Bipolar Junction Field Effect Transistor Field-Oxide Termination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The voltage-bearing capacity of the termination area in conventional superjunction IGBTs is limited due to the constraints of the conventional fabrication process, leading to fluctuations in device performance and low yield in mass production.
Innovation Solution
A bipolar junction field effect transistor design with pillar regions of a second doping type vertically extended and laterally spaced in a drift region, accompanied by a field oxide layer above the drift region in the termination area, allowing the pillar regions to be directly connected to the field oxide layer, thereby increasing the height of the pillar and drift regions compared to conventional designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication process is used for superjunction IGBT, then the manufacturing process is simple and compatible with existing technology, but the voltage-bearing capacity of the termination area is limited and device performance fluctuates
Solution Approach 1:
The device is divided into cell area and termination area with different structures. The termination area uses a simplified structure without the complex second epitaxial layer and superjunction pillars, while the cell area maintains the full superjunction structure. This segmentation allows the termination area to achieve higher voltage-bearing capacity without requiring the complex fabrication process throughout the entire device.
Solution Approach 2:
Different regions of the device are given different structural qualities optimized for their specific functions. The cell area has the complete superjunction structure with high doping concentration pillars for low on-resistance, while the termination area has a simplified structure with lower doping concentration for high voltage bearing. This local differentiation resolves the contradiction by allowing each region to be optimized independently.
2Reliability
If the height of pillar and drift regions is increased to improve voltage-bearing capacity, then the breakdown voltage increases, but the fabrication process becomes more difficult and yield decreases
Solution Approach 1:
The device structure is segmented into cell area and termination area, where only the termination area requires increased drift region height for voltage bearing. The cell area maintains standard dimensions optimized for current conduction. This segmentation allows high breakdown voltage to be achieved without requiring the entire device to undergo complex high-precision fabrication processes.
Solution Approach 2:
Instead of increasing the height of pillar regions throughout the device (which would require complex fabrication), the invention inverts the approach by creating a termination area with extended drift region that directly contacts the field oxide layer, eliminating the need for high pillar structures in the termination area. This inverted structure achieves high voltage bearing with simpler fabrication.
3Reliability
If conventional superjunction structure is used in termination area, then the fabrication process is consistent, but the voltage-bearing capacity is limited due to the presence of second epitaxial layer
Solution Approach 1:
The second epitaxial layer and superjunction pillar structures are extracted (removed) from the termination area, leaving only the drift region and field oxide layer. This extraction eliminates the structural complexity and voltage bearing limitations imposed by the conventional superjunction structure in the termination area, while the cell area retains the full superjunction structure for low on-resistance operation.
Solution Approach 2:
The invention inverts the conventional approach by not using the superjunction structure in the termination area. Instead of forcing the termination area to follow the cell area's complex structure, the invention allows the termination area to have a simplified structure optimized for voltage bearing, with the drift region extending directly to contact the field oxide layer.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Disclosed are a bipolar junction field effect transistor and a manufacturing method therefor. The bipolar junction field effect transistor includes a drift region of a first doping type, formed in a cell area and a termination area of the bipolar junction field effect transistor; a plurality of pillar regions of a second doping type, extended in a vertical direction, spaced out in a lateral direction, and arranged in a drift region of a first doping type; a first doping type region and a well region of the second doping type formed inversely, successively arranged on the top of the pillar region in the cell area from near to far; and in the termination area, a field oxide layer provided above the drift region of the first doping type, wherein the pillar region in the termination area is in contact with the field oxide layer.