SiC Semiconductor Contact Structure for Low Resistance
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Solution Overview
Problem
Establishing a satisfactory ohmic contact between silicon carbide (SiC) semiconductor regions and electrodes is challenging due to the high Schottky barrier height and the difficulty in using single metal materials to achieve low contact resistivity for both electrons and holes, while also maintaining a reduced contact area to improve power density.
Innovation Solution
The semiconductor device incorporates a first contact region with a U-shaped cross-section that provides three-dimensional contact between the electrode and the p-type well region, and a second contact region with a Ni silicide layer, along with an intermediate layer like Ti or TiN, to establish ohmic contacts between the electrode and both the p-type and n-type semiconductor regions, enhancing avalanche resistance and reducing parasitic resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single metal material is used to establish contact with SiC semiconductor regions, then the device structure is simple, but it is difficult to achieve low contact resistivity for both electrons and holes due to high Schottky barrier height
Solution Approach 1:
An intermediate layer (such as Ti, TiN, or other metals) is introduced between the electrode and the SiC semiconductor regions. This intermediate layer serves as a mediator that facilitates ohmic contact by reducing the Schottky barrier height, enabling low contact resistivity for both n-type and p-type regions without requiring complex multi-material structures
Solution Approach 2:
The contact structure employs composite material composition with multiple layers (intermediate layer + electrode material) to achieve properties that single materials cannot provide. The intermediate layer is specifically selected to have appropriate work function and chemical compatibility with SiC, creating a composite contact system that delivers low contact resistivity
2Reliability
If the contact area is increased to reduce contact resistance, then the contact resistance decreases, but the power density is reduced
Solution Approach 1:
The invention changes the material parameters of the contact structure by introducing an intermediate layer with specific electrical and chemical properties. This parameter change enables achieving low contact resistance through material selection rather than increasing contact area, thereby maintaining high power density
3Reliability
If the electrode directly contacts the p-type well region, then the structure is simple, but the potential in the p-type well region becomes unstable and avalanche resistance is reduced
Solution Approach 1:
The intermediate layer acts as a mediator between the electrode and the p-type well region, providing stable electrical contact and preventing direct metal-semiconductor interaction that would cause potential instability. This intermediate contact structure enhances avalanche resistance by ensuring proper potential distribution in the p-type well region
Solution Approach 2:
The contact structure is designed with local quality differentiation where the intermediate layer is specifically positioned at the electrode-p-type well interface to provide localized potential control and stability, while other regions of the device maintain their original structural characteristics
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
The solution effectively reduces contact resistance, stabilizes the potential in the p-type well region, and enhances avalanche resistance by allowing efficient discharge of holes during the OFF state, improving the on-state resistance and power density of the semiconductor device.
Implementation Method 1
a second contact region, and a first intermediate layer. The first intermediate layer is provided between the first electrode and the first contact region, and between the first electrode and the second contact region
Implementation Method 2
enhancing avalanche resistance by allowing efficient discharge of holes during the OFF state
Data Source
AI summary
According to one embodiment, a semiconductor device includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type, a third semiconductor region of a first conductivity type, a first electrode, and a contact region. The second semiconductor region is provided on the first semiconductor region. The third semiconductor region is provided on the second semiconductor region. The first electrode has a first and a second portion. The first portion is provided in a first direction and has a lower end being positioned below a lower end of the third semiconductor region. The second portion is in contact with the first portion and is provided on the third semiconductor region. The contact region is provided between the first portion and the second semiconductor region and is electrically connected to the first electrode and the second semiconductor region.