Semiconductor process equipment, method for obtaining optimal impedance values, and sweep matching method.

Abstract

This application discloses a semiconductor process apparatus, a method for obtaining an optimal impedance value, and a sweep matching method, and belongs to the technology of semiconductor processes. The sweep matching method includes the steps of: obtaining an optimal impedance value of a variable impedance device according to the plasma etching process currently being performed; fixing the impedance of the variable impedance device to the optimal impedance value; and turning on the sweep mode of the RF power supply to achieve plasma ignition matching.

Description

[Technical Field]

[0001] This application relates to the field of semiconductor process technology, and more particularly to semiconductor process equipment, a method for obtaining an optimal impedance value, and a sweep matching method. [Background technology]

[0002] In plasma etching equipment, the RF power supply typically provides an electromagnetic field environment to free electrons, allowing them to gain more energy. According to transmission line theory, impedance matching is necessary to ensure that the RF energy is absorbed to the maximum extent by the plasma during the RF energy transmission process of the RF power supply. Currently, most plasma etching equipment typically employs the following three methods for impedance matching: Method 1: The back-end impedance of the RF power supply is adjusted in real time by adding an impedance matcher, which is an automatically adjustable matching network, between the RF power supply and the plasma. This method has two main drawbacks: 1. The matching time is long (in the range of 0.5s to 2s), because the impedance matcher adjusts the position of the capacitor by rotating a stepping motor, and since the stepping motor is a mechanical structure, the adjustment speed is slow. 2. Under the same pressure, power, and gas type conditions, there is a large variation in the time required to repeat plasma ignition matching, and the matching time does not match because there are multiple matching paths in the matcher in each ignition matching process. Method 2: Impedance matching is performed by automatically adjusting the center frequency output by an RF power supply with a sweep function. While this method offers fast matching speed, the bandwidth supported by conventional RF power supplies is narrow (the center frequency bandwidth is 13.56 MHz ± 5%), resulting in a very small impedance range that can be matched by sweeping the RF power supply, making it insufficient to complete plasma ignition matching tasks under various conditions. Method 3: Impedance matching is completed by combining an RF power supply with a sweep function and an impedance matcher. This method, in which the RF power supply with a sweep function and the impedance matcher work in conjunction, not only allows for rapid completion of the plasma ignition matching process but also enables the completion of plasma ignition matching tasks under various conditions, and is therefore increasingly used for impedance matching in plasma etching equipment.

[0003] However, in actual application processes, the impedance matching method of method 3 described above is prone to causing the signal output from the RF power supply to oscillate due to the inappropriate load impedance of the RF power supply, and furthermore, it can lead to a failure of sweep matching of the RF power supply, i.e., a failure of plasma ignition. [Overview of the project] [Problems that the invention aims to solve]

[0004] The embodiment of the present invention provides a semiconductor process apparatus, a method for obtaining an optimal impedance value, and a sweep matching method, which aim to solve the technical problems of conventional methods that complete impedance matching by combining an RF power supply with a sweep function and an impedance matcher, where the load impedance of the RF power supply is inappropriate, which easily causes the signal output from the RF power supply to oscillate and further leads to the failure of sweep matching of the RF power supply. [Means for solving the problem]

[0005] In a first aspect, an embodiment of the present invention provides a method for obtaining an optimal impedance value for an impedance matcher, the impedance matcher being used to adjust the back-end impedance of an RF power supply in real time, the impedance matcher including a variable impedance device for performing impedance adjustment, the method including: adjusting the impedance of the variable impedance device to a predetermined impedance value; performing impedance matching adjustment by starting the RF power supply and, if the sweep function of the RF power supply is off, adjusting the impedance of the variable impedance device using an automatic matching algorithm; after completing the impedance matching adjustment, recording the matched impedance value of the variable impedance device at this time and turning off the RF power supply; fixing the impedance of the variable impedance device to the matched impedance value and turning on the RF power supply again; adjusting the operating frequency of the RF power supply, obtaining the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained by each adjustment, and generating a corresponding relationship curve; and, if the relationship curve satisfies predetermined requirements, recording the current matched impedance value as the optimal impedance value.

[0006] In some embodiments, the step of adjusting the operating frequency of the RF power supply includes a step of gradually changing the operating frequency of the RF power supply within an operating frequency range of the RF power supply from one of the minimum and maximum values ​​of the operating frequency range to the other of the minimum and maximum values ​​of the operating frequency range according to a first predetermined adjustment step.

[0007] In some embodiments, the predetermined requirements include that the relational curve contains an operating frequency point corresponding to the power reflection coefficient of less than 0.01, and that the relational curve does not contain a region in which the power reflection coefficient oscillates.

[0008] In some embodiments, the method further includes the steps of adjusting the operating frequency of the RF power supply, obtaining the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained by each adjustment, and generating a corresponding relationship curve, and if the relationship curve does not satisfy predetermined requirements, adjusting the matching impedance value, and after each adjustment of the matching impedance value, obtaining the relationship curve generated by adjusting the operating frequency of the RF power supply, and if the obtained relationship curve satisfies predetermined requirements, recording the current matching impedance value as the optimal impedance value.

[0009] In some embodiments, the variable impedance device includes a first variable capacitor and a second variable capacitor, the step of adjusting the variable impedance device to a predetermined impedance value includes the step of adjusting the first variable capacitor to a first predetermined capacitor position and adjusting the second variable capacitor to a second predetermined capacitor position, the step of recording the matched impedance value of the variable impedance device at the time after the impedance matching adjustment is completed includes the step of recording the first capacitor position of the first variable capacitor and the second capacitor position of the second variable capacitor at the time after the impedance matching adjustment is completed, the step of fixing the impedance of the variable impedance device to the matched impedance value includes the step of fixing the first variable capacitor to the first capacitor position and fixing the second variable capacitor to the second capacitor position, and the step of recording the current matched impedance value as the optimal impedance value includes the step of recording the current first capacitor position as the first optimal capacitor position and recording the current second capacitor position as the second optimal capacitor position.

