Graded SiGe Stressor Segmentation for Boron Diffusion Control
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Solution Overview
Problem
Current methods for enhancing the performance of Metal-Oxide Semiconductor (MOS) devices, such as introducing stress into channel regions, face challenges in effectively managing boron diffusion and lattice mismatch defects while maintaining stressor effectiveness.
Innovation Solution
The process involves forming a MOS device with epitaxially grown SiGe stressors, including germanium-rich layers adjacent to the substrate to prevent boron diffusion and using thin SiGe layers with varying germanium percentages to minimize lattice mismatch defects, thereby optimizing channel stress and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiGe stressors are grown in source and drain regions to induce compressive stress in the channel region, then carrier mobility is improved, but boron diffusion increases and lattice mismatch defects occur
Solution Approach 1:
The source and drain regions are segmented into multiple epitaxial layers with different SiGe compositions. The first SiGe layer (38) has lower germanium content while the second SiGe layer (42) has higher germanium content, creating distinct functional zones that separately manage stress induction and boron diffusion blocking
Solution Approach 2:
Different regions of the source/drain structure are assigned different SiGe compositions tailored to local requirements. The first SiGe layer provides compressive stress where needed, while the second SiGe layer with higher germanium content provides enhanced boron diffusion barrier properties in critical areas
2Reliability
If higher germanium percentages are used in SiGe stressors to enhance stress effectiveness, then carrier mobility improves, but lattice mismatch defects increase
Solution Approach 1:
The SiGe stressor structure is divided into multiple layers with graded germanium percentages. The first SiGe layer (38) has lower germanium content matching the substrate better, while the second SiGe layer (42) has higher germanium content for enhanced stress, with each layer's thickness and composition carefully controlled to minimize dislocation propagation
Solution Approach 2:
The germanium percentage parameter is varied across different epitaxial layers to optimize both stress effectiveness and lattice matching. By controlling the germanium concentration gradient and layer thicknesses, the structure achieves high compressive stress while managing lattice mismatch defects through controlled parameter transitions
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 enhances carrier mobility and reduces boron diffusion, maintaining stressor effectiveness while minimizing defects, thus improving MOS device performance and reliability.
Implementation Method 1
forming a MOS device with epitaxially grown SiGe stressors, including germanium-rich layers adjacent to the substrate to prevent boron diffusion
Implementation Method 2
forming a MOS device with epitaxially grown SiGe stressors, using thin SiGe layers with varying germanium percentages
Implementation Method 3
growing SiGe stressors in the source and drain regions... The epitaxy SiGe stressors apply a compressive stress to the channel region
Data Source
AI summary
An integrated circuit structure includes a gate stack over a semiconductor substrate, and an opening extending into the semiconductor substrate, wherein the opening is adjacent to the gate stack. A first silicon germanium region is in the opening, wherein the first silicon germanium region has a first germanium percentage. A second silicon germanium region is over the first silicon germanium region, wherein the second silicon germanium region has a second germanium percentage higher than the first germanium percentage. A third silicon germanium region is over the second silicon germanium region, wherein the third silicon germanium region has a third germanium percentage lower than the second germanium percentage.