Plasma etching apparatus and method of frequency modulation thereof

Abstract

The application provides a plasma etching device and a frequency modulation method thereof. The device comprises a reaction chamber and a radio frequency power supply, and is used to realize a plasma process comprising at least two sequentially circulating steps, each step comprising a process transition phase and a process stable phase. The method comprises: during the process transition phase of each step, controlling the radio frequency power supply to work at a fixed frequency, which is a preset initial frequency corresponding to the corresponding step; after each step enters the process stable phase, adjusting the frequency of the radio frequency power supply to obtain a matching frequency corresponding to the corresponding step in the current cycle. When each step is executed for the first time, the frequency of the radio frequency power supply is adjusted starting from the preset initial frequency corresponding to the corresponding step; when each step is executed for the second time, the frequency of the radio frequency power supply is adjusted starting from the matching frequency of the corresponding step in the previous cycle. The application can realize fast and accurate matching of plasma impedance in the plasma process with step cycle switching.

Description

Technical Field

[0001] This invention relates to the field of plasma process technology, and in particular to a plasma etching apparatus and its frequency modulation method. Background Technology

[0002] Deep silicon etching is an advanced process for fabricating high aspect ratio (high depth, narrow linewidth) microstructures on silicon substrates. It is widely used in optical devices, MEMS devices, power devices, 3D integration and packaging, and its core technologies include the Bosch process. Typically, the Bosch process involves a cyclical sequence of polymer deposition (Dep) – polymer etching (Etch) – silicon etching (Etch) to achieve a balance between conformal etching and high etching rates.

[0003] As etching linewidths decrease (e.g., linewidth < 0.1µm) and etching depths increase (e.g., depth > 5µm), Bosch's process faces increasing challenges. Specifically, the Dep-Etch-Etch cycle time becomes shorter (e.g., on the order of 0.1s), necessitating a corresponding increase in step switching speed. In practice, switching between the deposition gas (e.g., C4F8) and the etching gas (e.g., SF6) causes drastic fluctuations in the gas type, pressure, and flow rate within the reaction chamber. This transition process can last for tens of milliseconds (e.g., 40 milliseconds). During this transition period, the plasma impedance undergoes rapid and unsteady changes, making it difficult to quickly achieve impedance matching, thus affecting process accuracy and repeatability. Summary of the Invention

[0004] In order to achieve rapid and accurate matching of plasma impedance in plasma processes with cyclic switching steps, thereby improving process accuracy and repeatability, this invention provides a plasma etching apparatus and its frequency modulation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a frequency modulation method for a plasma etching apparatus, the plasma etching apparatus comprising a reaction chamber and a radio frequency power supply for implementing a plasma process, the plasma process comprising at least two sequentially cyclically executed steps, wherein different process conditions are used in different steps, and each step comprises a process transition phase and a process stabilization phase, the method comprising: During the process transition phase of each of the aforementioned steps, the radio frequency power supply is controlled to operate at a fixed frequency, which is a preset initial frequency corresponding to the respective step. Once each step has reached the process stabilization stage, the frequency of the radio frequency power supply is adjusted to obtain the matching frequency corresponding to the step in the current cycle. The matching frequency is used to match the impedance of the radio frequency power supply with the impedance of the reaction chamber. Specifically, when each step is executed for the first time, the frequency of the radio frequency power supply is adjusted starting from the preset initial frequency corresponding to the step. When each step is not executed for the first time, the frequency of the radio frequency power supply is adjusted starting from the matching frequency of the step in the previous cycle.

[0006] In one feasible embodiment, the process transition phase of each of the steps ends when any of the following conditions are met, and the process enters the process stabilization phase of the corresponding step: The duration reaches the transition duration pre-configured for the corresponding step; The reflected power of the radio frequency power supply reaches a stable state.

[0007] In one feasible approach, the start and stop of each step are triggered by control commands issued by the main controller of the plasma etching equipment according to a preset process timing, and the frequency modulation method identifies the start and end times of each step according to the control commands.

[0008] In one feasible approach, adjusting the frequency of the radio frequency power supply includes: adjusting the frequency of the radio frequency power supply according to the reflected power of the radio frequency power supply until the reflected power is minimized, thereby obtaining the matching frequency corresponding to the step in the current cycle.

[0009] In one feasible approach, the frequency of the radio frequency power supply is adjusted by invoking an automatic frequency modulation algorithm configured for the corresponding step.

