Internal atmosphere testing device for closed tiny vacuum cavity and calibration method

Abstract

The invention discloses an internal atmosphere testing device for a closed tiny vacuum cavity and a calibration method. The testing device comprises a calibration mechanism, a piercing mechanism and a test analysis mechanism which are connected in sequence, the sample is destroyed by the puncturing mechanism, so that the advantages of high precision and wide application range are obtained; a measurement and analysis mechanism is built by using a minimum leakage rate leak hole and a time-of-flight mass spectrometer, the test sensitivity of the device and the distinguishing capability of different gas components are improved, the measurable range of the device is expanded, and the calibration method comprises the following steps: introducing gas with known mass into the test device to verify the result accuracy and obtain the deviation coefficient of test data.

Description

Technical Field

[0001] The invention belongs to the field of vacuum technology, and more specifically to an internal atmosphere testing device and a calibration method for a sealed micro vacuum cavity. Background Art

[0002] With the rapid development of vacuum technology, sealed micro vacuum chambers have gradually been applied to products and facilities in various fields, becoming one of their indispensable prerequisites. Especially in the field of semiconductor industry, in recent years, with the development and application of semiconductor integrated circuits, the country's cutting-edge science and technology development has put forward higher requirements for semiconductor devices - extremely small size, long-term reliability, long service life, etc. The advantages of sealed micro vacuum chambers can fully meet the above needs. A good vacuum environment can control the gas composition and content that electronic components are exposed to, and at the same time can isolate heat and limit the operating temperature range of electronic components. Therefore, more and more sealed micro vacuum chambers are used in semiconductor devices.

[0003] Abnormal atmosphere inside a sealed micro vacuum cavity or excessive content of a certain component will have a strong impact on the performance, life and reliability of electronic components. For example, if the water vapor content inside the cavity is too high, it may condense into liquid on the surface of the electronic components, causing leakage of electronic components and affecting insulation performance. Therefore, how to measure the pressure and gas composition inside the sealed cavity with high precision and accuracy has become one of the necessary detection methods in the production and testing of semiconductor electronic components.

[0004] The existing chamber internal atmosphere testing devices have many defects, including: the detectable samples are single and can only be applied to specific samples; the pressure detection sensitivity is low and the resolution of different gas components is low; the measurement range is limited and most devices can only detect samples with a volume greater than 1cc; the measurement accuracy is low and there is a lack of calibration experiments for the test devices. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies, the present invention provides an internal atmosphere testing device and a calibration method for a sealed tiny vacuum cavity, which realizes precise puncture and destruction of the sealed tiny vacuum cavity by assembling a puncture unit and a carrying platform; a testing and analysis mechanism is formed by a very small leak rate hole and a time-of-flight mass spectrometer to improve the test sensitivity of the device and the ability to distinguish different gas components, and expand the measurement range; a calibration chamber is built by two ball valves, and a controllable gas of known volume and known pressure is introduced into the internal atmosphere testing device to simulate the process of puncture detection of the sealed tiny vacuum cavity, complete the device calibration experiment, and verify the accuracy of the test results of the internal atmosphere testing device.

[0006] The present invention adopts the following technical solutions to achieve the purpose of the invention:

