A Wafer-Scale Ni-Salicide Contact Technology on n-Type 4H-SiC

Abstract

A self-aligned Nickel (Ni) silicide process (Salicide) for n-type ohmic contacts on 4H-SiC is demonstrated and electrically verified in a wafer-scale device process. The key point is to anneal the contacts in two steps. The process is successfully employed on wafer-level and a contact resistivity below 5 × 10 −6 · cm 2 is achieved. The influence of the proposed process on the oxide quality is investigated and no significant effect is observed. The proposed self-aligned technology eliminates the undesirable effects of the lift-off process. Moreover, it is simple, fast, and manufacturable at wafer-scale which saves time and cost.

Investigation of a Self-Aligned Cobalt Silicide Process for Ohmic Contacts to Silicon Carbide

“…This temperature is 200 C higher than that of the FSA of the self-aligned nickel silicide contacts to 4H-SiC for the same annealing conditions (RTP process) and time. 2 It is possible that the nucleation can be enhanced, and thus lower the temperature, by having a cleaner interface during the deposition. In situ clean by backsputtering and thermal desorption of moisture by in-situ heat treatment prior to deposition are two possible improvements.…”

“…Compared to the already established self-aligned nickel silicide process, the result is also unfavourable. Elahipanah et al 2 achieved q C of 5 Â 10 À6 X cm 2 by annealing at 950 C for 1 min as the SSA.…”

“…The finding that nickel silicide (Ni 2 Si) can be selfaligned to contact holes to silicon carbide (4H-SiC) 1,2 has opened up new research opportunities. An example of such a study was the finding that the self-aligned Ni 2 Si can be turned from rectifying to ohmic to p-type 4H-SiC by alloying it with aluminum at relatively low temperatures.…”

“…3 A comparison between self-aligned nickel silicide and lift-off process for power devices was recently presented by Sledziewski at the conference of silicon carbide and related materials (ECSCRM 2018). Nickel-based contact processes give good ohmic contacts to ntype 4H-SiC, 2,4,5 but often gives rectifying contacts to p-type, with some notable exceptions. [6][7][8] As such, there is currently missing a single-metal process for self-aligned ohmic contacts to p-type.…”

“…26,27 The annealing temperature range was limited in this study up to 1000 C. It was considered that any contact process requiring higher annealing temperatures than 1000 C would not be competitive with already established contact processes. 2,3,[21][22][23][28][29][30] Higher anneal temperatures could potentially degrade other device related properties, like the silicon dioxide (SiO 2 )/4H-SiC interface of metal oxide semiconductor field-effect transistors (MOSFETs).…”