A method and device for controlling seamless switching of a crystal oscillator in a coating process

Abstract

The application discloses a crystal oscillator seamless switching control method and device in a coating process, and relates to the field of vacuum evaporation; the method comprises the following steps: continuously acquiring a frequency value of a first crystal oscillator, constructing a frequency decay function, and calculating an available remaining time for reducing a lowest available frequency threshold; switching is triggered when the available remaining time is less than a safety life threshold; whether the first crystal oscillator meets an effectiveness criterion is confirmed in a switching transition stage; if yes, a real-time coating rate signal of the first crystal oscillator is taken as a PID controller feedback input quantity; if not, an estimated coating rate output by a feedback quantity estimation model is taken as the feedback input quantity, the model is a discretization transfer function for mapping an evaporation source power into the estimated coating rate, parameters of the model are calibrated with a first crystal oscillator real-time coating rate as a true value, and a recursive least square method with a forgetting factor is used for online calibration; after successful switching, a cumulative thickness value of the first crystal oscillator and a PID integral term value are written into a second crystal oscillator control channel; and the feedback input is gradually switched to a second crystal oscillator real-time coating rate.

Description

Technical Field

[0001] This invention relates to the field of vacuum evaporation technology, and more specifically to a method and apparatus for seamless switching control of crystal oscillators in the coating process. Background Technology

[0002] In vacuum evaporation processes, monitoring the film thickness using a quartz crystal is crucial for controlling the deposition thickness. The crystal is mounted within the evaporation source's field of view. As the film is deposited, the equivalent mass of the crystal increases, and the resonant frequency continuously decreases. The controller calculates the film thickness and deposition rate based on this frequency change. However, the thicker the film deposited on the crystal surface, the greater the frequency drop. When the frequency falls below the minimum usable frequency threshold, the crystal reading becomes unreliable. At this point, the crystal must be replaced or switched to a backup crystal for continued operation; this process is called crystal switching.

[0003] In existing switching schemes, the switching trigger condition is usually that the crystal oscillator frequency reaches a fixed threshold, meaning the switching is only performed when the crystal oscillator is considered to have failed. For a period after the switching is triggered, the system completely abandons feedback control based on the rate signal, maintaining only the power value before the switching in open-loop operation, until feedback is restored after the backup crystal oscillator stabilizes. This approach has several problems.

[0004] First, the crystal oscillator data is no longer reliable when the switch occurs. After the frequency reaches the threshold, the frequency, plating rate, and thickness data output by the crystal oscillator have deviated significantly from the true values, and the last segment of process data before the switch has basically lost its reference value.

[0005] Secondly, there is a control blind spot during the transition period after switching. During the open-loop maintenance period, although the power remains constant, the evaporation source itself is subject to various disturbances such as thermal drift, drop in film liquid level, and crucible temperature fluctuations, inevitably causing the actual evaporation rate to deviate from the target value. The applicant conducted a simulation test on this type of scheme on a ZZS-800 electron gun evaporation equipment: the frequency dropped to the threshold and then switched immediately, maintaining open-loop operation with power after switching, and resuming feedback only after the standby crystal oscillator started oscillating. The results showed that the root mean square fluctuation of the coating rate during the transition period of this scheme was approximately 14.5% of the target value, and the more switching times, the more significant the cumulative thickness error—after 3 switching times, the cumulative film thickness deviation could reach 8% to 15% of the target thickness.

[0006] Third, there is no control state inheritance after the switch. After the new crystal oscillator takes over, the cumulative thickness is re-accumulated from zero, and the PID controller also needs to rebuild historical control information, resulting in data breakpoints before and after the switch.

[0007] Overall, these solutions share the common characteristic of treating crystal oscillator switching as an isolated event—if the crystal oscillator fails, it is replaced; during the switching process, an open-loop system is used temporarily; and after the switch is complete, the process restarts. Each link is isolated, failing to form a continuous control chain. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes a method and apparatus for seamless switching control of crystal oscillators in the coating process.

[0009] The main contents of this invention include:

[0010] A method for seamless switching control of crystal oscillators in a coating process includes the following steps: Continuously acquire the frequency values ​​of the first crystal oscillator at multiple sampling times during the current operation, and denote them as the first frequency sequence. ; According to the first frequency sequence and the preset minimum available frequency threshold Calculate the remaining available time for the first crystal oscillator; When the remaining usable time of the first crystal oscillator is less than a preset safe lifespan threshold When the switching process from the first crystal oscillator to the second crystal oscillator is triggered, the switching process from the first crystal oscillator to the second crystal oscillator includes a switching transition phase and a switching success phase. During the switching transition phase, it is determined whether the current frequency of the first crystal oscillator meets the preset validity criteria. If it does, the real-time plating rate signal of the first crystal oscillator continues to be used as the feedback input of the PID controller. If it does not meet the criteria, the estimated plating rate output by a feedback estimation model is used as the feedback input of the PID controller. During the successful switching phase, the second crystal oscillator is used as the current working crystal oscillator. The accumulated thickness of the first crystal oscillator and the current value of the integral term of the PID controller are written as initial values ​​into the control channel corresponding to the second crystal oscillator to continue the coating process.

[0011] Preferably, according to the first frequency sequence and the preset minimum available frequency threshold Calculate the remaining available time of the first crystal oscillator, including: According to the first frequency sequence Construct the frequency decay function of the first crystal oscillator: ; in, Indicates the current moment. Indicates the sampling time. This represents the rate of change of frequency at the current moment. This represents the acceleration due to the change in frequency at the current moment. ; Based on the frequency decay function of the first crystal oscillator and the preset minimum usable frequency threshold ,make Solve the frequency decay function to find the frequency of the first crystal oscillator decreasing to Required remaining time ,Will This is the remaining available time for the first crystal oscillator.

[0012] Preferably, when the absolute value of the frequency change acceleration is lower than a preset threshold, the frequency decay function degenerates into a linear function: The remaining available time of the first crystal oscillator is .

[0013] Preferably, the preset validity criterion includes: the current frequency of the first crystal oscillator is higher than the minimum usable frequency threshold. And / or the frequency signal noise of the first crystal oscillator is lower than a preset noise degradation threshold.

[0014] Preferably, during the switching transition phase, when the current frequency of the first crystal oscillator meets a preset validity criterion: The real-time plating rate signal of the first crystal oscillator is used as the feedback input of the PID controller to activate the oscillation circuit of the second crystal oscillator and monitor its frequency stability. Before the frequency of the second crystal oscillator stabilizes, the second crystal oscillator does not output power regulation to the evaporation source power supply.

[0015] Preferably, after the frequency of the second crystal oscillator stabilizes, the switching success stage begins, and the specific steps include: The cumulative parameters in the control channel corresponding to the first crystal oscillator are written into the control channel corresponding to the second crystal oscillator. The cumulative parameters include the current cumulative thickness value of the first crystal oscillator, the current value of the integral term of the PID controller corresponding to the first crystal oscillator, and the current plating rate value of the first crystal oscillator. Switching the feedback input of the PID controller from the real-time plating rate signal of the first crystal oscillator to the real-time plating rate signal of the second crystal oscillator is expressed as: ; in, This is the real-time plating rate signal of the second crystal oscillator. This is the real-time plating rate signal of the first crystal oscillator. It is a weighting coefficient that linearly increases from 0 to 1 within a preset transition time, starting from the moment when the second crystal oscillator frequency stabilizes.