[0007] The present invention is an internal atmosphere testing device for a sealed micro vacuum cavity, comprising a calibration mechanism, a piercing mechanism and a testing and analyzing mechanism connected in sequence; a calibration front stage chamber is arranged in the calibration mechanism; the calibration front stage chamber has three flange interfaces, namely, a front interface A, a front interface B and a front interface C, the front interface A is installed with a first full-range vacuum gauge, the front interface B is connected through a first angle valve and a rotary vane pump, and the front interface C is connected to one end of the calibration chamber; a first ball valve and a second ball valve connected to each other are arranged in the calibration chamber, and the other end of the calibration chamber is connected to the piercing mechanism; a piercing unit is arranged in the piercing mechanism; the piercing unit has four flange interfaces, namely, a unit interface A, a unit interface B, and a unit interface C. and unit interface D, the unit interface A is installed with a second full-range vacuum gauge, the unit interface B is connected to the sample carrying platform, the unit interface C is connected to the calibration chamber, and the unit interface C is connected to the test and analysis mechanism; an analysis chamber is arranged in the test and analysis mechanism; the analysis chamber has five flange interfaces, namely, analysis interface A, analysis interface B, analysis interface C, analysis interface D and analysis interface E, the analysis interface A is connected to a cold cathode ionization vacuum gauge, the analysis interface B is connected to a time-of-flight mass spectrometer, the analysis interface C is connected to a molecular pump group through a fourth angle valve, the analysis interface D is connected to a second angle valve, and the analysis interface E is connected to a third angle valve; the second angle valve is connected to a leak hole with a very small leak rate.

[0008] Preferably, the first ball valve and the second ball valve are connected by a stainless steel pipe, and polytetrafluoroethylene front and rear ferrules are selected to clamp the stainless steel pipe to the ball valve joint with the ferrule, and a torque wrench is used to apply a torque of 2N·m to tighten the ferrule to complete the connection and installation, and the space volume between the first ball valve and the second ball valve is adjusted by installing stainless steel pipes of different lengths and inner diameters;

[0009] Preferably, the piercing unit is externally provided with a shell of a full metal angle valve, which is used to ensure that the piercing unit is sealed inside the vacuum system; internally, the internal sealing copper pad of the full metal angle valve is replaced with a tungsten steel drill bit, which is used to achieve mechanical destruction of the sample;

[0010] Preferably, the sample carrying platform is a vacuum knife-edge blind flange, which has a rectangular parallelepiped groove at its inner center; the shape and depth of the rectangular parallelepiped groove inside the blind flange are processed according to the three-dimensional dimensions of width, height and depth of the sample to be tested;

[0011] Preferably, the second angle valve and the minimum leakage rate leak hole are connected to form a flow conduit, which is used to control the flow conductance to extend the time for the sample chamber gas to reach the analysis chamber through the pipeline, so that the time-of-flight mass spectrometer obtains sufficient test time to sample and analyze the gas inside the sample chamber;

[0012] Preferably, the extremely small leakage rate leak hole is an extremely small leakage rate vacuum leak hole element manufactured by MEMS ultraviolet lithography process and silicon-silicon direct bonding technology, and the leakage rate is less than 1×10 -11 Pa·m 3 / s, the required leakage rate can be selected by replacing the leakage hole element;

[0013] Also disclosed is a calibration method for the internal atmosphere testing device, comprising the following steps:

[0014] S1. Evacuate the internal atmosphere test device and use a heating device to bake and degas the entire device at high temperature. After the baking is completed and the device is completely cooled, close the third angle valve, use a very small leak rate leak to evacuate the sample chamber, and record the readings of the second full-scale vacuum gauge and the cold cathode ionization vacuum gauge;

[0015] S2, open the first ball valve, record the first full-scale vacuum gauge reading, close the first angle valve, start the time-of-flight mass spectrometer, open the second angle valve, and introduce gas into the internal atmosphere test device;

[0016] S3, record the changes of pressure in the sample chamber over time, and analyze the changes of pressure, gas type and partial pressure in the chamber over time;

[0017] S4. After the pressure in the analysis chamber returns to its initial state, close all angle valves and pump groups in the device, process the recorded data, and obtain the calibration experiment results.

[0018] The theoretical calculation of the calibration method of the internal atmosphere test device is described as follows:

[0019] The small hole conductance method is selected to measure the amount of gas released in the closed tiny vacuum cavity. The pressure change curve at both ends of the very small leakage hole is integrated by the integration method, and the total gas amount Q passing through the very small leakage hole is obtained as:

[0020]

[0021] Where C is the conductance of the center hole of the leak with the smallest leakage rate, P a is the internal pressure of the sample chamber, Pb is the internal pressure of the analysis chamber, t1 is the time point when the calibration gas is introduced into the sample chamber, and t2 is the time point when the internal pressure of the analysis chamber returns to the limit pressure.

