Cryogenic Etch Gas Composition for Ammonium Salt Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing plasma etching processes face challenges with etching interruptions due to the formation of ammonium salts during the cryogenic etching of semiconductor devices, particularly when forming structures with high aspect ratios.
Innovation Solution
A method involving a plasma etching apparatus that uses a combination of first and second process gases, where the first gas generates radicals for etching and the second gas, typically an R—OH compound, suppresses the formation of ammonium salts by introducing a second process gas such as methanol to reduce the production rate of ammonium salts during the cryogenic etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cryogenic etching is performed using plasma with process gas to achieve high selectivity and high-aspect-ratio structure formation, then etching precision and structure quality are improved, but ammonium salt is produced during the etching process causing etching interruptions and process defects
Solution Approach 1:
The patent extracts and removes the harmful ammonium salt byproduct from the etching process by introducing a second process gas (R-OH compound) that reacts with and eliminates the ammonium salt, preventing etching interruptions while maintaining the high selectivity benefits of cryogenic etching
Solution Approach 2:
The second process gas (R-OH compound) acts as an intermediary substance that mediates between the etching radicals and the ammonium salt byproduct, facilitating the removal of harmful ammonium salt without interfering with the primary etching function of the first process gas
2Shape
If cryogenic etching is performed to form high-aspect-ratio structures with high selectivity, then structural quality is improved, but etching interruptions occur due to ammonium salt formation
Solution Approach 1:
The patent converts the harmful ammonium salt byproduct into a beneficial removal process by introducing the R-OH compound that specifically reacts with and eliminates the ammonium salt, transforming the source of etching interruptions into an opportunity for process stabilization and continuous high-aspect-ratio structure formation
3Manufacturing precision
If process gas is used for plasma etching to achieve high selectivity, then etching performance is improved, but process defects are generated due to ammonium salt production
Solution Approach 1:
The patent uses a composite process gas system consisting of two distinct gases: the first process gas (CF4) for primary etching function and the second process gas (R-OH compound) for byproduct removal, creating a synergistic gas mixture that simultaneously achieves high etching selectivity and eliminates process defects caused by ammonium salt accumulation
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
The method effectively reduces etching interruptions and enhances the formation of high-aspect-ratio features by controlling the production rate of ammonium salts, leading to more reliable semiconductor device fabrication.
Implementation Method 1
generating the plasma from the process gas, such that radicals of the first process gas etch the portion of the mold layer
Implementation Method 2
cryogenic etching process that uses plasma
Data Source
AI summary
A method of fabricating a semiconductor device comprises forming a mold layer on a substrate, forming a hardmask layer on the mold layer such that a portion of the mold layer is exposed, and using the hardmask layer to perform on the mold layer a cryogenic etching process. The cryogenic etching process includes supplying a chamber with a process gas including first and second process gases, and generating a plasma from the process gas. Radicals of the first process gas etch the exposed portion of the mold layer. Ammonium salt is produced based on the radicals etching the exposed portion of the mold layer. The second process gas includes an R—OH compound. The R is hydrogen, a C1 to C5 alkyl group, a C2 to C6 alkenyl group, a C2 to C6 alkynyl group, or a phenyl group. The second process gas reduces a production rate of the ammonium salt.