Plasma interface stability control equipment and control method

Abstract

The invention relates to the technical field of plasma interface stability control, and discloses plasma interface stability control equipment and a control method. The method comprises the following steps: arranging a plurality of mutually independent transparent electrodes distributed along the axial direction between a reaction cavity quartz cylinder and a shielding cavity; periodic modulation voltages with spatial distribution differences are applied to the transparent electrodes respectively, so that the transparent electrodes form a modulation electric field with spatial phase differences in the reaction cavity; and under the action of the modulation electric field, a plasma interface in the reaction cavity generates controlled periodic oscillation, so that a stable space relationship between the plasma interface and the substrate is maintained. The stability and precision of the plasma interface position are improved.

Description

Technical Field

[0001] This invention relates to the field of plasma interface stabilization control technology, and in particular to a plasma interface stabilization control device and control method. Background Technology

[0002] Microwave plasma chemical vapor deposition (MPCVD) is used to synthesize high-quality diamond crystals. Existing techniques improve the overall spatial uniformity of plasma distribution by setting rotating magnetic fields and gas flow dispersion structures. However, during actual long-term deposition processes, the interface between the plasma sphere and the substrate still experiences drift, leading to uneven growth rates and unstable temperature distribution. Current control methods, which adjust macroscopic parameters such as microwave power, cavity pressure, and gas flow to maintain the plasma state, cannot effectively address the overall vertical drift, tilt drift, and local deformation of the plasma interface, resulting in step defects and polycrystalline nucleation, which severely affect the purity and structural integrity of the crystal. Summary of the Invention

[0003] The main objective of this invention is to provide a plasma interface stabilization control device and control method, which improves the accuracy of plasma interface position stability.

[0004] To achieve the above objectives, the present invention provides a plasma interface stabilization control method, comprising the following steps: Multiple independent transparent electrodes are arranged axially between the quartz cylinder of the reaction chamber and the shielding chamber; Periodic modulation voltages with spatially different distributions are applied to multiple transparent electrodes, causing the transparent electrodes to form a modulation electric field with a spatial phase difference within the reaction chamber. Under the action of the modulated electric field, the plasma interface in the reaction chamber generates controlled periodic oscillations, thereby maintaining a stable spatial relationship between the plasma interface and the substrate.

[0005] Optionally, in a first implementation of the first aspect of the present invention, the oscillation amplitude of the periodic oscillation is controlled within a preset amplitude range and the oscillation frequency is controlled within a preset frequency range, so as to avoid local collapse, tilting or positional drift and locking of the plasma interface.

[0006] Optionally, in a second implementation of the first aspect of the present invention, the parameters of the periodic modulation voltage are adjusted in a closed loop according to the plasma state detection signal, wherein the plasma state detection signal includes at least one of the following: plasma optical emission spectrum signal, temperature distribution signal within the reaction chamber, spatial position signal or morphology signal of the plasma interface.

[0007] Optionally, in a third implementation of the first aspect of the present invention, the plasma interface is identified as being in an overall vertical drift mode, a tilt drift mode, or a local deformation mode based on the plasma state detection signal, and the amplitude distribution and phase distribution of the periodic modulation voltage of the plurality of transparent electrodes are adjusted for different modes.

[0008] Optionally, in a fourth implementation of the first aspect of the present invention, adjusting the amplitude and phase distribution of the periodic modulation voltages of the plurality of transparent electrodes for different modes includes: When the overall vertical drift mode is identified, the periodic modulation voltages of all transparent electrodes are set to be in phase and have the same amplitude, so that the plasma interface will generate periodic oscillations along the vertical direction. When the tilt drift mode is identified, the phase difference of the periodic modulation voltage of each transparent electrode is set to a spatial gradient distribution according to the tilt direction, so that the tilt state of the plasma interface is corrected. When a local deformation mode is identified, the periodic modulation voltage amplitude of the transparent electrode corresponding to the deformation region is increased to restore the plasma interface of the local deformation region to the target shape.

[0009] Optionally, in a fifth implementation of the first aspect of the present invention, the periodic modulation voltage is an alternating voltage, and there is an adjustable phase difference between the modulation voltages of adjacent transparent electrodes, so as to form a spatially varying alternating electric field within the reaction chamber.

[0010] Optionally, in a sixth implementation of the first aspect of the invention, the controlled periodic oscillation homogenizes the plasma energy distribution in the time and spatial domains, thereby suppressing the accumulation of local overheating and step defects on the substrate surface.

