Impedance matching method and device for radio frequency power supply in plasma system

Abstract

The invention provides an impedance matching method and device for a radio frequency power supply in a plasma system, and the method comprises the steps: obtaining the current input impedance of a matching network under an impedance matching condition, and calculating the current reflection power of the matching network based on the current input impedance of the matching network, updating the inductance value of the first inductor based on the difference between the reflection power of the matching network in the last round of iteration process and the current reflection power, the difference between the updated inductance value of the first inductor in the last round of iteration process and the inductance value before updating, and the updated inductance value of the first inductor in the last round of iteration process; under the impedance mismatch condition, the capacitance values of the first capacitor and the second capacitor of the matching network are adjusted until impedance matching, and the influence of the first inductor connected in series with the first capacitor in the matching network on the reflection power of the matching network is minimized, so that the adjustment accuracy of the adjustable capacitor is improved and the adjustment frequency is reduced under the impedance mismatch condition subsequently; and the impedance matching precision and efficiency are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency power supply, and in particular to an impedance matching method and device of a radio frequency power supply in a plasma system. Background Art

[0002] Plasma processes are widely used in the manufacture of integrated circuits to meet the requirements of new technologies for smaller, faster, and more powerful circuits. Among them, plasma processing equipment usually uses the energy of RF power to generate plasma. In order to maximize the power output of the RF power system, the input impedance of the load must match the output impedance of the RF generator and the transmission line, and the characteristic impedance of the transmission line is usually 50Ω. However, the load impedance of the plasma chamber is affected by the RF power, pressure, and gas mixture in the plasma chamber, so real-time impedance matching is required to match the input impedance of the load with the output impedance of the RF generator and the transmission line. Unfortunately, when the current impedance matching circuit is tuned, the RF power delivered to the plasma will change, resulting in a change in the impedance of the plasma, and any change in the load impedance will increase the reflection coefficient, thereby increasing the RF power reflected back to the input end of the matching circuit.

[0003] During the impedance matching process, when the impedance matching circuit is tuned, the RF power delivered to the plasma will change, causing the impedance of the plasma to change. The change in the plasma load impedance will cause a matching time lag, resulting in poor impedance matching efficiency. In addition, the variable matching network composed of variable capacitors changes the impedance of the components through mechanical operation to achieve the purpose of impedance matching, but because the parasitic reactance of the variable matching network is ignored, the calculation error of the load impedance of the matching network circuit increases and is uncontrollable, resulting in insufficient impedance matching accuracy. Therefore, an impedance matching method that takes into account both impedance matching efficiency and accuracy is needed. Summary of the invention

[0004] The present invention provides an impedance matching method and device for a radio frequency power supply in a plasma system, which are used to solve the defects of poor efficiency and accuracy of impedance matching in the prior art.

[0005] The present invention provides an impedance matching method for a radio frequency power supply in a plasma system, comprising:

[0006] Under the impedance matching condition, in the current round of iteration, the current input impedance of the matching network is obtained, and the current reflected power of the matching network is calculated based on the current input impedance of the matching network; if the current reflected power does not reach the preset iteration stop condition, the inductance value of the first inductor is updated based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, and the inductance value of the first inductor after being updated in the previous round of iteration; if the current reflected power reaches the preset iteration stop condition, the iteration is stopped;

[0007] Under an impedance mismatch condition, adjusting the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched;

[0008] Wherein, the matching network is deployed between the RF power supply and the plasma chamber, and the matching network includes a first capacitor, a second capacitor, a first inductor and a second inductor; one end of the first capacitor and the second capacitor is connected to the RF power supply, the other end of the first capacitor and the second capacitor is connected to one end of the first inductor and the second inductor respectively, the other end of the first inductor is grounded, and the other end of the second inductor is connected to the plasma chamber.

[0009] According to an impedance matching method for a radio frequency power supply in a plasma system provided by the present invention, the updating of the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iterations and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iterations and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iterations specifically includes:

[0010] The inductance value of the first inductor is updated based on the following formula:

[0011]

[0012] Among them, L1′ new is the updated inductance value of the first inductor in the current round of iteration, L1′ old is the updated inductance value of the first inductor in the previous iteration process, ΔP reflect is the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, ΔL1 is the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, A is the adjustment coefficient, and the value of A is determined based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power.

