Semiconductor Trench Field Control via Impurity Grading
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Solution Overview
Problem
Conventional semiconductor devices face issues with concentrated electrical fields at the bottom of trenches due to comparable impurity concentrations in semiconductor layers, leading to potential breakdowns and reduced breakdown voltage.
Innovation Solution
A semiconductor device design featuring a first semiconductor layer with a trench and a second semiconductor layer on the inner wall, where the second layer has a lower impurity concentration and extends to the edge of the first layer, along with an oxide region and trench insulating and electrode structures, which reduces electrical field strength and improves breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the impurity concentration of the semiconductor layer is maintained at a level comparable to the epitaxial layer, then the electrical field concentrates on the bottom of the trench, but this leads to reduced breakdown voltage and potential device failures
Solution Approach 1:
The patent applies local quality by creating a second semiconductor layer with specifically controlled lower impurity concentration (3.2E14 to 4.5E16 cm^-3) compared to the first layer (4E14 to 7E16 cm^-3). This localized modification of impurity concentration in the region adjacent to the trench bottom effectively distributes the electrical field, preventing concentration at the trench bottom while maintaining overall device performance.
Solution Approach 2:
The patent changes the impurity concentration parameter of the semiconductor layer to resolve the electrical field concentration issue. By reducing the impurity concentration in the second semiconductor layer formed on the trench inner wall, the electrical field distribution is fundamentally altered, preventing breakdown at the trench bottom while maintaining adequate conductivity for device operation.
2Reliability
If a second semiconductor layer with lower impurity concentration is formed on the trench inner wall, then electrical field strength is reduced and breakdown voltage is improved, but the device structure becomes more complex
Solution Approach 1:
The patent segments the semiconductor layer into two distinct regions: a first semiconductor layer with higher impurity concentration and a second semiconductor layer with lower impurity concentration formed on the trench inner wall. This segmentation allows each region to perform its specific function - the first layer provides overall conductivity while the second layer specifically manages electrical field distribution at the trench region, achieving breakdown voltage improvement through structured division.
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 effectively lowers electrical field strength and enhances breakdown voltage by extending the depletion layer, allowing for more robust and reliable semiconductor performance.
Implementation Method 1
the second semiconductor layer containing impurities of the first conductivity type at a lower concentration than the first semiconductor layer... effectively lowers electrical field strength and enhances breakdown voltage by extending the depletion layer
Data Source
AI summary
A semiconductor layer may be subjected to etching to form a trench therein. An epitaxial layer may be further formed in the trench. Here, the impurity concentration of the epitaxial layer is controlled to be lower than that of the semiconductor layer. In this manner, concentration of electrical fields in the trench is reduced. A first innovations herein provides a semiconductor device including a first semiconductor layer containing impurities of a first conductivity type, a trench provided in the first semiconductor layer on a front surface side thereof, and a second semiconductor layer provided on an inner wall of the trench, where the second semiconductor layer contains impurities of the first conductivity type at a lower concentration than the first semiconductor layer.