Guard Ring Column Layout for MOSFET Breakdown Voltage
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Solution Overview
Problem
The challenge is to maintain a high breakdown voltage in semiconductor devices while increasing the impurity concentration of the drift layer to reduce the on-resistance of MOSFETs, without excessively lowering the breakdown voltage.
Innovation Solution
The semiconductor device incorporates a guard ring part with multiple guard rings and guard ring column regions in the outer peripheral region, where the guard ring column regions have a narrower width than the guard rings, allowing for improved breakdown voltage and proper connection even with misalignment during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the impurity concentration of the drift layer is increased to reduce on-resistance, then the on-resistance decreases, but the breakdown voltage is excessively lowered
Solution Approach 1:
The guard ring part is segmented into multiple guard rings formed at different positions in the drift layer, with each guard ring having guard ring column regions extending downward. This segmentation allows the electric field to be distributed and controlled at multiple levels, enabling the drift layer to have higher impurity concentration while maintaining breakdown voltage through the segmented guard ring structure.
Solution Approach 2:
The guard ring column regions have a narrower width than the guard rings themselves, creating a local quality difference. This narrow column structure concentrates the electric field control in specific vertical regions, allowing the drift layer to achieve lower on-resistance while the localized guard ring column structure maintains the necessary breakdown voltage characteristics.
2Reliability
If guard rings are formed in the drift layer to improve breakdown voltage, then the breakdown voltage increases, but the manufacturing precision is reduced due to misalignment issues
Solution Approach 1:
The guard ring column regions are formed first, extending downward from the drift layer surface. Then the guard rings are formed in the drift layer at different positions. This preliminary formation of the column regions provides a robust structural foundation that maintains proper electrical connection even when there is misalignment during subsequent guard ring formation, thereby reducing manufacturing precision requirements.
Solution Approach 2:
The guard ring column regions act as an intermediary structure between the guard rings and the substrate. This intermediate structure provides a buffer zone that accommodates misalignment, ensuring that the guard rings remain properly connected to the substrate through the column regions even when positioning is not perfectly precise, thus reducing the impact of manufacturing variability.
Data Source
AI summary
A semiconductor device has a cell region formed with a semiconductor element and an outer peripheral region surrounding the cell region. The outer peripheral region includes a guard ring part having a plurality of guard rings of the second conductivity-type, and a plurality of guard ring column regions of the second conductivity-type. Each of the guard rings is disposed in a surface layer portion of the drift layer and has a frame shape surrounding the cell region. The guard ring column regions are extended from the guard rings toward the substrate. Each of the guard ring column regions has a width smaller than a width of each of the guard rings in a direction along a planar direction of the substrate in a predetermined cross-section defined along the cell region and the outer peripheral region. At least two guard ring column regions are provided for each guard ring.