Control method for radio frequency system used in semiconductor process device

Abstract

The present disclosure provides a control method for a radio frequency system used in a semiconductor process device, comprising: completing impedance matching at a first output power of a power supply, and acquiring a first matching state of a matcher; adjusting the power supply to a second output power, completing impedance matching, and acquiring a second matching state of the matcher; comparing the parameter changes of the matcher in the first matching state and the second matching state; and on the basis of the comparison result, performing parameter adjustment on the basis of parameters corresponding to the first matching state of the matcher, so that when the power supply is restored to the first output power, the power fed into a load unit increases as the coupling efficiency of plasma decreases. In the control method for a radio frequency system used in a semiconductor process device of the present application, by matching the changed load impedance of a load unit by means of a matcher, the relationship between plasma resistance and the load impedance can be determined from the changes in the matcher; thus, the matcher can be configured in advance, making the system more stable.

Description

Control methods for radio frequency systems used in semiconductor process equipment Technical Field

[0001] This application relates to the field of semiconductor manufacturing, and more specifically, to a control method for a radio frequency system for semiconductor process equipment. Background Technology

[0002] Etching systems typically use an RF generator to supply radio frequency energy to a special gas (such as argon, helium, nitrogen, etc.) in a high-vacuum state within a chamber. This generates a plasma containing a large number of active particles, including electrons, ions, excited-state atoms, molecules, and free radicals. These active particles interact with the wafer placed in the chamber and exposed to the plasma environment, causing various physical and chemical reactions on the wafer material surface. This alters the surface properties of the material, thus completing the etching of the wafer.

[0003] In the prior art, during the semiconductor process, some byproducts are gradually generated in the process chamber, which changes the plasma state inside the chamber and reduces the plasma feed power. When the plasma feed power decreases, its coupling efficiency also decreases further, making the plasma prone to extinguishing and affecting the stability of the system. Summary of the Invention

[0004] This application aims to at least solve the problem in the prior art that the reduced plasma feed power leads to a decrease in coupling efficiency, which easily causes quenching and affects system stability. It proposes a control method for the radio frequency system of semiconductor process equipment.

[0005] To achieve the purpose of this application, a control method for a radio frequency (RF) system of a semiconductor process apparatus is provided. The RF system includes a power supply, a matching unit, and a coil. The power supply is electrically connected to the input terminal of the matching unit, and the output terminal of the matching unit is electrically connected to the coil for generating plasma within a process chamber. The coil and the plasma it generates form a load unit. The control method includes:

[0006] At the first output power of the power supply, impedance matching is completed, and the first matching state of the matcher is obtained; the power supply is adjusted to the second output power, impedance matching is completed, and the second matching state of the matcher is obtained; the parameter changes of the matcher in the first matching state and the second matching state are compared; based on the comparison result, the parameters are adjusted on the basis of the parameters corresponding to the first matching state of the matcher, so that after the power supply is restored to the first output power, the power fed into the load unit increases when the coupling efficiency of the plasma decreases.

[0007] In some embodiments, the matching device includes: a real part adjustment element for matching the real part of the load impedance of the load unit; the step of comparing the parameter changes of the matching device in the first matching state and the second matching state includes: comparing the parameter changes of the real part adjustment element of the matching device in the first matching state and the second matching state.

[0008] In some embodiments, the real part adjustment element is a first adjustable capacitor; comparing the parameter changes of the real part adjustment element of the matching device in the first matching state and the second matching state specifically includes: obtaining a first capacitance value of the first adjustable capacitor in the first matching state of the matching device; obtaining a second capacitance value of the first adjustable capacitor in the second matching state of the matching device; and comparing the magnitudes of the first capacitance value and the second capacitance value.

[0009] In some embodiments, the step of presetting the parameters of the matcher based on the comparison result so that the power fed into the load unit increases when the coupling efficiency of the plasma decreases at the first output power of the power supply specifically includes: if the second output power is less than the first output power, and if the second capacitance value is greater than the first capacitance value, then the first adjustable capacitor is adjusted to a third capacitance value, the third capacitance value being greater than the first capacitance value; if the second capacitance value is less than the first capacitance value, then the first adjustable capacitor is adjusted to a fourth capacitance value, the fourth capacitance value being less than the first capacitance value.

[0010] In some embodiments, the difference between the first capacitance value and the third capacitance value is 0.2% to 2% of the adjustment range of the first variable capacitor.

[0011] In some embodiments, the difference between the first capacitance value and the fourth capacitance value is 0.2% to 2% of the adjustment range of the first variable capacitor.

[0012] In some embodiments, the difference between the first preset value and the second preset value is greater than or equal to 5W and less than or equal to 20W.

[0013] In some embodiments, the load impedance of the load unit is

[0014] Where R1 is the equivalent resistance of the coil, ZM is the mutual inductance impedance between the coil and the plasma in the process chamber, R2 is the resistance of the plasma in the process chamber, and Z... L2 The inductive reactance is the plasma equivalent in the process chamber.

[0015] According to a second aspect of this application, a radio frequency system is also disclosed, which is controlled using the control method described above.