[0010] In some embodiments, if the relationship curve does not satisfy a predetermined requirement, the method further includes a step of gradually decreasing the current value of the first capacitor position according to a second predetermined adjustment step, and gradually decreasing the current value of the second capacitor position according to a third predetermined adjustment step, thereby adjusting the matching impedance value.

[0011] In some embodiments, the first variable capacitor is connected between the output terminal of the RF power supply and ground, the second variable capacitor is connected between the output terminal of the RF power supply and the load, and the third predetermined adjustment step is greater than the second predetermined adjustment step.

[0012] In a second aspect, an embodiment of the present invention provides a sweep matching method for an RF power supply of a semiconductor process apparatus, the semiconductor process apparatus comprising an RF power supply having a sweep function and an impedance matcher for adjusting the back-end impedance of the RF power supply in real time, the impedance matcher comprising a variable impedance device for performing impedance adjustment, the sweep matching method comprising the steps of obtaining the optimal impedance value of the variable impedance device using the method, depending on the plasma etching process currently being performed, fixing the impedance of the variable impedance device to the optimal impedance value, and turning on the sweep mode of the RF power supply to achieve plasma ignition matching.

[0013] In some embodiments, the step of obtaining the optimal impedance value of the variable impedance device includes the step of determining whether the plasma etching process to be performed is an existing plasma etching process, and if the plasma etching process to be performed is not an existing plasma etching process, the step of obtaining the optimal impedance value of the variable impedance device and recording and storing it in a predetermined process parameter list.

[0014] In some embodiments, the step of determining whether the plasma etching process to be executed is an existing plasma etching process includes: determining whether the plasma etching process to be executed is an existing plasma etching process depending on whether the plasma etching process to be executed is stored in the predetermined process parameter list; determining that the plasma etching process to be executed is an existing plasma etching process if the plasma etching process to be executed is stored in the predetermined process parameter list; and determining that the plasma etching process to be executed is not an existing plasma etching process if the plasma etching process to be executed is not stored in the predetermined process parameter list.

[0015] In some embodiments, the step of determining whether the plasma etching process to be performed is an existing plasma etching process includes: determining whether the plasma etching process to be performed is an existing plasma etching process based on whether the optimal impedance value of the plasma etching process to be performed is in the default state in the predetermined process parameter list; determining that the plasma etching process to be performed is not an existing plasma etching process if the optimal impedance value of the plasma etching process to be performed is in the default state; and determining that the plasma etching process to be performed is an existing plasma etching process if the optimal impedance value of the plasma etching process to be performed is not in the default state.

[0016] In some embodiments, the step of obtaining the optimal impedance value of the variable impedance device further includes, if the plasma etching process to be performed is an existing plasma etching process, finding the plasma etching process to be performed and the correspondingly stored optimal impedance value from a predetermined process parameter list.

[0017] In a third aspect, an embodiment of the present invention provides a semiconductor process apparatus comprising: an RF power supply having a sweep function; an impedance matcher for adjusting the backend impedance of the RF power supply in real time; and a controller, wherein the impedance matcher includes a variable impedance device for performing impedance adjustment; and the controller includes a processor; a memory; and a program stored in the memory and executable by the processor, wherein when the program is executed by the processor, it realizes a step of a method for obtaining the optimal impedance value of the impedance matcher or performs a step of a sweep matching method. [Effects of the Invention]

[0018] In this application, when the semiconductor process equipment performs sweep matching of the RF power supply, first, according to specific process conditions (that is, the current plasma etching process to be executed), the optimal impedance value of the variable impedance device can be found. The optimal impedance value can ensure that the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient meets predetermined requirements. That is, by finding an appropriate load for the RF power supply, when the RF power supply performs a sweep, it is ensured that the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient satisfies a one-to-one correspondence change relationship. In this way, after fixing the impedance of the variable impedance device to the optimal impedance value, the sweep mode of the RF power supply can be turned on. That is, the sweep mode of the power supply is turned on at the appropriate load, the plasma is quickly ignited, the occurrence of the frequency oscillation region is avoided, and further plasma ignition matching is achieved. As can be seen from the above, the technical solution effectively avoids the problem that the signal output from the RF power supply vibrates, improves the success rate of the sweep matching of the RF power supply, and further improves the reproducibility and stability of the process results.

[0019] Hereinafter, specific embodiments of the present application will be described in detail with reference to the drawings, whereby the technical solution of the present application and its beneficial effects will become clear.

Brief Description of the Drawings

[0020] [Figure 1] It is an operation principle diagram for completing impedance matching by a conventional method of combining an RF power supply having a sweep function and an impedance matcher. [Figure 2] It is a relationship curve diagram between the operating frequency of the RF power supply and the power reflection coefficient when the sweep of the RF power supply shown in FIG. 1 fails. [Figure 3] It is an enlarged schematic diagram of part I of the relationship curve diagram between the operating frequency of the RF power supply and the power reflection coefficient shown in FIG. 2. [Figure 4] It is an operation principle diagram of the power load of the RF power supply shown in FIG. 1. [Figure 5]This is a flowchart of a method for obtaining the optimal impedance value of an impedance matching device according to an embodiment of the present invention. [Figure 6] This is another flowchart of a method for obtaining the optimal impedance value of an impedance matching device according to an embodiment of the present invention. [Figure 7] This is a flowchart of the sweep matching method for a semiconductor process apparatus according to an embodiment of the present invention. [Figure 8] Figure 7 shows the relationship between the operating frequency of the RF power supply and the power reflection coefficient in the sweep matching method. [Figure 9] Figure 7 is a schematic diagram of the structure of an L-type impedance matcher in the sweep matching method shown. [Figure 10] Figure 7 is a flowchart of step S110 of the sweep alignment method. [Modes for carrying out the invention]

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the drawings. Clearly, the embodiments described are only a selection of the embodiments of this application, not all of them. Any other embodiments that a person skilled in the art can obtain without creative work based on the embodiments of this application are all within the scope of protection of this application. To the extent that they do not contradict each other, the embodiments and their technical features described below can be combined with each other.

