Multi-level Pulsing RF Bias for Plasma Etch Angular Spread
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Solution Overview
Problem
Current plasma etching technologies face challenges in achieving low angular spread of ions, which affects etch rate and mask selectivity, as high RF bias increases mask erosion and does not effectively reduce angular spread due to thick plasma sheath.
Innovation Solution
Implementing multi-level pulsing of RF signals with varying voltage and frequency levels, synchronized with DC pulsing, to reduce the angular spread of ions, thereby enhancing etch rate and mask selectivity by optimizing voltage and frequency transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high RF bias is applied to generate high energy ions, then etch rate is improved, but mask erosion increases and angular spread is not effectively reduced due to thick plasma sheath
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) in a controlled sequence. This periodic action allows ions to be accelerated to high energies during the high power phase to achieve vertical directionality and low angular spread, while the low power phase reduces overall mask erosion by limiting continuous high energy exposure.
2Manufacturing precision
If high RF bias is applied to reduce angular spread, then ion directionality is improved, but mask erosion increases due to excessive energy
Solution Approach 1:
The patent dynamically adjusts the RF bias voltage amplitude between two distinct levels during the etching process. By transitioning between a first amplitude level (for reducing angular spread) and a second amplitude level (for controlling mask erosion), the system optimizes ion directionality while minimizing harmful effects. This dynamic parameter adjustment allows the process to achieve low angular spread without sustaining continuously high energy that would cause excessive mask erosion.
3Manufacturing precision
If multiple voltage levels are applied to reduce angular spread, then ion directionality is improved, but process complexity increases
Solution Approach 1:
The patent segments the RF bias voltage into two distinct amplitude levels (first and second levels) that are applied in a pulsed sequence. This segmentation simplifies the control complexity by using only two discrete voltage states rather than continuous or multi-level adjustments. The segmented approach maintains effectiveness in reducing angular spread while keeping the voltage control system manageable through binary amplitude switching.
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 multi-level pulsing approach significantly reduces the angular spread of ions, increasing etch rate by up to 60% and improving mask selectivity by 20%, while reducing critical dimensions and mask erosion.
Implementation Method 1
The RF generator generates a radio frequency waveform that is supplied to the impedance matching circuit
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
Implementation Method 3
Voltage magnitudes of the low voltage level apply a voltage boost to the low energy ions during the high voltage level. The high electric field increases velocity and energy of the low energy ions
Implementation Method 4
The high electric field increases velocity and energy of the low energy ions without substantially increasing the high voltage level to increase directionality of the low energy ions or reducing the angular spread
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 RF signal is applied to a substrate support via a match. 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. In addition, a direct current (DC) parameter is applied to the substrate support or another RF signal is applied to an upper electrode. The parameter and the frequency of the RF signal applied to the substrate support are simultaneously pulsed with the DC parameter or the RF signal applied to the upper electrode to increase a rate of processing a wafer, to increase mask selectivity, and to reduce angular spread of ions within a plasma chamber.