[0010] In one feasible embodiment, the plasma process is a Bosch process, and the at least two sequentially cyclic steps include one or more etching steps and one or more deposition steps.

[0011] In one feasible approach, the preset initial frequency corresponding to each step is pre-calibrated based on preset process conditions for the corresponding step, including gas type, gas flow rate, chamber pressure, and radio frequency power.

[0012] Secondly, the present invention provides a plasma etching apparatus, the apparatus comprising a reaction chamber and a radio frequency power supply, and for implementing a plasma process, the plasma process comprising at least two sequentially cyclically executed steps, wherein the process conditions configured for different steps are different, and each step comprises a process transition phase and a process stabilization phase, wherein the apparatus further comprises a frequency modulation module configured to execute the method described above.

[0013] In one feasible embodiment, the radio frequency power supply includes a source radio frequency power supply and a bias radio frequency power supply, and the frequency modulation module is configured to perform the method described above for the source radio frequency power supply and the bias radio frequency power supply, respectively.

[0014] In one feasible embodiment, the device is an inductively coupled plasma etching apparatus or a capacitively coupled plasma etching apparatus.

[0015] By adopting the above technical solution, the present invention has the following advantages over the prior art: This invention addresses plasma processes requiring cyclic switching of process steps. By controlling the RF power supply to operate and maintain a preset initial frequency during the process transition phase of each step, it fundamentally avoids the "misleading" frequency modulation caused by invalid responses and drastically fluctuating impedance signals in traditional continuous frequency modulation methods during this period, ensuring process stability during the disturbance period. Once the process stabilizes, a frequency modulation process is initiated to seek impedance matching. For the first step executed, the preset initial frequency is used as the optimization starting point for frequency modulation. For steps not executed for the first time, a cross-cycle frequency modulation experience reuse mechanism is introduced. That is, the matching frequency of the previous successful matching in the corresponding step is directly used as the search starting point for the current frequency modulation. This allows the previously effective impedance matching to provide better initial conditions for the matching process in subsequent cycles, thereby achieving iterative improvement in matching efficiency and convergence speed, and thus improving the process accuracy and repeatability of plasma processes, especially suitable for high aspect ratio etching and ultra-high aspect ratio etching. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the implementation principle of the frequency modulation method in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the plasma etching equipment in an embodiment of the present invention. Detailed Implementation

[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0018] It should be noted that the illustrations provided in the embodiments are only schematic representations of the basic concept of the present invention. Although the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation, the shape, quantity, positional relationship and proportion of each component in the actual implementation can be changed at will under the premise of realizing the technical solution of the present invention, and the layout of the components may also be more complex.

[0019] In plasma etching equipment, the radio frequency power supply transmits radio frequency energy to the reaction chamber through an impedance matching device to excite the process gas in the reaction chamber to form plasma. The excited plasma contains a large number of active particles such as electrons, ions, excited-state atoms, molecules and free radicals. These active particles interact with the wafer, causing various physical and chemical reactions on the surface of the wafer material, thereby completing the wafer etching or deposition process.

[0020] During the transmission of radio frequency (RF) energy, the output impedance of the RF power supply is typically 50 ohms, while the input impedance of the reaction chamber is typically a non-50 ohm impedance with both real and imaginary impedances. This leads to an impedance mismatch between the two. In this case, if RF energy is directly transmitted to the reaction chamber, RF energy reflection will occur, meaning that not enough RF energy will be transmitted to the reaction chamber, thus preventing the normal excitation of the plasma.

[0021] Currently, impedance matching between the RF power supply and the reaction chamber can be achieved by adjusting the frequency of the RF power supply or the matching capacitor within the impedance matching circuit. For plasma impedance matching in Bosch processes, this is typically achieved by adjusting the frequency of the RF power supply. Specifically, this involves real-time monitoring of plasma impedance or reflected power information and rapid adjustment of the RF frequency (i.e., frequency modulation) based on the monitored information to ensure that the matching circuit and the reaction chamber achieve the target impedance with minimal power loss (e.g., 50 Ohms).

[0022] Based on existing data acquisition and processing capabilities, the frequency modulation rate of RF power supplies is typically in the microsecond (µs) or even nanosecond (ns) range. Under stable process conditions (such as relatively constant pressure, gas flow, and gas type), the plasma ignition process is roughly on the order of 10µs-30µs, so impedance matching can be achieved with frequency modulation in tens of microseconds.

