High-precision capacitance thin-film vacuum gauge
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN SANYAO ELECTRONICS CO LTD
- Filing Date
- 2026-04-09
- Publication Date
- 2026-06-09
Smart Images
Figure CN122171093A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sensor technology, specifically relating to a high-precision capacitive thin-film vacuum gauge, which is particularly suitable for the precise measurement and control of vacuum environments containing corrosive gases in fields such as semiconductor manufacturing, vacuum systems, and uranium enrichment. Background Technology
[0002] With the advancement of science and technology, the requirements for vacuum environments in high-tech fields such as semiconductor manufacturing and uranium enrichment are becoming increasingly stringent. Many process steps must be carried out under precisely controlled high vacuum conditions. Metal capacitor thin-film vacuum gauges are among the most widely used vacuum gauges. Their working principle utilizes the deformation of an elastic sensing diaphragm under the pressure difference between a reference vacuum and the pressure chamber being measured. This deformation causes a change in the spacing between capacitor plates, resulting in a change in capacitance. The pressure value is calculated by measuring the change in capacitance.
[0003] However, existing capacitive thin-film vacuum gauges have at least the following drawbacks:
[0004] 1. Poor corrosion resistance and short lifespan: In processes such as semiconductor etching and uranium enrichment, the measured medium gas often contains fluoride ions (F⁻), chloride ions (Cl⁻), and other acidic or alkaline corrosive substances. Traditional vacuum gauges typically use diaphragm materials in contact with the medium, such as 316L stainless steel, Inconel alloy, ceramics, or silicon. These materials have limited resistance to the aforementioned corrosive ions. Long-term contact leads to diaphragm corrosion, resulting in thinning, surface pitting, and other problems. This causes a rapid decline in vacuum gauge accuracy and a significantly shortened lifespan.
[0005] 2. Insufficient Accuracy and Stability: When measuring high vacuum (i.e., small pressure ranges, such as 0.1 Torr or 1 Torr), the sensor's elastic diaphragm must be made extremely thin to obtain sufficient sensitivity. This thin film is extremely sensitive to external stress. Since the diaphragm and housing are usually rigidly connected, external stresses such as stress generated during installation or vibrations during equipment operation are easily transmitted to the diaphragm, causing fluctuations and drift in the measurement signal. This makes it difficult to improve the stability and measurement accuracy of the vacuum gauge to above 0.1%FS. Summary of the Invention
[0006] The present invention aims to at least partially solve the aforementioned technical problems. Therefore, the objective of the present invention is to provide a high-precision capacitive thin-film vacuum gauge.
[0007] The technical solution adopted in this invention is as follows:
[0008] A high-precision capacitive thin-film vacuum gauge includes: a housing, a fixed capacitor plate disposed inside the housing, and an upper moving capacitor plate and a lower moving capacitor plate disposed on the upper and lower sides of the fixed capacitor plate, respectively. The upper and lower moving capacitor plates are both elastic diaphragms that deform under pressure. The upper and lower moving capacitor plates are made of amorphous alloy material.
[0009] By using amorphous alloy materials to make the dynamic capacitance plate (elastic diaphragm), its unique atomic structure (long-range disorder, no grain boundaries) and excellent chemical stability are utilized to fundamentally improve the vacuum gauge's resistance to corrosive media such as fluoride ions and chloride ions, prevent performance degradation caused by corrosion, thereby significantly extending the product's service life and ensuring long-term measurement accuracy.
[0010] Preferably, the amorphous alloy material is a zirconium-based amorphous alloy with a material composition of Zr. a Cu b Ni c Al d Ti e R f The atomic mass percentage (a) of Zr is 46-57%, that of Cu is 13-20.5%, that of Ni is 9.6-18.3%, that of Al is 8.5-11.7%, that of Ti is 3.7-8.5%, and R is one or more of Cr, Mo, and B, with an atomic mass percentage (f) of 0.08-0.19. Adding elements such as Cr, Mo, and B can further improve the stability of the passivation film and enhance its corrosion resistance.
[0011] Preferably, the amorphous alloy material can also be a nickel-based amorphous alloy or a cobalt-based amorphous alloy to meet the needs of different application scenarios.
