Electroless Nickel for N-Type Contact on 4H-SiC

Abstract

An electroless nickel film contains 5-14% by weight of phosphorus. Because of the presence of such a high concentration of phosphorus, electroless nickel can be a useful and convenient source of phosphorus dopant in the fabrication of n-type ohmic contacts for SiC. This paper describes the successful deposition of a Ni:P layer on 4H-SiC through electroless nickel plating followed by a discussion of the results of surface science and electrical measurements. Specific contact resistivity on lightly-doped samples with carrier concentration of 2.5 ´ 1016 cm-3 has been found to be about 4.8 ´ 10-6 Ωcm2 without any need for ion implantation. This metallization technique is especially useful in broad area ohmic contact formation on the back of n-type SiC substrate.

A new approach in impurity doping of 4H-SiC using silicidation

“…In the event that the nickel silicide layer need not be removed, as in the case of ohmic contact fabrication, the oxide layer is not necessary if some other means of providing phosphorus atoms is available, such as from a gas source or from electroless nickel plating. 13 The specific contact resistance data show that the values for type A samples are comparable to nitrogen-doped samples in the literature as shown in Table I but type B samples required higher contact annealing temperature to be comparable to nitrogen-doped samples. This is due to the need for higher temperature to activate the dopants.…”

“…In the TLM method, the total resistance between adjacent contacts (R T ) is measured as a function of separation, L, between the contacts. The specific contact resistance is then obtained from the slope and y-intercept of a linear plot of R T versus L. 13 Our TLM pattern consists of 200 lm  200 lm square pads with separation, L, varying from 8-48 lm. The TLM contact fabrication procedure began by first creating a mesa to isolate the TLM pattern and prevent fringing currents around the pattern in subsequent electrical measurements.…”