Modulating Germanium Percentage in SiGe Stressors for MOS Devices
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Solution Overview
Problem
Current Metal-Oxide Semiconductor (MOS) devices face limitations in performance enhancement due to challenges in modulating the channel region's stress and germanium percentage, which affect carrier mobility and source-to-drain resistance.
Innovation Solution
The process involves forming a gate stack on a semiconductor substrate, growing SiGe stressors in recesses to apply compressive stress, and using epitaxial growth to create regions with varying germanium percentages, followed by silicidation to reduce source/drain resistance and enhance carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SiGe stressors are grown in recesses to apply compressive stress to the channel region, then carrier mobility is improved, but source-to-drain resistance increases
Solution Approach 1:
The patent applies different germanium percentages at different locations: higher germanium content (30-70%) in the stressor regions adjacent to the channel to maximize compressive stress and carrier mobility, while maintaining lower germanium content in other regions to control source-to-drain resistance. This spatial variation in material composition resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The patent modulates the germanium percentage parameter across different regions of the device. By changing the germanium concentration from 0% in pure silicon regions to 30-70% in stressor regions, the patent simultaneously achieves the desired compressive stress for high carrier mobility while controlling the overall resistance characteristics through parameter optimization.
2Object-affected harmful factors
If germanium percentage is increased in source and drain regions, then source-to-drain resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent divides the source and drain regions into multiple segments with different germanium percentages. The first source/drain regions have a first germanium percentage while the second source/drain regions have a second germanium percentage. This segmentation allows independent optimization of each region's electrical characteristics while using standardized fabrication processes for each segment, thereby managing manufacturing complexity.
Solution Approach 2:
The patent introduces a compositional dimension by varying germanium percentage across different regions and depths. Instead of uniform composition, the patent creates a graded or stepped germanium distribution in the vertical and lateral dimensions, enabling fine-tuned control of source-to-drain resistance through compositional profiling rather than complex geometric structures.
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 effectively reduces source-to-drain resistance and enhances carrier mobility by introducing stress and optimizing germanium distribution, thereby improving MOS device performance.
Implementation Method 1
Since SiGe has a lattice constant greater than that of silicon, it applies a compressive stress to the channel region
Implementation Method 2
epitaxial growth to create regions with varying germanium percentages
Implementation Method 3
followed by silicidation to reduce source/drain resistance
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 disposed in the opening, wherein the first silicon germanium region has a first germanium percentage. A second silicon germanium region is overlying the first silicon germanium region, wherein the second silicon germanium region has a second germanium percentage higher than the first germanium percentage. A metal silicide region is over and in contact with the second silicon germanium region.