Impedance matching method and apparatus, semiconductor process equipment

Abstract

This invention provides an impedance matching method and apparatus, and semiconductor process equipment. The method, applied to a process chamber in a semiconductor device, includes: performing impedance matching between the output impedance of a radio frequency (RF) power supply and the load impedance; after impedance matching, real-time detection of the RF power supply's cutoff frequency; determining whether the cutoff frequency is within a preset tolerance range; if not, adjusting the parameter value of the impedance-adjustable element of the matching unit, and then returning to determine whether the cutoff frequency is within the preset tolerance range. This invention can control the RF power supply's cutoff frequency within the tolerance range, increase the frequency adjustment window, and avoid the problem of ineffective reduction of reflected power, thereby improving the stability of chamber operation and process results.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more specifically, to an impedance matching method and apparatus, and semiconductor process equipment. Background Technology

[0002] Due to the application of radio frequency energy, plasma-enhanced atomic layer deposition (PEALD) technology can reduce the process temperature required for dielectric thin films, offers a wider range of selectable reaction sources, and provides advantages such as precise control over film thickness, good film quality, uniformity, and step coverage. With the rapid development of semiconductor technology, PEALD's applications have become increasingly widespread, making it an important thin film deposition process technology.

[0003] In the PEALD process, the RF energy feed time is set to vary from 1 second to tens of seconds depending on actual needs. As production capacity continues to expand, the PEALD process time is becoming increasingly faster. Limited by the torque, speed, and matching algorithm of mechanical components, relying solely on a matcher to adjust reflected power is no longer suitable for the short PEALD process. Therefore, an RF power supply with auto-frequency tuning is used to adjust its output frequency in real time according to the chamber load, thereby achieving RF loop impedance matching and reducing reflected power.

[0004] However, existing impedance matching methods suffer from a reduction in the adjustable window of the RF power supply frequency after impedance matching is achieved. This reduction may increase the probability that the frequency approaches the upper or lower limit of the adjustable window, thus making it impossible to effectively reduce the reflected power. Consequently, the stability of the chamber operation deteriorates, and it may also affect process results such as thin film uniformity and thin film density. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art, and proposes an impedance matching method and device, and semiconductor process equipment, which can control the cutoff frequency of the RF power supply within the tolerance range, increase the adjustable window of the frequency, avoid the problem that the reflected power cannot be effectively reduced, and thus improve the stability of the chamber operation and the stability of the process results.

[0006] To achieve the objectives of this invention, an impedance matching method is provided, applied to the process chamber of a semiconductor device, comprising:

[0007] Impedance matching is performed between the output impedance and the load impedance of the RF power supply.

[0008] After impedance matching is achieved, the cutoff frequency of the RF power supply is detected in real time.

[0009] Determine whether the cutoff frequency is within the preset tolerance range;

[0010] If not, adjust the parameter value of the impedance adjustable element of the matching unit and return to determine whether the cutoff frequency is within the preset tolerance range.

[0011] Optionally, before performing impedance matching between the output impedance of the RF power supply and the load impedance, the method further includes:

[0012] An insulating film is deposited on the surface of the components exposed to the plasma environment within the process chamber.

[0013] Optionally, the insulating film comprises silicon dioxide.

[0014] Optionally, the thickness of the insulating film is greater than or equal to and less than or equal to

[0015] Optionally, the impedance matching between the output impedance of the RF power supply and the load impedance includes:

[0016] The operating mode of the RF power supply is set to fixed frequency to maintain the output frequency of the RF power supply at an initial value, which is within the tolerance range.

[0017] Set the matching mode to automatic matching mode, introduce process gas into the process chamber, and turn on the RF power supply so that the matching mode uses an automatic matching algorithm to adjust the parameter value of the impedance adjustable element until impedance matching is achieved.

[0018] Store the current parameter value of the impedance-adjustable element, turn off the RF power supply, and stop the process gas from being introduced;

[0019] Set the operating mode of the matching device to manual mode, and set and maintain the parameter value of the impedance adjustable element at the current parameter value;

[0020] The operating mode of the RF power supply is set to frequency sweep, and process gas is introduced into the process chamber. The RF power supply is then turned on so that impedance matching is performed by adjusting the output frequency.

