Source/Drain Germanium Gradient for MOSFET Mobility and Simpler Fabrication
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Solution Overview
Problem
As semiconductor devices are scaled down, the operating characteristics of MOSFETs deteriorate due to the linear decrease in germanium concentration in intermediate layers, leading to performance limitations.
Innovation Solution
A semiconductor device design with a source/drain pattern featuring varying germanium concentrations, including a first variation section with a greater rate of change in germanium concentration compared to other sections, and a simplified manufacturing process by eliminating an intermediate layer between the buffer and main layers, enhancing compressive stress and improving electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an intermediate layer with linearly decreasing germanium concentration is used, then the germanium concentration transitions between first and second layers, but the operating characteristics of MOSFETs deteriorate due to the linear decrease in germanium concentration
Solution Approach 1:
The patent changes the germanium concentration distribution from a linear gradient to a non-linear profile with an enhanced rate of change in the first variation section. This parameter modification optimizes the compressive stress distribution, improving hole mobility and MOSFET operating characteristics while maintaining compositional transition between layers.
2Stability of the object's composition
If an intermediate layer is inserted between first and second layers, then germanium concentration transitions are achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the buffer layer and main layer by eliminating the intermediate layer, while still achieving the necessary germanium concentration transition through a modified source/drain pattern with varied concentrations. This reduces the number of discrete layers and simplifies the manufacturing process.
Solution Approach 2:
The patent applies local quality by creating a source/drain pattern with non-uniform germanium concentration distribution, specifically with a first variation section having an enhanced rate of change. This localized optimization achieves the desired stress distribution without requiring a separate intermediate layer throughout the structure.
3Reliability
If germanium concentration is varied in the source/drain pattern, then mobility is increased, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameters for the germanium concentration profile, including a rate of change of 6-10 at%/nm in the first variation section and concentration ranges of 0-10 at% at specific levels. These quantified parameters provide clear manufacturing targets while achieving improved electrical characteristics.
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 design facilitates easier manufacturing and increases mobility, resulting in improved electrical characteristics and performance of the semiconductor device.
Implementation Method 1
providing increased compressive stress and simplified manufacturing processes by eliminating an intermediate layer, thereby enhancing hole mobility and electrical characteristics
Data Source
AI summary
A semiconductor device includes a substrate including an active pattern, a channel pattern on the active pattern, and a source/drain pattern on a side surface of the channel pattern, the source/drain pattern including a first section between a first level and a second level that is higher than the first level, a first variation section between the second level and a third level that is higher than the second level, and a second section between the third level and a fourth level that is higher than the third level, where a rate of change in germanium concentration in the first variation section in a first direction is greater than a rate of change in germanium concentration in each of the first section and the second section in the first direction, and a germanium concentration at each of the first level and the second level is greater than 0 at % and equal to or less than 10 at %.