A method and system for monitoring the state of wafer adhesion of an electrostatic chuck

Abstract

This invention discloses a method for monitoring the adsorption state of an electrostatic chuck wafer, comprising the following steps: If the wafer is not adsorbed, a reference frequency is found by frequency sweeping; based on the reference frequency, several sampling capacitors are obtained by frequency sweeping, and the initial capacitance is obtained by fitting the sampling capacitors; if the wafer is adsorbed, several sampling capacitors are obtained by frequency sweeping, and the adsorbed capacitance is obtained by fitting the sampling capacitors; the adsorbed capacitance is compared with the initial capacitance to determine the wafer adsorption state. By combining automatic reference frequency optimization with graded frequency sweeping calibration, it can adapt to LC RF filters with different capacitance values ​​from a few nanofarads to thousands of nanofarads without manual parameter preset, greatly enhancing the system's versatility, stability, and long-term reliability, reducing equipment maintenance costs, effectively solving the problems of narrow measurement range and inability to resolve small changes under large base capacitance values ​​in traditional capacitance detection, and avoiding detection failures or misjudgments caused by differences in filter capacitance values.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and in particular to a method and system for monitoring the adsorption state of an electrostatic chuck wafer. Background Technology

[0002] In semiconductor manufacturing, electrostatic chucks are key components used to hold wafers in processes such as etching and deposition. The accuracy of their adsorption state directly determines process uniformity and product yield. Assessing the state by measuring the change in capacitance between the electrostatic chuck and the wafer offers advantages such as non-contact operation and high potential accuracy. However, existing capacitance measurement technologies have limited ranges, making them difficult to adapt to practical applications.

[0003] Specifically, in electrostatic chuck systems, an RF filter (composed of an LC network) is typically installed between the power supply and the RF generator for high-frequency isolation and protection. Its base capacitance ranges from a few nanofarads to several hundred nanofarads, while the effective capacitance change caused by wafer adsorption is only a few tenths of a nanofarad to a few nanofarads, a negligible percentage. For example, if the filter capacitance is 500nF and the wafer adsorption change is 0.5nF, then the minute change of 0.5nF needs to be detected on a base value of 500nF, requiring a relative accuracy of 0.1%. Existing capacitance detection schemes have narrow ranges, mostly applicable to low capacitance ranges (e.g., 0-100nF). For large capacitance ranges (0-1000nF), they cannot resolve minute changes on a wide base value, easily leading to misjudgments or missed detections. Summary of the Invention

[0004] This application provides a method and system for monitoring the adsorption state of an electrostatic chuck wafer, which improves the adaptability of the monitoring system to filters with different capacitance values ​​and solves the problem of misjudgment of wafer adsorption state caused by range changes due to filter variations.

[0005] This application provides a method for monitoring the adsorption state of an electrostatic chuck wafer, comprising the following steps: S1: When the wafer is in an unattached state, a series of AC excitations of different frequencies are applied to the load one by one in a step and / or step-back manner, with frequency f as the initial frequency. The load feedback capacitor is compared with the preset capacitor of the corresponding frequency, and the frequency of the first load feedback capacitor that meets the preset comparison condition is taken as the reference frequency. S2: Based on the reference frequency, apply the reference frequency and a series of different frequency AC excitations obtained in a step manner to the load one by one to obtain the corresponding sampling capacitors. Fit all the sampling capacitors to obtain the initial capacitor. S3: When the wafer is in the adsorption state, the reference frequency and a series of AC excitations of different frequencies obtained in a step manner based on the reference frequency are applied to the load one by one to obtain the corresponding sampling capacitor. All sampling capacitors are fitted to obtain the adsorption capacitor. S4: Compare the adsorption capacitance with the initial capacitance to determine the wafer adsorption state.

[0006] The beneficial effects of the above embodiments are as follows: by combining automatic optimization of the reference frequency with hierarchical frequency sweep calibration, it can adapt to LC RF filters with different capacitance values ​​from a few nanofarads to thousands of nanofarads without the need for manual parameter preset, which greatly enhances the versatility, stability and long-term reliability of the system, reduces equipment maintenance costs, effectively solves the problem of narrow detection range of traditional capacitance and inability to resolve small changes under large base value capacitance, and avoids detection failure or misjudgment caused by differences in filter capacitance value; at the same time, based on the reference frequency, the initial capacitance and sampling capacitance are determined by fine sweep fitting, which can improve detection accuracy and enable the system to maintain stable and reliable judgment capability in complex semiconductor processing scenarios.