[0021] Optionally, the impedance matching network of the matching device is L-shaped, and the impedance adjustable element includes a first variable capacitor for adjusting the real part of the load impedance and a second variable capacitor for adjusting the imaginary part of the load impedance.

[0022] The adjustment of the parameter values ​​of the impedance-adjustable element includes:

[0023] If the cutoff frequency is less than the lower limit of the tolerance range, the first variable capacitor remains unchanged, and the capacitance of the second variable capacitor is reduced.

[0024] If the cutoff frequency is greater than the upper limit of the tolerance range, the first variable capacitor remains unchanged, and the capacitance of the second variable capacitor is increased.

[0025] Optionally, the tolerance range is greater than or equal to 13.42MHz and less than or equal to 13.69MHz.

[0026] As another technical solution, the impedance matching device provided by the present invention includes a matching unit, which includes an impedance adjustable element, a frequency detection unit, and a control unit. The frequency detection unit is used to detect the cutoff frequency of the radio frequency power supply and send it to the control unit.

[0027] The control unit is used to control the matching unit and the RF power supply, to perform impedance matching between the output impedance of the RF power supply and the load impedance, and after impedance matching is achieved, to detect the cutoff frequency of the RF power supply in real time and determine whether the cutoff frequency is within a preset tolerance range; if not, the control unit adjusts the parameter value of the impedance adjustable element of the matching unit and returns to determine whether the cutoff frequency is within the preset tolerance range.

[0028] Optionally, the impedance matching network of the matching device is L-shaped, and the impedance adjustable element includes a first variable capacitor for adjusting the real part of the load impedance and a second variable capacitor for adjusting the imaginary part of the load impedance.

[0029] The control unit is configured to keep the first variable capacitor unchanged and decrease the capacitance of the second variable capacitor when the cutoff frequency is less than the lower limit of the tolerance range; and to keep the first variable capacitor unchanged and increase the capacitance of the second variable capacitor when the cutoff frequency is greater than the upper limit of the tolerance range.

[0030] As another technical solution, the semiconductor process equipment provided by the present invention includes a process chamber, an inlet device, and an upper electrode device. The inlet device is used to introduce process gas into the process chamber. The upper electrode device includes an upper electrode and a radio frequency power supply, and also includes the impedance matching device provided by the present invention. The radio frequency power supply is electrically connected to the upper electrode through the impedance matching device.

[0031] The present invention has the following beneficial effects:

[0032] In the impedance matching method and apparatus provided by this invention, after impedance matching is achieved, the cutoff frequency of the RF power supply is detected in real time, and it is determined whether the cutoff frequency is within a preset tolerance range. If not, the parameter value of the impedance adjustable element of the matching device is adjusted until the cutoff frequency meets the above tolerance range. This allows the cutoff frequency of the RF power supply to be controlled within the tolerance range, increases the frequency adjustable window, avoids the problem of ineffective reduction of reflected power, and thus improves the stability of chamber operation and process results.

[0033] The semiconductor process equipment provided by this invention, by employing the impedance matching device provided by this invention, can control the cutoff frequency of the RF power supply within the tolerance range, increase the adjustable window of the frequency, avoid the problem of the reflection power not being effectively reduced, thereby improving the stability of the chamber operation and the stability of the process results. Attached Figure Description

[0034] Figure 1 The graph shows the change in cutoff frequency during impedance matching using existing impedance matching methods.

[0035] Figure 2 This is a schematic diagram of the frequency-adjustable window after impedance matching is achieved using existing impedance matching methods.

[0036] Figure 3 A flowchart of an impedance matching method provided in an embodiment of the present invention;

[0037] Figure 4 Another flowchart of the impedance matching method provided in the embodiments of the present invention;

[0038] Figure 5 A flowchart of step S1 of the impedance matching method provided in an embodiment of the present invention;

[0039] Figure 6 The equivalent circuit diagram of the impedance matching network of the matching device used in the embodiments of the present invention is shown below.

