Semiconductor Electrode Layout With Work-Function Split for Smaller Chips
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Solution Overview
Problem
The increase in chip size due to ineffective regions in semiconductor devices with IGBT and diode regions, where metal in ohmic contact with the n-type cathode layer also contacts the p-type collector layer, leading to unnecessary space occupation.
Innovation Solution
The implementation of electrodes with different work functions, where the first electrode has a larger work function than the second electrode, connected to the collector and cathode layers respectively, reducing contact resistance and eliminating ineffective regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single semiconductor substrate is used to integrate both IGBT and diode regions, then device integration is achieved, but ineffective regions increase chip size
Solution Approach 1:
The semiconductor substrate is divided into distinct IGBT regions and diode regions with clearly defined boundaries. The collector layer is segmented such that it forms part of the IGBT structure in the IGBT region while being excluded from the diode region, where the anode layer directly contacts the semiconductor substrate. This segmentation eliminates ineffective regions and ensures that each region contributes functionally to the device operation.
2Reliability
If metal in ohmic contact with the n-type cathode layer is also in contact with the p-type collector layer, then contact resistance is reduced, but ineffective regions are created
Solution Approach 1:
Different electrode configurations are applied to different regions of the semiconductor substrate. In the IGBT region, the first electrode contacts both the collector layer and cathode layer to reduce contact resistance. In the diode region, the anode layer directly contacts the semiconductor substrate without involving the collector layer, eliminating ineffective regions. This local differentiation of electrode structures optimizes both electrical performance and space utilization.
3Reliability
If electrodes with different work functions are used, then contact resistance is reduced, but device complexity increases
Solution Approach 1:
The work function parameter of the electrodes is optimized to reduce contact resistance. The first electrode has a work function of 4.0 eV or higher (such as aluminum or aluminum alloy) to achieve low contact resistance with the collector layer, while the second electrode has a work function of 4.5 eV or higher (such as titanium or titanium alloy) for optimal contact with the cathode layer. This parameter optimization reduces contact resistance without significantly increasing device complexity.
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 reduces chip size by minimizing contact resistance and ineffective regions, thereby optimizing semiconductor device design.
Implementation Method 1
A work function of the first electrode is larger than a work function of the second electrode
Data Source
AI summary
A semiconductor device includes a first electrode and a second electrode. The first electrode is connected to a collector layer and a first portion on the collector layer side of a cathode layer. The second electrode is connected to a second portion of the cathode layer excluding the first portion. A work function of the first electrode is larger than a work function of the second electrode, and one of the first electrode and the second electrode and the semiconductor substrate sandwich another of the first electrode and the second electrode in a thickness direction of the semiconductor substrate.