[0011] This invention also provides a plasma interface stabilization control device, applied to a microwave plasma chemical vapor deposition (PVDC) apparatus, characterized in that it comprises: A reaction chamber, the reaction chamber comprising a quartz cylinder and a shielding cavity disposed outside the quartz cylinder; Multiple transparent electrodes are distributed along the axial direction of the quartz cylinder. The transparent electrodes are disposed between the quartz cylinder and the shielding cavity, and each transparent electrode is electrically insulated from the others. The multiple transparent electrodes are arranged at equal or non-equal intervals along the axial direction of the quartz cylinder to form an electric field gradient distribution that varies along the height direction of the reaction cavity. A modulation power supply module is electrically connected to the plurality of transparent electrodes respectively, and is used to apply a periodic modulation voltage with a spatial phase difference to each transparent electrode; The plurality of transparent electrodes form a spatially distributed modulated electric field during operation, causing controlled periodic oscillations at the plasma interface within the reaction chamber.

[0012] Optionally, in a first implementation of the second aspect of the present invention, the transparent electrode is made of a conductive transparent material, which has a preset transmittance in the microwave operating band to avoid interference with plasma optical monitoring and microwave energy coupling.

[0013] Optionally, in a second implementation of the second aspect of the present invention, a plasma state detection module and a control module are further included. The plasma state detection module is used to acquire plasma state detection signals, and the control module adjusts the amplitude, frequency, and phase parameters of the periodic modulation voltage output by the modulation power supply module according to the plasma state detection signals.

[0014] In summary, the present invention has the following beneficial effects: The core innovation of this invention lies not in the optimization of a single sensor configuration or control algorithm, but in applying a periodically modulated electric field with a phase difference through a spatially distributed transparent electrode array. This transforms the plasma interface stability problem from the traditional "eliminating fluctuations" paradigm to an active control paradigm of a "controllable oscillation system." This invention shifts the plasma interface stability problem from "pursuing static equilibrium" to "constructing controlled dynamic oscillations." By applying periodically modulated voltages with spatial phase differences to multiple independent transparent electrodes positioned between the quartz cylinder of the reaction chamber and the shielding chamber, the plasma interface generates controlled breathing-like periodic oscillations within a preset oscillation amplitude and frequency range. This maintains a stable spatial relationship between the interface and the substrate in a time-averaged sense, effectively avoiding the local energy concentration, spatial locking effect of carbon atom deposition rate, and long-term accumulation of step defects caused by the long-term fixed interface position in traditional static control methods.

[0015] This invention achieves a technological leap from coarse-scale overall control to refined spatial distribution control by identifying three typical dynamic modes of the plasma interface: overall vertical drift, tilt drift, and local deformation. For each mode, the amplitude and phase distribution of the modulation voltage of each transparent electrode are adjusted. When overall vertical drift occurs, all transparent electrodes are driven in phase to restore the overall interface oscillation. When tilt occurs, a directional correction torque is formed by setting a phase gradient between the electrodes. When local deformation occurs, the electric field intensity in the deformed region is directionally enhanced to achieve local correction. This pattern recognition-based differentiated spatial electric field control strategy essentially treats the plasma interface as a distributed oscillation system that can be actively controlled through multi-point excitation, overcoming the limitations of existing technologies that rely solely on macroscopic parameter adjustment.

[0016] By superimposing a periodic AC modulation component on the initial bias voltage, the spatially varying alternating electric field constructed in this invention dynamically homogenizes the plasma energy distribution in both the time and spatial domains, fundamentally suppressing the formation of localized overheated regions and polycrystalline nucleation on the substrate surface. Simultaneously, the multi-system collaborative control mechanism established in this invention organically combines the fine interface control of the transparent electrode array, the overall energy regulation of the microwave source, and the spatial distribution optimization of the rotating magnetic field device, forming a multi-level stable control system from overall to local, and from static to dynamic, thereby improving the accuracy of plasma interface positional stability and the process stability of long-term deposition processes. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the steps of a plasma interface stabilization control method in one embodiment of the present invention; Figure 2 This is a schematic diagram of the distribution of the transparent electrode array in one embodiment of the present invention.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Reference Figure 1 This embodiment provides a plasma interface stabilization control method, including the following steps: S11, Multiple independent transparent electrodes are arranged axially between the quartz cylinder of the reaction chamber and the shielding chamber; S12, apply periodic modulation voltages with spatially different distributions to multiple transparent electrodes respectively, so that the transparent electrodes form a modulation electric field with a spatial phase difference in the reaction chamber; S13, under the action of the modulated electric field, the plasma interface in the reaction chamber generates controlled periodic oscillations, thereby maintaining a stable spatial relationship between the plasma interface and the substrate.

[0021] In one example, an initial bias voltage is applied to multiple transparent electrodes positioned between the quartz cylinder of the reaction chamber and the shielding cavity, and reference state data of the plasma interface is acquired, including: An initial bias voltage of a preset voltage range is applied to transparent electrodes arranged at a preset spacing along the axial direction of the quartz cylinder, and a microwave source of a preset power range is activated to form a plasma ball from a hydrogen-methane mixture. The voltage of each transparent electrode is adjusted to stabilize the distance between the lower interface of the plasma ball and the substrate surface within the target distance range. The reference spectral intensity ratio of the plasma ball is collected, and the first temperature data of multiple temperature measurement points on the substrate surface are collected; the reference spectral intensity ratio and the first temperature data are used as reference state data.