[0022] In related technologies, plasma etching equipment completes impedance matching by combining an RF power supply with a sweep function and an impedance matcher. The operating principle is typically divided into two stages, as shown in Figure 1. In the first stage, the variable capacitor of the impedance matcher is fixed, and the sweep function of the RF power supply is turned on. At this time, the power detection module of the RF power supply uses a detection control circuit to detect the incident power and reflected power using a high-frequency measuring inductor, calculates the power reflection coefficient Γ, and provides this signal to the frequency control module. The frequency control module takes the reflection coefficient Γ as an input variable, calculates the frequency adjustment amount in combination with a sweep matching algorithm, and feeds the frequency adjustment amount back to the RF signal source, realizing an impedance matching feedback process that automatically adjusts the operating frequency of the RF power supply. This stage performs primary matching using the sweep function of the RF power supply, and at this time, the reflected power in the transmission line can be reduced to 5% to 10% of the incident power, supporting rapid plasma ignition. In the second stage, the operating frequency of the RF power supply is fixed, and the automatic adjustment mode of the impedance matcher is turned on. At this time, the impedance matcher's sensor detects the voltage V and current I of the signal in the transmission line. Digital signal processing allows the amplitude Mag and phase Phase information of the input impedance from the input terminal to the output terminal of the impedance matcher to be obtained as input variables for the automatic matching algorithm. The controller, in combination with the automatic matching algorithm, calculates the adjustment amount for the stepping motor according to the variables provided by the sensor. Furthermore, by changing the capacitance values ​​of the variable capacitor devices C1 and C2 and fine-tuning the positions of the capacitors C1 and C2, the reflected power in the transmission line is reduced to less than 1%, completing the final matching. As can be seen from the above, this method of combining an RF power supply with a sweep function and an impedance matcher not only allows for the rapid completion of the plasma ignition matching process but also enables the completion of plasma ignition matching tasks in different situations, and is therefore increasingly used in impedance matching for plasma etching equipment.

[0023] However, as can be seen from actual application processes, this impedance matching method still has the following problems. When plasma ignition is achieved using the sweep function of the RF power supply, the RF power supply adjusts its output frequency by determining the relationship between the power reflection coefficient and the operating frequency, and finally finds the operating frequency point with the lowest power reflection coefficient to complete the plasma ignition matching process. Therefore, in order to achieve a rapid and stable plasma ignition process, it is necessary to ensure that when the RF power supply performs sweep matching, there is a one-to-one correspondence between the power reflection coefficient in the line and the operating frequency of the RF power supply. However, in the actual impedance matching process, if the load impedance of the RF power supply is inappropriate, the operating frequency (Frequency) and power reflection coefficient (Γ) of the RF power supply shown in Figures 2 and 3 will be affected. 2 A relationship curve appears, and the corresponding power reflection coefficient (Γ) appears in the 13.4MHz to 13.5MHz operating frequency range of the RF power supply. 2 It was clearly observed that the RF power supply vibrates, and therefore, when the RF power supply's operating frequency enters this region during the sweep process, it cannot escape, and furthermore, it is not possible to reduce and fix the reflected power to 5% to 10% of the incident power. As a result, the sweep matching of the RF power supply fails, i.e., plasma ignition fails.

[0024] Furthermore, a factor that can cause the sweep matching of the above RF power supply to fail is that when the output terminal of the RF power supply is connected to a different load, oscillation phenomena may be present in the signal output from the RF power supply. As shown in Figure 4, the voltage signal in the line is the incident voltage wave U i (z) and reflected voltage wave U r (z) consists of U r (z) is the reflection coefficient of the load Γ L In relation to this, the power supply load Z L If the load's reflection coefficient Γ is different, Lare different, whereby the amplitudes (U1, U2) of the voltage waves in the MOS transistor M1 of the power amplifier are somewhat different. At this time, if overvoltage, overcurrent, loss protection, etc. of the MOS transistor M1 are triggered and the MOS transistor M1 cannot operate normally, the oscillation phenomenon shown in FIGS. 2 and 3 will occur in the signal output by the RF power supply.

[0025]

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Number

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[0026] As shown in FIG. 4, the power load Z of the RF power supply L consists of two parts. The first part is the impedance Z of the matching network of the impedance matcher M , and the second part is the impedance Z of the plasma P . Generally, when performing sweep matching using the sweep function of the RF power supply, the variable capacitors C1 and C2 of the impedance matcher are fixed at the positions (C1_a, C2_a) after plasma ignition matching. However, if the capacitor positions are inappropriate, the power load Z L at this time will cause the oscillation of the signal output by the RF power supply, and ultimately the sweep matching of the RF power supply may fail.

[0027] Based on this, in the conventional method of completing impedance matching by combining an RF power supply with a sweep function and an impedance matcher, due to the inappropriate load impedance of the RF power supply, the phenomenon that the signal output from the RF power supply vibrates easily occurs, and further causes the problem that the sweep matching of the RF power supply fails. Therefore, it is necessary to provide a solution for a new RF power supply sweep matching method.

[0028] In one embodiment, as shown in Figure 5, an embodiment of the present invention provides a method for obtaining an optimal impedance value for an impedance matcher, which is used to adjust the backend impedance of an RF power supply in real time and to rapidly complete plasma ignition matching of a semiconductor process apparatus in combination with the RF power supply, the impedance matcher includes a variable impedance device for making impedance adjustments, and the method may specifically include the following steps.

[0029] Step S11: Adjust the impedance of the variable impedance device to a predetermined impedance value.

[0030] It can be understood that, in the embodiments of the present invention, the purpose of obtaining the optimal impedance value of the impedance matcher is primarily to perform a sweep matching service to the RF power supply of a subsequent semiconductor process equipment. Therefore, the specific structure of the impedance matcher can be seen in Figures 1 and 4, namely, the impedance matcher includes a variable impedance device for impedance adjustment. Furthermore, the variable impedance device may specifically include a first variable capacitor C1 and a second variable capacitor C2. In this case, obtaining the optimal impedance value of the impedance matcher should include obtaining the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2. That is, when the first variable capacitor C1 is in the first optimal capacitor position and the second variable capacitor C2 is in the second optimal capacitor position, the impedance of the variable impedance device of the impedance matcher is the optimal impedance value. To more easily find the optimal impedance values ​​of the variable impedance device (i.e., the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2), the impedance of the variable impedance device is adjusted to a reasonable impedance value before starting the search (i.e., adjusting the impedance of the variable impedance device to a predetermined impedance value may specifically include adjusting the first variable capacitor to a first predetermined capacitor position and the second variable capacitor to a second predetermined capacitor position, for example, to the (50%, 50%) position).

