Capacitive semiconductor miniature vacuum gauge and vacuum detection method

Abstract

The invention discloses a capacitive semiconductor miniature vacuum gauge and a vacuum detection method, and the vacuum gauge achieves the high precision, miniaturization and low power consumption of vacuum measurement through the combination of the electrical amplification characteristic of a semiconductor device and a capacitive sensing principle, makes full use of the compatibility of a standard CMOS technology, and improves the measurement precision. The air pressure sensing module and the signal processing unit are vertically integrated, so that the manufacturing process is simplified, the production cost is reduced, the reliability and the mass production potential of the device are remarkably improved, the measurement range is further widened and the sensitivity is optimized by adjusting the geometric parameters of the electrode, and the sensor has important practical value and wide commercial prospect and is worthy of popularization and application. And an efficient and economic solution is provided for the development of the next generation of miniature vacuum gauges.

Description

Technical Field

[0001] The present invention relates to a micro-vacuum gauge, and more particularly to a capacitive semiconductor micro-vacuum gauge, and also relates to a vacuum detection method implemented by using the above vacuum gauge. Background Art

[0002] A vacuum gauge is an instrument for detecting the air pressure or vacuum degree in a closed environment. The measurement principle generally utilizes a certain physical change effect of a gas under different air pressures for response. Currently, it has wide applications in fields such as outer space aerial survey, heat treatment processing, and semiconductor precision instruments. Among them, the capacitive thin-film vacuum gauge is valued in the chemical and thin-film process fields because of its good repeatability, ability to meet the requirements of high-speed response and accurate measurement in a range of about 5 orders of magnitude from low vacuum to medium-high vacuum, and its independence from gas components.

[0003] Currently, various existing vacuum gauges all have various defects. For example, traditional vacuum gauges mostly rely on mechanical or thermal principles, and the output signals are usually weak, requiring complex signal amplification and processing circuits. This not only increases the system complexity but also introduces additional noise and errors, affecting the accuracy and stability of measurement. Traditional capacitive or thermal conductivity vacuum gauges are difficult to meet the requirements of miniaturization in modern microelectronic systems, MEMS devices, or chip-level applications due to their complex structures or large volumes. Their large sizes limit their applications in high-integration environments (such as semiconductor manufacturing equipment, portable instruments, etc.) and cannot achieve seamless integration with micro-nano devices. Moreover, the measurement ranges of existing vacuum gauges are usually limited by their structural designs or material properties and cannot flexibly adapt to the requirements of different vacuum degree environments. For example, the sensitivity of a Pirani vacuum gauge significantly decreases at extremely low air pressures, while the measurement range of a capacitive vacuum gauge is limited by the linear range of film deformation and lacks dynamic adjustability. Even micro-vacuum gauges (such as Pirani vacuum gauges based on MEMS technology) usually rely on complex microfabrication processes, resulting in high manufacturing costs, long processing cycles, and difficulty in achieving large-scale mass production. In addition, the CMOS integration degree is relatively low, restricting its wide application in miniaturized systems. Although some vacuum gauges integrate MEMS structures using CMOS processes, they only utilize the easy integration characteristic of semiconductors and play a role at the packaging level, without fully utilizing the electrical amplification characteristics of semiconductor devices (such as MOSFETs).

[0004] At present, some vacuum gauges that integrate MEMS and CMOS processes have certain miniaturization advantages, but generally have two key technical limitations: First, the sensing part and the signal processing unit are often physically isolated and cannot form an effective electrical signal coupling, resulting in a long signal path and the inability to directly drive the response device due to capacitance changes, thus causing problems such as transmission loss and slow response, and it is difficult to achieve efficient electrical amplification; Second, although some solutions use the CMOS platform to integrate the MEMS structure, most are still limited to the integration at the structural level and have not deeply explored the electrical amplification capabilities of semiconductor devices such as MOSFETs, making them only exist as peripheral auxiliary units rather than core sensing and conversion elements. There is an urgent need to develop a micro-vacuum gauge with greatly improved miniaturization, sensitivity, and accuracy. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a capacitive semiconductor micro-vacuum gauge based on a semiconductor device structure and a vacuum detection method implemented by using the above vacuum gauge, which combines the electrical amplification characteristics of semiconductor devices and the capacitive sensing principle, significantly improves the sensitivity and accuracy of vacuum measurement while achieving high miniaturization of the device, aiming at the technical defects of existing vacuum gauges such as insufficient accuracy and sensitivity, limited miniaturization, fixed measurement range, high manufacturing cost, and failure to fully utilize the electrical characteristics of semiconductor devices.

