Dynamic Pressure Control for Low-Pressure Plasma Processing
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Solution Overview
Problem
Conventional pressure control methods in low-pressure processing chambers, such as plasma processing chambers, are slow and require gain optimization for each condition, leading to long control times and potential hunting issues, especially when dealing with variations in gas type, gas flow rate, or target pressure.
Innovation Solution
A pressure control device that adjusts the low-pressure processing chamber to a desired pressure by optimizing integral and proportional gains based on exhaust speed and valve opening, allowing for quick and stable control regardless of gas type, gas flow rate, or target pressure, using formulas that calculate exhaust speed and valve opening operation amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PID control with fixed gain values is used, then control stability is maintained, but control time becomes excessively long and hunting occurs with nonlinear throttle valves
Solution Approach 1:
The patent transforms the fixed gain PID control into a dynamic control system where the proportional gain Gp and integral gain Gi are continuously adjusted based on real-time pressure deviation and pressure change rate. The control amount ΔV is calculated as a function of both current pressure deviation (Pn-P0) and pressure change rate ((Pn-Pn-1)/Δt), enabling the system to adapt to nonlinear throttle valve characteristics and varying operating conditions, thus reducing control time while maintaining stability
Solution Approach 2:
The patent changes the control parameters from fixed gain values to dynamically varying parameters. The control amount ΔV is expressed as a function of pressure deviation and pressure change rate, with different weighting factors applied based on the magnitude of these parameters. This parameter transformation allows the system to respond more aggressively to large deviations while providing gentle control near the target pressure, eliminating hunting and reducing overall control time
2Productivity
If optimal gain values are used for specific conditions, then control performance is improved, but the system requires separate optimization for each gas type, flow rate, and target pressure
Solution Approach 1:
The patent creates a universal control algorithm that functions across different gas types, flow rates, and target pressures without requiring separate optimization for each condition. The control amount ΔV is calculated using a unified formula that incorporates pressure deviation and pressure change rate with adaptive weighting, allowing the same control logic to effectively handle various operating conditions. This universal approach eliminates the need for multiple sets of optimized gain values while maintaining high control speed
Solution Approach 2:
The dynamic adjustment of control parameters based on real-time pressure deviation and change rate enables the system to automatically adapt to different operating conditions. Rather than requiring pre-optimized fixed gains for each condition, the system dynamically modulates the control amount to match the current state, achieving optimal control performance across diverse scenarios with a single unified algorithm
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables rapid and stable pressure control, reducing control time to achieve target pressures within one or two seconds, regardless of gas type or flow rate, and minimizes hunting, even with nonlinear throttle valve characteristics.
Implementation Method 1
plasma generating means which supplies electromagnetic energy to the processing gas supplied to the low pressure processing chamber and generates plasma
Data Source
AI summary
A control method which quickly adjusts a plasma processing apparatus to a desired pressure regardless of gas type, gas flow rate or target pressure simply by optimizing constants. The plasma processing apparatus includes: gas supply means which supplies processing gas to a low pressure processing chamber; plasma generating means which supplies electromagnetic energy to the processing gas in the low pressure processing chamber and generates plasma; exhaust means which exhausts gas in the low pressure processing chamber; gas pressure measuring means which measures gas pressure in the low pressure processing chamber; exhaust speed adjusting means which adjusts exhaust speed of gas to be exhausted by the exhaust means; and an arithmetic and control unit calculates an exhaust speed to make the gas pressure measured by the pressure measuring means equal to a target value, and controls the exhaust speed adjusting means according to the calculation result.