

[0081]

[0082] Table 5. Silicon nitride material parameters

[0083]

[0084] Coupled physics settings:

[0085] Semiconductor module: Set up the NMOS enhancement mode transistor structure, define the source, drain and metal contact boundaries, doping concentration and range, and use the trap-assisted recombination mechanism for carrier recombination;

[0086] Electrostatic module: used to simulate the potential distribution and capacitance changes between the upper and lower electrodes;

[0087] Solid Mechanics Module: Defines the elastic deformation behavior of the upper electrode and applies different external air pressures to simulate changes in the vacuum environment;

[0088] Dynamic mesh module: used to deal with geometric nonlinear effects caused by diaphragm deformation.

[0089] Step 3: Meshing and dynamic mesh optimization

[0090] To achieve high-precision modeling and efficient solution of devices under multi-physics coupling conditions, the adaptive meshing strategy in COMSOL Multiphysics was adopted, and a dynamic mesh mechanism was introduced to adapt to the geometric deformation of the vacuum cavity area.

[0091] Semiconductor active region (MOSFET channel, source and drain regions): uses a medium-density free grid with a cell size of approximately 10 nm to ensure accurate calculation of electric field strength, carrier concentration, and current density to meet the requirements of electrical performance simulation;

[0092] Gate dielectric and metal layer areas: There is a significant potential gradient between the dielectric layer and the electrode, so local densification is required. The grid size is approximately 3-5 nm to ensure the ability to resolve capacitance changes under different operating conditions.

[0093] Peripheral silicon substrate and mechanical support structure: Since stress distribution in this area is relatively uniform, the mesh size can be relaxed to 20-30 nm to reduce the overall model size and improve simulation efficiency.

[0094] Dynamic Mesh Region (vacuum cavity and its upper and lower boundaries): This region corresponds to the elastic deformation of the upper electrode under the action of gas pressure. To capture its nonlinear displacement and capacitance changes, the dynamic mesh module automatically tracks the boundary position. The initial mesh uses a structured or free mesh layout, with a cell size controlled between 1 and 5 nm. During the simulation, the mesh is reconstructed in real time as the upper electrode deforms, closely matching the boundary curvature changes and effectively avoiding simulation divergence or loss of accuracy.

[0095] The total number of grid cells in the final simulation model was controlled between approximately 1.5 million and 2 million cells, taking into account both the simulation accuracy of the device's key response areas and the optimization of overall computing resources, ensuring good coupling consistency among the three-field results of deformation, capacitance, and current response.

[0096] Step 4: Parameter sweep and boundary condition setting

[0097] To investigate the electrical response of the device under different vacuum levels, a parameter sweep of the external pressure P0 was performed, covering the following range:

[0098] Study 1: P0 from 0 Pa to 100 Pa, with a step of 0.1;

[0099] Study 2: Fine scanning of P0 from 0 Pa to 1e-3 Pa in the low-pressure region with a step of 1e-5;

[0100] In the simulation, the free boundary of the diaphragm is considered, the bottom electrode is grounded, the top electrode is set as a variable terminal, and the MOSFET gate voltage is coupled to the bottom electrode potential through capacitance.

[0101] Step 5: Simulation results and performance analysis

[0102] Structural deformation response: As the air pressure increases, the upper electrode diaphragm undergoes visible downward elastic deformation, with the center displacement being the largest, and the displacement increases nonlinearly with the pressure difference;

[0103] Changes in lower plate voltage: The lower plate voltage increases significantly as the diaphragm sinks, forming a functional relationship that can be fitted with pressure.

[0104] Current response characteristics: While maintaining a constant source-drain voltage (Vds = 10V), the drain current Id varies significantly with gate voltage. Simulations show that the structure has an output gain of >100 times and a current signal strength of milliamperes, making it suitable for direct post-processing readout.

[0105] Pressure response range: The simulation display device can achieve 1×10 -4 High-sensitivity continuous detection in the range of Pa to 100 Pa, with significant current response, facilitates subsequent electronic acquisition and processing.

[0106] Final result:

[0107] Measuring range: 1×10 -4 High-precision measurement in the vacuum range from Pa to 100 Pa;

[0108] Signal strength and sensitivity: The output signal strength is as high as milliampere level, and the sensitivity is improved by 1~2 orders of magnitude;

[0109] Dynamic adjustment capability: By adjusting the diaphragm material parameters and geometric dimensions, the measurement range and sensitivity can be flexibly customized to suit different application requirements;

[0110] Miniaturization and system integration capabilities: The device size is controlled within the sub-micron range, and the MOSFET amplification unit and capacitive sensing structure adopt a vertical integration layout, which is suitable for CMOS chip-level integration and has excellent miniaturization characteristics and system compatibility.

[0111] like Figure 5 Figure 2 shows a schematic diagram of the structural deformation of a micro vacuum gauge under external air pressure. The deformable upper electrode 25 undergoes significant elastic deformation under external air pressure, with the center region experiencing the largest downward displacement. The deformation amplitude decreases gradually from the center to the edge. As the upper electrode deforms, the spacing between it and the fixed lower electrode 22 changes, causing a corresponding change in the capacitance of the capacitor formed by the two. The rigid support provided by the sealing structure 23 ensures that deformation is primarily concentrated in the center of the upper electrode, while effectively constraining deformation at the edge of the deformable upper electrode.