[0016] According to a second aspect of this application, a semiconductor process apparatus is also disclosed, comprising: a process chamber, a radio frequency system, and a controller, wherein the controller includes at least one processor and at least one memory, the memory storing a computer program that, when executed by the processor, implements the control method described above.

[0017] The control method for the radio frequency system of semiconductor process equipment disclosed in this application matches the load impedance of the changed load unit with the matching device. By observing the changes in the matching device, the relationship between the plasma resistance and the load impedance can be determined, thereby setting the matching device in advance. When the feed power decreases, causing a decrease in plasma coupling efficiency, the matching device can be better matched with the load impedance because it has been set in advance. This leads to an increase in the feed power, which can effectively prevent plasma quenching and make the system more stable. Attached Figure Description

[0018] Figure 1 is a schematic diagram of the radio frequency system of the process etching machine in the prior art;

[0019] Figure 2 is a schematic diagram of the structure of a matcher in the prior art;

[0020] Figure 3 is a flowchart of the matching process of the matcher in the prior art;

[0021] Figure 4 is a schematic diagram of the structure of a semiconductor process equipment according to an embodiment of this application;

[0022] Figure 5 is an equivalent circuit model of the radio frequency system according to an embodiment of this application;

[0023] Figure 6 shows the load impedance Z in an embodiment of this application. load The curves showing the real and imaginary parts of the impedance versus the plasma resistance R2.

[0024] Figure 7 is a Smith chart of the matcher in an embodiment of this application;

[0025] Figure 8 is a flowchart of the control method according to an embodiment of this application;

[0026] Figure 9 is an equivalent circuit model of a radio frequency system according to another embodiment of this application. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solution of this application, the control method for a radio frequency system for semiconductor process equipment provided in this application will be described in detail below with reference to the accompanying drawings.

[0028] Etching systems typically use an RF generator to supply radio frequency energy to a special gas (such as argon, helium, nitrogen, etc.) in a high-vacuum state within a chamber. This generates a plasma containing a large number of active particles, including electrons, ions, excited-state atoms, molecules, and free radicals. These active particles interact with the wafer placed in the chamber and exposed to the plasma environment, causing various physical and chemical reactions on the wafer material surface. This alters the surface properties of the material, thus completing the etching of the wafer.

[0029] Figure 1 shows the RF system of a conventional etching machine. The RF power supply 1 and the matching unit 2 are connected via a 50Ω coaxial cable 3, and the output impedance of the RF power supply 1 is typically a standard value, for example, 50Ω. To couple the power output from the RF power supply 1 into the process chamber 4, the matching network of the matching unit 2 dynamically adjusts its parameters according to changes in the equivalent impedance of the process chamber 4 to ensure that its input impedance is also equal to 50Ω. Input impedance refers to the impedance presented when viewed from the input port of the matching unit 2 towards its internal circuitry (including the matching network) and its connected load (process chamber 4).

[0030] As shown in Figure 2, the existing matching unit 2 consists of four modules: an input sensor 5, a matching circuit unit 6, a control unit 7, and an execution unit 8. The input sensor 5 is connected between the output terminal of the RF power supply 1 and the input terminal of the matching circuit unit 6. The input sensor 5 is used to feed back the measured voltage and current information to the control unit 7. The control unit 7 is used to calculate the information fed back by the input sensor 5 and give an adjustment signal, which is then sent to the execution unit 8. The execution unit 8 is used to control the impedance of the matching circuit unit 6 under the control of the adjustment signal, so as to match the output impedance of the RF power supply 1 with the input impedance of the load (such as the process chamber 4).

[0031] The execution unit 8 of the matching circuit 2 is generally a stepper motor. The stepper motor drives the capacitor adjustment mechanism of the adjustable capacitors C10 and C20 in the matching circuit unit 6. There is a one-to-one correspondence between the rotation position of the stepper motor and the capacitance value of the adjustable capacitor. Therefore, by adjusting the rotation position and direction of the stepper motor, the capacitance value of the variable capacitor can be precisely adjusted, so that the matching circuit 2 can dynamically adjust the input impedance, thereby achieving impedance matching.

[0032] As shown in Figure 3, the typical matching process of matcher 2 is as follows: Matcher 2 ultimately completes impedance matching according to the following steps in this matching process:

[0033] S01. Turn on RF power supply 1 and output RF power;

[0034] S02. Based on the voltage, current, and phase information fed back by the input sensor 5, determine the RF impedance Z. M The magnitude and phase;

[0035] S03, Determine the RF impedance Z M If the modulus is equal to 50Ω, proceed to step S05; otherwise, proceed to step S04.

[0036] S04. Based on the comparison between the modulus and 50Ω, increase or decrease the capacitance of the adjustable capacitor C20; specifically, if the modulus is greater than 50Ω, increase the capacitance of the adjustable capacitor C20; if the modulus is less than 50Ω, decrease the capacitance of the adjustable capacitor C20.

[0037] S05, Determine the RF impedance Z M If the phase is equal to 0 degrees, proceed to step S07; otherwise, proceed to step S06.

[0038] S06. Based on the phase-to-0-degree comparison, increase or decrease the capacitance of the adjustable capacitor C10; specifically, if the phase is greater than 0 degrees, decrease the capacitance of the adjustable capacitor C10; if the phase is less than 0 degrees, increase the capacitance of the adjustable capacitor C10.

