A voltage control method for lower radio frequency power supply and semiconductor process equipment

Abstract

The present application discloses a voltage control method for a lower RF power supply and a semiconductor process device, which pre-acquires the voltage setting value of the lower RF power supply fed to the electrostatic chuck, and corrects the voltage setting value according to a preset voltage correction strategy to obtain a target voltage value; obtains a first voltage signal output by a RF voltage sensor connected to the electrostatic chuck, and obtains a second voltage signal theoretically input by the RF voltage sensor based on the first voltage signal and a sensor conversion coefficient that characterizes the average input-output correspondence of the RF voltage sensor; compares the target voltage value and the second voltage signal, and adjusts the output power of the lower RF power supply according to the comparison result so that the second voltage signal is equal to the target voltage value. It can be seen that the present application corrects the voltage setting value of the lower RF power supply so that when the lower RF power supply reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage setting value, thereby improving the voltage control accuracy of the lower RF power supply.

Description

Technical Field

[0001] This application relates to the field of semiconductor processes, and particularly to a method for controlling the voltage of a lower radio frequency power supply and a semiconductor process equipment. Background Art

[0002] The structure of a typical ICP (Inductively Coupled Plasma) etcher is as Figure 1 shown. The ICP etcher includes: an upper radio frequency power supply 1, a matcher 2, an inductively coupled coil 3, a reaction chamber 4, an electrostatic chuck 6 for adsorbing a wafer 5, a spectrometer 7, a matcher 8, a lower radio frequency power supply 9, a radio frequency voltage sensor 10, and a dielectric window 11; wherein, the input end of the radio frequency voltage sensor 10 is connected to the electrostatic chuck 6, and the output end of the radio frequency voltage sensor 10 is connected to the feedback control port of the lower radio frequency power supply 9.

[0003] When the ICP etcher is working, the upper radio frequency power supply 1 is used to control the generation of inductive coupling plasma in the reaction chamber 4, and the lower radio frequency power supply 9 is used to generate a bias voltage to control the energy of the plasma in the reaction chamber 4. The lower radio frequency power supply 9 can work in a power mode or a voltage mode. In the power mode, the output power of the lower radio frequency power supply 9 is controlled to be constant, and in the voltage mode, the output voltage of the lower radio frequency power supply 9 is controlled to be constant.

[0004] When the lower radio frequency power supply 9 works in the voltage mode, it is necessary for the radio frequency voltage sensor 10 to collect the voltage signal of the electrostatic chuck 6 and feedback it to the lower radio frequency power supply 9 for output control. The specific control principle is: obtain the output voltage signal Vout of the radio frequency voltage sensor 10, and multiply the output voltage signal Vout by the sensor conversion coefficient Gain_av to obtain the input voltage signal Vin of the radio frequency voltage sensor 10 = Vout * Gain_av. Compare the voltage set value Vsetpoint of the lower radio frequency power supply 9 and the input voltage signal Vin. If Vsetpoint < Vout * Gain_av, the lower radio frequency power supply 9 reduces the power output; otherwise, the lower radio frequency power supply 9 increases the power output so that the lower radio frequency power supply 9 reaches a steady state: Vsetpoint = Vout * Gain_av. Here, Gain_av is the average value of the sensor conversion coefficient Gain of the radio frequency voltage sensor 10 within a certain power range, and Gain is the ratio Vin / Vout of the input to the output of the radio frequency voltage sensor 10.

[0005] However, the input and output of the RF voltage sensor are actually in a nonlinear relationship. If the input and output of the RF voltage sensor are directly regarded as a proportional relationship, there will be a certain deviation between the calculated input voltage signal of the RF voltage sensor and the actual input voltage signal of the RF voltage sensor. As a result, when the lower RF power supply reaches a steady state, there will be a certain deviation between the actual output voltage of the lower RF power supply and its voltage setting value, which will further reduce the voltage control accuracy of the lower RF power supply. Summary of the Invention

[0006] The purpose of this application is to provide a voltage control method for a lower RF power supply and a semiconductor process equipment, which can correct the voltage setting value of the lower RF power supply so that when the lower RF power supply reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage setting value of the lower RF power supply, thereby improving the voltage control accuracy of the lower RF power supply.

[0007] To solve the above technical problems, the present application provides a voltage control method for a radio frequency power supply, comprising:

[0008] A voltage setting value of a lower RF power supply feeding the electrostatic chuck is obtained in advance, and the voltage setting value is corrected according to a preset voltage correction strategy to obtain a target voltage value; wherein the correction purpose of the preset voltage correction strategy is to ensure that the actual output voltage of the lower RF power supply is equal to the voltage setting value when the lower RF power supply reaches a steady state;

[0009] Obtaining a first voltage signal output by a radio frequency voltage sensor connected to the electrostatic chuck, and obtaining a second voltage signal theoretically input by the radio frequency voltage sensor based on the first voltage signal and a sensor conversion coefficient representing an average input-output correspondence relationship of the radio frequency voltage sensor;

[0010] The target voltage value and the second voltage signal are compared, and the output power of the lower RF power supply is adjusted according to the comparison result so that the second voltage signal is equal to the target voltage value.

