HF Two-Step Oxide Etching for Uniform Substrate Processing
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Solution Overview
Problem
Existing substrate-processing methods using a gas mixture of hydrogen fluoride and ammonia for etching silicon oxide films often result in non-uniform in-plane etching depth due to consumption of gases at the substrate's outer periphery before reaching the center, leading to challenges in achieving uniform etching, especially in short-term processes.
Innovation Solution
A substrate-processing method involving two sequential gas supply steps: first, a gas containing hydrogen fluoride but no basic gas is supplied to the substrate surface to form silicon tetrafluoride, followed by a gas containing both hydrogen fluoride and a basic gas to form ammonium silicofluoride, thereby adjusting the in-plane distribution of the etching depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gas mixture of hydrogen fluoride and ammonia is supplied to etch silicon oxide film, then etching can be performed, but in-plane uniformity of etching depth deteriorates due to gas consumption at outer periphery
Solution Approach 1:
The etching process is divided into two sequential stages: first supplying hydrogen fluoride gas alone to uniformly etch the silicon oxide film across the entire substrate surface, then supplying a gas mixture containing ammonia to complete the etching. This segmentation allows the highly reactive HF to work alone first, ensuring uniform gas distribution and etching rate across the substrate, before introducing ammonia which tends to be consumed at the periphery.
Solution Approach 2:
Hydrogen fluoride gas is supplied in advance before the ammonia-containing gas mixture. The HF gas performs the primary etching action on the silicon oxide film first, establishing a uniform etching depth across the substrate. This preliminary action ensures that when ammonia is subsequently introduced, the etching is already well-established and uniform, minimizing the impact of ammonia consumption at the periphery.
2Manufacturing precision
If etching duration is extended to improve in-plane uniformity, then uniformity improves, but etching depth increases excessively
Solution Approach 1:
The etching process is divided into two sequential stages: first supplying hydrogen fluoride gas alone to uniformly etch the silicon oxide film across the entire substrate surface, then supplying a gas mixture containing ammonia to complete the etching. This segmentation allows the highly reactive HF to work alone first, ensuring uniform gas distribution and etching rate across the substrate, before introducing ammonia which tends to be consumed at the periphery.
Solution Approach 2:
Hydrogen fluoride gas is supplied in advance before the ammonia-containing gas mixture. The HF gas performs the primary etching action on the silicon oxide film first, establishing a uniform etching depth across the substrate. This preliminary action ensures that when ammonia is subsequently introduced, the etching is already well-established and uniform, minimizing the impact of ammonia consumption at the periphery.
3Productivity
If short-term etching is performed, then productivity is improved, but in-plane uniformity of etching depth deteriorates
Solution Approach 1:
The gas composition parameter is changed between two stages: first using pure hydrogen fluoride gas (100% HF) for the majority of the etching process to ensure uniformity, then switching to a gas mixture containing ammonia (e.g., HF:NH3 in ratios like 4:1 to 1:1) to complete the etching. This parameter change allows the process to achieve uniform etching in a shorter total time by leveraging the high reactivity and uniform distribution characteristics of HF alone, followed by ammonia-containing gas for final processing.
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 allows for the adjustment of in-plane etching depth distribution of silicon oxide films during short-term etching processes, improving uniformity and reducing the risk of etching silicon nitride films, thus enhancing etching selectivity.
Implementation Method 1
supplying a first gas to the surface of the substrate, the first gas containing a hydrogen fluoride gas and containing no basic gas... supplying a second gas to the surface of the substrate, the second gas containing both a hydrogen fluoride gas and a basic gas
Implementation Method 2
supplying a second gas to the surface of the substrate, the second gas containing both a hydrogen fluoride gas and a basic gas... form ammonium silicofluoride
Data Source
AI summary
A substrate-processing method includes (a) providing a substrate including a silicon oxide film on a surface of the substrate; (b) supplying a first gas to the surface of the substrate, the first gas containing a hydrogen fluoride gas and containing no basic gas; and (c) after (b), supplying a second gas to the surface of the substrate, the second gas containing both a hydrogen fluoride gas and a basic gas.