[0040] Figure 7 This is a schematic diagram showing the change curve of the cutoff frequency during impedance matching using the impedance matching method provided in this embodiment of the invention, and the frequency adjustable window after impedance matching is achieved.

[0041] Figure 8 This is another flowchart of the impedance matching method provided in the embodiments of the present invention. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions of the present invention, the impedance matching method and apparatus, and semiconductor process equipment provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0043] When using an RF power supply to apply RF power to a process chamber through a matching adapter to excite the process gas in the chamber to form plasma, if the chamber load impedance is mismatched with the output impedance of the RF power supply (i.e., the load impedance is not equal to the internal resistance of the RF power supply (usually 50Ω), a portion of the RF power output will not be absorbed by the process chamber and will be consumed in the transmission loop, known as reflected power. Excessive reflected power can affect plasma ignition in the process chamber and may also affect the process results. To address this, a matching adapter can be used for impedance matching. However, due to limitations in the torque, speed, and matching algorithm of mechanical components, impedance matching using only a matching adapter is not suitable for processes with short processing times, such as the PEALD process. In this case, an RF power supply with a frequency sweep function can be used in conjunction. That is, while keeping the adjustable impedance element in the matching adapter in a suitable position to keep the impedance of the impedance matching network constant, the output frequency is rapidly adjusted according to the changes in the chamber load until the reflected power is reduced to within the allowable range, ultimately achieving impedance matching of the RF loop and completing maximum power transmission.

[0044] Figure 1 This is a graph showing the change in cutoff frequency during impedance matching using existing methods. Figure 1 As shown, existing impedance matching methods include:

[0045] In impedance matching stage A, the operating mode of the RF power supply is set to Auto Frequency Tuning, and the operating mode of the matching device is set to Auto. Then, the process is carried out, that is, the process gas is introduced into the process chamber, and the RF power supply is turned on to excite the process gas in the process chamber to form plasma.

[0046] In sweep mode, the RF power supply can quickly adjust the output frequency according to changes in the chamber load impedance. The adjustable range of this output frequency has an upper limit of 14.238MHz (Max) and a lower limit of 12.882MHz (Min), with an initial value of 13.56MHz (Center). Simultaneously, in automatic mode, the matching unit uses an automatic matching algorithm to adjust the parameter values ​​of the impedance-adjustable components based on changes in the chamber load impedance. Ultimately, through the RF power supply's sweep and the matching unit's automatic matching, impedance matching is achieved. When the parameter values ​​of the impedance-adjustable components (e.g., the position of the variable capacitor's drive motor) approach stability, the current parameter values ​​of the impedance-adjustable components are stored, and the RF power supply is turned off. Figure 1 As shown, during impedance matching stage A, the output frequency will fluctuate slightly between the initial value Center and the upper limit value Max, or between the initial value Center and the lower limit value Min.

[0047] In impedance matching phase B, the matching unit's operating mode is set to manual, and the parameter values ​​of the impedance-adjustable components are set to the stored current parameter values ​​and maintained. The process then continues, involving the introduction of process gas into the process chamber and the activation of the RF power supply to excite the process gas and form plasma. The reflected power is checked to determine if it meets the requirements. If yes, the process ends; otherwise, it returns to impedance matching phase A to re-obtain the aforementioned current parameter values. During impedance matching phase B, the output frequency of the RF power supply remains essentially stable at frequency value F or frequency value F', with a deviation ΔF from the initial value Center.