[0011] Optionally, the correcting the voltage setting value according to a preset voltage correction strategy to obtain a target voltage value includes:

[0012] Using the voltage setting value as the input voltage signal of the radio frequency voltage sensor, and obtaining the output voltage signal of the radio frequency voltage sensor according to a preset actual input-output correspondence relationship of the radio frequency voltage sensor;

[0013] A third voltage signal input by the radio frequency voltage sensor is obtained according to the output voltage signal and the sensor conversion coefficient, so as to use the third voltage signal as the target voltage value obtained after the voltage setting value is corrected.

[0014] Optionally, the process of presetting the actual input-output correspondence of the radio frequency voltage sensor includes:

[0015] Determining voltage transfer functions corresponding to different circuits in the radio frequency voltage sensor;

[0016] Combining the voltage transfer functions corresponding to the different circuits to obtain a total voltage transfer function representing the actual input-output correspondence of the radio frequency voltage sensor;

[0017] An explicit relational expression of the total voltage transfer function is determined based on the input and output sample data of the radio frequency voltage sensor.

[0018] Optionally, the radio frequency voltage sensor includes a voltage divider circuit, a detection circuit and a linear amplifier circuit in sequence;

[0019] Then, determining the voltage transfer functions corresponding to different circuits in the radio frequency voltage sensor includes:

[0020] Determine the voltage transfer function corresponding to the voltage divider circuit as y0=f1(x)=k1*x; wherein k1 is a first coefficient; x is the RF voltage signal input by the RF voltage sensor, which serves as the input voltage signal of the voltage divider circuit; y0 is the output voltage signal of the voltage divider circuit, which serves as the input voltage signal of the detection circuit;

[0021] Determine the voltage transfer function corresponding to the detection circuit as y1=f2(y0); wherein y1 is the output voltage signal of the detection circuit, which serves as the input voltage signal of the linear amplifier circuit;

[0022] Determine that the voltage transfer function corresponding to the linear amplification circuit is y2=f3(y1)=k2*y1+b1; wherein k2 is the second coefficient; b1 is the first constant; and y2 is the output voltage signal of the linear amplification circuit, which serves as the output voltage signal of the radio frequency voltage sensor.

[0023] Optionally, the input voltage signal of the detection circuit is output after being regulated by an internal diode;

[0024] Then, determining that the voltage transfer function corresponding to the detection circuit is y1=f2(y0) includes:

[0025] Simulating the detection circuit to obtain a simulation curve representing a corresponding relationship between an input voltage signal of the detection circuit and a voltage drop signal across the diode;

[0026] The simulation curve is fitted with data according to a logarithmic function to obtain a fitting relationship y3=k3*ln(x)+b2; wherein y3 is the voltage drop signal on the diode; k3 is the third coefficient; and b2 is the second constant;

[0027] Based on the fitting relationship, the voltage transfer function y1=f2(y0)=y0-k3*ln(x)-b2 corresponding to the detection circuit is obtained.

[0028] Optionally, combining the voltage transfer functions corresponding to the different circuits to obtain a total voltage transfer function representing the actual input-output correspondence of the radio frequency voltage sensor includes:

[0029] The voltage transfer functions corresponding to the voltage divider circuit, the detection circuit, and the linear amplification circuit are combined to obtain a total voltage transfer function F(x)=k4*x+k5*ln(x)+b3, which represents the actual input-output correspondence of the RF voltage sensor; wherein k4 is the fourth coefficient; k5 is the fifth coefficient; and b3 is the third constant.

[0030] Optionally, determining the explicit relationship of the total voltage transfer function based on the input and output sample data of the radio frequency voltage sensor includes:

[0031] The input and output sample data of the radio frequency voltage sensor are subjected to curve fitting using the least square method to obtain a clear relationship of the total voltage transfer function.

[0032] Optionally, the voltage control method further includes:

[0033] The total voltage transfer function is solved according to the current output voltage signal of the radio frequency voltage sensor to obtain the current theoretical input voltage signal of the radio frequency voltage sensor.

[0034] Optionally, the total voltage transfer function is F(x)=k4*x+k5*ln(x)+b3; wherein x is the RF voltage signal input by the RF voltage sensor; k4 is the fourth coefficient; k5 is the fifth coefficient; and b3 is the third constant;

[0035] Solving the total voltage transfer function according to the current output voltage signal of the RF voltage sensor to obtain the current theoretical input voltage signal of the RF voltage sensor includes:

[0036] The total voltage transfer function is simplified to obtain a simplified transfer function F(x)=k4*x+b3; wherein x0=(A-b3) / k4, and n=0; x0 is the initial setting value of the voltage signal currently input by the RF voltage sensor; A is the current output voltage signal of the RF voltage sensor; b3 and k4 are both within the corresponding experimentally measured value ranges; and n is the number of iterations.

[0037] According to the error function f(x)=F(x n )-A calculates the error f(x) and determines the first iteration end condition |f(x)|<ε or the second iteration end condition n>n end Is it true? Where || is the absolute value; ε is the preset reading error threshold; n end is the preset maximum number of iterations;

[0038] If the first iteration end condition and the second iteration end condition are both not met, then according to x n+1 =x n -F(x n ) / F(x n )', n = n + 1 to perform parameter iteration and return to execute according to the error function f(x) = F(x n )-A step of calculating the error f(x); where F(x n )' is F(x n )’s derivative;

[0039] If one of the first iteration end condition and the second iteration end condition is met, then x n As the current theoretical input voltage signal of the RF voltage sensor.