[0007] Based on the above embodiments, the embodiments of this application can be further improved as follows: In one embodiment of this application: step S1 includes the following steps: S1.1: Treat f as f 输入 Initial value; S1.2: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.2. If ΔC > a, where a is the first preset value and is greater than 0, then f 输入 =f 输入 +f 步进1 Returning to step S1.2, if ΔC < b, and b is the second preset value and less than 0, then f 输入 =f 输入 -f 步退 If b≤ΔC≤a, proceed to step S1.3; if b≤ΔC≤a, proceed to step S1.5. S1.3: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.3. If ΔC < b, then f 输入 =f 输入 -f 步退 Returning to S1.3, if ΔC1 > a, then f 输入 =f 输入 +f 步进2，Proceed to step S1.4. If b≤ΔC≤a, proceed to step S1.5. S1.4: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.4. If ΔC > a, then f 输入 =f 输入 +f 步进2 If b≤ΔC≤a, proceed to step S1.5; S1.5: f 输入 Set as the reference frequency.

[0008] In one embodiment of this application: step S2 includes the following steps: S2.1: n=0; S2.2: f 输入 The AC excitation of the corresponding frequency is applied to the load as the initial input value. The load includes an RF filter and a wafer in an unattached state, and the sampling capacitance corresponding to the load is obtained. S2.3: f 输入 =f 输入 +f 步进3 If n = n + 1, and n ≤ e, return to step S2.2; otherwise, proceed to step S2.4. S2.4: Fit all sampled capacitances from step S2.2 to obtain the initial capacitance C. 初 .

[0009] In one embodiment of this application, step S3 includes the following steps: S3.1: n=0; S3.2: f 输入 An AC excitation of the corresponding frequency is applied as the initial input value to the load, which includes an RF filter and a wafer in an adsorbed state, to obtain the sampling capacitance corresponding to the load. S3.3: f 输入 =f 输入 +f 步进3 If n = n + 1, and n ≤ c, return to step S3.2; otherwise, proceed to step S3.4. S3.4: Fit all sampled capacitances from step S3.2 and obtain the adsorption capacitance C. 吸 .

[0010] In one embodiment of this application: in step S4, if the difference between the initial capacitance and the adsorption capacitance is greater than or equal to a threshold, the wafer is determined to be effectively adsorbed; otherwise, the wafer is determined to be ineffectively adsorbed. Attached Figure Description

[0011] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0012] Figure 1 This is a schematic diagram of a monitoring system for the adsorption state of a wafer in an electrostatic chuck. Figure 2 This is a block diagram of the signal generation unit. Figure 3 The principle block diagram of the coupling unit Figure 4 This is a block diagram illustrating the principle of the conditioning unit. Detailed Implementation

[0013] In this application, unless otherwise expressly specified and limited, the terminology used should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part of a device; it can be a direct connection or an indirect connection through an intermediate medium. If electrical or electronic equipment is involved, it can also refer to an electrical connection or a communication signal connection, etc. For those skilled in the art, the specific meaning of different terms in this invention can be understood according to the specific circumstances, and the scope of the specific meaning should be limited to achieving the functions of this application.

[0014] In the description of this application, it should be understood that the directional terms or positional relationships described are based on the orientation or positional relationships shown in the accompanying drawings, or based on the orientation or positional relationships in actual use, and are only for the purpose of facilitating the description of the contents of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0015] Example 1 A method for monitoring the adsorption state of a wafer in an electrostatic chuck includes the following steps: S1: When the wafer is in an unattached state, a series of AC excitations of different frequencies are applied to the load one by one in a step and / or step-back manner, with frequency f as the initial frequency. The load feedback capacitor is compared with the preset capacitor of the corresponding frequency, and the frequency of the first load feedback capacitor that meets the preset comparison condition is taken as the reference frequency. S2: Based on the reference frequency, apply the reference frequency and a series of different frequency AC excitations obtained in a step manner to the load one by one to obtain the corresponding sampling capacitors. Fit all the sampling capacitors to obtain the initial capacitor. S3: When the wafer is in the adsorption state, the reference frequency and a series of AC excitations of different frequencies obtained in a step manner based on the reference frequency are applied to the load one by one to obtain the corresponding sampling capacitor. All sampling capacitors are fitted to obtain the adsorption capacitor. S4: Compare the adsorption capacitance with the initial capacitance to determine the wafer adsorption state.

[0016] The preset capacitance is related to the load and the wafer, and is an empirical value or a pre-measured value. In steps S1, S2 and S3, the electrostatic chuck holds a wafer. In steps S1 and S2, the load includes an RF filter and a wafer in an unattached state. In step S3, the load includes an RF filter and a wafer in an attached state.