[0013] According to an impedance matching method for a radio frequency power supply in a plasma system provided by the present invention, the capacitance values ​​of the first capacitor and the second capacitor of the matching network are adjusted until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched, specifically comprising:

[0014] Iterative adjustment step: calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber, and adjusting the stepping drive motors of the first capacitor and the second capacitor based on the optimal capacitance values ​​of the first capacitor and the second capacitor;

[0015] Control step: if the current reflection coefficient of the matching network is greater than a preset coefficient threshold, the iterative adjustment step is performed; otherwise, the input impedance of the matching network and the output impedance of the RF power supply are determined to be conjugate matched.

[0016] According to an impedance matching method for a radio frequency power supply in a plasma system provided by the present invention, the current load impedance of the plasma chamber is calculated based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, specifically comprising:

[0017] The current load impedance of the plasma chamber is calculated based on the following formula:

[0018]

[0019] Among them, RP L is the real part of the current load impedance of the plasma chamber, X PL is the imaginary part of the current load impedance of the plasma chamber, R IN is the real part of the current input impedance of the matching network, X IN is the imaginary part of the current input impedance of the matching network, Z I is the current capacitance value of the first capacitor, Z T is the current capacitance value of the second capacitor.

[0020] According to an impedance matching method for a radio frequency power supply in a plasma system provided by the present invention, the optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the current load impedance of the plasma chamber, specifically comprising:

[0021] The optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the following formula:

[0022]

[0023] Among them, Z′ L is the optimal capacitance value of the first capacitor, Z′ T is the optimal capacitance value of the second capacitor.

[0024] The present invention also provides an impedance matching device for a radio frequency power supply in a plasma system, comprising:

[0025] Control unit and matching network;

[0026] The matching network is disposed between the RF power supply and the plasma chamber, and the matching network includes a first capacitor, a second capacitor, a first inductor, and a second inductor; one end of the first capacitor and the second capacitor is connected to the RF power supply, the other end of the first capacitor and the second capacitor is connected to one end of the first inductor and the second inductor respectively, the other end of the first inductor is grounded, and the other end of the second inductor is connected to the plasma chamber; the control unit is connected to the stepping drive motor of the first capacitor and the second capacitor of the matching network;

[0027] The control unit is used to obtain the current input impedance of the matching network in the current round of iteration under impedance matching conditions, calculate the current reflected power of the matching network based on the current input impedance of the matching network, and if the current reflected power does not reach a preset iteration stop condition, update the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iteration; stop the iteration if the current reflected power reaches the preset iteration stop condition; and adjust the capacitance values ​​of the first capacitor and the second capacitor of the matching network under impedance mismatch conditions until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched.

[0028] According to an impedance matching device of a radio frequency power supply in a plasma system provided by the present invention, the updating of the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iteration specifically includes:

[0029] The inductance value of the first inductor is updated based on the following formula:

[0030]

[0031] Among them, L1′new is the updated inductance value of the first inductor in the current round of iteration, L1′ old is the updated inductance value of the first inductor in the previous iteration process, ΔP reflect is the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, ΔL1 is the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, A is the adjustment coefficient, and the value of A is determined based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power.

[0032] According to an impedance matching device of a radio frequency power supply in a plasma system provided by the present invention, the capacitance values ​​of the first capacitor and the second capacitor of the matching network are adjusted until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched, specifically comprising:

[0033] Iterative adjustment step: calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber, and adjusting the stepping drive motors of the first capacitor and the second capacitor based on the optimal capacitance values ​​of the first capacitor and the second capacitor;

[0034] Control step: if the current reflection coefficient of the matching network is greater than a preset coefficient threshold, the iterative adjustment step is performed; otherwise, the input impedance of the matching network and the output impedance of the RF power supply are determined to be conjugate matched.

