Reverse RF Pulsing in Plasma Chambers for ARDE Reduction
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Solution Overview
Problem
Existing plasma etching processes face challenges with micro-loading and aspect ratio dependent etching (ARDE), leading to reduced etch rates and selectivity, particularly in semiconductor fabrication.
Innovation Solution
Implementing reverse pulsing of transformer coupled plasma (TCP) and bias RF signals, where the TCP RF signal is pulsed in an opposite phase to the bias RF signal, reducing electron temperature during the off period to enhance ion directionality and minimize micro-loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous RF signals are used for plasma etching, then plasma generation is maintained, but micro-loading and ARDE effects increase reducing etch rate and selectivity
Solution Approach 1:
The patent applies periodic pulsing of RF signals where the source RF signal and bias RF signal are pulsed in opposite phases. During the source RF pulse, plasma is generated; during the bias RF pulse, ion directionality is enhanced while electron temperature is reduced. This periodic alternating action maintains overall plasma generation while periodically reducing micro-loading effects, thereby improving etch uniformity across high aspect ratio structures without sacrificing etch rate.
2Manufacturing precision
If bias RF power is increased to improve ion directionality, then vertical etching is enhanced, but electron temperature increases reducing selectivity
Solution Approach 1:
The patent implements periodic pulsing where bias RF power is applied in alternating phases with source RF power. During bias RF pulses, ion directionality is enhanced for vertical etching. During source RF pulses, plasma generation is maintained while electron temperature is allowed to reset. This temporal separation prevents continuous electron heating while maintaining ion directionality benefits, thereby preserving selectivity.
Solution Approach 2:
The patent dynamically controls the timing and duration of source and bias RF pulses to optimize the balance between ion directionality and electron temperature. By adjusting pulse widths and duty cycles, the system adapts to maintain optimal conditions for both vertical etching and material selectivity throughout the etching process.
3Productivity
If source RF power is continuously applied to maintain plasma, then etching continues, but micro-loading effects accumulate reducing etch rate
Solution Approach 1:
The patent applies periodic pulsing of the source RF signal in alternating phases with the bias RF signal. During source RF pulses, plasma generation and etching occur. During bias RF pulses, ion directionality is enhanced and micro-loading effects are reduced. This periodic interruption and reset prevents micro-loading accumulation while maintaining overall etch rate through continued plasma generation during source RF 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
This approach improves etch rate, selectivity, and uniformity by reducing micro-loading and ARDE, allowing for higher aspect ratio etching with increased ion vertical directionality.
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.
Implementation Method 2
Reverse pulsing between bias and source RF signals is used to reduce electron temperature Te to enhance an influence of bias RF power to improve a directionality of ions towards the ESC.
Implementation Method 3
reducing electron temperature during the off period to enhance ion directionality and minimize micro-loading effects
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.