Post-Etch Plasma Treatment for Smooth High-Aspect-Ratio Sidewalls
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Solution Overview
Problem
High aspect ratio etching of semiconductor stacks results in issues such as twisting, non-circularity, aspect-ratio dependent etch rate, bowing, insufficient mask selectivity, and low etch rate, leading to device failure, reduced density, and performance, with existing methods exacerbating these problems rather than addressing them.
Innovation Solution
A method involving a cooled substrate support and specific etch gas plasma with controlled ion acceleration, followed by a post etch plasma treatment to reduce sidewall roughness and contaminants, is employed to etch high aspect ratio features with improved selectivity and smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If high aspect ratio etching is performed to increase device density and depth, then device capacity and integration are improved, but sidewall roughness and contamination increase leading to device failure
Solution Approach 1:
The patent changes the chemical parameters of the etch gas composition by adding phosphorous-containing components (PH3, PCl3, or PBr3) to the halogen-containing etch gas. This chemical parameter change modifies the etching mechanism to reduce sidewall roughness and contamination while maintaining high aspect ratio etching capability, directly resolving the contradiction between etch depth and sidewall quality
Solution Approach 2:
The patent uses a composite gas mixture combining halogen-containing components (CF4, SF6, NF3) with phosphorous-containing components (PH3, PCl3, PBr3). This composite approach creates a synergistic effect where the halogen provides etching capability and the phosphorous component passivates sidewalls and reduces roughness, simultaneously achieving deep etching with smooth sidewalls
2Device complexity
If conventional etching methods are used to maintain simple process flow, then manufacturing complexity is reduced, but mask selectivity becomes insufficient leading to mask damage
Solution Approach 1:
The patent modifies the chemical composition parameters of the etch gas by incorporating phosphorous-containing components. This change alters the etching chemistry to provide better mask protection through phosphorous-based passivation, improving mask selectivity without requiring additional process steps or complex equipment modifications
3Productivity
If etching proceeds at high speed to increase productivity, then manufacturing throughput is improved, but etch rate becomes aspect-ratio dependent leading to tapered features
Solution Approach 1:
The patent changes the chemical reactivity parameters by adding phosphorous-containing gas components to the etch mixture. This modification creates a more uniform etch rate throughout the high aspect ratio feature depth, preventing the aspect-ratio dependent etching that causes tapering, while maintaining high overall productivity
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 method achieves deeper etching with reduced sidewall roughness and contamination, enhancing device reliability and performance by minimizing twisting, non-circularity, and maintaining etch rate without compromising mask integrity.
Implementation Method 1
A plasma is generated from the etch gas
Implementation Method 2
A bias is provided to accelerate ions from the plasma to the stack
Implementation Method 3
A substrate support for supporting the stack in an etch chamber is cooled to a temperature below 0° C.
Data Source
AI summary
A method of forming features in stack with a silicon containing layer below a mask is provided. Features are etched into the stack. A post etch plasma treatment is provided to reduce surface roughness of sidewalls of the features.