Method for controlling the heating current of the filament in a Pirani vacuum transmitter and the Pirani vacuum transmitter itself.

Abstract

This invention discloses a method for controlling the heating current of a Pirani vacuum transmitter filament and a Pirani vacuum transmitter, relating to the field of vacuum measurement technology. The key technical points are: determining the vacuum degree change rate and acceleration of the Pirani vacuum transmitter filament based on the vacuum degree at each sampling interval and the sampling interval time; fitting the predicted vacuum degree of the Pirani vacuum transmitter filament at future times based on the vacuum degree, vacuum degree change rate, and vacuum degree acceleration; acquiring the real-time voltage value of the Pirani vacuum transmitter filament; determining the predicted voltage value of the Pirani vacuum transmitter filament at future times based on the temperature compensation coefficient corresponding to the predicted vacuum degree and the real-time voltage value; determining the compensation voltage of the Pirani vacuum transmitter filament based on the predicted voltage value and the real-time voltage value; and superimposing the compensation voltage onto the PID feedback loop to control the magnitude of the heating current of the Pirani vacuum transmitter filament.

Description

Technical Field

[0001] This invention relates to the field of vacuum measurement technology, and more specifically, to a method for controlling the heating current of a Pirani vacuum transmitter filament and a Pirani vacuum transmitter. Background Technology

[0002] The Pirani vacuum transmitter is a vacuum measuring instrument based on the relationship between gas thermal conductivity and pressure. Its working principle is to measure the temperature change of the heating wire to reflect the pressure change of the surrounding gas, thereby realizing the measurement of vacuum degree.

[0003] Industrial-grade precision Pirani vacuum transmitters differ from ordinary Pirani vacuum transmitters. Industrial-grade precision products must meet the requirements of applications such as semiconductor manufacturing and vacuum coating, and are designed for applications requiring a minimum operating temperature of 10°C. 0 Pa-10 3 The stringent requirements include a maximum permissible error of less than ±10% for the Pa pressure range and a response time of less than 200 ms.

[0004] Currently, most Pirani vacuum transmitters use PID closed-loop control to maintain a constant filament temperature. However, when the vacuum level changes rapidly (such as during the evacuation and venting of process chambers), the nonlinearity of thermal conductivity causes the PID closed-loop control to lag, leading to measurement errors. 0 Pa-10 3 The error within the Pa pressure range is between ±15% and ±30%, and the response time is typically around 1.2 seconds. Summary of the Invention

[0005] The purpose of this invention is to provide a heating current control method for the filament of a Pirani vacuum transmitter and a Pirani vacuum transmitter, which solves the problem of insufficient measurement accuracy caused by the response lag resulting from the constant temperature control method used in traditional Pirani vacuum transmitters.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for controlling the heating current of a Pirani vacuum transmitter filament, the method comprising:

[0008] The ambient temperature and voltage values ​​of the Pirani vacuum transmitter filament are collected according to the pre-configured sampling interval.

[0009] Determine the temperature compensation coefficient of the Pirani vacuum transmitter filament based on the ambient temperature.

[0010] The vacuum level of the Pirani vacuum transmitter filament at each sampling interval is determined based on the voltage value and temperature compensation coefficient.

[0011] Based on the vacuum level at each sampling interval and the sampling interval time, determine the vacuum level change rate and vacuum level change acceleration of the Pirani vacuum transmitter filament;

[0012] The predicted vacuum level of the Pirani vacuum transmitter filament at future moments is fitted based on vacuum level, vacuum level change rate, and vacuum level change acceleration.

[0013] The real-time voltage value of the Pirani vacuum transmitter filament is collected, and the predicted voltage value of the Pirani vacuum transmitter filament at future times is determined based on the temperature compensation coefficient corresponding to the predicted vacuum level and the real-time voltage value.

