Multi-sealing-cavity MEMS capacitor film vacuum gauge

Abstract

The invention relates to the technical field of vacuum measurement, in particular to a multi-sealing-cavity MEMS capacitor thin film vacuum gauge, and is characterized in that a silicon substrate is arranged above substrate glass and is bonded with the substrate glass; a pressure sensing film is obtained in the middle of the silicon substrate in a photoetching and dry etching mode; a fixed metal electrode is obtained in the middle of the substrate glass in a photoetching and sputter coating mode; a capacitance gap is formed between the fixed metal electrode and the pressure sensing film; photoetching and corroding the silicon substrate, forming a working sealing cavity above the pressure sensing film, and respectively forming a first cavity and a second cavity above two sides of the pressure sensing film; getter blocks are arranged in the first chamber and the second chamber; and the sealing glass is arranged above the silicon substrate. On the premise that the size of the vacuum gauge is not obviously increased, the multiple chambers are arranged to form the sealing cavity, the air suction capacity is improved, high vacuum obtaining and long-term maintaining performance of the sealing cavity of the vacuum gauge are ensured, and the long-term stability of the vacuum gauge is greatly improved.

Description

Technical Field

[0001] The present application relates to the field of vacuum measurement technology, and in particular to a multi-sealed cavity MEMS capacitive thin film vacuum gauge. Background Art

[0002] Capacitance film vacuum gauge has the characteristics of high accuracy, good linearity, good repeatability and good long-term stability. It can measure the total pressure of gas or vapor, and the measurement result is independent of the gas composition and type. Capacitance film vacuum gauge based on micro-electromechanical system (MEMS) technology has the advantages of light weight (gram level) and small size (less than 1cm 3 ) and low power consumption (milliwatt level), making it a hot topic of research at home and abroad.

[0003] Unlike traditional mechanical capacitive thin film vacuum gauges made using metal welding, machining and other technologies, MEMS capacitive thin film vacuum gauges are made using semiconductor processes such as photolithography, bonding, and etching. Their pressure-sensitive films are mostly made of single-crystal silicon materials, and the reference cavity is mostly formed by silicon and glass bonding and sealing. While miniaturization, it solves the problems of metal diaphragm creep and zero drift of traditional capacitive thin film vacuum gauges. In addition, compared with Pirani, resonant, and piezoelectric vacuum gauges based on MEMS technology, MEMS capacitive thin film vacuum gauges have irreplaceable advantages in terms of measurement range, power consumption, and the influence of gas types on measurement results.

[0004] However, since the volume of the sealed reference cavity in the current MEMS capacitive thin film vacuum gauge is in the order of cubic millimeters, it is difficult to obtain and maintain high vacuum in the sealed reference cavity, which limits the measurement lower limit and long-term stability of the MEMS capacitive thin film vacuum gauge. Summary of the invention

[0005] The present application provides a multi-sealed cavity MEMS capacitance thin film vacuum gauge, which can achieve 1Pa~8.4×10 4 The measurement of absolute vacuum in the Pa range improves the long-term stability of the vacuum gauge.

[0006] In order to achieve the above-mentioned purpose, the present application provides a multi-sealed cavity MEMS capacitive thin film vacuum gauge, including base glass, silicon substrate, sealing glass, pressure-sensitive film, fixed metal electrode and getter block, wherein: the silicon substrate is arranged above the base glass and bonded to the base glass; the pressure-sensitive film is obtained in the middle of the silicon substrate by photolithography and dry etching; the fixed metal electrode is obtained in the middle of the base glass by photolithography and sputtering coating; a capacitor gap is formed between the fixed metal electrode and the pressure-sensitive film; the silicon substrate is photolithographically and corroded to form a working sealed cavity above the pressure-sensitive film, and a first chamber and a second chamber are respectively formed above both sides of the pressure-sensitive film; the working sealed cavity is connected to the first chamber and the second chamber respectively through a connecting channel; getter blocks are arranged inside the first chamber and the second chamber; the sealing glass is arranged above the silicon substrate and bonded to the silicon substrate.

[0007] Furthermore, the fixed metal electrodes include sensitive capacitor electrodes and lead-out electrodes, both of which are composed of chromium film and gold film, and are plated on the surface of the substrate glass in the order of chromium first and gold later by magnetron sputtering method.

[0008] Furthermore, a first electrode lead-out port and a second electrode lead-out port are provided on the top of the silicon substrate. The first electrode lead-out port is used for leading out the sensitive capacitor electrode, and the second electrode lead-out port is used for leading out the pressure-sensitive film electrode.

[0009] Furthermore, the material of the pressure-sensitive film is boron-doped single-crystal silicon, and the whole film is a square film with four rounded corners.

[0010] Furthermore, the silicon substrate is made of an SOI wafer, the pressure-sensitive film is located in a thin silicon layer, and the working sealing cavity is located in a thick silicon layer.