[0023] However, in a typical Bosch process, process steps (hereinafter referred to as steps) are cyclically switched, involving rapid switching between polymer deposition systems (usually C4F8 systems) and etching systems (usually SF6 systems). During the switching process, the gas type, pressure, and flow rate in the reaction chamber fluctuate drastically for tens of milliseconds, typically around 40 ms (of which the switching time of gas valves is on the order of 10 ms, and the gas flow from the valves into the chamber takes approximately 20-30 ms). This continuous and drastic perturbation of process conditions causes drastic changes in plasma impedance. If a traditional continuous frequency modulation method is used at this time, it will continuously respond to invalid and fluctuating impedance signals and issue incorrect frequency adjustment commands accordingly. This "misleading" frequency modulation will prevent impedance matching from happening quickly, and the reflected power will not be effectively suppressed and converge to a minimum value within tens of milliseconds after the switching is completed, affecting process accuracy and repeatability.

[0024] In view of this, the present invention provides a plasma etching apparatus and its frequency modulation method, and creatively proposes to divide each step of the cyclic execution into two phases with different characteristics in the time dimension—a process transition phase and a process stabilization phase. The process transition phase refers to the period from the start of the step (e.g., the end of the preceding step or the start of process gas switching) until its process conditions (e.g., gas type, pressure, flow rate) begin to stabilize. The essential characteristic of this phase is the drastic change in process conditions and rapid, non-steady-state fluctuations in plasma impedance. The process stabilization phase, on the other hand, refers to the subsequent phase where the process conditions have stabilized at the set value, and the plasma impedance enters a relatively slow, steady-state variation range.

[0025] Based on the above classification, the inventors propose the following frequency modulation strategy, which is completely different from the traditional continuous frequency modulation method: During the process transition phase: Due to the invalidity and severe disturbances in impedance information during this phase, attempting to track its changes through "frequency modulation" is futile and even harmful. Therefore, the inventors devised a "fixed-frequency anti-interference" strategy: controlling the RF power supply to operate at a fixed frequency—a preset initial frequency pre-calibrated for this step—actively suspending the frequency adjustment function. This is not passive inaction, but rather an active "noise-ignoring" intelligent decision-making process. Its purpose is to provide a stable and reliable frequency reference during periods of drastic process condition changes, preventing the system from being misled by invalid signals and creating conditions for subsequent precise matching.

[0026] During the process stabilization phase: Since the process conditions are stable at this stage, the changes in plasma impedance become regular and traceable. Therefore, this invention initiates a precise frequency tuning process at this stage. Simultaneously, this invention further proposes an "experience-guided rapid frequency tuning" mechanism: intelligently selecting the starting point for frequency tuning based on whether a step is being executed for the first time. For steps being executed for the first time, frequency tuning starts from the aforementioned preset initial frequency; for steps not being executed for the first time, the matching frequency corresponding to the same step in the previous process cycle is directly used as the starting frequency for this step's frequency tuning. This mechanism allows successful matching experience to be effectively reused, guiding subsequent frequency tuning processes from "global search" to "local optimization," achieving a significant improvement in matching speed and accuracy.

[0027] In summary, this invention fundamentally overturns the traditional continuous frequency modulation mode, effectively avoids the matching trap during the ineffective disturbance period, and accelerates matching based on historical experience within the effective window period. Thus, it systematically solves the core problem of impedance matching sluggishness and inaccuracy in high-speed cyclic Bosch processes, specifically bringing the following advantages: (1) It fundamentally solves the problem of mismatch during the switching disturbance period of each step: For plasma processes that require rapid cyclic switching of steps, this invention controls the RF power supply to work at a fixed frequency of the preset initial frequency during the process transition phase of each step, which effectively avoids the "misleading" frequency modulation caused by the invalid response and drastic fluctuation of the impedance signal in the traditional continuous frequency modulation method during this period, and ensures that the RF energy and process status are basically stable during the process switching period.

[0028] (2) Iterative optimization of matching speed and efficiency was achieved: By introducing a cross-cycle frequency modulation experience reuse mechanism—for steps that are not executed for the first time, the matching frequency obtained in the previous cycle is directly used as the starting point for the current frequency modulation in the process stabilization stage, so that successful impedance matching can provide a search initial point closer to the optimal solution for subsequent cycles. This realizes the transformation of the matching process from "broad search" to "directional optimization", which significantly improves the convergence speed and efficiency of frequency modulation, and is especially suitable for deep silicon etching processes that require hundreds or thousands of cycles.

