Non-planar SiGe PFET Channel with Intermediary Capping Layer
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Solution Overview
Problem
The fabrication of non-planar transistor structures is limited by material properties, particularly in achieving high mobility and performance due to challenges in channel material engineering, such as crystal defects from significant disparities in Germanium concentrations between substrate and channel layers.
Innovation Solution
A semiconductor device structure is fabricated with a Germanium compound channel layer having a higher Germanium concentration than the substrate, a capping layer with a lower Germanium concentration, and uni-axial stress inducing portions with varying Germanium concentrations to enhance transistor performance by reducing crystal defects and improving mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a channel layer with high Germanium concentration is formed on a substrate with low Germanium concentration, then mobility and transistor performance are improved, but crystal defects increase due to significant concentration disparity
Solution Approach 1:
A capping layer with intermediate Germanium concentration is introduced between the high-Germanium channel layer and the low-Germanium substrate. This intermediary layer acts as a transition zone that reduces the abrupt concentration gradient, thereby minimizing crystal defects while preserving the high mobility benefits of the high-Germanium channel layer.
Solution Approach 2:
The patent applies different Germanium concentrations to different spatial regions: the substrate maintains low Germanium concentration, the capping layer has intermediate concentration, and the channel layer has high concentration. This localized variation in material composition optimizes both performance and defect reduction in their respective regions.
2Object-affected harmful factors
If the Germanium concentration difference between substrate and channel layer is reduced, then crystal defects decrease, but mobility and transistor performance deteriorate
Solution Approach 1:
The capping layer with intermediate Germanium concentration serves as a mediator that allows the channel layer to maintain high Germanium concentration for optimal mobility while the substrate retains low concentration. The intermediary layer bridges the concentration gap, preventing defect formation despite the large overall concentration difference.
3Object-affected harmful factors
If a capping layer with low Germanium concentration is used to separate the channel layer from the metal gate, then crystal defects are minimized, but quantum well confinement is reduced
Solution Approach 1:
The capping layer is positioned specifically at the interface region where defect prevention is most critical, while the channel layer maintains high Germanium concentration in its bulk region to preserve quantum well confinement. This localized application of low Germanium concentration achieves defect reduction without sacrificing confinement properties.
Data Source
AI summary
Systems and methods are provided for fabricating a semiconductor device structure. An example semiconductor device structure includes a channel layer formed of a Germanium compound having a Germanium concentration B formed on a semiconductor substrate having a Germanium concentration of A, the Germanium concentration of the substrate A being less than the Germanium concentration of the channel layer B. The structure further includes a capping layer formed to separate the channel layer from a metal gate, the capping layer having a Germanium concentration of C, the Germanium concentration of the channel layer B being greater than the Germanium concentration of the capping layer C.