Amorphous Carbon Sidewall Liner for Deep Etch CD Control
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Solution Overview
Problem
Existing semiconductor fabrication processes struggle to create high aspect ratio features with tight critical dimension (CD) control, leading to issues like lateral etching, bowing, and electrical shorting due to inadequate insulation.
Innovation Solution
The use of an amorphous carbon liner deposited via Plasma Enhanced Chemical Vapor Deposition (PECVD) on the sidewalls of features during vertical etching, which resists lateral etching and allows for deeper feature etching while maintaining CD control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional etching processes are used for deep vertical etching, then feature depth increases, but lateral etching increases and critical dimension control deteriorates
Solution Approach 1:
An amorphous carbon liner is deposited on the sidewalls of the feature to act as a protective intermediary layer. This liner prevents lateral etching of the feature walls during deep vertical etching, thereby maintaining critical dimension control while enabling increased feature depth. The liner is replenished periodically during the etching process to maintain its protective function throughout the deep etching operation.
2Reliability
If amorphous carbon liner is deposited on sidewalls, then lateral etching resistance improves, but excess carbon deposition in holes occurs causing pinch off
Solution Approach 1:
The deposition parameters are precisely controlled to optimize the balance between liner formation and excess deposition. By adjusting deposition rate, temperature, and precursor flow rates, the process achieves sufficient lateral etching resistance while minimizing carbon accumulation in the hole openings that would cause pinch-off conditions.
3Reliability
If liner material is highly resistant to etch chemistries, then protection against bowing improves, but surface irregularities and striations increase
Solution Approach 1:
The etching parameters are optimized to achieve selective removal of the amorphous carbon liner. By controlling ion energy, gas composition, and etch rate, the process removes the carbon liner uniformly without causing striations or surface irregularities, while still providing adequate protection against feature bowing during the etching process.
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 approach minimizes lateral etching, prevents bowing and surface irregularities, and enables the fabrication of highly dense, deep features with extremely high aspect ratios and tight CD control, addressing the limitations of current technologies.
Implementation Method 1
depositing a highly etch resistant, amorphous, carbon film onto sidewalls of the features using Plasma Enhanced Chemical Vapor Deposition (PECVD)
Implementation Method 2
a highly etch resistant, amorphous, carbon film onto sidewalls of the features
Data Source
AI summary
Fabricating a semiconductor substrate by (a) vertical etching a feature having sidewalls and a depth into one or more layers formed on the semiconductor substrate and (b) depositing an amorphous carbon liner onto the sidewalls of the feature. Steps (a) and optionally (b) are iterated until the vertical etch feature has reached a desired depth. With each iteration of (a), the feature is vertical etched deeper into the one or more layers, while the amorphous carbon liner resists lateral etching of the sidewalls of the feature. With each optional iteration of (b), the deposited amorphous carbon liner on the sidewalls of the feature is replenished.