[0016] Preferably, when the current frequency of the first crystal oscillator does not meet the preset validity criterion, during the switching transition phase: Stop using the real-time plating rate signal of the first crystal oscillator as the feedback input of the PID controller; The estimated coating rate, output in real time by the thermodynamic model of the evaporation source, is used as the feedback input of the PID controller. The oscillation circuit of the second crystal oscillator is activated, and the frequency stability of the second crystal oscillator is continuously monitored. Before the frequency of the second crystal oscillator is stable, the second crystal oscillator does not output power regulation to the evaporation source power supply. The thermodynamic model of the evaporation source is a discretized transfer function that maps the real-time value of the evaporation source power to an estimated coating rate. ; in, The estimated plating rate at the k-th sampling time is... Let be the evaporation source power at the k-th sampling time. , , , The discretized parameters are determined through online calibration. The online calibration uses the measured coating rate of the first crystal oscillator during the normal coating stage as the calibration true value and is performed using a recursive least squares method with a forgetting factor. The forgetting factor ranges from 0.95 to 0.99.

[0017] Preferably, after the frequency of the second crystal oscillator stabilizes, the switching success stage begins, and the specific steps include: The cumulative parameters in the control channel corresponding to the first crystal oscillator are written into the control channel corresponding to the second crystal oscillator. The cumulative parameters include the current cumulative thickness value of the first crystal oscillator and the current value of the integral term of the PID controller corresponding to the first crystal oscillator. The feedback input of the PID controller is switched from the estimated plating rate output by the evaporation source thermodynamic model to the real-time plating rate signal of the second crystal oscillator, as follows: ; in, This is the real-time plating rate signal of the second crystal oscillator. The estimated coating rate is output by the thermodynamic model of the evaporation source. It is a weighting coefficient that linearly increases from 0 to 1 within a preset transition time, starting from the moment when the second crystal oscillator frequency stabilizes.

[0018] Preferably, the weighting coefficient Generate in the following way: Taking the moment when the second crystal oscillator frequency stabilizes as the zero point of timing, the transition time is recorded as... , To determine the cumulative duration after stabilization, then: ; The range of values ​​is It increases linearly and monotonically with time and is used for weighted fusion of two plating rate signals.

[0019] Preferably, in the successful switching stage, the tooling parameters corresponding to the second crystal oscillator are loaded into the control channel corresponding to the second crystal oscillator, replacing the tooling parameters corresponding to the first crystal oscillator.

[0020] Preferably, the remaining usable time of the first crystal oscillator is not less than a preset safe lifespan threshold. During this period, the frequency signal of the first crystal oscillator was continuously monitored; When an abnormality is detected in the frequency signal of the first crystal oscillator, the vacuum degree signal and / or the evaporation source power feedback signal are collected synchronously, and the frequency signal is cross-correlation analysis is performed with the vacuum degree signal and / or the evaporation source power feedback signal. If the vacuum signal and the frequency signal change abruptly in sync, it is determined to be a film material splashing or boiling over, and the operation of closing the shield and waiting for recovery is executed without triggering crystal oscillator switching; If the frequency signal changes abruptly while the vacuum level signal remains unchanged, it is determined that the crystal oscillator is loose or has poor contact, triggering a switch from the first crystal oscillator to the second crystal oscillator.

[0021] This invention also proposes a crystal oscillator switching control device in the coating process, comprising: The acquisition module is used to continuously acquire the frequency values ​​of the first crystal oscillator in the current operation at multiple sampling times; The prediction module is used to construct a frequency decay function of the first crystal oscillator based on the frequency value, and to calculate the remaining available time of the first crystal oscillator based on the frequency decay function and a preset minimum available frequency threshold. The determination module is used to trigger a switching process from the first crystal oscillator to the second crystal oscillator when the available remaining time is less than a preset safe lifespan threshold; and is used to perform an anomaly determination and selectively trigger a switching when an anomaly is detected in the frequency signal of the first crystal oscillator during the period when the available remaining time is not less than the safe lifespan threshold. The feedback management module is used to select, based on whether the current frequency of the first crystal oscillator meets the preset validity criteria, the real-time plating rate signal of the first crystal oscillator or the estimated plating rate output by a feedback estimation model as the feedback input of the PID controller during the switching transition phase of the switching process. The state transition module is used to write the current cumulative thickness value of the first crystal oscillator and the current value of the integral term of the PID controller into the control channel corresponding to the second crystal oscillator during the successful switching phase of the switching process. The control module is used to continue the coating process based on the real-time signal of the second crystal oscillator and the written parameters.

[0022] It is worth noting that, compared to existing solutions that only trigger switching after the crystal oscillator has failed or reached a fixed frequency threshold, and which abandon rate feedback control and operate in open loop only to maintain power after switching, this invention predicts the remaining lifespan of the currently operating crystal oscillator in advance by analyzing the frequency decay trajectory before the crystal oscillator fails, and actively initiates switching while the crystal oscillator is still working normally; during the switching transition, the feedback signal of the crystal oscillator is used to continue using the current state of the crystal oscillator or the model estimation value is enabled to ensure that the closed-loop control is not interrupted; after the switching is completed, the control state of the previous crystal oscillator is completely inherited to the subsequent crystal oscillator, so that no control blind spots, data breakpoints, or accumulated switching errors are generated during the crystal oscillator switching transition. Attached Figure Description

[0023] Figure 1 This is a block diagram of the functional modules of the crystal oscillator switching control system. Figure 2 Flowchart for frequency attenuation prediction and handover triggering; Figure 3 Timing diagram of the switching process for the first crystal oscillator to meet the validity criterion; Figure 4 Timing diagram of the switching process when the first crystal oscillator does not meet the validity criterion; Figure 5 This is a weighted mixed transition timing diagram; Figure 6 A comparison curve of plating rate fluctuations during the transition period; Figure 7 This is a comparison chart of cumulative film thickness errors after multiple switching operations. Detailed Implementation

[0024] The technical solution protected by this invention will be described in detail below with reference to the accompanying drawings.

[0025] This invention proposes a seamless crystal oscillator switching control method and device in the coating process, which can achieve no control blind spots, no data breakpoints, and no accumulation of switching errors during the crystal oscillator switching transition. This invention determines whether the frequency of the currently operating crystal oscillator meets the validity criteria through frequency attenuation prediction. Based on the monitoring data of the currently operating crystal oscillator, different switching strategies are executed. After a successful switch, the new crystal oscillator inherits the accumulated thickness and PID integral term, and simultaneously, based on a weighted mixing formula, the feedback source is smoothly transitioned to the second crystal oscillator.

[0026] like Figure 1 As shown, the control system of the present invention includes an acquisition unit, a prediction unit, a decision unit, a feedback management unit, a state transition unit, and a power execution unit. Each module works together to complete the crystal oscillator switching control.

[0027] The applicant used a ZZS-800 electron gun vacuum evaporation machine equipped with an EGN-406M electron gun as the test platform, with Al2O3 as the film material, a target deposition rate of 3.0 Å / s, and a background vacuum level of [missing information]. Working vacuum The target film thickness is 1200 Å, the substrate temperature is 150℃, and the plating pot rotation speed is 60 rpm.

[0028] The crystal oscillator controller uses a CRTM-R1 type crystal film-forming controller, and the crystal oscillator is a 5MHz AT-cut quartz crystal oscillator with a minimum usable frequency threshold. =4.8MHz. In one possible implementation, the lowest available frequency threshold. The settings follow these principles: For a 5MHz AT-cut quartz crystal oscillator, the minimum usable frequency threshold... The minimum usable frequency threshold is set to 94%–97% of the fundamental frequency (i.e., 4.85–4.7 MHz). For crystal oscillators with different fundamental frequencies or different cuts, those skilled in the art can, based on the linear region range of the Sauerbrey equation (frequency deviation not exceeding 2%–4% of the fundamental frequency) and in conjunction with the specific equipment model and process precision requirements, set the minimum usable frequency threshold within a safe range. .

