A gas switching method for semiconductor apparatuses

Abstract

The application discloses a gas switching method for a semiconductor device, comprising the following steps: S1, obtaining a process recipe, wherein the process recipe comprises at least a first process step and a second process step which are alternately executed; each process step corresponds to a preset gas switching time and a power switching time; the semiconductor device is controlled to run according to the process recipe for at least three cycles, and process parameters in the running process of each process step are recorded, wherein the process parameters comprise reflected power; S2, based on the recorded reflected power, the time difference average AT of the characteristic time of each process step from the power switching time is calculated respectively, wherein the characteristic time is the time corresponding to the highest point of the slope of the reflected power; S3, the gas switching time of the corresponding process step is updated according to the time difference average AT; S4, the process recipe is run again until the process parameters meet the conditions. The application can directly and accurately judge the gas switching time in real time, and realize the dynamic adjustment of the gas switching time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a gas switching method for semiconductor equipment. Background Technology

[0002] In semiconductor manufacturing processes, process formulations consist of multiple consecutive and distinct process steps. The switching between adjacent process steps often requires rapid gas switching. For example, in the Bosch process of ICP etching equipment, rapid gas switching is crucial for achieving high aspect ratio silicon etching. The main steps of this Bosch process are: Step 1 introduces SF6 gas for isotropic etching; Step 2 switches to C4F8 gas to deposit a polymer passivation layer on the exposed silicon surface (including the bottom and sidewalls). In the next etching cycle, vertical ion bombardment removes the bottom passivation layer to continue etching downwards, while the sidewall passivation layers are retained to suppress lateral etching. Through this "etch-passivation-etch" cycle, deep vertical etching is achieved.

[0003] Without implementing any gas switching timing judgment steps, existing technologies often simultaneously perform gas switching (e.g., switching from gas 1 to gas 2) and power switching when transitioning from one process step to the next. However, since power switching can be completed instantaneously, while gas switching involves a lag, this simultaneous operation leads to a period of instability within the chamber at the beginning of each process step, and severe mixing of gas components within the chamber (i.e., gas mixing). Currently achievable switching cycles reach 200-500 ms or even shorter, and the degree of gas mixing within the chamber becomes increasingly severe as the switching between the two different gases becomes faster. Figure 2 As shown, during process step switching, various conditions within the chamber (such as gas type, gas content, and gas pressure) change abruptly, leading to drastic changes in the chamber's impedance. The areas highlighted by the green dashed box in the figure represent unstable states. Since reflected power is the process parameter most sensitive to the chamber's state (i.e., impedance changes), its high level during this stage can easily damage power devices. Furthermore, the persistence of unstable states severely impacts the effective time of process steps, preventing the stable completion of process requirements.

[0004] To compensate for the lag caused by gas switching and overcome the aforementioned defects, the unstable state at the beginning of the process step switching can be avoided by performing the gas switching in advance. However, to implement this operation, the precise timing of the gas switching needs to be determined. Existing technologies mainly employ the following methods to determine the specific timing of the gas switching, but all have significant limitations: One approach is a control method based on fixed timing. This method sets fixed gas switching times for each process step based on experience. However, when chamber pressure, temperature, or equipment status fluctuates, the fixed time cannot guarantee the actual effect of gas switching. In other words, the process effect of this method is highly dependent on the initial settings and experience, making it difficult to guarantee consistent process results on different machines or at different times.

[0005] The second method is plasma emission spectroscopy (OES). This method determines the reaction progress by monitoring specific spectral intensities. However, the spectral characteristic peaks in the process chamber are prone to overlap and are affected by parameter fluctuations, making data interpretation complex. More importantly, OES detects the signal of the reaction products, rather than the intake action itself, resulting in an inherent physical delay. In addition, OES sensors are expensive and require frequent maintenance in corrosive environments.

[0006] In summary, the existing technology lacks a detection and control method that can reflect the moment of gas switching in the chamber in real time, directly and accurately, resulting in bottlenecks in the process in terms of accuracy, efficiency and consistency.

[0007] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0008] The purpose of this invention is to provide a method that can determine the gas switching time in real time, directly and accurately, so as to realize the dynamic adjustment of the gas switching time and avoid problems such as high reflection power, easy damage to power devices, and inability to stably meet process requirements caused by unstable state in the chamber during gas switching.

