Step-wise Impedance Matching Network Tuning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing impedance matching networks in plasma systems face challenges in tuning the variable capacitance and RF frequency simultaneously due to differing control speeds, making it difficult to achieve optimal values directly.
Innovation Solution
The impedance matching network is tuned in a step-wise fashion, where the variable capacitance is adjusted in steps, and the RF frequency is varied quickly to achieve local optimal values, allowing for the calculation of optimal capacitance and frequency values incrementally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the variable capacitance and RF frequency are tuned simultaneously to achieve optimal values, then the impedance matching precision is improved, but the control complexity increases due to differing control speeds of the two variables
Solution Approach 1:
The patent segments the tuning process into two distinct phases: first adjusting the variable capacitance to a preliminary value, then adjusting the RF frequency to achieve optimal impedance matching. This segmentation resolves the contradiction by separating the control of two variables that have different control speeds, thereby maintaining control simplicity while achieving precise impedance matching.
2Productivity
If the variable capacitance is adjusted in steps with quick RF frequency variation, then the tuning speed is improved, but the manufacturing precision of optimal values may be compromised
Solution Approach 1:
The patent applies preliminary action by first setting the variable capacitance to a predetermined preliminary value before adjusting the RF frequency. This preliminary setup enables faster tuning overall because the capacitance (which changes slowly) is set once, and then the frequency (which changes quickly) is adjusted to achieve optimal matching, thus improving tuning speed without sacrificing precision.
Solution Approach 2:
The patent uses feedback through a match network model that predicts RF voltage, current, and phase based on measured load impedance and current settings. This feedback mechanism allows the system to determine optimal frequency values for each capacitance step, ensuring precise optimal values are achieved even though the capacitance is adjusted in discrete steps.
3Ease of operation
If the variable capacitance is set in advance in a recipe and does not vary within a recipe step, then the control simplicity is improved, but the adaptability to achieve optimal impedance matching decreases
Solution Approach 1:
The patent compensates for the fixed capacitance value by introducing another degree of freedom: RF frequency adjustment. While the capacitance remains fixed at a preliminary value for simplicity, the system achieves adaptability by varying the RF frequency to find optimal impedance matching conditions, thus maintaining control simplicity while preserving matching adaptability through frequency tuning.
Solution Approach 2:
The patent changes the operational parameter from variable capacitance to variable frequency. Instead of varying capacitance continuously to achieve optimal matching, the system keeps capacitance fixed at a preliminary value and achieves adaptability by adjusting the RF frequency parameter, thereby maintaining control simplicity while preserving matching flexibility.
Data Source
AI summary
Systems and methods for tuning an impedance matching network in a step-wise fashion are described. By tuning the impedance matching network in a step-wise fashion instead of directly to achieve optimum values of a radio frequency (RF) and a combined variable capacitance, processing of a wafer using the tuned optimal values becomes feasible.