[0012] Preferably, stress isolation grooves are provided at both ends where the fixed capacitor plate connects to the housing. The structure of these stress isolation grooves can effectively buffer and isolate the stress transmitted from the housing to the fixed capacitor plate during installation or external vibration, preventing stress from affecting the flatness of the capacitor plate, thereby greatly improving the measurement stability and accuracy of the product, especially small-range products.
[0013] Preferably, the fixed capacitor plate has an upper capacitor film on its upper surface and a lower capacitor film on its lower surface; the upper capacitor film and the upper movable capacitor plate constitute a first capacitor; the lower capacitor film and the lower movable capacitor plate constitute a second capacitor; the first capacitor and the second capacitor are connected in parallel, and the total capacitance change of the vacuum gauge is the sum of the capacitance changes of the first capacitor and the second capacitor. This parallel dual-capacitor structure theoretically doubles the total capacitance change under the same pressure, significantly improving the product's sensitivity, thereby enhancing the signal-to-noise ratio and measurement accuracy, which is particularly significant for small-range measurements.
[0014] Preferably, the thickness of the upper and lower moving capacitor plates is between 0.03 mm and 5.5 mm. Selecting an amorphous alloy diaphragm of appropriate thickness according to the requirements of different measurement ranges ensures both sufficient strength and excellent sensitivity.
[0015] Preferably, the present invention further includes a conditioning circuit board electrically connected to the upper and lower moving capacitor plates and the fixed capacitor plate, the conditioning circuit board including a capacitance detection circuit, a main control circuit and a temperature control circuit.
[0016] Preferably, the main control circuit incorporates a fuzzy control algorithm for piecewise fitting data, used for nonlinear compensation and temperature compensation of the detection signal. This algorithm can efficiently handle the nonlinearity and temperature drift problems of the sensor, achieving high-precision measurement across the entire measurement range.
[0017] Preferably, the present invention further includes a pressure chamber and a pressure-feeding tube leading to the pressure chamber; a heating element is provided at the upper part of the pressure-feeding tube, and the heating element is controlled by the temperature control circuit.
[0018] Preferably, the temperature control circuit controls the heating element to heat the gas entering the pressure chamber and maintain a constant temperature within the pressure chamber. This prevents certain low-temperature media gases from condensing and clogging the pipeline or adhering to the diaphragm when entering the measurement chamber. Simultaneously, the constant temperature environment helps eliminate the influence of temperature drift on the measurement results, further improving the stability and accuracy of the measurement.
[0019] The beneficial effects of this invention are as follows:
[0020] This invention uses an amorphous alloy as the material for the dynamic capacitor plate. Its grain-bound structure and stable passivation film effectively resist corrosion from highly corrosive media such as fluorine and chloride ions. It exhibits no pitting or crevice corrosion in Cl⁻ / F⁻ environments, extending product lifespan by 3-6 times. The amorphous alloy has a lower Young's modulus and higher strength than traditional metal materials, allowing for thinner and more sensitive diaphragms, improving sensitivity by more than 2 times. Combined with a parallel dual-capacitor design, the sensitivity is further doubled, enabling the overall product accuracy, especially for small-range products, to consistently exceed 0.1%FS.
[0021] The stress isolation groove designed on the fixed capacitor plate in this invention effectively isolates external stress from interfering with the core sensing components, greatly improving the stability and repeatability of the product. The annual drift rate can be controlled within ≤±0.1% FS / year.
[0022] This invention solves the application pain points of traditional vacuum gauges in harsh working conditions such as semiconductor etching, photovoltaic coating, uranium enrichment, and chemical industry, expands the application scope of high-precision capacitive vacuum gauges, and can directly replace traditional vacuum gauges. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the structure of a high-precision capacitive thin-film vacuum gauge according to the present invention.
[0024] In the diagram: 1-Metal casing, 2-Fixed capacitor plate, 3-Upper moving capacitor plate, 4-Lower moving capacitor plate, 5-Upper vacuum chamber, 6-Lower vacuum chamber, 7-Pressure chamber, 8-Conditioning circuit board, 9-Heating pack, 10-Pressure tube, 21-Stress isolation groove, 22-Upper capacitor film, 23-Lower capacitor film. Detailed Implementation
[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention. The components of the embodiments of the invention described and illustrated herein can generally be arranged and designed in various different configurations.