[0022] In this example, a controllable electric field adjustment structure is constructed within the microwave plasma chemical vapor deposition (PCCVD) reaction chamber. This involves arranging several transparent electrodes at equal intervals along the axial direction between the quartz cylinder and the shielded cavity. The electrode structure employs a ring-shaped or segmented design to ensure sufficient spatial resolution and field uniformity. Each transparent electrode is connected to a controllable RF power supply or a DC bias power supply via an independent channel. After the hardware setup is complete, an initialization process is initiated. This involves synchronously applying an initial bias voltage within a set range to all transparent electrodes to establish a multi-gradient axial electric field distribution within the quartz cavity. Simultaneously, a gas delivery system introduces a hydrogen-methane mixture into the reaction chamber and stabilizes the internal working pressure. After the gas enters the cavity, the microwave source is activated, exciting gas molecules within the reaction chamber to form a suspended, stable plasma sphere. The morphology of the plasma sphere is controlled by the electric field distribution applied by the transparent electrodes. Therefore, the bias voltage level of each electrode is adjusted channel by channel to stabilize the spatial distance between the lower interface of the plasma sphere and the surface of the diamond substrate within the target distance range. After establishing a stable morphology, the emission spectrum of the plasma sphere is synchronously acquired using a multi-channel fiber optic spectral probe array positioned at different locations around the circumference of the reaction chamber. The characteristic spectral lines of CH radicals at 431 nm and C2 dimers at 516 nm are monitored, and their intensity ratio I_CH / I_C2 is calculated in real time. This ratio serves as a spectral parameter describing the proportion of active species and the chemical reaction state of the plasma, and also represents the distribution of plasma reaction intensity at different orientations and heights. Simultaneously, based on multiple infrared temperature measurement windows located on the sidewall of the quartz cylinder and corresponding array-type infrared detectors, initial temperature data is acquired at multiple key thermosensitive locations on the crystal substrate surface. Multiple temperature measurement points are deployed, covering both the central and edge regions, and the temperature values ​​obtained from each measurement point form the initial two-dimensional temperature field data. The spectral intensity ratio of the plasma sphere acquired within the period and the initial temperature data from multiple temperature measurement points on the substrate surface are used as the baseline state data for interface state initialization, uniformly stored in the control system state register, and an initial mapping relationship model between the plasma interface and the temperature field is established.

[0023] In one example, real-time state data of the plasma interface is acquired during diamond crystal deposition, including: During the diamond crystal deposition process, plasma emission spectra are collected by fiber optic spectral probes arranged in a circular pattern at different positions in the reaction chamber. The characteristic spectral lines of CH radicals and C2 dimers are monitored, and the real-time spectral intensity ratio of the characteristic spectral lines of CH radicals and C2 dimers is calculated. Second temperature data are collected from multiple temperature measurement points on the substrate surface using an infrared temperature measurement system; the real-time spectral intensity ratio and the second temperature data are used as real-time status data.

[0024] In this example, during the design phase of the reaction chamber structure, multiple fiber optic spectral acquisition interfaces are uniformly arranged along the circumferential direction at the same height on its sidewalls. At least six fiber optic spectral probes are installed, each corresponding to a different azimuth angle of the plasma sphere. The fiber optic system connected to the spectral probes is linked with the high-speed spectral analysis module and continuously acquires data. After the diamond single-crystal deposition process begins, a microwave source maintains a constant power to excite the hydrogen-methane mixture to form a stable plasma sphere. The plasma sphere emits an emission spectral signal containing multiple spectral line characteristics. The spectral probes receive the local emission intensity distribution at their respective azimuth angles in real time. Within the spectral analysis module, the peak intensities of the CH radical characteristic spectral line at 431 nm and the C2 dimer characteristic spectral line at 516 nm are extracted, and their ratios are calculated in real time to obtain the CH / C2 spectral intensity ratio I_CH / I_C2 corresponding to each azimuth angle. This ratio reflects the proportional relationship of active free radicals in the hydrocarbon components of the plasma reaction zone. Simultaneously, an infrared temperature measurement system, consisting of multiple infrared temperature measurement windows and corresponding infrared sensor arrays set on the outer wall of the quartz tube, performs real-time temperature measurement on multiple key temperature-controlled areas on the surface of the diamond substrate. The temperature measurement points cover heat-sensitive areas such as the center and edges of the wafer, with at least nine infrared channels deployed. The temperature values ​​collected by each measurement point constitute a second temperature data matrix for the current time point. This second temperature data is then integrated with the CH / C2 intensity ratios collected by each spectral probe to form a set of real-time plasma interface state data with spatial correlation and thermo-chemical coupling characteristics in each sampling cycle.

