Power Transistor Terminal Trenches for High Voltage Isolation
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Solution Overview
Problem
High voltage operations in semiconductor devices lead to reduced breakdown voltage and current leakage due to heightened electrical field density between the peripheral and transistor regions, which existing isolation schemes fail to adequately address.
Innovation Solution
The semiconductor device employs an isolation scheme with orthogonal staggering patterns of terminal trenches and super junction structures with reduced surface field (RESURF) capabilities to reduce stacking faults and enhance breakdown voltage, thereby minimizing current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures with terminal trenches are formed around power transistors, then low voltage transistors are protected from high voltage operations, but junction breakdown voltage is reduced and current leakage increases
Solution Approach 1:
The patent applies different trench configurations at different locations: terminal trenches are formed in the peripheral region while body trenches are formed in the transistor region. The terminal trenches have specific depth and width characteristics that differ from body trenches, allowing optimized local protection without compromising overall breakdown voltage
Solution Approach 2:
The isolation structure is segmented into multiple components: terminal trenches in the peripheral region, body trenches in the transistor region, and intermediate trenches connecting them. This segmentation allows each region to be optimized independently for its specific function while maintaining overall system reliability
2Device complexity
If terminal trenches are formed in the peripheral region, then isolation is provided, but electrical field density increases at junctions causing reduced breakdown voltage
Solution Approach 1:
Intermediate trenches are introduced as mediator structures between the terminal trenches in the peripheral region and the body trenches in the transistor region. These intermediate trenches help distribute and reduce the electrical field density at the junctions, preventing field concentration that would lead to breakdown
Solution Approach 2:
The patent extends the isolation concept into the vertical dimension by forming trenches with specific depth characteristics. The terminal trenches extend to a first depth, body trenches extend to a second depth, and intermediate trenches provide gradual transition, utilizing the depth dimension to manage electrical field distribution
Data Source
AI summary
A device includes a transistor formed on a substrate. The transistor includes an n-type drain contact layer, an n-type drain layer, an oxide layer, a p-type body region, a p-type terminal region, body trenches, and terminal trenches. The n-type drain contact layer is near a bottom surface of the substrate. The n-type drain layer is positioned on the n-type drain contact layer. The oxide layer circumscribes a transistor region. The p-type body region is positioned within the transistor region. The p-type terminal region extends from under the oxide layer to an edge of the transistor region, thereby forming a contiguous junction with the p-type body region. The body trenches is within the transistor region and interleaves with the p-type body region, whereas the terminal trenches is outside the transistor region and interleaves with the p-type terminal region.