Polysilicon Etching via Fluoromethane Plasma
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Solution Overview
Problem
Existing methods for etching polycrystalline silicon films on semiconductor substrates result in varying etching results due to differences in pattern density between dense and sparse patterns, leading to inconsistencies in semiconductor devices like NAND flash memory.
Innovation Solution
A method involving the use of a mask layer on a polycrystalline silicon film with a temperature-controlled etching chamber, employing a mixture of hydrogen bromide and fluoromethane-based gases to generate plasma, which reduces etching variations by controlling the taper angles of both dense and sparse patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If RIE is performed with a mixture of hydrogen bromide and additive gases to etch polycrystalline silicon film, then etching can be performed on the film, but varying etching results occur due to pattern density variation between dense and sparse patterns
Solution Approach 1:
The patent changes the chemical parameters of the etching process by replacing traditional additive gases (chlorine, oxygen, nitrogen) with fluoromethane-based gas. This parameter change modifies the etching chemistry to produce volatile silicon fluoride compounds that can be easily removed, thereby achieving uniform etching results across both dense and sparse patterns without the deposit accumulation problems that occur with conventional gas mixtures
Solution Approach 2:
The patent substitutes the chemical mechanism of etching by replacing the hydrogen bromide-based chemistry with a fluoromethane-based chemistry. This substitution changes the reaction products from silicon bromide (which causes deposits) to silicon fluoride (which is volatile and easily removed), thereby eliminating the pattern density-dependent variation in etching results
2Productivity
If etching is performed simultaneously on densely patterned memory cell region and sparsely patterned peripheral circuit region, then productivity is maintained, but deposit of silicon bromide causes variation in etching results
Solution Approach 1:
The patent changes the chemical parameters by using fluoromethane-based gas instead of traditional additive gases, which alters the etching reaction products to be volatile silicon fluoride compounds. This enables simultaneous etching of dense and sparse patterns without deposit formation, maintaining productivity while achieving consistent etching results across different pattern densities
Solution Approach 2:
The patent converts the potential harm of deposit formation during simultaneous etching into a benefit by using fluoromethane-based gas that produces volatile silicon fluoride. The volatility of the reaction products transforms what would be a harmful deposit into a beneficial easily-removed byproduct, enabling uniform etching across varying pattern densities
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 achieves consistent etching results across varying pattern densities, ensuring reduced variation in etch outcomes and improved processability, particularly in NAND flash memory devices with high aspect ratios.
Implementation Method 1
supplying an etching gas composed of a hydrogen bromide containing gas and a fluoromethane based gas into the chamber, and generating plasma in the chamber
Implementation Method 2
supplying an etching gas composed of a hydrogen bromide containing gas and a fluoromethane based gas into the chamber
Data Source
AI summary
A method of manufacturing a semiconductor device including forming a mask layer on a polycrystalline silicon film formed on a semiconductor substrate via an insulating film; forming a dense pattern and a sparse pattern on the mask layer to form a mask; etching the polycrystalline silicon film with the mask by controlling a temperature of the semiconductor substrate placed in an etching chamber at 50 degrees Celsius or higher, supplying an etching gas composed of a hydrogen bromide containing gas and a fluoromethane based gas into the chamber, and generating plasma in the chamber.