[0006] Technical Solution: The capacitive semiconductor micro-vacuum gauge of the present invention is composed of a signal conversion module at the bottom layer and a gas pressure sensing module at the top layer. Among them, the signal conversion module is composed of a substrate and a source electrode and a drain electrode arranged on the upper surface. A gas pressure sensing module is provided between the source electrode and the drain electrode. The gas pressure sensing module includes a dielectric isolation layer, a lower electrode, a sealing structure, and a deformable upper electrode from bottom to top in sequence. A vacuum cavity is formed by surrounding the lower electrode, the deformable upper electrode, and the sealing structure encapsulated on the side walls.

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

[0008] The internal height of the vacuum cavity is 0.1 - 1.5 μm, and the vacuum degree is 0.9×10 -3 ~1.1×10 -3 Pa, with sub-micron packaging ability, which can effectively shield external gas penetration and mechanical interference and maintain the internal gas pressure stability for a long time. The internal gas pressure of this cavity can be set to different reference values according to application requirements (such as 10 -3 、10 -2, 10 -1 Pa, etc.), to achieve support for 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 that 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 , the shape is rectangular or annular electrode structure. Different structures can realize customized design of different ranges and sensitivities. For example: annular electrode (radius is 0.5~0.8μm, and the area ratio of electrode to substrate is 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 a variety of 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 3-5 μm, a width of 1-2 μm, and a height of 0.7-0.9 μm. The area ratio of the deformable upper electrode to the silicon-based substrate is 0.42-0.5:1.

[0013] The signal conversion module is an enhanced MOSFET, the static operating point of the MOSFET 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-based 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 of the capacitive semiconductor micro vacuum gauge utilizes the current amplification characteristics of semiconductor devices to convert the charge disturbance caused by the tiny capacitance change into a significant output current signal, thereby realizing the amplification and mapping process of the signal from the pico-farad capacitance change to the milliampere current, and includes the following steps: Step 1: Place the capacitive semiconductor micro-vacuum gauge in the vacuum environment to be measured, and a pressure difference is formed between the external air pressure and the internal reference pressure of the vacuum chamber. Step 2: This pressure difference causes the deformable upper electrode to undergo elastic deformation. 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 and the lower electrode form voltage coupling, and the capacitance change is coupled to the lower electrode through the dielectric isolation layer, changing the voltage of the lower electrode. Step 5: Set the drain voltage to 3.3 - 10 V. Under a fixed drain voltage V_DS, the change in the gate voltage generates a significant change in the drain current through the transconductance gain g_m of the MOSFET. Step 6: By detecting the magnitude of the drain current, the external vacuum degree can be measured, realizing high-sensitivity measurement.

[0016] The above capacitive semiconductor micro-vacuum gauge can be designed through a CMOS process platform or a lightweight MEMS-assisted process. Without introducing additional mask plates or non-mainstream materials, it has excellent process compatibility, mass producibility, and process migration ability, facilitating direct deployment on existing chip platforms. The main process steps include: (1) Set the substrate to have an acceptor doping (P-type) with a concentration of 1×10 17 cm -3 and complete ion implantation in the source and drain regions on the substrate with a donor doping (N-type) concentration of 1×10 20 cm -3 . (2) Deposit a gate dielectric layer (silicon dioxide, thickness: 20 - 30 nm) and planarize it through chemical mechanical polishing (CMP) to construct a dielectric isolation region. (3) Form the lower electrode (Al, thickness: 100 - 200 nm) through a metal interconnection layer. (4) Spin-coat a sacrificial layer material (such as polyimide PI), lithographically form a cavity template (height: 0.1 - 1.5 μm), and deposit a metal thin film on it to form a deformable upper electrode structure (Al, thickness: 10 - 50 nm). (5) Use dry etching (such as RIE) to remove the sacrificial layer and release the vacuum chamber. (6) Form a sealing structure (silicon nitride, thickness: 100 - 500 nm) through methods such as LPCVD or PECVD to achieve the encapsulation of the vacuum chamber.