[0026] In this invention, unless otherwise explicitly specified and limited, the terms "installation", "connection", "linking", "fixing", etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components.
[0027] like Figure 1 As shown, this embodiment provides a high-precision capacitive thin-film vacuum gauge, which mainly includes a metal housing 1, and a sensing core component and a conditioning circuit board 8 are encapsulated inside the housing 1.
[0028] The core sensing component includes a centrally located fixed capacitor plate 2, an upper moving capacitor plate 3 located above the fixed capacitor plate 2, and a lower moving capacitor plate 4 located below the fixed capacitor plate 2. The fixed capacitor plate 2, upper moving capacitor plate 3, and lower moving capacitor plate 4 together define three spaces: an upper vacuum cavity 5 located between the fixed capacitor plate 2 and the upper moving capacitor plate 3, a lower vacuum cavity 6 located between the fixed capacitor plate 2 and the lower moving capacitor plate 4, and a pressure cavity 7 located around the upper moving capacitor plate 3 and the lower moving capacitor plate 4. The upper vacuum cavity 5 and the lower vacuum cavity 6 are evacuated to a high vacuum (e.g., better than 1×10⁻⁶). -4 Pa), as a reference standard for measurement.
[0029] Both the upper moving capacitor plate 3 and the lower moving capacitor plate 4 are made of amorphous alloy material. In this embodiment, a zirconium-based amorphous alloy is selected, specifically with a Zr content of 100%. a Cu b Ni c Al d Ti e R f The atomic mass percentage range of each element is: a=46-57, b=13-20.5, c=9.6-18.3, d=8.5-11.7, e=3.7-8.5, f=0.08-0.19, where R is one or more of Cr, Mo, and B.
[0030] Amorphous alloys have significant advantages over traditional crystalline metal materials (such as 316L stainless steel):
[0031] 1. Structural advantages: Amorphous alloys have long-range atomic disorder and no defects such as grain boundaries or dislocations. This prevents corrosive ions (such as Cl⁻, F⁻) from penetrating along grain boundaries, fundamentally eliminating the pathways for pitting corrosion and stress corrosion cracking.
[0032] 2. Chemical Advantages: Amorphous alloys can rapidly form a dense, uniform, and stable passivation film on their surface, exhibiting corrosion resistance far superior to crystalline alloys such as 316L and Inconel. Experimental data (as shown in Table 1) indicate that in strongly acidic environments, the corrosion rate of zirconium-based amorphous alloys is 1-2 orders of magnitude lower than that of 316L stainless steel.
[0033] Table 1. Comparison of properties between zirconium-based amorphous alloys and 316L stainless steel.
[0034] Serial Number Performance indicators Zirconium-based amorphous alloys 316L stainless steel Amorphous alloys are several times higher 1 Compressive breaking strength / GPa 1.73 0.6 2.88 times 2 Elastic modulus / GPa 82 192 0.43% 3 <![CDATA[Corrosion rate 1mol / L HNO3 / g / (m²・h)]]> 0.81 89.0 109.88 times 4 <![CDATA[Corrosion rate in 0.5 mol / L H2SO4 / g / (m 2 ·h)]]> 0.48 64.0 133.33 times 5 <![CDATA[Corrosion rate 0.5mol / L HF / g / (m 2 ·h)]]> 0.55 44.8 81.5 times
[0035] 3. Mechanical Advantages: The compressive fracture strength (1.73 GPa) of zirconium-based amorphous alloy is approximately 2.88 times that of 316L stainless steel (0.6 GPa), while its elastic modulus (82 GPa) is only 43% of that of 316L (192 GPa). The high strength allows for thinner diaphragms within the same measurement range, while the low elastic modulus means greater deformation under the same pressure. Since sensitivity is inversely proportional to the elastic modulus, theoretically, sensitivity can be increased by approximately 2.33 times.
[0036] The dynamic capacitance plate (diaphragm) can be fabricated using a bulk cutting and grinding method. Its thickness depends on the range of the vacuum gauge, typically ranging from 0.03 mm to 5.5 mm. For example, for a small range of 1 Torr, a thin sheet of about 0.03 mm can be selected to obtain high sensitivity.