[0029] Dual sensor configuration: Crystal oscillator A is installed 5° to the left and 25cm above the evaporation source; crystal oscillator B is installed 10° to the right and 28cm above the evaporation source. The industrial control computer has a sampling period of 100ms, simultaneously recording full data on frequency, plating rate, evaporation source power, and vacuum level. Crystal oscillator A serves as the primary active crystal oscillator, while crystal oscillator B serves as the backup secondary crystal oscillator.

[0030] Before the process begins, a short-term dual-crystal synchronous calibration is performed: stabilizing the deposition rate at a low rate of 0.3 Å / s for 30 seconds, while simultaneously reading the deposition rate from both crystal oscillators, and measuring... =0.32Å / s =0.28Å / s, calculate the sensitivity difference ratio =1.14. Simultaneously, an offline step response test was performed—a 5% power step was applied (i.e., 5.5kW → 5.78kW), and the plating rate response curve was recorded. The initial parameters of the feedback quantity estimation model were obtained by fitting the curve. =1.724、 =-0.741、 =0.032、 =-0.015.

[0031] During a single coating process, the frequency values ​​of the first crystal oscillator at multiple sampling times are continuously acquired and denoted as the first frequency sequence. In this embodiment, the frequency value of the first crystal oscillator is continuously acquired with a sampling period of 100ms, and the frequency change rate is calculated every 100ms from the frequency values ​​at adjacent sampling times using a first-order difference. Then, the frequency change acceleration is calculated from the frequency change rate at adjacent sampling times using the first-order difference. At the current moment frequency value Rate of change of frequency and frequency change acceleration Constructing a second-order approximation function: ; Next, order Solve + + =0, take the positive real root as the available remaining time. ,when When the second-order approximation function degenerates into a linear function, The remaining available time of the first crystal oscillator is A preset threshold for the frequency change acceleration is used to determine whether the second-order term is significantly higher than the measurement noise. The contribution of the second-order term to the frequency prediction within a single sampling period is less than three times the standard deviation of the frequency measurement noise (i.e., satisfying the 3σ criterion). In this case, the influence of the second-order term is not significant compared to the measurement noise, and a linear approximation is sufficient to meet the prediction accuracy. One possible implementation is to set the preset threshold to 6. ,in, The short-time noise standard deviation of the frequency signal. This is the sampling interval. Those skilled in the art can also adjust this threshold according to the actual signal quality.

[0032] The complete execution logic based on the above frequency attenuation prediction, effectiveness determination, dual-path switching, and fault cross-diagnosis is summarized into a control flowchart, see below for details. Figure 2 The diagram shows the main lines of normal sampling, remaining lifetime calculation, switching trigger, two-way feedback shunting, backup crystal oscillator readiness, parameter migration, and smooth transition, with S1 to S9 connected in series. An additional abnormal monitoring branch is added to identify frequency jumps in real time when the crystal oscillator has sufficient remaining lifetime, distinguish between film material splashing process disturbances and crystal oscillator hardware failures, and execute differentiated handling logic.

[0033] This invention calculates the remaining usable time of the currently operating crystal oscillator based on extrapolation. When the remaining usable time of the first crystal oscillator is less than a preset safe lifespan threshold... When the switching process from the first crystal oscillator to the second crystal oscillator is triggered, the switching process from the first crystal oscillator to the second crystal oscillator includes a switching transition phase and a switching success phase; in the switching transition phase, two paths are executed respectively according to whether the current frequency of the first crystal oscillator meets the validity criterion.

[0034] Specifically, if the current frequency of the first crystal oscillator meets the preset validity criterion, then path one is executed, that is, the first crystal oscillator continues to be used for feedback, while the second crystal oscillator is started to prepare for takeover. After the second crystal oscillator enters a stable state, it smoothly takes over all parameters of the first crystal oscillator and smoothly transitions the feedback source to the second crystal oscillator based on the weighted mixing formula, and continues the coating process.

[0035] If the current frequency of the first crystal oscillator does not meet the preset validity criterion, then path two is executed. At this time, the first crystal oscillator has approached or entered the unreliable frequency range when it is switched to trigger. This path replaces the measured value of the crystal oscillator with the model estimate value to ensure that the PID controller can still obtain feedback input and maintain closed-loop regulation of the evaporation source power during the transition period. After the second crystal oscillator stabilizes, it inherits the corresponding cumulative data of the first crystal oscillator and smoothly transitions the feedback source to the second crystal oscillator based on the weighted mixing formula.

[0036] More specifically, the preset validity criteria include: the current frequency of the first crystal oscillator is higher than the minimum usable frequency threshold. And / or the frequency signal noise of the first crystal oscillator is lower than a preset noise degradation threshold.

[0037] Example 1 This embodiment will describe in detail the specific steps of path one execution.

[0038] The frequency sequence of crystal oscillator A is acquired in real time, and its frequency change rate and frequency change acceleration are calculated. Based on these calculations, a frequency decay function is constructed, and its remaining usable time is obtained. When the remaining available time of the first crystal oscillator Less than the preset safe lifespan threshold When the time comes, initiate the switch.

[0039] In this embodiment, the remaining available time of the first crystal oscillator is calculated. The preset safe lifespan threshold is 21 seconds. The time is 30 seconds, at which point the current frequency of the first crystal oscillator meets the preset validity criterion; safe lifespan threshold. The time should be set based on the complete switchover time of the specific equipment. The complete switchover time includes the switchover transition phase (standby crystal oscillator startup and frequency stabilization confirmation) and the successful switchover phase (weighted mixed smooth transition). In one possible implementation, ,in The maximum handover time for a specific device configuration, where K is a safety factor (typically 3~10). In this embodiment, the ZZS-800 device... ≈4.3s, taking K≈7, therefore the safe lifespan threshold is... =30s.

[0040] The system continuously collects the frequency value of the first crystal oscillator with a sampling period of 100ms. Table 1 records the measured data of the attenuation of the crystal oscillator frequency with film deposition during the complete 294s evaporation cycle.

[0041] As shown in Table 1, the frequency decreases approximately linearly within the 0–180 s time period, and the rate of change of frequency r(t) remains stable at approximately [value missing]. 640Hz / s, frequency change acceleration Approaching zero; after 180s, the continuous thickening of the film layer leads to increased crystal oscillator load, and the decay curve exhibits obvious nonlinear characteristics, with the absolute value of acceleration gradually increasing from... Increased to 5Hz / s² 103Hz / s², with a noise standard deviation The increase from 1.0Hz to 4.3Hz indicates that the quality of the crystal oscillator signal continuously deteriorates as the film thickness increases.

[0042] Table 1 Measured data of crystal oscillator frequency decay trajectory

[0043] Switching triggered by =270s, at this time =4.816MHz, frequency change rate = 654Hz / s, frequency change acceleration = 10Hz / s², minimum usable frequency threshold =4.8MHz. Substituting the above parameters into the second-order frequency attenuation equation: Solve the quadratic equation in one variable and take positive real roots. The solution is: ≈21 seconds, compared to the preset safe lifespan threshold =3 seconds, < Trigger switch, when triggered =4.816MHz> =4.8MHz, the first crystal oscillator is still in the normal operating range.

[0044] During the switching transition phase, and before the second crystal oscillator stabilizes, the following steps are performed: The real-time plating rate signal of the first crystal oscillator is used as the feedback input of the PID controller to maintain closed-loop regulation of the evaporation source power. The current plating rate value of the first crystal oscillator is preset as the initial target plating rate of the second crystal oscillator; The oscillation circuit of the second crystal oscillator is activated and its frequency stability is monitored. For example, if the output frequency of the second crystal oscillator is continuously monitored, and the frequency fluctuation of 10 consecutive samples is less than the preset tolerance ±50Hz, it is determined that the frequency of the second crystal oscillator has stabilized. Before the frequency of the second crystal oscillator stabilizes, the second crystal oscillator does not output power regulation to the evaporation source power supply. In this embodiment, the frequency of crystal oscillator B stabilizes after about 1.5 seconds, and after another 0.8 seconds of validity confirmation, crystal oscillator B is ready after a total of about 2.3 seconds.

