Selective Silicon Oxide Etching via Intermittent Gas Supply
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Solution Overview
Problem
Current methods for etching silicon nitride films in semiconductor manufacturing are challenged by the lack of selectivity between silicon oxide and silicon nitride films, leading to unwanted etching of silicon nitride films due to reaction with hydrogen fluoride and ammonia gases, especially when forming porous films at low temperatures.
Innovation Solution
A method and apparatus that intermittently supply a mixture of hydrogen fluoride and ammonia gases, along with a compound of nitrogen, hydrogen, and fluorine, under vacuum conditions to selectively etch silicon oxide films relative to silicon nitride films, utilizing a controlled gas supply and exposure pattern to minimize reaction with the silicon nitride films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen fluoride gas and ammonia gas are supplied to etch silicon oxide film, then etching of silicon oxide film is achieved, but silicon nitride film also reacts and is etched
Solution Approach 1:
The patent applies periodic action by intermittently supplying the processing gas (hydrogen fluoride and ammonia) to the substrate in multiple cycles rather than continuously. This allows the etching process to be performed in pulses, creating conditions that favor selective removal of silicon oxide while minimizing reaction with silicon nitride film.
Solution Approach 2:
The patent changes process parameters including gas supply timing (intermittent vs continuous), pressure conditions (vacuum atmosphere), and temperature control to achieve high selectivity. By adjusting these parameters, the etching rate of silicon oxide is enhanced while the reaction with silicon nitride is suppressed.
2Object-affected harmful factors
If silicon nitride film is formed at low temperature to suppress substrate damage, then substrate damage is reduced, but the film becomes porous and more prone to etching
Solution Approach 1:
The patent changes the process parameters of gas supply (intermittent mode) and pressure (vacuum conditions) to compensate for the porous structure of low-temperature silicon nitride film. These parameter changes create an etching environment that is selective to silicon oxide even when the silicon nitride film has increased etch susceptibility due to porosity.
Solution Approach 2:
By using intermittent gas supply in multiple cycles, the patent creates periodic etching conditions that allow selective removal of silicon oxide from porous low-temperature silicon nitride films without excessive damage to the substrate or unwanted etching of the nitride film.
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 high selectivity in etching silicon oxide films over silicon nitride films, reducing damage to semiconductor substrates and improving the etching process by controlling the exposure times and pressures of the processing gases, thereby enhancing the etching rate and uniformity.
Implementation Method 1
producing an (NH4)2SiF6 (ammonium fluorosilicate) gas through the reaction of the mixed gas with the silicon oxide
Implementation Method 2
The SiO2 film is removed (or etched) by heating and subliming the (NH4)2SiF6 gas
Implementation Method 3
a vacuum exhaust unit configured to vacuum-exhaust an interior of the process vessel
Data Source
AI summary
There is a method of selectively etching a silicon oxide film among a silicon nitride film and the silicon oxide film formed on a surface of a substrate to be processed, the method including: under a vacuum atmosphere, intermittently supplying at least one of a first processing gas composed of a hydrogen fluoride gas and an ammonia gas and a second processing gas composed of a compound of nitrogen, hydrogen and fluorine, to the substrate to be processed multiple times.