Deep Trench Isolation Structure for High-Voltage Leakage Control
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Solution Overview
Problem
Conventional high voltage semiconductor devices face challenges in achieving deep trench isolation, leading to inadequate breakdown voltage and increased leakage current, which results in larger chip sizes and manufacturing defects due to the need for multiple mask patterns and potential cracking of air gaps.
Innovation Solution
A high voltage semiconductor device with a DTI region featuring a wide upper region and a narrow lower region, where the wide region is formed by etching after the narrow region, and an inclined surface with a gradually narrowing lateral width, minimizing step differences and eliminating the need for additional mask patterns, and using a combination of non-Bosch and Bosch processes for trench formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single etching process is used to form the DTI region, then the manufacturing process is simple, but the trench depth is insufficient leading to inadequate electrical isolation and increased leakage current
Solution Approach 1:
The etching process is divided into two sequential steps: a first etching process that forms an initial trench to a first depth, and a second etching process that extends the trench to a greater second depth. This segmentation allows each etching step to be optimized independently, achieving both sufficient trench depth for electrical isolation and process simplicity by using the same etching chemistry throughout.
2Reliability
If the DTI region is formed to achieve high breakdown voltage with sufficient depth, then electrical isolation is improved, but multiple mask patterns are required increasing manufacturing cost and complexity
Solution Approach 1:
A single mask pattern serves dual purposes: it defines the trench region for both the first etching process and the second etching process. The mask pattern remains in place throughout both etching steps, eliminating the need for additional mask patterns and reducing manufacturing complexity while achieving the required trench depth for high breakdown voltage and electrical isolation.
Solution Approach 2:
The first etching process creates an initial trench structure that serves as a foundation for the second etching process. By pre-forming this initial structure with the first etching step, the second etching process can efficiently extend the trench to the final required depth without requiring additional mask alignment steps, thereby reducing overall process complexity.
3Ease of manufacture
If the air gap upper end is positioned at a high position in the substrate, then the DTI region can be formed more easily, but cracking occurs in subsequent processes reducing device reliability
Solution Approach 1:
The first etching process preliminarily forms the trench structure with the mask pattern in place, creating a controlled initial geometry. This preliminary action ensures that when the second etching process extends the trench deeper, the air gap upper end is positioned at an appropriate depth that prevents cracking in subsequent processes, while still allowing straightforward DTI formation.
Solution Approach 2:
The etching depth parameters are optimized across the two etching steps: the first etching process creates a trench to a specific first depth, and the second etching process extends it to a greater second depth. By carefully controlling these depth parameters, the air gap upper end position is optimized to prevent cracking while maintaining ease of DTI region formation.
4Reliability
If the trench width is reduced to achieve deep isolation, then electrical isolation is improved, but foreign substances may remain on the upper side of the DTI region
Solution Approach 1:
The trench formation is segmented into two depth stages, allowing the upper portion of the trench to maintain a wider opening while the lower portion achieves the necessary depth for isolation. This segmentation prevents foreign substance retention at the upper DTI region while still achieving sufficient electrical isolation at depth, as the wider upper section facilitates complete material removal and filling.
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
This configuration prevents cracking, reduces manufacturing costs, and ensures reliable electrical isolation by positioning the air gap deep within the substrate, minimizing the risk of foreign substance retention and maintaining a wide trench width, thereby enhancing breakdown voltage characteristics.
Implementation Method 1
a first trench is formed by etching the substrate to a first depth; a second trench is formed by etching from a bottom of the first trench to a second depth greater than the first depth
Data Source
AI summary
Proposed is a high voltage semiconductor device and a method of manufacturing the same and, more particularly, a high voltage semiconductor device and a method of manufacturing the same, which allow the upper end of an air gap or void formed in a DTI region to be positioned relatively deep in a substrate by forming a wide region with a relatively wide lateral width on the upper part of the DTI region, thereby preventing external exposure of the air gap in a subsequent process and preventing foreign substances such as tungsten from remaining on the upper side of the DTI region accordingly.