A radio frequency matching method, a radio frequency matcher and a computer readable storage medium

Abstract

The application discloses a radio frequency matching method, a radio frequency matching device and a storage medium, and is used for solving the problems of a matching dead zone and a long time. A load state sensor is used for detecting load impedance, an impedance adjusting network is used for adjusting input impedance, and the impedance adjusting network comprises adjustable capacitors C1 and C2; a loss function L is constructed based on a reflection coefficient Γ mode square, a gradient is calculated, and a capacitor parameter is iteratively adjusted. A main control module drives a vacuum capacitor to continuously adjust, dynamic optimization is combined with a gradient descent algorithm, discrete restrictions and a dead zone of a traditional table lookup method are eliminated, pulse mode microsecond-level rapid matching is adapted, and radio frequency overshoot is inhibited. The application improves matching precision and speed under a dynamic load (such as plasma), takes into account complex process stability, and is suitable for process procedures such as semiconductor etching.

Description

Technical Field

[0001] This invention relates to the field of radio frequency technology, and more specifically, to a radio frequency matching method, a radio frequency matching device, and a computer-readable storage medium. Background Technology

[0002] Current mainstream RF matching devices use different types of matching status sensors to determine the matching status, and then use an automatic matching algorithm to convert the matching status into the position of the adjustable capacitor to achieve automatic matching. They also use different motor control technologies or hybrid matching modes based on the identification of matching dead zones to optimize the matching process, or use a lookup table method to determine the matching combination of adjustable capacitor position and frequency.

[0003] Existing technologies have relied on matching state sensors, but these sensors deviate differently under different matching states. Furthermore, existing automatic matching algorithms all have varying degrees of matching dead zones, which can lead to failure to match or oscillations in the matcher, resulting in unsuccessful matching.

[0004] The lookup table method, which uses a certain number of discrete frequencies and vacuum capacitor positions, cannot fully meet the dynamic impedance requirements of the plasma process. The matching speed and accuracy are limited by the number of lookup table entries. When the number of lookup table entries is small, the matching speed is fast, but the accuracy cannot fully meet the dynamic impedance requirements of the plasma process, resulting in excessive reflected power. When the number of lookup table entries is large, the time and space complexity of the lookup algorithm will be very high, resulting in excessively long matching time or insufficient hardware resources to meet the algorithm requirements. Summary of the Invention

[0005] The purpose of this application is to provide a radio frequency matching method, a radio frequency matching device, and a computer-readable storage medium to solve the problems of matching dead zone and long matching time in existing radio frequency matching methods.

[0006] Firstly, a radio frequency matching method is provided.

[0007] The load impedance Z is detected by a load condition sensor. Load ;

[0008] The input impedance Z is adjusted using an impedance adjustment network. in The input impedance Z in It refers to the equivalent impedance of a system consisting of a load and an impedance adjustment network, wherein the impedance adjustment network includes at least one adjustable capacitor.

[0009] Based on the input impedance Z in Calculate the reflection coefficient Γ, reflection coefficient Γ = (Z) in -Z0) / (Z in+Z0), where Z0 is the target characteristic impedance and Z0 is the characteristic impedance of the transmission line.

[0010] The loss function L is established based on the squared magnitude of the reflection coefficient Γ:

[0011]

[0012] The variables of the loss function L include the input impedance Z used in the impedance regulation network. in The parameters of the components;

[0013] Calculate the gradient of the loss function L, and iterate the variables according to the gradient descent direction;

[0014] The impedance adjustment network adjusts the input impedance Z according to the variable values ​​after each iteration. in The parameters of the components;

[0015] The parameters characterizing the RF matching state are detected by the matching state sensor after each iteration. It is determined whether the reflection coefficient has reached the set judgment condition. If the set judgment condition is reached, the iteration stops, the current variable value is obtained, and the parameters of the components in the impedance adjustment network are adjusted accordingly. If the set judgment condition is not reached, the iteration continues.

