Layered Source/Drain Doping to Reduce Short Channel Effect
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Solution Overview
Problem
The challenge in semiconductor technology is to reduce the short channel effect in transistors, which is caused by the out-diffusion of dopants from the source/drain region, leading to electrical leakage and increased contact resistance, thereby affecting the performance and efficiency of field effect transistors (FETs).
Innovation Solution
A semiconductor device structure is proposed, where the source/drain region consists of a first n-type doped layer with a spike doping profile and a second n-type doped layer, where the first n-type dopant has a lower atomic mass than the second n-type dopant, and the doping profile is designed to prevent out-diffusion of dopants towards the channel region, thereby reducing the short channel effect and improving transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopants are heavily doped in the source/drain region to reduce contact resistance, then contact resistance decreases, but out-diffusion of dopants towards the channel region increases causing short channel effect
Solution Approach 1:
The source/drain region is segmented into multiple layers with different doping concentrations. The first source/drain layer has a higher doping concentration to reduce contact resistance, while the second source/drain layer has a lower doping concentration to prevent out-diffusion towards the channel. This segmentation allows each layer to fulfill its specific function independently.
Solution Approach 2:
Different regions of the source/drain structure are assigned different doping qualities. The region adjacent to the contact (first layer) has high doping concentration for low resistance, while the region adjacent to the channel (second layer) has low doping concentration to prevent harmful out-diffusion. This local differentiation resolves the contradiction between contact resistance and short channel effect.
2Reliability
If an underlap is introduced between gate terminal and source/drain terminal to reduce channel resistance, then channel resistance decreases, but short channel effect increases due to dopant out-diffusion
Solution Approach 1:
The source/drain region is divided into two layers where the first layer extends further under the gate (creating the underlap) with high doping for low channel resistance, while the second layer is positioned closer to the channel with low doping to prevent out-diffusion. This layered segmentation enables the underlap structure to reduce channel resistance without exacerbating the short channel effect.
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 the short channel effect, enhancing the transistor's static power consumption and threshold voltage control, while also lowering contact resistance, thus improving the overall performance of FETs.
Implementation Method 1
the out-diffusion of dopants from the source/drain region
Data Source
AI summary
The present disclosure describes a semiconductor structure and a method for forming the same. The method can include forming a recess structure in a substrate and forming a first semiconductor layer over the recess structure. The process of forming the first semiconductor layer can include doping first and second portions of the first semiconductor layer with a first n-type dopant having first and second doping concentrations, respectively. The second doping concentration can be greater than the first doping concentration. The method can further include forming a second semiconductor layer over the second portion of the first semiconductor layer. The process of forming the second semiconductor layer can include doping the second semiconductor layer with a second n-type dopant.