Strained Channel Transistor Pocket Structure
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Solution Overview
Problem
The semiconductor industry faces challenges in scaling down transistor technology due to strain relaxation and short channel effects caused by implantation processes in SiGe source/drain regions, leading to reduced performance and increased diffusion.
Innovation Solution
A method involving the formation of a semiconductor device with strained channels using epitaxially grown SiGe source/drain regions, where pockets are created between the SiGe and the substrate to maintain strain and reduce relaxation, and a second layer is added to enhance performance, thereby controlling short channel effects and preventing current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiGe source/drain regions are formed in the silicon substrate, then strain is introduced to enhance transistor performance, but defects at the substrate/SiGe interface increase short channel effects by enhancing diffusion
Solution Approach 1:
Pocket regions are introduced as intermediary structures between the SiGe source/drain regions and the channel. These pockets serve as diffusion barriers that block harmful diffusion paths from the SiGe regions into the channel, thereby reducing short channel effects while preserving the strain necessary for high transistor performance
Solution Approach 2:
The patent creates localized pocket regions specifically at the interface between the SiGe source/drain regions and the channel. This local modification targets the specific area where defects and diffusion occur, providing stress blocking and diffusion prevention exactly where needed without affecting other regions of the device
2Productivity
If geometry size is decreased to increase functional density, then production efficiency increases and costs are lowered, but strain relaxation and short channel effects become more pronounced
Solution Approach 1:
The patent modifies the structural parameters of the source/drain regions by forming SiGe epitaxial layers with specific thicknesses and compositions, and by introducing pocket regions at controlled depths. These parameter changes enable the maintenance of strain in scaled-down devices, allowing continued geometry reduction while preserving transistor performance
Solution Approach 2:
Pocket regions serve as intermediary stress-blocking features that become increasingly important as device dimensions are reduced. In scaled-down devices, these pockets prevent strain relaxation more effectively, enabling the continuation of scaling while maintaining the strain necessary for high carrier mobility and performance
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 improves carrier mobility, reduces strain relaxation, and allows for continued scaling of semiconductor devices by maintaining strain and controlling short channel effects, leading to enhanced performance and reliability.
Implementation Method 1
strain is often introduced into the transistor channel for improving mobility enhancement. Strain may be introduced by having an IC device comprising a silicon substrate and SiGe source/drain regions. The SiGe source/drain regions introduce strain into a silicon channel.
Implementation Method 2
forming one or more recesses in the substrate, wherein the one or more recesses define at least one source region and at least one drain region; and forming a pocket, a first layer comprising a second material, and a second layer comprising a third material in the one or more recesses
Data Source
AI summary
A semiconductor device and method for fabricating a semiconductor device providing reduced short channel effects is disclosed. The method comprises providing a substrate comprising a first material; forming at least one gate stack over the substrate; forming one or more recesses in the substrate, wherein the one or more recesses define at least one source region and at least one drain region; and forming a pocket, a first layer comprising a second material, and a second layer comprising a third material in the one or more recesses, the pocket being disposed between the first layer and the substrate.