Buried-Layer Isolation Layout for Semiconductor Breakdown Control
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Solution Overview
Problem
Existing semiconductor devices integrated in a common substrate face challenges in electrical isolation and breakdown voltage, particularly when multiple devices are integrated, leading to inefficiencies and potential premature breakdown.
Innovation Solution
A semiconductor device with a buried layer and elongate sinkers of opposing conductivity type, strategically positioned and doped to enhance electrical isolation and breakdown voltage, utilizing masks with specific openings for implantation and outdiffusion to optimize sinker contact resistance and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple devices are integrated in a common semiconductor substrate, then device integration density is improved, but electrical isolation between devices becomes more difficult to achieve
Solution Approach 1:
The isolation structure is segmented into multiple components: a buried layer extending through the substrate thickness, elongate sinkers positioned laterally outside device regions, and breakdown voltage influencing structures. This segmentation allows each component to contribute specifically to electrical isolation, enabling effective isolation even with high device integration density on the common substrate.
Solution Approach 2:
The isolation structure implements local quality by positioning elongate sinkers laterally outside specific device regions rather than uniformly across the substrate. The sinkers are strategically placed at locations where electrical isolation is most critical, and the breakdown voltage influencing structures are positioned adjacent to the sinkers to locally enhance isolation performance where needed.
2Reliability
If isolation structures are added to electrically separate devices, then electrical isolation is improved, but breakdown voltage decreases
Solution Approach 1:
Breakdown voltage influencing structures serve as intermediaries between the elongate sinkers and the semiconductor substrate. These structures are positioned laterally adjacent to the sinkers and modify the electric field distribution in the isolation region, preventing field concentration at the sinker-substrate interface. This intermediary structure allows the sinkers to provide electrical isolation while the influencing structure maintains higher breakdown voltage by redistributing the electric field.
3Reliability
If sinkers are positioned closer to device regions, then electrical isolation is improved, but sinker contact resistance increases
Solution Approach 1:
The elongate sinkers extend in the lateral dimension outside the device regions rather than only in the vertical dimension. By positioning sinkers laterally outside the device regions and extending them along the substrate surface, the structure provides effective electrical isolation without requiring the sinkers to be in direct contact with the device regions, thus avoiding increased contact resistance while maintaining isolation effectiveness.
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 improves electrical isolation and breakdown voltage, enabling the semiconductor device to operate at higher voltages with increased reliability and efficiency by optimizing the doping profiles and sinker positions.
Implementation Method 1
The masks are designed such that in the aligned state the ring-shaped opening in the second mask is positioned vertically above and overlaps with the opening in the first mask for the buried layer. The open areas of both masks, i.e. implant mask of buried layer and the trench mask of the first sinker may be designed to overlap
Implementation Method 2
utilizing masks with specific openings for implantation and outdiffusion to optimize sinker contact resistance and breakdown voltage
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2~3
AI summary
In an embodiment, a semiconductor device comprises a semiconductor substrate of a first conductivity type which comprises a first surface. A first device region is formed in the semiconductor substrate and has the first conductivity type. The first device region has a lateral extent that is less than the lateral extent of the first surface of the semiconductor substrate. The first device region is electrically separated from the semiconductor substrate by an isolation structure. The isolation structure comprises a buried layer which is doped with a second conductivity type that opposes the first conductivity type and further comprises a first elongate sinker of the second conductivity type. The first elongate sinker extends from the first surface into the semiconductor substrate and is in electrical contact with the buried layer. The semiconductor device further comprises a breakdown voltage influencing structure of the second conductivity type that is arranged in the semiconductor substrate and laterally adjacent the buried layer.