[0040] To solve the above technical problems, the present application also provides a semiconductor process equipment, including:

[0041] electrostatic chuck;

[0042] a radio frequency voltage sensor connected to the electrostatic chuck;

[0043] a lower radio frequency power supply feeding power to the electrostatic chuck;

[0044] A controller provided in the lower RF power supply and connected to the RF voltage sensor is used to implement the steps of any of the above-mentioned voltage control methods for the lower RF power supply when executing a computer program stored in the controller.

[0045] The present application provides a voltage control method for a lower RF power supply, which pre-acquires a voltage set value of the lower RF power supply fed to an electrostatic chuck, and corrects the voltage set value according to a preset voltage correction strategy to obtain a target voltage value; the correction purpose of the preset voltage correction strategy is to ensure that the actual output voltage of the lower RF power supply when the lower RF power supply reaches a steady state is equal to the voltage set value; obtain a first voltage signal output by an RF voltage sensor connected to the electrostatic chuck, and obtain a second voltage signal theoretically input by the RF voltage sensor based on the first voltage signal and a sensor conversion coefficient representing the average input-output correspondence of the RF voltage sensor; compare the target voltage value with the second voltage signal, and adjust the output power of the lower RF power supply based on the comparison result so that the second voltage signal is equal to the target voltage value. It can be seen that the present application can correct the voltage set value of the lower RF power supply so that when the lower RF power supply reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage set value of the lower RF power supply, thereby improving the voltage control accuracy of the lower RF power supply.

[0046] The present application also provides a semiconductor process equipment having the same beneficial effects as the above voltage control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in this application 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 only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0048] Figure 1 It is a structural diagram of an ICP etcher in the prior art;

[0049] Figure 2 A flowchart of a voltage control method for a lower RF power supply provided in an embodiment of the present application;

[0050] Figure 3 A working logic diagram of a voltage control method for a radio frequency power supply provided in an embodiment of the present application;

[0051] Figure 4 A schematic diagram of voltage transfer functions of different circuits in a radio frequency voltage sensor provided in an embodiment of the present application;

[0052] Figure 5 A typical circuit diagram of a detection circuit provided in an embodiment of the present application;

[0053] Figure 6 A diagram showing the corresponding relationship between an input voltage signal of a detection circuit and a voltage drop signal across a diode provided in an embodiment of the present application;

[0054] Figure 7 A curve chart of the same data provided in the embodiment of the present application for fitting the independent variable and the dependent variable;

[0055] Figure 8 A flowchart of a Newton iteration method for solving approximate roots is provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] The core of this application is to provide a voltage control method for a lower RF power supply and a semiconductor process equipment, which can correct the voltage setting value of the lower RF power supply so that when the lower RF power supply reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage setting value of the lower RF power supply, thereby improving the voltage control accuracy of the lower RF power supply.

[0057] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0058] Please refer to Figure 1 , Figure 1 Schematic diagram of a voltage control method for a radio frequency power supply provided in an embodiment of the present application. Figure 1 As shown, the scene includes: an upper RF power supply 1, a matching device 2, an inductive coupling coil 3, a reaction chamber 4, an electrostatic chuck 6 for adsorbing a wafer 5, a spectrometer 7, a matching device 8, a lower RF power supply 9, an RF voltage sensor 10, and a dielectric window 11. It should be noted that the lower RF power supply mentioned in this application operates in voltage mode, which controls the output voltage of the lower RF power supply to be constant.

[0059] Based on the above application scenario architecture, the present application embodiment provides a voltage control method for a radio frequency power supply. Figure 2 , Figure 2 This is a flow chart of a voltage control method for a radio frequency power supply provided in an embodiment of the present application. Figure 2 The method in can be Figure 1 The controller in the lower RF power supply executes, such as Figure 2 As shown, the method includes the following steps:

[0060] Step S101: obtaining in advance a voltage setting value of a lower radio frequency power supply feeding into an electrostatic chuck, and correcting the voltage setting value according to a preset voltage correction strategy to obtain a target voltage value.

[0061] In the embodiment of the present application, the correction purpose of the preset voltage correction strategy is: when the lower RF power source reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage setting value of the lower RF power source.

[0062] In a specific application, the present application obtains the voltage set value of the lower RF power supply in advance (the voltage set value is stored in a register of the lower RF power supply) and corrects the voltage set value of the lower RF power supply according to a preset voltage correction strategy to obtain a target voltage value. It is understood that the uncorrected voltage set value of the lower RF power supply is the voltage value desired to be achieved on the electrostatic chuck, while the corrected target voltage value of the lower RF power supply is the voltage value achieved on the electrostatic chuck by the lower RF power supply during the voltage control process. The ultimate goal is to achieve: when the lower RF power supply reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage set value of the lower RF power supply.

