Pulsed RF Plasma Frequency Tuning via Calibration Phase
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing frequency tuning methods for pulsed radio frequency plasma processing result in significant impedance mismatches at the start of each pulse, disrupting processing and potentially damaging substrates, as the tuned frequency at the end of a pulse is not well-suited for the start of the subsequent pulse.
Innovation Solution
A method is introduced where a fixed initial RF frequency is selected and used at the start of each pulse, determined during a calibration phase with a dummy substrate to minimize impedance mismatch, and then adjusted for the remainder of each pulse to optimize power delivery, ensuring consistent and accurate processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tuned frequency at the end of a pulse is used at the start of a subsequent pulse, then frequency tuning is continuous, but impedance mismatch occurs at the start of pulses disrupting processing
Solution Approach 1:
The patent applies preliminary action by pre-tuning the RF frequency during a calibration phase before actual substrate processing begins. A dummy substrate is used to determine an optimal initial frequency that minimizes impedance mismatch at pulse starts. This pre-established frequency setting is then used as the starting point for each pulse during processing, avoiding the instability that would result from using end-of-pulse frequencies from previous pulses.
2Power
If frequency is adjusted pulse to pulse to minimize impedance mismatch, then power delivery is optimized, but processing consistency deteriorates due to frequency variations
Solution Approach 1:
The patent performs frequency optimization in advance during a calibration phase using a dummy substrate, establishing a stable initial frequency before processing begins. This pre-determined frequency is then maintained as the initial setting for each pulse, providing both optimal power delivery and processing consistency.
Solution Approach 2:
The patent uses a dummy substrate as a copy or surrogate for the actual substrate during the calibration phase. The frequency settings optimized on the dummy substrate are then transferred and applied to the real substrate processing, ensuring consistent results without the variability introduced by pulse-to-pulse frequency adjustments.
3Reliability
If RF frequency is tuned during each pulse, then impedance matching is improved, but substrate damage risk increases due to large initial mismatch
Solution Approach 1:
The patent applies preliminary action by pre-determining an optimal initial RF frequency during calibration before substrate processing. This pre-optimized frequency minimizes impedance mismatch at the start of each pulse, preventing the large initial mismatches that cause substrate damage while ensuring reliable plasma ignition and sustainment throughout the pulse duration.
Data Source
AI summary
This disclosure describes systems, methods, and apparatus for pulsed RF power delivery to a plasma load for plasma processing of a substrate. In order to maximize power delivery, a calibration phase using a dummy substrate or no substrate in the chamber, is used to ascertain a preferred fixed initial RF frequency for each pulse. This fixed initial RF frequency is then used at the start of each pulse during a processing phase, where a real substrate is used and processed in the chamber.