High-Aspect-Ratio Plasma Etching With Metal Additive Sidewall Protection
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Solution Overview
Problem
Semiconductor fabrication processes face challenges in consistently etching mixed material stacks with multiple alternating layers, leading to issues such as undercutting, uneven etching, and feature profile distortion, particularly in deep features with varying sizes and shapes.
Innovation Solution
A method involving exposure to etching gases followed by a second plasma with a metal-containing additive gas at reduced power, pressure, and temperature, which helps maintain feature shape and size by modulating plasma power and using inert gases for dilution, thereby reducing crystallized metal byproduct formation and improving sidewall etching uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching is used on mixed material stacks, then etching can be performed, but undercutting and feature profile distortion occur
Solution Approach 1:
The patent applies parameter changes by modulating plasma power between high and low states during the etching process. High plasma power is used initially to achieve adequate etching rates, then power is reduced to a low state to minimize sidewall damage and prevent undercutting. This dynamic parameter adjustment resolves the contradiction between achieving sufficient etching and maintaining feature profile integrity.
Solution Approach 2:
The patent implements periodic action through cyclic modulation of plasma power and gas flow. The process alternates between high-power etching phases and low-power maintenance phases, creating a periodic pattern that allows aggressive etching when needed while protecting sidewalls during other phases. This periodic modulation prevents cumulative sidewall damage that would lead to undercutting.
2Productivity
If high plasma power is used for etching, then etching rate is improved, but sidewall damage and chipping increase
Solution Approach 1:
The patent applies dynamics by making the plasma power a dynamic variable rather than a constant parameter. The system continuously adjusts plasma power between high and low states based on the etching progress and sidewall condition. This dynamic control allows the process to achieve high etching rates when sidewalls are intact while preventing chipping by reducing power when sidewalls become vulnerable.
Solution Approach 2:
The patent implements beforehand cushioning by introducing a protective low-power plasma phase before significant sidewall damage can occur. This low-power phase acts as a cushion that prevents the accumulation of sidewall stress and damage that would lead to chipping, allowing the process to sustain high-power etching cycles without compromising sidewall integrity.
3Quantity of substance
If metal-containing additive gas is used at high plasma power, then metal deposition occurs, but crystallized metal byproduct formation increases
Solution Approach 1:
The patent applies parameter changes by controlling plasma power to remain low during metal-containing gas exposure. This low-power condition prevents the thermal energy necessary for crystallization while still allowing metal deposition to occur. The parameter change from high to low power during metal gas introduction resolves the contradiction between achieving metal deposition and avoiding crystallized byproducts.
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 enhances the etching of mixed features by reducing pattern loading effects, maintaining feature profiles, and minimizing chipping and distortion, resulting in improved uniformity and structural integrity across the substrate.
Implementation Method 1
igniting a first plasma at a first plasma power to partially etch a feature into the mixed material stack
Implementation Method 2
a plasma generator
Data Source
AI summary
Methods and apparatus for etching high aspect ratio features in substrates having mixed material stacks are provided herein. Methods involve using low plasma power, high chamber pressure, and/or low temperature while exposing the substrate to a metal-containing additive gas during etching using a fluorocarbon gas.