[0009] To achieve the above objectives, the present invention provides a gas switching method for semiconductor devices, comprising: S1. Obtain a process formula, wherein the process formula includes at least a first process step and a second process step, the first process step and the second process step are executed alternately, and the set parameters in the first process step and the second process step are different; wherein, each process step corresponds to a preset gas switching time and power switching time, the semiconductor device is controlled to run according to the process formula for at least 3 cycles, and the process parameters during the operation of each process step are recorded, wherein the process parameters include reflection power. S2. Based on the recorded reflected power, calculate the average time difference ΔT between the characteristic time of each process step and the power switching time of that process step. The characteristic time is the time corresponding to the highest slope of the reflected power. S3. Update the gas switching time of the corresponding process step according to the average time difference ΔT of each process step; if the characteristic time lags behind the power switching time of the corresponding process step, advance the gas switching time of the process step by ΔT; if the characteristic time is ahead of the power switching time of the corresponding process step, delay the gas switching time of the process step by ΔT. S4. Update the gas switching time in each process step, and run the process formula again until the process parameters meet the conditions.

[0010] Optionally, in step S2, a curve relating reflection power to time is constructed based on the continuously recorded reflection power in each process step, and the characteristic moment is determined by the curve relating reflection power to time.

[0011] Optionally, in step S2: the characteristic time of each process step is subtracted from the power switching time of that process step and the absolute value is taken to obtain the time difference between the characteristic time of that process step and the power switching time. The average value of the multiple time differences obtained by the same process step in multiple cycles is calculated to obtain the average value of the time difference ΔT.

[0012] Optionally, in the process of averaging multiple time differences for the same process steps, after removing the maximum and minimum values ​​among the multiple time differences, the average of the remaining time differences is calculated.

[0013] Optionally, before step S1, the parameters set include: gas type, gas flow rate, gas pressure, and radio frequency power for each process step; The process parameters also include the concentration and pressure of each gas in the process chamber.

[0014] Optionally, the semiconductor device includes a radio frequency (RF) power supply for providing RF power to the process chamber of the semiconductor device; in step S1, the reflected power of the RF power reflected back to the RF power supply is detected in real time by a power sensor disposed in the RF power supply, and the reflected power is transmitted to the host computer for recording in real time.

[0015] Optionally, the types of gases and / or the process conditions of the gases corresponding to the first process step and the second process step are different.

[0016] Optionally, the first process step is a deposition process step, and the corresponding gas is a deposition gas; the second process step is an etching process step, and the corresponding gas is an etching gas.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention overcomes the limitations of traditional fixed-sequence control, enabling real-time, direct, and accurate determination of gas switching moments. By extracting the reflected power, which is most sensitive to changes in cavity impedance, as the core monitoring parameter, and calculating the time difference between the moment corresponding to the highest slope of the reflected power in each step and the power switching moment of that step, the precise delay or advance time of gas switching is obtained. Furthermore, if the current process parameters do not meet the conditions, the time difference and gas switching moment are updated again through iterative loops, thereby achieving dynamic feedforward adjustment of the gas switching moment.

[0018] 2. This invention effectively compensates for the inherent time lag between gas switching and instantaneous power switching by precisely determining and adjusting the gas switching timing. This mitigates the drastic impedance fluctuations caused by sudden changes in various parameters such as gas type, content, and pressure within the chamber. This mechanism reduces the reflected power spikes at the initial stage of process step switching, significantly lowering the risk of damage to the machine's power devices from high reflected power, extending equipment lifespan, and reducing maintenance costs.

