Radio frequency power matcher topology network
By introducing a topology network of fixed inductors and fixed capacitors into the RF power matching unit, the problem of difficult cavity impedance matching under low gas pressure and low power conditions is solved, the matching speed and accuracy are improved, the cost is reduced and the capacitor life is extended, and the stability of the process and product quality are ensured.
Patent Information
- Application Number
- CN202511720732.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-03-03
AI Technical Summary
Existing RF power matching devices have difficulty matching cavity impedance under low pressure and low power conditions. Furthermore, adjustable capacitors are expensive and have insufficient matching speed and accuracy, which can easily lead to fluctuations in reflected power and even wafer loss.
A topology network structure combining fixed inductors and fixed capacitors with adjustable capacitors is adopted. By designing the inductance value of the fixed inductor and the capacitance value of the fixed capacitor, the matching range with a lower real part is covered, improving the matching speed and accuracy, and reducing the mechanical error of the adjustable capacitor.
It achieves rapid and accurate matching under low pressure and low power conditions, reduces component costs, extends capacitor lifespan, reduces reflected power fluctuations, and improves process quality and product yield.
Smart Images
Figure CN121602940A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an RF power matching device, and more specifically to an RF power matching device topology network. Background Technology
[0002] An RF power matcher, also known as an RF load matcher or RF matching network, is a device used to match the impedance between an RF power supply and a load. Its primary function is to ensure that the RF power supply can efficiently transfer energy to the load, providing maximum power delivery and system efficiency.
[0003] RF power matching circuits primarily achieve optimal power transfer by adjusting internal electrical components, such as inductors and capacitors, to alter the impedance matching between the power supply and the load. Their operating principle is based on the concept of impedance matching, adjusting the parameters of the matching network according to the impedance characteristics of the power supply and the load to achieve optimal power transfer and reflection loss.
[0004] Topology design is a core technology in RF power supply matching circuits. The design of the topology network is crucial to the matching speed, accuracy, and capacitor lifespan of the RF matching circuit. An optimal network topology can effectively improve the matching speed and accuracy of the RF matching circuit, while also reducing errors. Furthermore, it can lower the component costs of the topology network and effectively extend its lifespan.
[0005] like Figure 1 The diagram shows a typical theoretical circuit model of an RF matching circuit, consisting of two adjustable vacuum capacitors. RF matching circuits are used in semiconductor equipment such as etching machines, PVD, and CVD systems to match the RF power supply to the process cavity in real time, ensuring a stable power output from the RF power supply to the process cavity and achieving high-quality completion of semiconductor processes such as etching, resist removal, and coating. Since the impedance characteristics of the process cavity change due to factors such as gas pressure, plasma concentration, and gas ignition, the matching circuit's function is to adjust the impedance in real time, stabilizing the power supply's output impedance at 50Ω and reducing input power reflection.
[0006] However, in reality, when the internal environment of equipment such as etching machines is under low pressure and low power, the impedance of the cavity will decrease as the pressure and power decrease. In this case, if you want to match it to 50 ohms, then C... LOAD A larger capacitance value is needed, and by looking at the prices of adjustable capacitors, it is found that the wider the adjustable range and the higher the voltage rating, the higher the price.
[0007] On the other hand, high-end processes require faster matching speeds and smaller errors in the matching circuit. However, the capacitance value of a standard capacitor at the same position also exhibits some error. Adjustable capacitors are typically controlled by stepper motors via electrical pulses, and this step-by-step rotation means the capacitor is not adjusted continuously but in steps. Specifically, a standard adjustable capacitor at the same mechanical position will show a capacitance deviation of approximately 0.5% when rotating counterclockwise and clockwise to the same position, differing from the theoretical value by about 3-5%. This error is extremely detrimental to model-based matching algorithms. Furthermore, to improve matching speed, the motor speed is typically increased. When a high-speed motor suddenly stops, it cannot stop instantaneously; due to inertia, there is some over-adjustment, meaning there is a time delay between the capacitance value and the control signal at this step. This delay can cause the reflected power to decrease and then increase, potentially leading to wafer failure and significant losses. Therefore, to achieve both fast matching and precise control, the capacitance value per unit motor step length must be reduced. Summary of the Invention
[0008] To address the technical problems of existing RF power matching devices being unable to match the impedance of low-pressure, low-power cavities and the high cost of matching network components, this invention provides an RF power matching device topology network.