[0063] Step S102: obtaining a first voltage signal output by a radio frequency voltage sensor connected to the electrostatic chuck, and obtaining a second voltage signal theoretically input by the radio frequency voltage sensor based on the first voltage signal and a sensor conversion coefficient.

[0064] In the embodiment of the present application, the sensor conversion coefficient represents the average input-output correspondence of the RF voltage sensor. Specifically, the sensor conversion coefficient can be represented by Gain_av, where Gain_av is the average value of the sensor conversion coefficient Gain of the RF voltage sensor within a certain power range (e.g., 10-1500W). Gain is the ratio of the input Vin of the RF voltage sensor to the output Vout of the RF voltage sensor, that is, Gain = Vin / Vout.

[0065] In a specific application, the present application obtains a voltage signal (referred to as a first voltage signal) output by a radio frequency voltage sensor connected to an electrostatic chuck, and multiplies the first voltage signal output by the radio frequency voltage sensor by the sensor conversion coefficient Gain_av to calculate the voltage signal theoretically input by the radio frequency voltage sensor (referred to as a second voltage signal).

[0066] Step S103: comparing the target voltage value and the second voltage signal, and adjusting the output power of the RF power supply according to the comparison result so that the second voltage signal is equal to the target voltage value.

[0067] In a specific application, the present application compares the corrected target voltage value of the lower RF power supply and the second voltage signal input by the RF voltage sensor. If the corrected target voltage value of the lower RF power supply is greater than the second voltage signal input by the RF voltage sensor, the output power of the lower RF power supply is increased; if the corrected target voltage value of the lower RF power supply is less than the second voltage signal input by the RF voltage sensor, the output power of the lower RF power supply is reduced. The ultimate adjustment goal is to make the second voltage signal input by the RF voltage sensor equal to the corrected target voltage value of the lower RF power supply, that is, the lower RF power supply reaches a steady state.

[0068] It can be seen that when the RF power supply works in voltage mode, the working logic of the RF power supply is voltage closed-loop control logic, such as Figure 3 As shown, specifically, the actual voltage value on the electrostatic chuck is detected by the RF voltage sensor, and the detected actual voltage value on the electrostatic chuck is fed back to the controller in the lower RF power supply. The controller in the lower RF power supply performs voltage closed-loop control according to the above voltage control method.

[0069] The voltage control method of the lower RF power supply provided in the present application can correct the voltage setting value of the lower RF power supply so that when the lower RF power supply reaches a steady state, the actual voltage value on the electrostatic chuck is equal to the uncorrected voltage setting value of the lower RF power supply, thereby improving the voltage control accuracy of the lower RF power supply.

[0070] Based on the above embodiment:

[0071] As an optional embodiment, the voltage setting value is corrected according to a preset voltage correction strategy to obtain a target voltage value, including:

[0072] The voltage setting value is used as the input voltage signal of the radio frequency voltage sensor, and the output voltage signal of the radio frequency voltage sensor is obtained according to the preset actual input-output correspondence relationship of the radio frequency voltage sensor;

[0073] A third voltage signal input by the radio frequency voltage sensor is obtained according to the output voltage signal and the sensor conversion coefficient, so as to use the third voltage signal as a target voltage value obtained after the voltage setting value is corrected.

[0074] In a specific application, the voltage setting value of the lower RF power supply is the voltage value expected to be achieved on the electrostatic chuck, that is, the voltage signal expected to be input by the RF voltage sensor. Therefore, this application uses the voltage setting value of the lower RF power supply as the input voltage signal of the RF voltage sensor, and substitutes the input voltage signal of this RF voltage sensor into the actual input-output correspondence of the preset RF voltage sensor to obtain the output voltage signal of the RF voltage sensor when the input voltage setting value is reached.

[0075] The condition for the lower RF power supply to reach steady state during voltage control is: target voltage = RF voltage sensor output voltage signal * sensor conversion factor Gain_av. To ensure that the actual voltage value on the electrostatic chuck (the actual voltage signal input by the RF voltage sensor) equals the uncorrected voltage setting value of the lower RF power supply when the lower RF power supply reaches steady state, the following setting is required: target voltage = RF voltage sensor output voltage signal at the input voltage setting value * sensor conversion factor Gain_av. For example, if the uncorrected voltage setting value of the lower RF power supply is B (0-1000V), the output voltage signal of the RF voltage sensor at the input voltage setting value B is F(B), and the target voltage value is Vsetpoint, then Vsetpoint = F(B) * Gain_av. In this case, when the lower RF power supply reaches steady state, the actual voltage value on the electrostatic chuck equals the voltage setting value B.

[0076] As an optional embodiment, the process of presetting the actual input-output correspondence of the radio frequency voltage sensor includes:

[0077] Determine the voltage transfer functions corresponding to different circuits within the RF voltage sensor;

[0078] The voltage transfer functions corresponding to the different circuits are combined to obtain a total voltage transfer function representing the actual input-output correspondence of the RF voltage sensor;

[0079] Based on the input and output sample data of the radio frequency voltage sensor, a clear relationship for the total voltage transfer function is determined.

[0080] In existing solutions, a linear function is used to establish the input-output correspondence of the RF voltage sensor. Specifically, it is assumed that the input and output of the RF voltage sensor are in a directly proportional relationship: Gain = Vin / Vout. However, in reality, the input and output of the RF voltage sensor are in a nonlinear relationship. This results in low accuracy in the input-output correspondence of the RF voltage sensor established using a linear function.