[0025] In one example, real-time state data is compared and analyzed with baseline state data to identify the overall vertical drift mode, tilt drift mode, or local deformation mode of the plasma interface and calculate the voltage adjustment for each transparent electrode, including: The difference between the real-time spectral intensity ratio and the reference spectral intensity ratio is calculated to obtain the spectral intensity ratio deviation vector at each angle. The standard deviation between the second temperature data and the first temperature data is calculated to obtain the temperature field deviation value. The directional consistency of the spectral intensity ratio deviation vector is judged. When the deviation directions of all directional components are the same and the difference in amplitude is less than a preset threshold, it is identified as an overall vertical drift mode. When the deviation of each directional component shows a linear gradient change and the gradient slope is greater than a preset gradient threshold, it is identified as a tilt drift mode and the tilt direction angle and tilt amplitude are calculated. When the deviation amplitude of a single directional component or two adjacent directional components exceeds a preset multiple of the average value of other directional components, it is identified as a local deformation mode and the deformation azimuth angle range is recorded. Calculate the voltage adjustment of each transparent electrode corresponding to the overall vertical drift mode, tilt drift mode, or local deformation mode.

[0026] In this example, a spectral ratio data structure corresponding to the azimuth angle is established. The real-time acquired CH / C2 spectral intensity ratio is matched one-to-one with the reference ratio recorded during the initialization phase. The difference is calculated at the azimuth angle corresponding to each spectral probe, forming a spectral intensity ratio deviation vector composed of multiple components, reflecting the current trend of plasma interface reactivity changes at different azimuth angles. Simultaneously, the second temperature data acquired in the current cycle is compared with the corresponding first temperature data. The standard deviation calculation method is used to extract the dispersion of temperature field changes, obtaining the current temperature field deviation value, which serves as a supplementary parameter for determining whether the plasma sphere interface height drift causes abnormal heat distribution. The control system performs directional consistency judgment on the spectral deviation vector, that is, checks whether the positive and negative signs of each component are consistent. If all components are positive or all are negative, and the difference in absolute deviation amplitude between each component is less than the preset threshold ε, it indicates that the plasma sphere is floating or sinking as a whole, and the interface is in a state of consistent height change. At this time, it is identified as an overall vertical drift mode. If each component changes continuously along the spatial azimuth angle and shows an obvious linear gradient trend, and the slope obtained by fitting is greater than the set minimum discrimination gradient threshold, it is identified as a tilt drift mode. The polar coordinate linear fitting algorithm is used to calculate the main direction of the gradient curve and the drift amplitude in that direction to describe the tilt characteristics of the plasma sphere in space. If the deviation amplitude of a certain azimuth component or its adjacent azimuth is found to be higher than the average value of the other azimuth components and exceeds the set multiple, it indicates that there is an abnormal accumulation of plasma density or a sudden local change in interface height in this area. It is identified as a local deformation mode, and the azimuth angle where the abnormal component is located is marked as the deformation zone. After identification, the control system inputs the identification results into the electric field response model. Combined with the pre-constructed voltage and interface response mapping matrix, it calculates the voltage adjustment of each transparent electrode accordingly. For the overall vertical drift mode, the voltage of all transparent electrodes increases or decreases simultaneously with the same adjustment range. For the tilt drift mode, the electrode voltage adjustment value is weighted according to the cosine function of the angle with the main tilt direction to form a balancing torque. For the local deformation mode, only the electrodes in the corresponding orientation are adjusted by direction, while the other electrodes remain unchanged or are slowly corrected to minimize unnecessary electric field disturbances.

[0027] In one example, the voltage adjustment of each transparent electrode corresponding to the overall vertical drift mode, tilt drift mode, or local deformation mode is calculated, including: When the overall vertical drift mode is identified, a uniform adjustment amount is calculated based on the average amplitude of the spectral intensity ratio deviation vector, and the uniform adjustment amount is used as the voltage adjustment amount for all transparent electrodes. When the tilt drift mode is identified, the cosine of the angle between the azimuth angle and the tilt direction angle of each transparent electrode is calculated, and the product of the cosine of the angle and the tilt amplitude is used as the voltage adjustment amount of each transparent electrode. When a local deformation mode is identified, the corresponding transparent electrode number is determined according to the deformation azimuth angle range, and the product of the temperature field deviation value and the preset response coefficient is used as the voltage adjustment amount of the transparent electrode within the deformation azimuth angle range.

