Self-Bias Calculation in Process Chamber Substrate Support
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Solution Overview
Problem
Conventional methods for calculating self-bias on a substrate in a process chamber are inaccurate, especially when multiple frequencies are used, and do not account for non-linearities in the chamber, leading to improper substrate chucking and potential breakage.
Innovation Solution
A method involving measuring DC potential, voltage, current, and phase shift at a substrate support while providing bias power, calculating effective impedance, and using linear coefficients to determine self-bias, which can be applied to both single and multiple frequency scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methodologies for calculating self-bias are used, then the calculation process is simple, but the accuracy of self-bias estimation deteriorates
Solution Approach 1:
The patent transforms the self-bias calculation from a direct measurement approach to an impedance-based calculation approach. By measuring impedance parameters (real and imaginary components) at the cathode and using linear relationships with measured DC potential, the method achieves accurate self-bias estimation while maintaining practical implementation complexity
Solution Approach 2:
The patent introduces impedance as an intermediary parameter to bridge the relationship between measurable quantities (voltage, current, DC potential) and the target parameter (self-bias). The linear relationships established between impedance and DC potential serve as intermediary equations that enable accurate self-bias calculation without direct measurement
2Adaptability or versatility
If conventional single-frequency methodologies are used, then the implementation is straightforward, but the applicability to multi-frequency scenarios deteriorates
Solution Approach 1:
The patent creates a universal self-bias calculation methodology that functions across single-frequency and multi-frequency scenarios. The core impedance-based approach with linear relationships remains the same, but can be applied to any frequency configuration, making the method universally applicable to different RF power source configurations
Solution Approach 2:
The patent segments the self-bias calculation into independent frequency components. For multi-frequency operation, the total self-bias is calculated as the sum of self-bias contributions from each frequency component, allowing the methodology to handle complex multi-frequency scenarios by breaking them down into manageable single-frequency calculations
3Manufacturing precision
If non-linearities in the chamber are not accounted for, then the calculation process remains simple, but the substrate chucking accuracy deteriorates
Solution Approach 1:
The patent incorporates feedback by using measured DC potential values in the linear relationships to determine impedance parameters. This measured feedback from the actual chamber conditions allows the calculation to account for non-linearities and achieve accurate substrate chucking control
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
This method provides an accurate calculation of self-bias, enhancing the matching of process chamber performance and preventing substrate breakage by accounting for non-linearities and multiple frequency conditions.
Implementation Method 1
calculating an effective impedance of the cathode by determining a linear relationship between a calculated voltage and the measured DC potential of the substrate
Implementation Method 2
measuring a voltage, a current and a phase shift at a matching network coupled to the power source
Implementation Method 3
Conventional process chambers utilizing an electrostatic chuck typically include a grid, or mesh electrode, embedded within the chuck that is biased negatively to create a static potential difference with the substrate, thereby chucking the substrate
Data Source
AI summary
Methods for calculating a self-bias on a substrate in a process chamber may include measuring a DC potential of a substrate disposed on a substrate support of a process chamber while providing a bias power from a power source to a cathode at a first frequency; measuring a voltage, current and phase shift at a matching network coupled to the power source while providing the bias power; calculating an effective impedance of the cathode by determining a linear relationship between a calculated voltage and the measured DC potential of the substrate; calculating a first linear coefficient and a second linear coefficient of the linear relationship between the calculated voltage and the measured DC potential of the substrate; and calculating a self bias on the substrate by utilizing the first linear coefficient, second linear coefficient, measured DC potential of the substrate, effective impedance, and measured phase shift.