Reverse RF Pulsing in Plasma Etching for ARDE Control
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Solution Overview
Problem
Existing plasma processing technologies face challenges with micro-loading and aspect ratio dependent etching (ARDE) during semiconductor fabrication, leading to reduced etch rates and selectivity, particularly in features with varying dimensions.
Innovation Solution
Implementing reverse synchronization between bias and source radio frequency (RF) signals, where the bias RF signal is pulsed with opposite phases to the source RF signal, reducing electron temperature during the off period to enhance ion directionality and plasma modulation, thereby mitigating micro-loading and improving etch selectivity and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous RF signals are used for plasma etching, then etch rate is maintained, but micro-loading and ARDE effects worsen due to sustained plasma presence
Solution Approach 1:
The patent applies periodic pulsed RF signaling where the source RF signal and bias RF signal are pulsed in opposite phases. During source RF on-periods, plasma is generated for etching; during bias RF on-periods, plasma is suppressed or reduced. This periodic modulation allows the etch process to proceed in controlled intervals while preventing continuous plasma exposure that causes micro-loading and ARDE effects, thereby maintaining etch rate while improving etch uniformity across features of varying dimensions.
2Productivity
If high plasma density is maintained for high etch rate, then productivity increases, but ion directionality decreases leading to poor anisotropy
Solution Approach 1:
The patent utilizes periodic pulsed RF signaling with opposite phase synchronization between source and bias RF signals. During source RF on-periods with high plasma density, etching proceeds at high rate. During bias RF on-periods, the enhanced bias power improves ion directionality and verticality. This temporal separation allows the system to achieve both high etch rate and good ion directionality/anisotropy by alternating between plasma generation phases and bias-enhanced ion directionality phases.
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 reverse pulsing technique enhances etch rate, selectivity, and uniformity by reducing electron temperature and increasing ion directionality towards vertical features, effectively addressing micro-loading and ARDE issues.
Implementation Method 1
A radio frequency (RF) signal is provided to a plasma chamber in which a wafer is located. Also, one or more gases are supplied to the plasma chamber and upon reception of the RF signal, plasma is generated within the plasma chamber.
Data Source
AI summary
Systems and methods for reverse pulsing are described. One of the methods includes receiving a digital signal having a first state and a second state. The method further includes generating a transformer coupled plasma (TCP) radio frequency (RF) pulsed signal having a high state when the digital signal is in the first state and having a low state when the digital signal is in the second state. The method includes providing the TCP RF pulsed signal to one or more coils of a plasma chamber, generating a bias RF pulsed signal having a low state when the digital signal is in the first state and having a high state when the digital signal is in the second state, and providing the bias RF pulsed signal to a chuck of the plasma chamber.