[0048] Due to the aforementioned offset ΔF, the adjustable window of the RF power supply's output frequency is reduced, such as... Figure 2 As shown, the adjustable window is reduced from "13.56~14.238MHz" to "frequency value F'~14.238MHz" (or from 12.882MHz~13.56MHz to 12.882MHz~frequency value F). Reducing the adjustable window presents the following problems:

[0049] Firstly, during plasma ignition, plasma state fluctuations (mainly manifested as changes in chamber load impedance) can occur. In this case, the RF power supply adjusts the output frequency in real time to ensure the reflected frequency meets requirements. However, due to the reduced adjustable window, the probability of the frequency approaching the upper or lower limit of the adjustable window increases, making it impossible to effectively reduce the reflected power. This leads to poor chamber operational stability and may also affect process results such as film uniformity and film density. Especially for PEALD processes with shorter ignition times (0.2–1 s), plasma state fluctuations account for a larger proportion of the entire ignition process, resulting in a greater impact on chamber operational stability and severely affecting the process structure. Therefore, existing impedance matching methods are not suitable for short-time PEALD processes.

[0050] Secondly, as the process time accumulates, the dielectric film attached to the surface of the process components in the process chamber becomes thicker (equivalent to capacitance). This increased thickness alters the chamber's load impedance, necessitating continuous increases (or decreases) in the RF power supply frequency for impedance matching. However, when the frequency approaches the upper limit (Max, 14.238MHz) or lower limit (Min, 12.882MHz), the reflected power can no longer be effectively reduced, and the chamber reaches its operational limit, failing to meet process requirements. This necessitates cleaning or chamber opening maintenance. The reduction in the adjustable window increases the probability of the frequency approaching the upper or lower limit of the adjustable window, thus shortening the chamber's periodic maintenance cycle and indirectly impacting production capacity.

[0051] To resolve the above issues, please refer to Figure 3 This invention provides an impedance matching method applied to the process chamber of a semiconductor device, comprising:

[0052] S1. Perform impedance matching between the output impedance of the RF power supply and the load impedance;

[0053] S2. After impedance matching is achieved, the cutoff frequency of the RF power supply is detected in real time.

[0054] S3. Determine whether the cutoff frequency is within the preset tolerance range; if yes, the process ends; if no, proceed to step S4.

[0055] S4. Adjust the parameter value of the impedance adjustable element of the matching circuit, and return to step S3 above.

[0056] After impedance matching is achieved, the cutoff frequency of the RF power supply is detected in real time, and it is determined whether the cutoff frequency is within the preset tolerance range. If not, the parameter value of the impedance adjustable element of the matching device is adjusted until the cutoff frequency meets the above tolerance range. This allows the cutoff frequency of the RF power supply to be controlled within the tolerance range, increases the frequency adjustment window, avoids the problem of the reflected power not being effectively reduced, and thus improves the stability of the chamber operation and the stability of the process results.

[0057] In practical applications, the aforementioned tolerance range can be set according to the adjustable frequency window. For example, if the upper limit of the adjustable frequency window is 14.238MHz and the lower limit is 12.882MHz, the range closest to the middle value between the upper and lower limits can be selected as the tolerance range. Specifically, if the middle value is selected as 13.56MHz, the tolerance range can be 3.56±0.1325MHz, that is, the tolerance range is greater than or equal to 13.42MHz and less than or equal to 13.69MHz. However, this embodiment of the invention is not limited to this. In practical applications, the aforementioned tolerance range can be set according to specific needs.

[0058] In some alternative embodiments, the process chamber is pre-cleaned or a bare process chamber that has not been used in a process is purged for an extended period of time before the process is carried out, in order to avoid particles affecting the process.

[0059] In some alternative embodiments, such as Figure 4 As shown, before step S1 above, the procedure also includes:

[0060] S0. Deposit an insulating film on the surface of components exposed to the plasma environment within the process chamber.