[0039] S07. Determine whether the plasma process is complete. If yes, the process ends; otherwise, return to step S02.

[0040] In existing technology, when the impedance modulus measured by the input sensor 5 of the matching network 2 is 50Ω and the phase is 0 degrees, the positions of the two adjustable capacitors are fixed. However, in practical applications, the phase detected by the input sensor 5 is almost never exactly equal to 0 degrees. Due to different process conditions and preset conditions, when the adjustable capacitors are finally fixed, the phase detected by the input sensor 5 may be greater than 0 degrees or less than 0 degrees. When the phase is less than 0 degrees, the back-end circuit exhibits capacitive behavior. For capacitors, they typically have the characteristic of clamping voltage; that is, under external disturbances, their voltage can remain relatively stable, but the current is difficult to keep stable. Therefore, when there is an external disturbance, the current in the entire network will change abruptly, leading to abrupt changes in the coil current. The change in coil current will cause changes in the magnetic field inside the process chamber, such as the etching chamber, and the change in the magnetic field will affect the plasma state maintained by the magnetic field, ultimately leading to changes in the plasma. Changes in the plasma will cause changes in the impedance of the matching network. The aforementioned changes mainly involve changes in the electromagnetic field, which usually occur on a time scale of microseconds. However, the capacitor used for impedance adjustment inside the matching unit 2 is driven by a motor, which is a mechanical motion with a response time typically on the order of milliseconds. Therefore, the response speed of this mechanical motion is difficult to keep up with the rapid changes in the downstream plasma, easily leading to mismatch. This mismatch can severely affect the stability of the system, resulting in process inhomogeneities or a decline in equipment performance.

[0041] Furthermore, in existing semiconductor processes, byproducts gradually accumulate within the process chamber, altering the plasma state and reducing its feed power. As the feed power decreases, the coupling efficiency further declines, making the plasma more susceptible to quenching. Once quenched, the process gas ceases to conduct electricity, increasing resistance and causing a sudden change in impedance at the load. In this situation, the motors in the matching network, due to their mechanical motion characteristics, struggle to keep up with the rapid impedance changes, leading to sudden mismatches and impacting system stability.

[0042] To address the aforementioned problems, this application discloses a control method for a radio frequency (RF) system in a semiconductor process apparatus. As shown in Figure 4, the semiconductor process apparatus includes a process chamber 10, an RF system 20, and a controller. The controller controls the RF system 20, which includes a power supply (not shown), a matching unit 21, and a coil 22. The output terminal of the power supply is electrically connected to the input terminal of the matching unit 21, and the output terminal of the matching unit 21 is electrically connected to the coil 22. The power supply applies RF power to the coil 22 through the matching unit 21 to excite the process gas to form plasma.

[0043] In this embodiment, the semiconductor process equipment is an inductively coupled plasma (ICP) etching equipment. The control method of this application will be described in detail below using the on-radio frequency system of the ICP etching equipment as an example:

[0044] As shown in Figures 4 and 5, Figure 5 is an equivalent circuit model of the radio frequency system 20 of this application. The radio frequency system 20 includes a matching unit 21 and a coil 22. The input terminal of the matching unit 21 is electrically connected to the output terminal of a power supply (not shown in the figure), and the output terminal of the matching unit 21 is electrically connected to the coil 22. The power supply applies radio frequency power to the coil 22 through the matching unit 21. The electric field generated by the coil 22 is used to excite the process gas to form plasma. The coil 22 and the plasma forming load unit are also included.

[0045] In this embodiment, the matching device 21 is an L-type network matching device 21, where L is the inductance in the matching network, C1 is the first adjustable capacitor used to match the real impedance of the load unit, and C2 is the second adjustable capacitor used to match the imaginary impedance of the load unit.

[0046] In the load unit, R1 is the equivalent ohmic resistance of coil 22, M is the mutual inductance between coil 22 and the plasma in process chamber 10, and R2 is the resistance of the plasma in process chamber 10. L1 is the inductance of coil 22, and L2 is the inductance of the plasma in process chamber 10. The impedance Z of the load unit is... load for

[0047] Among them, Z M Z represents the mutual inductance impedance between coil 22 and the plasma within process chamber 10. L2 The plasma equivalent inductive reactance within the process chamber 10.

[0048] Depending on the size of the chamber, most plasma inductances are approximately 0.25 μH. During the plasma ignition process, the process chamber 10 undergoes a process from no plasma to plasma formation; therefore, the value of R2 can vary from 1e6 Ω to several Ω.

[0049] As shown in Figure 6, Z is calculated according to the above formula. load The curves show the relationship between the real and imaginary parts of the impedance and the variation of the plasma resistance R2 within the process chamber 10. The vertical axis represents Z. load The real and imaginary parts of the impedance are expressed in ohms; the horizontal axis represents the plasma resistance R2; the dotted line corresponding to Z_load_r(ohm) is the curve of the real part of the impedance changing with the plasma resistance R2, while the solid line corresponding to Z_load_i(ohm) is the curve of the imaginary part of the impedance changing with the plasma resistance R2.