[0045] After the frequency of the second crystal oscillator stabilizes, the following parameters are written from the control channel corresponding to the first crystal oscillator into the control channel corresponding to the second crystal oscillator, specifically including: (1) The current cumulative thickness value of the first crystal oscillator is used as the initial base for the cumulative thickness of the second crystal oscillator. The second crystal oscillator is only used to measure the thickness added after the switch. The total thickness is the sum of the initial base and the added thickness. (2) The current value of the integral term of the PID controller corresponding to the first crystal oscillator is used as the initial value of the integral term of the PID controller corresponding to the second crystal oscillator; (3) The current plating rate value of the first crystal oscillator is used as the initial target plating rate of the second crystal oscillator. The second crystal oscillator performs closed-loop control starting from the initial target plating rate and gradually converges to the preset process target plating rate during the weighted mixing transition.

[0046] Before writing the current value of the integral term into the control channel corresponding to the second crystal oscillator, it first checks whether the current value of the integral term is already at the preset upper or lower limit of integral saturation. If it is at the upper limit of integral saturation, the upper limit of integral saturation is multiplied by a discount factor of 0.65 and used as the value to be written; if it is at the lower limit of integral saturation, the lower limit of integral saturation is multiplied by a discount factor of 0.65 and used as the value to be written.

[0047] In step (3) above, the current plating rate value of the first crystal oscillator is used as the initial target plating rate of the second crystal oscillator. The purpose is that before the weighted mixing officially starts, the control channel of the second crystal oscillator has obtained an initial target value close to the current process state, so that when the weighted mixing starts, the error term of the control loop of the second crystal oscillator (the difference between the initial target plating rate and the measured plating rate of the second crystal oscillator) is at a low level, thereby further reducing the instantaneous plating rate deviation at the beginning of the mixing. This feature works synergistically with the subsequent weighted mixing transition formula—the initial target plating rate reduces the deviation amplitude at the starting point of the mixing, and the weighted mixing provides a smooth transition path. Together, they ensure that there is no power step jump during the switching process.

[0048] The feedback input of the PID controller is then switched from the real-time plating rate signal of the first crystal oscillator to the real-time plating rate signal of the second crystal oscillator, achieved through a weighted mixing method: ; in, This is the real-time plating rate signal of the second crystal oscillator. This is the real-time plating rate signal for the first crystal oscillator. It is a weighting coefficient that linearly increases from 0 to 1 within a preset transition time, starting from the moment when the second crystal oscillator frequency stabilizes.

[0049] And the weighting coefficient The generation method is as follows: A timer is started when the second crystal oscillator frequency stabilizes, with a preset smooth transition time. =2 seconds is the threshold; when the timer value Δt < 2s =Δt / 2; when Δt≥2s =1.

[0050] During the 2-second smooth transition, the hybrid feedback value smoothly transitioned from 3.04 Å / s to 3.00 Å / s, and the PID output power smoothly decreased from 6.30 kW to 6.11 kW without any abrupt changes. For details on the changes in weighting coefficients, plating rates of the two paths, and hybrid feedback during the 2-second smooth transition phase, please refer to [link to details]. Figure 5 .

[0051] Figure 5 The graph is a weighted mixed transition time curve. The horizontal axis represents the transition time after the second crystal oscillator stabilizes. The black solid line represents the real-time plating rate of the first crystal oscillator, the black dashed line represents the real-time plating rate of the second crystal oscillator, the dotted line represents the linearly increasing weight σ(t), and the thick solid line represents the mixed feedback value. The weight increases linearly from 0 to 1 over time, the two plating rates are smoothly integrated, and the PID output power changes continuously and gently without step disturbances.

[0052] Load the Tooling parameter (Tooling_B=92.5%) corresponding to the second crystal oscillator into the control channel corresponding to the second crystal oscillator, replacing the Tooling parameter (Tooling_A=95.0%) corresponding to the first crystal oscillator.

[0053] Figure 3The timing diagram for the switching process when the first crystal oscillator meets the validity criterion is shown in Path 1. The diagram contains six curves from top to bottom: the first curve represents the resonant frequency of the first crystal oscillator, characterizing the attenuation trend of the crystal oscillator frequency with film deposition and the frequency position at the switching trigger; the second curve represents the oscillation status indication curve of the second crystal oscillator, characterizing the process of the standby crystal oscillator from activation to frequency stabilization (low level indicates inactivation or instability, high level indicates frequency stabilization); the third curve represents the PID controller feedback input source selection signal, indicating whether the current feedback signal comes from the measured value of the first crystal oscillator (high level) or the measured value of the second crystal oscillator (low level). In Path 1, the feedback source is the first crystal oscillator before successful switching, and switches to the second crystal oscillator after successful switching; the fourth curve represents the evaporation source output power curve, reflecting the continuous adjustment of the evaporation source power by the PID controller output; the fifth curve represents the real-time deposition rate curve, reflecting the dynamic change of the deposition rate; and the sixth curve represents the cumulative thickness curve, reflecting the cumulative increase in film thickness.

[0054] Figure 3 The time axis is marked with a broken axis (" / / ") at 270s, indicating that the time axis is broken at this point and the proportional relationship is changed—the left side (0~270s) normally displays the normal coating stage, while the right side (270~274.3s) is a magnified display of the switching transition and successful switching stages. Before 270s, all curves in the figure maintain continuous operation; after the switching is triggered at 270s, the frequency of the first crystal oscillator continues to decay; from 270s to 272.3s is the switching transition stage, the second crystal oscillator starts oscillating, and the PID feedback input remains the measured value of the first crystal oscillator, with power and coating rate remaining continuous; after the second crystal oscillator frequency stabilizes at 272.3s, the successful switching stage begins, executing a state inheritance and weighted mixed transition; from 272.3s to 274.3s is the weighted smooth transition stage, where the PID feedback input gradually switches from the measured value of the first crystal oscillator to the measured value of the second crystal oscillator; after 274.3s, the second crystal oscillator completely takes over, and the first crystal oscillator stops using its function. The evaporation power changes without abrupt changes throughout the entire process, the coating rate fluctuates very little, and the cumulative thickness curve is continuous without any breaks.

[0055] Example 2 This embodiment will describe in detail the specific steps of path two execution.

[0056] In a specific test, the current frequency of the first crystal oscillator was switched during triggering. =4.805MHz, slightly higher The frequency is 4.8MHz, but the frequency-to-noise ratio is 6.8, exceeding the noise degradation threshold of 5, thus failing to meet the validity criterion. Therefore, path two must be executed. The noise degradation threshold is used to determine whether the crystal oscillator frequency signal can still serve as a valid feedback input for the PID controller. When the frequency-to-noise ratio exceeds this threshold, the noise in the plating rate signal converted from the frequency signal has reached a level that the PID controller cannot effectively adjust—the sensitivity of the derivative element to noise will cause severe fluctuations in the PID output. In one possible implementation, the noise degradation threshold is set to 3-8, depending on the PID controller parameter tuning and process accuracy requirements. In this embodiment, a threshold of 5 is used.