[0017] Principle of the Invention: The capacitive semiconductor micro-vacuum gauge of the present invention combines the electrical amplification characteristics of semiconductor devices with the capacitive sensing principle to achieve high-precision, miniaturization, and low power consumption in vacuum measurement. The device of the present invention is based on the principle of coupling the deformation of the diaphragm under pressure with semiconductor amplification devices to achieve highly sensitive detection of the external vacuum degree. When the device is in the environment to be measured, a stable pressure difference is formed between the external air pressure and the preset vacuum reference cavity inside the device. This pressure difference acts on the upper electrode diaphragm, causing it to undergo elastic deformation, thereby changing the distance between the diaphragm and the fixed electrode, resulting in a change in the capacitance value. This capacitance change is coupled to the control terminal (such as the gate) of semiconductor devices such as MOSFETs through the dielectric isolation structure provided below, causing a slight perturbation in the control terminal voltage. Within the operating range of the semiconductor device, this perturbation will be effectively amplified into a significant current change, so that the slight fluctuation of the external air pressure is converted into a readable electrical signal output.

[0018] The above detection mechanism has the characteristics of fast response speed, strong output signal, and strong anti-interference ability, and is suitable for high-precision and low-power micro-vacuum degree sensing scenarios. At the same time, by synergistically optimizing the diaphragm structure, capacitance unit, dielectric thickness, and semiconductor device parameters, the measurement sensitivity and response range can be flexibly adjusted according to application requirements to meet the monitoring needs of various vacuum environments. This design makes full use of the compatibility of the standard CMOS process to vertically integrate the air pressure sensing module and the signal processing unit, which not only simplifies the manufacturing process, reduces the production cost, 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 the sensitivity. Among them, the adjustable electrode here refers to the upper electrode, and its optimization methods are mainly as follows: increasing the area of the upper electrode, the larger the area, the more obvious its deformation under the same air pressure, and the more sensitive the perception; modifying the thickness of the upper electrode, thinning the thickness can increase the deformation amount under the same air pressure and improve the sensitivity. And thickening the thickness makes the maximum pressure that the thin film can withstand larger, broadening the measurement range.

[0019] The present invention first proposes to use the gate voltage perturbation of MOSFET as the sensing core. By introducing a tight coupling mechanism of "pressure-sensitive capacitor - gate-controlled input - drain amplification" in the device structure, the diaphragm deformation caused by a tiny pressure difference is converted into a capacitance value change. The capacitance signal is directly coupled through the dielectric layer to the MOSFET gate, causing a perturbation in the lower electrode voltage. Under the condition that the device operates in the saturation region, the drain current is driven to increase by an order of magnitude, realizing a "signal conversion - amplification integration" response path from picofarad-level capacitance change to milliampere-level current output. This mechanism effectively breaks through the technical bottlenecks in traditional solutions, such as long signal chains, slow response, and high external dependence, and greatly improves the response speed, sensitivity, and signal strength of the device. Its structural design fully considers compatibility with existing integrated circuit manufacturing processes. Both the capacitance sensing unit and the semiconductor amplification module can be realized by fine-tuning and reconstructing the metal interconnection layer, via structure, and dielectric layer thickness in the standard CMOS process flow, without introducing additional masks or special materials, and the device manufacturing can be completed on the existing production line. This solution is not only applicable to processes with nodes of 0.18μm and below, but also can be extended to SoC or MEMS-CMOS hybrid integration platforms, with excellent mass producibility and cross-platform process migration capabilities. It can be widely used in the process chamber monitoring of semiconductor manufacturing equipment, the in-cabin vacuum state management of space detectors, micro mass spectrometers, the online feedback control of vacuum coating systems, and integrated chip-level environmental monitoring modules, and is particularly suitable for scenarios with limited volume or extremely high requirements for response speed and sensitivity. It has important practical value and broad commercial prospects, providing an efficient and economical solution for the development of the next-generation micro-vacuum gauge.