[0035] According to an impedance matching device of a radio frequency power supply in a plasma system provided by the present invention, the current load impedance of the plasma chamber is calculated based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, specifically comprising:

[0036] The current load impedance of the plasma chamber is calculated based on the following formula:

[0037]

[0038] Among them, RP L is the real part of the current load impedance of the plasma chamber, X PL is the imaginary part of the current load impedance of the plasma chamber, R IN is the real part of the current input impedance of the matching network, X IN is the imaginary part of the current input impedance of the matching network, Z I is the current capacitance value of the first capacitor, ZT is the current capacitance value of the second capacitor.

[0039] According to an impedance matching device for a radio frequency power supply in a plasma system provided by the present invention, the optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the current load impedance of the plasma chamber, specifically including:

[0040] The optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the following formula:

[0041]

[0042] Among them, Z′ L is the optimal capacitance value of the first capacitor, Z′ T is the optimal capacitance value of the second capacitor.

[0043] The present invention provides an impedance matching method and device for a radio frequency power supply in a plasma system. Under impedance matching conditions, in a current round of iteration, the current input impedance of a matching network is obtained, and the current reflected power of the matching network is calculated based on the current input impedance of the matching network. If the current reflected power does not reach a preset iteration stop condition, the inductance value of the first inductor is updated based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, and the inductance value of the first inductor after being updated in the previous round of iteration; if the current reflected power reaches a preset iteration stop condition, the iteration is stopped; under impedance mismatch conditions, the capacitance values ​​of the first capacitor and the second capacitor of the matching network are adjusted until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched, and the influence of the first inductor connected in series with the first capacitor in the matching network on the reflected power of the matching network is minimized, so that the adjustment accuracy of the first capacitor and the second capacitor is improved under impedance mismatch conditions, the number of adjustments is reduced, and the impedance matching accuracy and efficiency are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a schematic flow chart of an impedance matching method of a radio frequency power supply in a plasma system provided by the present invention;

[0046] Figure 2is a schematic diagram of the structure of a matching network provided by the present invention;

[0047] Figure 3 It is a flow chart of the capacitance adjustment method provided by the present invention;

[0048] Figure 4 It is a structural schematic diagram of an impedance matching device of a radio frequency power supply in a plasma system provided by the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Figure 1 is a flow chart of an impedance matching method for a radio frequency power supply in a plasma system provided by the present invention, such as Figure 1 As shown, the method includes:

[0051] Step 110: Under the impedance matching condition, in the current round of iteration, the current input impedance of the matching network is obtained, and the current reflected power of the matching network is calculated based on the current input impedance of the matching network. If the current reflected power does not reach the preset iteration stop condition, the inductance value of the first inductor is updated based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, and the inductance value of the first inductor after being updated in the previous round of iteration; if the current reflected power reaches the preset iteration stop condition, the iteration is stopped;

[0052] Step 120, under an impedance mismatch condition, adjusting the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched;

[0053] Among them, Figure 2As shown, a matching network is deployed between the RF power supply 200 and the plasma chamber 25, and the matching network includes a first capacitor 210, a second capacitor 220, a first inductor 230 and a second inductor 240; one end of the first capacitor 210 and the second capacitor 220 are connected to the RF power supply 200, and the other end of the first capacitor 210 and the second capacitor 220 are respectively connected to one end of the first inductor 230 and the second inductor 240, the other end of the first inductor 230 is grounded, and the other end of the second inductor 240 is connected to the plasma chamber 250.

