Fluoro-Dithiethane Etching for Silicon-Carbon Selectivity
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Solution Overview
Problem
The dry etching process in semiconductor manufacturing requires improved etching selectivity, particularly the ratio of the etching rate of silicon materials to carbon materials, to meet the demands of miniaturization and three-dimensional semiconductor device development.
Innovation Solution
An etching method using an etching gas containing fluoro-dithiethane (CxFyS2) with specific molecular ranges and controlled metal impurity concentrations, along with optional second etching compounds and inert gases, to selectively etch silicon materials over carbon materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching gases are used to etch silicon materials, then etching rate is achieved, but etching selectivity between silicon material and carbon material mask deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas by introducing fluoro-dithiethane (C2F4S2) as a novel etching compound. This specific compound provides optimal balance between etching rate and selectivity by modifying the chemical reaction characteristics with silicon materials while minimizing interaction with carbon material masks, thereby resolving the contradiction between etching rate and selectivity
Solution Approach 2:
The patent uses a composite etching gas system comprising fluoro-dithiethane combined with inert gases (argon, helium) and optionally sulfur hexafluoride. This composite gas mixture synergistically enhances both etching rate and selectivity, where fluoro-dithiethane provides the primary etching action on silicon while the inert gases maintain plasma stability and the optional SF6 component further improves selectivity against carbon masks
2Productivity
If etching gas composition is optimized for high etching rate, then productivity improves, but manufacturing precision of etching selectivity deteriorates
Solution Approach 1:
The patent optimizes the concentration parameters of fluoro-dithiethane in the etching gas mixture, specifically setting it within 1-50% by volume. This parameter range maximizes etching rate while maintaining high selectivity, as the fluoro-dithiethane molecules provide sufficient reactive species for fast etching while their specific chemical structure prevents excessive attack on carbon masks
3Device complexity
If metal impurities are present in etching gas, then device complexity of purification is reduced, but manufacturing precision of etching characteristics deteriorates
Solution Approach 1:
The patent specifies stringent metal impurity concentration parameters in the etching gas, requiring total metal content to be 300 ppb by mass or less. This purity parameter ensures consistent and reproducible etching characteristics, preventing metal-induced variations in etching rate and selectivity, while the purification system is designed to achieve this threshold without excessive complexity
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
Achieves high etching selectivity of silicon materials to carbon materials, enabling the production of three-dimensionally integrated semiconductor elements with precise control over etching rates and selectivity.
Implementation Method 1
an etching step of bringing an etching gas containing an etching compound into contact with a member to be etched having an etching object subject to etching by the etching gas and a non-etching object not subject to etching by the etching gas and selectively etching the etching object over the non-etching object
Data Source
AI summary
An etching method includes an etching step of bringing an etching gas containing an etching compound into contact with a member to be etched (400) having an etching object (silicon material) and a non-etching object (carbon material) and selectively etching the etching object over the non-etching object. The etching compound is fluoro-dithiethane represented by Chemical Formula CxFyS2, wherein, in Chemical Formula, x is 2 or more and 6 or less and y is 4 or more and 12 or less. The etching gas contains or does not contain at least one type of metal among sodium, magnesium, aluminum, potassium, calcium, chromium, manganese, iron, cobalt, nickel, copper, and molybdenum, and, when the at least one type of metal is contained, the total concentration of all types of the contained metals is 300 ppb by mass or less.