[0061] The surfaces of components exposed to the plasma environment within the aforementioned process chamber generally include the inner surfaces of process assemblies within the chamber, such as linings. Taking the process chamber in a bare state as an example, the surfaces of components exposed to the plasma environment within the process chamber may be uneven due to limitations in processing precision and technology, resulting in concave or granular surfaces. In this case, when the plasma within the chamber is ignited, some charged particles will adhere to the surfaces of the components exposed to the plasma environment within the process chamber and gradually accumulate to form a floating potential, causing an uneven electric field. This makes it difficult to stabilize the generated plasma state, and the chamber load impedance will fluctuate abnormally, which is not conducive to impedance matching adjustment. To address this issue, an insulating film is deposited on the surface of the component exposed to the plasma environment within the process chamber in step S0. This insulating film uniformly covers the surface, improving the smoothness of the exposed surface and effectively reducing unevenness, pits, and particles. This provides a stable chamber environment for plasma ignition, enhances plasma stability, reduces fluctuations in chamber load impedance, and facilitates impedance matching. Furthermore, it allows for smaller and faster adjustment of the matching device's capacitor position, thus improving its adjustment accuracy. Therefore, the impedance matching method provided by this invention is particularly suitable for PEALD processes with shorter ignition times (0.2–1 s), thereby expanding its application range.

[0062] In practical applications, step S0 can be performed at regular intervals. For example, step S0 can be performed on a process chamber after pre-cleaning or on a process chamber in a bare state that has not been processed. Alternatively, step S0 can be performed before each step S1.

[0063] To prevent the insulating film from reacting with the process gas, the insulating film is made of an insulating material such as silicon dioxide. Optionally, the thickness of the insulating film is greater than or equal to... and less than or equal to

[0064] There are various ways to perform impedance matching between the output impedance and load impedance of the RF power supply in step S1 above. In some optional embodiments, such as... Figure 5 As shown, step S1 above includes:

[0065] S11. Set the operating mode of the RF power supply to fixed frequency so that the output frequency of the RF power supply is maintained at the above initial value.

[0066] The initial value mentioned above is typically a value between the upper limit (Max) and lower limit (Min) of the adjustable frequency window (e.g., 14.238MHz) and within the aforementioned tolerance range. This value is usually chosen as an intermediate value, such as 13.56MHz, but this embodiment of the invention is not limited to this. In practical applications, the initial value can be set according to specific needs.

[0067] S12. Set the matching mode of the matching unit to automatic matching mode, introduce process gas into the process chamber, and turn on the RF power supply (i.e. start the process) so that the matching unit uses the automatic matching algorithm to adjust the parameter value of the impedance adjustable component until impedance matching is achieved.

[0068] The aforementioned automatic matching algorithm refers to calculating the adjustment amount of the parameter value of the adjustable impedance element based on the signal detected by the sensor, and automatically adjusting the parameter value of the adjustable impedance element (such as the capacitance value or position of the adjustable capacitor) according to the adjustment amount until impedance matching is achieved.

[0069] In step S12 above, the RF power supply is set to fixed frequency mode, that is, the output frequency is always kept at the initial value (e.g., 13.56MHz), and impedance matching is performed by the matching unit alone. This not only avoids the matching disorder caused by simultaneous impedance matching through frequency sweeping by the matching unit and the RF power supply, but also improves the accuracy of the parameter values ​​of the adjustable impedance components (e.g., the capacitance value or position of the adjustable capacitor).

[0070] S13. Store the current parameter values ​​of the impedance-adjustable element, turn off the RF power supply, and stop the process gas supply.

[0071] After impedance matching is achieved through step S12 and the parameter value of the impedance adjustable element is basically stable at the current parameter value, the current parameter value of the impedance adjustable element is stored.

[0072] S14. Set the matching circuit to manual mode, and set and maintain the parameter values ​​of the impedance adjustable element at the current parameter values ​​mentioned above.

[0073] S15. Set the operating mode of the RF power supply to frequency sweep, introduce process gas into the process chamber, and turn on the RF power supply so that the RF power supply can perform impedance matching by adjusting the output frequency.

[0074] The process parameters, such as the process gas introduced and the output power of the RF power supply, in step S15 are the same as those in step S12.

[0075] In step S15 above, the matching mode is set to manual mode, that is, the parameter value of the impedance adjustable element is kept at the current parameter value, and impedance matching is performed by the RF power supply alone, so as to avoid matching disorder caused by simultaneous impedance matching through frequency sweeping by the matching unit and the RF power supply.

