Field Stop IGBT Injection Region for Low-Loss Latch-Up Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vertical insulated-gate bipolar transistor (IGBT) devices face challenges in reducing forward collector-emitter voltage drop and switching losses, particularly due to high carrier modulation in the N base of the PNP BJT, which degrades the safe operation area and increases the risk of latch-up during load short circuits, and the activation of dopant impurities at the back side of the wafer is problematic due to temperature constraints.
Innovation Solution
The solution involves forming and activating P-type hole injection regions on the top surface of the substrate before epitaxial drift region growth, eliminating the need for back side laser activation and allowing for tightly controlled dopant concentrations without high-temperature processes, thereby integrating a Fast Recovery Diode with the IGBT to enhance switching performance and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to form P-type hole injection region and N field stop region, then doping concentration can be controlled, but high-temperature activation process is required which may cause aluminum spiking
Solution Approach 1:
The P-type hole injection region is formed by ion implantation before epitaxial growth, and the dopant activation occurs during the subsequent epitaxial growth process at temperatures below 450°C, avoiding the need for separate high-temperature activation that would cause aluminum spiking
Solution Approach 2:
The epitaxial growth process serves as an intermediary mechanism that simultaneously activates the implanted dopants without requiring high temperatures, thus preventing aluminum spiking while achieving dopant activation
2Strength
If thick drift region is used to withstand high voltage, then breakdown voltage is improved, but forward voltage drop increases
Solution Approach 1:
The drift region is engineered with non-uniform doping characteristics through the interaction of the P-type hole injection region and N field stop region, creating localized variations in electric field distribution that reduce peak field strength and allow thinner drift layers for the same breakdown voltage
Solution Approach 2:
The doping concentration profile of the drift region is modified by the presence of the P-type hole injection region, changing the electric field distribution to achieve both high breakdown voltage and low forward voltage drop
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 approach reduces the forward voltage drop and switching losses, improves the safe operation area, and prevents latch-up, while avoiding the expense and inefficiency of laser annealing, allowing for more reliable and efficient IGBT operation.
Implementation Method 1
The doping concentrations of the P+ hole injector and the N field stop or N buffer regions of an IGBT may be used to control injection efficiency of the MOSFET into the base of the vertical BJT of the IGBT
Implementation Method 2
Punch through type IGBT structures generally use a P+ substrate wafer with an N buffer region and an N− drift region epitaxially grown on the P+ substrate
Implementation Method 3
the back side of a wafer may be ground and ion implanted with phosphorous or hydrogen to form an N field stop region and with boron to form a P-type hole injection region
Data Source
AI summary
A field stop insulated gate bipolar transistor (IGBT) fabricated without back-side laser dopant activation or any process temperatures over 450° C. after fabrication of front-side IGBT structures provides activated injection regions with controlled dopant concentrations. Injection regions may be formed on or in a substrate by epitaxial growth or ion implants and diffusion before growth of N field stop and drift layers and front-side fabrication of IGBT active cells. Back-side material removal can expose the injection region(s) for electrical connection to back-side metal. Alternatively, after front-side fabrication of IGBT active cells, back-side material removal can expose the field stop layer (or injection regions) and sputtering using a silicon target with a well-controlled doping concentration can form hole or electron injection regions with well-controlled doping concentration.