[0022] The background leakage and material outgassing in the sample chamber cannot be ignored, so the outgassing rate q0 inside the sample chamber is:

[0023] q0=C (Pa0-Pb0)

[0024] Among them, P a0 is the ultimate pressure inside the sample chamber, P b0is the ultimate pressure inside the test chamber.

[0025] In actual situations, the total amount of gas passing through the extremely small leak rate hole includes the leakage inside the sample chamber and the outgassing of the material. Therefore, the amount of gas Q1 released in the closed tiny vacuum chamber measured by the extremely small leak rate hole is:

[0026]

[0027] The internal volume of the calibration chamber is measured by the gas expansion method, the basic principle of which is Boyle's law, that is, for a certain mass of gas, when the temperature remains unchanged, the pressure and volume are inversely proportional. Ignoring the temperature change, the standard volume chamber and the calibration chamber are connected to conduct a gas expansion experiment. The specific formula is as follows:

[0028] P α V α +P β V β =P y (V α +V β )

[0029] Among them, P α is the initial pressure of the standard volume chamber, V α is the volume of the standard volume chamber, P β is the initial pressure of the calibration chamber, V β is the internal volume of the calibration chamber, P γ It is the average pressure in the entire chamber after the gas expands.

[0030] At this time, the pressure and volume inside the calibration chamber are known, and the gas volume Q2 inside the calibration chamber can be calculated as:

[0031] Q2=P2×V β

[0032] Among them, P2 is the initial pressure inside the calibration chamber during the calibration experiment.

[0033] Then the test result deviation coefficient λ of the internal atmosphere test device can be calculated as:

[0034]

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. The present invention is aimed at different volumes (1 cc -0.001c c)'s enclosed tiny vacuum chamber is designed with a piercing mechanism. By modifying the angle valve, replacing the internal sealing copper gasket of the angle valve with a threaded tungsten steel drill bit, and cutting grooves inside the blind flange to carry and limit the position of the sample, it can achieve precise piercing and destruction of samples of different sizes and packaging materials, thereby improving the accuracy and success rate of destruction and has a wide range of applications.

[0037] 2. The present invention designs a test and analysis mechanism based on the characteristic that a sealed tiny vacuum cavity contains a very small amount of gas. It uses a leak hole with an extremely small leak rate and a time-of-flight mass spectrometer to improve the sensitivity of the test and analysis mechanism and the ability to distinguish different gas components, expand the measurable range of the mechanism, and achieve precise measurement of the amount of gas inside the sealed cavity.

[0038] 3. The present invention uses a calibration chamber to perform calibration experiments on the internal atmosphere test device. The volume and pressure inside the calibration chamber are controllable, and the device can be calibrated multiple times within a wide volume and pressure range to correct the device test data, obtain the deviation coefficient of the device test results, and optimize the device test data. This calibration method is also applicable to other test devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a partition diagram of the testing device of the present invention;

[0040] Figure 2 It is a schematic diagram of the structure of the testing device of the present invention;

[0041] Figure 3 A three-dimensional view of a piercing unit portion of the test device of the present invention;

[0042] Figure 4 is a cross-sectional view of a sample carrying platform in the testing device of the present invention;

[0043] Figure 5 A three-dimensional view of the test device of the present invention;