[0019] 3. By accurately determining and adjusting the gas switching time, this invention maximizes the effective time of each process step and ensures that the entire process can stably and consistently meet the stringent process requirements, ultimately improving the process consistency and overall efficiency of semiconductor manufacturing. Attached Figure Description

[0020] Figure 1 A schematic diagram of a semiconductor device including a gas rapid switching system for performing the method of the present invention; Figure 2 This is a schematic diagram illustrating the changes in process parameters when gas switching and power switching are performed simultaneously in the prior art. Figure 3 This is a flowchart of the gas switching method according to an embodiment of the present invention; Figure 4 This is a schematic diagram showing the changes in process parameters after using the method of the present invention. Detailed Implementation

[0021] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the gas switching method for semiconductor devices proposed by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of the present invention. Please refer to the drawings to make the objectives, features, and advantages of the present invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0022] To facilitate understanding and implementation of the gas switching method of the present invention, the structure of the semiconductor device performing the method is illustrated below with reference to the accompanying drawings. It should be understood that the structure of the semiconductor device is not limited to the form shown in the drawings.

[0023] Taking inductively coupled plasma etching equipment as an example, such as Figure 1 As shown, the semiconductor device includes: The process chamber 1 is equipped with an electrostatic chuck 2 for holding a wafer 3; a dielectric window is provided on the top of the process chamber 1, and an induction coil 6 is provided on the top of the dielectric window. Radio frequency power supply 4 is connected to the induction coil 6 through a first matching unit 5 to provide radio frequency power of a specific frequency (e.g., 13.56 MHz) to the induction coil 6. The induction coil 6 generates an electromagnetic field after receiving the radio frequency power. The electromagnetic field is coupled into the interior of the process chamber 1 to excite the process gas in the process chamber 1 to form plasma. A high-voltage power supply 7 is connected to the electrostatic chuck 2 to provide high-voltage DC power to the electrostatic chuck 2, thereby generating electrostatic adsorption force to fix the wafer 3. The bias power supply 8 is connected to the radio frequency electrode built into the electrostatic chuck 2 through the second matching unit 9, and is used to output a radio frequency bias voltage of a specific frequency (such as 400 KHz) to the radio frequency electrode. After the radio frequency bias voltage is applied to the radio frequency electrode, it generates a self bias voltage on the wafer 3, thereby accelerating the bombardment of the wafer 3 surface by ions in the plasma. The gas supply system 10 includes a deposition gas source and an etching gas source, and is connected to the process chamber through corresponding gas supply pipelines; a first gas valve 11 and a second gas valve 12 are respectively installed on the two gas supply pipelines to control the deposition gas and etching gas to enter the process chamber, so as to realize the switching of reaction gases for different process steps. The optical emission spectrometer (HT-OES) 13 is installed on the side wall of the process chamber and is used to monitor the intensity of plasma emission spectrum in the process chamber in real time. The vacuum pump unit is connected to the process chamber through the exhaust port and is used to evacuate the process chamber to maintain the vacuum level required by the process or to remove the exhaust gas after the reaction. The control system 14 is electrically connected to the radio frequency power supply 4, high voltage power supply 7, bias power supply 8, first gas valve 11, second gas valve 12 and optical emission spectrometer 13, and is used to control the opening and closing or operating parameters of the above components.

[0024] This invention provides a gas switching method for semiconductor devices, such as... Figure 3 As shown, the gas switching method includes the following steps: S1. Obtain a process recipe, which includes at least a first process step and a second process step. The first process step and the second process step are executed alternately, and the set parameters in the first process step and the second process step are different. Each process step corresponds to a preset gas switching time and a power switching time. Control the semiconductor device to run according to the process recipe for at least 3 cycles, and record the process parameters during the operation of each process step, including the reflected power.

[0025] The parameters set for each process step in the process formula include: gas type, gas flow rate, gas pressure, and radio frequency power for each process step.

[0026] The parameters set in the first process step and the second process step are different, including at least one of the following situations: the types of gases corresponding to the first process step and the second process step are different; the process conditions of the gases corresponding to the first process step and the second process step are different. Wherein, the different process conditions of the gases include at least one of the following situations: different gas flow rates; different gas pressures.

[0027] In one specific embodiment, the first process step is a deposition process step, and the corresponding gas is a deposition gas; the second process step is an etching process step, and the corresponding gas is an etching gas. For example, in the Bosch process of an ICP etching machine, the first process step introduces C4F8 gas to deposit a polymer passivation layer on the exposed silicon surface, and the second process step introduces SF6 gas for isotropic etching. The first process step and the second process step are executed alternately.

[0028] Each process step involves gas switching at the corresponding gas switching time and power switching at the corresponding power switching time.