[0020] Advantages: Compared with the prior art, the present invention has the following remarkable advantages: (1) The capacitive semiconductor micro-vacuum gauge of the present invention has high sensitivity and high precision, converting a tiny capacitance change (the deformation of the upper electrode caused by the pressure difference) into a significant drain current change (milliampere level), and can achieve high-precision measurement in the vacuum degree range of 1×10 -4 Pa to 100 Pa. The output signal strength is as high as the milliampere level, and the sensitivity is increased by 1 - 2 orders of magnitude; (2) This vacuum gauge also has the ability of dynamic adjustment: by adjusting the diaphragm material parameters and geometric dimensions, the measurement range and sensitivity can be flexibly customized to adapt to different application requirements; (3) This vacuum gauge also has the capabilities of miniaturization and system integration. The device size is controlled within the sub-micron range. The MOSFET amplification unit and the capacitance sensing structure adopt a vertical integration layout, which is suitable for CMOS chip-level integration, and has excellent miniaturization characteristics and system compatibility; (4) This vacuum gauge also features low power consumption and high stability: It only requires applying a voltage (V_DS) to the drain for driving, without the need for additional excitation signals or complex peripheral circuits. Its power consumption is significantly lower than that of traditional Pirani vacuum gauges. (5) This vacuum gauge also has the advantages of low cost and potential for mass production: All process steps are compatible with standard CMOS processes, without the need for special materials or complex microfabrication techniques, making it suitable for large-scale mass production and significantly reducing the manufacturing cost. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the capacitive semiconductor micro-vacuum gauge of the present invention; Figure 2 It is a three-dimensional view of the capacitive semiconductor micro-vacuum gauge of the present invention; Figure 3 It is a three-dimensional view of the ring electrode structure of the capacitive semiconductor micro-vacuum gauge of the present invention; Figure 4 It is a three-dimensional view of the array structure of the capacitive semiconductor micro-vacuum gauge of the present invention; Figure 5 It is a schematic diagram of the structural deformation of the micro-vacuum gauge under the action of external air pressure; Figure 6 It is a doping concentration diagram; Figure 7 It is an electron concentration diagram of the micro-vacuum gauge under working conditions; Figure 8 It is a pressure-drain current curve under high-vacuum range air pressure; Figure 9 It is a pressure-drain current curve under medium-vacuum range air pressure; Among them, 1 - signal conversion module, 11 - substrate, 12 - source electrode, 13 - drain electrode, 2 - air pressure sensing module, 21 - dielectric isolation layer, 22 - lower electrode, 23 - sealing structure, 24 - vacuum chamber, 25 - deformable upper electrode. Detailed Embodiments

[0022] The following further illustrates the technical solutions of the present invention in conjunction with embodiments. The test materials used in the embodiments can all be obtained through conventional channels.

[0023] Embodiment 1 The capacitive semiconductor micro-vacuum gauge of the present invention, as Figure 1 and Figure 2As shown in the figure, it is composed of a bottom signal conversion module 1 and a top air pressure sensing module 2. Among them, 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. An air pressure sensing module 2 is provided between the source electrode 12 and the drain electrode 13. The air pressure sensing module 2 includes a dielectric isolation layer 21, a lower electrode 22, a sealing structure 23, and a deformable upper electrode 25 from bottom to top. A vacuum chamber 24 is formed by surrounding the lower electrode 22, the deformable upper electrode 25, and the sealing structure 23 encapsulated on the side walls.

[0024] Among them, the deformable upper electrode 25 and the lower electrode 22 are aluminum films, and the internal 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 material, and the dielectric isolation layer 21 is a silicon dioxide SiO2 insulating layer with a thickness of 20 nm. 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 about 0.5:1.

[0025] The signal conversion module 1 is an enhancement-mode MOSFET; the operating point is set in the saturation region, the drain voltage is 10 V, and a voltage coupling is formed between the dielectric isolation layer 21 and the lower electrode 22.

[0026] Embodiment 2 The capacitive semiconductor micro-vacuum gauge of the present invention is as Figure 3 shown, the deformable upper electrode 25 is a ring electrode structure, the radius of the ring electrode is 0.8 μm, and the area ratio to the substrate is 0.3:1. Its inner diameter is 0.5 μm and the outer diameter is 0.8 μm, and the overall area ratio of the electrode to the silicon-based substrate is 0.3:1.