[0014] The compensation voltage of the Pirani vacuum transmitter filament is determined based on the predicted voltage value and the real-time voltage value. The compensation voltage is then superimposed on the PID feedback loop to control the magnitude of the heating current of the Pirani vacuum transmitter filament.

[0015] In one implementation, the vacuum level of the Pirani vacuum transmitter filament at each sampling interval is determined based on the voltage value and the temperature compensation coefficient, specifically as follows:

[0016] Determine the pressure based on the voltage value and the table showing the relationship between voltage and pressure;

[0017] Multiplying the pressure by the temperature compensation coefficient yields the vacuum level of the Pirani vacuum transmitter filament at each sampling interval.

[0018] In one implementation scheme, the vacuum degree change rate of the Pirani vacuum transmitter filament is determined based on the vacuum degree at each sampling interval time point and the sampling interval time. Specifically, the vacuum degree change rate of the Pirani vacuum transmitter filament is calculated based on the difference in vacuum degree between adjacent sampling points and the sampling interval time.

[0019] In one implementation scheme, the acceleration of vacuum change of the Pirani vacuum transmitter filament is determined based on the vacuum level at each sampling interval time point and the sampling interval time. Specifically, the acceleration of vacuum change of the Pirani vacuum transmitter filament is calculated based on the rate of change of vacuum level at adjacent sampling points and the sampling interval time.

[0020] In one implementation, the predicted vacuum level of the Pirani vacuum transmitter filament at a future time is fitted based on the vacuum level, the rate of change of vacuum level, and the acceleration of the change of vacuum level. Specifically:

[0021] The vacuum degree, vacuum degree change rate, and vacuum degree change acceleration were fitted using the least squares method to obtain the vacuum degree prediction model for the Pirani vacuum transmitter filament.

[0022] The vacuum level of the Pirani vacuum transmitter filament at future moments is predicted based on a vacuum level prediction model.

[0023] In one implementation, the vacuum prediction model includes models of the Pirani vacuum transmitter in evacuation, venting, and steady-state conditions.

[0024] In one implementation scheme, the expression for the vacuum degree prediction model under evacuation conditions is: Where Py represents the predicted vacuum level, Sp represents the rate of change of vacuum level, T represents the sampling interval time, a represents the acceleration of vacuum level change, and P0 represents the vacuum level.

[0025] In one implementation scheme, the expression for the vacuum degree prediction model in the venting state is: Where Py represents the predicted vacuum level, Sp represents the rate of change of vacuum level, T represents the sampling interval time, a represents the acceleration of vacuum level change, and P0 represents the vacuum level.

[0026] In one implementation scheme, the expression for the vacuum degree prediction model in steady state is: Py≈P0; where Py represents the predicted vacuum degree and P0 represents the vacuum degree.

[0027] A second aspect of the present invention provides a Pirani vacuum transmitter, characterized in that it is used to perform a heating current control method for a Pirani vacuum transmitter filament as provided in the first aspect of the present invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention collects ambient temperature and voltage values ​​of the filament, calculates multi-dimensional parameters such as vacuum degree, vacuum degree change rate, and vacuum degree change acceleration, and uses these to fit a vacuum degree prediction model for the Pirani vacuum transmitter filament under evacuation, venting, and steady-state conditions. Based on the predicted vacuum degree of the Pirani vacuum transmitter filament at future moments, and combined with a temperature compensation coefficient, determines the predicted voltage value of the Pirani vacuum transmitter filament at future moments. Thus, the voltage that needs to be compensated at future moments can be determined. This compensated voltage is then superimposed on the PID feedback loop to adjust the output power, achieving overshoot suppression and rapid stabilization of the heating filament temperature within 10... 0 Pa-10 3 Pa improves the measurement accuracy and reduces the response time of the vacuum gauge under dynamic operating conditions. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 A flowchart illustrating a heating current control method for a Pirani vacuum transmitter filament, provided as an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that the terms "comprising" or "may include" used in the various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in the various embodiments of this application, the terms "comprising," "having," and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0034] It should be understood that terms such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] The Pirani vacuum transmitter is a vacuum measuring instrument based on the relationship between gas thermal conductivity and pressure. Its working principle is to measure the temperature change of the heating wire to reflect the pressure change of the surrounding gas, thereby realizing the measurement of vacuum degree.