[0029] The RF power supply of the semiconductor device provides RF power to the process chamber of the semiconductor device, and the portion of the RF power reflected back to the RF power supply is the reflected power. The power switching is achieved by the RF power supply directly changing the set value of its output RF power, so that the RF power in the process chamber switches within a very short time.

[0030] The gas switching is achieved through, for example... Figure 1 The illustrated rapid gas switching system achieves this. The rapid gas switching system includes a gas supply system connected to the process chamber via at least two gas supply lines. A first gas valve and a second gas valve are respectively installed on the two gas supply lines. Deposition gas output from the gas supply system enters the process chamber via the gas supply line containing the first gas valve, and etching gas output from the gas supply system enters the process chamber via the gas supply line containing the second gas valve. When the first gas valve is open and the second gas valve is closed, the deposition gas (e.g., C4F8) enters the process chamber and is excited into plasma under the action of radio frequency power. The active species (e.g., CF2 free radicals) in the plasma undergo a polymerization reaction on the wafer surface, forming a fluorocarbon polymer film that provides passivation. When the first gas valve is closed and the second gas valve is open, the etching gas (e.g., SF6) enters the process chamber and is excited into plasma under the action of radio frequency power. The active species (e.g., fluorine free radicals) in the etching gas react chemically with the wafer surface to generate volatile products (e.g., SiF4), thereby producing isotropic chemical etching of the exposed silicon. Therefore, by controlling the continuous opening and closing of the first and second gas valves, the switching of different process gases can be achieved.

[0031] The gas valve switching time is defined as the gas switching time; the RF power output power switching time is defined as the power switching time.

[0032] In step S1 (i.e., initially), the power switching time and gas switching time are the same for each process step. In this case, due to the physical response time of gas flow and diffusion in the gas supply line and the process chamber, the gas switching has an inherent time lag compared to the instantaneous power switching of the RF power supply.

[0033] Preferably, the semiconductor equipment is controlled to run for 3 to 9 cycles according to the process formula, for example, 5 cycles, thereby effectively eliminating random fluctuations that may occur in a single run, ensuring the statistical reliability of the subsequent calculation time difference, and avoiding the impact on production efficiency due to too many running cycles.

[0034] During operation, process parameters for each process step are recorded. The method for recording the reflected power is as follows: the reflected power reflected back to the RF power source is detected in real time by a power sensor installed in the RF power source, and the reflected power is transmitted to the host computer for recording in real time.

[0035] The recorded process parameters also include the concentration and pressure of each gas in the process chamber, to characterize the transition state of components in the process chamber during gas switching.

[0036] S2. Based on the recorded reflected power, calculate the average time difference ΔT between the characteristic time of each process step and the power switching time of that process step. The characteristic time is the time corresponding to the highest slope of the reflected power.

[0037] Specifically, a curve relating reflection power to time is constructed based on the continuously recorded reflection power in each process step, and the characteristic moment is determined through the curve relating reflection power to time.

[0038] Subsequently, the characteristic time of each process step is subtracted from the power switching time of that process step, and the absolute value is taken to obtain the time difference between the characteristic time and the power switching time of that process step. The average of the multiple time differences obtained by the same process step in multiple cycles is then calculated to obtain the average time difference ΔT.

[0039] Optionally, in the process of averaging multiple time differences for the same process steps, after removing the maximum and minimum values ​​among the multiple time differences, the average of the remaining time differences is calculated.

[0040] For example, a trial run of 5 cycles is conducted, with each cycle consisting of a first process step and a second process step. The time differences of the first process step within the 5 cycles are calculated as ta1, ta2, ta3, ta4, and ta5, respectively; the time differences of the second process step within the 5 cycles are also calculated as ta1, ta2, ta3, ta4, and ta5, respectively. Then, the average time differences of the first and second process steps are calculated as ΔT1 and ΔT2, respectively. Depending on the actual situation, if the state within the process chamber is unstable at the beginning or end of the previous cycle, resulting in excessively large or small time differences within that cycle, a step can be added to the calculation process to remove the maximum and minimum time difference values ​​before calculating the average.

