Co-Implanted Drain-Extended MOSFETs for Low Rsd and Stable Vt
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Solution Overview
Problem
As semiconductor devices are scaled, they face challenges in reducing source-to-drain resistance (Rsd), off-state current (Ioff), and threshold voltage (Vt), with existing methods failing to simultaneously achieve both scaling and performance improvement in metal oxide semiconductor (MOS) transistors with extended drain regions.
Innovation Solution
The introduction of carbon, nitrogen, and fluorine co-implants in the diffusion suppression implant region of semiconductor devices, specifically in the body region under the gate electrode, to suppress dopant out-diffusion and parasitic bipolar transistor activation, thereby enhancing the operating characteristics of drain extended MOSFETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If device scaling is performed to reduce transistor size, then device integration density improves, but source-to-drain resistance increases and performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a diffusion suppression implant region with specific carbon, nitrogen, and fluorine concentrations in the body region under the gate electrode, while maintaining different doping characteristics in other regions. This localized modification suppresses dopant out-diffusion at the critical interface without affecting overall device scaling, thereby reducing source-to-drain resistance while maintaining small transistor dimensions.
Solution Approach 2:
The patent implements preliminary action by performing carbon, nitrogen, and fluorine co-implantation into the body region before final device operation. This pre-treatment creates a diffusion barrier that prevents future dopant migration, ensuring stable electrical characteristics and low resistance throughout the device lifecycle without requiring larger dimensions.
2Reliability
If dopant concentration is increased to reduce resistance, then source-to-drain resistance decreases, but parasitic bipolar transistor activation increases
Solution Approach 1:
The patent uses carbon, nitrogen, and fluorine atoms as intermediary elements implanted into the body region. These intermediaries form a diffusion barrier that decouples the relationship between dopant concentration and parasitic bipolar activation. The barrier allows high dopant concentrations in source/drain regions for low resistance while preventing the lateral diffusion that would create parasitic bipolar transistors, thus resolving the contradiction.
Solution Approach 2:
The patent converts the potentially harmful effect of dopant diffusion into a beneficial outcome by using carbon, nitrogen, and fluorine co-implantation to create a controlled diffusion barrier. This barrier prevents unwanted parasitic bipolar transistor formation while allowing the desired high dopant concentration in source/drain regions, transforming what would be a harmful diffusion process into a controlled and beneficial doping profile.
3Area of moving object
If device dimensions are reduced for scaling, then integration density improves, but off-state current increases
Solution Approach 1:
The patent applies local quality by implementing carbon, nitrogen, and fluorine co-implantation specifically in the body region under the gate electrode, creating a localized diffusion suppression zone. This localized treatment maintains sharp doping profiles and prevents lateral dopant spread that would increase off-state current, enabling small device dimensions with保持良好的关断特性.
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 significantly reduces source-to-drain resistance, improves off-state current, and stabilizes threshold voltage, increasing the safe operating area and reliability of the devices by suppressing parasitic bipolar transistor activation and dopant out-diffusion.
Implementation Method 1
At least one of carbon, nitrogen, and fluorine is implanted into the body region
Implementation Method 2
The diffusion suppression implant region includes a body region having the second opposite conductivity type and comprises at least one of carbon, nitrogen, and fluorine
Data Source
AI summary
A semiconductor device including drain extended metal oxide semiconductor field effect transistor (MOSFET) includes a source region and a drain region each having a first dopant type spaced apart along a surface of a semiconductor material having a second opposite conductivity type. A gate electrode over the semiconductor material surface between the source region and the drain region. A diffusion suppression implant region in the semiconductor material extends from the source region under the gate electrode. The diffusion suppression implant region includes a body region having the second opposite conductivity type and comprises at least one of carbon, nitrogen, and fluorine.