[0076] In some alternative embodiments, such as Figure 6 As shown, the RF power supply 1 is electrically connected to the upper electrode (e.g., coil or electrode plate) of the process chamber 3 via a matching unit 2. The impedance matching network of the matching unit 2 is L-shaped. The impedance adjustable element of the matching unit includes a first variable capacitor C1 for adjusting the real part of the load impedance and a second variable capacitor C2 for adjusting the imaginary part of the load impedance. In some optional embodiments, the matching unit includes a sensor, an impedance variable element, an execution unit, and a control module. The sensor is used to detect voltage and current signals on the RF transmission line in real time and send them to the control unit. The impedance variable element includes a first variable capacitor C1 and a second variable capacitor C2, and their capacitance values ​​or positions are the parameter values ​​of the adjustable element. The control module is used to control two motors to adjust the capacitance positions of the two first variable capacitors C1 and the second variable capacitor C2 respectively, so as to adjust their capacitance values ​​until impedance matching is achieved. Of course, in practical applications, the impedance matching network is not limited to L-shape; it can also be π-shape, T-shape, etc., and the corresponding impedance adjustable element can be adaptively adjusted according to the different types of impedance matching networks.

[0077] Based on an L-type impedance matching network, options include, for example... Figure 8 As shown, step S4 above includes:

[0078] If the cutoff frequency is less than the lower limit of the tolerance range, proceed to step S41;

[0079] If the cutoff frequency is greater than the upper limit of the tolerance range, proceed to step S42;

[0080] S41. Keep the first variable capacitor C1 unchanged and decrease the capacitance value of the second variable capacitor C2.

[0081] S42. Keep the first variable capacitor C1 unchanged and increase the capacitance of the second variable capacitor C2.

[0082] The single adjustment amount of the capacitance value of the second variable capacitor C2 can be set according to specific circumstances.

[0083] like Figure 6 As shown, the chamber load impedance Z2 satisfies the following formula:

[0084]

[0085] Where R is the equivalent resistance of the chamber at plasma ignition; and C is the equivalent capacitance of the chamber at plasma ignition.

[0086] The cutoff frequency F satisfies the following formula:

[0087] ω=2πF

[0088] Based on the above two formulas, it can be seen that if the capacitance of the second variable capacitor C2 is increased (or decreased), the cutoff frequency F needs to be reduced (or increased) accordingly to ensure that the chamber load impedance Z2 remains unchanged. That is, the capacitance of the second variable capacitor C2 is inversely proportional to the cutoff frequency F.

[0089] Based on L-type impedance matching networks, such as Figure 7 As shown, step S1 corresponds to the impedance matching period C. The initial value is a value between the upper limit Max (e.g., 14.238MHz) and the lower limit Min (e.g., 12.882MHz) of the adjustable frequency window. This value is usually chosen to be the middle value, such as 13.56MHz. During the impedance matching period C, when the plasma is ignited, the cutoff frequency of the RF power supply increases from 13.56MHz and continues to fluctuate until impedance matching is completed. After the reflected power decreases to within the allowable range, the cutoff frequency of the RF power supply will stabilize around the frequency value F1 with slight fluctuations. There will be a deviation ΔF1 between the frequency value F1 and the initial value (13.56MHz). Sometimes, the frequency value F1 may even approach the upper limit Max (e.g., 14.238MHz), which seriously narrows the frequency adjustment window in subsequent processes. To solve this problem, after impedance matching is achieved, the cutoff frequency of the RF power supply is detected in real time, and it is determined whether the cutoff frequency is within the tolerance range of the preset initial value. If not, the parameter value of the impedance adjustable element of the matching device is adjusted until the cutoff frequency meets the above tolerance range. Specifically, such as Figure 7 As shown, step S4 corresponds to the cutoff frequency adjustment period D. By adjusting the parameter value of the impedance adjustable element of the matching device, the cutoff frequency can be reduced to the frequency value F2, which is close to the initial value (13.56MHz), that is, within the tolerance range of the initial value. The frequency adjustment window is significantly increased, which can effectively cope with the plasma state fluctuations of tens or hundreds of milliseconds during process operation (especially at the start and end of ignition). This can improve the stability of chamber operation and process results, and is especially suitable for short-time processes, with a wider range of applications.

