Transistor Well Structure With Doping Gradients Against Punch Through
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Solution Overview
Problem
Current transistor structures face challenges in achieving optimal electrical performance and reliability due to issues like punch through, excessive doping compensation, and damage from hot carriers generated by strong electric fields.
Innovation Solution
The proposed transistor structure incorporates a substrate with adjacent first and second well regions, a gate structure, a drift region, doped regions, and an isolation structure. The well regions have specific doping concentration gradients and configurations to prevent punch through and excessive doping compensation, thereby reducing the Kirk effect and hot carrier damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform doping concentration is used in well regions, then manufacturing process is simple, but punch through occurs and electrical performance deteriorates
Solution Approach 1:
The patent applies local quality by implementing different doping concentration distributions in different regions of the well structure. Specifically, the first well region has a doping concentration that increases from top to bottom, while the second well region has a doping concentration that decreases from top to bottom. This localized variation in doping properties prevents punch through between doped regions while avoiding excessive doping compensation in the drift region, thereby resolving the contradiction between reliability and device complexity.
2Reliability
If high doping concentration is used in drift region, then electrical performance improves, but excessive doping compensation occurs and Kirk effect increases
Solution Approach 1:
The patent resolves this contradiction by creating a specific doping concentration gradient in the drift region through the interaction with adjacent well regions. The second well region's decreasing doping concentration from top to bottom, combined with the drift region's positioning, ensures that the drift region receives appropriate doping levels that improve electrical performance without causing excessive doping compensation or Kirk effect. This localized doping strategy optimizes the drift region's electrical characteristics while minimizing harmful effects.
3Speed
If strong electric field is present in drift region, then transistor switching speed improves, but hot carrier damage increases
Solution Approach 1:
The patent addresses this contradiction by carefully controlling the doping concentration parameters in the drift region and adjacent well regions. The specific doping concentration gradients (increasing in the first well region, decreasing in the second well region) modify the electric field distribution within the drift region. This parameter optimization allows the maintenance of strong electric fields necessary for fast switching while reducing the peak field strengths that would otherwise generate excessive hot carriers and cause damage.
Data Source
AI summary
A transistor structure includes a substrate, a first well region, a second well region, a gate structure, a drift region, a first doped region, a second doped region, and a first isolation structure. The first well region and the second well region are located in the substrate and adjacent to each other. The gate structure is located on the substrate. The drift region is located in the second well region on one side of the gate structure. The first doped region and the second doped region are located in the substrate on two sides of the gate structure. The first doped region is located in the first well region. The second doped region is located in the drift region. The first isolation structure is located in the substrate between the gate structure and the second doped region. The first well region has a first portion lower than a bottom surface of the drift region. The second well region has a second portion lower than the bottom surface of the drift region. A doping concentration of the first portion of the first well region is greater than a doping concentration of the second portion of the second well region.