[0009] To achieve the above objectives, the present invention adopts the following technical solution: An RF power matching topology network includes adjustable capacitors. and adjustable capacitor Its special feature is: Also includes fixed inductors and fixed capacitor ; The fixed inductor One end is connected to the adjustable capacitor One end is connected, and the connected node serves as the network input terminal RFin, used to connect to the RF power supply; The fixed inductor The other end is connected to the adjustable capacitor One end is connected to the adjustable capacitor. The other end is grounded; The adjustable capacitor The other end is connected to a fixed capacitor One end is connected to the fixed capacitor. The other end serves as the network output RFout, used to connect the load.
[0010] Furthermore, the inductance value of the fixed inductor Ls satisfies the following condition: ; In the formula: Ls represents the inductance value of the fixed inductor Ls; , For radio frequency power supply frequency; Indicates adjustable capacitor The maximum capacity.
[0011] Furthermore, the fixed capacitor The capacitance value is designed according to the following formula: ; ; ; ; In the formula: The impedance of the load; Adjustable capacitor and fixed capacitor The equivalent capacitance after series connection; The imaginary unit; Adjustable capacitor The capacitance value; For fixed capacitors The capacitance value; The source resistor.
[0012] The beneficial effects of this invention are: This invention achieves the effects of covering a lower real part matching range, improving matching speed and control accuracy by connecting a suitable fixed inductor in series with the adjustable capacitor of the parallel branch and then connecting a suitable fixed capacitor in series with the adjustable capacitor of the series branch. This solves the technical problems of difficulty in matching the impedance of low-pressure and low-power cavities and high cost of matching network components. Attached Figure Description
[0013] Figure 1 This is the existing matcher topology graph; Figure 2 This is a schematic diagram of the network structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the matching range calculation in an embodiment of the present invention; Figure 4 This is a graph showing the change in capacitance value of the 400pF adjustable capacitor as the motor position in an embodiment of the present invention. Figure 5 This is a graph showing the change of the equivalent capacitance of 400pF series with 300pF in an embodiment of the present invention as a function of the motor position. Detailed Implementation
[0014] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0015] like Figure 1 The diagram shown is a typical matcher topology, where... The real part determines the matching range of the matcher. This determines the imaginary part of its matching range. Furthermore, calculations show... The larger the value, the smaller the real part of the matching range. The larger the value, the smaller the imaginary part. Based on market prices for vacuum capacitors, the larger the adjustable range, the more expensive the capacitor. For example, a 1000pF adjustable capacitor and a 1500pF adjustable capacitor with similar voltage ratings can differ in price by a factor of three.
[0016] When the system is in a matched state, the matched state holds true when viewed from any point in the circuit in both directions. Based on this theorem, the matching range of an L-type match can be calculated: ; in: ; ; Then we have: ; Other: ; Therefore, the matching range of this topology is The complex conjugate of is then: ; in, For load, The source resistor.
[0017] Observed Follow Monotonically decreasing, at a fixed value hour Follow Monotonically decreasing.
[0018] In general systems =50Ω, assuming Cload=1000pF, the calculation at a frequency of 13.56MHz yields... =2.61; When Cload maximum value = 1500pF, the calculated value is... =1.20, while under many process conditions the real part of the cavity impedance can be very small, reaching below 0.5. In this case, it is difficult to meet the requirements without using a wider range of adjustable capacitors, which will increase the production cost of the RF matching unit by a factor of two.
[0019] Therefore, this invention uses a capacitor connected in series with an inductor of a suitable size for an equivalent design: Equivalent capacitance ; To reduce the real part of the matching range, Figure 2 The value of series inductance Design in its place Near the resonant point at the maximum RF source frequency, there is: For example, when Cload is 1000pF This is approximately equal to 137nH (13.56MHz). A 137nH inductor requires only a few turns of air-core coil, making it far less expensive than using an adjustable capacitor with a wider adjustment range, and relatively easier to repair or replace. Simultaneously, the Cload capacitor matching position under low impedance is moved towards the center. Since capacitors are mechanical structures, keeping them at their maximum or minimum values for extended periods accelerates aging. Therefore, this design is beneficial to the capacitor's mechanical structure and effectively extends its lifespan.
