SiGe Fin Channel Formation via Ge Diffusion
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Solution Overview
Problem
Existing semiconductor processing methods for forming SiGe channels in finFETs often result in faceted surfaces with non-uniform Ge profiles, which can affect device performance due to epitaxial growth processes.
Innovation Solution
A method involving the deposition of an amorphous Ge layer over a Si fin, followed by oxidation to diffuse Ge atoms into the fin, forming a facet-free SiGe channel region without epitaxial growth, maintaining the original fin shape and achieving uniform Ge distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If SiGe structures are formed epitaxially, then SiGe fins can be created, but faceted surfaces with non-uniform Ge profiles are formed
Solution Approach 1:
The patent changes the fundamental formation parameter from epitaxial growth to diffusion-based formation. By depositing an amorphous SiGe layer and then performing a thermal diffusion process, the Ge atoms diffuse into the Si fin to form a SiGe channel region. This parameter change eliminates faceting while achieving uniform Ge distribution, resolving the contradiction between manufacturing precision and ease of manufacture.
Solution Approach 2:
The patent replaces the mechanical/chemical process of epitaxial growth with a diffusion-based process. Instead of growing SiGe material layer by layer through epitaxy, the method uses thermal diffusion to transport Ge atoms from the amorphous SiGe layer into the Si fin, creating a SiGe channel region without faceting. This substitution achieves uniform Ge profiles while simplifying the manufacturing process.
2Reliability
If SiGe is used instead of Si, then performance advantages are achieved, but faceted surfaces with non-uniform Ge profiles are formed
Solution Approach 1:
The patent changes the formation mechanism from epitaxial growth to diffusion, which fundamentally alters how Ge is distributed in the SiGe structure. The diffusion process naturally produces uniform Ge profiles because Ge atoms diffuse according to concentration gradients, ensuring even distribution throughout the channel region. This maintains device performance while achieving the desired Ge uniformity.
Solution Approach 2:
The patent introduces an amorphous SiGe layer as an intermediary material that serves as the Ge source for diffusion. This intermediary layer allows controlled Ge release into the Si fin during thermal processing, ensuring uniform Ge distribution without the faceting problems associated with direct epitaxial SiGe growth. The intermediary layer acts as a reservoir that feeds Ge atoms uniformly into the channel region.
3Shape
If epitaxial growth is used to form SiGe fins, then SiGe structures are created, but the original fin shape is distorted due to faceting
Solution Approach 1:
The patent segments the SiGe formation process into two distinct stages: first forming the Si fin structure with the desired shape, then separately introducing Ge through diffusion. This segmentation allows the Si fin to maintain its original shape while Ge is added in a controlled manner through the amorphous SiGe layer, preventing the faceting that would otherwise distort the fin geometry during epitaxial growth.
Solution Approach 2:
The patent performs preliminary formation of the Si fin structure before introducing Ge. By first establishing the Si fin with the correct geometry and then performing Ge diffusion, the original fin shape is preserved. The preliminary Si fin formation acts as a template that guides the subsequent Ge diffusion process, ensuring uniform Ge distribution without shape distortion.
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 ensures a uniform and high Ge concentration in the SiGe channel region, enhancing device performance by preventing faceting and maintaining the fin's original shape, thus improving the operational consistency and efficiency of finFETs.
Implementation Method 1
oxidizing the amorphous layer to condense out Ge and diffuse the Ge into the region of the underlying fin to form a channel region including Ge
Data Source
AI summary
A fin field effect transistor includes a Si fin including a central portion between end portions of the fin, and a SiGe channel region disposed on the central portion of the fin. The SiGe channel region includes a facet free SiGe region having Ge atoms diffused into the Si fin and includes a same shape as the Si fin outside the central portion.