[0044] Numbers in the figure: 1 calibration mechanism, 2 piercing mechanism, 3 test and analysis mechanism, 11 first full-range vacuum gauge, 12 calibration front stage chamber, 13 first angle valve, 14 rotary vane pump, 15 calibration chamber, 151 first ball valve, 152 second ball valve, 21 second full-range vacuum gauge, 22 piercing unit, 23 sample chamber, 24 sample carrying platform, 31 second angle valve, 32 extremely small leak rate leak, 33 third angle valve, 34 cold cathode ionization vacuum gauge, 35 analysis chamber, 36 time-of-flight mass spectrometer, 37 fourth angle valve, 38 molecular pump, 39 front stage pump. DETAILED DESCRIPTION

[0045] See also Figure 1, a device for testing the internal atmosphere of a sealed micro vacuum cavity, comprising a calibration mechanism 1, a piercing mechanism 2 and a testing and analyzing mechanism 3 which are connected in sequence.

[0046] See also Figure 2 , Figure 3 , Figure 4 and Figure 5 A calibration pre-stage chamber 12 is arranged in the calibration mechanism 1; the calibration pre-stage chamber 12 has three flange interfaces, one of which is installed with a first full-range vacuum gauge 11, a second is connected with a rotary vane pump 14 through a first angle valve 13, and a third is connected with a calibration chamber 15; a first ball valve 151 and a second ball valve 152 are arranged in the calibration chamber 15, and the other end of the first ball valve 151 and the second ball valve 152 are connected with each other, and the other end is connected with the piercing mechanism 2; the first ball valve 151 and the second ball valve 152 are connected with each other through a stainless steel pipe and a Swagelok ferrule, and the length and inner diameter of the stainless steel pipe are adjustable; a piercing unit 22 is arranged in the piercing mechanism 2; the piercing unit 22 is modified by replacing the internal sealing copper gasket of the all-metal angle valve with a threaded tungsten steel drill bit; the piercing unit 22 has four flange interfaces, one of which is installed with a second full-range vacuum gauge 21, a second is connected with a sample carrying platform 24, and the other two are respectively connected with a sample carrying platform 24, and a sample carrying platform 24 is ... The calibration chamber 23 and the test and analysis mechanism 3 are connected; an analysis chamber 35 is arranged in the test and analysis mechanism 3; the sample carrying platform 24 is a blind flange with a groove in the center, and the size of the groove can be adjusted according to the sample to be tested; the analysis chamber 35 has five flange interfaces, one of which is connected to the cold cathode ionization vacuum gauge 34, the second is connected to the time-of-flight mass spectrometer 36, the third is connected to the molecular pump group through the fourth angle valve 37, and the last two are connected to the second angle valve 31 and the third angle valve 33 respectively; the second angle valve 31 is connected to the minimum leakage rate leak 32, and together constitute a flow conduit pipeline for controlling the flow conductance to extend the time for the gas in the sample chamber 23 to reach the analysis chamber 35 through the pipeline, ensuring that the time-of-flight mass spectrometer 36 has sufficient test time to sample and analyze the gas inside the sample chamber 23; the size of the center hole of the minimum leakage rate leak 32 is adjustable.

[0047] The internal atmosphere test of a closed micro vacuum cavity using the test device of the present invention is completed according to the following steps:

[0048] The first step is to open the second angle valve 31, the third angle valve 33, and the fourth angle valve 37, close the first angle valve 13, the first ball valve 151, and the second ball valve 152, open the second full-scale vacuum gauge 21, and open the front pump 39 to evacuate the piercing mechanism 2 and the test and analysis mechanism 3, observe the reading of the second full-scale vacuum gauge 21, and when the reading is less than 0.1Pa, open the molecular pump 38, open the cold cathode ionization vacuum gauge 34 to observe the pressure reading, and evacuate the two mechanisms to the limit pressure. Close the second full-scale vacuum gauge 21 and the cold cathode ionization vacuum gauge 34, and use a heating device to perform high-temperature baking and degassing on the entire device.

[0049] Step 2: After the baking is completed and the device is completely cooled, open the second full-scale vacuum gauge 21 and the cold cathode ionization vacuum gauge 34. Close the third angle valve 33, record the change curves of the second full-scale vacuum gauge 21 and the cold cathode ionization vacuum gauge 34, calculate the background degassing of the sample chamber 23, and open the third angle valve 33 to pump the piercing mechanism 2 back to the limit pressure.