[0031] Step S12: The RF power supply is started, and if the sweep function of the RF power supply is off, impedance matching adjustment is performed by adjusting the impedance of the variable impedance device using an automatic matching algorithm.

[0032] One understandable point is that, after adjusting the impedance of the variable impedance device to a predetermined impedance value by the steps of the above method (i.e., adjusting the first variable capacitor C1 to a first predetermined capacitor position and adjusting the second variable capacitor C2 to a second predetermined capacitor position), impedance matching can be performed by starting the RF power supply and, if the sweep function of the RF power supply is off, adjusting the impedance of the variable impedance device using an automatic matching algorithm. In other words, impedance matching is completed by adjusting the impedance of the variable impedance device using an automatic adjustment mode inherent to the impedance matcher itself (specifically, adjusting the capacitor positions of the first variable capacitor C1 and the second variable capacitor C2, i.e., adjusting the specific capacitance values ​​of the first variable capacitor C1 and the second variable capacitor C2, respectively).

[0033] Step S13: After completing the impedance matching adjustment, record the matched impedance value of the variable impedance device at this time and turn off the RF power supply.

[0034] One understandable point is that after the impedance matcher completes the corresponding impedance matching adjustment by the steps of the method described above, the system can automatically record the matching impedance value of the variable impedance device at this time (and can also record the first capacitor position of the first variable capacitor C1 and the second capacitor position of the second variable capacitor C2 at this time). At the same time, since the matching impedance value of the variable impedance device at this time is recorded after the impedance matcher has completed the impedance matching adjustment, the first capacitor position of the first variable capacitor C1 at this time can specifically coincide with the matching position C1_a of the first variable capacitor C1 in the related technology, and the second capacitor position of the second variable capacitor C2 can specifically coincide with the matching position C2_a of the second variable capacitor C2 in the related technology.

[0035] Step S14: After fixing the impedance of the variable impedance device to the matched impedance value, the RF power supply is turned on again.

[0036] One understandable point is that, after obtaining the matched impedance value of the variable impedance device (or the first capacitor position of the first variable capacitor C1 and the second capacitor position of the second variable capacitor C2) by the steps of the above method, the impedance of the variable impedance device is fixed to the matched impedance value (specifically, the first variable capacitor C1 may be fixed to the first capacitor position and the second variable capacitor C2 may be fixed to the second capacitor position), and then the RF power supply is turned on again to perform the corresponding initial preparations for subsequently obtaining the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient under the current matched impedance value.

[0037] Step S15: The operating frequency of the RF power supply is adjusted, the correspondence between the operating frequency of the RF power supply obtained by each adjustment and the power reflection coefficient is acquired, and a corresponding relationship curve is generated.

[0038] In essence, the above method involves fixing the impedance of a variable impedance device to the matching impedance value (specifically, the first variable capacitor may be fixed to the first capacitor position and the second variable capacitor to the second capacitor position), turning the RF power supply on again, adjusting the operating frequency of the RF power supply, and obtaining the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained by each adjustment to generate a corresponding relationship curve. That is, each time the operating frequency of the RF power supply is adjusted and changed, the power reflection coefficient corresponding to the current operating frequency of the RF power supply is recorded once, and after multiple adjustments and recordings, the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained by each adjustment is obtained to generate a corresponding relationship curve, i.e., a relationship curve between the operating frequency of the RF power supply and the power reflection coefficient under the current matching impedance value (or the current first and second capacitor positions).

[0039] Step S16: If the relationship curve satisfies the predetermined requirements, the current matching impedance value is recorded as the optimal impedance value.

[0040] One understandable aspect is that, after obtaining a relationship curve between the operating frequency and power reflection coefficient of the RF power supply under the current matched impedance value (or the current first and second capacitor positions) by the steps of the above method, it is possible to determine whether the relationship curve between the operating frequency and power reflection coefficient of the RF power supply satisfies predetermined requirements. If the relationship curve satisfies the predetermined requirements, the current matched impedance value is recorded as the optimal impedance value (or the current first capacitor position is recorded as the first optimal capacitor position, and the current second capacitor position is recorded as the second optimal capacitor position).

[0041] Generally, the specified requirements may specifically include the existence of an operating frequency point in the relationship curve corresponding to a power reflection coefficient of less than 0.01, and the absence of a region in the relationship curve where the power reflection coefficient oscillates. The existence of an operating frequency point in the relationship curve corresponding to a power reflection coefficient of less than 0.01 ensures the existence of a frequency point for plasma ignition matching, thereby enabling successful plasma ignition matching. The absence of a region in the relationship curve where the power reflection coefficient oscillates ensures that the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient satisfies a one-to-one correspondence, similarly ensuring the success of plasma ignition matching.

[0042] In this way, by obtaining the optimal impedance value of the impedance matcher by the method of the embodiment of the present invention (or obtaining the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2), it is possible to ensure that when sweeping the corresponding RF power supply after fixing the impedance of the variable impedance device for adjusting the impedance of the impedance matcher to the optimal impedance value, the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient satisfies a one-to-one corresponding change relationship, and furthermore, the success of plasma ignition matching can be ensured.

