Semiconductor Substrate Edge Structure to Suppress Anodization
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Solution Overview
Problem
Semiconductor devices used in inverter circuits under DC or AC bias experience structural defects due to substrate anodization, leading to reduced moisture resistance and discharge prevention functions, especially in high-humidity environments, which decreases their reliability.
Innovation Solution
A semiconductor device design that includes a semiconductor substrate with a high-resistance region positioned under the protective layer's outer peripheral end, preventing anodization and structural defects by ensuring the high-resistance region does not function as an anode, thus maintaining the protective layer's integrity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective layer covers up to the end portion of the substrate, then the protective function is improved, but cracks occur in the protective layer due to damage in dicing and moisture enters through the cracks, promoting anodization
Solution Approach 1:
A metal guard ring is introduced as an intermediary element between the protective layer and the substrate end portion. The guard ring extends beyond the protective layer's end, creating a protective barrier that prevents moisture from reaching the substrate edge. This mediator structure eliminates the need for the protective layer to extend to the substrate end, avoiding cracking while maintaining protection.
2Ease of operation
If the substrate serves as the anode side under DC bias, then the device operates as intended, but the substrate portion in contact with the outer peripheral end portion of the protective film is oxidized by anodization, causing volume expansion and structural defects
Solution Approach 1:
The harmful anodization process is prevented by extracting the substrate portion from the anode function in the high-resistance region. By creating a high-resistance region at the substrate edge, electric field lines are redirected away from this area, preventing oxidation while maintaining the substrate's anode function in the active device regions.
Solution Approach 2:
The substrate is given different electrical properties in different regions. The high-resistance region at the periphery has distinct electrical characteristics compared to the bulk substrate, allowing the edge portion to be protected from anodization while the main substrate continues to function as an anode where needed.
3Reliability
If a metal guard ring covers the end portion of the substrate, then protection against moisture is improved, but there is a risk of creeping discharge in a high-humidity environment
Solution Approach 1:
The guard ring's geometric parameters are optimized to prevent creeping discharge. By controlling the guard ring's width, height, and positioning relative to the protective layer and substrate, the electric field distribution is modified to eliminate conditions that would promote surface discharge along the guard ring in humid environments.
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 solution effectively suppresses anodization and moisture ingress, enhancing the reliability of semiconductor devices by preventing structural defects and maintaining the protective layer's functionality under various biases and humidity conditions.
Implementation Method 1
when a substrate portion in contact with the outer peripheral end portion of the protective film is oxidized by anodization, the volume of the substrate portion expands
Data Source
AI summary
A semiconductor device is provided that includes a semiconductor substrate having a first main surface and a second main surface facing each other; a dielectric layer laminated on the first main surface of the semiconductor substrate; a first electrode layer laminated on the dielectric layer; and a protective layer covering at least an outer peripheral end of the dielectric layer and an outer peripheral end of the first electrode layer. Moreover, the protective layer is provided to expose an outer peripheral end on the first main surface of the semiconductor substrate. The semiconductor substrate includes a high-resistance region positioned at least directly under an outer peripheral end of the protective layer.