[0054] Specifically, the plasma system includes a radio frequency power supply, a matching network and a plasma chamber, and the impedance matching between the radio frequency power supply and the plasma chamber is realized by the matching network. Wherein, by adjusting the first capacitor 210 and the second capacitor 220 in the matching network, the real part and the imaginary part of the load impedance of the matching network can be adjusted respectively, so as to achieve the purpose of impedance matching. In addition, as the semiconductor process continues, the load impedance corresponding to the plasma chamber will change with factors such as plasma density, chamber temperature, and chamber pressure, so the radio frequency power supply and the plasma chamber will switch back and forth under the conditions of impedance matching and impedance mismatch. However, in the matching network, the serial inductance (i.e., the first inductance 230) of the first capacitor 210 will bring obvious errors to the capacitance adjustment of the first capacitor 210, and then the capacitance adjustment of the second capacitor 220 will also bring errors. This is because the series inductor will introduce the equivalent series resistance of the inductor and the self-inductance of the inductor, and generate parasitic reactance, which will change the impedance characteristics of the components in the matching network, and the parasitic reactance generated by the first inductor 230 connected in series with the first capacitor 210 has a greater impact, which will cause the adjustment effect of the first capacitor 210 to be less than expected, and the second capacitor 220 is adjusted based on the first capacitor 210, so the adjustment effect of the second capacitor 220 will also be less than expected. Especially at high frequencies (the frequency of RF power supplies in the semiconductor manufacturing field is usually 13.56MHz), the above effects of the first inductor 230 will become more significant, resulting in a larger capacitance adjustment error, and the adjustment error will introduce more capacitance adjustment times, reducing the accuracy and efficiency of impedance matching.

[0055] Therefore, in order to eliminate the influence of the first inductor to improve the accuracy and efficiency of impedance matching, when the parasitic reactance caused by the first inductor L1 cannot be directly measured, the optimal inductance value of the first inductor 230 can be iteratively solved with reflected power as the objective function under the condition of impedance matching by using a gradient descent method, thereby minimizing the influence of the first inductor 230 on the impedance matching task. Here, under the condition of impedance matching, the magnitude of the reflected power is mainly affected by the inductance value of the first inductor 230, so the optimal inductance value of the first inductor 230 can be iteratively solved with reflected power as the objective function, minimizing its influence on the reflected power of the matching network, so that the adjustment accuracy of the first capacitor 210 and the second capacitor 220 can be improved under the condition of impedance mismatch, and the number of adjustments can be reduced, so as to achieve the purpose of improving the accuracy and efficiency of impedance matching.

[0056] Specifically, under the impedance matching condition, the first capacitor 210, the second capacitor 220 and the second inductor 240 in the matching network are fixed, and the value of the first inductor 230 is iteratively updated to seek its optimal value. In the current round of iteration, the sensor can be used to obtain the current input impedance of the matching network, and the current reflected power of the matching network is calculated based on the current input impedance of the matching network. Here, the current reflected power of the matching network can be calculated using the following formula:

[0057]

[0058] Among them, Z IN is the current input impedance of the matching network, and Z0 is the characteristic impedance of the RF power transmission line.

[0059] If the current reflected power does not reach the preset iteration stop condition, based on the difference between the reflected power of the matching network in the previous iteration process and the current reflected power, the difference between the updated inductance value of the first inductor 230 in the previous iteration process and the inductance value before the update, and the updated inductance value of the first inductor 230 in the previous iteration process, the inductance value of the first inductor is updated, and the next iteration process is entered. Among them, the preset iteration stop condition can be that the current reflected power is less than a preset threshold. On the contrary, if the current reflected power reaches the preset iteration stop condition, the iteration is stopped to obtain an optimized matching network, so that the optimized matching network can be used for impedance matching when the impedance mismatch condition is reached next time.

[0060] In some embodiments, during the current round of iterations, the inductance value of the first inductor may be updated based on the following formula:

[0061]

[0062] Among them, L1′ new is the updated inductance value of the first inductor in the current round of iteration, L1′old is the updated inductance value of the first inductor in the previous iteration process, ΔP reflect is the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, ΔL1 is the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, A is the adjustment coefficient, and the value of A is determined based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power.

[0063] In other embodiments, when the current reflected power of the matching network is greater than the preset power value, the value of A may be updated based on the learning parameters and the difference between the reflected power of the matching network in the previous round of iterations and the current reflected power, so as to improve the solution efficiency of the first inductor 230 and take into account the system stability. For example, the value of A in the current round of iterations may be determined in the following manner:

[0064] A=A old -α×(ΔP reflect -B)

[0065] Among them, A old is the A value in the previous iteration process, α is the preset learning parameter, and B is the preset power difference value.