[0043] In some examples, to better obtain the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient under the current matched impedance value (or the current first and second capacitor positions), the process of performing the “adjusting the operating frequency of the RF power supply” step of the above method is, specifically, to gradually change the operating frequency of the RF power supply within the operating frequency range of the RF power supply from one of the minimum and maximum values ​​of the operating frequency range to the other of the minimum and maximum values ​​of the operating frequency range according to a first predetermined adjustment step. Specifically, taking as an example that the operating frequency range of the RF power supply is 13.56 MHz ± 5% and the first predetermined adjustment step is 0.1 MHz, the operating frequency of the RF power supply is gradually changed from 12.882 MHz to 14.238 MHz in steps of 0.1 MHz, and the power reflection coefficient corresponding to each operating frequency of the RF power supply is recorded to obtain a relationship curve between the operating frequency of the RF power supply and the power reflection coefficient under the current matching impedance value (i.e., under the corresponding matching impedance value and power load after fixing the first variable capacitor to the first capacitor position and the second variable capacitor to the second capacitor position).

[0044] Generally, the matching impedance value of the variable impedance device found for the first time by the steps of the above method is recorded after the impedance matcher has completed impedance matching adjustment. At this time, the matching impedance value of the variable impedance device is also the matching impedance value in the related art. Specifically, the first capacitor position of the first variable capacitor C1 can coincide with the matching position C1_a of the first variable capacitor C1 in the related art, and the second capacitor position of the second variable capacitor C2 can coincide with the matching position C2_a of the second variable capacitor C2 in the related art. As can be seen from the above, in the related technology, the method of completing impedance matching by combining an RF power supply with a sweep function and an impedance matcher works as follows: when the RF power supply performs sweep matching, the impedance of the variable impedance device of the impedance matcher is fixed to the matched impedance value (i.e., the first variable capacitor C1 and the second variable capacitor C2 are fixed to the matched positions C1_a and C2_a). At this time, if the power supply load is inappropriate, the operating frequency (Frequency) and power reflection coefficient (Γ) of the RF power supply shown in Figures 2 and 3 are affected. 2 A relationship curve appears, and in the 13.4MHz to 13.5MHz operating frequency range of the RF power supply, the corresponding power reflection coefficient (Γ) 2It is clearly observed that the power reflection coefficient oscillates, and when the RF power supply performs a sweep, if its operating frequency enters this oscillating region, it cannot escape and search for an operating frequency point where the power reflection coefficient is less than 0.1, resulting in a failure of sweep matching of the RF power supply. In particular, with some electrically negative gases (HBr, CF4, etc.), the transition region from capacitive discharge to inductive discharge mode is large, and the plasma impedance is unstable in this region. If the matching impedance values ​​at this time (i.e., capacitor positions C1_a and C2_a) are inappropriate, the problem of power reflection coefficient oscillation is likely to occur. When using matching schemes of related technologies, the success of sweep matching of the RF power supply cannot be ensured because the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient in the line is not obtained in advance by optimizing the capacitor fixing position of the impedance matcher during sweep matching of the RF power supply. On the other hand, the process of "obtaining and searching for the relationship curve between the power supply frequency and the power reflection coefficient of the optimal impedance value of the variable impedance device (i.e., the appropriate fixed position of the first variable capacitor C1 and the second variable capacitor C2)" in the embodiment of the present application is a part that was lacking in the means of related technologies, and is also the root cause of the failure of power supply sweeps using the means of related technologies. Without performing this process, it is not possible to ensure that every RF power supply sweep matching is successful after turning on the RF power supply sweep function.

[0045] Therefore, in some examples, as shown in Figure 6, after performing the above step of "adjusting the operating frequency of the RF power supply, obtaining the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained by each adjustment, and generating the corresponding relationship curve," the following steps are further included.

[0046] Step S17: If the relationship curve does not meet the predetermined requirements, adjust the matching impedance value.

[0047] One point that can be understood is that if the steps of the above method determine that the relationship curve between the operating frequency and the power reflection coefficient of the RF power supply under the current matched impedance value (or the current first and second capacitor positions) does not satisfy the predetermined requirements of the steps of the above method, it indicates that the currently found matched impedance value (or the first and second capacitor positions) cannot ensure successful plasma ignition matching, that is, the currently found matched impedance value is not the optimal impedance value for the variable impedance device (or the first and second capacitor positions are not the first optimal capacitor position for the first variable capacitor and the second optimal capacitor position for the second variable capacitor), and in this case, it is necessary to further optimize the matched impedance value (or the first and second capacitor positions), that is, to further adjust the matched impedance value (or the first and second capacitor positions) to gradually find the optimal impedance value for the variable impedance device (or the first optimal capacitor position for the first variable capacitor and the second optimal capacitor position for the second variable capacitor).

[0048] Step S18: After adjusting the matching impedance value each time, a relationship curve generated by adjusting the operating frequency of the RF power supply is obtained, and if the obtained relationship curve satisfies predetermined requirements, the current matching impedance value is recorded as the optimal impedance value.

[0049] One understandable point is that, in the process of adjusting the matching impedance value (or the first and second capacitor positions), in order to gradually find the optimal impedance value of the variable impedance device (or the first optimal capacitor position of the first variable capacitor and the second optimal capacitor position of the second variable capacitor), each time the matching impedance value (or the first and second capacitor positions) is adjusted, it is necessary to adjust the operating frequency of the RF power supply to obtain a corresponding relationship curve. That is, following the process of step S15 above, a relationship curve between the operating frequency of the RF power supply and the power reflection coefficient corresponding to the current matching impedance value (or the current first and second capacitor positions) is obtained, and each time a relationship curve is obtained, it is necessary to determine whether the relationship curve in the step of the above method satisfies predetermined requirements. If the obtained relationship curve satisfies predetermined requirements, the current matching impedance value is recorded as the optimal impedance value (or the current first capacitor position is recorded as the first optimal capacitor position, and the current second capacitor position is recorded as the second optimal capacitor position).

[0050] In this way, by obtaining the optimal impedance value of the impedance matcher by the method of the embodiment of the present invention (or obtaining the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2), it is possible to ensure that when sweeping the corresponding RF power supply after fixing the impedance of the variable impedance device for adjusting the impedance of the impedance matcher to the optimal impedance value, the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient satisfies a one-to-one corresponding change relationship, and furthermore, the success of plasma ignition matching can be ensured.

