Organochloride Plasma Etching for High-Aspect-Ratio Profile Control
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Solution Overview
Problem
Existing etching processes for semiconductor devices face challenges in uniformly forming high aspect ratio recessed features with issues such as twisting, non-circularity, aspect-ratio dependent etch rate, bowing, insufficient mask selectivity, and low etch rate, which are often balanced with tradeoffs that exacerbate other problems.
Innovation Solution
A plasma-based etching method using a gas mixture of organochloride, carbon, and fluorine sources, controlled at low temperatures, with RF power pulsing and specific gas flow rates, to etch silicon-containing layers with improved selectivity and reduced bowing and twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching processes are used to etch high aspect ratio features, then etching can proceed at reasonable speeds, but the features exhibit twisting, non-circularity, and bowing due to aspect-ratio dependent etch rate
Solution Approach 1:
The patent changes the chemical parameters of the etching process by introducing organochloride sources (CCl4, CxHyClz) in combination with fluorocarbon and hydrogen sources. This chemical parameter change modifies the etch chemistry to reduce aspect-ratio dependent etch rate, thereby improving feature uniformity while maintaining etching productivity
Solution Approach 2:
The patent uses a composite gas mixture comprising organochloride, fluorocarbon, and hydrogen sources. This composite approach combines the benefits of different gas chemistries: organochloride for reduced ARDE and improved uniformity, fluorocarbon for protective film formation, and hydrogen for passivation, achieving both high etch rate and feature uniformity
2Productivity
If etching parameters are optimized for high etch rate, then productivity improves, but mask selectivity becomes insufficient leading to poor profile control
Solution Approach 1:
The composite gas mixture of organochloride, fluorocarbon, and hydrogen sources creates multiple protective films on the mask surface through different mechanisms. The fluorocarbon forms a protective polymer film while hydrogen provides atomic passivation, and organochloride contributes additional protective species. This multi-layer protective mechanism enhances mask selectivity while maintaining high etch rate
Solution Approach 2:
The patent modifies the chemical composition parameters by adding organochloride sources to the traditional fluorocarbon-hydrogen mixture. This parameter change alters the film formation kinetics and composition, creating a more robust protective film on the mask that maintains selectivity at higher etch rates
3Manufacturing precision
If process conditions are adjusted to reduce bowing and twisting, then feature uniformity improves, but etch rate decreases
Solution Approach 1:
The composite gas mixture provides synergistic effects where organochloride reduces aspect-ratio dependent etch rate and improves uniformity, while fluorocarbon and hydrogen maintain high etch rate through efficient silicon etching chemistry and protective film formation. The combination achieves both uniformity and productivity that neither gas could achieve alone
Solution Approach 2:
The patent changes the chemical composition by introducing organochloride sources which modify the etch chemistry to be less sensitive to aspect ratio effects. This parameter change in gas composition allows the process to maintain high etch rate while reducing the severity of bowing and twisting that would otherwise require slower processing
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 etching of high aspect ratio features with minimal twisting and bowing, maintaining circularity and sufficient etch rate, while providing sufficient mask selectivity and improved throughput.
Implementation Method 1
The etch gas is formed into a plasma. The stack is exposed to the plasma to etch recessed features into the stack.
Data Source
AI summary
A method of etching recessed features in stack with a silicon containing layer below a mask and over a wafer on a substrate support is provided. An etch gas comprising a carbon source, a fluorine source, and an organochloride source selected from the group consisting of carbon tetrachloride (CCI4), CxHyClz (where x>0 and z>0), and combinations thereof, is provided. The etch gas is formed into a plasma. The stack is exposed to the plasma to etch recessed features into the stack.