[0066] It should be noted that in the initial state, the RF power supply and the plasma chamber may be in an impedance mismatch condition. In order to improve the accuracy of impedance matching, the capacitance values ​​of the first capacitor and the second capacitor of the matching network can be directly adjusted until the impedance matching condition is reached, and then the inductance value of the first inductor 230 is adjusted using the method given in the above embodiment to optimize the matching network.

[0067] In some other embodiments, the inductance value of the second inductor 240 may be preset based on the operating frequency of the matching network. For example, the inductance value of the second inductor 240 may be set to 250 nH.

[0068] When the RF power supply and the plasma chamber are switched to an impedance mismatch condition, the capacitance values ​​of the first capacitor and the second capacitor of the matching network can be iteratively adjusted until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched.

[0069] In some embodiments, Figure 3 As shown, in order to further improve the efficiency of impedance matching, the following method can be used to calculate the optimal capacitance values ​​of the first capacitor 210 and the second capacitor 220 for the purpose of perfect impedance matching to adjust the first capacitor 210 and the second capacitor 220 of the matching network, thereby improving the adjustment efficiency of the first capacitor 210 and the second capacitor 220:

[0070] Iterative adjustment step 310: calculating a current load impedance of the plasma chamber based on current capacitance values ​​of the first capacitor and the second capacitor and a current input impedance of the matching network, calculating optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber, and adjusting the stepping drive motors of the first capacitor and the second capacitor based on the optimal capacitance values ​​of the first capacitor and the second capacitor;

[0071] Control step 320: If the current reflection coefficient of the matching network is greater than a preset coefficient threshold, the iterative adjustment step is performed; otherwise, the input impedance of the matching network and the output impedance of the RF power supply are determined to be conjugate matched.

[0072] Specifically, the capacitance values ​​of the first capacitor 210 and the second capacitor 220 can be iteratively adjusted until the current reflection coefficient of the matching network is less than the preset coefficient threshold. When the current reflection coefficient of the matching network is less than the preset coefficient threshold, it can be determined that the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched.

[0073] During the current round of iterations, the current load impedance of the plasma chamber 250 can be calculated based on the current capacitance values ​​of the first capacitor 210 and the second capacitor 220 and the current input impedance of the matching network, and then the optimal capacitance values ​​of the first capacitor 210 and the second capacitor 220 can be calculated based on the current load impedance of the plasma chamber 250, and the stepper drive motors of the first capacitor 210 and the second capacitor 220 can be adjusted based on the optimal capacitance values ​​of the first capacitor 210 and the second capacitor 220 to achieve a single capacitance adjustment.

[0074] In some embodiments, the current load impedance of the plasma chamber may be calculated based on the following formula:

[0075]

[0076] Among them, R PL is the real part of the current load impedance of the plasma chamber, X PL is the imaginary part of the current load impedance of the plasma chamber, R IN is the real part of the current input impedance of the matching network, X IN is the imaginary part of the current input impedance of the matching network, Z L is the current capacitance value of the first capacitor, Z T is the current capacitance value of the second capacitor.

[0077] Here, the current input impedance of the matching network is Z IN and the current load impedance Z of the plasma chamber PL It can be expressed as follows:

[0078] ZIN =R IN +jX IN , Z PL =R PL +jX PL (1)

[0079] Then there exists:

[0080] in, Z OUT The complex conjugate of OUT is the output impedance of the matching network;

[0081] Expanding the above formula (2), we get:

[0082]

[0083] Therefore, we can get:

[0084]

[0085] The current load impedance of the plasma chamber can be calculated using formula (4).

[0086] In some other embodiments, the optimal capacitance values ​​of the first capacitor 210 and the second capacitor 220 may be calculated based on the following formula:

[0087]

[0088] Among them, Z′ L is the optimal capacitance value of the first capacitor 210, Z′ T is the optimal capacitance value of the second capacitor 220 .

[0089] Here, in the case of perfect matching, the optimal capacitance values ​​of the first capacitor 210 and the second capacitor 220 can make the input impedance Z′ of the matching network IN The following conditions are met:

[0090] Z′ IN =50+j0 (5)

[0091] That is R IN =50,X IN =0.

[0092] Substituting it into formula (4) we can get:

[0093]

[0094] The optimal capacitance values ​​of the first capacitor 210 and the second capacitor 220 can be calculated using formula (6).

