Bias Supply Transition Control for Faster Plasma State Settling
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Solution Overview
Problem
Bias supplies in plasma processing systems experience undesirable oscillations and slower settling times during state changes, leading to suboptimal ion energy distribution functions (IEDFs) and etching performance.
Innovation Solution
A bias supply system with a switch network and power supplies configured to apply an asymmetric periodic voltage waveform, controlled by a controller that adjusts the voltage and switching frequency during state transitions to mitigate oscillations and achieve faster settling times, using a transition control module to modify the fundamental frequency of the waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the bias supply undergoes state changes during operation, then different ion energy distribution functions can be achieved to control etching performance, but undesirable oscillations occur during transitions between states
Solution Approach 1:
The transition control module performs preliminary actions by detecting when a state change is requested and proactively adjusting the fundamental frequency during the transition period before the new state is fully established. This prevents oscillations from occurring in the first place rather than correcting them afterward.
Solution Approach 2:
The system dynamically adjusts the fundamental frequency of the asymmetric periodic voltage waveform during state transitions. The transition control module modifies the frequency in real-time based on the transition state, making the system adaptive and responsive to changing operational requirements while maintaining stability.
2Adaptability or versatility
If the bias supply undergoes state changes to control ion energy distribution, then etching performance can be optimized, but the settling time during transitions increases
Solution Approach 1:
The transition control module applies preliminary anti-action by detecting the transition request and immediately adjusting the fundamental frequency to counteract the oscillatory behavior that would naturally occur during state changes. This preemptive frequency adjustment prevents the system from entering an oscillatory state, thereby reducing settling time.
Solution Approach 2:
The system changes the fundamental frequency parameter during transitions to optimize settling behavior. By adjusting this key parameter in response to state change requests, the system achieves faster settling while maintaining the ability to provide different ion energy distribution functions for optimized etching performance.
3Productivity
If high power is applied to achieve desired etch rate, then etching performance improves, but wafer or process hardware may be damaged
Solution Approach 1:
The bias supply applies periodic action by delivering asymmetric periodic voltage waveforms that create pulsed plasma conditions. This periodic delivery of energy allows high power to be applied during active etching phases while providing natural rest periods, thereby achieving high etch rates without continuous exposure that would cause damage to the wafer or hardware.
Data Source
AI summary
Bias supplies and bias control methods are disclosed. One method comprises applying an asymmetric periodic voltage waveform and providing a corresponding current waveform at an output node relative to a return node; receiving a signal to change from a current state of the asymmetric periodic voltage waveform to a next state of the asymmetric periodic voltage waveform; and adjusting, during a transition from the current state to the next state, at least one portion of the asymmetric periodic voltage waveform and simultaneously adjusting a fundamental frequency of the asymmetric periodic voltage waveform to settle at the next state.