Abstract
We report here on the simulation of temperature and stress evolution of 4H-SiC during laser-induced silicidation to locally generate ohmic contacts between the semiconductor and nickel metallization. The simulation is based on optical free carrier absorption, thermal conduction, and thermal radiation. Our results show that, during laser irradiation, similar temperatures and correspondingly similar contact resistances, as compared to conventional oven-driven annealing processes, are achievable, yet with the advantageous potential to limit the temperature treatment spatially to the desired regions for electrical contacts and without the necessity of heating complete wafers. However, due to temperature gradients during local laser silicidation, thermal induced stress appears, which may damage the SiC wafer. Based on the simulated results for temperature and stress increase, we identify an optimized regime for laser-induced local silicidation and compare it to experimental data and observations.
Highlights
Electronic devices based on silicon carbide (SiC) have distinctive advantages, especially for ultrafast and high-power electronics and high-temperature applications
To generate ohmic contacts on SiC, metals such as nickel, tungsten, or titanium are deposited on the wafer using physical vapor deposition (PVD) [3] followed by a so-called rapid thermal process (RTP) to transform the contact’s Schottky behavior into an ohmic one
Whereas the temperature increase can be attributed to the loading of the thermal capacities in the material, the saturation-type behavior can be attributed to a balance between ongoing energy input by the laser irradiation and the thermal conduction and thermal radiation
Summary
Electronic devices based on silicon carbide (SiC) have distinctive advantages, especially for ultrafast and high-power electronics and high-temperature applications. 4H-SiC by continuous wave (cw) infrared fiber laser irradiation, resulting in ohmic contacts with a resistance of 1.4 × 10−5 Ω·cm and a high temperature stability up to 450 K. Complementary to thermal simulation, since semiconductors and ceramics are very brittle, thermal induced stress analysis during laser scribing was simulated by Modest et al [17], who based the mechanical part of the simulation on the theory of elastic body Against this background, in this contribution, we extend our previous experimental studies by simulating the laser-induced temperature increase of 4H-SiC and correlate this to the achievable contact resistance. We simulate the thermal induced stress that may damage the semiconductor wafer when the stress exceeds a critical value Based on these results, we identify an optimized process regime for laser silicidation
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