Selective Silicon Oxide Etching While Preserving Nitride Films
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Solution Overview
Problem
Existing semiconductor processing technologies lack the ability to selectively etch silicon oxide films without damaging adjacent silicon nitride films, which is crucial for maintaining device functionality, particularly in logic and memory applications.
Innovation Solution
A method involving multiple etching processes with specific gas combinations and temperature controls is employed to selectively remove silicon oxide and oxynitride layers while preserving silicon nitride layers, using gases like NF3, CF4, and inert gases, with optional bake steps to manage reaction byproducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etching process is used to remove silicon oxide films, then the oxide layer is removed, but the silicon nitride film is damaged or removed along with it
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas compositions. The first step uses a specific gas mixture to etch oxide while protecting nitride, followed by a second step with different gas composition to complete oxide removal. This segmentation allows selective etching of oxide layers without damaging the nitride film, achieving high selectivity ratios.
Solution Approach 2:
The patent employs changes in gas composition parameters between etching steps. The first etching step uses a fluorocarbon-based gas mixture, while the second step uses a different gas composition. These parameter changes enable differential etching rates for oxide versus nitride layers, achieving selective removal of oxide while preserving nitride structures.
2Productivity
If the etching process is made more aggressive to improve oxide removal rate, then productivity increases, but nitride layer loss increases
Solution Approach 1:
The high-selectivity etching process is segmented into multiple steps with different gas compositions and duration. This allows the total oxide removal to be achieved through cumulative effect of multiple milder etching steps rather than a single aggressive step, thereby maintaining high productivity while minimizing nitride layer loss through selective protection.
Solution Approach 2:
The patent employs periodic alternation between different gas compositions during the etching process. By periodically switching between gas mixtures with different selectivity characteristics, the process maintains high overall etching throughput while periodically protecting the nitride layer from excessive damage, achieving both productivity and material preservation.
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 a high selectivity ratio of etching silicon oxide to nitride layers, minimizing nitride layer loss by up to 80%, ensuring the integrity of semiconductor devices.
Implementation Method 1
performing a first etching process, wherein the first etching process comprises flowing a hydrogen precursor gas, a fluorine precursor gas, and an inert gas onto the substrate
Implementation Method 2
flowing a hydrogen precursor gas, a fluorine precursor gas, and an inert gas onto the substrate
Data Source
AI summary
An apparatus and methods for selectively etching a particular layer are disclosed. The apparatus and methods are directed towards maintaining the etch rate of the particular layer, while keeping intact a non-etched layer. A gas mixture may be flowed onto the substrate in separate loops having an oxide layer and an oxynitride layer as an etch layer and a nitride layer as a non-etched layer, for example. A reaction between the resulting gas mixture and the particular layer takes place, resulting in etching of the oxide layer and the oxynitride layer while maintaining the nitride layer in the above example.