Sense MOSFET Structure to Eliminate RC-IGBT Snapback
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Solution Overview
Problem
Conventional RC-IGBTs experience snapback due to conductivity modulation, making control difficult in low current regions, which affects detection sensitivity.
Innovation Solution
A semiconductor device with a MOSFET in the sense region and an IGBT in the main region, where the sense region lacks a p-type collector layer on its rear surface, preventing conductivity modulation and reducing on-voltage, thereby enhancing detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type collector layer is formed on the rear surface of the substrate in the sense region, then the structure provides conventional IGBT characteristics, but snapback occurs due to conductivity modulation making control difficult
Solution Approach 1:
The substrate is divided into a main region with IGBT structure and a sense region with MOSFET structure. The sense region specifically excludes the p-type collector layer on the rear surface, creating a segmented structure that prevents snapback in the sense region while maintaining IGBT functionality in the main region.
Solution Approach 2:
The p-type collector layer is selectively formed only in the main region and excluded from the sense region. This local differentiation in structure allows the sense region to operate without conductivity modulation effects, eliminating snapback and improving control stability for detection purposes.
2Measurement precision
If a p-type collector layer is formed on the rear surface in the sense region, then conventional structure is maintained, but on-voltage increases in low current region reducing detection sensitivity
Solution Approach 1:
The sense region is segmented from the main region by excluding the p-type collector layer formation. This segmentation allows the sense region to achieve lower on-voltage characteristics suitable for sensitive detection in low current regions, while the main region maintains conventional IGBT structure.
Solution Approach 2:
The sense region is given a different local structure by omitting the p-type collector layer, creating optimal electrical characteristics for detection. This local quality change reduces on-voltage in the sense region, thereby improving detection sensitivity without affecting the main IGBT region.
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 configuration increases responsiveness and detection sensitivity by eliminating snapback and maintaining low on-voltage in low current regions, improving control and sensitivity of the semiconductor device.
Implementation Method 1
the sense region has a lower on-voltage. Therefore, responsiveness at a turn-on time in the low current region is increased
Implementation Method 2
a back pn junction including a p-type collector layer and an n-type drift layer is turned on, whereby an on-voltage increases
Implementation Method 3
holes are injected from the p-type collector layer, resulting in conductivity modulation. Therefore, there occurs snapback in which the on-voltage rapidly decreases
Data Source
AI summary
A semiconductor substrate (1) includes a main region (2) and a sense region (3) having a smaller operation region area than that of the main region (2). An IGBT is formed in the main region (2). A MOSFET is formed as a sense device in the sense region (3) and has a gate electrode (15) connected to a gate electrode (15) of the IGBT. A front surface electrode (5) is formed on a front surface of the semiconductor substrate (1) in the main region (2). A rear surface electrode (20) is formed on a rear surface of the semiconductor substrate (1) in the main region (2) and the sense region (3). A current detection electrode (6) is formed on the front surface in the sense region (3) and separated from the front surface electrode (5).