[0016] The impedance adjustment network includes an adjustable capacitor C1 and an adjustable capacitor C2. The adjustable capacitor C2 is connected in series between the RF input terminal and the RF output terminal. One end of the adjustable capacitor C1 is grounded, and the other end is connected to the RF input terminal.

[0017] The iterative function for the adjustable capacitor C1 is:

[0018]

[0019] in Let γ be the capacitance value of the adjustable capacitor C1 after K iterations, and γ be the iteration step size. The gradient of the loss function with respect to the adjustable capacitor C1;

[0020] The iterative function for the adjustable capacitor C2 is:

[0021]

[0022] in Let γ be the capacitance value of the adjustable capacitor C2 after K iterations, and γ be the iteration step size. The gradient of the loss function with respect to the adjustable capacitor C2 is given. Before the iteration, the adjustable capacitors C1 and C2 are given initial values ​​respectively.

[0023] Furthermore,

[0024]

[0025]

[0026]

[0027] Where ω is the angular frequency, and C1 and C2 are the capacitance values ​​of adjustable capacitors C1 and C2, respectively:

[0028]

[0029]

[0030] Where Γ * Let Z0 be the complex conjugate of Γ, and Im() denotes taking the imaginary part of the complex number, Z0 = 50Ω.

[0031] Furthermore, the load is a dynamically changing radio frequency plasma cavity.

[0032] Furthermore, both the adjustable capacitor C1 and the adjustable capacitor C2 are adjustable capacitors, and the capacitance value can be continuously adjusted by changing the electrode spacing or effective area through the driving device.

[0033] Furthermore, the impedance adjustment network also includes a main control module, which acquires the load impedance Z. Load Using the parameters of the matching state sensor as input, the loss function L is iterated, and the operating parameters of the drive device are calculated based on the results of each iteration to automatically adjust the value of the adjustable capacitor.

[0034] Furthermore, the matching state sensor detects the amplitude and phase errors of the reflected wave at the RF input port.

[0035] Secondly, an RF matching device is provided, including a load state sensor, a matching state sensor, an adjustable capacitor C1, an adjustable capacitor C2, a driving device, and a main control module. The load state sensor is used to detect the load impedance Z. Load The matching state sensor is used to detect parameters characterizing the radio frequency matching state, and the main control module acquires the load impedance Z. Load With the parameters of the matching state sensor as input, the main control module adjusts the plate spacing or effective area of ​​the adjustable capacitors C1 and C2 through the driving device to iterate the capacitance value. The iteration method adopts the radio frequency matching method described in the first aspect.

[0036] Thirdly, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described in the first aspect.

[0037] Compared with existing technologies, the advantages of this invention are as follows: By introducing a gradient descent algorithm and real-time dynamic impedance adjustment, the matching performance of the RF system is improved. The gradient descent algorithm can continuously optimize the capacitance value, avoid discrete entry limitations, adapt to high-frequency impedance fluctuations (such as transient plasma density changes), break through the discrete entry limitations of the traditional lookup table method, and solve the matching dead zone and oscillation problems under dynamic loads (such as pulsed plasma). Combined with the main control module and high-precision electromechanical drive, continuous adaptive adjustment of the capacitance value is achieved, effectively suppressing RF overshoot. It takes into account stability and reliability under complex process environments, providing an efficient and low-power matching solution for semiconductor etching scenarios. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 A schematic diagram of the structure of a radio frequency matching device provided in this application embodiment.

[0040] Figure 2 The iterative flowchart of the variables in the radio frequency matching method provided in the embodiments of this application is shown. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art. The words "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are only used to distinguish different components. The words "comprising" or "including," etc., mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but do not exclude other elements or objects. The words "connected," "coupled," or "connected," etc., are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0042] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application. Furthermore, the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0043] The structure of a radio frequency matching device provided in this application embodiment is as follows: Figure 1 As shown, it includes a load status sensor, a matching status sensor, an impedance adjustment network, a drive unit, and a main control module.