[0112] like Figure 6The figure shows the doping concentration diagram, which shows the key doping distribution characteristics of the semiconductor substrate in the micro vacuum gauge. The figure uses different colors to mark the P-type and N-type doping areas: the blue area indicates the concentration of 1×10 17 cm⁻³ acceptor doping (P-type), mainly distributed in the substrate and channel region (i.e., below the lower plate); the red area indicates a concentration of 1×10 20 The 100 cm⁻³ donor dopant (N-type) is concentrated in the region below the source and drain. This combination of high-concentration N+ doping (source and drain regions) and a lightly doped P-type channel forms a typical enhancement-mode NMOS structure. The steep concentration gradient in the doping transition region demonstrates the process control of ion implantation.

[0113] like Figure 7 Figure 2 shows the electron concentration of the micro vacuum gauge under operating conditions, demonstrating the conduction characteristics of the channel region during operation. The figure shows that when a 10V drain voltage and an appropriate bottom electrode voltage are applied, a clear electron conduction channel forms in the channel region, manifesting as a bright stripe-like structure.

[0114] like Figure 8 and Figure 9 The following is a pressure-drain current curve, showing the electrical response characteristics of the device under different vacuum levels. It can be observed in the figure that when the pressure reaches 0.00005 Pa (high vacuum range), the drain current begins to change detectably, indicating that the device has entered the effective detection range. As the pressure continues to rise, the current response shows a steady upward trend. In the medium vacuum range (1×10 -1 ~1×10 2 The change is more obvious, and the output current changes in the milliampere level. This can achieve the condition that the device operates in the saturation region, drive the drain current to increase by an order of magnitude, and realize the "signal conversion-amplification integration" response path from pico-farad capacitance change to milliampere current output.

[0115] Therefore, the present invention proposes a highly sensitive capacitive micro vacuum gauge based on a semiconductor device structure. By combining the electrical amplification characteristics of semiconductor devices with the capacitive sensing principle, high-precision, miniaturized, and low-power vacuum measurement is achieved. This design fully utilizes the compatibility of standard CMOS processes and vertically integrates the air pressure sensing module with the signal processing unit. This not only simplifies the manufacturing process and reduces production costs, but also significantly improves the reliability and mass production potential of the device. Its innovative structural design, such as adjustable electrode geometric parameters, further broadens the measurement range and optimizes sensitivity. It has important practical value and broad commercial prospects, providing an efficient and economical solution for the development of the next generation of micro vacuum gauges.

Claims

1. A capacitive semiconductor micro vacuum gauge, characterized in that: The capacitive semiconductor micro vacuum gauge is composed of a signal conversion module (1) at the bottom layer and an air pressure sensing module (2) at the top layer, wherein the signal conversion module (1) is composed of a substrate (11) and a source electrode (12) and a drain electrode (13) arranged on the upper surface, and an air pressure sensing module (2) is arranged between the source electrode (12) and the drain electrode (13), and the air pressure sensing module (2) is composed of a dielectric isolation layer (21), a lower electrode (22), a sealing structure (23) and a deformable upper electrode (25) from bottom to top, and the lower electrode (22), the deformable upper electrode (25) and the sealing structure (23) encapsulated by the side wall surround a vacuum cavity (24).

2. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The deformable upper electrode (25) and the lower electrode (22) are made of aluminum, titanium, tantalum, copper, a graphene conductive film, or a ceramic composite material film with a metallized surface layer.

3. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The inner height of the vacuum chamber (24) is 0.1-1.5 μm, and the vacuum degree is 0.9×10 -3 ~1.1×10 -3 Pa.

4. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The thickness of the deformable upper electrode (25) is 10-50 nm, and the area is 1.28-10 μm 2 , the shape is a rectangular or ring electrode structure.

5. The capacitive semiconductor micro vacuum gauge according to claim 4, characterized in that: The radius of the annular electrode is 0.5-0.8 μm, and the area ratio of the electrode to the substrate is 0.2-0.3:

1.

6. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The material of the sealing structure (23) is silicon nitride Si3N4, silicon dioxide SiO2, silicon oxynitride SiON, polyimide PI, glass or low-temperature deposited ceramic film.

7. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The dielectric isolation layer (21) is a silicon dioxide SiO2 insulating layer with a thickness of 20-30 nm.

8. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The substrate (11) is a silicon-based substrate.

9. The capacitive semiconductor micro vacuum gauge according to claim 1, wherein: The capacitive semiconductor micro vacuum gauges are arranged in an array on a substrate (11).

10. A method for detecting vacuum degree of a capacitive semiconductor micro vacuum gauge according to claim 1, characterized in that: The following steps are involved: Step 1: Place the capacitive semiconductor micro vacuum gauge in a vacuum environment to be measured, so that a pressure difference is formed between the external air pressure and the internal reference air pressure of the vacuum chamber; Step 2: The pressure difference causes the deformable upper electrode to elastically deform; Step 3: The deformation changes the distance between the deformable upper electrode and the lower electrode, causing a change in the sensing capacitance; Step 4: The dielectric isolation layer forms a voltage coupling with the lower electrode, and the capacitance change is coupled to the lower electrode through the dielectric isolation layer, thereby changing the voltage of the lower electrode; Step 5: The drain voltage is set to 3.3-10V. Under a fixed drain voltage V_DS, the gate voltage change produces a significant drain current change through the MOSFET's transconductance gain g_m. Step 6: The external vacuum degree can be calculated by detecting the drain current, achieving high-sensitivity measurement.

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