Edge Sheath RF Phase Tuning for Uniform Plasma Etching
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Solution Overview
Problem
Plasma etching processes in semiconductor fabrication face challenges with spatial non-uniformities in plasma characteristics due to varying radiofrequency signal transmission, leading to inconsistencies in etching results across semiconductor wafers.
Innovation Solution
A tunable edge sheath system with independently powered edge electrodes, using multi-state pulsed RF signals to adjust voltage setpoints and phase adjustments, ensuring uniform plasma processing by matching phases and optimizing capacitance settings to maintain plasma sheath consistency despite edge ring wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If RF power is applied to the edge electrode to maintain plasma sheath levels, then plasma uniformity is improved, but phase mismatch and voltage setpoint drift occur due to edge ring wear
Solution Approach 1:
The system continuously monitors the actual phase and voltage setpoint of the pulsed RF signal and compares it with target values. When deviations are detected due to edge ring wear, the control system automatically adjusts impedance matching network parameters and voltage setpoints to restore optimal operation, creating a closed-loop feedback mechanism that maintains reliability despite component degradation
Solution Approach 2:
The patent implements dynamic adjustment of voltage setpoints for different pulse states (on-state, off-state, intermediate states) based on real-time detection of phase deviations. The system adapts operating parameters continuously during plasma processing to compensate for edge ring wear, transforming a static system into a dynamically responsive one that maintains optimal performance over time
2Manufacturing precision
If multi-state pulsed RF signals are used to control plasma characteristics, then etching precision is improved, but system complexity increases due to multiple voltage setpoints and phase adjustments
Solution Approach 1:
The system controls plasma characteristics by dynamically changing multiple parameters of the pulsed RF signal including voltage setpoints for different states (Von, Voff, Vintermediate), pulse widths, and phase relationships. By systematically varying these parameters, the patent achieves precise control over etch rate, anisotropy, and selectivity without requiring complex additional hardware
Solution Approach 2:
The RF signal is divided into multiple distinct states within each pulse cycle, with each state having its own optimized voltage setpoint and duration. This segmentation allows independent optimization of different plasma functions (ionization, etching, passivation) occurring at different moments in the pulse cycle, achieving high precision control through temporal division
3Reliability
If edge ring wear is compensated by adjusting voltage setpoints, then plasma sheath consistency is maintained, but etch rate uniformity across the wafer deteriorates
Solution Approach 1:
The patent applies different voltage setpoints and phase adjustments to different temporal states of the RF pulse rather than uniformly across the entire cycle. By optimizing parameters for specific states (e.g., higher voltage during on-state for sheath maintenance, adjusted voltage during intermediate states for uniformity), the system achieves local optimization that simultaneously maintains sheath consistency and etch rate uniformity across the wafer surface
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 approach enhances radial uniformity and maintains plasma sheath levels, reducing etch rate and feature profile variations, thereby improving the consistency and quality of semiconductor wafer processing.
Implementation Method 1
The plasma can be generated using specific reactant gases that will cause constituents of the plasma to interact with the material(s) to be removed/modified from the semiconductor wafer, without significantly interacting with other materials on the wafer that are not to be removed/modified. The plasma is generated by using radiofrequency signals to energize the specific reactant gases.
Implementation Method 2
applying RF power from a second generator to an edge electrode that surrounds the ESC and is disposed below an edge ring that surrounds the ESC, the RF power from the second generator defining a second multi-state pulsed RF signal having a first state and a second state, wherein for each state of the second multi-state pulsed RF signal, the second generator automatically introduces a phase adjustment to substantially match phase with a corresponding state of the first multi-state pulsed RF signal
Implementation Method 3
adjusting a voltage setpoint for the second state of the second multi-state pulsed RF signal to tune the phase adjustment to a target phase adjustment setting
Implementation Method 4
the target phase adjustment setting, which facilitates the voltage setpoint to be in the middle portion of the allowed range for the voltage setpoint, remains substantially the same for changes in a capacitance of a match circuit through which the RF power from the second generator is applied to the edge electrode
Data Source
AI summary
Method for tuning a voltage setpoint for a multi-state pulsed RF signal in a plasma processing system, including: applying RF power from a first generator to an ESC, the RF power from the first generator defining a first multi-state pulsed RF signal; applying RF power from a second generator to an edge electrode that surrounds the ESC and is disposed below an edge ring that surrounds the ESC, the RF power from the second generator defining a second multi-state pulsed RF signal having a first state and a second state, wherein for each state of the second multi-state pulsed RF signal, the second generator automatically introduces a phase adjustment to substantially match phase with a corresponding state of the first multi-state pulsed RF signal; adjusting a voltage setpoint for the second state of the second multi-state pulsed RF signal to tune the phase adjustment to a target phase adjustment setting.