[0036] Industrial-grade precision Pirani vacuum transmitters differ from ordinary Pirani vacuum transmitters. Industrial-grade precision products must meet the requirements of applications such as semiconductor manufacturing and vacuum coating, and are designed for applications requiring a minimum operating temperature of 10°C. 0 Pa-10 3 The stringent requirements include a maximum permissible error of less than ±10% and a response time of less than 200ms within the Pa pressure range.

[0037] Currently, most Pirani vacuum transmitters use PID closed-loop control to maintain a constant filament temperature. However, when the vacuum level changes rapidly (such as during the evacuation and venting of process chambers), the nonlinearity of thermal conductivity causes the PID closed-loop control to lag, leading to measurement errors. 0 Pa-10 3 The error within the Pa pressure range is between ±15% and ±30%, and the response time is typically around 1.2 seconds.

[0038] To address the insufficient measurement accuracy caused by the response lag in traditional Pirani vacuum transmitters using isothermal control, this invention proposes a heating current control method for the filament of a Pirani vacuum transmitter. This method collects the ambient temperature and voltage values ​​of the filament, calculates multi-dimensional parameters such as vacuum degree, vacuum degree change rate, and vacuum degree change acceleration, and uses these to fit a vacuum degree prediction model of the Pirani vacuum transmitter filament under evacuation, venting, and steady-state conditions. Based on the predicted vacuum degree of the Pirani vacuum transmitter filament at future moments, and combined with a temperature compensation coefficient, determines the predicted voltage value of the Pirani vacuum transmitter filament at future moments. Thus, the voltage requiring future compensation can be determined. This compensation voltage is then superimposed on the PID feedback loop to adjust the output power, achieving overshoot suppression and rapid stabilization of the heating filament temperature within 10... 0 Pa--10 3 Pa improves the measurement accuracy and reduces the response time of the vacuum gauge under dynamic operating conditions.

[0039] This invention is primarily applicable to industrial manufacturing scenarios with extremely high requirements for vacuum monitoring, such as the semiconductor manufacturing field. In core processes like chemical vapor deposition (CVD) and physical vapor deposition (PVD) in wafer fabrication, even minute fluctuations in vacuum directly affect the uniformity of thin film deposition and device yield. This invention can adapt to dynamic changes in the pressure of the process chamber in real time, providing accurate data for process control and facilitating stable production of processes below 7nm.

[0040] For example, in optical coating, decorative coating, and photovoltaic cell coating processes, a stable medium-low vacuum environment must be maintained to ensure film adhesion and optical properties. The rapid response capability of this invention can effectively suppress pressure overshoot during chamber evacuation, reducing the defect rate.

[0041] For example, in space environment simulation chambers and material surface analysis equipment, this invention can improve the dynamic performance of vacuum measurements and ensure the accuracy of experimental data.

[0042] This invention overcomes the technical bottleneck of traditional Pirani vacuum transmitters that rely on single PID control, deeply integrating predictive control algorithms with a vacuum measurement physical model, achieving an upgrade from passive feedback to active prediction. In industrial applications, at 10... 0 Pa-10 3 Pa enables the Pirani vacuum transmitter to achieve a measurement accuracy of less than 10% under dynamic operating conditions and a response time of less than 200ms, while improving the process stability of the entire vacuum system.

[0043] The heating current control method for the filament of a Pirani vacuum transmitter provided by the present invention will be described in detail below with reference to specific implementation schemes, such as... Figure 1 As shown, the method includes the following steps:

[0044] S101 collects the ambient temperature and voltage values ​​of the Pirani vacuum transmitter filament according to the pre-configured sampling interval.

