RF Bias And Frequency Pulsing for Low-Angular-Spread Plasma Etching
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Solution Overview
Problem
Current plasma etching technologies face challenges in achieving high aspect ratio etching with low angular spread, leading to increased mask erosion and reduced etch rates due to high plasma sheath thickness and high energy ions.
Innovation Solution
Implementing multi-level parameter and frequency pulsing of RF signals, where the RF bias is increased at low frequencies to generate both high and low energy ions with reduced angular spread, using multiple voltage and frequency levels to control the plasma sheath and ion energy, thereby optimizing the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If RF bias is increased to achieve high aspect ratio etching, then etching capability is improved, but mask erosion increases
Solution Approach 1:
The patent applies periodic pulsing of RF bias voltage with multiple amplitude levels during the etching process. The RF bias is pulsed between a first amplitude level (lower power) and a second amplitude level (higher power), creating periodic action that allows high aspect ratio etching while reducing cumulative mask erosion compared to continuous high power application.
Solution Approach 2:
The patent changes the parameter of RF bias voltage amplitude dynamically during the etching process by implementing multi-level pulsing. The system transitions between different voltage amplitude levels (first amplitude level and second amplitude level) to optimize both etching rate and mask protection, rather than maintaining a constant high bias voltage.
2Manufacturing precision
If RF bias is increased to reduce plasma sheath thickness, then angular spread is reduced, but ion energy increases causing mask damage
Solution Approach 1:
The patent uses periodic pulsing of RF bias with varying amplitudes to control plasma sheath dynamics. During low amplitude phases, ion energy is reduced protecting the mask, while during high amplitude phases, the plasma sheath thickness is reduced to decrease angular spread. This temporal separation of functions resolves the contradiction between precision and damage prevention.
Solution Approach 2:
The patent makes the RF bias voltage dynamic by implementing multi-level pulsing rather than maintaining a static high voltage. The system dynamically adjusts between first and second amplitude levels, allowing the plasma sheath to respond in real-time and enabling both low angular spread and controlled ion energy at different moments in the pulsing cycle.
3Productivity
If continuous high RF bias is applied to improve etch rate, then productivity increases, but low energy ion quality deteriorates
Solution Approach 1:
The patent implements periodic pulsing where the RF bias alternates between first and second amplitude levels. During the lower amplitude phases, low energy ions are generated with high quality for precise etching, while during higher amplitude phases, overall etching productivity is enhanced. This periodic alternation maintains both ion quality and productivity.
Solution Approach 2:
The system dynamically modulates the RF bias voltage between multiple amplitude levels, creating a time-varying electric field that produces both low energy ions (during lower amplitude phases) and maintains high etch rates (during higher amplitude phases). This dynamic control resolves the contradiction between productivity and ion quality.
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 reduces the angular spread of low energy ions, enhancing mask selectivity and etch rates while maintaining high aspect ratio etching, resulting in improved processing efficiency and reduced mask erosion.
Implementation Method 1
A plasma tool includes a radio frequency (RF) generator, and impedance matching circuit, and a plasma chamber. The RF generator generates a radio frequency waveform that is supplied to the impedance matching circuit. The impedance matching circuit receives the radio frequency waveform to output a radio frequency signal
Implementation Method 2
A wafer is processed within the plasma chamber by plasma generated when the radio frequency signal is supplied in conjunction with a process gas. For example, the wafer is etched within the plasma chamber pursuant to the radio frequency signal
Implementation Method 3
To generate ions, such as both high energy and low energy ions, a radio frequency (RF) bias is increased at low frequency, such as 1 megahertz (MHz). The RF bias has a continuous waveform
Data Source
AI summary
Systems and methods for multi-level pulsing of a parameter and multi-level pulsing of a frequency of a radio frequency (RF) signal are described. The parameter is pulsed from a low level to a high level while the frequency is pulsed from a low level to a high level. The parameter and the frequency are simultaneously pulsed to increase a rate of processing a wafer, to increase mask selectivity, and to reduce angular spread of ions within a plasma chamber.