Fabrication of Ohmic contact on semi-insulating 4H-SiC substrate by laser thermal annealing

Abstract

The Ni contact layer was deposited on semi-insulating 4H-SiC substrate by magnetron sputtering. The as-deposited samples were treated by rapid thermal annealing (RTA) and KrF excimer laser thermal annealing (LTA), respectively. The RTA annealed sample is rectifying while the LTA sample is Ohmic. The specific contact resistance (ρc) is 1.97 × 10−3 Ω·cm2, which was determined by the circular transmission line model. High resolution transmission electron microscopy morphologies and selected area electron diffraction patterns demonstrate that the 3C-SiC transition zone is formed in the near-interface region of the SiC after the as-deposited sample is treated by LTA, which is responsible for the Ohmic contact formation in the semi-insulating 4H-SiC.

Laser Annealing Simulations of Metallisations Deposited on 4H-SiC

“…This indicates that a large part of energy is reflected and the interface temperature might be too low to form an ohmic contact (T<600°C for Al(100nm)/4H-SiC). Nevertheless, refractory metals and nickel showed an interface temperature high enough to form ohmic contacts without using a top absorption layer, as already demonstrated in literature [4][5][6]. Finally, it is to note that the results clearly indicate that different thicknesses lead to different interface temperatures, as supposed, indicating that an optimisation can be realised, as a function of the metals stacking.…”

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

“…For an electrode material to form an Ohmic contact, it is closely related to the substrate material. A vast majority of the works reported were based on n-type 4H-SiC, as opposed to other substrates, such as 6H-SiC, semi-insulating 4H-SiC [13], and only Ni and Ti-based electrode materials have been reported [7,14,15]. Although different types of power device architectures can be fabricated to investigate the effect of laser annealing on the performance of ohmic contact, only simple device structures were used such as Schottky barrier diode and junction barrier Schottky diode [16,17].…”

“…It demonstrated that surface damage of SiC can be removed during the laser annealing process. Cheng [13] compared the contact resistivity of rapid thermal and laser-annealed Ni with 150 nm thick deposited on a silicon surface semi-insulating SiC substrate with the latter annealed strategy revealed a lower resistivity (1.97 × 10 −3 Ω•cm 2 ). Based on TEM (Figure 5b), it was found that in addition to Ni-Si phase and C clusters, 3C-SiC was also formed at the interface after laser treatment, but this was not detected in the rapid thermal annealed sample.…”

Resistor-to-Schottky barrier analytical model for ohmic contact test structures

“…Forming ohmic contacts requires high-temperature annealing, which activates the implanted dopants and forms silicide layers in traditional silicon ohmic contacts [8]. Recent advances in annealing, such as laser thermal annealing (LTA), have resulted in superior ohmic contacts for 4H-SiC-based devices [9] and up to 16% reduction in contact resistivity for Sub-10 nm FinFETs [10]. Improved models for ohmic contacts would be valuable in guiding future process refinements.…”