Low Temperature Ni-Al Ohmic Contacts to p-Type 4H-SiC Using Semi-Salicide Processing

Mattias Ekström,Arash Salemi,Carl-Mikael Zetterling,Shuo Ben Hou,Mikael Östling,Hossein Elahipanah

doi:10.4028/www.scientific.net/msf.924.389

Mattias Ekström, Arash Salemi + Show 4 more

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https://doi.org/10.4028/www.scientific.net/msf.924.389

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Journal: Materials Science Forum	Publication Date: Jun 5, 2018
Citations: 9	License type: CC BY 4.0

Affiliation: KTH Royal Institute of Technology

Abstract

Most semiconductor devices require low-resistance ohmic contact to p-type doped regions. In this work, we present a semi-salicide process that forms low-resistance contacts (~10-4 Ω cm2) to epitaxially grown p-type (>5×1018 cm-3) 4H-SiC at temperatures as low as 600 °C using rapid thermal processing (RTP). The first step is to self-align the nickel silicide (Ni2Si) at 600 °C. The second step is to deposit aluminium on top of the silicide, pattern it and then perform a second annealing step in the range 500 °C to 700 °C.

Highlights

Both bipolar junction transistors (BJTs) and P-channel metal-oxide-semiconductor field-effect transistors (PMOSs) benefit from low-resistance p-type ohmic contacts, as the contact resistance is a parasitic resistance for these devices
The wafer was further processed by SiO2 deposition, via opening (MERIE and 10 s spraying of diluted HF) and TiW/Al/TiW deposition/patterning
Unlike the conventional Ni-Al contact that requires anneals up to 1000 °C [2,3,4,5], the semi-salicide processed contacts only require that the second-step anneal is higher than 500 °C to become ohmic

Summary

Introduction

Both bipolar junction transistors (BJTs) and P-channel metal-oxide-semiconductor field-effect transistors (PMOSs) benefit from low-resistance p-type ohmic contacts, as the contact resistance is a parasitic resistance for these devices. Several different p-type contacts have been proposed and investigated, such as Ni-Al [2,3,4,5], NiTi-Al [2, 6,7,8], Ge-Ti-Al [9], Ti-Al [4, 10, 11], epitaxially grown MAX-phase Ti3SiC2 [12], phase segregation annealed co-sputtered Pt-Ti [13] and pure titanium [14]. We present a LO free/semi-salicide process for fabricating low-resistance Ni-Al contacts to p-type 4H-SiC. The process employs a first step of nickel salicide (Elahipanah et al [15]) and a second step of Al sputtering, patterning and RTP (400 °C to 700 °C).

Results

Conclusion