[0017] Specifically, step S1 includes the following steps: S1.1: Treat f as f 输入 Initial value; S1.2: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.2. If ΔC > a, where a is the first preset value and is greater than 0, then f 输入 =f 输入 +f 步进1 Returning to step S1.2, if ΔC < b, and b is the second preset value and less than 0, then f 输入 =f 输入 -f 步退 Proceed to step S1.3; if b≤ΔC≤a, proceed to step S1.5. S1.3: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.3. If ΔC < b, then f 输入 =f 输入 -f 步退 Returning to step S1.3, if ΔC1>a, then f 输入 =f 输入 +f 步进2， Proceed to step S1.4. If b ≤ ΔC ≤ a, proceed to step S1.5. S1.4: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.4. If ΔC > a, then f 输入 =f 输入 +f 步进2If b≤ΔC≤a, proceed to step S1.5; S1.5: f 输入 Set as the reference frequency.

[0018] Where f = 1 kHz, meaning the initial step is 1 kHz; a = 1 nF, b = -1 nF, f 步进1 =1KHz, f 步退 =100Hz, f 步进2 =10Hz; that is, first use 1KHz as the initial frequency, and sweep the frequency upward in steps of 1KHz. If the judgment condition is met, sweep the frequency downward in steps of 100Hz. If the judgment condition is met, sweep the frequency upward in steps of 10Hz until |ΔC|≤1nF.

[0019] Specifically, S2 includes the following steps: S2.1: n=0; S2.2: f 输入 The AC excitation of the corresponding frequency is applied to the load as the initial input value. The load includes an RF filter and a wafer in an unattached state, and the sampling capacitance corresponding to the load is obtained. S2.3: f 输入 =f 输入 +f 步进3 If n = n + 1, and n ≤ e, return to step S2.2; otherwise, proceed to step S2.4. S2.4: Fit all sampled capacitances from step S2.2 to obtain the initial capacitance C. 初 .

[0020] Among them, f 步进3 =1Hz, e=10, the sampling capacitance fitting method can process the sampling capacitance using a weighted average algorithm to obtain the initial capacitance C. 初 .

[0021] Specifically, S3 includes the following steps: S3.1: n=0; S3.2: f 输入 An AC excitation of the corresponding frequency is applied as the initial input value to the load, which includes an RF filter and a wafer in an adsorbed state, to obtain the sampling capacitance corresponding to the load. S3.3: f 输入 =f 输入 +f 步进3 If n = n + 1, and n ≤ c, return to step S3.2; otherwise, proceed to step S3.4. S3.4: Fit all sampled capacitances from step S3.2 and obtain the adsorption capacitance C. 吸 .

[0022] Where C=10, the sampling capacitance fitting method can process the sampling capacitance using a weighted average algorithm to obtain the adsorption capacitance C. 吸 .

[0023] Specifically, if the difference between the initial capacitance and the adsorption capacitance is greater than or equal to the threshold, the wafer is determined to be effectively adsorbed; otherwise, the wafer is determined to be ineffectively adsorbed.

[0024] The threshold is independent of the filter, but is related to the size and warpage of the wafer, and the magnitude is in the order of several nanofarads.

[0025] This method for monitoring the adsorption state of electrostatic chuck wafers combines automatic optimization of the reference frequency with graded frequency sweep calibration. It can adapt to LC RF filters with different capacitance values ​​ranging from a few nanofarads to thousands of nanofarads without the need for manual parameter preset. This greatly enhances the system's versatility, stability, and long-term reliability, reduces equipment maintenance costs, and effectively solves the problems of narrow measurement range and inability to resolve minute changes under large base capacitance values ​​in traditional capacitance detection. It also avoids detection failures or misjudgments caused by differences in filter capacitance values. At the same time, based on the reference frequency, the initial capacitance and sampling capacitance are determined by fine sweep fitting, which can improve detection accuracy and enable the system to maintain stable and reliable judgment capabilities even in complex semiconductor processing scenarios.

[0026] Example 2 A monitoring system for the adsorption state of an electrostatic chuck wafer, employing the monitoring method disclosed in Example 1, specifically includes: a signal generation unit, a coupling unit, a conditioning unit, and a control unit. The control unit is electrically connected to the multi-frequency signal generation unit and the coupling unit. The control unit is used to send frequency control commands to the signal generation unit and high-voltage control commands to the coupling unit. The signal generation unit is also electrically connected to the coupling unit and is used to send a series of AC excitation signals of different frequencies to the coupling unit. The coupling unit is also electrically connected to the load. The coupling unit is used to couple the high-voltage DC signal and the AC excitation signal into a DC composite output signal and send it to the load. The load is also electrically connected to the conditioning unit and sends voltage and current feedback signals to the conditioning unit. The conditioning unit is electrically connected to the control unit and sends digital feedback signals to the control unit. The control unit is used to process the digital signals.

[0027] Specifically, the signal generation unit is a multi-frequency signal generation unit, which includes a DDS generation circuit, an amplification circuit, and a power drive circuit connected in sequence by electrical signals. The DDS generation circuit is connected to the control unit by electrical signals and receives the frequency control signal sent by the control unit. The power drive circuit is connected to the coupling unit by electrical signals and sends AC excitation to the coupling unit.