[0050] It should be noted that the resistance value of the plasma resistor R2 varies under different process gas ratios, pressures, and power conditions. However, under the same process gas ratios and pressures, the higher the power, the lower the resistance value of the plasma resistor R2. This is because, during the ignition matching process, as the input power increases, the number of charged particles excited by the process gas also increases accordingly, and the conductivity of the process gas is enhanced. Therefore, the resistance value of R2 will undergo a process of decreasing from large to small, which is the process of the horizontal axis changing from right to left in Figure 6.

[0051] As shown in Figure 6, Z_load_r undergoes a process of first increasing and then decreasing as the resistance of R2 decreases, resulting in a peak point in the Z_load_r curve in Figure 6. When disturbances such as gas pressure instability occur in the entire etching system, causing a sudden change in the plasma impedance inside the process chamber 10, and the matching device 21 cannot adjust in time, the feed power will decrease. After the matching stabilizes, if the resistance of R2 is to the left of the peak point shown in Figure 6, then as the feed power decreases, the resistance of R2 increases, and Z_load_r will also increase. Conversely, if the resistance of R2 is to the right of the peak point shown in Figure 6, then as the feed power decreases, the resistance of R2 increases, and Z_load_r will decrease.

[0052] The following section combines the Smith chart and the impedance Z of the load element. load Matching paths on the Smith chart, for Z load The relationship between the real part of the impedance and the size of C1 during matching by the matching circuit 21 will be explained in detail.

[0053] As shown in the Smith chart of matcher 21 in Figure 7, it should be noted beforehand that a polar coordinate system is used in Figure 7. The right end of the horizontal axis in Figure 7 is infinity, the left end of the horizontal axis is 0, and the midpoint of the horizontal axis (▲ position) is the matching position.

[0054] As shown in Figure 7, when the coordinate point moves along the arc of the same constant resistance circle (for example, along the arc of the first constant resistance circle 41), Z load The real part of the impedance remains unchanged, while Z loadThe imaginary part of the impedance changes; when the coordinate point moves between different fixed-resistance circles (for example, from the first fixed-resistance circle 41 to the second fixed-resistance circle 42), the real part of the impedance changes accordingly. Furthermore, the point where the fixed-resistance circle intersects the horizontal axis represents the magnitude of the real part of the impedance corresponding to that circle. The closer the intersection point of the fixed-resistance circle and the horizontal axis is to the right end of the horizontal axis, the smaller the diameter of the fixed-resistance circle, but the larger the real part of the impedance represented by that circle. For example, in Figure 7, the diameter of the first fixed-resistance circle 41 is smaller than the diameter of the second fixed-resistance circle 42, but the real part of the impedance represented by the first fixed-resistance circle 41 is larger than the real part of the impedance represented by the second fixed-resistance circle 42.

[0055] As shown in Figure 7, when the coordinate point moves along the arc of the same equal-conductivity circle (for example, along the arc of the first equal-conductivity circle 51), the imaginary part of the impedance remains basically unchanged, while the real part of the impedance changes; when the coordinate point moves between different equal-conductivity circles (for example, from the first equal-conductivity circle 51 to the second equal-conductivity circle 52), the imaginary part of the impedance will change accordingly.

[0056] When matching in matcher 21, adjusting the size of C1 is equivalent to adjusting Z. load When the real part of the impedance is obtained, the coordinate point in Figure 7 will move along the arc of the circle of equal conductance. Adjusting the value of C2, which is equivalent to adjusting Z... load When the impedance is the imaginary part, the coordinate point in Figure 7 will move along the arc of the constant impedance circle.

[0057] Based on the above rules, let Z1 and Z2 represent Z in Figure 5 respectively. load Two possible impedance values ​​are given, where the × position represents the impedance value of Z1 at the coordinate point on the Smith chart, and the + position represents the impedance value of Z2 at the coordinate point on the Smith chart. R is the real part of the impedance of Z1, and R' is the real part of the impedance of Z2, with R > R'. The imaginary parts of the impedances of Z1 and Z2 are both jX.

[0058] As shown in Figure 7, the coordinate point of Z1 is located on the first constant resistance circle 41, while the coordinate point of Z2 is located on the constant resistance circle (not shown in the figure) between the first constant resistance circle 41 and the second constant resistance circle 42, that is, R > R'. At the same time, the coordinate points of Z1 and Z2 are both located on the first equal conductance circle 51, therefore, their imaginary impedance values ​​are the same.

[0059] The impedance Z of the load unit loadWhen the impedance value is Z1, and the matching device 21 matches the imaginary part of the impedance of Z1, by adjusting C2, the imaginary part of the impedance at the front end of the matching device 21 changes from the × position on the first equal conductance circle 51 to the ● position on the second equal conductance circle 52 along the first constant resistance circle 41 in Figure 7. Then, when the matching device 21 matches the real part of the impedance of Z1, by adjusting C1, the real part of the impedance at the front end of the matching device 21 changes from the ● position to the ▲ position along the second equal conductance circle 52 in Figure 7. The distance traveled on the second conductance circle 52 during the movement from the ● position to the ▲ position represents the magnitude of the change in C1; the longer the distance, the greater the change in C1, and vice versa.

