FinFET Strained Channels Using Diffusion Blocking Layers
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Solution Overview
Problem
Semiconductor finFETs face strain loss during source and drain formation due to cavity etching processes, which is not fully recoverable with existing methods, leading to increased on-state resistance.
Innovation Solution
Incorporating a diffusion blocking layer, such as SiC, between the doped source and drain regions and the underlying fin region within dielectric material to prevent dopant diffusion and preserve strain, while allowing for increased doping to reduce on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cavity etching processes are used for source and drain formation, then source and drain regions can be formed, but strain is lost (approximately 50% of cSiGe strain)
Solution Approach 1:
A diffusion blocking layer (e.g., SiC) is introduced as an intermediary between the doped source/drain regions and the underlying fin region. This blocking layer prevents dopant diffusion into the fin region while preserving the strain in the channel, thereby resolving the contradiction between forming source/drain regions and maintaining strain.
Solution Approach 2:
The source and drain regions are segmented into two parts: a doped region for electrical contact and a strained region for carrier mobility enhancement. The diffusion blocking layer enables this segmentation by preventing dopant contamination of the strained channel region while allowing sufficient dopant in the source/drain regions to reduce on-state resistance.
2Manufacturing precision
If cladding techniques are used to prevent strain loss, then strain is preserved, but there is not enough SiGe:B volume to provide junction overlap
Solution Approach 1:
The diffusion blocking layer acts as a mediator that allows the fin region to maintain its strained composition without requiring additional SiGe:B cladding material. By blocking dopant diffusion, the blocking layer enables sufficient SiGe:B volume in the source/drain regions to provide the necessary junction overlap for lowering Ron.
3Manufacturing precision
If embedded source and drain epitaxial processes are used, then some strain loss can be recovered, but the process is not simple
Solution Approach 1:
The diffusion blocking layer provides a simple and effective mechanism to prevent strain loss during source and drain formation, avoiding the need for complex embedded epitaxial processes. The blocking layer can be formed using standard deposition techniques and integrated into existing process flows, thereby reducing overall process complexity while achieving strain 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
The diffusion blocking layer effectively maintains strain post-source and drain formation, reduces on-state resistance by providing a sufficient boron source for junction overlap, and simplifies integration with minimal disruption to the process flow.
Implementation Method 1
Incorporating a diffusion blocking layer, such as SiC, between the doped source and drain regions and the underlying fin region within dielectric material to prevent dopant diffusion and preserve strain
Implementation Method 2
growing an epitaxial layer on the diffusion blocking layer; doping the epitaxial layer with a dopant; and forming source and drain regions from the doped epitaxial layer
Data Source
AI summary
The present disclosure generally relates to semiconductor structures and, more particularly, to finFETs with strained channels and reduced on state resistances and methods of manufacture. The structure includes: a plurality of fin structures comprising doped source and drain regions with a diffusion blocking layer between the doped source and drain regions and an underlying fin region formed within dielectric material.