Deep Trench Isolation Structure for High Iso BV in BCD Chips
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Solution Overview
Problem
Existing deep trench isolation (DTI) structures in Bipolar-CMOS-DMOS (BCD) technology face limitations in achieving high isolation breakdown voltage (Iso BV) and are vulnerable to process variations.
Innovation Solution
A novel DTI structure with a predetermined depth and inclination, where the width increases from the buried layer to the bottom face, is introduced. This structure includes a gap-fill insulating film and an air gap, optimizing DTI depth, width, and angle to enhance Iso BV and reduce variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a typical deep trench isolation structure is used, then the chip area is reduced compared to junction isolation, but the isolation breakdown voltage cannot be increased and is vulnerable to process variations
Solution Approach 1:
The deep trench isolation structure employs an asymmetric width profile where the trench width varies with depth. Specifically, the trench has a narrower width at the upper portion and a wider width at the lower portion, creating an asymmetric geometry that optimizes both area utilization and electrical isolation performance. This asymmetric design allows the trench to provide sufficient isolation breakdown voltage while maintaining compact chip area.
Solution Approach 2:
The invention applies local quality by providing different trench widths at different depths. The upper portion of the trench has a narrower width to save chip area, while the lower portion has a wider width to enhance isolation breakdown voltage. This localized variation in geometric properties allows each region of the trench to serve its specific function optimally.
2Reliability
If the deep trench isolation depth is increased to improve isolation breakdown voltage, then the manufacturing complexity and process variation sensitivity increase
Solution Approach 1:
The invention optimizes the isolation breakdown voltage by carefully controlling geometric parameters of the trench, specifically the width at different depths and the overall trench depth. By adjusting these parameters within optimized ranges, high isolation performance is achieved without requiring excessive trench depth that would complicate manufacturing. The asymmetric width profile is defined by specific dimensional parameters that balance performance and manufacturability.
3Reliability
If the deep trench isolation width is increased uniformly to improve isolation breakdown voltage, then the chip area occupied by isolation structures increases
Solution Approach 1:
Rather than using a uniform wide trench that would consume excessive chip area, the invention employs an asymmetric width profile where the trench is narrower at the upper portion and wider at the lower portion. This asymmetric configuration provides sufficient isolation breakdown voltage through the wider lower section while minimizing the area occupied by the narrower upper section, thus optimizing the balance between isolation performance and chip area utilization.
Solution Approach 2:
The trench width is locally optimized at different depths: the upper portion has a narrower width to conserve chip area, while the lower portion has a wider width to provide the necessary isolation breakdown voltage. This local differentiation of geometric properties ensures that area is only where needed for electrical isolation, rather than uniformly across the entire trench height.
Data Source
AI summary
A semiconductor device including: a semiconductor substrate including a buried layer; and a deep trench isolation a predetermined depth disposed starting from an upper surface of the semiconductor substrate, wherein the deep trench isolation includes: a first point disposed near the upper surface of the semiconductor substrate; a second point disposed near the buried layer; and a third point disposed near a bottom face of the deep trench isolation, and wherein the deep trench isolation has an inclination such that a width of the deep trench isolation increases from the second point to the third point, is disclosed.