Session: 10-01 Interactive Presentations

Paper Number: 100267

100267 - A Thin-Film Sic Thermal Test Chip for Reliability Monitoring in Harsh Environment 

The thermal characteristic evaluation and reliability of wide-bandgap (WBG) devices leave crucial issues to be investigated for the next generation of power modules. For example, in automotive applications, the high performance of vehicle computer depends on the high thermo-mechanical reliability. Power cycling at elevated temperatures causes crack or delamination failure especially at the die-attached bonded interface in long term. Therefore, the in-situ reliability investigation of power modules, materials, and semi-conductor packages are of great significance in modern industries.

The excellent physical features of WBG materials such as silicon-carbide (SiC) and gallium-nitride (GaN) dominate the constraints of conventional silicon (Si) substrates. Thanks to the higher band-gap energy of SiC, these devices are capable of operating at considerably higher temperature, i.e., more than 400 ˚C. Moreover, its higher intrinsic thermal conductivity and higher mechanical strength make it a great candidate for next generation of semiconductor devices which are supposed to operate in harsh conditions.

In this work, a programmable thin-film SiC thermal test chip (TTC) is designed and fabricated to mimic the behaviour of WBG power modules. It allows thermal and power cycling tests to examine the thermal reliability by monitoring changes of the internal junction-to-case thermal resistance. The chip is modular in size, power mapping, and substrate thickness. The SiC wafer contains identical 4x4 mm² cells that could be diced into any desired array configuration, which provides modularity in size. Prior to dicing, the wafer could also be mechanically polished to achieve a substrate thinner than 300 µm which is the initial thickness in the proposed process.

Each TTC cell includes 6 electrically-isolated microheaters which allows for uniform, non-uniform, or hot-spot profiles. The proportional active heater area is larger than 82.5 percent which provides standard uniformity in temperature distribution. In addition, 3 high-precision resistive temperature detectors (RTDs) are added to enable tracking the junction temperature with high spatial resolution during thermal characterizations. The fabrication process of SiC TTC is based on the thin-film technology. 4H-SiC substrate with 300 µm initial thickness is chosen because of its intrinsic higher thermal conductivity and higher bandgap energy of 3.23 eV. The two metallization steps in this process were carried out using electron beam evaporation. The micro-heaters and RTDs were created using one layer of Platinum (Pt). Chromium-gold (Cr-Au) was subsequently deposited to form interconnects and bonding pads.

The SiC TTC with improved functionality at elevated temperatures could serve as a reliable platform for evolution of power-electronics packaging. The TTC can be employed in variety of reliability characterizations in harsh environment, including on/off cycling tests and thermal characterization of nanoparticle-based sintering materials with high thermal conductivity as novel die-attach (DA) materials.

Presenting Author: Romina Sattari Delft University of Technology