Hydrogen Buffer Region Structure for Stable Carrier Profiles
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Solution Overview
Problem
In semiconductor devices with a proton buffer region formed in a substrate having an oxygen concentration of 1E16 to 6E17 atoms/cm3, the buffer effect decreases, leading to formation anomalies, increased leakage current, and oscillation issues due to undefined oxygen concentration from the buffer region to the cathode layer.
Innovation Solution
A semiconductor device with a hydrogen buffer region and a flat region, both having constant oxygen concentrations of 1E16 to 6E17 atoms/cm3, is formed on the back surface side of a semiconductor substrate, along with a carrier injection layer, using proton injection and thermal activation to prevent high-resistance layer formation and ensure proper carrier concentration profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a proton buffer region is formed in one step into a semiconductor substrate having an oxygen concentration of 1E16 atoms/cm3 to 6E17 atoms/cm3 inclusive, then throughput is increased, but buffer effect decreases and formation anomaly of carrier concentration profile occurs
Solution Approach 1:
The invention divides the buffer region formation into two separate regions: a hydrogen buffer region formed by proton injection and a flat region formed by oxygen precipitation. This segmentation allows each region to perform its specific function independently, preventing the formation anomalies that occur when attempting to create a single buffer region in one step.
Solution Approach 2:
The invention controls the oxygen concentration parameter within a specific range (1E16 to 6E17 atoms/cm3) to enable proper oxygen precipitation in the flat region. By adjusting oxygen concentration as a key parameter, the invention ensures that the flat region forms with appropriate electrical characteristics, preventing buffer effect degradation while maintaining throughput.
2Loss of time
If a proton buffer region is formed in one step, then manufacturing time is reduced, but leakage current increases
Solution Approach 1:
The invention segments the buffer region into a hydrogen buffer region and a flat region, where the flat region specifically addresses leakage current through controlled oxygen precipitation. This segmentation maintains manufacturing efficiency while eliminating the harmful leakage current effect.
Solution Approach 2:
The flat region acts as an intermediary between the hydrogen buffer region and the drift region, providing a transition zone that prevents leakage current. The oxygen precipitates in this intermediate region create a depletion layer that blocks harmful current paths while maintaining the overall buffer function.
3Device complexity
If a proton buffer region is formed in one step, then process complexity is reduced, but oscillation at turn-off occurs
Solution Approach 1:
The invention segments the buffer region formation process into distinct zones (hydrogen buffer region and flat region) that can be created through coordinated proton injection and oxygen precipitation. This segmentation provides the necessary structural complexity to prevent oscillation while maintaining overall process simplicity.
Solution Approach 2:
By controlling oxygen concentration and thermal treatment parameters, the invention creates a flat region with specific electrical characteristics that prevent oscillation at turn-off. The parameter control enables reliable device operation without significantly increasing process complexity.
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 configuration prevents the generation of high-resistance layers, reduces dynamic abrupt changes in the depleted layer, decreases surge voltage, and prevents oscillation by maintaining a stable carrier concentration profile and reducing leakage current.
Implementation Method 1
an injection step of injecting protons within a depth of 10 μm from the back surface of the semiconductor substrate
Implementation Method 2
an activation step of activating the protons injected in the injection step through thermal treatment at 400° C.
Implementation Method 3
The hydrogen buffer region and the flat region each have a constant oxygen concentration of 1E16 atoms/cm3 to 6E17 atoms/cm3 inclusive
Data Source
AI summary
A semiconductor device includes a drift region that is of first conductive type and formed in a semiconductor substrate; a hydrogen buffer region that is of first conductive type, positioned on the back surface side of the drift region, contains hydrogen as impurities, and has impurity concentration higher than impurity concentration of the drift region; a flat region that is of first conductive type, positioned on the back surface side of the hydrogen buffer region, and has impurity concentration higher than impurity concentration of the drift region; and a carrier injection layer that is of first or second conductive type, positioned on the back surface side of the flat region, and has impurity concentration higher than impurity concentrations of the hydrogen buffer region and the flat region. The hydrogen buffer region and the flat region each have a constant oxygen concentration of 1E16 atoms/cm3 to 6E17 atoms/cm3 inclusive.