Self-Limiting Sidewall Protection for Etched Holes
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Solution Overview
Problem
As substrate geometries shrink, the continuous sidewall deposition of protection layers during etching processes leads to over deposition, especially in corners, affecting the shape of holes and causing etch shadowing effects, which impact the performance of formed structures.
Innovation Solution
A self-limiting etch protection layer is formed using a cyclical series of etch and protective layer formation steps, with a silicon oxide layer that limits over deposition by reacting with silicon to form a thin, controllable protective layer, minimizing over deposition in corners and maintaining critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorocarbon plasma processing is used to provide carbon based sidewall protection layer, then sidewall protection is achieved enabling anisotropic etching, but over deposition occurs particularly in corner locations affecting pattern geometry
Solution Approach 1:
The patent implements periodic action by cycling between etching steps and protective layer formation steps. The etch process alternates with brief exposures to oxygen plasma that form thin oxide layers on sidewalls, preventing continuous carbon deposition. This periodic switching between etching and protection phases controls the protective layer thickness and prevents over-deposition in corners while maintaining sidewall protection throughout the etch process.
2Reliability
If continuous sidewall deposition process is used, then sidewall protection is maintained throughout etch process, but deposition is not self-limiting leading to excessive layer accumulation
Solution Approach 1:
The patent applies self-service by utilizing the etched surface itself to regulate protective layer formation. The oxygen plasma forms oxide layers that are naturally limited by the available silicon surface; as the etch progresses and surface area changes, the oxide formation automatically adjusts. The cyclical process allows the protective layer to self-regulate its thickness based on the instantaneous sidewall geometry without requiring external control mechanisms.
3Reliability
If protective layer deposition continues during etch process, then sidewalls are protected, but corner locations accumulate excessive deposition causing etch shadowing effects
Solution Approach 1:
The periodic cycling between etching and protective layer formation prevents continuous deposition that causes corner accumulation. During each etch phase, material is removed uniformly including from corners. During subsequent brief oxygen exposure phases, thin oxide layers form on all exposed surfaces including corners, but the limited exposure time prevents excessive buildup. This periodic alternation maintains protective coverage while preventing the shadowing effects that occur with continuous deposition.
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 self-limiting silicon oxide protective layer prevents excessive deposition, ensuring a more controllable hole profile and etch process, reducing etch shadowing effects and maintaining the desired geometry of polygonal holes.
Implementation Method 1
exposing the substrate to a protective layer formation plasma, the protective layer formation plasma reacting with the exposed sidewalls of the underlying layer to form a self-limiting protective layer
Implementation Method 2
exposing the substrate to a first plasma, the first plasma comprising oxygen; exposing the substrate to a second plasma, the second plasma etching portions of the silicon layer
Data Source
AI summary
Substrate processing techniques are described in which an etch protection layer that is formed as part of an etch process forms in a self-limiting nature. Thus, over deposition effects are minimized, particularly in the corners of etched polygonal holes. In one embodiment, the layer being etched contains silicon and the protective layer comprises a silicon oxide (SixOy). The process may include the use of a cyclical series of etch and protective layer formation steps. In the case of a silicon oxide based protective layer, a thin protective layer of silicon oxide may be formed in a limiting and controllable manner due to the nature of the oxygen atom interaction with silicon and newly formed silicon oxide protective layers. In this manner, a polygonal hole may be formed without detrimental over deposition of a protective layer in corners of the hole.