[0011] Furthermore, the getter block is composed of a plurality of rectangular silicon wafers with Ti-Zr-V alloy non-evaporable getter films coated on the surfaces.

[0012] Furthermore, the getter block is activated during the anodic bonding process between the sealing glass and the silicon substrate.

[0013] Furthermore, the working sealed cavity, the first cavity and the second cavity are interconnected to form a sealed cavity, and the vacuum degree is less than 10 -2 Pa.

[0014] Furthermore, the measurement range of vacuum pressure is 1Pa~8.4×10 4 Pa.

[0015] The multi-sealed cavity MEMS capacitive thin film vacuum gauge provided in the present application has the following beneficial effects:

[0016] The present application arranges multiple chambers to form a sealed cavity without significantly increasing the size of the vacuum gauge, thereby solving the problem of insufficient placement of getter due to size limitation of the MEMS vacuum gauge, increasing the placement amount of getter in the vacuum gauge, improving the air absorption capacity, ensuring the high vacuum acquisition and long-term maintenance performance of the sealed cavity of the vacuum gauge, and greatly improving the long-term stability of the vacuum gauge; at the same time, it avoids the mutual interference problem caused by the placement of the getter and the pressure-sensitive film working in the same sealed cavity, eliminates external factors that affect the normal operation of the pressure-sensitive film, eliminates the risk of causing the pressure-sensitive film to fail, and improves the reliability and accuracy of the vacuum gauge. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0018] Figure 1 is a schematic diagram of a multi-sealed cavity MEMS capacitive thin film vacuum gauge provided according to an embodiment of the present application;

[0019] Figure 2 is a cross-sectional view of the internal structure of a multi-sealed cavity MEMS capacitive thin film vacuum gauge provided according to an embodiment of the present application;

[0020] Figure 3 The multi-sealed chamber MEMS capacitor thin film vacuum gauge provided in the embodiment of the present application is 1Pa~8.4×10 4 Test data graph in Pa range;

[0021] Figure 4 This is a test data chart of the long-term stability of the multi-sealed cavity MEMS capacitive thin film vacuum gauge provided in the embodiment of the present application within the range of 1Pa to 100Pa;

[0022] In the figure: 1-base glass, 2-silicon substrate, 3-sealing glass, 4-pressure-sensitive film, 5-sensitive capacitor electrode, 6-getter block, 7-capacitor gap, 8-working sealed cavity, 9-first cavity, 10-second cavity, 11-lead-out electrode, 12-first electrode lead-out port, 13-second electrode lead-out port, 14-connecting channel. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0026] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0027] In addition, the term "plurality" shall mean two or more.

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] like Figure 1-2As shown, the present application provides a multi-sealed cavity MEMS capacitive thin film vacuum gauge, including a substrate glass 1, a silicon substrate 2, a sealing glass 3, a pressure-sensitive film 4, a fixed metal electrode and a getter block 6, wherein: the silicon substrate 2 is arranged above the substrate glass 1 and bonded to the substrate glass 1; the pressure-sensitive film 4 is obtained in the middle of the silicon substrate 2 by photolithography and dry etching; the fixed metal electrode is obtained in the middle of the substrate glass 1 by photolithography and sputtering coating; a capacitor gap 7 is formed between the fixed metal electrode and the pressure-sensitive film 4; the silicon substrate 2 is photolithographically and corroded to form a working sealed cavity 8 above the pressure-sensitive film 4, and a first cavity 9 and a second cavity 10 are respectively formed above both sides of the pressure-sensitive film 4; the working sealed cavity 8 is connected to the first cavity 9 and the second cavity 10 respectively through a connecting channel 14; the first cavity 9 and the second cavity 10 are both provided with a getter block 6; the sealing glass 3 is arranged above the silicon substrate 2 and bonded to the silicon substrate 2.

[0030] Specifically, the multi-sealed cavity MEMS capacitive thin film vacuum gauge provided in the embodiment of the present application is made of MEMS technology and can be used to measure the total pressure of medium and low vacuum gases. It has good linearity, good output repeatability, and high measurement accuracy. At the same time, a multi-sealed cavity structure is set up to increase the number of placed getters, thereby increasing the air intake capacity of the getters, ensuring the acquisition and long-term maintenance of high vacuum in the sealed cavity, and can be applied to deep space exploration, wind tunnel experiments, biomedicine and other fields that have miniaturization requirements for vacuum measuring instruments.