[0051] In some examples, in order to better achieve the adjustment of the matching impedance value by adjusting the first and second capacitor positions, the current value of the first capacitor position may be gradually decreased according to a second predetermined adjustment step, and the current value of the second capacitor position may be gradually decreased according to a third predetermined adjustment step. For example, if the current value of the first capacitor position is the matching position C1_a, the current value of the second capacitor position is the matching position C2_a, the second predetermined adjustment step is 1%, and the second predetermined adjustment step is 2%, then by gradually decreasing the capacitor positions from the matching positions C1_a and C2_a in steps of 1% and 2%, respectively, it is necessary to obtain a relationship curve generated by adjusting the operating frequency of the RF power supply after each capacitor position adjustment (i.e., matching impedance value adjustment). If the obtained relationship curve satisfies predetermined requirements, the current first capacitor position is recorded as the first optimal capacitor position, and the current second capacitor position is recorded as the second optimal capacitor position (or the current matching impedance value is recorded as the optimal impedance value).

[0052] In one embodiment, as shown in Figure 7, an embodiment of the present application provides a sweep matching method for a semiconductor process apparatus, which may specifically include an RF power supply having a sweep function and an impedance matcher for adjusting the backend impedance of the RF power supply in real time, the impedance matcher including a variable impedance device for impedance adjustment, and the sweep matching method specifically includes the following steps.

[0053] Step S110: Depending on the plasma etching process currently being performed, the optimal impedance value of the variable impedance device is obtained using the method according to the above embodiment.

[0054] It can be understood that the sweep matching method in the embodiment of the present application is an improvement on the method in related art that completes impedance matching by combining an RF power supply with a sweep function and an impedance matcher. The specific structure of the RF power supply and impedance matcher can be seen in Figure 1. In order to avoid the problem that the signal output from the RF power supply oscillates due to an inappropriate load impedance of the RF power supply, and further causes the sweep matching of the RF power supply to fail, before performing the sweep operation of the RF power supply, an appropriate load for the RF power supply in the plasma etching process currently being performed is found, i.e., the optimal impedance value of the variable impedance device (or the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2) is obtained, thereby ensuring that when sweeping the RF power supply, the relationship curve between the operating frequency of the RF power supply and the power reflection coefficient satisfies the one-to-one corresponding change relationship shown in Figure 8.

[0055] Step S120: Fix the impedance of the variable impedance device to the optimal impedance value.

[0056] One understandable point is that, after obtaining the optimal impedance value of the variable impedance device (or the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2) by the steps of the above method, the impedance of the variable impedance device can be further fixed to the optimal impedance value (specifically, the first variable capacitor may be fixed to the first optimal capacitor position and the second variable capacitor may be fixed to the second optimal capacitor position), and at this time, the RF power supply can have an appropriate load.

[0057] Step S130: The sweep mode of the RF power supply is turned on to achieve plasma ignition matching.

[0058] One understandable point is that by following the steps of the above method, the impedance of the variable impedance device is fixed to the optimal impedance value (or the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2). That is, after the RF power supply has a suitable load, the sweep mode of the RF power supply is turned on, and by turning on the sweep mode of the power supply at the suitable load, the plasma can be rapidly ignited, avoiding the occurrence of frequency oscillation regions, and further enabling a stable and reproducible ignition matching process for the plasma.

[0059] Furthermore, as can be seen from the above, after finding the optimal impedance value of the variable impedance device (or the first optimal capacitor position of the first variable capacitor C1 and the second optimal capacitor position of the second variable capacitor C2), turning on the sweep function of the RF power supply can assist in rapid ignition matching of the plasma. In a conventional general L-type impedance matcher, as shown in Figure 9, the first variable capacitor C1 is connected between the output terminal of the RF power supply and ground, and the second variable capacitor C2 is connected between the output terminal of the RF power supply and the load (i.e., the plasma portion shown in Figure 9).

[0060] The input admittance from the output terminal of the RF power supply to the plasma is G L When that is the case,

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[0061] In this way, the embodiment of the present invention effectively avoids the problem of the signal output from the RF power supply oscillating, improves the success rate of sweep matching of the RF power supply, and further improves the reproducibility and stability of the process results.

[0062] In some examples, as shown in Figure 10, the specific process for performing the step of "obtaining the optimal impedance value of the variable impedance device using the method according to the above embodiment, depending on the plasma etching process currently being performed" in order to better obtain the optimal impedance value of the variable impedance device (or the first optimal capacitor position of the corresponding first variable capacitor and the second optimal capacitor position of the corresponding second variable capacitor) is as follows.

[0063] Step S111: Determine whether the plasma etching process to be executed is an existing plasma etching process.

[0064] One understandable point is that an existing plasma etching process generally refers to a plasma etching process that automatically searches for and saves the optimal impedance value (or optimal capacitor position), that is, a plasma etching process previously performed by the semiconductor process equipment, and that process has already found the corresponding optimal impedance value (or optimal capacitor position, which may include the first optimal capacitor position of the first variable capacitor and the second optimal capacitor position of the second variable capacitor) in the process that was previously performed, and that the corresponding optimal impedance value (or optimal capacitor position) can be directly recalled when the same process is subsequently performed, and therefore the corresponding optimal impedance value (or optimal capacitor position) may be saved in a predetermined process parameter list. Accordingly, it is possible to determine whether the plasma etching process to be executed is an existing plasma etching process depending on whether the plasma etching process to be executed is saved in the predetermined process parameter list, and this process specifically involves determining whether the plasma etching process to be executed is an existing plasma etching process depending on whether the plasma etching process to be executed is stored in the predetermined process parameter list. If the plasma etching process to be executed is stored in the predetermined process parameter list, it is determined that the plasma etching process to be executed is an existing plasma etching process. If the plasma etching process to be executed is not stored in the predetermined process parameter list, it is determined that the plasma etching process to be executed is not an existing plasma etching process.

