Super Junction Trench Aspect Ratio via Layered Segmentation
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Solution Overview
Problem
The existing trench fill process for forming super junction structures in semiconductor devices faces challenges in achieving high aspect ratios, leading to difficulties in increasing the depth of trenches while maintaining the width, which affects the withstand voltage and on-resistance of power transistors.
Innovation Solution
The semiconductor device employs a multi-trench fill process where the epitaxial layer is divided into multiple layers, and trenches are formed in each layer, allowing for a higher aspect ratio by planarly superposing and connecting them, thereby increasing the depth of the trench and enhancing the withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the depth of the trench is increased to increase the withstand voltage, then the aspect ratio of the trench becomes larger, but the manufacturing difficulty increases significantly
Solution Approach 1:
The patent divides the epitaxial layer into multiple layers and forms trenches in each layer separately. By planarly superposing and connecting these trenches, the overall trench depth is increased while each individual trench maintains a manageable aspect ratio, thus resolving the contradiction between increasing withstand voltage and maintaining manufacturability.
2Manufacturing precision
If the cell size is shrunk to reduce on-resistance, then the impurity concentration of the n-type column region must be increased, but the trench aspect ratio becomes larger
Solution Approach 1:
The patent segments the epitaxial layer formation into multiple steps, creating multiple thinner layers. Trenches are formed in each layer and then connected planarly to achieve the required overall depth. This segmentation allows for smaller cell sizes and higher impurity concentrations in the n-type regions while keeping individual trench aspect ratios within producible limits.
3Strength
If the depth of p-type and n-type column regions is increased to increase withstand voltage, then the epitaxial layer thickness must be increased, but the trench aspect ratio becomes larger
Solution Approach 1:
The patent divides the thick epitaxial layer into multiple thinner partial layers. Trenches are formed in each partial layer and filled with semiconductor material to create p-type column regions. By connecting these segmented trenches planarly, the patent achieves increased overall column region depth for higher withstand voltage while maintaining each individual trench aspect ratio within producible limits.
Solution Approach 2:
The patent transitions from forming a single deep trench in the vertical dimension to forming multiple shallower trenches across multiple layers that are then connected. This dimensional approach allows achieving the required depth without exceeding the aspect ratio constraints of individual trench formation steps.
Data Source
AI summary
A super junction structure having a high aspect ratio is formed. An epitaxial layer is dividedly formed in layers using the trench fill process, and when each of the layers has been formed, trenches are formed in that layer. For example, when a first epitaxial layer has been formed, first trenches are formed in the epitaxial layer. Subsequently, when a second epitaxial layer has been formed, second trenches are formed in the epitaxial layer. Subsequently, when a third epitaxial layer has been formed, third trenches are formed in the third epitaxial layer.