[0028] In this example, when the overall vertical drift mode is identified, that is, when the spectral intensity ratio deviation of all azimuth angles is consistent in direction and similar in magnitude, the control system performs an arithmetic mean operation on all components of the spectral intensity ratio deviation vector to obtain the average deviation amplitude representing the degree of overall height change of the plasma sphere. The average deviation amplitude is then multiplied by a uniform voltage response coefficient to construct a uniform voltage adjustment amount. This uniform voltage adjustment amount is synchronously assigned to the bias correction channels of all transparent electrodes, so that the electrode array coordinates to raise or lower the position of the plasma sphere in a consistent manner, thereby adjusting the overall spacing between the plasma sphere and the substrate. When the tilt drift mode is identified, the physical azimuth angle of each transparent electrode is obtained, and the angle difference between the physical azimuth angle and the identified main tilt direction angle of the plasma sphere is calculated. Then, a cosine function transformation is performed on the result to obtain the cosine value of the included angle. The cosine value of the included angle is used as the directional coupling weight, and then multiplied with the tilt amplitude obtained by fitting the deviation vector to form the final voltage adjustment amount of the electrode. This allows the electrode located in the tilt sinking direction to obtain a larger positive compensation voltage, while the electrode located in the floating direction obtains the opposite negative adjustment, thus constructing an asymmetric control field with directional torque to promote the tilt interface to return to the equilibrium state. If a local deformation mode is identified, the azimuth range of the deformation is deduced from the distribution position of the spectral deviation peak. The corresponding transparent electrode numbers within this azimuth range are extracted and identified. The temperature field deviation value is multiplied by the preset local response coefficient in the system to obtain the compensation voltage corresponding to the deformation intensity. This compensation voltage is applied only to the transparent electrodes falling within the deformation azimuth range, while the other electrodes maintain their existing static synthesis voltage or are slowly fine-tuned. Precise electric field correction is performed on the local abnormal region without disturbing the overall stable field, thereby achieving rapid correction and morphological regression of the plasma interface abrupt state.

[0029] In one example, a dynamically modulated voltage is applied to the transparent electrode by superimposing a periodic AC modulation component on the initial bias voltage based on a voltage adjustment amount, including: The initial bias voltage is superimposed with the voltage adjustment to obtain the static synthesized voltage. The modulation amplitude is determined based on the amplitude of the spectral intensity ratio deviation vector, and periodic AC modulation components are generated based on the preset modulation frequency range. When the overall vertical drift mode is identified, the phase difference of all transparent electrodes is set to zero. When the tilt drift mode is identified, the phase difference of each transparent electrode is calculated based on the difference between the azimuth angle of each transparent electrode and the tilt direction angle. When the local deformation mode is identified, the phase difference of the transparent electrodes within the deformation azimuth angle range is set to zero. The static synthesis voltage and the periodic AC modulation component are superimposed according to the phase difference corresponding to each transparent electrode to obtain the dynamic modulation voltage of each transparent electrode, which is then applied to the corresponding transparent electrode to make the plasma ball generate a breathing oscillation within a preset oscillation amplitude range in the vertical direction.

[0030] In this example, after identifying the current plasma interface state, the bias voltages of each transparent electrode set during the initialization phase are summed one by one with the voltage adjustment calculated in the previous control cycle to form the static composite voltage of each transparent electrode. The static composite voltage determines the basic electric field distribution applied to the electrode in the current state. The control system performs normalization calculations based on the amplitude of the spectral intensity ratio deviation vector at the current moment to quantify the overall deviation of the interface, and determines the modulation amplitude for this cycle based on the deviation degree, where a larger deviation results in a higher modulation amplitude. Simultaneously, a modulation frequency is selected from a preset modulation frequency range. If the deviation value is large and the control requirement is strong, high-frequency modulation is selected to accelerate the interface response rate; if the interface state is stable, low-frequency modulation is selected to maintain stability and control accuracy. After determining the modulation amplitude and modulation frequency, periodic AC modulation components are generated. The timing structure of the periodic AC modulation components is determined by the phase difference corresponding to each electrode. The phase difference setting strategy differs depending on the drift mode: When the overall vertical drift mode is identified, the phase difference of all transparent electrodes is uniformly set to zero to ensure synchronous changes in modulation voltage, thereby establishing a vertical driving electric field of the same phase within the entire plasma sphere and forming a uniform rising and falling breathing oscillation; when the tilt drift mode is identified, the angle difference between the azimuth angle of each electrode and the tilt direction angle is calculated, and different phase difference values ​​are set according to the angle difference value to form a driving field distribution with spatially gradual phase characteristics, thereby applying a spatially oriented correction torque to the plasma sphere under the action of the electric field to restore it to a horizontal equilibrium state; if the local deformation mode is identified, the deformation azimuth angle interval corresponding to the abnormal area is identified, and the phase difference of the electrodes in the abnormal area is uniformly set to zero, while other electrodes maintain the original modulation structure or amplitude reduction modulation to avoid applying unnecessary interference to non-abnormal areas. The static synthesized voltage of each transparent electrode is superimposed with its corresponding periodic AC modulation component in both the time and phase dimensions to form a dynamic modulation voltage signal. This dynamic modulation voltage signal is then applied to the drive power supply of each transparent electrode through an independent control channel, thereby constructing a controlled, asymmetric, and dynamically modulated composite electric field distribution in space within the transparent electrode array. When this composite electric field acts on the plasma sphere at the center of the cavity, it guides the interface to produce micro-amplitude periodic motion in the vertical direction, creating a breathing-like oscillation effect.