[0050] The third step is to close the third angle valve 33, use the piercing unit 22 to destroy the sample, observe and record the changes in the readings of the second full-scale vacuum gauge 21 and the cold cathode ionization vacuum gauge 34, and simultaneously turn on the time-of-flight mass spectrometer 36 to analyze the gas composition.

[0051] The above operations can complete the internal atmosphere test experiment of the closed micro vacuum cavity, and the internal pressure and gas composition analysis results of the cavity can be obtained by processing the experimental measured data.

[0052] The calibration method for the internal atmosphere testing device in this embodiment includes the following steps: Figure 2 As shown:

[0053] S1. Evacuate the internal atmosphere test device and use a heating device to bake and degas the entire device at high temperature. After the baking is completed and the device is completely cooled, close the third angle valve 33, use the extremely small leakage rate leak 32 to evacuate the sample chamber, and record the readings of the second full-scale vacuum gauge 21 and the cold cathode ionization vacuum gauge 34;

[0054] S2, open the first ball valve, record the reading of the first full-scale vacuum gauge 11, close the first angle valve 13, start the time-of-flight mass spectrometer 36, open the second angle valve 31, and introduce gas into the internal atmosphere test device;

[0055] S3, recording the changes of the pressure in the sample chamber 23 over time, and the changes of the pressure, gas type and partial pressure in the analysis chamber 35 over time;

[0056] S4. After the pressure in the analysis chamber 35 returns to the initial state, all angle valves and pump groups of the device are closed, and the recorded data are processed to obtain the calibration experiment results.

[0057] The above operation can complete the internal atmosphere calibration experiment of the closed micro vacuum cavity. The data measured in the experiment can be processed to compare the deviation between the known pressure and gas composition in the calibration chamber 15 and the results measured by the device, and obtain the device measurement deviation coefficient.

[0058] This article describes the specific implementation methods of the present invention, but it should be clear that the present invention is not limited to the specific implementation methods, and all inventions created based on the present invention are within the scope of protection.

Claims

1. A device for testing the internal atmosphere of a sealed micro vacuum cavity, characterized in that: The invention comprises a calibration mechanism (1), a piercing mechanism (2) and a testing and analyzing mechanism (3) which are connected in sequence; a calibration forestage chamber (12) is arranged in the calibration mechanism (1); the calibration forestage chamber (12) has three flange interfaces, namely, a front interface A, a front interface B and a front interface C; the front interface A is installed with a first full-range vacuum gauge (11); the front interface B is connected to a rotary vane pump (14) via a first angle valve (13); the front interface C is connected to one end of a calibration chamber (15); a first ball valve (151) and a second ball valve (152) which are connected to each other are arranged in the calibration chamber (15); the other end of the calibration chamber (15) is connected to the piercing mechanism (2); a piercing unit (22) is arranged in the piercing mechanism (2); the piercing unit (22) has four flange interfaces, namely, a unit interface A, a unit interface B, a unit interface C and a unit interface Port D, the unit interface A is installed with a second full-scale vacuum gauge (21), the unit interface B is connected to the sample carrying platform (24), the unit interface C is connected to the calibration chamber (15), and the unit interface D is connected to the test and analysis mechanism (3); an analysis chamber (35) is arranged in the test and analysis mechanism (3); the analysis chamber (35) has five flange interfaces, namely, analysis interface A, analysis interface B, analysis interface C, analysis interface D and analysis interface E, the analysis interface A is connected to the cold cathode ionization vacuum gauge (34), the analysis interface B is connected to the time-of-flight mass spectrometer (36), the analysis interface C is connected to the molecular pump group through the fourth angle valve (37), the analysis interface D is connected to the second angle valve (31), and the analysis interface E is connected to the third angle valve (33); the second angle valve (31) is connected to the extremely small leakage rate leak hole (32).