[0095] It should be noted that in the initial state, the RF power supply and the plasma chamber may be in an impedance mismatch condition. At this time, in order to perform impedance matching, the method given in the above embodiment can be used to repeat the iterative adjustment steps until the current reflection coefficient of the matching network is less than the preset coefficient threshold. If the condition that the current reflection coefficient is less than the preset coefficient threshold cannot be met after reaching the preset number of iterations, the first capacitor 210 and the second capacitor 220 are adjusted according to a fixed adjustment step until the current reflection coefficient of the matching network is less than the preset coefficient threshold.

[0096] In summary, an impedance matching method for a radio frequency power supply in a plasma system provided by an embodiment of the present invention obtains the current input impedance of a matching network in a current round of iteration under impedance matching conditions, calculates the current reflected power of the matching network based on the current input impedance of the matching network, and if the current reflected power does not reach a preset iteration stop condition, updates the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iteration; if the current reflected power reaches a preset iteration stop condition, stops the iteration; under impedance mismatch conditions, adjusts the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched, and minimizes the influence of the first inductor connected in series with the first capacitor in the matching network on the reflected power of the matching network, so that the adjustment accuracy of the first capacitor and the second capacitor is improved and the number of adjustments is reduced under impedance mismatch conditions, thereby improving the impedance matching accuracy and efficiency.

[0097] The impedance matching device of a radio frequency power supply in a plasma system provided by the present invention is described below. The impedance matching device of a radio frequency power supply in a plasma system described below and the impedance matching method of a radio frequency power supply in a plasma system described above can correspond to each other.

[0098] Based on any of the above embodiments, Figure 4 Schematic diagram of the structure of an impedance matching device for a radio frequency power supply in a plasma system provided by the present invention. Figure 4 As shown, the device comprises:

[0099] Control unit 400 and matching network 410;

[0100] like Figure 2 and Figure 4As shown, the matching network 410 is disposed between the RF power supply 200 and the plasma chamber 250, and the matching network 410 includes a first capacitor 210, a second capacitor 220, a first inductor 230 and a second inductor 240; one end of the first capacitor 210 and the second capacitor 220 are connected to the RF power supply 200, and the other end of the first capacitor 210 and the second capacitor 220 are respectively connected to one end of the first inductor 230 and the second inductor 240, the other end of the first inductor 230 is grounded, and the other end of the second inductor 240 is connected to the plasma chamber 250; the control unit 400 is connected to the stepping drive motor of the first capacitor 210 and the second capacitor 220 of the matching network 410;

[0101] The control unit 400 is used to obtain the current input impedance of the matching network 410 in the current round of iteration under the impedance matching condition, calculate the current reflected power of the matching network 410 based on the current input impedance of the matching network 410, and if the current reflected power does not reach the preset iteration stop condition, update the inductance value of the first inductor 230 based on the difference between the reflected power of the matching network 410 in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor 230 in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor 230 in the previous round of iteration; stop the iteration if the current reflected power reaches the preset iteration stop condition; and adjust the capacitance values ​​of the first capacitor 210 and the second capacitor 220 of the matching network 410 under the impedance mismatch condition until the input impedance of the matching network 410 and the output impedance of the RF power supply 200 are conjugate matched.

[0102] An impedance matching device for a radio frequency power supply in a plasma system provided by an embodiment of the present invention obtains the current input impedance of a matching network in a current round of iteration under impedance matching conditions, calculates the current reflected power of the matching network based on the current input impedance of the matching network, and if the current reflected power does not reach a preset iteration stop condition, updates the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iteration; stops iteration if the current reflected power reaches a preset iteration stop condition; adjusts the capacitance values ​​of a first capacitor and a second capacitor of the matching network under impedance mismatch conditions until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched, and minimizes the influence of the first inductor connected in series with the first capacitor in the matching network on the reflected power of the matching network, so that the adjustment accuracy of the first capacitor and the second capacitor is improved under impedance mismatch conditions, the number of adjustments is reduced, and the impedance matching accuracy and efficiency are improved.

