Active Radial Etch Uniformity Control via Harmonic RF Phase Adjustment
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Solution Overview
Problem
Plasma etchers face challenges in achieving radial etch uniformity due to standing waves caused by high-order harmonics, which are difficult to control with conventional adjustments in process parameters like RF power ratios and gas pressures.
Innovation Solution
The introduction of additional RF power sources that generate phase-adjustable high RF harmonic power signals, optimized for power, frequency, and phase, to control the shape of electromagnetic waves and plasma density within the plasma chamber, thereby adjusting etch rate uniformity across the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional RF power sources generating high RF harmonic power signals are introduced, then radial etch uniformity is improved, but device complexity increases
Solution Approach 1:
The RF power generation is segmented into multiple independent RF power sources, each generating specific harmonic frequencies (fundamental, 2nd harmonic, 3rd harmonic, etc.). Each RF power source operates independently to provide phase-adjustable signals at different frequencies, allowing precise control over plasma harmonics without requiring a complete system redesign.
Solution Approach 2:
The additional RF power sources serve multiple functions simultaneously: they generate high RF harmonic power signals, provide phase adjustment capability, control electromagnetic wave shapes, and regulate plasma density. This multi-functionality addresses the technical contradiction by consolidating several control functions into integrated RF power source units.
2Object-affected harmful factors
If process parameters such as RF power ratios and gas pressures are adjusted, then standing wave effects are reduced, but control effectiveness is limited
Solution Approach 1:
The invention changes the fundamental parameters of the RF power sources by introducing multiple independent sources operating at different harmonic frequencies (2nd harmonic, 3rd harmonic, etc.) with phase adjustment capabilities. This allows direct control over the parameters that generate standing waves, rather than indirectly adjusting process parameters like gas pressure or fundamental RF power ratios.
Solution Approach 2:
The invention converts the harmful standing wave effects into beneficial control mechanisms by using additional RF power sources to generate controlled harmonic signals. These harmonics, which previously caused non-uniformities, are now used intentionally to cancel or reduce standing wave patterns through phase adjustment, transforming a harmful phenomenon into a useful control tool.
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 effectively enhances radial etch uniformity by controlling plasma harmonics, reducing standing wave effects and improving the consistency of etching across the wafer surface.
Implementation Method 1
The additional RF power sources provide high RF harmonic power signals that are phase adjustable or phase locked with respect to a fundamental frequency
Implementation Method 2
Power magnitudes, frequencies, and phases of the high RF harmonic power signals are optimized to reduce standing wave effects in the plasma
Implementation Method 3
The additional RF sources generate RF power at two times the fundamental driving frequency, three times the fundamental driving frequency, four times the fundamental driving frequency, and so on, with phases that are adjustable with respect to the phase associated with the fundamental driving frequency
Implementation Method 4
By controlling the phases of the additional RF sources and controlling power levels of the additional RF sources, shapes of electromagnetic waves within the plasma, a radial shape of a plasma sheath of the plasma, and a radial plasma density at the surface of the wafer are controlled
Data Source
AI summary
Systems and methods for active control of radial etch uniformity are described. One of the methods includes generating a radio frequency (RF) signal having a fundamental frequency and generating another RF signal having a harmonic frequency. The harmonic frequency, or a phase, or a parameter level, or a combination thereof of the other RF signal are controlled to control harmonics of RF plasma sheath within a plasma chamber to achieve radial etch uniformity.