[0031] More specifically, in the embodiment of the present application, the vacuum gauge is a glass-silicon-glass structure as a whole, a fixed metal electrode is made on the substrate glass 1, a pressure-sensitive film 4 and a sealed cavity are made on the silicon substrate 2, and the sealed cavity is composed of a working sealed cavity 8 of a pressure-sensitive film and two chambers for placing getter blocks 6, and finally the sealing glass 3 and the silicon substrate 2 are bonded by high vacuum anode to complete the high vacuum sealing. Among them, the fixed metal electrode and the pressure-sensitive film 4 form a sensitive capacitor, which converts the vacuum pressure change into a capacitance signal change during the measurement process, thereby realizing the measurement of the vacuum pressure.

[0032] Further, the fixed metal electrode includes a sensitive capacitor electrode 5 and an extraction electrode 11, both of which are composed of a chromium film and a gold film, and are plated on the surface of the base glass 1 by a magnetron sputtering method in the order of chromium first and gold later. The sensitive capacitor electrode 5 is used as a fixed electrode, and the pressure-sensitive film 4 is used as a movable electrode. The two constitute a sensitive capacitor. The capacitor gap 7 between the two serves as a measurement cavity for vacuum pressure. There is a pressure difference between the capacitor gap 7 and the sealed cavity above the pressure-sensitive film 4, so that the pressure-sensitive film 4 is deformed, resulting in a change in the sensitive capacitance. The extraction electrode 11 is used to lead out the wire of the sensitive capacitor electrode 5. The sensitive capacitor electrode 5 and the extraction electrode 11 are both composed of a chromium film and a gold film, and are plated on the surface of the base glass 1 by a magnetron sputtering method in the order of chromium first and gold later. The thickness of the chromium film is preferably 30nm, and the thickness of the gold film is preferably 330nm.

[0033] Furthermore, the top of the silicon substrate 2 is also provided with a first electrode lead-out port 12 and a second electrode lead-out port 13. The first electrode lead-out port 12 is used to lead out the sensitive capacitor electrode 5, and the second electrode lead-out port 13 is used to lead out the electrode of the pressure-sensitive film 4. The electrode lead-out port is mainly used to lead out the electrode capacitance signal. The electrodes of the sensitive capacitor electrode 5 and the pressure-sensitive film 4 are respectively led out to the circuit board from the first electrode lead-out port 12 and the second electrode lead-out port 13 by aluminum wire pressure welding. During measurement, the gas enters the capacitor gap 7 from the first electrode lead-out port 12, causing the pressure-sensitive film 4 to deform, so that the sensitive capacitor changes, thereby realizing the pressure measurement.

[0034] Furthermore, the material of the pressure-sensitive film 4 is boron-doped single-crystal silicon, and the whole is a square film with four rounded corners.

[0035] Furthermore, the silicon substrate 2 is made of an SOI wafer, the pressure-sensitive film 4 is located in a thin silicon layer, and the working sealing cavity 8 is located in a thick silicon layer.

[0036] Specifically, the pressure-sensitive film 4 is prepared on the silicon substrate 2 by a process of dry etching combined with wet etching. The pressure-sensitive film 4 is a square single-crystal silicon film, preferably with a side length of 2000 μm and a thickness of 6 μm. The gap between the pressure-sensitive film 4 and the sensitive capacitor electrode 5 is preferably 4 μm, and the fillet radius of the four corners of the pressure-sensitive film 4 is preferably 50 μm. During measurement, the pressure-sensitive film 4 is deformed by the pressure difference between the lower measuring cavity and the upper working sealed cavity, and the change signal is drawn out, and the vacuum pressure is measured according to the change amount.

[0037] Further, the getter block 6 is composed of a plurality of rectangular silicon wafers coated with Ti-Zr-V alloy non-evaporable getter films on the surface. The getter block 6 is preferably composed of four rectangular silicon wafers coated with Ti-Zr-V alloy non-evaporable getter films on the surface, which are respectively arranged in the first chamber 9 and the second chamber 10 for air absorption to ensure that the inside of the working sealed chamber 8 can maintain a high vacuum state.

[0038] Furthermore, the getter block 6 is activated during the anodic bonding process between the sealing glass 3 and the silicon substrate 2 .

[0039] Furthermore, the working sealed chamber 8, the first chamber 9 and the second chamber 10 are interconnected to form a sealed chamber, and the vacuum degree is less than 10 -2 The working sealed cavity 8 is connected to the first cavity 9 and the second cavity 10 on both sides through the connecting channel 14, and together they form a sealed cavity, and the overall vacuum degree is better than 10 -2 Pa, when measured, can be regarded as a low pressure reference, that is, as a measurement reference cavity for pressure comparison with the measurement cavity formed by the capacitor gap 7 below, the pressure to which the pressure-sensitive film 4 is subjected during operation can be regarded as an absolute pressure.

[0040] Furthermore, the measurement range of vacuum pressure is 1Pa~8.4×10 4 Pa.