[0029] (3) Significantly improved overall process performance: The improved impedance matching speed and accuracy directly translate into a more stable and controllable plasma environment. This makes the control of etching profile (sidewall roughness and perpendicularity) more precise, the uniformity of critical dimensions (CD) better, and significantly improves the process repeatability between wafers and batches.

[0030] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] Example 1 This embodiment provides a frequency modulation method for a plasma etching apparatus, which includes a reaction chamber and a radio frequency power supply, and is used to implement a plasma process (such as the Bosch process) comprising at least two sequentially cyclic process steps (hereinafter referred to as steps). The different process conditions used in each step are different, and each step includes a process transition phase and a process stabilization phase.

[0032] like Figure 1 As shown, the frequency modulation method in this embodiment specifically includes: during the process transition phase of each step, controlling the radio frequency power supply to operate at a fixed frequency of the preset initial frequency corresponding to the corresponding step; after each step enters the process stabilization phase, starting the adjustment of the radio frequency power supply frequency to obtain the matching frequency corresponding to the corresponding step in the current cycle, which is used to match the impedance of the radio frequency power supply with the impedance of the reaction chamber.

[0033] Specifically, this embodiment pre-sets a corresponding preset initial frequency for each step, which serves as the fixed frequency used by each step during the process transition phase in all cycles. Once each step enters the process stabilization phase, the starting frequency for frequency adjustment is determined based on whether the step is being executed for the first time: if it is being executed for the first time (i.e., in the first cycle), the adjustment starts from the preset initial frequency corresponding to that step; if it is not being executed for the first time, the adjustment starts from the matching frequency obtained by the same step in the previous cycle. The preset initial frequency corresponding to each step can be pre-calibrated based on the process conditions configured for the corresponding step.

[0034] exist Figure 1 In the example shown, the plasma process includes, for instance, a cyclical switching of two process steps: a first step of deposition (Dep) and a second step of etching (Etch). Each step comprises a sequentially executed process transition phase and a process stabilization phase, with the different phases shown as boundaries defined by vertical dashed lines. Figure 1 In the equation, Dep Pr represents the reflected power during the deposition step, Dep freq represents the RF frequency of the RF power supply during the deposition step, Etch Pr represents the reflected power during the etching step, Etch freq represents the RF frequency of the RF power supply during the etching step, and δT d δT represents the duration of the process transition phase in the deposition step. e This represents the duration of the process transition phase in the etching step, and Step ij represents the j-th step in the i-th cycle. In this embodiment, a preset initial frequency f is set for the first step (i.e., the deposition step). d0 Set the corresponding preset initial frequency f for the second step (i.e., the etching step). e0 Radio frequency matching is achieved through the following progressive adjustment method: In the first cycle, the deposition step is performed first. During the process transition phase of the deposition step, the RF power supply is controlled at a preset initial frequency f. d0 The process is run and kept constant; once the deposition step enters the stable phase, the preset initial frequency f corresponding to that step is used. d0 Frequency tuning is performed starting from this point to obtain the matching frequency f corresponding to the deposition step in the first cycle. d1 The process then switches to the etching step, during which the RF power supply is switched to a preset initial frequency f during the process transition phase. e0 Run and maintain a constant frequency; after the etching step enters the process stabilization stage, use the preset initial frequency f corresponding to that step. e0 Frequency tuning is performed starting from the first cycle to obtain the matching frequency f of the etching step. e1 .

[0035] In the second cycle, the deposition step is performed first, and during its process transition phase, the RF power supply is still controlled at a preset initial frequency f. d0 Run and maintain a constant frequency; once the deposition step enters the process stabilization phase, since it is not the first execution, use the matching frequency f obtained from the previous cycle. d1 The frequency of the RF power supply is adjusted to obtain the matching frequency f corresponding to the deposition step in the second cycle. d2 Then, the process switches to the etching step, and during its transition phase, the RF power supply is still controlled at a preset initial frequency f. e0 Run and maintain a constant frequency; after the etching step enters the process stabilization stage, since this is not the first execution, use the matching frequency f obtained from the previous cycle. e1 The frequency of the RF power supply is adjusted to obtain the matching frequency f corresponding to the etching step in the second cycle. e2 .