[0081] Based on this, the present application first divides the RF voltage sensor into multiple circuits according to circuit functions, and then determines the voltage transfer functions corresponding to the different circuits in the RF voltage sensor based on the input-output correspondence of each circuit in the RF voltage sensor, and combines the voltage transfer functions corresponding to the different circuits in the RF voltage sensor to obtain a total voltage transfer function that characterizes the actual input-output correspondence of the RF voltage sensor. Then, multiple input and output signals of the RF voltage sensor are measured experimentally, and the multiple input and output signals of the experimentally measured RF voltage sensor are used as input and output sample data of the RF voltage sensor, so as to determine a clear relationship of the total voltage transfer function through the input and output sample data of the RF voltage sensor, thereby accurately describing the input-output correspondence of the RF voltage sensor.

[0082] Please refer to Figure 4 , Figure 4 A schematic diagram of the voltage transfer functions of different circuits in a radio frequency voltage sensor provided in an embodiment of the present application.

[0083] As an optional embodiment, the radio frequency voltage sensor includes a voltage divider circuit, a detection circuit and a linear amplifier circuit in sequence;

[0084] Then determine the voltage transfer functions corresponding to different circuits in the RF voltage sensor, including:

[0085] Determine the voltage transfer function corresponding to the voltage divider circuit as y0=f1(x)=k1*x; where k1 is the first coefficient; x is the RF voltage signal input by the RF voltage sensor, which serves as the input voltage signal of the voltage divider circuit; y0 is the output voltage signal of the voltage divider circuit, which serves as the input voltage signal of the detection circuit;

[0086] Determine the voltage transfer function corresponding to the detection circuit as y1=f2(y0); where y1 is the output voltage signal of the detection circuit, which serves as the input voltage signal of the linear amplifier circuit;

[0087] Determine the voltage transfer function corresponding to the linear amplifier circuit as y2=f3(y1)=k2*y1+b1; wherein k2 is the second coefficient; b1 is the first constant; y2 is the output voltage signal of the linear amplifier circuit, which serves as the output voltage signal of the RF voltage sensor.

[0088] In specific applications, RF voltage sensors can be divided into voltage divider circuit, detection circuit, and linear amplifier circuit according to circuit function. Specifically, the RF voltage is loaded to the input port of the RF voltage sensor, and is processed in sequence by the voltage divider circuit, detection circuit, and linear amplifier circuit, and finally output as a 0-10V DC voltage signal.

[0089] like Figure 4As shown, the input-output correspondence of each functional circuit of the RF voltage sensor can be expressed by a voltage transfer function. The input-output correspondence of the voltage divider circuit can be expressed by a voltage transfer function y0=f1(x)=k1*x; the input-output correspondence of the detection circuit can be expressed by a voltage transfer function y1=f2(y0); the input-output correspondence of the linear amplifier circuit can be expressed by a voltage transfer function y2=f3(y1)=k2*y1+b1.

[0090] Please refer to Figure 5 , Figure 5 A typical circuit diagram of a detection circuit provided in an embodiment of the present application.

[0091] As an optional embodiment, the input voltage signal of the detection circuit is regulated by the internal diode D1 and then output;

[0092] The voltage transfer function corresponding to the detection circuit is determined to be y1=f2(y0), including:

[0093] The detection circuit is simulated to obtain a simulation curve representing the corresponding relationship between the input voltage signal of the detection circuit and the voltage drop signal across the diode D1;

[0094] The simulation curve is fitted with a logarithmic function to obtain a fitting relationship y3=k3*ln(x)+b2; wherein y3 is the voltage drop signal on the diode D1; k3 is the third coefficient; and b2 is the second constant.

[0095] Based on the fitting relationship, the voltage transfer function corresponding to the detection circuit is obtained: y1 = f2 (y0) = y0 - k3 * ln (x) - b2.

[0096] In specific applications, such as Figure 5 As shown in Figure 1, the detector circuit, consisting of diode D1 (such as a Schottky diode) and capacitor C1, detects the peak value of the AC input signal. Diode D1 in the detector circuit is the primary factor contributing to the nonlinearity of the RF voltage sensor. This nonlinearity arises from the fact that when the input voltage across diode D1 is low, it is not fully on, preventing the input voltage from passing through it, resulting in nonlinear signal variations. Therefore, finding a model that accurately describes diode D1 is crucial for resolving nonlinearity in RF voltage sensors.

[0097] Based on this, the present application simulates the detection circuit to obtain a simulation curve representing the corresponding relationship between the input voltage signal of the detection circuit and the voltage drop signal on the diode D1. Specifically, the simulation curve is drawn with the input voltage signal (Vin, in V) of the detection circuit as the horizontal axis and the voltage drop signal (Vd, in V) on the diode D1 as the vertical axis, as shown in FIG. Figure 6As shown, the data of the simulation curve is fitted according to the logarithmic function, and the fitting relationship y=0.0322*ln(x)+0.1557 can be obtained, R 2 is 0.9967(R 2 is the goodness of curve fitting, R 2 The closer it is to 1, the better the curve fit. It can be seen that a logarithmic function can well describe the relationship between the voltage drop across diode D1 and the input voltage of the detector circuit. Therefore, the voltage transfer function corresponding to the detector circuit can be expressed as y1 = f2(y0) = y0 - k3*ln(x) - b2.

