Vertical Bi-Directional JFET Layout for Compact Power Switching
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Solution Overview
Problem
Bi-directionality of power semiconductor switches is challenging due to active area consumption and requires design optimization in junction field effect transistors (JFETs) to improve electric device characteristics and reduce costs.
Innovation Solution
A bi-directional junction field effect transistor (JFET) with a semiconductor substrate featuring a first and second drift structure and a channel region arranged vertically between them, allowing for blocking voltages in both directions and optimizing device integration by stacking drift structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bi-directionality is implemented in power semiconductor switches, then voltage blocking capability in both directions is achieved, but active area consumption increases
Solution Approach 1:
The patent implements bi-directionality by stacking drift structures vertically along a third direction perpendicular to the channel region plane, transitioning from a two-dimensional lateral arrangement to a three-dimensional vertical arrangement. This allows voltage blocking in both directions without increasing the lateral active area footprint.
Solution Approach 2:
The control region is segmented into first and second sub-regions that selectively control current flow in opposite directions. The first sub-region controls current flow in a first direction while the second sub-region controls current flow in a second direction, enabling independent control of bi-directional current flow through divided control zones.
2Ease of manufacture
If device geometries are shrunk to reduce costs, then manufacturing cost decreases, but device functionality per unit area becomes more challenging
Solution Approach 1:
By stacking drift structures vertically in a third direction perpendicular to the substrate surface, the patent increases device functionality (voltage blocking capability) without increasing lateral dimensions. This vertical integration allows maintaining small footprint while achieving enhanced bi-directional power switching functionality.
Solution Approach 2:
The stacked drift structure configuration enables a single device to perform multiple functions: blocking voltages in both directions, conducting current in both directions, and providing selective control through divided control regions. This multi-functionality is achieved within a compact geometry suitable for cost-effective manufacturing.
3Reliability
If drift structures are stacked vertically between channel region and substrate surface, then area-specific on-state resistance is enhanced, but device complexity increases
Solution Approach 1:
The control region is divided into first and second sub-regions with different conductivity types, where each sub-region selectively controls current flow in one direction. This segmentation provides independent control of bi-directional current flow and enables optimized on-state resistance characteristics while maintaining manageable structural complexity through systematic zoning.
Data Source
Figure 1~2
Figure 3A~4B
Figure 4C~7
AI summary
A bi-directional junction field-effect transistor, bi-directional JFET (100) is proposed. The bi-directional JFET (100) includes a semiconductor substrate (102) having a first surface (1021) and a second surface (1022) opposite to the first surface (1021). The semiconductor substrate (102) includes a first drift structure (104) comprising a drift region (1041) of a first conductivity type. The semiconductor substrate (102) further includes a channel region (106) of the first conductivity type adjoining, along a first lateral direction (x1), to first and second sub-regions (1081, 1082) of a control region (108) of a second conductivity type. The semiconductor substrate (102) further includes a second drift structure (110) comprising a drift region (1101) of the first conductivity type. The channel region (106) and the first and second sub-regions (1081, 1082) of the control region (108) are arranged, along a vertical direction (y), between the first drift structure (104) and the second drift structure (110).