[0065] Furthermore, the predetermined process parameter list may pre-record plasma etching processes that the semiconductor process apparatus has not previously performed. In this case, only the plasma etching processes that have been performed have their corresponding optimal impedance values ​​(or optimal capacitor positions) recorded, while the records of the corresponding optimal impedance values ​​(or optimal capacitor positions) for plasma etching processes that have not been performed remain in their default state. In this case, the process for determining whether the plasma etching process to be performed is an existing plasma etching process may specifically involve determining whether the plasma etching process to be performed is an existing plasma etching process based on whether the optimal impedance values ​​(or first optimal capacitor positions and second optimal capacitor positions) of the plasma etching process to be performed are in their default state in the predetermined process parameter list. If the optimal impedance values ​​(or first optimal capacitor positions and second optimal capacitor positions) of the plasma etching process to be performed are in their default state, it is determined that the plasma etching process to be performed is not an existing plasma etching process. If the optimal impedance values ​​(or first optimal capacitor positions and second optimal capacitor positions) of the plasma etching process to be performed are not in their default state, it is determined that the plasma etching process to be performed is an existing plasma etching process.

[0066] Step S112: If the plasma etching process to be performed is not an existing plasma etching process, the optimal impedance value of the variable impedance device is obtained using the method in the above embodiment and recorded and stored in a predetermined process parameter list.

[0067] One point that can be understood is that if the steps of the above method determine that the plasma etching process to be executed is not an existing plasma etching process, it indicates that the semiconductor process equipment has not previously executed the plasma etching process to be executed. In this case, by performing an optimal impedance value (or optimal capacitor position) search process for the plasma etching process to be executed using the method in the above embodiment, it is necessary to obtain the optimal impedance value (or the first optimal capacitor position of the first variable capacitor and the second optimal capacitor position of the second variable capacitor) of the variable impedance device under the process conditions corresponding to the plasma etching process to be executed, and record and store it in a predetermined process parameter list. This allows the corresponding optimal impedance value (or optimal capacitor position) to be directly recalled when the same process is executed subsequently.

[0068] Step S113: If the plasma etching process to be executed is an existing plasma etching process, the plasma etching process to be executed and the corresponding optimal impedance value stored are found from a predetermined list of process parameters.

[0069] One point that can be understood is that, as can be seen from the above, if the plasma etching process to be executed is an existing plasma etching process, the corresponding optimal impedance value (or optimal capacitor position, specifically, which may include the first optimal capacitor position of the first variable capacitor and the second optimal capacitor position of the second variable capacitor) is pre-recorded in the predetermined process parameter list. Therefore, if the plasma etching process to be executed is determined to be an existing plasma etching process by the steps of the above method, the plasma etching process to be executed and the corresponding stored optimal impedance value (or first optimal capacitor position and second optimal capacitor position) can be directly found from the predetermined process parameter list.

[0070] In one embodiment, an embodiment of the present application further provides a semiconductor process apparatus comprising an RF power supply having a sweep function, an impedance matcher for adjusting the backend impedance of the RF power supply in real time, and a controller, wherein the impedance matcher includes a variable impedance device for performing impedance adjustment, and the controller comprises a processor, a memory, and a program stored in the memory and executable by the processor, wherein when the program is executed by the processor, it performs a step of the method for obtaining the optimal capacitor position of the impedance matcher in the embodiment or a step of the sweep matching method in the embodiment. A redundant explanation is omitted here.

[0071] In some examples, the impedance matchers described above may specifically be L-type, π-type, and T-type impedance matchers. An L-type impedance matcher consists of one series inductor and a parallel capacitor, and its structure is similar to the letter L. A π-type impedance matcher consists of two parallel capacitors and one series inductor, and its structure is similar to the letter π. A T-type impedance matcher consists of two series inductors and one parallel capacitor, and its structure is similar to the letter T. All of these structural forms can match different impedances, and all have a first variable capacitor and a second variable capacitor for impedance adjustment, and the specific structure to use can be determined depending on the actual situation.

[0072] While the present application has illustrated and described one or more embodiments, those skilled in the art will be able to conceive of equivalent variations and modifications by reading and understanding this specification and the drawings. This application includes all such variations and modifications and is limited only by the scope of the appended claims. In particular, with respect to the various functions performed by the above components, the terms used to describe such components correspond to any component (unless otherwise specified) that performs a designated function of the above component (e.g., it is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the exemplary embodiments of this specification shown herein.

[0073] In other words, the above are merely embodiments of the present application and do not limit the scope of the patent. Any equivalent structure or flow transformation using the contents of the specification and drawings of the present application, including combinations of technical features between each embodiment or direct or indirect applications to other related technical fields, are all similarly included within the scope of the patent protection of the present application.

[0074] Furthermore, in the description of this application, directions or positional relationships indicated by terms such as "center," "vertical," "horizontal," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," and "outside" are directions or positional relationships based on the illustrations and are merely for the convenience and simplification of the description of this application. They do not indicate or imply that such devices or elements necessarily have a specific direction, or are configured and operated in a specific direction, and therefore do not limit this application. Also, structural elements with the same or similar characteristics may be marked with the same or different symbols in this application. It should be understood that terms such as "first" and "second" are used for explanatory purposes only and do not indicate or imply their relative importance, nor do they implicitly indicate the number of technical features being indicated. Accordingly, features limited by "first" and "second" may explicitly or implicitly include one or more such features. In the description of this application, unless otherwise clearly and specifically limited, "multiple" means two or more.

[0075] In this application, the term “exemplary” means “used as an example, illustration, or explanation.” Any embodiment described “exemplary” in this application is not necessarily construed as preferable or superior to other embodiments. The above description is provided so that a person skilled in the art may implement and use this application. Various details are listed in the above description for interpretive purposes. A person skilled in the art should understand that they may recognize that this application can be implemented without using these particular details. In other embodiments, known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary details. Thus, this application is not limited to the embodiments shown, but corresponds to the broadest scope that matches the principles and features disclosed herein.

