SiC JBS Diode Contacts for Low Forward Voltage and Surge Withstand
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices with JBS structures face challenges in achieving low forward voltage and high surge current withstand due to high contact resistance and issues with ohmic electrode formation, leading to reduced bonded surface area and increased forward voltage.
Innovation Solution
The method involves forming p+-type contact regions with high impurity concentration through thermal diffusion of aluminum atoms, which reduces contact resistance and enhances ohmic contact with titanium film Schottky electrodes, allowing for increased bonded surface area and improved surge current handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ohmic electrodes are formed on p-type regions in JBS structure, then surge current handling is improved, but contact resistance increases and forward voltage increases
Solution Approach 1:
The patent changes the impurity concentration parameter by forming high-concentration p++-type contact regions (1×10^19 to 1×10^21 atoms/cm³) compared to conventional p-type regions (1×10^16 to 1×10^18 atoms/cm³). This parameter change reduces contact resistance and forward voltage while maintaining surge current handling capability through the JBS structure.
2Loss of energy
If bonded surface area is increased to reduce forward voltage, then forward voltage decreases, but surge current withstand capability is reduced
Solution Approach 1:
The patent applies local quality by creating high-concentration p++-type contact regions specifically at the electrode contact points, while maintaining the original p-type region characteristics in other areas. This localized modification allows increased bonded surface area without compromising surge current handling, as the high-concentration regions provide low-resistance paths for forward current.
3Ease of operation
If p-type regions are formed with standard impurity concentration, then JBS structure is achieved, but contact resistance is high and forward voltage increases
Solution Approach 1:
The patent segments the p-type region formation process into two distinct regions: standard p-type regions for JBS structure formation (1×10^16 to 1×10^18 atoms/cm³) and high-concentration p++-type contact regions (1×10^19 to 1×10^21 atoms/cm³) for low-resistance contact. This segmentation allows both JBS structure functionality and low forward voltage to be achieved simultaneously.
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 results in reduced forward voltage and enhanced surge current withstand capability by forming low-resistance ohmic contacts and preventing silicide formation issues, thereby improving the overall performance of silicon carbide diodes.
Implementation Method 1
thermally diffusing aluminum atoms in the aluminum film, from a contact portion between the aluminum film and the semiconductor substrate, to the second-conductivity-type regions by a heat treatment
Implementation Method 2
by a heat treatment, to thereby form a plurality of second-conductivity-type high-concentration regions
Data Source
AI summary
A method of manufacturing a silicon carbide semiconductor device, including forming a first-conductivity-type region in a SiC semiconductor substrate, selectively forming a plurality of second-conductivity-type regions in the first-conductivity-type region, forming an interlayer insulating film covering the first-conductivity-type region and the second-conductivity-type regions, selectively removing the interlayer insulating film to form a plurality of openings exposing the second-conductivity-type regions, forming, in each opening, a layered metal film having a cap film stacked on an aluminum film, thermally diffusing aluminum atoms in the aluminum film to thereby form a plurality of second-conductivity-type high-concentration regions, removing the layered metal film, selectively removing the interlayer insulating film to form a contact hole, forming a first electrode by sequentially stacking a titanium film and a metal film containing aluminum on the first surface of the semiconductor substrate in the contact hole, and forming a second electrode on the second main surface of the semiconductor substrate.