[0041] Specifically, when manufacturing the embodiment of the present application, firstly, a 4-inch SOI wafer is selected as a substrate, and a pattern of a pressure-sensitive film 4 is obtained on the SOI thin silicon layer by photolithography, and then a capacitor gap 7 is obtained by dry etching; a 4-inch BF33 glass is selected as a base glass 1, and a pattern of a fixed metal electrode composed of an extraction electrode 11 and a sensitive capacitor electrode 5 is obtained by photolithography, and the extraction electrode 11 and the sensitive capacitor electrode 5 are obtained by magnetron sputtering and electrode stripping technology; the SOI wafer and the base glass 1 are bonded by anodic bonding, and the wafer after bonding is photolithographically processed on the other side to obtain the pattern of a working sealed cavity 8 of the pressure-sensitive film 4, a first cavity 9 and a second cavity 10, and a working sealed cavity 8 of the pressure-sensitive film 4 is obtained by wet etching. A sealing cavity 8 and a getter are placed in a first cavity 9 and a second cavity 10; a rectangular silicon wafer with a non-evaporable getter film coated on the surface, i.e., a getter block 6, is placed inside the first cavity 9 and inside the second cavity 10 respectively; in a high vacuum environment, a sealing glass 3 and a silicon substrate 2 are anodically bonded, and the getter block 6 is activated during the vacuum anodizing process, thereby obtaining a working sealed cavity 8, a first cavity 9 and a second cavity 10 with a high vacuum degree, and finally the entire wafer is diced to obtain a separate multi-sealed cavity MEMS capacitor thin film vacuum gauge, and the electrodes of the vacuum gauge are led out to the circuit board through the first electrode lead-out port 12 and the second electrode lead-out port 13 by aluminum wire pressure welding, thereby completing the production of the multi-sealed cavity MEMS capacitor thin film vacuum gauge.

[0042] More specifically, Figure 3 As shown, the embodiment of the present application is an absolute pressure vacuum gauge, which can accurately measure 1Pa~8.4×10 4 The vacuum pressure in the sealed cavity is less than 10 Pa, and the lower limit of measurement is 1 Pa. -2 Pa. And according to Figure 4 The test results shown indicate that when the vacuum gauge is placed in an atmospheric pressure storage environment, the maximum error of its output capacitance does not exceed 0.2% 6 months after the vacuum gauge is sealed. This indicates that the multi-sealed cavity MEMS capacitor thin film vacuum gauge provided in the embodiment of the present application has good long-term stability.

[0043] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-sealed cavity MEMS capacitance thin film vacuum gauge, characterized in that: It includes substrate glass, silicon substrate, sealing glass, pressure-sensitive film, fixed metal electrode and getter block, wherein: The silicon substrate is arranged above the substrate glass and bonded to the substrate glass; Obtaining the pressure-sensitive film in the middle of the silicon substrate by photolithography and dry etching; The fixed metal electrode is obtained in the middle of the substrate glass by photolithography and sputtering coating; A capacitance gap is formed between the fixed metal electrode and the pressure-sensitive film; Performing photolithography and etching on the silicon substrate to form a working sealed cavity above the pressure-sensitive film, and forming a first cavity and a second cavity above both sides of the pressure-sensitive film respectively; The working sealed chamber is communicated with the first chamber and the second chamber respectively through a connecting channel; Getter blocks are disposed inside the first chamber and the second chamber; The sealing glass is arranged above the silicon substrate and bonded to the silicon substrate.

2. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 1, characterized in that: The fixed metal electrodes include sensitive capacitor electrodes and lead-out electrodes, both of which are composed of chromium film and gold film, and are plated on the surface of the substrate glass in the order of chromium first and gold later by magnetron sputtering method.

3. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 2, characterized in that: A first electrode lead-out port and a second electrode lead-out port are also provided on the top of the silicon substrate. The first electrode lead-out port is used for leading out the sensitive capacitor electrode, and the second electrode lead-out port is used for leading out the pressure-sensitive film electrode.

4. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 3, characterized in that: The material of the pressure-sensitive film is boron-doped single-crystal silicon, and the whole is a square film with four rounded corners.

5. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 4, characterized in that: The silicon substrate is made of an SOI sheet, the pressure-sensitive film is located in a thin silicon layer, and the working sealing cavity is located in a thick silicon layer.

6. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 5, characterized in that: The getter block is composed of a plurality of rectangular silicon slices with Ti-Zr-V alloy non-evaporable getter films plated on the surfaces.

7. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 6, characterized in that: The getter block is activated during the anodic bonding of the sealing glass to the silicon substrate.

8. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 7, characterized in that: The working sealed cavity, the first chamber and the second chamber are interconnected to form a sealed cavity with a vacuum degree of less than 10 -2 Pa.

9. The multi-sealed cavity MEMS capacitance thin film vacuum gauge according to claim 8, characterized in that: The measurement range of vacuum pressure is 1Pa~8.4×10 4 Pa.

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