[0036] Subsequent loops follow the same procedure as the second loop, and so on, until all loops are completed.

[0037] This embodiment maintains a constant frequency during the process transition phase of each process step, which avoids misleading frequency tuning caused by process condition switching. After entering the process stabilization phase, it performs progressive adjustment based on the matching frequency of the corresponding step at the end of the previous cycle. This not only improves the response speed of RF matching, but also enhances the repeatability and stability of the process, which is beneficial for achieving high-precision plasma processes.

[0038] To precisely control the progress of each step and improve efficiency, this embodiment detects whether the following conditions are met during the process. When any of the following conditions are met, the process transition phase of the corresponding step is determined to have ended and the process enters the corresponding stable phase: (1) The duration of the process transition phase has reached the fixed transition duration pre-configured for the corresponding step (e.g., the fixed transition duration of the deposition step is configured as δT). d The fixed transition time for the etching step is configured as δT e ).

[0039] (2) The reflected power of the radio frequency power supply (such as Dep Pr or Etch Pr) is monitored to reach a stable state, wherein the stable state can be defined as the fluctuation amplitude of the reflected power continuously within a preset threshold range.

[0040] By setting the above judgment conditions, while taking into account the preset timing control, we can actively respond to the actual physical state changes in the reaction chamber, ensure process repeatability, and optimize cycle time.

[0041] In this embodiment, the plasma process is automatically controlled by the main controller of the etching equipment according to the timing logic defined in the preset process recipe. That is, the start and stop of each process step are triggered by control commands issued by the main controller according to the preset process timing. Specifically, before the process starts, the operator or system preloads the process recipe into the main controller. This recipe specifies in detail the execution order of each step, the process conditions of each step (such as gas type, gas flow rate, pressure, RF power, etc.), and the switching timing between steps. When the process cycle starts, the main controller becomes the core command unit of the entire equipment. According to the timing in the recipe, it precisely issues control commands to the relevant subsystems at the set time points or after the completion conditions of specific preceding steps are met. For example, when it is necessary to switch from the deposition step to the etching step, the main controller will issue a command to close the process gas valve in the deposition gas path required for the deposition step after the stable phase of the deposition step ends or its termination conditions are met, and simultaneously open the process gas valve in the etching gas path required for the etching step. The rhythm, synchronization, and coordination of the entire process are centrally managed by the main controller, thereby ensuring a high degree of automation, precise repeatability, and excellent consistency of the process cycle.

[0042] In this embodiment, once any step reaches its process stabilization stage, a frequency adjustment process is initiated to dynamically adjust the output frequency based on the real-time monitored reflected power of the RF power supply. Specifically, the adjustment process involves using a determined starting frequency (a preset initial frequency or the matching frequency from the previous cycle) as the optimization starting point, calling a preset automatic frequency tuning algorithm to iteratively fine-tune the frequency, and continuously comparing changes in reflected power until the reflected power is adjusted to convergence. At this point, it indicates that the optimal impedance matching state has been reached, and the frequency at this moment is locked as the matching frequency (e.g., f) corresponding to that step in the current cycle. d1 f e1 ).

[0043] In this embodiment, the same or different automatic frequency modulation algorithms can be configured for each step. That is, each step can call the exact same general frequency modulation algorithm, or different frequency modulation algorithms can be configured and used according to their unique process requirements, such as differentiation in frequency modulation strategy, adjustment step size, or convergence tolerance. When a process step is determined to have entered its stable phase, the automatic frequency modulation algorithm pre-configured for that step is automatically invoked to execute the frequency adjustment process described above, which aims to minimize reflected power. This achieves highly adaptive, accurate, and efficient RF matching, improving the overall repeatability, uniformity, and reliability of the process.

[0044] It should be understood that, although Figure 1 The plasma process shown in the example includes only one deposition (Dep) and one etching (Etch) step, but this is merely a simplified example to clearly illustrate the basic principles of this embodiment. The method of this embodiment is fully applicable to complex cyclic processes containing more steps. For example, a cycle may contain one deposition step and two etching steps with different process conditions, such as the Dep1-Etch1-Etch2 cycle; or, a cycle may contain two deposition steps with different process conditions and two etching steps with different process conditions, such as the Dep1-Etch1-Dep2-Etch2 cycle. This embodiment does not impose any specific limitations on this.

