Structural and Electrical Characterization of Ni-Based Ohmic Contacts on 4H-SiC Formed by Solid-State Laser Annealing

Abstract

Laser annealing process for ohmic contact formation on 4H-SiC has attracted increasing attention in the last years, because it enables the fabrication of SiC power devices on very thin substrates. We have investigated the formation of Nickel-based ohmic contact on 4H-SiC by using a Yb:YAG laser in scanning mode, with a wavelength of 515 nm and a pulse duration of 1200 ns. A 100 nm thick Ni layer has been deposited on SiC and irradiated at different process conditions. The reaction process has been studied, as a function of fluence and scan number of laser annealing, by means of X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analyses. The electrical properties of the annealed layers have been evaluated on Schottky Barrier Diodes (SBDs) devices, confirming the ohmic behavior of the reacted contact and showing improved performances respect to RTA approach. The compatibility of thermal budget of the process in the front side has been verified by means process simulation. A strong relationship between structural properties of reacted layers and electrical behavior of SBDs devices has been revealed. Solid-state laser annealing process, with wavelength in green light region, can indeed represent a suitable solution for ohmic contact formation of 4H-SiC power devices, fabricated on thin substrates.

Fabrication of Ohmic Contact on N-Type SiC by Laser Annealed Process: A Review

“…The turn−on voltage (VF) of the device dropped from 1.78 V in the rapid annealing process to 1.62 V at a rated current of 6 A, and the leakage current of the device is less than 1 μA at a rated voltage of 650 V. It was also maintaining a blocking capability of more than 1.1 kV. In addition, Badala [31] prepared SBD with a similar struc- In addition, laser annealing on SiC power devices with thin substrates can reduce onresistance and switching loss. Rupp [30] deposited a NiSi layer on a thinned SiC substrate and formed an ohmic contact below 1 × 10 −5 Ω•cm 2 when treated with a 310 nm laser.…”

“…The turn-on voltage (V F ) of the device dropped from 1.78 V in the rapid annealing process to 1.62 V at a rated current of 6 A, and the leakage current of the device is less than 1 µA at a rated voltage of 650 V. It was also maintaining a blocking capability of more than 1.1 kV. In addition, Badala [31] prepared SBD with a similar structure and method, which proved the advantages in reducing the on-voltage. Rascuna [32] also applies a laser annealing process in the preparation of SiC power diodes.…”

Ni-Silicide Ohmic Contacts on 4H-SiC Formed by Multi Pulse Excimer Laser Annealing

“…A solution to form backside ohmic contacts after front side device definition is therefore required. Among the alternative processes to RTA proposed for Si [5][6][7][8], laser annealing is the most promising one for ohmic contact formation on 4H-SiC [9][10][11][12][13][14][15]. Excimer UV laser annealing has been widely studied for Ni-based ohmic contacts [16], with particular focus on single pulse process, with the aim to understand the early stages of reaction process [17][18].…”