Route towards power MOSFET large thin die mechanical robustness

Masters thesis report

Master thesis (2022)

Authors

N. Gupta Electrical Engineering, Mathematics and Computer Science

Contributors

René H. Poelma Electronic Components, Technology and Materials - EEMCS (supervisor 1)
Kouchi Zhang Electronic Components, Technology and Materials - EEMCS (supervisor 2)
P.J. French Bio-Electronics - EEMCS (supervisor 2)
W.D. van Driel Electronic Components, Technology and Materials - EEMCS (supervisor 2)
H.W. van Zeijl Electronic Components, Technology and Materials - EEMCS (supervisor 2)
Faculty
Electrical Engineering, Mathematics and Computer Science
Copyright: © 2022 Nikhil Gupta
Weibull distribution Ultra-thin die Three point bending Power MOSFET
More Info
expand_more

Published Date

20-10-2022

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Electrical Engineering, Mathematics and Computer Science

Abstract

Today’s cars are undergoing the greatest transformation the industry has seen. Power MOSFETs play a crucial role in making electronics more energy efficient by driving down switching losses and Rdson using a combination of next-generation trench technology and ultra-thin dies. Power MOSFET dies are becoming larger ( > 5 X 5 mm ) and thinner ( < 50 μm ) to meet the high performance lifetime requirements of the automotive industry. The high aspect ratio and the new chip designs with trench technology offer challenges for assembly, packaging and testing.

The majority of the research performed in the past, aimed to reduce the risk of die crack by improving equipment and process strategies in back-end semiconductor processing. This thesis study aims at improving die
strength from a front-end approach (device fabrication process) by making dies stronger to stress from die frontside. New chip designs are presented with new metal layer layouts for improved stress distribution. Materials like polyimide are investigated as new die top material for mechanical strengthening of die frontside. Key factors which influence die strength like trench-metal interaction, wafer stress and warpage are also analyzed in this thesis report.

In this study, ultra-thin power MOSFET dies are realised on 100 mm diameter silicon wafers with dimensions of 6 X 3 X 0.050 mm. These dies are mechanical equivalent in design, robustness to commercial trench power MOSFETs. The processed wafers are grinded from the backside to realise 50 μm thin wafers which are then sawned to obtain singulated dies. The strength of the dies are characterized by three-point bending tests and analyzed using probability plots for weibull distribution.