[0057] When the remaining usable time of the first crystal oscillator is less than a preset safe lifespan threshold When the current frequency of the first crystal oscillator does not meet the preset validity criterion, that is, the current frequency of the first crystal oscillator is not higher than the minimum usable frequency threshold. If the frequency signal noise of the first crystal oscillator is not lower than the noise degradation threshold, and before the second crystal oscillator stabilizes during the switching transition phase, the following steps are performed: Stop using the real-time plating rate signal of the first crystal oscillator as the feedback input of the PID controller; The estimated coating rate, output in real time from the thermodynamic model of the evaporation source, is used as the feedback input of the PID controller to maintain closed-loop regulation of the evaporation source power. The oscillation circuit of the second crystal oscillator is activated, and the frequency stability of the second crystal oscillator is continuously monitored. Before the frequency of the second crystal oscillator is stable, the second crystal oscillator does not output power regulation to the evaporation source power supply. The thermodynamic model of the evaporation source is a discretized transfer function that maps the real-time value of the evaporation source power to an estimated coating rate. ; in, The estimated plating rate at the k-th sampling time is... Let be the evaporation source power at the k-th sampling time. , , , The discretized parameters determined through online calibration are used as the calibration true value based on the measured coating rate of the first crystal oscillator during the normal coating stage. The calibration is performed using a recursive least squares method with a forgetting factor, where the forgetting factor ranges from 0.95 to 0.99; in this embodiment, it is chosen to be 0.97. Before online calibration, the measured coating rate of the first crystal oscillator used as the calibration true value undergoes data preprocessing: periodic mechanical vibration disturbances are filtered out using a first-order low-pass filter with a cutoff frequency of 1-2 Hz; data sampling points whose difference from the median value in the sliding window exceeds three times the standard deviation of the sliding window are discarded.

[0058] After the frequency of the second crystal oscillator stabilizes, the following parameters are written into the control channel corresponding to the first crystal oscillator, specifically including: (1) The current cumulative thickness value of the first crystal oscillator — used as the initial base for the cumulative thickness of the second crystal oscillator; (2) The current value of the integral term of the PID controller corresponding to the first crystal oscillator is used as the initial value of the integral term of the PID controller corresponding to the second crystal oscillator; The current plating rate value of the first crystal oscillator is not written into the control channel corresponding to the second crystal oscillator.

[0059] The feedback input of the PID controller is switched from the estimated plating rate output by the feedback estimation model to the real-time plating rate signal from the second crystal oscillator: ; in, This is the real-time plating rate signal of the second crystal oscillator. The estimated coating rate is output by the thermodynamic model of the evaporation source. The weighting coefficients, which linearly increase from 0 to 1 within a preset transition time starting from the stable moment of the second crystal oscillator frequency, are also referred to in the smooth weighted transition curve of this path. Figure 5 The smooth weighted transition method of this path is the same as that of path one, the only difference being that the "old source" in the hybrid feedback is replaced by the measured value of the first crystal oscillator with the model estimate.

[0060] Figure 4 This is the timing diagram for the switching process when the first crystal oscillator does not meet the validity criterion (path two). The curves in the diagram have the same meaning as... Figure 3 Consistent: From top to bottom, the curves are: first crystal resonant frequency curve, second crystal oscillator start-up status indication curve, PID controller feedback input source selection signal, evaporation source output power curve, real-time plating rate curve, and cumulative thickness curve.

[0061] Figure 4 The timeline also uses a broken axis marker (" / / ") at 270s. The left side (0-270s) shows the normal coating stage, while the right side (after 270s) shows a magnified view of the switching transition and successful switching stages. Figure 3The difference lies in the following: In path two, the first crystal oscillator no longer meets the validity criterion when the switching is triggered. Therefore, after the switching is triggered at 270s, the real-time plating rate signal of the first crystal oscillator is immediately stopped as the PID feedback input. The PID feedback input source is switched to the estimated plating rate output by the thermodynamic model of the evaporation source during the switching transition phase (i.e., the virtual sensor takes over the feedback). From 270s to 272.3s is the switching transition phase. The frequency of the first crystal oscillator continues to decay, but its signal is no longer used for feedback control. The second crystal oscillator starts oscillating, and the power of the evaporation source is closed-loop regulated by the PID controller based on the model-estimated plating rate. After the frequency of the second crystal oscillator stabilizes at 272.3s, the switching success phase begins. The current cumulative thickness value and PID integral term value of the first crystal oscillator are written into the control channel of the second crystal oscillator (the current plating rate value of the first crystal oscillator is not written). Then, a weighted mixed transition is performed. From 272.3s to 274.3s is the weighted smooth transition phase. The PID feedback input is gradually switched from the model-estimated plating rate to the real-time plating rate signal of the second crystal oscillator. After 274.3s, the second crystal oscillator takes over completely, the model exits, and the first crystal oscillator stops being used. During the transition period, the power regulation is always in a closed-loop state, and there is no open-loop runaway range as in traditional solutions.

[0062] Example 3 This embodiment is a response strategy designed for unexpected and sudden abnormal situations.

[0063] The remaining usable time of the first crystal oscillator is not less than a preset safe lifespan threshold. During this period, the frequency signal of the first crystal oscillator was continuously monitored; When an abnormality is detected in the frequency signal of the first crystal oscillator, the vacuum degree signal and / or the evaporation source power feedback signal are collected synchronously, and the frequency signal is cross-correlation analysis is performed with the vacuum degree signal and / or the evaporation source power feedback signal. If the vacuum signal and the frequency signal change abruptly in sync, it is determined to be a film material splashing or boiling over, and the operation of closing the shield and waiting for recovery is executed without triggering crystal oscillator switching; If the frequency signal changes abruptly while the vacuum level signal remains unchanged, it is determined that the crystal oscillator is loose or has poor contact, triggering a switch from the first crystal oscillator to the second crystal oscillator.

[0064] In this embodiment, if the vacuum level signal and frequency signal change abruptly, it is determined to be a film splashing or boiling over, and the shielding is closed while waiting for recovery, without triggering crystal oscillator switching. In a specific test, when the evaporation reached a cumulative thickness of approximately 450 Å, the first crystal oscillator frequency signal showed a spike jump of approximately 139 Hz, and the vacuum level signal dropped from 8.0 × 10⁻⁶ Å. -3 Pa rose sharply to 2.3 × 10 -2 Pa indicates membrane material splashing; therefore, the shielding should be closed and the system should wait for recovery.

[0065] If the frequency signal changes abruptly while the vacuum level signal shows no significant change (i.e., the fluctuation is within the normal range), it is determined that the crystal oscillator is loose or has poor contact, triggering a switch from the first crystal oscillator to the second. In a specific test, when the evaporation deposition reached a cumulative thickness of approximately 680 Å, the frequency signal of the first crystal oscillator experienced a jump of approximately 243 Hz followed by continuous unstable fluctuations, while the vacuum level signal showed no significant change, stabilizing at 7.8 × 10⁻⁶. -3 ~8.3×10 -3 If the value is within the Pa range, it is determined that the crystal oscillator is loose, triggering a switch.

[0066] When the current frequency of the first crystal oscillator does not meet the validity criterion and the parameters of the feedback estimation model have not been calibrated online, the following degradation processing is executed: reduce the power of the evaporation source at a preset rate and close the shield to terminate the current coating process; or immediately switch to the second crystal oscillator, maintain the current power open-loop operation, and restore closed-loop control after the second crystal oscillator stabilizes.

[0067] Example 4 The technical advantages of the present invention will be fully explained below, based on experimental data.

[0068] First, we compare the difference in plating rate fluctuation during the transition period between this invention and the traditional switching scheme. The comparison curves are shown below. Figure 6 . Figure 6 The graph shows a comparison of the plating rate fluctuation of the present invention and typical existing solutions. The horizontal axis is based on the switching trigger time. The solid line represents the plating rate curve of the present invention, and the dashed line represents the plating rate curve of the traditional open-loop solution. The plating rate fluctuation range of the traditional solution during the transition period is -22.4% to +18.6%, with a root mean square fluctuation of 14.5%. The plating rate of the present invention fluctuates only slightly by ±4.2%, with an RMS fluctuation of only 2.8%. The shaded area represents the 2.3s switching transition period, demonstrating that the closed-loop control significantly suppresses fluctuations.

