MOSFET Channel Structure for Threshold Voltage Stability
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Solution Overview
Problem
Semiconductor devices, such as MOSFETs and IGBTs, face challenges in maintaining small characteristic fluctuations, particularly in the threshold voltage of the gate electrode, due to p-type impurity diffusion affecting the on-resistance and channel formation.
Innovation Solution
Incorporating a third semiconductor region with a higher concentration of elements like carbon, germanium, or antimony between the second semiconductor region and the gate insulating layer to suppress p-type impurity diffusion, thereby stabilizing the threshold voltage and reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional semiconductor structure is used, then the manufacturing process is simple, but the threshold voltage fluctuates due to p-type impurity diffusion
Solution Approach 1:
The second semiconductor region is divided into three distinct portions (first, second, and third portions) with different impurity concentrations and compositions. This segmentation allows each portion to serve a specific function: the first portion provides base conductivity, the second portion creates the channel region, and the third portion acts as a barrier to p-type impurity diffusion toward the gate electrode, thereby stabilizing threshold voltage.
Solution Approach 2:
Different portions of the second semiconductor region are assigned different local qualities through varying impurity concentrations and elemental compositions. The third portion specifically has a higher concentration of first conductivity type impurities and contains elements like carbon, germanium, antimony, or indium to create a localized region that resists p-type impurity diffusion, while other portions maintain different properties for their specific functions.
2Reliability
If the second semiconductor region has high impurity concentration, then electrical resistance is reduced, but threshold voltage fluctuation increases
Solution Approach 1:
The second semiconductor region is segmented into three portions with progressively higher impurity concentrations from the first to the third portion. This segmentation enables the third portion to act as a diffusion barrier with high impurity concentration to prevent p-type impurity migration, while the first and second portions maintain lower concentrations suitable for channel formation and base conductivity.
Solution Approach 2:
The second semiconductor region is formed as a composite structure with three portions having different impurity compositions and concentrations. The third portion contains elements (carbon, germanium, antimony, or indium) at higher concentrations than the other portions, creating a composite material that provides both electrical conductivity and diffusion barrier properties.
3Ease of manufacture
If p-type impurity diffusion is allowed, then manufacturing is easier, but on-resistance and threshold voltage are affected
Solution Approach 1:
The third portion of the second semiconductor region is pre-formed with high first conductivity type impurity concentration and specific elemental composition (carbon, germanium, antimony, or indium) before final device operation. This preliminary structure acts as a pre-established barrier that prevents p-type impurity diffusion during subsequent processing and operation, eliminating the need for complex diffusion control measures.
Solution Approach 2:
The third portion of the second semiconductor region serves as an intermediary barrier between the gate electrode and the bulk of the second semiconductor region. This intermediate layer with high impurity concentration and specific elemental composition intercepts and blocks p-type impurity diffusion paths, protecting the gate region while maintaining overall device functionality.
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 fluctuation of the threshold voltage and maintains low electrical resistance by controlling p-type impurity diffusion, enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
suppress p-type impurity diffusion
Data Source
AI summary
According to one embodiment, a semiconductor device includes a first electrode, a first semiconductor region of a first conductivity type, a gate electrode, a second semiconductor region of a second conductivity type, a third semiconductor region of the first conductivity type, and a second electrode. The gate electrode is located on the first semiconductor region with a gate insulating layer interposed. The second semiconductor region faces the gate electrode via the gate insulating layer. The second semiconductor region includes: a first portion; a second portion located on the first portion and having a higher second-conductivity-type impurity concentration than the first portion; and a third portion positioned between the second portion and the gate electrode and having a higher concentration of a first element than the second portion. The first element is at least one selected from the group consisting of carbon, germanium, antimony, and indium.