Super Junction Trench Power MOSFET Gate Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional super junction trench power MOSFET devices face issues such as diffusion of p-type and n-type columns during fabrication, leading to reduced breakdown voltage, unsuitability for high-speed circuits due to floating p-type columns, and limited active device density due to trench gate placement.
Innovation Solution
Incorporating oxide layers to prevent diffusion between p-type and n-type columns, shorting p-type columns to the source for rapid carrier removal, and aligning trench gates over p-type columns to reduce n-type column width and increase cell density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional SJ trench power MOSFET devices are fabricated with heating processes, then the device can be manufactured, but the p-type columns and n-type columns diffuse into one another, reducing breakdown voltage
Solution Approach 1:
An oxide layer is introduced as an intermediary barrier between the p-type columns and n-type columns. This oxide layer prevents direct diffusion between the oppositely doped regions during heating processes, thereby maintaining breakdown voltage while allowing the device to be fabricated with standard heating processes.
Solution Approach 2:
The device structure is segmented by introducing oxide layers that physically separate the p-type columns from the n-type columns. This segmentation prevents unwanted interaction and diffusion between the two doped regions during fabrication and operation.
2Stability of the object's composition
If p-type columns are left floating in conventional SJ trench power MOSFET devices, then the super junction structure is maintained, but carriers cannot be removed rapidly, making the device unsuitable for high speed circuits
Solution Approach 1:
The p-type columns are transformed from a static floating state to a dynamic state where carriers can be rapidly removed. By connecting the p-type columns to the n+ source region, the structure enables active carrier extraction, allowing the device to switch rapidly while maintaining the super junction configuration.
3Device complexity
If trench gates are placed between p-type columns in conventional SJ trench power MOSFET devices, then the device structure is simplified, but the density of active devices is limited
Solution Approach 1:
The trench gate placement strategy is changed from being positioned between p-type columns to being positioned over n-type columns. This dimensional repositioning allows for reduced n-type column widths and increased spacing between trenches, thereby increasing the density of active devices that can be packed into a given area.
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
Enhances breakdown voltage stability, suitability for high-speed circuits, and reduces on-resistance (Rdson) by preventing column diffusion and optimizing trench gate placement.
Implementation Method 1
the oxide layers keep the adjacent n-type and p-type columns from diffusing into one another when the device is heated during fabrication
Data Source
AI summary
In a super junction trench power MOSFET (metal oxide semiconductor field effect transistor) device, a column of p-type dopant in the super junction is separated from a first column of n-type dopant by a first column of oxide and from a second column of n-type dopant by a second column of oxide. In an n-channel device, a gate element for the FET is advantageously situated over the column of p-type dopant; and in a p-channel device, a gate element for the FET is advantageously situated over the column of n-type dopant.