2. The internal atmosphere testing device for a sealed micro vacuum cavity according to claim 1, characterized in that: The first ball valve (151) and the second ball valve (152) are connected via a stainless steel pipe. Polytetrafluoroethylene front and rear ferrules are selected to clamp the stainless steel pipe onto the ball valve joint with the ferrule. A torque wrench is used to apply a torque of 2 N·m to tighten the ferrule to complete the connection installation. The space volume between the first ball valve and the second ball valve is adjusted by installing stainless steel pipes of different lengths and inner diameters.

3. The internal atmosphere testing device for a sealed micro vacuum cavity according to claim 1, characterized in that: The piercing unit has an outer shell of a full metal angle valve on the outside, which is used to ensure that the piercing unit is sealed inside the vacuum system; the inner sealing copper pad of the full metal angle valve is replaced with a tungsten steel drill bit on the inside, which is used to achieve mechanical destruction of the sample.

4. The internal atmosphere testing device for a sealed micro vacuum cavity according to claim 1, characterized in that: The sample carrying platform is a vacuum knife-edge blind flange, which has a rectangular groove at its inner center. The shape and depth of the rectangular groove inside the blind flange are processed according to the three-dimensional dimensions of width, height and depth of the sample to be tested.

5. The internal atmosphere testing device for a sealed micro vacuum cavity according to claim 1, characterized in that: The second angle valve (31) and the extremely small leakage rate leak hole (32) are connected to form a flow conduit, which is used to control the flow conductance to extend the time it takes for the gas in the sample chamber to reach the analysis chamber through the pipeline, so that the time-of-flight mass spectrometer (36) obtains sufficient test time to sample and analyze the gas inside the sample chamber.

6. The internal atmosphere testing device for a sealed micro vacuum cavity according to claim 1, characterized in that: The extremely small leakage rate leak hole (32) is an extremely small leakage rate vacuum leak hole element manufactured by using MEMS ultraviolet photolithography technology and silicon-silicon direct bonding technology, and the leakage rate is less than 1×10 -11 Pa·m 3 / s, the required leakage rate can be selected by replacing the leakage hole element.

7. A calibration method for a sealed micro vacuum cavity, characterized by: The internal atmosphere testing device for sealing a micro vacuum cavity as described in any one of claims 1 to 6 is carried out in the following steps: S1. The internal atmosphere test device after assembly is completely sealed, and the internal atmosphere test device is roughly vacuumed, and the entire device is baked at 180°C for 24 hours using a heating belt; after the baking is completed and the device is naturally cooled to room temperature, the third angle valve is closed, so that the molecular pump group only evacuates the sample chamber through the extremely small leakage rate hole, and the initial pressure readings of the second full-scale vacuum gauge and the cold cathode ionization vacuum gauge are recorded. The real number is the background pressure value of the calibration chamber and the analysis chamber; S2, open the first ball valve, record the first full-scale vacuum gauge reading, which is the pressure value of the calibration gas subsequently introduced into the calibration chamber, close the first ball valve, start the time-of-flight mass spectrometer, and open the second ball valve; record the change in the second full-scale vacuum gauge pressure reading, which is the change of the pressure in the sample chamber over time, and at the same time record the change in the cold cathode ionization vacuum gauge pressure reading and the mass spectrometer's pressure monitoring curve for each gas component in the analysis chamber, which is the change of the pressure, gas type, and partial pressure in the analysis chamber over time; S3. After the pressure in the analysis chamber returns to the initial pressure indication, close all angle valves and pump groups of the device, perform integral calculation on the recorded pressure indication change data of the second full-scale vacuum gauge and the cold cathode ionization vacuum gauge, and enter the device test result of the total amount of gas in the calibration chamber. By comparing it with the initial calibration gas total amount, the calibration experiment result can be obtained.

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