Amorphous Silicon Wet Etching After UV Surface Reforming
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Solution Overview
Problem
The etch rate of amorphous silicon layers during wet etching is significantly lower due to alterations caused by oxygen or carbon introduction during plasma etching, leading to incomplete pattern formation in semiconductor substrates.
Innovation Solution
A substrate processing method involving ultraviolet irradiation of the altered amorphous silicon layer to break Si—O and Si—C bonds, followed by wet etching with a chemical solution, specifically using a fluorocarbon and oxygen plasma etched coating film, to efficiently remove the intermediate pattern while preserving the sidewalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching is performed on the coating film to form sidewalls, then the pattern formation is enabled, but the upper face of the amorphous silicon layer is altered by oxygen or carbon introduction, causing a significant decrease in wet etch rate
Solution Approach 1:
The patent applies preliminary action by performing ultraviolet irradiation on the amorphous silicon layer before wet etching to remove the altered layer formed during plasma etching. This preliminary treatment restores the surface to a state that accepts wet etching, thereby resolving the contradiction between achieving precise pattern formation through plasma etching and maintaining high wet etch rate for intermediate pattern removal.
2Ease of manufacture
If wet etching is used to remove the intermediate pattern, then the process is simpler, but the etch rate becomes considerably lower due to the altered layer from plasma etching
Solution Approach 1:
The patent introduces ultraviolet irradiation as a preliminary step before wet etching to eliminate the harmful altered layer. This enables the use of wet etching (which is easier and more selective) while restoring the etch rate to acceptable levels, thus resolving the contradiction between ease of manufacture and productivity.
3Device complexity
If the altered layer is not removed, then the process steps are reduced, but polymer residues remain between sidewalls causing failure in downstream steps
Solution Approach 1:
The patent introduces ultraviolet irradiation as an intermediary treatment between plasma etching and wet etching. This intermediary step removes the altered layer that would otherwise cause reliability issues in downstream processes, while not significantly increasing overall process complexity since the irradiation can be integrated into existing equipment.
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 etch rate of amorphous silicon layers, allowing for effective wet etching and maintaining the integrity of the sidewalls, thus improving the pattern formation process in semiconductor substrates.
Implementation Method 1
irradiating the altered layer with an ultraviolet ray to reform the altered layer into a reformed layer
Implementation Method 2
supplying a chemical solution to the amorphous silicon layer having the reformed layer on the surface to perform wet etching on the amorphous silicon layer
Implementation Method 3
the dry etching includes etching a coating film formed on the surface of the amorphous silicon layer, using plasma generated from a fluorocarbon gas and an oxygen gas
Data Source
AI summary
A substrate processing method includes an operation for holding a substrate in a horizontal position, the substrate including an amorphous silicon layer having a surface on which an altered layer derived from dry etching is formed, an operation for irradiating the altered layer with ultraviolet rays to reform the altered layer into a reformed layer, and an operation for supplying a chemical solution to the amorphous silicon layer having the reformed layer on the surface to perform wet etching on the amorphous silicon layer. This improves the efficiency of the wet etching on the amorphous silicon layer.