[0069] This verification experiment used the ZZS-800 electron gun evaporation equipment, with alumina as the film material and a target coating rate of 3.0 Å / s. Thirty sets of complete coating control tests were completed using both the control method of this invention and the existing traditional crystal oscillator switching scheme.

[0070] The existing traditional crystal oscillator switching scheme operates as follows: switching is initiated only when the resonant frequency of the working crystal oscillator drops to a fixed failure threshold. During the switching process, the current crystal oscillator signal acquisition is directly disabled, and the backup crystal oscillator circuit is activated to wait for oscillation to stabilize. Before the backup crystal oscillator reaches a stable state, the controller receives no effective plating rate feedback input, directly stops PID closed-loop regulation, and locks the evaporation source power to open-loop operation before switching. After the backup crystal oscillator stabilizes, the signal is reconnected to restore the closed loop, and the cumulative thickness of the backup crystal oscillator channel is recalculated from zero, and the integral term of the PID controller is reset to zero. The test results and data analysis for each group are as follows.

[0071]

[0072] Table 2: Statistical table of crystal oscillator status at the moment of predictive switching triggering in 30 tests Note: In 30 tests, all switches occurred within... Triggered under normal operating conditions of >4.8MHz, the 100% switching achieves "pre-emptive avoidance".

[0073] As can be seen from the data in Table 2, this invention relies on the frequency decay function to predict the remaining usable lifespan of the crystal oscillator in advance, without waiting for the crystal oscillator frequency to drop to the minimum usable threshold before performing the switching action; all switching operations are completed in the 4.808~4.825MHz range where the crystal oscillator sensing signal is not distorted, thus avoiding the two major defects of traditional threshold triggering mode: distortion of measurement data in the early stage of switching and open-loop loss of control during the transition period.

[0074] Table 3: Convergence Process of RLS Online Calibration Parameters

[0075] Table 3 shows the online parameter identification results of the evaporation source thermodynamic discrete prediction model using the RLS recursive least squares method with a forgetting factor λ=0.97. The model form is as follows: ; The initial parameters were obtained by fitting offline tests with power steps ranging from 5.5kW to 5.78kW. During online operation, the coefficients were continuously iterated and corrected using the measured plating rate with a normal crystal oscillator as the true value. The data convergence pattern can be divided into three stages: First 60 seconds: The model is in a rapid correction phase, with the estimation bias dropping rapidly from the initial uncalibrated state to 6.2%, and parameter fluctuations are relatively obvious; 90s node: The model has achieved effective convergence, and the estimation bias has decreased to 4.1%, both below the 5% process error threshold. , , , The four coefficients tend to stabilize without significant jumps; After 120 seconds: the parameters tend to reach a steady state, and the estimation deviation is stably maintained in the extremely small range of 3.0%~3.5%, which can output high-precision estimated plating rate stably for a long time.

[0076] The experimental data verified the feasibility of the closed-loop fallback control scheme during the transition period of this invention. When the working crystal oscillator ages or the signal is distorted and cannot provide an effective measured coating rate, the output value of the thermodynamic model that has completed convergence is used as the PID feedback input. The prediction error is much smaller than the allowable upper limit of ±15% for the coating process, which completely solves the problem of open-loop operation and drastic fluctuations in coating rate during the transition period of the traditional switching method, and provides algorithmic support for uninterrupted closed-loop adjustment under crystal oscillator failure conditions.

[0077] Table 4: Precision accuracy of feedback quantity estimation model during the transition period

[0078] Note: In 30 switching tests, the average estimation deviation of the feedback quantity estimation model was 3.7%, with a maximum of 13.7%, which meets the process accuracy requirement of ±15% for the coating transition period; the average time for the standby crystal oscillator to stabilize was 2.3s, demonstrating excellent switching response speed.

[0079] Table 4 shows the results of closed-loop bottom-line switching tests under all crystal oscillator failure conditions. The estimated plating rate output by the thermodynamic model with RLS parameter identification was used as the PID feedback quantity throughout the process.

[0080] Data shows that the average prediction deviation of the model during a single switch is only 3.7%, and the maximum prediction deviation of the entire sample is 13.7%, which does not exceed the process error threshold. It can completely replace the measured signal of the distorted crystal oscillator to maintain closed-loop regulation, eliminating the rate drift defect caused by open loop from the source. The backup crystal oscillator takes an average of only 2.3s from starting oscillation to frequency stabilization, and the shortest is only 1.6s. The transition period is extremely short and will not interfere with the process cycle of the continuous coating production line.

[0081] Therefore, it can be seen that when the crystal oscillator is deposited too thickly, the signal noise exceeds the standard, and the frequency reading is distorted, the prediction model can seamlessly support PID closed-loop power regulation to ensure that the output power of the evaporation source is continuously controllable.

[0082] Table 5: Comparison of PID integral term inheritance effects

[0083] Note: Both sets of experiments used the same smooth weighted transition logic, with the only variable being whether to migrate the PID integral term; the data shows that the inheritance of the integral term can significantly reduce the transient disturbance during switching and improve the dynamic response performance of the system.

[0084] As shown in Table 5, each control group underwent 15 crystal oscillator switching tests. The control group used the traditional scheme, where the integral term of the spare crystal oscillator PID controller was cleared and re-accumulated from zero. The experimental group used the complete migration and inheritance technology of the PID integral terms of the old and new channels of this invention to verify the optimization effect of control state inheritance on the switching dynamic performance.

[0085] Among them, for power disturbance suppression, the instantaneous power jump during switching without integral inheritance is as high as 0.58kW, which can easily cause sudden changes in the heat load of the evaporation source; this solution has a jump of only 0.03kW, which greatly reduces the disturbance amplitude by 94.8%, thus avoiding the coating rate drift caused by drastic fluctuations in crucible temperature from the source.

[0086] Regarding the suppression of dynamic overshoot / undershoot in deposition rate, compared with the non-integral term inherited deposition rate, the positive overshoot was reduced from 15.7% to 4.2%, an improvement of 73.2%, and the negative undershoot was reduced from 9.4% to 3.8%, an improvement of 59.6%. This significantly reduces the instantaneous deviation of the film deposition rate and avoids defects such as excessively thick or thin films in certain areas.

[0087] Regarding steady-state convergence speed, the adjustment time for the ±3% process allowable error band of coating rate regression is shortened from 6.5s to 1.8s, and the convergence time is reduced by 72.3%. The closed-loop system quickly returns to steady state, improving the consistency of the coating process.

[0088] As can be seen from the above, traditional crystal oscillator switching causes the PID integral value to be reset, which is equivalent to restarting the adjustment process of the controller, resulting in large dynamic oscillations and long adjustment cycles. The present invention migrates the integral term accumulated by the previous crystal oscillator operation to the backup channel, completely continuing the historical control quantity and realizing seamless handover of controller status.

[0089] Table 6: Statistics on the Accuracy of Multidimensional Cross-Association Diagnosis

[0090] Note: Through cross-correlation diagnosis of multiple signals such as frequency, vacuum degree, and evaporation source power, a total of 11 unnecessary crystal oscillator switchings were avoided, and the comprehensive diagnostic accuracy for all fault types was 90.9%.