[0060] The impedance Z of the load unit load When the impedance value is Z2, when the matching device 21 matches the imaginary part of the impedance of Z2, by adjusting C2, the imaginary part of the impedance at the front end of the matching device 21 changes from the + position on the first equal conductance circle 51 to the ■ position on the second equal conductance circle 52 in Figure 7; then, when the matching device 21 matches the real part of the impedance of Z2, by adjusting C1, the impedance at the front end of the matching device 21 changes from the ■ position along the second equal conductance circle 52 to the ▲ position in Figure 7. The distance traveled on the second equal conductance circle 52 during the movement from the ■ position to the ▲ position represents the magnitude of the change in C1. The longer the distance traveled, the greater the change in C1, and vice versa.

[0061] As shown in Figure 7, when the matching device 21 is matching, the distance from the + position to the ■ position is equivalent to the distance from the X position to the ● position. These two distances correspond to the magnitude of the change in C2 during the matching process. This indicates that when the matching device 21 is matching Z1 and Z2, the position of the capacitor C2 is basically the same, that is, the change in the real part of the load is not sensitive to C2.

[0062] Regarding the change of C1, as shown in Figure 7, when matching the real part of the impedance of Z1, the matching device 21 adjusts C1 to make the real part of the front-end impedance change from the ● position to the ▲ position. When matching the real part of the impedance of Z2, the matching device 21 adjusts C1 to make the real part of the front-end impedance change from the ■ position to the ▲ position. It can be seen that the distance of the change when matching Z1 is smaller than the distance of the change when matching Z2. In other words, compared with Z2, the change of C1 when matching the real part of the impedance of Z1 is smaller.

[0063] For the matching circuit 21 in the L-type matching network, when matching the real part of the impedance of Z1, the value of C1 is increased to change the real part of the front-end impedance from the ● position to the ▲ position; similarly, when matching the real part of the impedance of Z2, the value of C1 is increased to change the real part of the front-end impedance from the ■ position to the ▲ position. Therefore, the larger the change in C1, the larger the adjusted C1 value, and the smaller the change in C1, the smaller the adjusted C1 value.

[0064] It can be seen that for the matching circuit 21 of the L-type matching network, the real impedance of Z1 is greater than the real impedance of Z2, and the capacitance value of C1 required by the matching circuit 21 when matching Z1 is less than the capacitance value of C1 required by the matching circuit 21 when matching Z2.

[0065] We can assume that if Z load When the real part of the impedance decreases (e.g., Z1 becomes Z2), then C1 in the matching circuit 21 is equivalent to adjusting the capacitance value from the real part of the impedance when matching Z1 to the real part of the impedance when matching Z2. Since the capacitance value of C1 required by the matching circuit 21 when matching Z1 is less than the capacitance value required by the matching circuit 21 when matching Z2, therefore, when Z... load When the real part of the impedance decreases, the capacitance value of C1 needs to be increased. Conversely, if Z... load When the real part of the impedance increases (e.g., Z2 becomes Z1), the capacitance value of C1 needs to be reduced.

[0066] In other words, substituting the above conclusions into Figure 6, Z load The real part of the impedance is Z_load_r. The larger Z_load_r is, the smaller C1 is. Similarly, the smaller Z_load_r is, the larger C1 is, and vice versa. A smaller C1 also implies a larger Z_load_r, and a larger C1 also implies a smaller Z_load_r.

[0067] Based on the above principles, as shown in Figure 8, the control method disclosed in this application includes:

[0068] Step S10: Under the first output power of the power supply, complete impedance matching and obtain the first matching state of the matching device 21.

[0069] Step S20: Adjust the power supply to the second output power to complete impedance matching and obtain the second matching state of the matching device 21.

[0070] Step S30: Compare the parameter changes of matcher 21 in the first matching state and the second matching state;

[0071] Step S40: Based on the comparison results, adjust the parameters corresponding to the first matching state of the matcher 21 so that after the power supply is restored to the first output power, the power fed into the load unit increases when the coupling efficiency of the plasma decreases.

[0072] The stability of a plasma is closely related to the characteristic that its coupling efficiency varies with its feed power. During semiconductor processing, byproducts are gradually generated within the process chamber, altering the plasma state and reducing its feed power. When the feed power decreases while the plasma coupling efficiency (i.e., the proportion of feed power absorbed by the plasma) increases, the plasma is in a negative feedback state, and the matching system is stable. Conversely, when the plasma feed power decreases and the coupling efficiency further decreases, the plasma is in a positive feedback state, and the matching system is prone to mismatch or even quenching. Therefore, if the plasma state can be predicted in advance and the entire matching system is pre-set to a negative feedback state, the stability of the matching system can be greatly improved.