[0027] The ring electrode structure redistributes the capacitance response weights of the upper electrode region of the diaphragm, increasing the contribution of the deformation in the edge region to the overall capacitance change, which helps to improve the response sensitivity to small pressure difference changes. At the same time, this structure has higher geometric adjustability compared to solid electrodes and can be optimized according to different diaphragm materials and sizes to adapt to various sensing scenarios with different precision and linearity requirements.

[0028] Embodiment 3 The capacitive semiconductor micro-vacuum gauge of the present invention is as Figure 4 shown, the capacitive semiconductor micro-vacuum gauge adopts an array layout structure, and multiple independent vacuum detection units are evenly distributed on the same silicon-based substrate 11, and each unit shares a common drain or signal readout electrode. This design allows multiple vacuum gauges to sample synchronously and build a redundant fault tolerance mechanism, which can maintain the overall measurement stability in the case of sudden changes in atmospheric pressure or local failures; at the same time, the multi-point layout improves the spatial sampling accuracy, achieving a faster air pressure response time and a higher error tolerance.

[0029] Example 4 The capacitive semiconductor microvacuum gauge of the present invention supports multi-dimensional implementation schemes. Device wafer fabrication and physical testing can be carried out using standard CMOS processes, and virtual modeling and performance prediction can also be performed based on multi-physics simulation platforms (such as COMSOL and ANSYS), thus achieving the unity of theoretical analysis and engineering implementation.

[0030] Use COMSOL Multiphysics software to carry out multi-physics coupling simulation analysis to verify the working mechanism and performance of the high-sensitivity capacitive semiconductor microvacuum gauge based on the MOSFET structure proposed by the present invention: Model and study the electrical response, structural deformation of the device in different vacuum environments and their coupling relationship with capacitance change, specifically including the following steps: Step 1. Simulation model construction Select the COMSOL Multiphysics 6.2 software platform, activate the "Semiconductor Module", "Solid Mechanics Module", "Electrostatics Module" and "Moving Mesh Module" to achieve the coupling simulation of the electric field, force field and structural deformation; The simulation structure includes: Bottom layer: Si-based substrate and the main MOSFET structure (source, drain, gate and their contact layers); Top layer: SiO2 insulation layer and metal fixed electrode (lower electrode); deformable aluminum film (upper electrode), vacuum chamber and silicon nitride sidewall sealing layer; The structural dimension parameters are set as follows: the thickness of the silicon oxide layer is 30 nm, the height of the vacuum chamber is 0.1 μm, the drain voltage is 10V, the substrate width is 0.7μm, etc.; The material model includes silicon (Si), silicon dioxide (SiO2), aluminum (Al), silicon nitride (Si3N4) and the relative vacuum layer, and their corresponding thermal, mechanical and electrical properties are assigned to them respectively.

[0031] Step 2. Material parameter setting and multi-physics coupling setting Material selection type The material model includes silicon (Si), silicon dioxide (SiO2), aluminum (Al), silicon nitride (Si3N4) and the relative vacuum layer, and their corresponding electrostatic, mechanical and semiconductor properties are assigned to them respectively; Key physical parameters To adapt to multi-physics coupling analysis, the following key parameters need to be defined in the material respectively: Table 1. Silicon material parameters

[0032] Table 2. Silicon dioxide material parameters

[0033] Table 3, Aluminum Material Parameters

[0034] Table 4, Vacuum Material Parameters

[0035] Table 5, Silicon Nitride Material Parameters

[0036] Coupled Physical Field Settings: Semiconductor Module: Set the NMOS enhancement transistor structure, define the source, drain, and metal contact boundaries, doping concentration and range, and use the trap-assisted recombination mechanism for carrier recombination; Electrostatic Module: Used to simulate the potential distribution and capacitance change between the upper and lower electrodes; Solid Mechanics Module: Define the elastic deformation behavior of the upper electrode and apply different external air pressures to simulate the change of the vacuum environment; Dynamic Mesh Module: Used to handle the geometric nonlinear effects caused by the diaphragm deformation.