[0091] As shown in Table 6, this invention abandons the crude logic of relying solely on frequency jumps to determine crystal oscillator faults. It simultaneously collects three signals—crystal oscillator resonant frequency, cavity vacuum degree, and evaporation source output power—to conduct coupled correlation analysis, distinguishing between crystal oscillator hardware faults and process pseudo-anomalies such as film material disturbances and thermal drift. Switching is only performed when the crystal oscillator is determined to be damaged, and process disturbances are only addressed by closing the shield and allowing the device to stand still for recovery.

[0092] Hardware-related faults, such as loose crystal oscillator, depleted film material, or crystal oscillator blockage, can be diagnosed with 100% accuracy and can precisely trigger necessary switching to ensure continuous coating operation. For process disturbance-related faults, such as film splashing and crystal oscillator thermal drift, the diagnostic accuracy rates were 87.5% and 80.0%, respectively, avoiding a total of 11 meaningless crystal oscillator switching. The overall diagnostic accuracy of 22 abnormal events under all operating conditions is 90.9%, which significantly reduces the consumption of crystal oscillator materials and reduces the risk of process breakpoints caused by frequent equipment operation.

[0093] Compared to the traditional approach of "switching when the frequency is abnormal," the multi-parameter coupled diagnosis improves the fault tolerance of the entire control system and serves as a fallback module for the seamless switching solution of this invention.

[0094] Table 7: Comparison of Switching Performance between the Invention Scheme and Typical Existing Schemes

[0095] Note: Both sets of comparative experiments were conducted using the ZZS-800 electron gun evaporation equipment, Al2O3 film material, and the same process conditions with a target deposition rate of 3.0 Å / s. The only variable was the crystal oscillator switching control logic.

[0096] The control group uses the industry-standard threshold triggering and open-loop power locking crystal switching method, which is the traditional defective solution pointed out in the background technology; the experimental group uses the integrated control strategy of this invention, which includes early prediction and switching, closed-loop fallback during the transition period, PID state inheritance, and weighted smooth transition.

[0097] Specifically, the comparative experiments in Table 7 were conducted under identical external conditions: both groups of experiments used the same ZZS-800 electron gun vacuum evaporation machine equipped with an EGN-406M electron gun as the evaporation source; the film material was Al2O3 (purity 99.99%); the target deposition rate was 3.0 Å / s; and the background vacuum was 5.0 × 10⁻⁶. -3 Pa, while the working vacuum degree is 8.0 × 10⁻⁶. - 3 Pa, substrate temperature is 150℃, plating pan speed is 60rpm, crystal oscillator is 5MHz AT-cut quartz crystal oscillator, and minimum usable frequency threshold is 4.8MHz.

[0098] The only variable in both sets of experiments was the crystal oscillator switching control logic: Control group (typical existing scheme): The crystal oscillator switching trigger condition is that the working crystal oscillator frequency drops to a fixed threshold of 4.8MHz; after the switching is triggered, the signal of the current crystal oscillator is immediately stopped, the backup crystal oscillator circuit is activated and waited for it to stabilize; during the stabilization period of the backup crystal oscillator (measured average of about 2.3 seconds), the controller has no effective plating rate feedback input, the PID controller stops closed-loop regulation, and the evaporation source power is locked to the power value at the last moment before the switching and runs in open loop; after the backup crystal oscillator frequency stabilizes, its rate signal is reconnected to resume closed-loop control; the cumulative thickness of the backup crystal oscillator channel is recalculated from zero, and the integral term of the PID controller is cleared and reset.

[0099] Experimental group (invention scheme): The crystal oscillator switching trigger condition is that the available remaining time predicted based on the frequency decay function is less than the safe lifetime threshold (in this embodiment). =30s); after the switching is triggered, the switching transition phase begins. Path 1 is selected based on whether the first crystal oscillator meets the validity criterion, ensuring that the PID controller always has feedback input and the closed-loop regulation is uninterrupted during the transition period. After the frequency of the standby crystal oscillator stabilizes, the current cumulative thickness value of the first crystal oscillator and the current value of the integral term of the PID controller are written as initial values ​​into the standby crystal oscillator control channel. The PID feedback input is smoothly switched from the old source to the real-time plating rate signal of the standby crystal oscillator through a weighted mixing formula, with a transition time of 2 seconds.

[0100] When the first crystal oscillator does not meet the validity criterion, path two will be selected. Under the same equipment conditions, the same switching control framework will be used. Path two only replaces the measured plating rate of the first crystal oscillator with the plating rate estimated by the thermodynamic model of the evaporation source during the transition period. The remaining parameters are inherited and the weighted mixed switching logic remains the same. The corresponding comparison data for path two are not described in this embodiment.

[0101] As shown in Table 7, in terms of the ability to suppress coating rate fluctuations, the traditional solution operates in an open loop during the switching transition period. Affected by the thermal inertia of the evaporation source and the disturbance of film material consumption, the root mean square fluctuation of the coating rate is as high as 14.5%. The present invention relies on dual-path closed-loop uninterrupted control to compress the fluctuation to 2.8%, and the fluctuation amplitude is directly reduced by 81%. It significantly reduces the film thickness unevenness caused by a single switch from the root cause. After multiple accumulations, the overall thickness deviation is significantly reduced.

[0102] Regarding the steady-state convergence speed of PID, the traditional solution requires the backup channel PID integral to be zeroed, and the controller needs to be readjusted. It takes 8.2s to return to the ±3% process allowable error range. The present invention migrates the historical integral term and can enter steady state in only 1.8s, reducing the adjustment time by 78% and enabling the process to return to stability quickly.

[0103] The total switching time of this invention, including prediction triggering, backup crystal oscillator start-up, and smooth signal transition, is only 4.1s, which is 78% shorter than the traditional solution of 18.3s. It has minimal impact on the cycle time of continuous mass production coating production lines and is more efficient.

[0104] The cumulative film thickness error comparison bar chart after multiple switching is shown below. Figure 7 As shown. Figure 7 A comparison chart of cumulative film thickness deviation under different switching times is presented. The filled bars represent the measured deviations of the present invention and the traditional scheme, respectively. The error of the traditional scheme increases linearly with the number of switching times, and the deviation exceeds 9% after 5 switching times. The error of the present invention is always controlled within 1.1%, with no cumulative deterioration trend. This verifies that the parameter inheritance and closed-loop fallback scheme can ensure the accuracy of film thickness in the long term.

[0105] The above embodiments use Al2O3 elemental oxide film as an example for detailed description, but the scope of protection of this invention is not limited to this specific film. The method and apparatus of this invention are also applicable to other common vapor deposition film materials, including but not limited to: metal film materials (such as Au, Ag, Al, Cu, Cr), fluoride film materials (such as MgF2, CaF2), sulfide film materials (such as ZnS), and semiconductor film materials (such as Si, Ge). For different film materials, the basic working principle of the frequency attenuation prediction and feedback estimation model remains unchanged; for different film materials, the core algorithms of the frequency attenuation prediction and evaporation source estimation models do not need to be modified. Only the material density, Z-Ratio, and Tooling process coefficient need to be adjusted, and the initial parameters of the estimation model need to be updated through offline power step tests to adapt it for use.