[0098] As an optional embodiment, the voltage transfer functions corresponding to different circuits are combined to obtain a total voltage transfer function that represents the actual input-output correspondence relationship of the RF voltage sensor, including:

[0099] By combining the voltage transfer functions corresponding to the voltage divider circuit, the detection circuit, and the linear amplifier circuit, a total voltage transfer function F(x)=k4*x+k5*ln(x)+b3 is obtained, which represents the actual input-output correspondence of the RF voltage sensor; where k4 is the fourth coefficient; k5 is the fifth coefficient; and b3 is the third constant.

[0100] In a specific application, after combining the voltage transfer functions corresponding to the voltage divider circuit, the detection circuit, and the linear amplifier circuit, the corresponding relationship between the input and output of the RF voltage sensor can be described by F(x)=k4*x+k5*ln(x)+b3.

[0101] As an optional embodiment, determining a clear relationship of the total voltage transfer function based on the input and output sample data of the radio frequency voltage sensor includes:

[0102] The input and output sample data of the RF voltage sensor are curve-fitted using the least squares method to obtain a clear relationship of the total voltage transfer function.

[0103] In a specific application, the present application uses the least-squares minimization method to perform curve fitting on the input and output sample data of the RF voltage sensor (such as the multiple input and output signals of the RF voltage sensor experimentally measured as shown in Table 1 below) to obtain a clear relationship for the total voltage transfer function of the RF voltage sensor: y = 0.00793778*x - 0.0260501*ln(x) + 0.06070613.

[0104] Table 1

[0105]

[0106] In Table 1, DIF% represents the deviation relative to the test data. A negative value indicates that the calculated value Vout' is smaller than the actual measured value Vout, and a positive value indicates that the calculated value Vout' is larger than the actual measured value Vout.

[0107] As an optional embodiment, the voltage control method further includes:

[0108] The total voltage transfer function is solved according to the current output voltage signal of the radio frequency voltage sensor to obtain the current theoretical input voltage signal of the radio frequency voltage sensor.

[0109] In existing solutions, the lower RF power supply not only controls the output voltage signal (Vout) of the RF voltage sensor but also returns Vout*Gain_av as a real-time voltage monitoring value to the upper computer monitoring system. However, because the actual sensor conversion coefficient (Gain) of the RF voltage sensor varies at different times, this can cause deviations in the voltage monitoring value.

[0110] Based on the solution of the present application, when monitoring the voltage of the RF power supply, the corresponding input voltage signal Vin is found from the output voltage signal Vout of the RF voltage sensor, that is, a curve y=F(x) is fitted from Vin to Vout, and then a curve x=F(y) is fitted from Vout to Vin to obtain the voltage monitoring value x. However, this solution still has a certain deviation: two corresponding relationships will be obtained from x to y and from y to x, which causes deviation in the corresponding relationship, such as Figure 7 As shown, this will result in the voltage setting value being 100 V, the RF power supply output being stable at 100 V, but the final voltage monitoring value read may be 105 V. If y = F(x) can be inverted, the problem of inconsistency between the voltage setting value and the voltage monitoring value read can be solved.

[0111] Based on this, the total voltage transfer function y=F(x) that characterizes the actual input-output correspondence of the RF voltage sensor is known. The present application can solve the total voltage transfer function y=F(x) according to the current output voltage signal of the RF voltage sensor, obtain the current theoretical input voltage signal of the RF voltage sensor, and return the current theoretical input voltage signal of the RF voltage sensor as a real-time voltage monitoring value to the host computer monitoring system, with high voltage monitoring accuracy.

[0112] As an optional embodiment, the total voltage transfer function is F(x)=k4*x+k5*ln(x)+b3; wherein x is the RF voltage signal input by the RF voltage sensor; k4 is the fourth coefficient; k5 is the fifth coefficient; and b3 is the third constant.

[0113] Then, the total voltage transfer function is solved according to the current output voltage signal of the RF voltage sensor to obtain the current theoretical input voltage signal of the RF voltage sensor, including:

[0114] The total voltage transfer function is simplified to obtain a simplified transfer function F(x)=k4*x+b3; where x0=(A-b3) / k4, n=0; x0 is the initial setting value of the current input voltage signal of the RF voltage sensor; A is the current output voltage signal of the RF voltage sensor; b3 and k4 are both within the corresponding experimentally measured value range; n is the number of iterations;

[0115] According to the error function f(x)=F(x n )-A calculates the error f(x) and determines the first iteration end condition |f(x)|<ε or the second iteration end condition n>n end Is it true? Where || is the absolute value; ε is the preset reading error threshold; n end is the preset maximum number of iterations;

[0116] If the first and second iteration end conditions are not met, then according to x n+1 =x n -F(x n ) / F(x n )', n = n + 1 to perform parameter iteration and return to execute according to the error function f(x) = F(x n )-A step of calculating the error f(x); where F(x n )' is F(x n )’s derivative;

[0117] If one of the first and second iteration end conditions is met, then x n As the input voltage signal of the current theory of RF voltage sensor.