[0037] Step 3: Mesh Generation and Dynamic Mesh Optimization To achieve high-precision modeling and efficient solution of the device under multi-physical field coupling conditions, adopt the adaptive mesh generation strategy in COMSOL Multiphysics and introduce the dynamic mesh mechanism to adapt to the geometric deformation of the vacuum chamber area; Semiconductor Active Region (MOSFET Channel, Source / Drain Region): Use medium-density free meshes with an element size of about 10 nm to ensure accurate calculation of the electric field strength, carrier concentration, and current density, and meet the electrical performance simulation requirements; Gate Dielectric and Metal Layer Region: There is a significant potential gradient between the dielectric layer and the electrode, and local refinement is required. The mesh size is about 3 - 5 nm to ensure the resolution ability of capacitance changes under different working conditions; Peripheral Silicon Substrate and Mechanical Support Structure: Since the stress distribution in this region is relatively uniform, the mesh size can be relaxed to 20 - 30 nm to reduce the overall model scale and improve the simulation efficiency; Dynamic Mesh Region (Vacuum Chamber and Its Upper and Lower Boundaries): This region corresponds to the elastic deformation region of the upper electrode under the action of air pressure. To capture its nonlinear displacement and capacitance change, use the dynamic mesh module to automatically track the boundary position. The initial mesh uses structured or free mesh arrangement, and the element size is controlled between 1 - 5 nm. During the simulation process, the mesh is reconstructed in real time as the upper electrode deforms, maintaining a high degree of fitting to the boundary curvature change, effectively avoiding simulation divergence or accuracy degradation; The total number of elements in the final simulation model grid is controlled between approximately 1.5 million and 2 million elements, taking into account the simulation accuracy of the key response areas of the device and the optimization of overall computing resources, ensuring good coupling consistency among the results of the deformation, capacitance, and current response fields.

[0038] Step 4: Parameter Scanning and Boundary Condition Setting To investigate the electrical response of the device under different vacuum degrees, the external air pressure P0 is scanned parametrically, with the coverage range being: Study 1: P0 ranges from 0 Pa to 100 Pa, with a step of 0.1; Study 2: In the low-pressure region, P0 is finely scanned from 0 Pa to 1e-3 Pa, with a step of 1e-5; In the simulation, the free boundary of the diaphragm is considered, the bottom electrode is grounded, the upper electrode is set as the variable terminal, and the gate voltage of the MOSFET and the potential of the lower electrode are capacitively coupled.

[0039] Step 5: Simulation Result and Performance Analysis Structural Deformation Response: As the air pressure increases, the upper electrode diaphragm undergoes visible downward elastic deformation, with the maximum displacement at the center, and the displacement amount shows non-linear growth with the pressure difference; Lower Plate Voltage Change: The value of the lower plate voltage increases significantly with the increase in the sinking degree of the diaphragm, forming a fitting function relationship with the pressure; Current Response Characteristics: Under the condition of keeping the source-drain (Vds = 10V) voltage constant, the drain current Id changes significantly with the change in the gate voltage. The simulation shows that this structure has an output gain of >100 times, and the current signal intensity reaches the milliampere level, which is suitable for direct post-stage readout and processing; Pressure Response Range: The simulation shows that the device can achieve high-sensitivity continuous detection in the range of 1×10 -4 Pa to 100 Pa, with a significant current response, facilitating subsequent electronic acquisition and processing.

[0040] Final Effect: Measurement Range: It can achieve high-precision measurement in the vacuum degree range of 1×10 -4 Pa to 100 Pa; Signal Intensity and Sensitivity: The output signal intensity is as high as the milliampere level, and the sensitivity is increased by 1 - 2 orders of magnitude; Dynamic Adjustment Ability: By adjusting the diaphragm material parameters and geometric dimensions, the measurement range and sensitivity can be flexibly customized to adapt to different application requirements; Miniaturization and System Integration Ability: The device size is controlled within the sub-micron range. The MOSFET amplification unit and the capacitive sensing structure adopt a vertical integrated layout, which is suitable for CMOS chip-level integration, with excellent miniaturization characteristics and system compatibility.

[0041] As Figure 5 shown, it is a schematic diagram of the structural deformation of the micro-vacuum gauge under the action of external air pressure. Among them, it can be observed that obvious elastic deformation occurs in the deformable upper electrode 25 under the action of external air pressure. The displacement of the central region sinking downward is the largest, and the deformation amplitude decreases in a gradient distribution from the center to the edge. With the deformation of the upper electrode, the distance between it and the fixed lower electrode 22 changes, resulting in a corresponding change in the capacitance value of the capacitor formed by the two. The rigid support of the sealing structure 23 makes the deformation mainly concentrated in the central region of the upper electrode, while the deformation of the edge of the deformable upper electrode is effectively constrained.