[0073] The specific method for predicting the state of the plasma in advance is as follows: By changing the output power of the power supply, a controllable load change is actively introduced. That is, the feed power of the load unit changes accordingly with the output power of the power supply, thereby causing a change in the resistance R2 of the plasma, and consequently affecting the Z-axis of the load unit. load A change has occurred. Matcher 21 detects Z... load After the change, its parameters (the size of the first adjustable capacitor C1) will be automatically adjusted to accommodate the changed Z. load Matching is performed. During this matching process, the direction of change of the parameter (the value of the first adjustable capacitor C1) can be monitored to determine Z. load The change in the real part of the impedance allows us to determine whether the resistance R2 of the plasma is located to the left or right of the peak point in Figure 6. Specifically, taking an L-shaped matching network of the matching unit 21 as an example, if the output power of the power supply decreases, the capacitance of the first adjustable capacitor C1 increases, then Z... load The real part of the impedance decreases, meaning that as the plasma resistance R2 increases, Z... load When the real part of the impedance decreases, the resistance of the plasma R2 is located to the right of the peak point in Figure 6; if the output power of the power supply decreases, the capacitance of the first adjustable capacitor C1 decreases, then Z load As the real part of the impedance increases, that is, as the resistance R2 of the plasma increases, Z... load As the real part of the impedance increases, the resistance of the plasma R2 is located to the left of the peak point in Figure 6.

[0074] The specific method for pre-setting the entire matching system to a negative feedback state is as follows: Taking the matching network of matcher 21 as an L-type network as an example, if the resistance R2 of the plasma is located to the right of the peak point in Figure 6 (manifested as an increase in the capacitance of the first adjustable capacitor C1), the parameter (first adjustable capacitor C1) can be proactively set to be slightly larger than the value at the matching point based on the first matching state of matcher 21. When the feed power decreases due to external disturbances, causing the resistance R2 of the plasma to increase, Z load When the real part of the impedance decreases, the plasma coupling efficiency increases due to the pre-increased parameters, and the entire matching system is in a negative feedback state, which effectively prevents plasma quenching and makes the system more stable. If the resistance R2 of the plasma is located to the left of the peak point in Figure 6 (manifested as a decrease in the capacitance of the first adjustable capacitor C1), the parameter (the first adjustable capacitor C1) can be proactively set to be slightly smaller than the value at the matching point based on the first matching state of the matcher 21. When the feed power decreases due to external disturbances, causing the plasma resistance R2 to increase, Z load When the real part of the intermediate impedance increases, the plasma coupling efficiency increases due to the parameter reduction in advance. The entire matching system is in a negative feedback state, which can effectively prevent plasma quenching and make the system more stable.

[0075] As can be seen from the above, by determining the state of the plasma in advance and setting the parameters of the matcher 21 accordingly, it is possible to provide Z load The real part of the impedance is prepared in advance with a controllable impedance margin to cope with dynamic adjustments during power disturbances. This allows the matched device 21 to better match the Z impedance after the change when the plasma feed power decreases due to external disturbances. load Matching, which in turn increases the coupling efficiency of the plasma, allows the entire matching system to be in a negative feedback state, effectively preventing plasma quenching and thus making the system more stable.

[0076] Step S30 also includes the following steps:

[0077] Step S31: In the first matching state of the matcher 21, obtain the first capacitance value of the first adjustable capacitor C1;

[0078] Step S32: In the first matching state of the matcher 21, obtain the second capacitance value of the first adjustable capacitor C1;

[0079] Step S33: Compare the first capacitance value with the second capacitance value.

[0080] Based on the aforementioned conclusion, by comparing the first and second capacitance values ​​of the first adjustable capacitor C1, we can reflect the value of Z. loadBy observing the change in the real part of the impedance of Zload, it can be determined whether the resistance of R2 is located to the left or right of the peak point in Figure 6. This allows for better assessment of the impact of Zload on the real part of the impedance when the input power decreases. load The trend of the change of the real part of the impedance is predicted.

[0081] Taking the matching network of the matching unit 21 as an L-type network as an example, when the second output power is less than the first output power, the feed power decreases and the resistance of R2 increases. When the matching is stable, if the second capacitance value is greater than the first capacitance value, that is, the capacitance value of the first adjustable capacitor C1 increases, it indicates that as the resistance of R2 increases, Z... load The real part of the impedance, Z_load_r, decreases. Therefore, the resistance of the plasma, R2, is located to the right of the peak point in Figure 6. Conversely, if the second capacitance value is less than the first capacitance value, meaning the capacitance value of the first adjustable capacitor C1 decreases, it indicates that as the resistance of R2 increases, Z_load_r... load The real part of the impedance, namely Z_load_r, increases, therefore, the resistance of the plasma R2 is to the left of the peak point in Figure 6.

[0082] Therefore, based on the above principles, step S40 further includes the following steps:

[0083] Step S41: If the second capacitance value is greater than the first capacitance value, adjust the capacitance value of the first adjustable capacitor C1 to the third capacitance value, which is greater than the first capacitance value.

[0084] When the second capacitance value is greater than the first capacitance value, it indicates that as the resistance of R2 increases, Z_load_r decreases. The resistance of the plasma R2 is located to the right of the peak point in Figure 6. The capacitance value of the first adjustable capacitor C1 can be set to a third capacitance value that is slightly larger than the first capacitance value. When the input power decreases, since the capacitance value of the first adjustable capacitor C1 is preset to the third capacitance value, the Z_load_r after the input power decreases will be more matched with the capacitance value of the first adjustable capacitor C1, thereby increasing the input power. This avoids the slow response of the actuator and the occurrence of mismatch, making the matching more stable.

[0085] Step S42: If the second capacitance value is less than the first capacitance value, adjust the capacitance value of the first adjustable capacitor C1 to the fourth capacitance value, which is less than the first capacitance value.