[0118] In a specific application, the present application uses Newton's method to solve the total voltage transfer function y=F(x) based on the current output voltage signal of the RF voltage sensor to obtain the current theoretical input voltage signal of the RF voltage sensor.

[0119] Specifically, when the RF voltage sensor reads the voltage value at a certain voltage sampling interval, it is necessary to obtain the theoretical input voltage Vin=B (generally 0-1000V) of the RF voltage sensor based on the output voltage Vout=A (generally 0-10V) of the RF voltage sensor. Figure 8The solution steps shown are used to obtain the theoretical input voltage signal Vin of the RF voltage sensor. The solution steps are as follows:

[0120] Step 1: Based on the current output voltage signal A of the input RF voltage sensor and the simplified transfer function F(x) = k4*x + b3, solve for x0 = (A-b3) / k4, where n = 0. It should be noted that the fitting function y = F(x) = k4*x + k5*ln(x) + b3, measured through extensive experiments, shows that k4 ranges from 0.00796 to 0.0086, k5 ranges from -0.0267 to -0.0174, and b3 ranges from 0.0345 to 0.0824. Since the input and output of the RF voltage sensor are linear under macroscopic conditions, the linearity degrades only at low voltages. To reduce the number of iterations and improve computational speed, the fitting function y = F(x) = k4*x + k5*ln(x) + b3 is simplified to y = F(x) = k4*x + b3, where b3 and k4 are both within their respective experimentally measured ranges.

[0121] Step 2: Determine the end condition of the first iteration |f(x)|=|F(x n )-A|<ε or the second iteration end condition n>100 is established; if both the first iteration end condition and the second iteration end condition are not established, then execute Step 3; if one of the first iteration end condition and the second iteration end condition is established, then x n As the current theoretical input voltage signal of the RF voltage sensor, it should be noted that since the voltage control accuracy of the RF power supply is required to be within 1%, the accuracy of the RF voltage sensor must be at least 0.1%, and here ε = x0*0.001 is taken.

[0122] Step 3: Update the value x of the approximate solution n+1 =x n -F(x n ) / F(x n )', n=n+1, return to execute step 2.

[0123] Experimental measurements show that the voltage reading process using this method takes between 1ms and 29ms, with fewer than 30 iterations, which is sufficient to meet the sampling interval requirement of the host monitoring system (100ms). Table 2 below shows the test results of this technical solution. Compared with the test results of the prior art solution in Table 1, the deviation of the relative test data is reduced.

[0124] Table 2

[0125]

[0126] In summary, according to the above working logic of controlling voltage and reading voltage, the present application can achieve a control and reading accuracy of the RF power supply voltage of more than 1%.

[0127] The present application also provides a semiconductor process equipment, comprising:

[0128] electrostatic chuck;

[0129] a radio frequency voltage sensor connected to the electrostatic chuck;

[0130] a lower RF power supply feeding the electrostatic chuck;

[0131] A controller disposed in the lower RF power supply and connected to the RF voltage sensor is used to implement the steps of any of the above-mentioned voltage control methods for the lower RF power supply when executing a computer program stored in the controller.

[0132] For an introduction to the semiconductor process equipment provided in this application, please refer to the above-mentioned embodiment of the voltage control method, and this application will not go into details here.

[0133] Those skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0134] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, and this is merely a way of distinguishing the objects of the same attributes when describing them in the embodiments of the present application. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment comprising a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application 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 application.

Claims

1. A voltage control method for a radio frequency power supply, characterized in that: include: A voltage setting value of a lower RF power supply feeding the electrostatic chuck is obtained in advance, and the voltage setting value is corrected according to a preset voltage correction strategy to obtain a target voltage value; wherein the correction purpose of the preset voltage correction strategy is to ensure that the actual output voltage of the lower RF power supply is equal to the voltage setting value when the lower RF power supply reaches a steady state; Obtaining a first voltage signal output by a radio frequency voltage sensor connected to the electrostatic chuck, and obtaining a second voltage signal theoretically input by the radio frequency voltage sensor based on the first voltage signal and a sensor conversion coefficient representing an average input-output correspondence relationship of the radio frequency voltage sensor; The target voltage value and the second voltage signal are compared, and the output power of the lower RF power supply is adjusted according to the comparison result so that the second voltage signal is equal to the target voltage value.

2. The voltage control method according to claim 1, wherein: The step of correcting the voltage setting value according to a preset voltage correction strategy to obtain a target voltage value includes: Using the voltage setting value as the input voltage signal of the radio frequency voltage sensor, and obtaining the output voltage signal of the radio frequency voltage sensor according to a preset actual input-output correspondence relationship of the radio frequency voltage sensor; A third voltage signal input by the radio frequency voltage sensor is obtained according to the output voltage signal and the sensor conversion coefficient, so as to use the third voltage signal as the target voltage value obtained after the voltage setting value is corrected.