[0045] Specifically, the Pirani vacuum transmitter includes a temperature sensor and a filament. When the Pirani vacuum transmitter starts working, the temperature sensor measures the tube temperature of the Pirani vacuum transmitter, which is the ambient temperature Te of the Pirani vacuum transmitter.

[0046] The filament is usually made of tungsten or platinum and is used to measure the vacuum level P.

[0047] Voltage values ​​can be acquired through an ADC sampling circuit, which is common knowledge in this technical field, and will not be described further in this embodiment.

[0048] S102, determine the temperature compensation coefficient of the Pirani vacuum transmitter filament based on the ambient temperature.

[0049] In this embodiment, the ambient temperature and temperature compensation coefficient can be pre-measured experimentally to determine the temperature compensation coefficient corresponding to each ambient temperature, thereby forming a relationship table between ambient temperature and temperature compensation coefficient. For example, the temperature compensation coefficient corresponding to 23°C is 1, and the temperature compensation coefficient for each degree Celsius from 5°C to 50°C increases from 0.9578 to 1.0752. This temperature compensation coefficient is measured through the vacuum system in the constant temperature chamber. First, it is measured at a given pressure (generally 3000Pa-100000Pa, taking 5 fixed points such as 6000Pa, 9000Pa) at a room temperature of 23°C. 30000Pa, 60000Pa, 100000Pa. Five fixed points (0.3Pa, 3Pa, 30Pa, 300Pa, 3000Pa) were measured at 0.1Pa-3000Pa, resulting in 10 sets of voltage values. Then, the temperature of the constant temperature chamber was varied (5°C-50°C), and 46 sets of voltage values ​​were measured at 46 different temperatures under constant vacuum. The average of the 10 voltage values ​​at each 1°C was compared to the voltage at room temperature (23°C) to obtain the corresponding compensation coefficient (0.9578 for 5°C and 1.0752 for 50°C). The temperature compensation coefficient at the current ambient temperature can then be determined by referring to a table.

[0050] S103, based on the voltage value and temperature compensation coefficient, determines the vacuum level of the Pirani vacuum transmitter filament at each sampling interval.

[0051] In this embodiment, firstly, the pressure is determined according to the voltage value and the voltage-pressure relationship table; then, the pressure is multiplied by the temperature compensation coefficient to obtain the vacuum degree of the Pirani vacuum transmitter filament at each sampling interval.

[0052] Here, the voltage and pressure values ​​can be pre-measured experimentally to determine the pressure value corresponding to each voltage value, thus creating a table showing the relationship between voltage and pressure. Examples include: 10, 17, 23, 30, 37, 43, 50, 57, 63, 70, 77, 83, 90, 95, 100, 108, 115, 123, 131, 138, 146, 154, 162, 169, 177, 185, 192, 200, 211, 222, 233, 244. 256, 267, 278, 289, 300, 311, 322, 333, 344, 356, 367, 378, 389, 400, 414, 429, 443, 457, 471, 486, 500, 513, 525, 538, 550, 563, 575, 588, 600, 617, 633, 650, 667, 683, 700, 715, 731, 746, 762, 777, 792 808, 823, 838, 854, 869, 885, 900, 920, 940, 960, 980, 1000, 1018, 1036, ..., 220000, 230000, 250000, 260000, 280000, 300000, 325000, 350000, 375000, 400000, 450000, 500000, 566667, 633333, 70 0000, 800000, 1000000, 1200000, 1500000, 1900000, 2600000, 3300000, 4000000, 4500000, 5000000, 5500000, 6000000, 6285714, 6571429, 6857143, 7142857, 7428571, 7714286, 8000000, 8333333,

[0053] A total of 500 data points, including 8666667, 9000000, 9533333, 10000000, and 10000000, are used. By controlling the vacuum calibration system at 23°C with pressure ranging from 0.1 Pa to 100000 Pa, the corresponding sensor voltage values, such as 0V to 5V, are measured. These 500 data points are mapped to the above data points. Then, by looking up a table, the pressure at the current voltage value can be determined. Multiplying the pressure by the temperature compensation coefficient, the vacuum level of the Pirani vacuum transmitter filament at each sampling interval can be obtained.

