Semiconductor Guard Trenches With Intermediate Voltage Isolation
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Solution Overview
Problem
Existing semiconductor devices struggle to effectively isolate high voltage regions from low voltage regions on semiconductor chips, leading to potential breakdown across surface junctions, especially when the voltage difference is large.
Innovation Solution
A guard structure comprising a first layer of a first type of semiconductor in contact with a second layer of a second type of semiconductor, with trenches between high and low voltage regions to isolate them, and an intermediary voltage applied to a sub-region between the trenches to split the voltage drop and prevent breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single trench is used to isolate high voltage region from low voltage region, then the structure is simple, but breakdown occurs across the trench when voltage difference is large
Solution Approach 1:
The isolation structure is segmented into multiple trenches (first trench and second trench) instead of using a single trench. This segmentation divides the voltage drop across multiple barriers, reducing the electric field strength at each individual trench interface and preventing breakdown even when the overall voltage difference is large.
Solution Approach 2:
A sub-region of the second layer is introduced as an intermediary between the high voltage region and low voltage region. This intermediary sub-region is isolated from both high and low voltage regions by the trenches, allowing it to assume an intermediate voltage potential that further reduces the voltage gradient across each trench interface.
2Reliability
If guard ring structure is used to prevent voltage breakdown, then breakdown prevention is improved, but current leakage occurs through the semiconductor layer below the rings
Solution Approach 1:
The harmful conductive path through the semiconductor layer is extracted and removed by forming trenches that extend through the second layer. This eliminates the continuous material path that would allow current leakage, while the trenches themselves provide the isolation barrier.
3Reliability
If trench isolation is used between high voltage and low voltage regions, then isolation effectiveness is improved, but breakdown across the trench occurs with large voltage differences
Solution Approach 1:
The isolation structure is segmented into multiple trenches (first trench and second trench) instead of using a single trench. This segmentation divides the voltage drop across multiple barriers, reducing the electric field strength at each individual trench interface and preventing breakdown even when the overall voltage difference is large.
Solution Approach 2:
A sub-region of the second layer is introduced as an intermediary between the high voltage region and low voltage region. This intermediary sub-region is isolated from both high and low voltage regions by the trenches, allowing it to assume an intermediate voltage potential that further reduces the voltage gradient across each trench interface.
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 proposed solution effectively isolates high voltage regions from low voltage regions by splitting the voltage drop across multiple trenches, thereby preventing breakdown and ensuring reliable operation even with large voltage differences.
Implementation Method 1
the intermediary voltage having a value between the voltages of the respective high and low voltage regions... splitting the voltage drop across multiple trenches
Data Source
AI summary
A structure and method for guarding a high voltage region at a semiconductor surface from a low voltage region at the semiconductor surface. The structure comprising at least two trenches between the high and low voltage regions to isolate the high voltage region from the low voltage region. The trenches are spaced apart so as to define a sub-region therebetween. To prevent breakdown across the trenches, an intermediate voltage, i.e., of a value between the voltages of the high and low voltage regions, is applied to the sub-region so as to reduce the voltage drop across each trench. Preferably this is achieved by providing an integrated voltage divider circuit that connects between the high and low voltage regions and has an output connected to the sub-region by which the intermediate voltage is applied to the sub-region.