[0044] The load condition sensor is used to detect the load impedance Z. Load In this embodiment, the load is a radio frequency plasma cavity. In low-frequency to high-frequency (MHz level) radio frequency systems, the voltage and current signals at the radio frequency input can be directly measured, and the impedance can be calculated through amplitude and phase difference, such as using a high-frequency voltage probe, Rogowski coil, or current transformer. In high-power radio frequency systems, a directional coupler is used to separate the forward and reflected waves, and the reflection coefficient (Γ) is calculated through power ratio and phase difference, thereby deriving the impedance. A dual-channel power meter is used in conjunction with the directional coupler to calculate the standing wave ratio. Impedance sensors can also be used, such as a radio frequency impedance analyzer to directly measure complex impedance, or a resonant impedance probe to find the resonant frequency by frequency sweeping and derive the load impedance.

[0045] Matching state sensors are used to detect parameters characterizing the RF matching state. Matching state sensors can employ directional couplers in conjunction with amplitude / phase detectors. The directional coupler separates the incident and reflected waves, calculates the reflection coefficient using the amplitude ratio and phase difference of the two signals, measures the power ratio (i.e., return loss) of the incident and reflected waves using a diode detector or logarithmic amplifier, and compares the phase difference between the incident and reflected waves using a phase detector (such as a multiplier or mixer). Alternatively, a high-speed ADC can sample the incident and reflected waves, extracting the amplitude ratio and phase difference using FFT or correlation algorithms. The error signal can be converted into a digital control signal to drive the matching network (e.g., adjusting the capacitor / inductor of a stepper motor). Standing wave ratio (VSWR) sensors indirectly reflect amplitude error by measuring the VSWR; combined with a phase detection circuit (such as a delay line phase detector), phase error can be obtained simultaneously.

[0046] Impedance adjustment networks match the plasma cavity impedance to the source impedance (typically 50Ω) to maximize power transfer and reduce reflections. Commonly used matching networks include L-type networks, consisting of two reactive elements (inductor L and capacitor C), with topologies of series-parallel (one element in series, the other in parallel) and parallel-series (one element in parallel, the other in series). T-type networks add a series or parallel element to the L-type, forming a "T" structure, providing greater degrees of freedom and expanding the matching range through three reactive elements. π-type networks are similar to T-type networks but use two parallel elements and one series element (such as CLC or LCL), complementing the T-type and suitable for high-impedance to low-impedance transformations. Hybrid matching networks combine passive elements (fixed L / C) and active elements (variable capacitor / inductor); the passive network provides basic matching, while the active elements fine-tune to adapt to dynamic changes.

[0047] The impedance adjustment network in this embodiment can employ two adjustable capacitors, namely adjustable capacitor C1 and adjustable capacitor C2. Adjustable capacitor C2 is connected in series between the RF input and RF output terminals. One end of adjustable capacitor C1 is grounded, and the other end is connected to the RF input terminal. Both adjustable capacitors C1 and C2 are adjustable capacitors, and their capacitance values ​​are continuously adjusted by a driving device, such as a motor, changing the electrode spacing or effective area. The impedance adjustment network also includes a main control module, which automatically adjusts the capacitance values ​​of the adjustable capacitors based on the operating parameters of the driving device.

[0048] The working principle of the RF matching device in the embodiments of this application is as follows: Figure 2 As shown.

[0049] The input impedance Z is adjusted using an impedance adjustment network. in Input impedance Z in This refers to the equivalent impedance of a system consisting of a load and an impedance regulation network, based on the input impedance Z. in Calculate the reflection coefficient Γ, reflection coefficient Γ = (Z) in -Z0) / (Z in +Z0), where Z0 is the target characteristic impedance, which is the characteristic impedance of the transmission line, and the value of Z0 is usually 50Ω.

[0050] The loss function L is established based on the squared magnitude of the reflection coefficient Γ:

[0051]

[0052] The variables of the loss function L include the input impedance Z used in the impedance regulation network. in In this embodiment, the parameters of the components are the values ​​of adjustable capacitor C1 and adjustable capacitor C2, and the constraints are:

[0053]

[0054]

[0055]

[0056] Where ω is the angular frequency, and C1 and C2 are the capacitance values ​​of adjustable capacitors C1 and C2, respectively.

