Silicon Oxide Vapor Etching for High Nitride Selectivity
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Solution Overview
Problem
Current isotropic etching methods for silicon oxide films in 3D-NAND flash memory and Fin-type FET processing face challenges with etching residue and poor controllability in minute structures, and difficulty in achieving high selectivity when alternatingly stacked with silicon nitride films.
Innovation Solution
An etching method involving the use of hydrogen fluoride and alcohol vapor in a controlled temperature range of -30°C to -50°C, with additional steps for deposit removal using infrared light heating, to achieve high accuracy and selectivity in etching silicon oxide films relative to silicon nitride films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wet processing using chemical solution is used for isotropic etching, then etching can be performed in lateral direction, but pattern collapse due to surface tension and etching residue in gaps occur
Solution Approach 1:
The patent replaces wet chemical processing with a vapor-phase dry etching process using HF and alcohol vapor. This substitution eliminates liquid surface tension effects that cause pattern collapse while maintaining isotropic etching capability through vapor deposition and chemical reaction mechanisms.
Solution Approach 2:
The patent uses a controlled vapor atmosphere of HF and alcohol in a processing chamber, creating an inert-like environment that prevents unwanted side reactions and residue formation. The vapor phase processing avoids the harmful effects of liquid chemical solutions while maintaining effective etching.
2Loss of substance
If conventional dry etching is used for silicon oxide film, then chemical solution processing is reduced, but insufficient selectivity against silicon nitride film and etching residue remain
Solution Approach 1:
The patent changes the chemical parameters by using a specific mixture of HF vapor and alcohol vapor at controlled temperatures (-30°C to -50°C). This parameter optimization achieves high etching rates for silicon oxide while maintaining low etching rates for silicon nitride, providing the required selectivity without chemical solution residue.
Solution Approach 2:
The patent employs a composite vapor processing system combining HF (for etching silicon oxide) and alcohol (as a modifier to control etching characteristics and prevent residue). This composite approach achieves superior selectivity and cleanliness compared to single-gas dry etching processes.
3Manufacturing precision
If etching selectivity between silicon oxide and silicon nitride films is increased, then processing accuracy improves, but etching rate may decrease
Solution Approach 1:
The patent optimizes temperature parameters (-30°C to -50°C) and vapor composition ratios to achieve a unique condition where high selectivity (10:1 or more between silicon oxide and silicon nitride) and high etching rate are simultaneously realized. This parameter optimization breaks the traditional trade-off between selectivity and productivity.
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 method enables high etching rates for silicon oxide films while maintaining low etching rates for silicon nitride films, ensuring high accuracy and selectivity, thus addressing the limitations of existing techniques.
Implementation Method 1
supplying processing gas into the processing chamber including a step of supplying hydrogen fluoride and alcohol vapor into the processing chamber
Implementation Method 2
maintaining the wafer in a range of −30° C. to −50° C.
Implementation Method 3
removing deposits of ammonium hexauorosilicate derived from materials of the silicon nitride film
Data Source
AI summary
Provided is an etching method for etching a silicon oxide film with a high accuracy at a high selection ratio with respect to a silicon nitride film, the etching method of etching a film structure, in which an end portion of a film layer in which the silicon oxide film and the silicon nitride film formed in advance on a wafer disposed in a processing chamber are alternately stacked in a vertical direction forms a side wall of a groove or a hole, by supplying processing gas into the processing chamber includes a step of supplying hydrogen fluoride and alcohol vapor into the processing chamber, maintaining the wafer at a temperature of −20° C. or lower, preferably −20° C. to −60° C., and etching the silicon oxide film from the end portion in a lateral direction.