TY - THES

T1 - In-situ thermo-mechanical fatigue of copper metallizations

AU - Zernatto, Gerald Nikolaus

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Modern semiconductor devices are generally build up as various functional layers. Those layers are naturally composed from a multitude of materials with different electrical, mechanical, and thermal properties. The demand on high performance in combination with steadily advanced miniaturization leads to more and more extreme operating conditions with power devices being subjected to extreme heating rates in the order of 10^6 K/s. It is known that thermo-mechanical fatigue, especially of integrated metallizations, may occur when materials are subjected to such conditions repetitively.Actual microelectronic chips are rather difficult to subject to specific thermal loading conditions, consequently a special test chip – the poly-heater – was developed solely to emulate the thermal loadings as close to actual device operating conditions as possible. With a built-in heating element and a resistive temperature measuring structure it requires a special driving and monitoring setup in order to perform highly automated, well controlled repetitive stress testing. In the past, different in-situ experiments have been done utilizing optical microscopy and thermal imaging. This work takes the next step towards monitoring materials changes at a microstructural level by developing a setup for thermo-mechanical fatigue testing inside a scanning electron microscope. Various challenges had to be overcome in order to successfully perform fatigue experiments inside such a delicate scientific instrument. A custom-engineered setup has been build to deliver the power pulses into the vacuum chamber and drive the chip under well defined and safe conditions. Since fatigue experiments might last for several hours and images need to be captured in regular intervals, manual operation of the laboratory equipment during the test has been targeted to be minimized. A communication protocol from the scanning electron microscope offers some remote control capability and special software is developed to orchestrate all commercial and purpose-built devices utilized in the experiment. The software is capable of executing the in-situ stress test at a high level of automation. This way, time-consuming operations for the experimentalist are mainly reduced to test preparation. Finally, some efforts regarding image processing had to be made to gain the most information from the recorded data. This includes brightness and contrast adaption of the recorded images, spatial alignment, and noise reduction.

AB - Modern semiconductor devices are generally build up as various functional layers. Those layers are naturally composed from a multitude of materials with different electrical, mechanical, and thermal properties. The demand on high performance in combination with steadily advanced miniaturization leads to more and more extreme operating conditions with power devices being subjected to extreme heating rates in the order of 10^6 K/s. It is known that thermo-mechanical fatigue, especially of integrated metallizations, may occur when materials are subjected to such conditions repetitively.Actual microelectronic chips are rather difficult to subject to specific thermal loading conditions, consequently a special test chip – the poly-heater – was developed solely to emulate the thermal loadings as close to actual device operating conditions as possible. With a built-in heating element and a resistive temperature measuring structure it requires a special driving and monitoring setup in order to perform highly automated, well controlled repetitive stress testing. In the past, different in-situ experiments have been done utilizing optical microscopy and thermal imaging. This work takes the next step towards monitoring materials changes at a microstructural level by developing a setup for thermo-mechanical fatigue testing inside a scanning electron microscope. Various challenges had to be overcome in order to successfully perform fatigue experiments inside such a delicate scientific instrument. A custom-engineered setup has been build to deliver the power pulses into the vacuum chamber and drive the chip under well defined and safe conditions. Since fatigue experiments might last for several hours and images need to be captured in regular intervals, manual operation of the laboratory equipment during the test has been targeted to be minimized. A communication protocol from the scanning electron microscope offers some remote control capability and special software is developed to orchestrate all commercial and purpose-built devices utilized in the experiment. The software is capable of executing the in-situ stress test at a high level of automation. This way, time-consuming operations for the experimentalist are mainly reduced to test preparation. Finally, some efforts regarding image processing had to be made to gain the most information from the recorded data. This includes brightness and contrast adaption of the recorded images, spatial alignment, and noise reduction.

KW - Metallisierung

KW - Ermüdung

KW - Dünnschicht

KW - Kupfer

KW - thin film

KW - copper

KW - microelectronics

KW - fatigue

M3 - Master's Thesis

ER -