Selective Etch Chemistries for High Aspect Ratio Features
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Solution Overview
Problem
Conventional etching methods for integrated circuit fabrication result in bowed sidewalls and non-uniform openings due to polymer film deposition, leading to issues like tapering and parasitic capacitance, which affect the reliability and uniformity of the final product.
Innovation Solution
The use of etch chemistries comprising silicon, halide, carbon, and oxygen species, which are plasma-excited, to form passivating films on the sidewalls, reducing bowing and tapering by providing etch resistance and controlling the profile of etched openings, while also increasing etch selectivity and rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional dry etch chemistry with hydrofluorocarbons is used, then etching of silicon oxide can proceed, but polymer films deposit on sidewalls causing bowed sidewalls and non-uniform openings
Solution Approach 1:
The patent changes the chemical parameters of the etch chemistry by introducing silicon-containing compounds (such as silane or tetraethyl orthosilicate) combined with oxygen and fluorine sources. This chemical composition change enables formation of silicon oxide passivation layers that deposit more uniformly on sidewalls compared to conventional hydrofluorocarbon chemistries, thereby reducing bowing while maintaining etch rate
Solution Approach 2:
The patent employs a composite etch chemistry system combining silicon-containing compounds, oxygen, and fluorine sources. This composite approach creates a dual-function system where silicon oxide passivation layers protect sidewalls from excessive etching while the fluorine components enable continued etching of the silicon oxide layer, achieving both sidewall uniformity and productive etching
2Manufacturing precision
If polymer films are allowed to protect sidewalls from etching, then bowing is reduced, but the films can block etchant flow causing tapering and non-uniform openings
Solution Approach 1:
The patent modifies the deposition parameters of the passivation layer by controlling the silicon-to-oxygen ratio and using plasma-enhanced chemical vapor deposition conditions. This results in formation of porous or less dense silicon oxide films that provide sidewall protection while remaining permeable to etchant species, preventing tapering while maintaining sidewall straightness
Solution Approach 2:
The silicon oxide passivation films formed by the patent's etch chemistry have a porous structure that allows etchant species to penetrate through the film and reach the sidewall surface. This porosity enables the film to provide mechanical protection against bowing while maintaining etchant accessibility, thus preventing tapering
3Manufacturing precision
If thicker passivation films are formed to protect sidewalls, then bowing decreases, but the films may plug the openings and block etchant flow
Solution Approach 1:
The patent controls the thickness and density parameters of the passivation film through precise control of silicon precursor flow rates, plasma power, and pressure conditions. This results in formation of thin (5-50 nm), low-density silicon oxide films that provide adequate sidewall protection while remaining sufficiently thin and porous to allow etchant penetration, preventing both bowing and plugging
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 enables the formation of high aspect ratio openings with uniform, nearly vertical sidewalls, improved etch rates, and increased selectivity, reducing bowing and tapering, thus enhancing the reliability and uniformity of integrated circuit features.
Implementation Method 1
a dry etch in which the material is exposed to a directional plasma, in which excited species are directed to the material
Implementation Method 2
by physically sputtering away the material, due to bombardment by the excited species
Implementation Method 3
carbon from the hydrofluorocarbons of the etch chemistry can deposit and polymerize in the openings 50 during etching, thereby forming polymer films 60
Implementation Method 4
carbon from the hydrofluorocarbons of the etch chemistry can deposit and polymerize in the openings 50 during etching
Data Source
AI summary
An interlevel dielectric layer, such as a silicon oxide layer, is selectively etched using a plasma etch chemistry including a silicon species and a halide species and also preferably a carbon species and an oxygen species. The silicon species can be generated from a silicon compound, such as SixMyHz, where “Si” is silicon, “M” is one or more halogens, “H” is hydrogen and x≧1, y≧0 and z≧0. The carbon species can be generated from a carbon compound, such as CαMβHγ, where “C” is carbon, “M” is one or more halogens, “H” is hydrogen, and α≧1, β≧0 and γ≧0. The oxygen species can be generated from an oxygen compound, such as O2, which can react with carbon to form a volatile compound.