Impedance Matching Capacitor Measurement in Live RF Plasma Circuits
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Solution Overview
Problem
Conventional capacitance measurement methods in semiconductor fabrication require disconnecting capacitors from high power RF circuits, leading to inaccuracies and wafer non-uniformity due to issues like stepper motor slipping couplers, which affects the uniformity and repeatability of semiconductor processing.
Innovation Solution
A method and apparatus for measuring capacitance without disconnecting the capacitor from the RF power circuit, using techniques such as voltage measurement, resonant frequency analysis, and impedance matching, allowing for real-time adjustment of capacitance values to maintain impedance matching and reduce station-to-station variations in RF power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitance measurement methods are used (disconnecting capacitor from RF circuit), then measurement can be performed, but measurement precision deteriorates due to stepper motor slipping couplers and inability to measure in-situ
Solution Approach 1:
The patent introduces an intermediary measurement circuit that couples to the capacitor through a coupling capacitor and resistor network, allowing capacitance measurement without direct disconnection. The intermediary circuit extracts measurement signals while the main RF circuit remains connected and operational.
Solution Approach 2:
The patent replaces the mechanical stepper motor coupling system with an electrical measurement approach. Instead of mechanically disconnecting and reconnecting the capacitor, the system uses electrical signal extraction through the intermediary circuit to measure capacitance while maintaining the electrical connection.
2Manufacturing precision
If capacitor is disconnected from RF circuit for measurement, then capacitance can be measured, but manufacturing precision deteriorates due to incorrect capacitor values and station-to-station variations
Solution Approach 1:
The patent enables continuous operation by allowing capacitance measurement to occur while the capacitor remains connected to the RF circuit. The measurement process does not interrupt the RF power distribution or require stopping the semiconductor processing operation, thus maintaining continuous useful action.
Solution Approach 2:
The system performs self-diagnosis and self-adjustment by continuously monitoring capacitor values through the intermediary measurement circuit. The system can detect drift in capacitance values and automatically adjust impedance matching parameters without external intervention or manual disconnection.
3Productivity
If RF power is distributed to multiple stations, then productivity increases, but reliability deteriorates due to station-to-station variations in RF power distribution
Solution Approach 1:
The patent implements feedback control by measuring the capacitance values of capacitors in the impedance matching circuits of multiple stations and using these measurements to adjust RF power distribution. The system continuously monitors and adjusts parameters to compensate for station-to-station variations, ensuring uniform RF power delivery across all stations.
Solution Approach 2:
The patent applies local adjustments at each station based on individual capacitor measurements. Each station's impedance matching circuit is tuned independently based on its specific capacitor values, allowing customized optimization for each station while maintaining overall system productivity.
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
Enables accurate capacitance measurement and adjustment during semiconductor processing, improving wafer-to-wafer uniformity and reducing the risk of incorrect capacitor values, thereby enhancing the reliability and efficiency of semiconductor fabrication processes.
Implementation Method 1
a filter having a passband including a first frequency greater than a 10th harmonic frequency of the target frequency of the RF power distributed to the multiple stations, and a stopband including the target frequency of the RF power distributed to the multiple stations
Implementation Method 2
measuring a capacitance of a capacitor in the impedance matching circuit without disconnecting the capacitor from the impedance matching circuit
Data Source
AI summary
A method and an apparatus of plasma-assisted semiconductor processing is provided. The method comprises: a) providing substrates at each of the multiple stations; b) distributing RF power including a first target frequency to multiple stations to thereby generate a plasma in the stations, wherein the RF power is distributed according to a RF power parameter configured to reduce station to station variations; c) tuning an impedance matching circuit for a first station included in the multiple stations while distributing RF power to the first station by: i) measuring a capacitance of a capacitor in the impedance matching circuit without disconnecting the capacitor from the impedance matching circuit; and ii) adjusting, according to the capacitance measured in (i) and the RF power parameter, a capacitance of the capacitor; and d) performing a semiconductor processing operation on the substrate at each station.