Thermostable Ti/Au/Pt/Ti Schottky contacts to n-type 4H-SiC

Abstract

The electrical properties and interface chemistry of Ti/Au/Pt/Ti Schottky contacts to n-type 4H-SiC have been investigated with respect to their utilization for MESFETs operated at high temperatures. The electrical properties of these contacts were studied at room temperature as well as during thermal treatment. The barrier height determined from I -V characteristics was calculated to be 1.17 eV with an ideality factor of 1.09. These parameters were examined by ageing and temperature dependence tests as criteria for the thermal stability and reliability of the contacts. The barrier height and ideality factor did not change after prolonged heating at a constant temperature of 500 • C and operating temperatures up to 350 • C, which confirmed the contact stability. Diodes used in the measurements showed a low leakage current at 100 V reverse voltage and room temperature (2.48 × 10 −9 A) as well as at 350 • C (2.15 × 10 −5 A) and breakdown voltage above 400 V.The chemical interface properties were studied by x-ray photoelectron spectroscopy for as-deposited, annealed and heated contacts. Annealing at 575 • C for 10 min led to formation of TiC and Pt x Si in a restricted region close to the SiC interface. The data revealed a chemically stable Ti/SiC interface after annealing, which is of importance for stable rectifying characteristics during long-term operation.

Long-term reliability of Ti–Pt–Au metallization system for Schottky contact and first-level metallization on SiC MESFET

“…Regarding to the realization of Schottky contact on SiC for MESFET gates, SiC/Ti/Pt/Au has a stable behaviour in terms of electrical characteristics (ideality factor, barrier height) as reported by Kassamakova [2], but presents low MTF predictions for the resistivity evolution at high-channel temperatures. This increase might lead to a decrease of the maximum frequency of oscillation (f max ) and then degrade the frequency performances of high-power devices.…”

“…stabilization of the interface thanks to Ti reaction with C deriving from SiC dissociation forming TiC which acts as a barrier to further Ti diffusion in SiC (Fig. 6) (see also [2]). …”

“…Different metals (Au, Pt, Pd, Ni, Co, ...) were investigated for Schottky gate contacts on n-type SiC. Ti demonstrated good characteristics for Schottky contacts on SiC [1,2], whereas Au is classically used in integrated circuits because of its excellent conductivity, lack of oxidation, and its resistance to electromigration failures [3]. A possible compromise for taking advantage of the characteristics of these two metals is to utilize a two layer metallization Ti-Au.…”

Thermally Stable Schottky Barrier Diode by Ru/Diamond

“…5) For a Schottky contact on diamond, tungsten carbide (WC x ) has been studied; however degradation of both the n value and barrier height was observed following annealing at 500 C for 5 h. 6,7) Pt/diamond is a candidate for a high temperature durable Schottky contact, having high stability at 400 C for 117 h. 8) However, this system suffers from poor adhesion characteristics and can not be used in practical application. Silicon carbide has good stability, having been observed at 500 C for 100 h for a Tibased Schottky, 9) but when annealing at 500 C for more than 448 h, degradation of leakage has been observed. 10) Thus, herein a new Schottky metal for use in a Ru/diamond system is examined.…”