3. The voltage control method according to claim 2, wherein: The process of presetting the actual input-output correspondence relationship of the radio frequency voltage sensor includes: Determining voltage transfer functions corresponding to different circuits in the radio frequency voltage sensor; Combining the voltage transfer functions corresponding to the different circuits to obtain a total voltage transfer function representing the actual input-output correspondence of the radio frequency voltage sensor; An explicit relational expression of the total voltage transfer function is determined based on the input and output sample data of the radio frequency voltage sensor.

4. The voltage control method according to claim 3, wherein: The radio frequency voltage sensor includes a voltage divider circuit, a detection circuit and a linear amplifier circuit in sequence; Then, determining the voltage transfer functions corresponding to different circuits in the radio frequency voltage sensor includes: Determine the voltage transfer function corresponding to the voltage divider circuit as y0=f1(x)=k1*x; wherein k1 is a first coefficient; x is the RF voltage signal input by the RF voltage sensor, which serves as the input voltage signal of the voltage divider circuit; y0 is the output voltage signal of the voltage divider circuit, which serves as the input voltage signal of the detection circuit; Determine the voltage transfer function corresponding to the detection circuit as y1=f2(y0); wherein y1 is the output voltage signal of the detection circuit, which serves as the input voltage signal of the linear amplifier circuit; Determine that the voltage transfer function corresponding to the linear amplification circuit is y2=f3(y1)=k2*y1+b1; wherein k2 is the second coefficient; b1 is the first constant; and y2 is the output voltage signal of the linear amplification circuit, which serves as the output voltage signal of the radio frequency voltage sensor.

5. The voltage control method according to claim 4, wherein: The input voltage signal of the detection circuit is output after being regulated by the internal diode; Then, determining that the voltage transfer function corresponding to the detection circuit is y1=f2(y0) includes: Simulating the detection circuit to obtain a simulation curve representing a corresponding relationship between an input voltage signal of the detection circuit and a voltage drop signal across the diode; The simulation curve is fitted with data according to a logarithmic function to obtain a fitting relationship y3=k3*ln(x)+b2; wherein y3 is the voltage drop signal on the diode; k3 is the third coefficient; and b2 is the second constant; Based on the fitting relationship, the voltage transfer function y1=f2(y0)=y0-k3*ln(x)-b2 corresponding to the detection circuit is obtained.

6. The voltage control method according to claim 5, wherein: The voltage transfer functions corresponding to the different circuits are combined to obtain a total voltage transfer function representing the actual input-output correspondence of the radio frequency voltage sensor, including: The voltage transfer functions corresponding to the voltage divider circuit, the detection circuit, and the linear amplification circuit are combined to obtain a total voltage transfer function F(x)=k4*x+k5*ln(x)+b3, which represents the actual input-output correspondence of the RF voltage sensor; wherein k4 is the fourth coefficient; k5 is the fifth coefficient; and b3 is the third constant.

7. The voltage control method according to claim 3, wherein: Determining the explicit relationship of the total voltage transfer function based on the input and output sample data of the radio frequency voltage sensor includes: The input and output sample data of the radio frequency voltage sensor are subjected to curve fitting using the least square method to obtain a clear relationship of the total voltage transfer function.

8. The voltage control method according to any one of claims 3 to 7, wherein: The voltage control method further includes: The total voltage transfer function is solved according to the current output voltage signal of the radio frequency voltage sensor to obtain the current theoretical input voltage signal of the radio frequency voltage sensor.

9. The voltage control method according to claim 8, wherein: The total voltage transfer function is F(x)=k4*x+k5*ln(x)+b3; wherein x is the RF voltage signal input by the RF voltage sensor; k4 is the fourth coefficient; k5 is the fifth coefficient; and b3 is the third constant. Solving the total voltage transfer function according to the current output voltage signal of the RF voltage sensor to obtain the current theoretical input voltage signal of the RF voltage sensor includes: The total voltage transfer function is simplified to obtain a simplified transfer function F(x)=k4*x+b3; wherein x0=(A-b3) / k4, and n=0; x0 is the initial setting value of the voltage signal currently input by the RF voltage sensor; A is the current output voltage signal of the RF voltage sensor; b3 and k4 are both within the corresponding experimentally measured value ranges; and n is the number of iterations. According to the error function f(x)=F(x n )-A calculates the error f(x) and determines the first iteration end condition |f(x)|<ε or the second iteration end condition n>n end Is it true? Where || is the absolute value; ε is the preset reading error threshold; n end is the preset maximum number of iterations; If the first iteration end condition and the second iteration end condition are both not met, then according to x n+1 =x n -F(x n ) / F(x n )', n = n + 1 to perform parameter iteration and return to execute according to the error function f(x) = F(x n )-A step of calculating the error f(x); where F(x n )' is F(x n )’s derivative; If one of the first iteration end condition and the second iteration end condition is met, then x n As the current theoretical input voltage signal of the RF voltage sensor.

10. A semiconductor process equipment, characterized in that: include: electrostatic chuck; a radio frequency voltage sensor connected to the electrostatic chuck; a lower radio frequency power supply feeding power to the electrostatic chuck; A controller provided in the lower RF power supply and connected to the RF voltage sensor is configured to implement the steps of the voltage control method for the lower RF power supply according to any one of claims 1 to 9 when executing a computer program stored therein.

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