[0103] Based on any of the foregoing embodiments, updating the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iterations and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iterations and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iterations specifically includes:

[0104] The inductance value of the first inductor is updated based on the following formula:

[0105]

[0106] Among them, L1′ new is the updated inductance value of the first inductor in the current round of iteration, L1′ old is the updated inductance value of the first inductor in the previous iteration process, ΔP reflect is the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, ΔL1 is the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, A is the adjustment coefficient, and the value of A is determined based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power.

[0107] Based on any of the above embodiments, adjusting the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched specifically includes:

[0108] Iterative adjustment step: calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber, and adjusting the stepping drive motors of the first capacitor and the second capacitor based on the optimal capacitance values ​​of the first capacitor and the second capacitor;

[0109] Control step: if the current reflection coefficient of the matching network is greater than a preset coefficient threshold, the iterative adjustment step is performed; otherwise, the input impedance of the matching network and the output impedance of the RF power supply are determined to be conjugate matched.

[0110] Based on any of the above embodiments, the calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network specifically includes:

[0111] The current load impedance of the plasma chamber is calculated based on the following formula:

[0112]

[0113] Among them, RP L is the real part of the current load impedance of the plasma chamber, XP L is the imaginary part of the current load impedance of the plasma chamber, R IN is the real part of the current input impedance of the matching network, X IN is the imaginary part of the current input impedance of the matching network, Z I is the current capacitance value of the first capacitor, Z T is the current capacitance value of the second capacitor.

[0114] Based on any of the above embodiments, calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber specifically includes:

[0115] The optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the following formula:

[0116]

[0117] Among them, Z′ L is the optimal capacitance value of the first capacitor, Z′ T is the optimal capacitance value of the second capacitor.

[0118] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0119] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An impedance matching method for a radio frequency power supply in a plasma system, characterized in that: include: Under the impedance matching condition, in the current round of iteration, the current input impedance of the matching network is obtained, and the current reflected power of the matching network is calculated based on the current input impedance of the matching network; if the current reflected power does not reach the preset iteration stop condition, the inductance value of the first inductor is updated based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, and the inductance value of the first inductor after being updated in the previous round of iteration; If the current reflected power reaches a preset iteration stop condition, the iteration is stopped; Under an impedance mismatch condition, adjusting the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the radio frequency power supply are conjugate matched; Wherein, the matching network is deployed between the RF power supply and the plasma chamber, and the matching network includes a first capacitor, a second capacitor, a first inductor and a second inductor; one end of the first capacitor and the second capacitor is connected to the RF power supply, the other end of the first capacitor and the second capacitor is connected to one end of the first inductor and the second inductor respectively, the other end of the first inductor is grounded, and the other end of the second inductor is connected to the plasma chamber.

2. The impedance matching method of a radio frequency power supply in a plasma system according to claim 1, characterized in that: The updating of the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iteration specifically includes: The inductance value of the first inductor is updated based on the following formula: Among them, L1′ new is the updated inductance value of the first inductor in the current round of iteration, L1′ old is the updated inductance value of the first inductor in the previous iteration process, ΔP reflect is the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, ΔL1 is the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, A is the adjustment coefficient, and the value of A is determined based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power.

3. The impedance matching method of a radio frequency power supply in a plasma system according to claim 1, characterized in that: The adjusting the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched specifically includes: Iterative adjustment step: calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber, and adjusting the stepping drive motors of the first capacitor and the second capacitor based on the optimal capacitance values ​​of the first capacitor and the second capacitor; Control step: if the current reflection coefficient of the matching network is greater than a preset coefficient threshold, the iterative adjustment step is performed; otherwise, the input impedance of the matching network and the output impedance of the RF power supply are determined to be conjugate matched.

4. The impedance matching method of a radio frequency power supply in a plasma system according to claim 3, characterized in that: The calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network specifically includes: The current load impedance of the plasma chamber is calculated based on the following formula: Among them, R PL is the real part of the current load impedance of the plasma chamber, X PL is the imaginary part of the current load impedance of the plasma chamber, R IN is the real part of the current input impedance of the matching network, X IN is the imaginary part of the current input impedance of the matching network, Z L is the current capacitance value of the first capacitor, Z T is the current capacitance value of the second capacitor.