Claims

1. A method for obtaining the optimal impedance value of an impedance matcher, which is used to adjust the backend impedance of an RF power supply in real time and includes a variable impedance device for impedance adjustment, The steps include adjusting the impedance of the variable impedance device to a predetermined impedance value, The steps include: starting the RF power supply and, if the sweep function of the RF power supply is off, adjusting the impedance of the variable impedance device using an automatic matching algorithm to perform impedance matching adjustment; After completing the impedance matching adjustment, the matching impedance value of the variable impedance device at that time is recorded, and the RF power supply is turned off. The steps include fixing the impedance of the variable impedance device to the matching impedance value, and then turning the RF power supply on again, The steps include adjusting the operating frequency of the RF power supply, obtaining the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained through each adjustment, and generating a corresponding relationship curve, A method for obtaining the optimal impedance value of an impedance matcher, comprising the step of recording the current matching impedance value as the optimal impedance value if the relationship curve satisfies predetermined requirements.

2. The step of adjusting the operating frequency of the RF power supply is, The method according to claim 1, characterized in that, within the operating frequency range of the RF power supply, the method includes a step of gradually changing the operating frequency of the RF power supply from one of the minimum and maximum values ​​of the operating frequency range to the other of the minimum and maximum values ​​of the operating frequency range according to a first predetermined adjustment step.

3. The method according to claim 1, characterized in that the predetermined requirements include the existence of an operating frequency point in the relational curve corresponding to the power reflection coefficient of less than 0.01, and the absence of a region in the relational curve where the power reflection coefficient oscillates.

4. After the steps of adjusting the operating frequency of the RF power supply, obtaining the correspondence between the operating frequency of the RF power supply and the power reflection coefficient obtained by each adjustment, and generating a corresponding relationship curve, If the aforementioned relationship curve does not satisfy the predetermined requirements, the steps include adjusting the matching impedance value, The method according to claim 1, further comprising the steps of: obtaining a relationship curve generated by adjusting the operating frequency of the RF power supply after each adjustment of the matching impedance value; and recording the current matching impedance value as the optimal impedance value when the obtained relationship curve satisfies predetermined requirements.

5. The variable impedance device includes a first variable capacitor and a second variable capacitor. The step of adjusting the variable impedance device to a predetermined impedance value includes the steps of adjusting the first variable capacitor to a first predetermined capacitor position and adjusting the second variable capacitor to a second predetermined capacitor position. After completing the impedance matching adjustment, the step of recording the matching impedance value of the variable impedance device at that time includes the step of recording the first capacitor position of the first variable capacitor and the second capacitor position of the second variable capacitor at that time. The step of fixing the impedance of the variable impedance device to the matching impedance value includes the steps of fixing the first variable capacitor to the first capacitor position and fixing the second variable capacitor to the second capacitor position. The method according to any one of claims 1 to 4, characterized in that the step of recording the current matching impedance value as the optimal impedance value includes the step of recording the current first capacitor position as the first optimal capacitor position and recording the current second capacitor position as the second optimal capacitor position.

6. The method according to claim 5, further comprising the step of adjusting the matching impedance value by gradually decreasing the current value of the first capacitor position according to a second predetermined adjustment step and gradually decreasing the current value of the second capacitor position according to a third predetermined adjustment step if the relationship curve does not satisfy predetermined requirements.

7. The first variable capacitor is connected between the output terminal of the RF power supply and ground, and the second variable capacitor is connected between the output terminal of the RF power supply and the load. The method according to 6, characterized in that the third predetermined adjustment step is greater than the second predetermined adjustment step.

8. A sweep matching method for a semiconductor process apparatus, comprising an RF power supply having a sweep function and an impedance matcher for adjusting the backend impedance of the RF power supply in real time, wherein the impedance matcher includes a variable impedance device for performing impedance adjustment, The steps include obtaining the optimal impedance value of the variable impedance device using the method described in any one of claims 1 to 7, depending on the plasma etching process currently being performed, The steps include fixing the impedance of the variable impedance device to the optimal impedance value, A sweep matching method characterized by comprising the step of turning on the sweep mode of the RF power supply to achieve plasma ignition matching.

9. The step of obtaining the optimal impedance value of the variable impedance device is: The steps include determining whether the plasma etching process to be executed is an existing plasma etching process, The sweep matching method according to claim 8, characterized in that, if the plasma etching process to be performed is not an existing plasma etching process, the sweep matching method includes the step of obtaining the optimal impedance value of the variable impedance device and recording and storing it in a predetermined process parameter list.

10. The step of determining whether the plasma etching process to be executed is an existing plasma etching process is, The steps include determining whether the plasma etching process to be executed is an existing plasma etching process, depending on whether the plasma etching process to be executed is stored in the predetermined process parameter list, If the plasma etching process to be executed is stored in the predetermined process parameter list, the step of determining that the plasma etching process to be executed is an existing plasma etching process, The sweep matching method according to claim 9, further comprising the step of determining that the plasma etching process to be executed is not an existing plasma etching process if the plasma etching process to be executed is not stored in the predetermined process parameter list.

11. The step of determining whether the plasma etching process to be executed is an existing plasma etching process is, The steps include determining whether the plasma etching process to be executed is an existing plasma etching process based on whether the optimal impedance value of the plasma etching process to be executed is in the default state in the predetermined process parameter list, If the optimal impedance value of the plasma etching process to be executed is in the default state, the step of determining that the plasma etching process to be executed is not an existing plasma etching process, The sweep matching method according to claim 9, further comprising the step of determining that the plasma etching process to be executed is an existing plasma etching process if the optimal impedance value of the plasma etching process to be executed is not in the default state.

12. The step of obtaining the optimal impedance value of the variable impedance device is: The sweep matching method according to any one of claims 9 to 11, further comprising the step of finding the plasma etching process to be executed and the corresponding optimal impedance value stored from the predetermined process parameter list, if the plasma etching process to be executed is an existing plasma etching process.

13. A semiconductor process apparatus comprising an RF power supply having a sweep function, an impedance matcher for adjusting the backend impedance of the RF power supply in real time, and a controller, wherein the impedance matcher includes a variable impedance device for performing impedance adjustment, and the controller comprises a processor, a memory, and a program stored in the memory and executable by the processor, wherein when the program is executed by the processor, it performs a step of the method according to any one of claims 1 to 7, or a step of the sweep matching method according to any one of claims 8 to 12.

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