Semiconductor Buffer Layer Gradient for Surge Voltage
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving high withstand voltage, maintaining productivity, and suppressing surge voltage in turned-off or recovery states due to incomplete donor layer formation and reduced depletion layer stopping, leading to defect regions and decreased voltage withstand.
Innovation Solution
A semiconductor device design featuring a semiconductor substrate with a drift layer, a first diffusion layer, a high-concentration first buffer layer, and a second buffer layer with a peak concentration higher than the first buffer layer, where the second buffer layer's length is greater than five times the first buffer layer's length, ensuring effective impurity concentration distribution to prevent defect regions and enhance voltage withstand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-stage injection or high-concentration injection is carried out to prevent defect region formation, then defect regions are suppressed, but productivity deteriorates
Solution Approach 1:
The invention changes the impurity concentration parameter by creating a gradient distribution where the impurity concentration gradually decreases from the deep buffer layer toward the drift layer. This gradient structure allows the depletion layer to be effectively stopped without requiring multi-stage or high-concentration injection, thus maintaining high productivity while preventing defect regions.
Solution Approach 2:
The invention applies local quality by creating different impurity concentration zones within the buffer layer. The deep buffer layer has higher impurity concentration to stop the depletion layer, while the region toward the drift layer has gradually decreasing concentration to prevent defect formation. This localized variation in impurity concentration resolves the contradiction between defect suppression and productivity.
2Object-affected harmful factors
If the depletion layer is stopped in the deep buffer layer, then surge voltage is suppressed, but withstand voltage is reduced
Solution Approach 1:
The invention changes the impurity concentration parameter by implementing a gradient distribution that gradually decreases from the deep buffer layer toward the drift layer. This allows the depletion layer to be stopped in the high-concentration deep buffer layer for surge voltage suppression, while the gradual transition prevents abrupt electric field changes that would reduce withstand voltage.
Solution Approach 2:
The gradient impurity concentration profile acts as an intermediary between the deep buffer layer and the drift layer. It provides a smooth transition zone that allows the depletion layer to be stopped effectively while maintaining electric field distribution that preserves withstand voltage, thus mediating between surge voltage suppression and withstand voltage requirements.
3Object-affected harmful factors
If a buffer layer is formed to stop the depletion layer at a predetermined depth, then surge voltage is suppressed, but defect regions are generated when the donor layer cannot be fully formed
Solution Approach 1:
The invention changes the impurity concentration parameter by creating a gradient that gradually decreases from the deep buffer layer toward the drift layer. This gradient ensures that the donor layer is fully formed throughout the buffer region, preventing defect formation while still allowing the depletion layer to be stopped at the predetermined depth for surge voltage suppression.
Solution Approach 2:
The invention applies preliminary action by pre-forming the gradient impurity concentration profile in the buffer layer before operation. This gradient structure proactively prevents defect region formation by ensuring complete donor layer formation, while simultaneously enabling effective depletion layer stopping for surge voltage suppression.
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 design achieves improved productivity, increased withstand voltage, and effective suppression of surge voltage by preventing defect regions and optimizing depletion layer stopping, while maintaining high impurity concentration and reduced leak current.
Implementation Method 1
When a reverse bias is applied to a vertical semiconductor device, a depletion layer extends toward a back surface from an interface between a P-type region and an N-type drift layer
Implementation Method 2
a first buffer layer of the first conductive type provided between the drift layer and the second diffusion layer, having a concentration higher than that of the drift layer, and into which a proton is injected
Data Source
AI summary
A semiconductor device includes: a semiconductor substrate including a front surface, a back surface that is opposite to the front surface, and a drift layer of a first conductive type disposed between the front surface and the back surface; a first diffusion layer of a second conductive type provided between the drift layer and the front surface; a second diffusion layer provided between the drift layer and the back surface; a first buffer layer of the first conductive type provided between the drift layer and the second diffusion layer, having a concentration higher than that of the drift layer, and into which a proton is injected; and a second buffer layer of the first conductive type provided between the first buffer layer and the second diffusion layer and having a concentration higher than that of the drift layer, wherein a peak concentration of the second buffer layer is higher than a peak concentration of the first buffer layer, an impurity concentration of the first buffer layer gradually decreases toward the back surface, a length from a peak position of the first buffer layer to a boundary between the drift layer and the first buffer layer is represented by Xa, a length from the peak position to a boundary between the first buffer layer and the second buffer layer is represented by Xb, and Xb>5 Xa.