[0041] S3. Update the gas switching time of the corresponding process step according to the average time difference ΔT of each process step; if the characteristic time lags behind the power switching time of the corresponding process step, advance the gas switching time of the process step by ΔT; if the characteristic time precedes the power switching time of the corresponding process step, delay the gas switching time of the process step by ΔT.

[0042] In step S3, only the gas switching time is updated, while the other condition change times, including the power switching time, remain unchanged.

[0043] Since the power switching time and gas switching time of each process step are initially set to the same time, and gas switching has an inherent time lag compared to power switching, the characteristic time will inevitably lag behind the power switching time of the corresponding process step when the gas switching time is updated for the first time. At this time, the gas switching time of each process step is advanced. After one update, and when the subsequent step S4 determines that the gas switching time needs to be updated again, the characteristic time may lag behind the power switching time of the corresponding process step, indicating that the previous advance was insufficient. In this case, the gas switching time is further advanced based on the average time difference ΔT after the update. Alternatively, the characteristic time may advance ahead of the power switching time of the corresponding process step, indicating that the previous advance was excessive. In this case, the gas switching time is delayed accordingly based on the average time difference ΔT after the update.

[0044] This invention calculates the advance or delay of the gas switching time based on the time corresponding to the highest point of the reflected power slope. The specific principle is as follows: In the process chamber, the gas is ionized into plasma under the excitation of radio frequency power. Plasma generated by gases with different compositions has different impedance characteristics. Spectral fluctuations directly reflect plasma state fluctuations. In deposition and etching processes, the characteristic spectral lines corresponding to the process gas are the critical spectral lines. When the intensity of all critical spectral lines remains stable, it means that the current process state is in a stable phase. During gas switching, the intensity of the characteristic spectral lines of the original gas gradually decreases over time, while the intensity of the characteristic spectral lines of the new gas gradually increases from the background noise and eventually reaches stability. This spectral intensity data intuitively reflects the complete transition process of the new gas reaching the predetermined concentration and plasma steady state in the process chamber.

[0045] Furthermore, at the transient point where the gas actually undergoes replacement within the process chamber (significantly later than the valve switching moment), a drastic jump in spectral intensity is often observed. At this time, the chemical composition of the plasma changes rapidly and significantly, directly leading to a sudden change in plasma impedance. Since the reflected power is the process parameter most sensitive to impedance changes, it typically exhibits a corresponding peak or drastic fluctuation due to this impedance abrupt change, subsequently gradually returning to a stable state as the new gas becomes stable.

[0046] During the aforementioned transition process, the moment when the plasma impedance change within the process chamber is most drastic corresponds to the highest point of the slope of the reflected power change. This is the physical critical point where the gas state within the chamber changes from being dominated by the gas required in the previous process step (e.g., gas 2) to being dominated by the gas required in the current process step (e.g., gas 1). Therefore, this invention extracts the moment corresponding to the highest point of the reflected power slope as a characteristic moment, which can accurately characterize the actual physical moment when the gas and plasma states undergo a substantial switch. Based on this, the advance or delay amount required for the gas switching moment can be accurately calculated, thereby precisely dividing the actual dominant time of the gas required for each process step into the corresponding process time, so as to maximize the extension of the dominant time of the required gas in each process step.

[0047] S4. After updating the gas switching time in each process step, run the process formula again until the process parameters meet the conditions.

[0048] Specifically, in step S4, the process formula is run again for at least 3 cycles according to the gas switching time updated in step S3, and the process parameters and process results when the process formula is run again are recorded. The process parameters include the reflection power. It is also determined whether the process results meet the process requirements, and the process parameters are evaluated to determine whether the conditions are met by verifying the process results. If the conditions are met, the gas switching time of each current process step will be determined as the final gas switching time. If the conditions are not met, the process returns to step S2 based on the reflected power recorded when the process formulation is run again to update the mean time difference ΔT. In step S3, the gas switching time is updated for each process step using the updated mean time difference ΔT.

[0049] The determination of whether the process results meet the process requirements includes determining whether at least one of the following indicators meets the corresponding preset requirements: sidewall roughness; bottom morphology; wafer intra-wafer uniformity; and inter-wafer uniformity. The criteria for determining the bottom morphology include whether roughness, spikes, or microgrooves are present.

