MOSFET Co-Implants for Low Resistance and Dopant Diffusion Control
Find Innovative SolutionsGenerate Solutions
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 issues such as dopant out-diffusion leading to early device failure and parasitic bipolar transistor activation, which affect performance and reliability.
Innovation Solution
The use 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 enhance transistor performance by forming a more abrupt junction and limiting boron diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional doping methods are used to reduce source-to-drain resistance, then resistance decreases, but dopant out-diffusion occurs leading to early device failure
Solution Approach 1:
Carbon, nitrogen, and fluorine are introduced as intermediary elements that form a diffusion barrier between the dopant regions. These elements preferentially occupy lattice sites and create a physical/chemical barrier that prevents boron atoms from diffusing out of the intended implant region, thereby maintaining sharp junctions without requiring extremely precise implantation conditions
Solution Approach 2:
The patent employs co-implantation of multiple elements (carbon, nitrogen, fluorine) together with boron dopant. This creates a composite doped region where the different elements work synergistically: carbon and nitrogen form diffusion barriers while fluorine passivates dangling bonds and reduces defect formation, collectively improving both resistance and diffusion control
2Productivity
If device scaling is pursued to improve performance metrics, then device density increases, but parasitic bipolar transistor activation occurs
Solution Approach 1:
The patent converts the potentially harmful high dopant concentrations required for low resistance into a beneficial effect by using carbon/nitrogen/fluorine co-implantation. The carbon and nitrogen form a diffusion barrier that confines the dopant, while fluorine passivates defects, allowing high dopant doses to be used without activating parasitic bipolar transistors, thus turning what would be a harmful condition into a beneficial low-resistance state
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 the resistance, improves off-state current, and increases the safe operating area by suppressing parasitic bipolar transistor activation, thereby enhancing the overall performance and reliability of semiconductor devices.
Implementation Method 1
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
Implementation Method 2
At least one of carbon, nitrogen, and fluorine is implanted into the body region
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.