In Situ Fluorine Cleaning for Silicon Etch Byproduct Removal
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Solution Overview
Problem
The accumulation of bromine-containing byproducts during silicon etching in plasma processing chambers leads to clogging of narrow features, etch profile distortion, and limited etching depth at high aspect ratios, particularly at sub-10 nm scales, due to re-deposition on the substrate.
Innovation Solution
Incorporating an in situ chamber cleaning step using fluorine chemistry between etching steps to remove byproducts, where fluorine-containing gases like CF4 break down to release atomic fluorine, which reacts with bromine-containing byproducts to form removable silicon fluoride gas, preventing re-deposition and maintaining etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HBr is used as etchant gas for silicon etching, then etching capability is improved, but bromine-containing byproducts accumulate on chamber walls and re-deposit on substrate causing clogging and profile distortion
Solution Approach 1:
The patent introduces a fluorine-based plasma cleaning step that converts the harmful bromine-containing byproducts into volatile silicon fluoride gas that can be pumped away. The fluorine atoms react with the accumulated byproducts on chamber walls and substrate, transforming the clogging problem into a removable gaseous product, thereby eliminating the harmful effects while maintaining the etching capability of the HBr-based process
Solution Approach 2:
The patent implements a periodic cleaning cycle where fluorine-based plasma is introduced between etching steps or during etching interruptions. This periodic action removes accumulated byproducts before they can re-deposit and cause defects, allowing the system to maintain high etching productivity while periodically eliminating the harmful byproduct accumulation
2Length of moving object
If etching depth is increased for high aspect ratios, then more material is removed, but byproduct re-deposition increases causing clogging of narrow features
Solution Approach 1:
The patent introduces fluorine-based plasma as an intermediary cleaning step between etching operations. This intermediary action removes byproducts from chamber walls and substrate surfaces, preventing their re-deposition during subsequent etching steps. The fluorine acts as a mediator that clears the path for continued deep etching without compromising feature clarity or causing clogging in narrow structures
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 etching depth and aspect ratios, reduces post-etching defects, and prevents physical contact with neighboring gates by effectively removing byproducts, thereby improving the precision and reliability of silicon etching processes.
Implementation Method 1
a cleaning step based on fluorine chemistry, which is executed in between separate etch steps
Implementation Method 2
fluorine-containing gases like CF4 break down to release atomic fluorine, which reacts with bromine-containing byproducts to form removable silicon fluoride gas
Implementation Method 3
heating electrons to energies sufficient to sustain ionizing collisions
Implementation Method 4
heated electrons can have energy sufficient to sustain dissociative collisions
Data Source
AI summary
Techniques herein provide a chamber and substrate cleaning solution for etching and removing byproducts between separate etching steps. Such techniques include using a cleaning step based on fluorine chemistry, which is executed in between separate etch steps or divided etch steps. Such a technique can be executed in situ for improved efficiency. Other benefits include increasing etching depth/aspect ratios, and preventing post-etching defects including physical contact with neighboring gates, etc. Techniques herein are especially beneficial when applied to relatively small feature openings.