[0050] Changes in process parameters when the gas switching time is not adjusted, such as Figure 2As shown, the types of gases, their concentrations, and reflected power within the chamber change abruptly during process step switching. The areas highlighted by the green dashed box in the figure represent unstable states. In unstable states, the reflected power is high, which can easily damage power devices. Furthermore, upon entering step 2, the concentration of gas 2 remains higher, indicating that the gas type required in the process formulation of step 1 still dominates during this period, rather than the gas type required in step 2. This severely impacts the effective time of the process steps, leading to an inability to stably meet process requirements. The effective time refers to the duration during which the concentration of the gas type required for any given process step is dominant within the process chamber. For example, the effective time in step 1 represents the time during which gas 2 is dominant in step 1, and the effective time in step 2 represents the time during which gas 1 is dominant in step 2.

[0051] The changes in process parameters after adjusting the gas switching timing using the method of this invention are as follows: Figure 4 As shown in the figure, the area highlighted by the gray dashed box represents the unstable state. It can be seen that after adjusting the gas switching time, the reflected power decreased significantly, indicating a marked improvement in reflected power. Furthermore, during each process step, the gas in the process chamber was generally in a stable state, and the duration of the unstable state was significantly shortened, indicating a substantial improvement in the stable state. For example, upon entering step 2, the concentration of gas 2 decreased rapidly, while the concentration of gas 1 required for step 2 increased rapidly, resulting in a significant increase in the effective time of the process step.

[0052] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] In the description of this invention, it should be understood that the terms "center," "height," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0054] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0056] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A gas switching method for semiconductor devices, characterized in that, include: S1. Obtain a process formula, wherein the process formula includes at least a first process step and a second process step, the first process step and the second process step are executed alternately, and the set parameters in the first process step and the second process step are different; wherein, each process step corresponds to a preset gas switching time and power switching time, the semiconductor device is controlled to run according to the process formula for at least 3 cycles, and the process parameters during the operation of each process step are recorded, wherein the process parameters include reflection power. S2. Based on the recorded reflected power, calculate the average time difference ΔT between the characteristic time of each process step and the power switching time of that process step. The characteristic time is the time corresponding to the highest slope of the reflected power. S3. Update the gas switching time of the corresponding process step according to the average time difference ΔT of each process step; if the characteristic time lags behind the power switching time of the corresponding process step, advance the gas switching time of the process step by ΔT; if the characteristic time is ahead of the power switching time of the corresponding process step, delay the gas switching time of the process step by ΔT. S4. Update the gas switching time in each process step, and run the process formula again until the process parameters meet the conditions.

2. The gas switching method as described in claim 1, characterized in that, In step S2, a curve showing the relationship between reflection power and time is constructed based on the continuously recorded reflection power in each process step, and the characteristic moment is determined through the curve showing the relationship between reflection power and time.

3. The gas switching method as described in claim 1, characterized in that, In step S2: the characteristic time of each process step is subtracted from the power switching time of that process step and the absolute value is taken to obtain the time difference between the characteristic time of that process step and the power switching time. The average value of the multiple time differences obtained by the same process step in multiple cycles is calculated to obtain the average time difference ΔT.

4. The gas switching method as described in claim 3, characterized in that, In the process of averaging multiple time differences for the same process steps, after removing the maximum and minimum values ​​among the multiple time differences, the average of the remaining time differences is calculated.

5. The gas switching method as described in claim 1, characterized in that, Before step S1, the parameters set include: gas type, gas flow rate, gas pressure, and radio frequency power for each process step; The process parameters also include the concentration and pressure of each gas in the process chamber.

6. The gas switching method as described in claim 1, characterized in that, The semiconductor device includes an RF power supply for providing RF power to the process chamber of the semiconductor device; in step S1, the reflected power of the RF power reflected back to the RF power is detected in real time by a power sensor installed in the RF power supply, and the reflected power is transmitted to the host computer for recording in real time.

7. The gas switching method as described in claim 1, characterized in that, The first process step and the second process step correspond to different types of gases and / or different gas process conditions.

8. The gas switching method as described in claim 1, characterized in that, The first process step is a deposition process step, and the corresponding process gas is a deposition gas; the second process step is an etching process step, and the corresponding process gas is an etching gas.

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