[0086] When the second capacitance value is less than the first capacitance value, it means that as the resistance of R2 increases, Z_load_r increases. The resistance of the plasma R2 is to the left of the peak point in Figure 6. The capacitance value of the first adjustable capacitor C1 can be set to a slightly smaller fourth capacitance value. When the input power decreases, since the capacitance value of the first adjustable capacitor C1 is preset to the fourth capacitance value, the Z_load_r after the input power decreases will be more matched with the capacitance value of the first adjustable capacitor C1, thereby increasing the input power and avoiding the occurrence of slow response and mismatch of the actuator, making the matching more stable.

[0087] It should be noted that in this embodiment, the difference between the first output power and the second output power is greater than or equal to 5W and less than or equal to 20W. In other words, the output power of the power supply cannot be reduced too much during the adjustment process to ensure the stability of the system.

[0088] It should also be noted that if the difference between the third and fourth capacitance values ​​and the first capacitance value is too large, the reflected power will also be greater, thus affecting the feed efficiency. Therefore, in order to ensure the feed efficiency, the difference between the first and third capacitance values ​​is 0.2% to 2% of the adjustment range of the first variable capacitor. The difference between the first and fourth capacitance values ​​is 0.2% to 2% of the adjustment range of the first variable capacitor.

[0089] It should be noted that in the above embodiment, the matching network 21 is an L-shaped matching network, but this is not limiting. That is to say, the matching network 21 can also use other matching networks, as long as it has a real part adjustment element for matching the real part of the load impedance of the load unit. The magnitude of the real part of the impedance of the load unit can be changed by adjusting the real part adjustment element.

[0090] As shown in Figure 9, another embodiment also discloses a semiconductor process apparatus with the same structure as the above embodiment, except that in this embodiment, the matching device 21 is a T-type network. In the T-type network matching device 21, L is still the inductor in the matching network, C1 is still the first adjustable capacitor used to match the real part of the impedance of the load unit, and C2 is still the second adjustable capacitor used to match the imaginary part of the impedance of the load unit.

[0091] However, unlike the L-type matching network matching device 21, for the T-type matching network matching device 21, when matching the real part of the impedance of Z1, the value of C1 is decreased to change the real part of the impedance at the front end of the matching device 21 from the ● position to the ▲ position; similarly, when matching the real part of the impedance of Z2, the value of C1 is also decreased to change the real part of the impedance at the front end of the matching device 21 from the ■ position to the ▲ position. Therefore, the larger the change in C1, the smaller the adjusted C1 value, and the smaller the change in C1, the larger the adjusted C1 value.

[0092] It can be seen that for the matching circuit 21 of the T-type matching network, the real part of the impedance of Z1 is greater than the real part of the impedance of Z2, and the capacitance value of C1 required when matching circuit 21 matches Z1 is greater than the capacitance value of C1 required when matching circuit 21 matches Z2.

[0093] We can assume that if Z load When the real part of the impedance decreases (e.g., Z1 becomes Z2), then C1 in the matching circuit 21 is equivalent to adjusting from the capacitance value matching the real part of Z1 to the capacitance value matching the real part of Z2. Since the capacitance value of C1 required by the matching circuit 21 to match Z1 is greater than the capacitance value required by the matching circuit 21 to match Z2, therefore, when Z... load When the real part of the impedance decreases, the capacitance value of C1 also needs to be reduced. Conversely, if Z... load When the real part of the impedance increases (for example, Z2 becomes Z1), the capacitance value of C1 needs to be increased.

[0094] In other words, substituting the above conclusions into Figure 6, Z load The real part of the impedance is Z_load_r. The larger Z_load_r is, the larger C1 is. Similarly, the smaller Z_load_r is, the smaller C1 is. Conversely, the larger C1 is, the larger Z_load_r is, and the smaller C1 is, the smaller Z_load_r is.

[0095] Based on the T-type network matching device 21 in another embodiment shown in Figure 9, this application also discloses a control method that is basically the same as the control method in the embodiment shown in Figure 5, except that the result of determining whether the resistance value of resistor R2 is located to the left or right of the peak point in Figure 6 by comparing the first capacitance value and the second capacitance value of the first adjustable capacitor C1 is different.

[0096] Specifically, when using a matching circuit 21 with a T-type matching network, if the second output power is less than the first output power, the feed power decreases, and the resistance of R2 increases. Once the matching stabilizes, if the second capacitance value is greater than the first capacitance value, meaning the capacitance of the first adjustable capacitor C1 increases, it indicates that as the resistance of R2 increases, Z... loadThe real part of the impedance, Z_load_r, increases. Therefore, the resistance of the plasma, R2, is to the left of the peak point in Figure 6. The capacitance of the first adjustable capacitor C1 can be set to a third capacitance value, slightly larger than the first value. When the input power decreases, the pre-set capacitance of the first adjustable capacitor C1 will better match the Z_load_r after the input power decreases with the capacitance of the first adjustable capacitor C1, thereby increasing the input power and preventing slow actuator response and mismatch, resulting in a more stable match. Conversely, if the second capacitance value is smaller than the first capacitance value, meaning the capacitance of the first adjustable capacitor C1 decreases, it indicates that as the resistance of R2 decreases, Z_load_r... load The real part of the impedance, Z_load_r, becomes smaller. Therefore, the resistance of the plasma R2 is located to the right of the peak point in Figure 6. The capacitance of the first adjustable capacitor C1 can be set to a slightly smaller fourth capacitance value. When the input power decreases, since the capacitance of the first adjustable capacitor C1 is preset to the fourth capacitance value, the Z_load_r after the input power decreases will be more matched with the capacitance value of the first adjustable capacitor C1, thereby increasing the input power. This avoids the slow response of the actuator and the occurrence of mismatch, making the matching more stable.