[0090] Furthermore, as the frequency adjustable window increases, the thickness of the film attached inside the cavity can be increased, and the continuous operating time of the cavity can be further extended. For example, previously, a film with a PEALD cavity deposition thickness of 1 μm required cleaning or maintenance of the cavity. However, by using the impedance matching method provided in this embodiment of the invention, the PEALD cavity deposition thickness can be increased by 1.3 to 1.5 μm, thereby reducing the number of maintenance cycles and increasing production capacity.

[0091] As another technical solution, this embodiment of the invention also provides an impedance matching device, which includes a matching unit, an impedance adjustable element, a frequency detection unit, and a control unit. The frequency detection unit is used to detect the cutoff frequency of the radio frequency power supply and send it to the control unit. The control unit is used to control the matching unit and the radio frequency power supply to perform impedance matching between the output impedance of the radio frequency power supply and the load impedance. After impedance matching is achieved, the control unit detects the cutoff frequency of the radio frequency power supply in real time and determines whether the cutoff frequency is within the tolerance range of a preset initial value. If not, the control unit adjusts the parameter value of the impedance adjustable element of the matching unit and returns to determine whether the cutoff frequency is within the preset tolerance range.

[0092] In some optional embodiments, the impedance matching network of the matching device is L-shaped, and the impedance adjustable element of the matching device includes a first variable capacitor for adjusting the real part of the load impedance and a second variable capacitor for adjusting the imaginary part of the load impedance; the control unit is used to keep the first variable capacitor unchanged and decrease the value of the second variable capacitor when the cutoff frequency is less than the lower limit of the tolerance range; and to keep the first variable capacitor unchanged and increase the value of the second variable capacitor when the cutoff frequency is greater than the upper limit of the tolerance range.

[0093] In summary, the impedance matching method and apparatus provided in this embodiment of the invention, after impedance matching is achieved, detects the cutoff frequency of the RF power supply in real time and determines whether the cutoff frequency is within a preset tolerance range; if not, adjusts the parameter value of the impedance adjustable element of the matching device until the cutoff frequency meets the above tolerance range, thereby controlling the cutoff frequency of the RF power supply within the tolerance range, increasing the frequency adjustable window, avoiding the problem of the reflection power not being effectively reduced, and thus improving the stability of the chamber operation and the stability of the process results.

[0094] As another technical solution, this embodiment of the invention also provides a semiconductor process apparatus, including a process chamber, an inlet device, and an upper electrode device. The inlet device is used to introduce process gas into the process chamber. The upper electrode device includes an upper electrode and a radio frequency power supply. The semiconductor process apparatus also includes the impedance matching device provided in this embodiment of the invention. The radio frequency power supply is electrically connected to the upper electrode through the impedance matching device.

[0095] The semiconductor process equipment provided in this embodiment of the invention, by employing the impedance matching device provided in this embodiment of the invention, can control the cutoff frequency of the radio frequency power supply within the tolerance range, increase the adjustable window of the frequency, avoid the problem that the reflected power cannot be effectively reduced, thereby improving the stability of the chamber operation and the stability of the process results.

[0096] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An impedance matching method applied to the process chamber of a semiconductor device, characterized in that, include: Impedance matching is performed between the output impedance and the load impedance of the RF power supply. After impedance matching is achieved, the cutoff frequency of the RF power supply is detected in real time. Determine whether the cutoff frequency is within the preset tolerance range; If not, adjust the parameter value of the impedance adjustable element of the matching circuit, and return to determine whether the cutoff frequency is within the preset tolerance range. The impedance matching between the output impedance of the RF power supply and the load impedance includes: The operating mode of the RF power supply is set to fixed frequency to maintain the output frequency of the RF power supply at an initial value, which is within the tolerance range. Set the matching unit to automatic matching mode, introduce process gas into the process chamber, and turn on the RF power supply so that the matching unit uses an automatic matching algorithm to adjust the parameter value of the impedance-adjustable element until impedance matching is achieved.