[0106] The above description is merely an 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's 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 seamless switching control of crystal oscillators in a coating process, characterized in that, Includes the following steps: Continuously acquire the frequency values ​​of the first crystal oscillator at multiple sampling times during the current operation, and denote them as the first frequency sequence. ; According to the first frequency sequence and the preset minimum available frequency threshold Calculate the remaining available time for the first crystal oscillator; When the remaining usable time of the first crystal oscillator is less than a preset safe lifespan threshold When the switching process from the first crystal oscillator to the second crystal oscillator is triggered, the switching process from the first crystal oscillator to the second crystal oscillator includes a switching transition phase and a switching success phase. During the switching transition phase, it is determined whether the current frequency of the first crystal oscillator meets the preset validity criteria. If it does, the real-time plating rate signal of the first crystal oscillator is used as the feedback input of the PID controller. If it does not meet the criteria, the estimated plating rate output by a feedback estimation model is used as the feedback input of the PID controller. During the successful switching phase, the second crystal oscillator is used as the current working crystal oscillator. The current cumulative thickness of the first crystal oscillator and the current value of the integral term of the PID controller are written as initial values ​​into the control channel corresponding to the second crystal oscillator to continue the coating process. According to the first frequency sequence and the preset minimum available frequency threshold Calculate the remaining available time of the first crystal oscillator, including: According to the first frequency sequence Construct the frequency decay function of the first crystal oscillator: ； in, Indicates the current moment. Indicates the sampling time. This represents the rate of change of frequency at the current moment. This represents the acceleration due to the change in frequency at the current moment. ; Based on the frequency decay function of the first crystal oscillator and the preset minimum usable frequency threshold ,make Solve the frequency decay function to find the frequency of the first crystal oscillator decreasing to Required remaining time ,Will The remaining available time for the first crystal oscillator; When the absolute value of the frequency change acceleration is lower than a preset threshold, the frequency decay function degenerates into a linear function. The remaining available time of the first crystal oscillator is .

2. The crystal oscillator seamless switching control method in the coating process according to claim 1, characterized in that, The preset validity criteria include: the current frequency of the first crystal oscillator is higher than the minimum available frequency threshold. And / or the frequency signal noise of the first crystal oscillator is lower than a preset noise degradation threshold.

3. The crystal oscillator seamless switching control method in the coating process according to claim 2, characterized in that, When the current frequency of the first crystal oscillator meets the preset validity criterion, during the switching transition phase: The real-time plating rate signal of the first crystal oscillator is used as the feedback input of the PID controller to activate the oscillation circuit of the second crystal oscillator and monitor its frequency stability. Before the frequency of the second crystal oscillator stabilizes, the second crystal oscillator does not output power regulation to the evaporation source power supply.

4. The crystal oscillator seamless switching control method in the coating process according to claim 3, characterized in that, After the frequency of the second crystal oscillator stabilizes, the switching success phase begins, which includes the following steps: The cumulative parameters in the control channel corresponding to the first crystal oscillator are written into the control channel corresponding to the second crystal oscillator. The cumulative parameters include the current cumulative thickness value of the first crystal oscillator, the current value of the integral term of the PID controller corresponding to the first crystal oscillator, and the current plating rate value of the first crystal oscillator. Switching the feedback input of the PID controller from the real-time plating rate signal of the first crystal oscillator to the real-time plating rate signal of the second crystal oscillator is expressed as: ； in, This is the real-time plating rate signal of the second crystal oscillator. This is the real-time plating rate signal of the first crystal oscillator. It is a weighting coefficient that linearly increases from 0 to 1 within a preset transition time, starting from the moment when the second crystal oscillator frequency stabilizes.

5. The crystal oscillator seamless switching control method in the coating process according to claim 2, characterized in that, When the current frequency of the first crystal oscillator does not meet the preset validity criterion, during the switching transition phase: Stop using the real-time plating rate signal of the first crystal oscillator as the feedback input of the PID controller; The estimated coating rate, output in real time by the thermodynamic model of the evaporation source, is used as the feedback input of the PID controller. The oscillation circuit of the second crystal oscillator is activated, and the frequency stability of the second crystal oscillator is continuously monitored. Before the frequency of the second crystal oscillator is stable, the second crystal oscillator does not output power regulation to the evaporation source power supply. The thermodynamic model of the evaporation source is a discretized transfer function that maps the real-time value of the evaporation source power to an estimated coating rate. ； in, The estimated plating rate at the k-th sampling time is... Let be the evaporation source power at the k-th sampling time. , , , The discretized parameters are determined through online calibration. The online calibration uses the measured coating rate of the first crystal oscillator during the normal coating stage as the calibration true value and is performed using a recursive least squares method with a forgetting factor. The forgetting factor ranges from 0.95 to 0.

99.

6. The crystal oscillator seamless switching control method in the coating process according to claim 5, characterized in that, After the frequency of the second crystal oscillator stabilizes, the switching success phase begins, which includes the following steps: The cumulative parameters in the control channel corresponding to the first crystal oscillator are written into the control channel corresponding to the second crystal oscillator. The cumulative parameters include the current cumulative thickness value of the first crystal oscillator and the current value of the integral term of the PID controller corresponding to the first crystal oscillator. The feedback input of the PID controller is switched from the estimated plating rate output by the evaporation source thermodynamic model to the real-time plating rate signal of the second crystal oscillator, as follows: ； in, This is the real-time plating rate signal of the second crystal oscillator. The estimated coating rate is output by the thermodynamic model of the evaporation source. It is a weighting coefficient that linearly increases from 0 to 1 within a preset transition time, starting from the moment when the second crystal oscillator frequency stabilizes.

7. A crystal oscillator seamless switching control method in a coating process according to claim 4 or 6, characterized in that, The weighting coefficient Generate in the following way: Taking the moment when the second crystal oscillator frequency stabilizes as the zero point of timing, the transition time is recorded as... ,but: ； The total time will be accumulated after the system stabilizes.

8. The crystal oscillator seamless switching control method in the coating process according to claim 1, characterized in that, During the successful switching phase, the tooling parameters corresponding to the second crystal oscillator are also loaded into the control channel corresponding to the second crystal oscillator, replacing the tooling parameters corresponding to the first crystal oscillator.

9. The crystal oscillator seamless switching control method in the coating process according to claim 1, characterized in that, The remaining usable time of the first crystal oscillator is not less than a preset safe lifespan threshold. During this period, the frequency signal of the first crystal oscillator was continuously monitored; When an abnormality is detected in the frequency signal of the first crystal oscillator, the vacuum degree signal and / or the evaporation source power feedback signal are collected synchronously, and the frequency signal is cross-correlation analysis is performed with the vacuum degree signal and / or the evaporation source power feedback signal. If the vacuum signal and the frequency signal change abruptly in sync, it is determined to be a film material splashing or boiling over, and the operation of closing the shield and waiting for recovery is executed without triggering crystal oscillator switching; If the frequency signal changes abruptly while the vacuum level signal remains unchanged, it is determined that the crystal oscillator is loose or has poor contact, triggering a switch from the first crystal oscillator to the second crystal oscillator.

10. A crystal oscillator seamless switching control device in a coating process, characterized in that, The apparatus is configured to perform the method as described in any one of claims 1 to 9, comprising: The acquisition module is used to continuously acquire the frequency values ​​of the first crystal oscillator in the current operation at multiple sampling times; The prediction module is used to construct a frequency decay function of the first crystal oscillator based on the frequency value, and to calculate the remaining available time of the first crystal oscillator based on the frequency decay function and a preset minimum available frequency threshold. The determination module is used to trigger a switching process from the first crystal oscillator to the second crystal oscillator when the available remaining time is less than a preset safe lifespan threshold; and is used to perform an anomaly determination and selectively trigger a switching when an anomaly is detected in the frequency signal of the first crystal oscillator during the period when the available remaining time is not less than the safe lifespan threshold. The feedback management module is used to select, based on whether the current frequency of the first crystal oscillator meets the preset validity criteria, the real-time plating rate signal of the first crystal oscillator or the estimated plating rate output by a feedback estimation model as the feedback input of the PID controller during the switching transition phase of the switching process. The state transition module is used to write the current cumulative thickness value of the first crystal oscillator and the current value of the integral term of the PID controller into the control channel corresponding to the second crystal oscillator during the successful switching phase of the switching process. The PID control module is used to continue the coating process based on the real-time signal of the second crystal oscillator and the written parameters.

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