Thermo-mechanically induced texture evolution and micro-structural change of aluminum metallization

Mads Brincker, Thomas Walter, Peter Kjær Kristensen, Vladimir Popok

Research output: Contribution to journalJournal articleResearchpeer-review

6 Citations (Scopus)

Abstract

During operation of high power electronic chips the topside metallization is subjected to cyclic compressive and tensile stresses leading to unwanted thermo-mechanical fatigue of the metallization layer. The stress is caused by the difference in the thermal expansion coefficients of the metallization and the semiconductor underneath that can lead to a severe structural degradation of the layer changing the electrical characteristics of the electronic chips, finally causing a failure. Although this problem is well-known, the underlying physical mechanisms governing this fatigue phenomenon are not yet fully understood. In this work, we investigate the microstructural evolution of an Al metallization on high power diode chips subjected to passive thermal cycling between 20 and 100ºC. The texture of the Al film is analyzed ex-situ by a combination of electron backscatter diffraction and X-ray diffraction. It is found that the initial dominating (111) orientation of Al grains in the film changes towards a (311) texture as the number of cycles increases. A simple model explaining the driving mechanism behind the crystallographic re-orientation is proposed. Also, large orientation gradients within individual grains are found to arise during thermal cycling, which results in sub-grain formation. These processes are the dominant mechanism for the degradation of the Al layer structure leading to the formation of voids and significant increase of the surface roughness.
Original languageEnglish
JournalJournal of Materials Science: Materials in Electronics
Volume29
Issue number5
Pages (from-to)3898-3904
Number of pages7
ISSN0957-4522
DOIs
Publication statusPublished - Mar 2018

Fingerprint

Metallizing
Aluminum
chips (electronics)
textures
Textures
aluminum
cycles
Thermal cycling
grain formation
degradation
Fatigue of materials
tensile stress
diffraction
Degradation
retraining
voids
thermal expansion
Microstructural evolution
surface roughness
Power electronics

Cite this

@article{33f566094b9a4eea982cccad6746d079,
title = "Thermo-mechanically induced texture evolution and micro-structural change of aluminum metallization",
abstract = "During operation of high power electronic chips the topside metallization is subjected to cyclic compressive and tensile stresses leading to unwanted thermo-mechanical fatigue of the metallization layer. The stress is caused by the difference in the thermal expansion coefficients of the metallization and the semiconductor underneath that can lead to a severe structural degradation of the layer changing the electrical characteristics of the electronic chips, finally causing a failure. Although this problem is well-known, the underlying physical mechanisms governing this fatigue phenomenon are not yet fully understood. In this work, we investigate the microstructural evolution of an Al metallization on high power diode chips subjected to passive thermal cycling between 20 and 100ºC. The texture of the Al film is analyzed ex-situ by a combination of electron backscatter diffraction and X-ray diffraction. It is found that the initial dominating (111) orientation of Al grains in the film changes towards a (311) texture as the number of cycles increases. A simple model explaining the driving mechanism behind the crystallographic re-orientation is proposed. Also, large orientation gradients within individual grains are found to arise during thermal cycling, which results in sub-grain formation. These processes are the dominant mechanism for the degradation of the Al layer structure leading to the formation of voids and significant increase of the surface roughness.",
author = "Mads Brincker and Thomas Walter and Kristensen, {Peter Kj{\ae}r} and Vladimir Popok",
year = "2018",
month = "3",
doi = "10.1007/s10854-017-8328-x",
language = "English",
volume = "29",
pages = "3898--3904",
journal = "Journal of Materials Science: Materials in Electronics",
issn = "0957-4522",
publisher = "Springer",
number = "5",

}

Thermo-mechanically induced texture evolution and micro-structural change of aluminum metallization. / Brincker, Mads; Walter, Thomas ; Kristensen, Peter Kjær; Popok, Vladimir.

In: Journal of Materials Science: Materials in Electronics, Vol. 29, No. 5, 03.2018, p. 3898-3904.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Thermo-mechanically induced texture evolution and micro-structural change of aluminum metallization

AU - Brincker, Mads

AU - Walter, Thomas

AU - Kristensen, Peter Kjær

AU - Popok, Vladimir

PY - 2018/3

Y1 - 2018/3

N2 - During operation of high power electronic chips the topside metallization is subjected to cyclic compressive and tensile stresses leading to unwanted thermo-mechanical fatigue of the metallization layer. The stress is caused by the difference in the thermal expansion coefficients of the metallization and the semiconductor underneath that can lead to a severe structural degradation of the layer changing the electrical characteristics of the electronic chips, finally causing a failure. Although this problem is well-known, the underlying physical mechanisms governing this fatigue phenomenon are not yet fully understood. In this work, we investigate the microstructural evolution of an Al metallization on high power diode chips subjected to passive thermal cycling between 20 and 100ºC. The texture of the Al film is analyzed ex-situ by a combination of electron backscatter diffraction and X-ray diffraction. It is found that the initial dominating (111) orientation of Al grains in the film changes towards a (311) texture as the number of cycles increases. A simple model explaining the driving mechanism behind the crystallographic re-orientation is proposed. Also, large orientation gradients within individual grains are found to arise during thermal cycling, which results in sub-grain formation. These processes are the dominant mechanism for the degradation of the Al layer structure leading to the formation of voids and significant increase of the surface roughness.

AB - During operation of high power electronic chips the topside metallization is subjected to cyclic compressive and tensile stresses leading to unwanted thermo-mechanical fatigue of the metallization layer. The stress is caused by the difference in the thermal expansion coefficients of the metallization and the semiconductor underneath that can lead to a severe structural degradation of the layer changing the electrical characteristics of the electronic chips, finally causing a failure. Although this problem is well-known, the underlying physical mechanisms governing this fatigue phenomenon are not yet fully understood. In this work, we investigate the microstructural evolution of an Al metallization on high power diode chips subjected to passive thermal cycling between 20 and 100ºC. The texture of the Al film is analyzed ex-situ by a combination of electron backscatter diffraction and X-ray diffraction. It is found that the initial dominating (111) orientation of Al grains in the film changes towards a (311) texture as the number of cycles increases. A simple model explaining the driving mechanism behind the crystallographic re-orientation is proposed. Also, large orientation gradients within individual grains are found to arise during thermal cycling, which results in sub-grain formation. These processes are the dominant mechanism for the degradation of the Al layer structure leading to the formation of voids and significant increase of the surface roughness.

U2 - 10.1007/s10854-017-8328-x

DO - 10.1007/s10854-017-8328-x

M3 - Journal article

VL - 29

SP - 3898

EP - 3904

JO - Journal of Materials Science: Materials in Electronics

JF - Journal of Materials Science: Materials in Electronics

SN - 0957-4522

IS - 5

ER -