[0031] Before calculating the position deviation index of the plasma interface based on real-time state data, the process includes: performing a two-dimensional spatial discrete Fourier transform on the second temperature data to decompose the temperature field into low-frequency and high-frequency spatial components, where the low-frequency spatial components correspond to the overall temperature drift characteristics and the high-frequency spatial components correspond to the local hot spot distribution characteristics; extracting the top N frequency components with the largest amplitudes from the high-frequency spatial components, calculating the spatial position coordinates and amplitude evolution trends of each frequency component, and determining that the amplitude of a certain frequency component monotonically increases within M consecutive sampling periods and the growth rate exceeds the preset hot spot growth threshold, indicating a local overheating risk at the corresponding spatial location and predicting the temperature peak within the next T time steps; determining the adjacent transparent electrode number based on the spatial location corresponding to the local overheating risk, calculating the temperature margin between the predicted temperature peak and the target temperature threshold, and calculating the feedforward compensation voltage increment based on the temperature margin and the preset temperature-voltage response coefficient; and pre-adding the feedforward compensation voltage increment to the static synthesis voltage of the corresponding transparent electrode, while simultaneously increasing the modulation amplitude and modulation frequency of the transparent electrode to perform feedforward control of the local morphology of the plasma interface before local overheating occurs.

[0032] In one example, the plasma interface stabilization control method also includes: The target change rate is calculated based on the spectral intensity ratio, and the temperature standard deviation surge increment is calculated based on the temperature standard deviation. When the target change rate exceeds the preset change rate threshold or the temperature standard deviation surge increment exceeds the preset temperature surge threshold, it is determined to be an interface instability abnormal state. The amplitude and width of the forced correction voltage pulse are calculated based on the interface instability anomaly state, and the forced correction voltage pulse is synchronously applied to all transparent electrodes within a preset response time. Based on the abnormal state of interface instability, a power adjustment command is sent to the microwave source to reduce the microwave source power by a preset power reduction ratio, and a rotation frequency adjustment command is sent to the rotating magnetic field device to restore the plasma interface to a stable state.

[0033] In this example, the continuous trend of the spectral intensity ratio is monitored in real time in the plasma interface stability control system. Based on the target value of the interface state constructed from the CH to C2 spectral line ratio, the rate of change between two adjacent sampling periods is continuously calculated and converted into the target rate of change. Simultaneously, the standard deviation sequence of the temperature field is calculated, and the increase in temperature standard deviation is extracted. The sudden increase serves as an indicator of severe thermal inhomogeneity or local hot spot outbreaks. When the target rate of change exceeds the set rate of change threshold or the sudden increase in temperature standard deviation exceeds the temperature surge threshold, the control logic module immediately marks the current interface state as an "instability anomaly state." This state indicates that a sudden interface collapse, local overheating, or morphological abrupt change is occurring at the plasma-substrate interface. To quickly suppress such disturbances and prevent their propagation to crystal defects, a forced intervention process is initiated. The voltage pulse parameters to be applied are calculated based on the current anomaly intensity, and the pulse triggering time window is set in conjunction with the system's maximum safe response capability. Within the response window, all transparent electrodes will synchronously receive the forced correction voltage pulse to form a strong transient electric field gradient, forcing the plasma sphere to rapidly recover to the target region. Simultaneously, to prevent the microwave input power from further exacerbating reaction instability during abnormal periods, a power adjustment command is sent to the microwave source to reduce plasma energy density and alleviate the interface overheating trend. A frequency reduction command is sent to the rotating magnetic field control unit to temporarily lower its rotation frequency to near the initially set minimum value, thereby reducing the interference of macroscopic plasma flow disturbances on local interface recovery. Under multi-channel coordinated intervention, a high-energy electric field reconstruction and energy input reduction are synchronously linked within milliseconds, forming a composite recovery mode of "electric field pulse suppression + energy reduction and cooling + magnetic field disturbance suppression." This effectively ensures that the plasma interface can return to the stable range in a very short time when faced with sudden disturbances, preventing nonlinear runaway evolution during crystal deposition.