[0028] Specifically, the coupling unit is a high-voltage DC and broadband signal coupling unit, which includes an electrical connection between the high-voltage DC power supply and the broadband signal coupling circuit, an electrical connection between the high-voltage DC power supply and the control unit, and an electrical connection between the broadband coupling unit and the signal generation unit and the load. It is used to receive AC excitation signals and couple the AC excitation signals with the high-voltage DC signals to form a composite output signal.

[0029] Specifically, the conditioning unit includes a differential sampling circuit, a gain conditioning circuit, and an AD conversion circuit connected in sequence by electrical signals. The differential sampling circuit is connected to the load electrical signal and receives the voltage and current signals fed back from the load. The AD conversion circuit is connected to the control unit electrical signal and outputs digital signals.

[0030] Specifically, the control unit can be an MCU control unit, which receives digital feedback signals, compares the digital signals with the set thresholds, reissues frequency control commands and high voltage control commands, or outputs whether the adsorption signal is valid.

[0031] Specifically, the circuits involved in each of the above units are all conventional circuits that already exist in this field.

[0032] The above are merely embodiments of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, based on the guidance provided in this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for monitoring the adsorption state of an electrostatic chuck wafer, characterized in that, Includes the following steps: S1: When the wafer is in an unattached state, a series of AC excitations of different frequencies are applied to the load one by one in a step and / or step-back manner, with frequency f as the initial frequency. The load feedback capacitor is compared with the preset capacitor of the corresponding frequency, and the frequency of the first load feedback capacitor that meets the preset comparison condition is taken as the reference frequency. S2: Based on the reference frequency, apply the reference frequency and a series of different frequency AC excitations obtained in a step manner to the load one by one to obtain the corresponding sampling capacitors. Fit all the sampling capacitors to obtain the initial capacitor. S3: When the wafer is in the adsorption state, the reference frequency and a series of AC excitations of different frequencies obtained in a step manner based on the reference frequency are applied to the load one by one to obtain the corresponding sampling capacitor. All sampling capacitors are fitted to obtain the adsorption capacitor. S4: Compare the adsorption capacitance with the initial capacitance to determine the wafer adsorption state.

2. The monitoring method according to claim 1, characterized in that, Step S1 includes the following steps: S1.1: Treat f as f 输入 Initial value; S1.2: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.

2. If ΔC > a, where a is the first preset value and is greater than 0, then f 输入 =f 输入 +f 步进1 Returning to step S1.2, if ΔC < b, and b is the second preset value and less than 0, then f 输入 =f 输入 -f 步退 Proceed to step S1.3; if b≤ΔC≤a, proceed to step S1.

5. S1.3: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.

3. If ΔC < b, then f 输入 =f 输入 -f 步退 Returning to step S1.3, if ΔC1>a, then f 输入 =f 输入 +f 步进2， Proceed to step S1.

4. If b ≤ ΔC ≤ a, proceed to step S1.

5. S1.4: f 输入 As an AC frequency signal applied to the load, the load feedback capacitor is obtained, and f 输入 The difference ΔC is obtained by subtracting the corresponding preset capacitor from the load feedback capacitor in step S1.

4. If ΔC > a, then f 输入 =f 输入 +f 步进2 If b≤ΔC≤a, proceed to step S1.5; S1.5: f 输入 Set as the reference frequency.

3. The monitoring method according to claim 2, characterized in that, Step S2 includes the following steps: S2.1: n=0; S2.2: f 输入 The AC excitation of the corresponding frequency is applied to the load as the initial input value. The load includes an RF filter and a wafer in an unattached state, and the sampling capacitance corresponding to the load is obtained. S2.3: f 输入 =f 输入 +f 步进3 If n = n + 1, and n ≤ e, return to step S2.2; otherwise, proceed to step S2.

4. S2.4: Fit all sampled capacitances from step S2.2 to obtain the initial capacitance C. 初 .

4. The monitoring method according to claim 3, characterized in that, Step S3 includes the following steps: S3.1: n=0; S3.2: f 输入 An AC excitation of the corresponding frequency is applied as the initial input value to the load, which includes an RF filter and a wafer in an adsorbed state, to obtain the sampling capacitance corresponding to the load. S3.3: f 输入 =f 输入 +f 步进3 If n = n + 1, and n ≤ c, return to S3.2; otherwise, proceed to step S3.

4. S3.4: Fit all sampled capacitances from step S3.2 and obtain the adsorption capacitance C. 吸 .

5. The monitoring method according to claim 4, characterized in that, In step S4, if the difference between the initial capacitance and the adsorption capacitance is greater than or equal to the threshold, the wafer is determined to be effectively adsorbed; otherwise, the wafer is determined to be ineffectively adsorbed.

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