[0054] S104. Based on the vacuum level at each sampling interval and the sampling interval time, determine the vacuum level change rate and vacuum level change acceleration of the Pirani vacuum transmitter filament.

[0055] In this embodiment, the vacuum degree change rate of the Pirani vacuum transmitter filament is calculated based on the difference in vacuum degree between adjacent sampling points and the sampling interval time.

[0056] For example, the vacuum change rate Sp is calculated at adjacent sampling points d1 and d2 using the following steps: Where P1 represents the vacuum level at sampling point d1, P2 represents the vacuum level at sampling point d2, and T represents the sampling interval.

[0057] S105, based on vacuum level, vacuum level change rate and vacuum level change acceleration, fits the predicted vacuum level of the Pirani vacuum transmitter filament at future moments.

[0058] In this embodiment, the acceleration of vacuum change of the Pirani vacuum transmitter filament is calculated based on the rate of change of vacuum at adjacent sampling points and the sampling interval.

[0059] Specifically, as described in step S104 above, P1 represents the vacuum level at sampling point d1, and P2 represents the vacuum level at sampling point d2. In order to solve the acceleration of the change in vacuum level, a new sampling point d3 needs to be introduced, and the vacuum level P3 at sampling point d3 needs to be calculated.

[0060] Combine the vacuum levels P1, P2, and P3 at the three sampling points with the interval time T;

[0061] The acceleration 'a' due to the change in vacuum can be calculated using the following steps:

[0062] ; ; where Sp1 represents the rate of change of vacuum degree at sampling point d1, and Sp2 represents the rate of change of vacuum degree at sampling point d2.

[0063] ; .

[0064] S106: Collect the real-time voltage value of the Pirani vacuum transmitter filament, and determine the predicted voltage value of the Pirani vacuum transmitter filament at future times based on the temperature compensation coefficient corresponding to the predicted vacuum level and the real-time voltage value.

[0065] In this embodiment, the least squares method is used to fit the vacuum degree, the rate of change of vacuum degree, and the acceleration of change of vacuum degree to obtain the vacuum degree prediction model of the Pirani vacuum transmitter filament; based on the vacuum degree prediction model, the predicted vacuum degree of the Pirani vacuum transmitter filament at future times is fitted.

[0066] The vacuum degree prediction model includes models for the Pirani vacuum transmitter in evacuation, venting, and steady-state conditions. Specifically, the expression for the vacuum degree prediction model in evacuation condition is as follows: Where Py represents the predicted vacuum level, Sp represents the rate of change of vacuum level, T represents the sampling interval, a represents the acceleration of vacuum level change, and P0 represents the vacuum level. The expression for the vacuum level prediction model in the venting state is: The expression for the vacuum degree prediction model in steady state is: Py≈P0.

[0067] S107 determines the compensation voltage of the Pirani vacuum transmitter filament based on the predicted voltage value and the real-time voltage value, and superimposes the compensation voltage onto the PID feedback loop to control the magnitude of the heating current of the Pirani vacuum transmitter filament.

[0068] Based on the description in the above embodiment, the predicted voltage value of the filament is Vdy, and the real-time voltage value of the filament is Vd. Therefore, the predicted compensation voltage ΔV is obtained by using ΔV = Vdy - Vd. The control DAC superimposes the compensation voltage output onto the traditional PID feedback loop, adjusting the output power in advance to achieve rapid control, reduce the response time of the Pirani vacuum transmitter, and improve the measurement accuracy of the Pirani vacuum transmitter.

[0069] This embodiment also provides a Pirani vacuum transmitter for executing a heating current control method for the filament of a Pirani vacuum transmitter described in the above embodiment.