[0034] In one example, based on the abnormal state of interface instability, a power adjustment command is sent to the microwave source to reduce the microwave source power by a preset power reduction ratio, and a rotation frequency adjustment command is sent to the rotating magnetic field device to restore the plasma interface to a stable state, including: The severity index of the anomaly is calculated based on the target rate of change and the sudden increment of the temperature standard deviation. The power reduction ratio of the microwave source and the rotation frequency adjustment value of the rotating magnetic field device are determined according to the severity index of the anomaly, and the power adjustment command and the rotation frequency adjustment command are generated. Within a preset response time, a power adjustment command is simultaneously sent to the microwave source and a rotation frequency adjustment command is sent to the rotating magnetic field device. Periodic disturbance data corresponding to each direction angle within a single rotation cycle of the rotating magnetic field are recorded. Based on the periodic perturbation data, the phase compensation and amplitude compensation of the transparent electrode corresponding to each angle are calculated. When the spectral intensity ratio deviation vector and the temperature field deviation value both fall back to the preset stable threshold range, it is determined that the plasma interface has recovered to a stable state.

[0035] In this example, the severity of the anomaly is quantitatively assessed. After real-time detection of the target rate of change in the CH / C2 spectral intensity ratio and the sudden increase in the standard deviation of the substrate temperature, these two variables are combined according to set weights to form an anomaly severity index, reflecting the intensity of the nonlinear dynamic change at the plasma-substrate interface and the degree of thermo-chemical coupling disturbance. When the anomaly severity index reaches a medium-to-high level threshold, the microwave source power should be automatically reduced by a certain percentage, and the rotational frequency of the rotating magnetic field device should be reduced by a certain amount, generating corresponding power adjustment and rotational frequency adjustment commands. Within a preset response time, a power adjustment command is simultaneously sent to the microwave source and a rotational frequency adjustment command is sent to the rotating magnetic field device. Reducing the microwave source power slows the continued rise in plasma active free radical density, while reducing the rotating magnetic field frequency weakens the impact of large-scale magnetofluid disturbances on the interface geometric stability. After the power and magnetic field parameters are reduced, the disturbance monitoring phase begins. After the rotating magnetic field completes one full rotation cycle, the disturbance response data of the plasma interface at various azimuth angles during that cycle are recorded, mainly including key quantities such as the trend of spectral ratio deviation change, temperature gradient fluctuation curve, and interface geometric center offset trajectory. Based on periodic perturbation data, using spatial matching algorithms and frequency domain modulation functions, the phase compensation and amplitude compensation amounts of each transparent electrode at the corresponding azimuth angle are deduced. This allows the electrode array to implement directional feedforward compensation in the next round of dynamic modulation, that is, to actively adjust the modulation parameters of the corresponding electrodes to construct a locally stable field before the rotating magnetic field causes disturbances, thereby counteracting the periodic perturbations caused by the rotation of the magnetofluid to the interface. After the modulation system performs feedforward compensation, the downward trend of the spectral ratio deviation vector and the standard deviation of the temperature field is continuously monitored. If both decrease steadily and remain within the preset stable threshold range for multiple consecutive sampling periods, the control system automatically determines that the plasma interface has recovered from the unstable abnormal state to the dynamic stable operating range and marks the state as the stable closed-loop completion node.

[0036] This embodiment provides a plasma interface stabilization control device, applied to a microwave plasma chemical vapor deposition (PVDC) apparatus, characterized by comprising: A reaction chamber, the reaction chamber comprising a quartz cylinder and a shielding cavity disposed outside the quartz cylinder; Multiple transparent electrodes are distributed along the axial direction of the quartz cylinder. The transparent electrodes are disposed between the quartz cylinder and the shielding cavity, and each transparent electrode is electrically insulated from the others. The multiple transparent electrodes are arranged at equal or non-equal intervals along the axial direction of the quartz cylinder to form an electric field gradient distribution that varies along the height direction of the reaction cavity. A modulation power supply module is electrically connected to the plurality of transparent electrodes respectively, and is used to apply a periodic modulation voltage with a spatial phase difference to each transparent electrode; The plurality of transparent electrodes form a spatially distributed modulated electric field during operation, causing controlled periodic oscillations at the plasma interface within the reaction chamber.

[0037] The reaction chamber is used to contain the plasma and the substrate; Figure 2 This diagram illustrates the distribution of the transparent electrode array. The transparent electrode array is located between the quartz cylinder and the shielding cavity, distributed axially, with each electrode electrically insulated from the others. A modulation power module applies a periodic modulation voltage with a spatial phase difference to each transparent electrode in the array via an electrical connection. Specifically, 1 represents the shielding cavity, which is cylindrical and forms the outermost structure of the device; 2 represents the quartz cylinder, also cylindrical, located inside the shielding cavity and concentrically positioned with it; 3 represents the transparent electrodes, each an independent rectangular electrode sheet positioned in the annular gap between the outer wall of the quartz cylinder and the inner wall of the shielding cavity. Multiple electrodes are evenly spaced axially (vertically) to form an electrode array, each independent and electrically insulated from the others; 4 represents the substrate, located at the bottom inside the quartz cylinder, used to support the single-crystal diamond to be deposited. Each transparent electrode can be independently subjected to a periodic modulation voltage with a spatial phase difference via the modulation power module, thereby creating an axially varying spatially distributed modulation electric field within the reaction cavity, achieving precise electric field control at different heights of the plasma interface.

