Two-Step Etching for Smooth Sidewalls in Semiconductor Trenches
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Solution Overview
Problem
Existing etching methods for creating through-vias and trenches in semiconductor applications often result in features with rough sidewalls, leading to ineffective filling and reduced yield, and are impractical for high-volume manufacturing due to high costs associated with plasma etching and slow etch rates.
Innovation Solution
A two-step etching process involving a main etch process with continuously supplied chlorine-containing gas to form features and a post etch process with pulsed fluorine-containing gas to smooth sidewalls, using a hard mask layer on a substrate with alternately formed first and second layers, enabling fast etching and sidewall smoothing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing etching methods are used to create through-vias and trenches, then the etching process can be performed, but the sidewalls become rough leading to ineffective filling and reduced yield
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas chemistries: a first etch step using a fluorocarbon-based gas to create initial features, followed by a second etch step using a different gas mixture to smooth the sidewalls. This segmentation allows each step to optimize for its specific function, achieving both through-via formation and smooth sidewalls that enable effective filling
Solution Approach 2:
The patent changes etching parameters including gas composition (switching between fluorocarbon-based and other etching gases), gas flow rates, and process conditions between etching steps. These parameter changes enable transition from a high-etch-rate mode to a sidewall-smoothing mode, resolving the contradiction between achieving deep etches and maintaining smooth sidewalls
2Productivity
If plasma etching is performed with high etch rate to reduce manufacturing time, then productivity increases, but sidewall roughness increases leading to reduced reliability
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas chemistries: a first etch step using a fluorocarbon-based gas to create initial features, followed by a second etch step using a different gas mixture to smooth the sidewalls. This segmentation allows each step to optimize for its specific function, achieving both through-via formation and smooth sidewalls that enable effective filling
Solution Approach 2:
The patent employs periodic alternation between different etching gas compositions and process conditions. High-power plasma etching is performed periodically to achieve deep etches at high speed, followed by periodic sidewall smoothing steps using modified gas chemistry. This periodic action resolves the contradiction by achieving both high productivity and smooth sidewalls through time-separated operations
3Device complexity
If conventional etching methods are used to form features, then the process is simple, but the sidewalls become rough requiring additional processing steps
Solution Approach 1:
The patent merges the feature formation and sidewall smoothing functions into a single integrated etching process sequence. By combining multiple etching steps with different gas chemistries into one continuous process flow within the same reactor, the method achieves smooth sidewalls without requiring separate processing equipment or complex additional steps, thus maintaining process simplicity while improving manufacturing precision
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 method allows for the formation of features with smooth sidewalls at a high overall etch rate, improving yield and reliability by combining fast etching with effective sidewall smoothing, suitable for high-volume manufacturing.
Implementation Method 1
performing a first etch process to form features in the material layer through the hard mask layer by supplying a first etching gas, and performing a second etch process to smooth sidewalls of the features formed in the material layer by suppling a second etching gas
Data Source
AI summary
A method for patterning a material layer on a substrate includes forming a hard mask layer on a material layer disposed on a substrate, the material layer comprising a plurality of first layers and a plurality of second layers alternately formed over the substrate, performing a first etch process to form features in the material layer through the hard mask layer by supplying a first etching gas, and performing a second etch process to smooth sidewalls of the features formed in the material layer by suppling a second etching gas. The first etching gas is supplied continuously and the second etching gas is pulsed.