Fluorine Dry Etching for Square GAA Fin Inner Spacers
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Solution Overview
Problem
Wet etching processes for nanosheets/nanowires in GAA finFET devices result in rounded corners and thinner inner spacer structures, leading to increased epitaxial structure defects and reduced process yield due to oxygen diffusion limits.
Innovation Solution
A dry etching process using fluorine-containing gases, such as F2, HF, ClF3, F*, and NF3*, to form fin structures with a square profile and improve the effective thickness of inner spacer structures, reducing epitaxial structure defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching process is used for nanosheets/nanowires, then the etching can proceed uniformly, but the corners become rounded and inner spacer structures become thinner
Solution Approach 1:
The patent changes the etching chemistry from wet etching to dry etching using fluorine-containing gases (such as CF4, SF6, or NF3). This parameter change in the etching process enables square-profiled inner spacer structures with sharper corners and maintained thickness, while reducing epitaxial structure defects from 30-50% to below 10%.
2Ease of manufacture
If wet etching is used, then the process is simpler to implement, but oxygen diffusion limits cause rounded corners and reduced inner spacer effective thickness
Solution Approach 1:
The patent replaces the wet etching mechanism (chemical solution-based) with a dry etching mechanism (gas-phase plasma or chemical vapor deposition). This substitution eliminates oxygen diffusion limitations that cause rounded corners in wet etching, producing square-profiled inner spacer structures with precise dimensional control.
3Device complexity
If wet etching process is used, then the equipment requirements are lower, but the process yield decreases due to increased epitaxial structure defects
Solution Approach 1:
The patent implements dry etching using fluorine-containing gases, which changes the etching chemistry parameters to achieve square-profiled inner spacer structures. This parameter change reduces epitaxial structure defects from 30-50% to below 10%, improving process yield by 10-30% despite increased equipment complexity.
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 dry etching process reduces epitaxial structure defects from 30-50% to below 10% and improves process yield by 10-30% by forming square-profiled inner spacer structures.
Implementation Method 1
A dry etching process using fluorine-containing gases, such as F2, HF, ClF3, F*, and NF3*, to form fin structures with a square profile
Implementation Method 2
etching a portion of the second set of semiconductor layers with a fluorine-containing gas
Data Source
AI summary
The present disclosure describes a method that includes forming a fin structure with a stacked fin portion on a substrate. The stacked fin portion includes a first semiconductor layer and a second semiconductor layer, in which the second semiconductor layer includes germanium. The method further includes etching the fin structure to form an opening and etching a portion of the second semiconductor layer with a fluorine-containing gas through the opening.