[0037] like Figure 1 As shown, stress isolation grooves 21 are machined at both ends of the fixed capacitor plate 2, i.e., in the areas connected to the metal housing 1. This is a structural optimization design. When the vacuum gauge is installed on the vacuum system via flanges or other means, the installation force or pipe vibration will cause slight deformation of the housing 1. Without the stress isolation grooves 21, this stress would be directly transmitted to the fixed capacitor plate 2, causing it to warp, thereby changing the initial spacing of the capacitors and causing zero-point drift and measurement errors. The presence of the stress isolation grooves 21 is equivalent to a mechanical buffer structure, which can greatly absorb and reduce the stress transmitted to the core area of the capacitor plate, ensuring the flatness and stability of the capacitor plate. This is especially important when measuring pressures in extremely small ranges such as 0.1 Torr, 1 Torr, and 10 Torr.
[0038] The fixed capacitor plate 2 has capacitor films on both its front and back sides, namely an upper capacitor film 22 and a lower capacitor film 23. The upper capacitor film 22 is opposite to the upper movable capacitor plate 3, forming the first capacitor C1. The lower capacitor film 23 is opposite to the lower movable capacitor plate 4, forming the second capacitor C2. These two capacitors are connected in parallel in the circuit.
[0039] When the gas being measured enters the pressure chamber 7 through the pressure tap 10, the pressure P inside the pressure chamber 7... meas The force acts on the upper surface of the upper moving capacitor plate 3 and the lower surface of the lower moving capacitor plate 4. Since the upper vacuum chamber 5 and the lower vacuum chamber 6 are reference vacuums (pressure P... ref ≈0), pressure difference (P) meas -P ref This causes the upper moving capacitor plate 3 to bend downwards and the lower moving capacitor plate 4 to bend upwards, both moving towards the fixed capacitor plate 2. This results in a decrease in the spacing of the first capacitor C1 and an increase in capacitance value of ΔC1; at the same time, the spacing of the second capacitor C2 also decreases, and the capacitance value increases by ΔC2.
[0040] The total capacitance change detected by the conditioning circuit board 8 is ΔC = ΔC1 + ΔC2. Compared to a single-capacitor structure with only one moving capacitor plate, the dual-capacitor structure of this invention theoretically doubles the total capacitance change under the same pressure. Experimental data (as shown in Table 2) confirms that the product using the dual-capacitor form (D2011) has nearly double the sensitivity (approximately 2.77 mV / V) compared to the single-capacitor form product (S3022, approximately 1.43 mV / V), and the overall accuracy has also improved from 0.126%FS to within 0.1%FS.
[0041] Table 2 Comparison of main parameters between dual-capacitor plate and single-capacitor plate products
[0042]
[0043] The gas being measured enters through the pressure tap 10. In some applications, the medium may be at a low temperature and prone to condensation. Therefore, a heating element 9 is installed on the upper part of the pressure tap 10. The temperature control circuit within the conditioning circuit board 8 controls the operation of the heating element 9 to preheat the incoming gas, ensuring it enters the pressure chamber 7 in a gaseous state, preventing condensation blockage or affecting diaphragm deformation. Simultaneously, the temperature control circuit also maintains the entire sensing core component at a constant operating temperature (e.g., 45°C), eliminating temperature drift caused by changes in ambient temperature.
[0044] The gas entering pressure chamber 7 deforms the upper moving capacitor plate 3 and the lower moving capacitor plate 4, generating a capacitance change ΔC. A capacitance detection circuit on the conditioning circuit board 8 (e.g., employing a high-frequency oscillation design with a detection accuracy of 0.001pF) converts this minute capacitance change into an electrical signal. This signal is then sent to the main control circuit (which can be a microcontroller MCU). The main control circuit runs an optimized fuzzy control algorithm. This algorithm, based on pre-calibrated piecewise fitting data and incorporating boundary smoothing factors, performs nonlinear correction and temperature compensation on the signal, ultimately outputting a standardized signal (such as a voltage or current signal) that is linearly related to the pressure value.