[0038] In this embodiment, the transparent electrode is made of a conductive transparent material, which has a preset transmittance in the microwave operating band to avoid interference with plasma optical monitoring and microwave energy coupling.

[0039] In this embodiment, a plasma state detection module and a control module are also included. The plasma state detection module is used to acquire plasma state detection signals, and the control module adjusts the amplitude, frequency, and phase parameters of the periodic modulation voltage output by the modulation power supply module according to the plasma state detection signals.

[0040] In this embodiment, the specific implementation of each unit in the above device embodiment is described in the above method embodiment, and will not be repeated here.

[0041] 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, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for stabilizing and controlling a plasma interface, characterized in that, include: Multiple independent transparent electrodes are arranged axially between the quartz cylinder of the reaction chamber and the shielding chamber; Periodic modulation voltages with spatially different distributions are applied to multiple transparent electrodes, causing the transparent electrodes to form a modulation electric field with a spatial phase difference within the reaction chamber. Under the action of the modulated electric field, the plasma interface in the reaction chamber generates controlled periodic oscillations, thereby maintaining a stable spatial relationship between the plasma interface and the substrate.

2. The plasma interface stabilization control method according to claim 1, characterized in that, The amplitude of the periodic oscillation is controlled within a preset amplitude range and the oscillation frequency is controlled within a preset frequency range to avoid local collapse, tilting or positional drift and locking of the plasma interface.

3. The plasma interface stabilization control method according to claim 2, characterized in that, The parameters of the periodic modulation voltage are adjusted in a closed loop according to the plasma state detection signal, which includes at least one of the following: plasma optical emission spectrum signal, temperature distribution signal in the reaction chamber, spatial position signal or morphology signal of plasma interface.

4. The plasma interface stabilization control method according to claim 3, characterized in that, Based on the plasma state detection signal, the plasma interface is identified as being in an overall vertical drift mode, a tilt drift mode, or a local deformation mode, and the amplitude and phase distribution of the periodic modulation voltage of the multiple transparent electrodes are adjusted for different modes.

5. The plasma interface stabilization control method according to claim 4, characterized in that, Adjusting the amplitude and phase distribution of the periodic modulation voltages of the multiple transparent electrodes for different modes includes: When the overall vertical drift mode is identified, the periodic modulation voltages of all transparent electrodes are set to be in phase and have the same amplitude, so that the plasma interface will generate periodic oscillations along the vertical direction. When the tilt drift mode is identified, the phase difference of the periodic modulation voltage of each transparent electrode is set to a spatial gradient distribution according to the tilt direction, so that the tilt state of the plasma interface is corrected. When a local deformation mode is identified, the periodic modulation voltage amplitude of the transparent electrode corresponding to the deformation region is increased to restore the plasma interface of the local deformation region to the target shape.

6. The plasma interface stabilization control method according to claim 5, characterized in that, The periodic modulation voltage is an alternating voltage, and there is an adjustable phase difference between the modulation voltages of adjacent transparent electrodes to form a spatially varying alternating electric field within the reaction chamber.

7. The plasma interface stabilization control method according to claim 6, characterized in that, The controlled periodic oscillations homogenize the plasma energy distribution in both the time and spatial domains, thereby suppressing the accumulation of localized overheating and step defects on the substrate surface.

8. A plasma interface stabilization control device, applied to a microwave plasma chemical vapor deposition (PVDC) system, characterized in that, include: A reaction chamber, the reaction chamber comprising a quartz cylinder and a shielding cavity disposed outside the quartz cylinder; Multiple transparent electrodes are distributed along the axial direction of the quartz cylinder. The transparent electrodes are disposed between the quartz cylinder and the shielding cavity, and each transparent electrode is electrically insulated from the others. The multiple transparent electrodes are arranged at equal or non-equal intervals along the axial direction of the quartz cylinder to form an electric field gradient distribution that varies along the height direction of the reaction cavity. A modulation power supply module is electrically connected to the plurality of transparent electrodes respectively, and is used to apply a periodic modulation voltage with a spatial phase difference to each transparent electrode; The plurality of transparent electrodes form a spatially distributed modulated electric field during operation, causing controlled periodic oscillations at the plasma interface within the reaction chamber.

9. The plasma interface stabilization control device according to claim 8, characterized in that, The transparent electrode is made of a conductive transparent material, which has a preset transmittance in the microwave operating band to avoid interference with plasma optical monitoring and microwave energy coupling.

10. The plasma interface stabilization control device according to claim 8, characterized in that, It also includes a plasma state detection module and a control module. The plasma state detection module is used to collect plasma state detection signals, and the control module adjusts the amplitude, frequency, and phase parameters of the periodic modulation voltage output by the modulation power supply module according to the plasma state detection signals.

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