5. The impedance matching method of a radio frequency power supply in a plasma system according to claim 4, characterized in that: The calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber specifically includes: The optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the following formula: Among them, Z′ L is the optimal capacitance value of the first capacitor, Z′ T is the optimal capacitance value of the second capacitor.

6. An impedance matching device for a radio frequency power supply in a plasma system, characterized in that: include: Control unit and matching network; The matching network is disposed between the RF power supply and the plasma chamber, and the matching network includes a first capacitor, a second capacitor, a first inductor, and a second inductor; one end of the first capacitor and the second capacitor is connected to the RF power supply, the other end of the first capacitor and the second capacitor is connected to one end of the first inductor and the second inductor respectively, the other end of the first inductor is grounded, and the other end of the second inductor is connected to the plasma chamber; the control unit is connected to the stepping drive motor of the first capacitor and the second capacitor of the matching network; The control unit is used to obtain the current input impedance of the matching network in the current round of iteration under the impedance matching condition, calculate the current reflected power of the matching network based on the current input impedance of the matching network, and if the current reflected power does not reach the preset iteration stop condition, update the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, and the inductance value of the first inductor after being updated in the previous round of iteration; If the current reflected power reaches a preset iteration stop condition, the iteration is stopped; under an impedance mismatch condition, the capacitance values ​​of the first capacitor and the second capacitor of the matching network are adjusted until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched.

7. The impedance matching device of a radio frequency power supply in a plasma system according to claim 6, characterized in that: The updating of the inductance value of the first inductor based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, the difference between the updated inductance value of the first inductor in the previous round of iteration and the inductance value before the update, and the updated inductance value of the first inductor in the previous round of iteration specifically includes: The inductance value of the first inductor is updated based on the following formula: Among them, L1′ new is the updated inductance value of the first inductor in the current round of iteration, L1′ old is the updated inductance value of the first inductor in the previous iteration process, ΔP reflect is the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power, ΔL1 is the difference between the inductance value of the first inductor after being updated in the previous round of iteration and the inductance value before being updated, A is the adjustment coefficient, and the value of A is determined based on the difference between the reflected power of the matching network in the previous round of iteration and the current reflected power.

8. The impedance matching device of a radio frequency power supply in a plasma system according to claim 6, characterized in that: The adjusting the capacitance values ​​of the first capacitor and the second capacitor of the matching network until the input impedance of the matching network and the output impedance of the RF power supply are conjugate matched specifically includes: Iterative adjustment step: calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network, calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber, and adjusting the stepping drive motors of the first capacitor and the second capacitor based on the optimal capacitance values ​​of the first capacitor and the second capacitor; Control step: if the current reflection coefficient of the matching network is greater than a preset coefficient threshold, the iterative adjustment step is performed; otherwise, the input impedance of the matching network and the output impedance of the RF power supply are determined to be conjugate matched.

9. The impedance matching device of a radio frequency power supply in a plasma system according to claim 8, characterized in that: The calculating the current load impedance of the plasma chamber based on the current capacitance values ​​of the first capacitor and the second capacitor and the current input impedance of the matching network specifically includes: The current load impedance of the plasma chamber is calculated based on the following formula: Among them, R PL is the real part of the current load impedance of the plasma chamber, X PL is the imaginary part of the current load impedance of the plasma chamber, R IN is the real part of the current input impedance of the matching network, X IN is the imaginary part of the current input impedance of the matching network, Z L is the current capacitance value of the first capacitor, Z T is the current capacitance value of the second capacitor.

10. The impedance matching device of a radio frequency power supply in a plasma system according to claim 9, characterized in that: The calculating the optimal capacitance values ​​of the first capacitor and the second capacitor based on the current load impedance of the plasma chamber specifically includes: The optimal capacitance values ​​of the first capacitor and the second capacitor are calculated based on the following formula: Among them, Z′ L is the optimal capacitance value of the first capacitor, Z′ T is the optimal capacitance value of the second capacitor.

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