Power Device Carrier Lifetime Zone
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Solution Overview
Problem
Power semiconductor devices, such as IGBTs, face challenges in reliability, switching speed, and miniaturization, particularly due to the induced electromotive force generated by inductors during power conversion, which can be mitigated by integrating a diode monolithically with the switch but requires precise control to prevent deterioration of the switch's forward performance.
Innovation Solution
A power semiconductor device is fabricated with a substrate having a drift layer and distinct regions for the switch and diode, where a metal structure with varying thicknesses and an implantation mask are used to prevent impurity implantation in the switch region, allowing helium ions to be implanted in the diode region to form a carrier lifetime zone, improving switching speed and turn-off characteristics without affecting the IGBT's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is integrated monolithically with the IGBT to counter induced electromotive force, then reliability is improved, but the forward performance of the IGBT may deteriorate due to impurity implantation
Solution Approach 1:
The substrate is divided into distinct first region (for IGBT) and second region (for diode), allowing separate optimization and independent impurity implantation processes for each device type, preventing cross-contamination and performance deterioration
Solution Approach 2:
A metal structure with varying thickness is introduced as an intermediary element that serves as a mask during impurity implantation, blocking impurities from reaching the IGBT region while allowing implantation in the diode region, thus protecting IGBT forward performance while enabling diode functionality
2Speed
If impurities are implanted in the diode region to improve switching speed, then the diode's turn-off characteristics are improved, but impurity implantation may affect the IGBT region
Solution Approach 1:
Different regions of the substrate are given different impurity concentrations and types - the diode region receives impurity implantation optimized for fast recovery characteristics, while the IGBT region maintains its original doping profile to preserve forward performance, achieving local optimization without compromising overall device functionality
Solution Approach 2:
The metal structure acts as a spatial mask that enables selective impurity implantation, allowing the diode region to be treated with impurities for improved switching speed while physically preventing impurity contamination of the IGBT region, thus resolving the conflict between speed improvement and performance integrity
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 solution enhances the switching speed and reliability of the diode while maintaining the integrity of the IGBT, suitable for high-frequency applications by precisely controlling the implantation of impurities, thereby addressing the limitations of existing power semiconductor devices.
Implementation Method 1
allowing helium ions to be implanted in the diode region to form a carrier lifetime zone
Implementation Method 2
an implantation mask are used to prevent impurity implantation in the switch region
Implementation Method 3
a zone provided in the drift layer in the second region of the substrate, the drift layer having impurities of a second type that is different from the first type
Data Source
AI summary
A power device includes a substrate including a drift layer and having a first region and a second region, the drift layer having impurities of a first type; a switch formed in the first region; a diode formed in the second region; a metal structure formed over a surface of the substrate, the metal structure having a first thickness over the first region of the substrate and a second thickness over the second region of the substrate, the first thickness and second thickness having at least 3 um in thickness difference; and a zone provided in the drift layer in the second region of the substrate, the zone having impurities of a second type that is different from the first type.