[0097] The semiconductor process equipment of this application includes a controller comprising at least one processor and at least one memory, wherein the memory stores a computer program, and the computer program is executed by the processor to implement the control method described above.

[0098] As shown in Figure 4, the semiconductor process equipment also includes an inlet assembly, a lower electrode assembly 30, and a controller. The controller includes at least one processor and at least one memory, in which a computer program is stored. When the computer program is executed by the processor, it implements the method of any of the above embodiments.

[0099] For example, the controller can be a host computer or a slave computer. The controller can open the valve of the air intake assembly to introduce the corresponding process gas into the process chamber 10; the controller can also control the opening and closing degree of the valve of the air intake assembly to control the flow rate of the process gas. The controller can also control the air extraction assembly to evacuate the interior of the process chamber 10, thereby controlling the pressure inside the process chamber 10 and removing reaction byproducts.

[0100] The lower electrode assembly 30 includes a wafer carrier 31, a lower RF power supply, and a lower matching unit 32. The controller is also used to control the lower RF power supply to provide lower electrode power to the lower electrode of the wafer carrier 31 through the lower matching unit 32, so that the lower electrode of the wafer carrier 31 provides RF bias voltage to attract plasma above the object to be etched and bombard the object to be etched.

[0101] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this application, and this application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this application, and these modifications and improvements are also considered to be within the scope of protection of this application.

Claims

1. A control method for a radio frequency (RF) system in semiconductor process equipment, the RF system comprising: A power supply, a matching unit, and a coil are provided. The power supply is electrically connected to the input terminal of the matching unit, and the output terminal of the matching unit is electrically connected to the coil. The coil is used to excite process gas within a process chamber to form plasma. The coil and the plasma form a load unit. The control method includes: At the first output power of the power supply, impedance matching is completed, and the first matching state of the matching device is obtained; Adjust the power supply to the second output power to complete impedance matching and obtain the second matching state of the matching device; Compare the parameter changes of the matcher in the first matching state and the second matching state; Based on the comparison results, the parameters are adjusted according to the parameters corresponding to the first matching state of the matcher so that after the power supply is restored to the first output power, the power fed into the load unit increases when the coupling efficiency of the plasma decreases.

2. The control method according to claim 1, characterized in that, The matching device includes: a real part adjustment element for matching the real part of the load impedance of the load unit; the step of comparing the parameter changes of the matching device in the first matching state and the second matching state includes: The parameter changes of the real part adjustment element are compared between the matcher in the first matching state and the second matching state.

3. The control method according to claim 2, characterized in that, The real part adjustment element is a first adjustable capacitor; comparing the parameter changes of the real part adjustment element in the first matching state and the second matching state of the matched circuit specifically includes: In the first matching state of the matcher, the first capacitance value of the first adjustable capacitor is obtained; In the second matching state of the matcher, the second capacitance value of the first adjustable capacitor is obtained; Compare the first capacitance value with the second capacitance value.

4. The control method according to claim 3, characterized in that, The step of adjusting the parameters based on the comparison results and the parameters corresponding to the first matching state of the matcher, so that the power supply is restored to the first output power, and increasing the power fed into the load unit when the coupling efficiency of the plasma decreases, specifically includes: When the second output power is less than the first output power, If the second capacitance value is greater than the first capacitance value, then the first adjustable capacitor is adjusted to a third capacitance value, which is greater than the first capacitance value; If the second capacitance value is less than the first capacitance value, then the first adjustable capacitor is adjusted to a fourth capacitance value, which is less than the first capacitance value.

5. The control method according to claim 4, characterized in that, The difference between the first capacitance value and the third capacitance value is 0.2% to 2% of the adjustment range of the first variable capacitor.

6. The control method according to claim 4, characterized in that, The difference between the first capacitance value and the fourth capacitance value is 0.2% to 2% of the adjustment range of the first variable capacitor.

7. The control method according to claim 1, characterized in that, The difference between the first output power and the second output power is greater than or equal to 5W and less than or equal to 20W.

8. The control method according to claim 2, characterized in that, The load impedance of the load unit is Where R1 is the equivalent resistance of the coil, ZM is the mutual inductance impedance between the coil and the plasma in the process chamber, R2 is the resistance of the plasma in the process chamber, and Z... L2 The inductive reactance is the plasma equivalent in the process chamber.

9. A radio frequency system, characterized in that, Control is performed using the control method described in any one of claims 1 to 8.

10. A semiconductor process apparatus, characterized in that, include: A process chamber, a radio frequency system, and a controller, the controller comprising at least one processor and at least one memory, the memory storing a computer program that, when executed by the processor, implements the control method according to any one of claims 1 to 8.

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