[0020] For series branches, there is usually only one adjustable capacitor, or an adjustable capacitor connected in series with a fixed inductor. The fixed inductor usually plays the role of "shifting" the matching range.
[0021] In high-end processes, to improve process quality and product yield, faster response times are generally required for the matching circuit. However, since adjustable capacitors are typically controlled by stepper motors, according to motor control theory, increasing the motor speed to a certain extent inevitably leads to unnecessary motor displacement due to inertia. The impact of this displacement on the matching effect is significant; in severe cases, it can render the wafer in the chamber unusable, resulting in incalculable losses. Therefore, to reduce this impact without reducing the matching speed, a faster response time is required. Figure 2 Medium adjustable capacitor series fixed capacitor This method is implemented, and its value can be designed based on the load impedance. It is generally used in etching equipment for high-end processes. To ensure less contamination inside the cavity, only one process is typically performed, and the cavity impedance variation range is generally not very large. Therefore, it can be appropriately reduced. The adjustment range.
[0022] According to the principle of equivalent capacitance in series, the equivalent capacitance of two capacitors connected in series is 1. ; See Figure 2 Based on the above-described inventive concept, this embodiment provides an RF power matching topology network, including adjustable capacitors. Adjustable capacitor Fixed inductor and fixed capacitor .
[0023] Fixed inductor One end is connected to the adjustable capacitor One end is connected, and the connected node serves as the network input terminal RFin, used to connect to the RF power supply; fixed inductor The other end is connected to the adjustable capacitor One end is connected to an adjustable capacitor. The other end is grounded; adjustable capacitor The other end is connected to a fixed capacitor One end is connected to a fixed capacitor. The other end serves as the network output RFout, used to connect the load.
[0024] like Figure 4 The curve shows the change of a 400pF adjustable capacitor with the motor position. Figure 5 The curves show the equivalent capacitance changing with the motor position after a 300pF fixed capacitor is connected in series. Comparing the two curves, we find... Figure 5 The slope decreases significantly, indicating that even during rapid adjustments, errors caused by factors such as over-adjustment due to inertia are greatly reduced. Because the minimum equivalent capacitance value is reduced, this scheme can also achieve higher Q-value load impedance matching and shift the matching position of these load points towards the middle of the adjustable capacitor, which is beneficial for slowing down the aging of the adjustable capacitor. Furthermore, since it is composed of two capacitors connected in series, it can also reduce [the required capacitance] under the same load impedance. The voltage across the capacitor reduces the risk of adjustable capacitor breakdown and extends capacitor life. From a cost perspective, adjustable capacitors with higher voltage ratings are more expensive and larger, while fixed capacitors, lacking mechanical structures, are smaller, thus reducing the size of the matching circuit.
[0025] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. An RF power matching topology network, including adjustable capacitors. and adjustable capacitor ; Its features are: Also includes fixed inductors and fixed capacitor ; The fixed inductor One end is connected to the adjustable capacitor One end is connected, and the connected node serves as the network input terminal RFin, used to connect to the RF power supply; The fixed inductor The other end is connected to the adjustable capacitor One end is connected to the adjustable capacitor. The other end is grounded; The adjustable capacitor The other end is connected to a fixed capacitor One end is connected to the fixed capacitor. The other end serves as the network output RFout, used to connect the load.
2. The RF power matching topology network according to claim 1, characterized in that, The inductance value of the fixed inductor Ls satisfies the following condition: ； In the formula: Ls represents the inductance value of the fixed inductor Ls; , For radio frequency power supply frequency; Indicates adjustable capacitor The maximum capacity.
3. The RF power matching topology network according to claim 1 or 2, characterized in that, The fixed capacitor The capacitance value is designed according to the following formula: ； ； ； ； In the formula: The impedance of the load; Adjustable capacitor and fixed capacitor The equivalent capacitance after series connection; The imaginary unit; Adjustable capacitor The capacitance value; For fixed capacitors The capacitance value; The source resistor.