Pulsed Multi-RF Plasma Control for Anisotropic Etching
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Solution Overview
Problem
Current plasma processing technologies face inefficiencies in controlling ion energy and plasma parameters, particularly in generating high-aspect-ratio deep holes and achieving vertical ion incidence angles, due to limitations in radio-frequency power supply configurations.
Innovation Solution
A plasma processing apparatus utilizing three radio-frequency power generators producing pulsed signals of different frequencies and power levels, with non-overlapping periods to control plasma parameters and ion energy, ensuring efficient substrate processing and high anisotropy etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple radio-frequency power supplies with different frequencies are used to control plasma parameters, then etching precision and anisotropy are improved, but device complexity increases
Solution Approach 1:
The plasma processing system is segmented into multiple independent radio-frequency power supply units, each operating at different frequencies (e.g., 13.56 MHz for main plasma generation, 27.12 MHz for ion control). This segmentation allows precise independent control of plasma density and ion energy, achieving high etching precision while managing complexity through modular architecture
Solution Approach 2:
The system changes multiple parameters simultaneously by employing radio-frequency power supplies with different frequencies and duty cycles. By adjusting frequency ratios, power levels, and pulse widths of each RF source, the system optimizes plasma parameters (electron temperature, ion flux, radical density) to achieve superior etching anisotropy and precision
2Manufacturing precision
If pulsed RF signals with multiple periods are used to control ion energy, then ion incidence angle control is improved, but process time increases
Solution Approach 1:
The system employs periodic pulsed RF signals with multiple periods where different power levels are applied in sequence. High-power pulses generate plasma and accelerate ions, while low-power or zero-power periods allow plasma relaxation and byproduct removal. This periodic modulation enables precise control of ion incidence angles by timing the high-power phases to coincide with substrate processing stages
Solution Approach 2:
The multi-period pulsed RF scheme maintains continuous useful action by overlapping processing cycles and optimizing duty cycles. While one RF source is in its high-power phase for ion acceleration, another source operates in complementary phases, ensuring uninterrupted plasma generation and ion supply, thereby minimizing idle time and reducing overall process time
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
The apparatus improves etching accuracy and anisotropy by finely controlling ion incidence angles and plasma parameters, enhancing the efficiency and precision of substrate processing.
Implementation Method 1
a first RF generator coupled to the first matching circuit, and configured to generate a first RF pulsed signal including a plurality of first pulse cycles
Implementation Method 2
a second RF generator coupled to the second matching circuit, and configured to generate a second RF pulsed signal including a plurality of second pulse cycles, the second RF pulsed signal having a frequency lower than a frequency of the first RF pulsed signal
Implementation Method 3
a third RF generator coupled to the second matching circuit, and configured to generate a third RF pulsed signal including a plurality of third pulse cycles, the third RF pulsed signal having a frequency lower than the frequency of the second RF pulsed signal
Data Source
AI summary
An RF system includes: a first RF generator configured to generate a first RF pulsed signal including a plurality of first pulse cycles, each first pulse cycle including a first period, a second period, and a third period; a second RF generator configured to generate a second RF pulsed signal including a plurality of second pulse cycles, each second pulse cycle including a fourth period and a fifth period; and a third RF generator configured to generate a third RF pulsed signal including a plurality of third pulse cycles, each third pulse cycle including a sixth period and a seventh period.