[0045] It should be noted that regardless of the number and type of steps in the loop, each step follows the same frequency modulation strategy: during its process transition phase, the RF power supply always operates at a fixed frequency—the preset initial frequency corresponding to that step; during its process stabilization phase, the frequency modulation process is initiated—if this step is being executed for the first time in the current loop, frequency modulation is performed starting from its preset initial frequency; if it is not being executed for the first time, frequency modulation is performed starting from the matching frequency obtained in the same step of the previous loop, thereby obtaining the matching frequency for this loop and updating the storage. In this way, even in complex loops containing multiple deposition and etching variants, this embodiment can ensure that each step can intelligently utilize its own historical matching experience during its stabilization phase to achieve fast and stable impedance matching.

[0046] Example 2 This embodiment provides a plasma etching apparatus, such as... Figure 2As shown, the device includes a deposition gas path 1, an etching gas path 2, a plasma source matcher 3, a source RF power supply 4, a bias source matcher 5, a bias RF power supply 6, a main controller 7 (such as a PLC), a frequency modulation module 8, an RF coil 9, an inlet nozzle 10, a dielectric window 11, an electrostatic chuck 13 (also called a base) supporting the wafer 12, a gas distribution ring 14, a reaction chamber 15, and an exhaust port 16. In Example 1, the RF power supply can refer to either the source RF power supply 4 or the bias RF power supply 6. The switching of process gases is achieved through valves in the deposition gas path 1 and the etching gas path 2.

[0047] In this embodiment, the reaction chamber 15 is the core cavity for plasma processing. A dielectric window 11 is located at its top, and an RF coil 9 is positioned above the dielectric window 11. The RF coil 9 is connected to a source RF power supply 4 to generate an alternating electromagnetic field to excite the process gas. The process gas is delivered via a deposition gas path 1 or an etching gas path 2 and injected through an inlet nozzle 10 located at the top of the reaction chamber 15. Under the influence of the electromagnetic field, it is excited and dissociated, forming plasma containing active particles. These active particles diffuse and are guided by the electric field to the surface of the wafer 12, where they undergo physical bombardment or chemical reaction, thereby achieving material etching or deposition. Finally, the reaction gas and byproducts are discharged through the exhaust port 16 at the bottom. During the process, the wafer 12 is supported and fixed by an electrostatic chuck 13, which is connected to a bias RF power supply 6 to adjust the ion energy bombarding the surface of the wafer 12.

[0048] exist Figure 2 In the example shown, the frequency modulation module 8 establishes communication connections with the main controller 7, the source RF power supply 4, and the bias RF power supply 6. The main controller 7 is responsible for controlling the process operation according to the preset process recipe and sending timing instructions for step switching to the frequency modulation module 8. The frequency modulation module 8 executes the frequency modulation method provided in Example 1 based on these instructions: during the process transition phase of each process step, it controls the corresponding RF power supply (source RF power supply 4 and / or bias RF power supply 6) to operate at a fixed frequency of the preset initial frequency corresponding to that step; when the step enters the process stabilization phase, the frequency modulation process is initiated—if this is the first execution of the step, the preset initial frequency is used as the optimization starting point; if it is not the first execution, the matching frequency obtained in the same step of the previous cycle is used as the optimization starting point, and the frequency of the RF power supply is automatically adjusted until the matching frequency that minimizes the reflected power is obtained, thereby achieving impedance matching between the RF power supply and the reaction chamber. The matching frequency obtained in each cycle will provide an optimized starting point for frequency modulation of the same process step in the process stabilization phase of the next cycle, and the efficiency and speed of the matching process are continuously improved through this experience reuse mechanism.

[0049] In one feasible approach, the frequency modulation module is configured to independently execute the frequency modulation method of Embodiment 1 for the source RF power supply 4 and the bias RF power supply 6, respectively. This means that for the source RF power supply 4 that excites the plasma and the bias RF power supply 6 that controls the ion energy, the frequency modulation module maintains two independent but logically identical control sequences: locked to a dedicated fixed frequency during the process transition phase, and independently performing frequency modulation optimization during the process stabilization phase, while recording and reusing their respective matching frequencies.

