Nanosheet Inner Spacer Blocking Layer for Channel Release Etching
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Solution Overview
Problem
Challenges exist in fabricating nanosheet transistors due to insufficient etch selectivity during channel release processes, leading to damage to source/drain regions in semiconductor devices like GAAFETs and CFETs.
Innovation Solution
A small molecule treatment using volatile molecules with leaving and remaining groups is applied to form a blocking layer on inner spacers, preventing etchant diffusion and protecting source/drain regions during channel release processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etch processes are used for channel release, then the sacrificial layer can be removed, but the source/drain regions are damaged due to insufficient etch selectivity
Solution Approach 1:
A blocking layer is deposited as an intermediary between the etchant and the source/drain regions. This blocking layer selectively prevents etchant diffusion to the source/drain regions while allowing the etch process to proceed with the sacrificial layer, thereby resolving the selectivity issue and preventing damage
Solution Approach 2:
The protective function is segmented from the inner spacer structure by forming a separate blocking layer. This segmentation allows the inner spacer to maintain its structural role while the blocking layer provides the selective protection function, achieving both structural integrity and etch selectivity
2Productivity
If over-etch time is increased to ensure complete sacrificial layer removal, then channel release is more complete, but source/drain region damage increases
Solution Approach 1:
The blocking layer acts as a protective intermediary that enables extended etch durations. By preventing etchant access to source/drain regions, it allows the etch process to run longer to ensure complete sacrificial layer removal without causing damage to sensitive regions
Solution Approach 2:
The blocking layer is deposited beforehand to cushion or protect the source/drain regions from the harmful effects of prolonged etching. This prior protection enables the etch process to proceed to completion without compromising the source/drain regions
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 method reduces or prevents damage to source/drain regions, allowing for increased over-etch time and integration with existing manufacturing processes without affecting throughput.
Implementation Method 1
performing a small molecule treatment with a gas including a leaving group and a remaining group
Implementation Method 2
forming a recess by etching a sacrificial layer
Implementation Method 3
epitaxially growing a source/drain region from exposed tips of the nanosheets
Data Source
AI summary
A method of processing a substrate includes forming a recess by etching a sacrificial layer and forming a blocking layer and an inner spacer in the recess. The sacrificial layer is between a lower nanosheet and an upper nanosheet. The forming the blocking layer includes performing a small molecule treatment with a gas including a leaving group and a remaining group. The method further includes forming a source/drain region and removing the sacrificial layer with an etch process. The source/drain region is adjacent the lower nanosheet, the inner spacer, and the upper nanosheet. The blocking layer protects the source/drain region from etchants.