MOS Device Doped Region Segmentation for Threshold Stability
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Solution Overview
Problem
Conventional MOS devices suffer from unstable electronic characteristics due to the hot carrier effect and threshold voltage roll-off effect, which affect their performance.
Innovation Solution
The MOS device design includes a semiconductor layer, an isolation structure, a well region, a gate with a dielectric and conductive layer, and lightly doped regions formed using self-aligned processes to create a deeper first lightly doped region and a shallower second lightly doped region, optimizing the inversion current channel and reducing on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lightly doped regions are formed using the gate as a mask, then the device structure is simple, but the threshold voltage roll-off effect and hot carrier effect cause unstable electronic characteristics
Solution Approach 1:
The lightly doped region is divided into two distinct parts: a first lightly doped region formed deeper in the semiconductor layer and a second lightly doped region formed shallower. This segmentation allows each region to perform different functions - the first region reduces the short channel effect and threshold voltage roll-off, while the second region controls hot carrier effects, thereby improving overall device reliability without requiring complex additional structures
Solution Approach 2:
Different doping concentrations and depths are applied at different locations within the lightly doped region. The first lightly doped region has a deeper penetration depth and different doping characteristics compared to the second lightly doped region. This local differentiation optimizes the electrical characteristics at specific locations - reducing threshold voltage roll-off near the drain while controlling hot carrier effects in other areas
2Productivity
If the channel length is reduced to improve device integration, then productivity increases, but the short channel effect and threshold voltage roll-off worsen
Solution Approach 1:
The invention changes the doping parameters by creating a first lightly doped region with specific depth and concentration characteristics that differ from conventional single-region designs. By adjusting the doping depth, concentration, and distribution of the first and second lightly doped regions, the device maintains stable threshold voltage even with reduced channel length, enabling higher integration density without sacrificing reliability
3Loss of energy
If the on-resistance is reduced to improve device performance, then power consumption decreases, but the threshold voltage roll-off effect increases
Solution Approach 1:
By optimizing the doping concentration and depth parameters of the first and second lightly doped regions, the invention achieves a balance where on-resistance is reduced for lower power consumption, while the threshold voltage roll-off effect is simultaneously suppressed. The first lightly doped region's deeper structure reduces resistance, while its specific doping profile maintains threshold voltage stability
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 design alleviates the threshold voltage roll-off effect without increasing on-resistance, enhancing the stability and performance of the MOS device by increasing breakdown voltage and reducing the short channel effect.
Implementation Method 1
implanting N-type impurities in the form of accelerated ions into the operation region 14 by an angle α with reference to a vertical direction
Data Source
AI summary
A metal oxide semiconductor (MOS) device includes: a semiconductor layer, an isolation structure, a well, a gate, a source, a drain, a first lightly doped region, and a second lightly doped region. The first lightly doped region is located right below a spacer layer and a portion of a dielectric layer of the gate. In a channel direction, the first lightly doped region is between and contacts the drain and an inversion current channel. The second lightly doped region includes a first part and a second part. The first part is located right below the spacer which is near the source, and the first part is between and contacts the source and the inversion current channel. The second part is located right below the spacer which is near the drain, and the second part is between and contacts the drain and the first lightly doped region.