[0050] It should be pointed out that, Figure 2 The frequency modulation module 8 is shown as a standalone entity, only to clearly illustrate its functional principle. In actual equipment, this module can be integrated in various ways: for example, it can be integrated into the software system of the main controller 7; or it can be embedded in the internal controllers of the source RF power supply 4 and the bias RF power supply 6 respectively, making it an RF power supply with intelligent frequency modulation capability. Regardless of the physical integration method used, as long as the control strategy of "fixed frequency anti-interference in the transition phase, fast matching in the stable phase, and cross-cycle frequency learning" in Embodiment 1 is implemented, it falls within the protection scope of this invention.

[0051] Alternatively, the device in this embodiment can be Figure 2 The inductively coupled plasma (ICP) etching equipment shown can also be a capacitively coupled plasma (CCP) etching equipment. This embodiment does not impose specific restrictions on the type of equipment.

[0052] This embodiment uses frequency modulation module 8 to implement the frequency modulation method of embodiment 1. In the high-speed circulating plasma process, it achieves the unity of "anti-interference stability", "fast and accurate matching" and "experience self-learning", improves impedance matching efficiency, provides key radio frequency environment guarantee for the contour control and uniformity necessary to achieve high aspect ratio etching, and improves the robustness of equipment capacity and process formulation.

[0053] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A frequency modulation method for a plasma etching apparatus, the plasma etching apparatus comprising a reaction chamber and a radio frequency power supply, and used to implement a plasma process, the plasma process comprising at least two sequentially cyclically executed steps, wherein different process conditions are used in different steps, and each step comprises a process transition phase and a process stabilization phase, characterized in that, The method includes: During the process transition phase of each of the aforementioned steps, the radio frequency power supply is controlled to operate at a fixed frequency, which is a preset initial frequency corresponding to the respective step. After each step enters the process stabilization stage, the frequency of the radio frequency power supply is adjusted to obtain the matching frequency corresponding to the step in the current cycle. The matching frequency is used to match the impedance of the radio frequency power supply with the impedance of the reaction chamber. When each step is executed for the first time, the frequency of the radio frequency power supply is adjusted starting from the preset initial frequency corresponding to the step. When each step is not executed for the first time, the frequency of the radio frequency power supply is adjusted starting from the matching frequency of the corresponding step in the previous cycle.

2. The frequency modulation method as described in claim 1, characterized in that, The process transition phase of each step ends when any of the following conditions are met, and the process enters the process stabilization phase of the corresponding step: The duration reaches the transition duration pre-configured for the corresponding step; The reflected power of the radio frequency power supply reaches a stable state.

3. The frequency modulation method as described in claim 1, characterized in that, The start and stop of each step are triggered by control commands issued by the main controller of the plasma etching equipment according to the preset process timing, and the frequency modulation method identifies the start and end times of each step according to the control commands.

4. The frequency modulation method as described in claim 1, characterized in that, Adjusting the frequency of the radio frequency power supply includes: adjusting the frequency of the radio frequency power supply according to the reflected power of the radio frequency power supply until the reflected power is minimized, thereby obtaining the matching frequency corresponding to the step in the current cycle.

5. The frequency modulation method as described in claim 4, characterized in that, The frequency of the radio frequency power supply is adjusted by invoking the automatic frequency tuning algorithm configured for the corresponding steps.

6. The frequency modulation method as described in claim 1, characterized in that, The plasma process is a Bosch process, and the at least two sequentially cyclic steps include one or more etching steps and one or more deposition steps.

7. The frequency modulation method as described in claim 1, characterized in that, The preset initial frequency corresponding to each step is obtained by pre-calibration based on the process conditions configured for the corresponding step, including gas type, gas flow rate, chamber pressure and radio frequency power.

8. A plasma etching apparatus, the apparatus comprising a reaction chamber and a radio frequency power supply, and for performing a plasma process, the plasma process comprising at least two sequentially cyclically executed steps, wherein the process conditions configured for different steps are different, and each step comprises a process transition phase and a process stabilization phase, characterized in that, The device further includes a frequency modulation module configured to perform the frequency modulation method as described in any one of claims 1-7.

9. The plasma etching apparatus as described in claim 8, characterized in that, The radio frequency power supply includes a source radio frequency power supply and a bias radio frequency power supply. The frequency modulation module is configured to execute the frequency modulation method for the source radio frequency power supply and the bias radio frequency power supply, respectively.

10. The plasma etching apparatus as described in claim 8, characterized in that, The device is an inductively coupled plasma etching device or a capacitively coupled plasma etching device.

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