[0042] As Figure 6 shown, it is a doping concentration diagram, showing the key doping distribution characteristics of the semiconductor substrate in the micro-vacuum gauge. Different colors are used in the figure to mark the P-type and N-type doping regions: the blue region represents the acceptor doping (P-type) with a concentration of 1×10 17 cm⁻³, which is mainly distributed in the substrate and the channel region (i.e., the position below the lower plate); the red region represents the donor doping (N-type) with a concentration of 1×10 20 cm⁻³, which is concentrated in the regions below the source and drain. This combination of high-concentration N+ doping (source-drain region) and lightly doped P-type channel forms a typical enhancement-type NMOS structure. The steep concentration gradient in the doping transition region reflects the process control of ion implantation.

[0043] As Figure 7 shown, it is an electron concentration diagram of the micro-vacuum gauge under working conditions, showing the conduction characteristics of the channel region of the micro-vacuum gauge in the working state. It can be observed in the figure that when a 10V drain voltage and an appropriate lower electrode voltage are applied, an obvious electron conduction channel is formed in the channel region, showing a bright strip-shaped structure.

[0044] As Figure 8 and Figure 9 shown, it is a gas pressure-drain current curve, showing the electrical response characteristics of the device under different vacuum degrees. It can be observed in the figure that when the gas pressure reaches 0.00005 Pa (high vacuum range), a detectable change in the drain current begins, indicating that the device has entered the effective detection range. As the gas pressure continues to increase, the current response shows a stable upward trend. In the medium vacuum range (1×10 -1 ~1×10 2 Pa), the change is more obvious, and a current with a change in the milliampere level is output. Thus, under the condition that the device operates in the saturation region, the drive drain current can be increased by an order of magnitude, realizing the "signal conversion-amplification integration" response path from picofarad-level capacitance change to milliampere-level current output.

[0045] 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, miniaturization, and low power consumption of vacuum measurement are achieved. This design makes full use of the compatibility of standard CMOS processes, vertically integrating the gas pressure sensing module and the signal processing unit, which not only simplifies the manufacturing process, 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 the sensitivity, having important practical value and broad commercial prospects, and 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 a gas pressure sensing module (2) at the top layer. Among them, 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. A gas pressure sensing module (2) is arranged between the source electrode (12) and the drain electrode (13). The gas pressure sensing module (2) includes a dielectric isolation layer (21), a lower electrode (22), a sealing structure (23), and a deformable upper electrode (25) from bottom to top. A vacuum chamber (24) is formed by surrounding the lower electrode (22), the deformable upper electrode (25), and the sealing structure (23) encapsulated on the side walls.

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, graphene conductive film or ceramic composite film with a metallized surface layer.

3. The capacitive semiconductor micro-vacuum gauge according to claim 1, characterized in that, The internal height of the vacuum chamber (24) is 0.1 to 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 to 50 nm, and the area is 1.28 to 10 μm 2 , and the shape is a rectangular or annular 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, characterized in that, The substrate (11) is a silicon-based substrate.

9. The capacitive semiconductor micro-vacuum gauge according to claim 1, characterized in that, The capacitive semiconductor micro-vacuum gauges are arranged on the substrate (11) in an array.

10. A method for detecting the vacuum degree of the capacitive semiconductor micro-vacuum gauge according to claim 1, characterized in that, It includes the following steps: Step 1: Place the capacitive semiconductor micro-vacuum gauge in the vacuum environment to be measured, and a pressure difference is formed between the external air pressure and the internal reference air pressure in the vacuum chamber. Step 2: This pressure difference causes the deformable upper electrode to undergo elastic deformation. 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 and the lower electrode form voltage coupling, and the capacitance change is coupled to the lower electrode through the dielectric isolation layer, changing the voltage of the lower electrode. Step 5: The drain voltage is set to 3.3 - 10 V. Under the fixed drain voltage V_DS, the change in the gate voltage generates a significant change in the drain current through the transconductance gain g_m of the MOSFET. Step 6: By detecting the magnitude of the drain current, the external vacuum degree can be measured, realizing high-sensitivity measurement.

Images