[0057] The main control module acquires the load impedance Z. Load The system uses the parameters of the matching state sensor as input for optimization, iterates over the loss function L, and automatically adjusts the adjustable capacitor value based on the operating parameters of the drive unit according to the results of each iteration. The specific iterative method is as follows:

[0058] Calculate the gradient of the loss function L, and iterate the variables according to the gradient descent direction. The gradient is a vector of the first-order partial derivatives of the loss function with respect to the variables, pointing in the direction in which the loss function grows fastest at the current point. The gradient descent direction, i.e., the negative gradient direction, is the direction in which the loss function decreases fastest, guiding parameter updates to minimize the loss.

[0059] The impedance adjustment network adjusts the input impedance Z according to the variable values ​​after each iteration. in The parameters of the components. For example, after iteration, the variable values ​​C1=1F and C2=2.5F. The main control module calculates the operating parameters of the drive device and adjusts the values ​​of adjustable capacitors C1 and C2 to 1F and 2.5F respectively.

[0060] The matching state sensor detects the parameters used to characterize the RF matching state after each iteration to determine whether the reflection coefficient meets the set judgment condition, such as reflection coefficient modulus |Γ| < 0.05 (corresponding to VSWR < 1.1). If the set judgment condition is met, the iteration stops, the current variable value is obtained, and the main control module adjusts the plate spacing or effective area of ​​adjustable capacitors C1 and C2 through the drive device to make the capacitance value the same as or approximately the current variable value. If the set judgment condition is not met, the iteration continues.

[0061] The iterative function for the adjustable capacitor C1 is:

[0062]

[0063] in Let γ be the capacitance value of the adjustable capacitor C1 after K iterations, and γ be the iteration step size. The gradient of the loss function with respect to the adjustable capacitor C1;

[0064] The iterative function for the adjustable capacitor C2 is:

[0065]

[0066] in Let γ be the capacitance value of the adjustable capacitor C2 after K iterations, and γ be the iteration step size. To define the gradient of the loss function with respect to the adjustable capacitor C2, initial values ​​are assigned to the adjustable capacitors C1 and C2 before iteration, such as C1 = 1 pF and C2 = 1 pF. The iteration step size can be set empirically, typically between 0.01 and 0.1. If the gradient magnitude is large (e.g., reflection coefficient |Γ| > 0.5), it can be appropriately reduced to γ ​​= 0.001 to avoid oscillation; conversely, if the gradient is small, it can be increased to γ ​​= 0.05 to accelerate convergence.

[0067] The calculation methods for ∇1 and ∇2 are as follows:

[0068] 1. Calculate the derivative of the reflection coefficient:

[0069]

[0070] 2. Calculate the derivative of the input impedance.

[0071] Differentiate with respect to C1:

[0072]

[0073] Differentiate with respect to C2:

[0074]

[0075] 3. According to the rules of complex derivatives:

[0076]

[0077]

[0078] Using the chain rule, we can deduce:

[0079]

[0080]

[0081] Where Γ * Let Z0 be the complex conjugate of Γ, Im() denotes taking the imaginary part of the complex number, Re() denotes taking the imaginary part of the complex number, and Z0 = 50Ω.

[0082] The main control module iterates over the loss function L, calculating the operating parameters of the drive unit based on the results of each iteration and automatically adjusting the value of the adjustable capacitor. The main control module can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0083] The RF matching device and matching method of this invention improve the matching performance of RF systems by introducing a gradient descent algorithm and real-time dynamic impedance adjustment. The gradient descent algorithm can continuously optimize the capacitance value, avoiding discrete entry limitations and adapting to high-frequency impedance fluctuations (such as transient plasma density changes). It overcomes the discrete entry limitations of traditional lookup table methods and solves the matching dead zone and oscillation problems under dynamic loads (such as pulsed plasma). Combined with a main control module and high-precision electromechanical drive, it achieves continuous adaptive adjustment of the capacitance value while supporting microsecond-level fast response, adapting to 10μs-level short pulse scenarios, and effectively suppressing RF overshoot. It balances stability and reliability under complex process environments, providing an efficient and low-power matching solution for semiconductor etching scenarios.