[0045] As shown in Table 3, a comparative experiment was conducted between a vacuum gauge using the amorphous material of this invention and a vacuum gauge using conventional materials. After passing HF gas containing fluorine and chloride ions and maintaining it for 300 hours, the zero-point change of the conventional material vacuum gauge reached 3.29%-5.33%, and the accuracy change was as high as 14.78%-17.85%, indicating a severe deterioration in performance. In contrast, the vacuum gauge using amorphous materials exhibited a zero-point change of only 1.79%-1.89% and an accuracy change of only 2.04%-2.11%, demonstrating extremely strong corrosion resistance and stability.
[0046] Table 3 Comparison of corrosion resistance of vacuum gauges with different capacitor plate materials
[0047]
[0048] This invention addresses the corrosion and stability issues of existing capacitive vacuum gauges by employing an amorphous alloy dynamic capacitor plate, setting stress isolation grooves, and using a dual-capacitor parallel structure, thereby significantly improving the product's accuracy, lifespan, and applicability.
[0049] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.
Claims
1. A high-precision capacitive thin-film vacuum gauge, characterized in that, include: The housing (1), the fixed capacitor plate (2) disposed inside the housing (1), and the upper moving capacitor plate (3) and the lower moving capacitor plate (4) disposed on the upper and lower sides of the fixed capacitor plate (2), respectively. The upper moving capacitor plate (3) and the lower moving capacitor plate (4) are both elastic diaphragms that deform under pressure. The upper moving capacitor plate (3) and the lower moving capacitor plate (4) are made of amorphous alloy material.
2. The high-precision capacitive thin-film vacuum gauge according to claim 1, characterized in that, The amorphous alloy material is a zirconium-based amorphous alloy, and its material composition is Zr. a Cu b Ni c Al d Ti e R f In this composition, Zr has an atomic mass percentage (a) of 46-57, Cu has an atomic mass percentage (b) of 13-20.5, Ni has an atomic mass percentage (c) of 9.6-18.3, Al has an atomic mass percentage (d) of 8.5-11.7, Ti has an atomic mass percentage (e) of 3.7-8.5, and R is one or more of Cr, Mo, and B, with an atomic mass percentage (f) of 0.08-0.
19.
3. The high-precision capacitive thin-film vacuum gauge according to claim 1, characterized in that, The amorphous alloy material is a nickel-based amorphous alloy or a cobalt-based amorphous alloy.
4. The high-precision capacitive thin-film vacuum gauge according to claim 1, characterized in that, The fixed capacitor plate (2) is provided with stress isolation grooves (21) at both ends where it is connected to the housing (1).
5. The high-precision capacitive thin-film vacuum gauge according to claim 1, characterized in that: The upper surface of the fixed capacitor plate (2) is provided with an upper capacitor film (22), and the lower surface is provided with a lower capacitor film (23). The upper capacitor film (22) and the upper moving capacitor plate (3) constitute the first capacitor; The lower capacitor film (23) and the lower moving capacitor plate (4) constitute a second capacitor; The first capacitor and the second capacitor are connected in parallel, and the total capacitance change of the vacuum gauge is the sum of the changes in the first capacitor and the second capacitor.
6. The high-precision capacitive thin-film vacuum gauge according to claim 1, characterized in that, The thickness of the upper moving capacitor plate (3) and the lower moving capacitor plate (4) is 0.03 mm to 5.5 mm.
7. The high-precision capacitive thin-film vacuum gauge according to claim 1, characterized in that, It also includes a conditioning circuit board (8) electrically connected to the upper moving capacitor plate (3), the lower moving capacitor plate (4) and the fixed capacitor plate (2), the conditioning circuit board (8) including a capacitor detection circuit, a main control circuit and a temperature control circuit.
8. The high-precision capacitive thin-film vacuum gauge according to claim 7, characterized in that, The main control circuit has a built-in fuzzy control algorithm for segmented fitting data, which is used to perform nonlinear compensation and temperature compensation on the detection signal.
9. The high-precision capacitive thin-film vacuum gauge according to claim 7, characterized in that, It also includes a pressure chamber (7) and a pressure tube (10) leading to the pressure chamber (7); a heating element (9) is provided on the upper part of the pressure tube (10), and the heating element (9) is controlled by the temperature control circuit.
10. The high-precision capacitive thin-film vacuum gauge according to claim 9, characterized in that, The temperature control circuit controls the heating element (9) to heat the gas entering the pressure chamber (7) and maintain a constant temperature inside the pressure chamber (7).