2. The impedance matching method according to claim 1, characterized in that, Before performing impedance matching between the output impedance of the RF power supply and the load impedance, the following steps are also included: An insulating film is deposited on the surface of the components exposed to the plasma environment within the process chamber.

3. The impedance matching method according to claim 2, characterized in that, The insulating film comprises silicon dioxide.

4. The impedance matching method according to claim 2, characterized in that, The thickness of the insulating film is greater than or equal to and less than or equal to 5. The impedance matching method according to any one of claims 1-4, characterized in that, The impedance matching between the output impedance of the RF power supply and the load impedance also includes: Store the current parameter value of the impedance-adjustable element, turn off the RF power supply, and stop the process gas from being introduced; Set the operating mode of the matching device to manual mode, and set and maintain the parameter value of the impedance adjustable element at the current parameter value; The operating mode of the RF power supply is set to frequency sweep, and process gas is introduced into the process chamber. The RF power supply is then turned on so that impedance matching is performed by adjusting the output frequency.

6. The impedance matching method according to any one of claims 1-4, characterized in that, The impedance matching network of the matching device is L-shaped, and the impedance adjustable element includes a first variable capacitor for adjusting the real part of the load impedance and a second variable capacitor for adjusting the imaginary part of the load impedance. The adjustment of the parameter values ​​of the impedance-adjustable element includes: If the cutoff frequency is less than the lower limit of the tolerance range, the first variable capacitor remains unchanged, and the capacitance of the second variable capacitor is reduced. If the cutoff frequency is greater than the upper limit of the tolerance range, the first variable capacitor remains unchanged, and the capacitance of the second variable capacitor is increased.

7. The impedance matching method according to claim 1, characterized in that, The tolerance range is greater than or equal to 13.42MHz and less than or equal to 13.69MHz.

8. An impedance matching device, comprising a matching unit, the matching unit including an impedance adjustable element, characterized in that, It also includes a frequency detection unit and a control unit, wherein the frequency detection unit is used to detect the cutoff frequency of the radio frequency power supply and send it to the control unit; The control unit controls the matching unit and the RF power supply, performs impedance matching between the output impedance of the RF power supply and the load impedance, and after impedance matching is achieved, detects the cutoff frequency of the RF power supply in real time and determines whether the cutoff frequency is within a preset tolerance range; if not, it adjusts the parameter value of the impedance adjustable element of the matching unit and returns to determine whether the cutoff frequency is within the preset tolerance range. Impedance matching between the output impedance and load impedance of the RF power supply includes: The operating mode of the RF power supply is set to fixed frequency to maintain the output frequency of the RF power supply at an initial value, which is within the tolerance range. Set the matching unit to automatic matching mode, introduce process gas into the process chamber, and turn on the RF power supply so that the matching unit uses an automatic matching algorithm to adjust the parameter value of the impedance-adjustable element until impedance matching is achieved.

9. The impedance matching device according to claim 8, characterized in that, The impedance matching network of the matching device is L-shaped, and the impedance adjustable element includes a first variable capacitor for adjusting the real part of the load impedance and a second variable capacitor for adjusting the imaginary part of the load impedance. The control unit is used to keep the first variable capacitor unchanged and reduce the capacitance value of the second variable capacitor when the cutoff frequency is less than the lower limit of the tolerance range. When the cutoff frequency is greater than the upper limit of the tolerance range, the first variable capacitor remains unchanged, and the capacitance of the second variable capacitor is increased.

10. A semiconductor process apparatus, comprising a process chamber, a gas inlet device, and an upper electrode device, wherein the gas inlet device is used to introduce process gas into the process chamber; the upper electrode device comprises an upper electrode and a radio frequency power supply, characterized in that, It also includes the impedance matching device as described in claim 8 or 9, wherein the radio frequency power supply is electrically connected to the upper electrode through the impedance matching device.

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