[0084] Based on the above embodiments, this application provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the above-described radio frequency matching method.

[0085] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0086] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0087] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0088] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0089] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A radio frequency matching method, characterized in that, detecting the load impedance Z by means of a load state sensor Load ; The input impedance Z is regulated by an impedance regulating network in , said input impedance Z in refers to the equivalent impedance of a system consisting of a load and an impedance regulating network, said impedance regulating network comprising at least one adjustable capacitor; According to the input impedance Z in The reflection coefficient Γ is calculated, Γ = (Z in -Z0) / (Z in + Z0), where Z0 is the target characteristic impedance, which is the characteristic impedance of the transmission line. a loss function L is established according to the modulus square of the reflection coefficient Γ: The variables of the loss function L include parameters of components in the impedance adjustment network for adjusting the input impedance Z in ​ the gradient of the loss function L is calculated, and the variable is iterated according to the gradient descent direction; The impedance adjusting network adjusts the parameter of the component corresponding to the variable value after each iteration for adjusting the input impedance Z in . a parameter for representing the radio frequency matching state after each iteration is detected by a matching state sensor, whether the reflection coefficient reaches a set judgment condition is judged, if the set judgment condition is reached, the iteration is stopped, the current variable value is obtained, the parameters of the components in the impedance adjustment network are adjusted, if the set judgment condition is not reached, the iteration is continued; the impedance adjustment network comprises an adjustable capacitor C1 and an adjustable capacitor C2, the adjustable capacitor C2 is connected in series between the radio frequency input end and the radio frequency output end, one end of the adjustable capacitor C1 is grounded, and the other end is connected to the radio frequency input end; the iteration function of the adjustable capacitor C1 is: wherein is the capacitance value of the adjustable capacitor C1 after K iterations, and γ is the iteration step size, is the gradient of the loss function with respect to the adjustable capacitor C1; the iteration function of the adjustable capacitor C2 is: wherein is the capacitance value of the adjustable capacitor C2 after K iterations, and γ is the iteration step size, is the gradient of the loss function with respect to the adjustable capacitor C2, and the adjustable capacitors C1 and C2 are respectively assigned initial values before the iteration is performed. wherein: wherein ω is the angular frequency, C1 and C2 are the capacitance values of the adjustable capacitor C1 and the adjustable capacitor C2, and then: wherein Γ* is the complex conjugate of Γ, Im() represents taking the imaginary part of a complex number, and Z0=50Ω.

2. The radio frequency matching method of claim 1, wherein, The load is a dynamic radio frequency plasma cavity.

3. The radio frequency matching method of claim 2, wherein, The adjustable capacitor C1 and the adjustable capacitor C2 are both adjustable vacuum capacitors, and the continuous adjustment of the capacitance values is realized by changing the plate spacing or effective area through a driving device.

4. The radio frequency matching method of claim 3, wherein, The impedance adjusting network further comprises a master control module, which collects the load impedance Z Load and the matching state sensor parameters as inputs, iterates the loss function L, and calculates the operation parameter of the driving device to automatically adjust the adjustable capacitance value.

5. The radio frequency matching method of claim 4, wherein, The matching state sensor detects the reflection wave amplitude error and phase error of the radio frequency input port.

6. A radio frequency matcher characterized by: The load state sensor is used for detecting the load impedance Z Load The matching state sensor is used for detecting the parameter representing the radio frequency matching state Load The main control module collects the load impedance Z and the matching state sensor parameter as input, and adjusts the plate distance or effective area of the adjustable capacitor C1 and the adjustable capacitor C2 to iterate the capacitance value through the driving device, and the iteration method adopts the radio frequency matching method as claimed in any one of claims 1-5.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The computer program is executed by a processor to realize the steps of the method of any one of claims 1-5.

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