Semiconductor Device with Back Gate Electrode for Bidirectional Control
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Solution Overview
Problem
Existing semiconductor devices with two power MOSFETs for bidirectional current control are difficult to miniaturize, leading to challenges in size reduction for devices like cellular phones, and previous solutions either suffer from breakdown issues or struggle with bidirectional current control.
Innovation Solution
A semiconductor device design featuring a single transistor with a trench structure, including a first conductivity type semiconductor substrate, a drift area, a second conductivity type body area, a trench penetrating the source and body areas, an insulation film, a gate electrode, and a second conductivity type back gate electrode, allowing bidirectional control with reduced ON resistance and improved breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two power MOSFETs are used for bidirectional current control, then bidirectional current control is achieved, but device size increases
Solution Approach 1:
The patent merges two separate power MOSFETs into a single integrated device structure. The first and second power MOSFETs share a common drift area, body area, and substrate, with their source areas positioned on opposite sides. This integration allows bidirectional current control while reducing the overall device footprint compared to using two discrete MOSFETs.
Solution Approach 2:
The single semiconductor device structure serves multiple functions: it provides bidirectional current control, houses two independent gate electrodes for controlling current in opposite directions, and includes a common back gate electrode for overall device control. The shared drift and body areas are utilized by both MOSFET paths, making the structure multi-functional and space-efficient.
2Area of stationary object
If source area and back gate electrode are placed close together, then device size is reduced, but breakdown phenomenon occurs
Solution Approach 1:
The patent applies different quality requirements to different regions: the clearance between the source area and back gate electrode is specifically designed to be sufficient (e.g., 5-20 μm) in the high-stress region to prevent breakdown, while other areas of the device are optimized for size reduction. This localized quality adjustment ensures reliability where needed without compromising overall device miniaturization.
3Ease of manufacture
If ion implantation is used to form back gate electrode, then electrode is created, but manufacturing complexity increases
Solution Approach 1:
The back gate electrode structure is designed to be formed through self-aligned processes where the electrode naturally positions itself relative to the source and drain areas. The electrode extends from the substrate surface into the drift region, and its position is determined by the underlying structure rather than requiring complex alignment steps, thereby simplifying manufacturing.
Data Source
AI summary
A semiconductor device includes a second conductivity type back gate electrode formed within a body area, and electrically connected with the body area, and performs bidirectional current control in a direction from a drain area to a source area and in a direction from the source area to the drain area. A sheet resistance of the back gate electrode is lower than a sheet resistance of the body area. The source area and the back gate electrode are disposed apart from each other with a clearance sufficient for preventing a breakdown phenomenon caused between the source area and the back gate electrode when a maximum operation voltage is applied between the source area and the drain area.