[0070] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the heating current of a Pirani vacuum transmitter filament, characterized in that the method... include: The ambient temperature and voltage values ​​of the Pirani vacuum transmitter filament are collected according to the pre-configured sampling interval. Determine the temperature compensation coefficient of the Pirani vacuum transmitter filament based on the ambient temperature. The vacuum level of the Pirani vacuum transmitter filament at each sampling interval is determined based on the voltage value and temperature compensation coefficient. Based on the vacuum level at each sampling interval and the sampling interval time, determine the vacuum level change rate and vacuum level change acceleration of the Pirani vacuum transmitter filament; The predicted vacuum level of the Pirani vacuum transmitter filament at future moments is fitted based on vacuum level, vacuum level change rate, and vacuum level change acceleration. The real-time voltage value of the Pirani vacuum transmitter filament is collected, and the predicted voltage value of the Pirani vacuum transmitter filament at future times is determined based on the temperature compensation coefficient corresponding to the predicted vacuum level and the real-time voltage value. The compensation voltage of the Pirani vacuum transmitter filament is determined based on the predicted voltage value and the real-time voltage value. The compensation voltage is then superimposed on the PID feedback loop to control the magnitude of the heating current of the Pirani vacuum transmitter filament.

2. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 1, characterized in that, Based on the voltage value and temperature compensation coefficient, the vacuum level of the Pirani vacuum transmitter filament at each sampling interval is determined as follows: Determine the pressure based on the voltage value and the table showing the relationship between voltage and pressure; Multiplying the pressure by the temperature compensation coefficient yields the vacuum level of the Pirani vacuum transmitter filament at each sampling interval.

3. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 1, characterized in that, The vacuum degree change rate of the Pirani vacuum transmitter filament is determined based on the vacuum degree at each sampling interval and the sampling interval time. Specifically, the vacuum degree change rate of the Pirani vacuum transmitter filament is calculated based on the difference in vacuum degree between adjacent sampling points and the sampling interval time.

4. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 3, characterized in that, Based on the vacuum level at each sampling interval and the sampling interval time, the acceleration of vacuum level change of the Pirani vacuum transmitter filament is determined. Specifically, the acceleration of vacuum level change of the Pirani vacuum transmitter filament is calculated based on the rate of change of vacuum level at adjacent sampling points and the sampling interval time.

5. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 1, characterized in that, The predicted vacuum level of the Pirani vacuum transmitter filament at future moments is fitted based on the vacuum level, the rate of change of vacuum level, and the acceleration of the change of vacuum level. Specifically: The vacuum degree, vacuum degree change rate, and vacuum degree change acceleration were fitted using the least squares method to obtain the vacuum degree prediction model for the Pirani vacuum transmitter filament. The vacuum level of the Pirani vacuum transmitter filament at future moments is predicted based on a vacuum level prediction model.

6. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 5, characterized in that, The vacuum prediction model includes models of the Pirani vacuum transmitter in pumping, venting, and steady-state conditions.

7. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 6, characterized in that, The expression for the vacuum degree prediction model under evacuation conditions is: Where Py represents the predicted vacuum level, Sp represents the rate of change of vacuum level, T represents the sampling interval time, a represents the acceleration of vacuum level change, and P0 represents the vacuum level.

8. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 6, characterized in that, The expression for the vacuum degree prediction model under the venting state is: Where Py represents the predicted vacuum level, Sp represents the rate of change of vacuum level, T represents the sampling interval time, a represents the acceleration of vacuum level change, and P0 represents the vacuum level.

9. The heating current control method for the filament of a Pirani vacuum transmitter according to claim 6, characterized in that, The expression for the vacuum degree prediction model in steady state is: Py≈P0; where Py represents the predicted vacuum degree and P0 represents the vacuum degree.

10. A Pirani vacuum transmitter, characterized in that, This method is used to perform a heating current control method for a Pirani vacuum transmitter filament as described in any one of claims 1 to 9.

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