Semiconductor Electrode Structure for Hole Injection and Breakdown Control
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Solution Overview
Problem
Semiconductor devices used in power conversion devices face challenges in achieving a balance between reducing switching loss and enhancing breakdown resistance, particularly due to issues with hole injection and thermal diffusion affecting the contact area ratio of semiconductor layers.
Innovation Solution
The semiconductor device incorporates a design with third electrodes and contact trenches that electrically insulate the semiconductor part, controlling hole injection and preventing thermal diffusion by arranging third semiconductor layers to minimize contact area changes, thereby optimizing the contact ratio and reducing forward current concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the contact area ratio of semiconductor layers is increased to reduce switching loss, then switching loss is reduced, but thermal diffusion increases causing reliability degradation
Solution Approach 1:
The patent applies local quality by creating distinct regions with different impurity concentrations and types. Specifically, it forms a first semiconductor layer with a first conductivity type and a second semiconductor layer with a second conductivity type, where each layer has locally optimized properties. The third semiconductor layer is selectively formed in certain regions to control hole injection locally, allowing the contact area ratio to be optimized for low switching loss while maintaining reliability in critical regions through localized property variations.
Solution Approach 2:
The patent employs parameter changes by varying impurity concentration and conductivity type across different semiconductor layers. The third semiconductor layer is formed with a higher impurity concentration than the second semiconductor layer, and the first and second layers have opposite conductivity types. These parameter variations enable independent optimization of switching characteristics and breakdown resistance, resolving the contradiction between reducing switching loss and maintaining reliability.
2Reliability
If hole injection is increased to improve conductivity, then electrical performance is improved, but thermal diffusion increases affecting contact area stability
Solution Approach 1:
The patent applies preliminary action by pre-forming the third semiconductor layer with a higher impurity concentration in specific regions before final device operation. This third layer is selectively positioned to control hole injection in advance, preventing excessive thermal diffusion during operation. The preliminary structuring of impurity distribution ensures that hole injection is optimized for conductivity while maintaining contact area ratio stability during device operation.
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 design effectively reduces switching loss and improves breakdown resistance by controlling hole injection and preventing thermal diffusion, ensuring efficient operation of power conversion devices.
Implementation Method 1
The plurality of third electrodes are provided inside a first trench extending into the first semiconductor layer from a front surface of the semiconductor part at the second electrode side. The plurality of third electrodes include a first-third electrode and a second-third electrode. The second semiconductor layer is provided between the first-third electrode and the second-third electrode. The second semiconductor layer faces the first-third electrode and the second-third electrode respectively via the first insulating film.
Implementation Method 2
The third semiconductor layer includes a second conductivity type impurity with a concentration higher than a concentration of a second conductivity type impurity in the second semiconductor layer. The third semiconductor layer is provided between the contact portion of the second electrode and the second-third electrode. The third semiconductor layer faces the second-third electrode via the first insulating film.
Data Source
AI summary
A semiconductor device includes a semiconductor part, first and second electrodes and first-third and second-third electrodes. The semiconductor part is provided between the first and second electrodes. The semiconductor part includes a first semiconductor layer of a first conductivity type, second and third semiconductor layers of a second conductivity type. The second and third semiconductor layers are arranged between the first layer and the second electrode. The first-third and second-third electrodes are provided in the semiconductor part. The second semiconductor layer is provided between the first-third electrode and the second-third electrode. The second electrode includes a contact portion extending into the second semiconductor layer. The third semiconductor layer is provided on the second semiconductor layer between the contact portion and the second-third electrode. The second semiconductor layer includes a first portion facing the third semiconductor layer via the contact portion.