IGBT Collector Layer Dopant Segmentation for Breakdown Voltage
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Solution Overview
Problem
Conventional insulated-gate bipolar transistors (IGBTs) face a reduction in reverse breakdown voltage due to defects at the p-n junction, especially when a strong electric field is applied, leading to increased reverse leakage current.
Innovation Solution
A semiconductor device with a MOS gate structure on the front surface and a collector layer on the rear surface, where a first dopant and a second dopant are implanted, with the impurity concentration peak of the second dopant being deeper and larger than that of the first dopant, forming a thicker collector layer to prevent defects and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional collector layer is formed by single dopant implantation, then the manufacturing process is simple, but the reverse breakdown voltage is reduced due to defects at the p-n junction under strong electric field
Solution Approach 1:
The collector layer is segmented into multiple dopant regions: a first dopant (boron) forms a shallow junction near the surface, while a second dopant (aluminum) forms a deeper junction. This segmentation allows each dopant to serve distinct functional purposes, with the deeper aluminum junction providing robust reverse blocking capability that prevents breakdown voltage reduction
Solution Approach 2:
Different dopants are introduced at different depths and concentrations within the collector layer. The first dopant creates a high-concentration shallow region for carrier injection, while the second dopant creates a lower-concentration deeper region for electric field management. This local quality differentiation optimizes both forward conduction and reverse blocking characteristics
2Reliability
If the collector layer thickness is increased to prevent alloy spikes and scratches, then reverse leakage current is reduced, but the manufacturing complexity increases
Solution Approach 1:
Instead of simply increasing the collector layer thickness in one dimension, the patent introduces a new dimension of dopant type differentiation. By varying both depth and dopant species, the patent achieves effective defect prevention through the deeper second dopant junction without requiring excessive overall thickness, thus managing complexity more efficiently
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
The thicker collector layer effectively prevents alloy spikes and scratches from reaching the p-n junction, reducing reverse leakage current and improving reverse breakdown voltage, making the semiconductor device suitable for applications requiring high breakdown voltages.
Implementation Method 1
a collector layer of a second conductivity type into which a first dopant and a second dopant which is different from the first dopant are implanted
Data Source
AI summary
A semiconductor device is provided, the semiconductor device including a base layer of a first conductivity type having a MOS gate structure formed on a front surface side thereof, a collector layer of a second conductivity type formed on a rear surface side of the base layer, and into which a first dopant and a second dopant which is different from the first dopant are implanted, and a collector electrode formed on a rear surface side of the collector layer, wherein an impurity concentration peak of the second dopant is at a deeper position from the rear surface of the collector layer than an impurity concentration peak of the first dopant, and magnitude of the impurity concentration peak of the second dopant is larger than 1/100 of magnitude of the impurity concentration peak of the first dopant.