SiC Trench Gate Floating Layer Width via Asymmetric Bottom
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices made from silicon carbide face challenges in impurity diffusion, particularly in the direction perpendicular to the injection of impurity ions, leading to insufficient width of the floating layer in the short direction of the trench gate, which results in reduced withstand voltage.
Innovation Solution
A manufacturing method for semiconductor devices that involves forming a trench with a bottom portion deeper at the end than the center, injecting second conductivity type impurity ions into the bottom portion, and deepening the central portion of the trench to widen the floating layer in the short direction, ensuring sufficient width and improved withstand voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If impurity ions are injected into the bottom portion of a trench to form a floating layer in silicon carbide semiconductor substrate, then the floating layer is formed, but the impurity ions are hard to diffuse in the plane direction perpendicular to injection direction, resulting in insufficient width of the floating layer
Solution Approach 1:
The patent applies asymmetry by forming a trench with an asymmetric bottom profile where the central portion is deeper than the end portions. This asymmetric geometry causes impurity ions injected into the trench bottom to diffuse preferentially in the plane direction, widening the floating layer width while maintaining sufficient diffusion depth, thereby resolving the contradiction between floating layer width and withstand voltage
Solution Approach 2:
The patent introduces a dimensional change by creating a three-dimensional asymmetric trench bottom structure instead of a flat bottom. By making the central portion deeper, the impurity diffusion process is extended into the depth dimension, which indirectly promotes lateral diffusion in the plane direction, thus increasing the floating layer width without compromising the vertical junction depth needed for withstand voltage
2Manufacturing precision
If boron ions are injected in deeper position and aluminum ions in shallower position to widen floating layer, then the floating layer width is increased in deep position, but the width is narrowed in shallow position
Solution Approach 1:
The patent extracts and eliminates the need for multiple impurity injection steps with different ion types. Instead of injecting both boron ions at deep positions and aluminum ions at shallow positions, the invention uses a single impurity injection process into the asymmetric trench, simplifying the manufacturing process while achieving uniform floating layer width enhancement throughout the trench depth
Solution Approach 2:
The patent changes the geometric parameter of the trench bottom from a flat configuration to an asymmetric configuration with a deeper central portion. This parameter change in trench geometry fundamentally alters the impurity diffusion behavior, enabling single-step impurity injection to achieve the same effect that previously required multi-step injection with different ion types and positions
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 method effectively widens the floating layer in the short direction of the trench gate, enhancing the withstand voltage characteristics of the semiconductor device and providing a more adjustable and improved manufacturing process compared to conventional methods.
Implementation Method 1
injecting second conductivity type impurity ions into the bottom portion of the trench
Implementation Method 2
the impurity ions thus injected are hard to diffuse in a plane direction of the semiconductor substrate
Data Source
AI summary
A manufacturing method of a semiconductor device includes: a semiconductor substrate including a drain, a drift making contact with a front face of the drain, a body contacting with a front face of the drift, a source provided in part of a front face of the body, and a floating surrounded by the drift; and a gate including an insulator formed on an inner wall of a trench and a electrode disposed inside the insulator and which has a bottom portion contacting with the floating, the manufacturing method includes: forming the trench in a semiconductor wafer so as to have a bottom portion in which an end portion in a short direction perpendicular to a longitudinal direction thereof is deeper than a central portion; injecting an impurity ions into the bottom portion of the trench; and forming the central portion of the trench in the short direction to be deepened.