8/4/2019 Surface Preparation and Coating Strategies in Processing of Nickel Silicide Contacts on Silicon Carbide

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CONCLUSIONS

INTRODUCTION 

EXPERIMENTAL 

RESULTS

Two different procedures for coating of the SiC prior to contact

formation upon annealing were compared: single Ni layer 

deposited by sputtering and binary Ni-Si layer produced by co-

deposition of Ni and Si. In both cases, the dominant silicide formed

is the Ni2Si phase. In the former case, the silicide is formed in

crystalline form during the annealing, while in the case the silicide

is already formed during deposition (amorphous state). Thedevelopment of the contact behaviour is shown to be related to the

final characteristic of the Ni-silicide/SiC interface, which in turn is a

result of the preparation procedure and coating process. The

performance of the classical Ni/SiC contact formation and the

novel Ni+Si co-deposited contact formation was compared. The

latter results in less good electrical contact behaviour for same

annealing characteristics. Still, the co-deposition technique opens

new possibilities for tailoring of the contact properties after further 

optimisation.

Surface Preparation and Coating Strategies in

Processing

of Nickel Silicide Contacts on Silicon Carbide S. A. Pérez-Garcíaa,b, Y. Caob and L. Nyborgb

a)Centro de Investigación en Materiales Avanzados, S.C.; Alianza Norponiente #202, 66600 Apodaca, N.L.., México.

b)Department of Materials and Manufacturing Technology, Chalmers University of Technology, SE-41296, Göteborg,

Sweden.

Nickel coating is a preferred choice as precursor for contact

formation on SiC. This is because of the capability of Ni to provide

either Schottky or ohmic behaviour depending on the heattreatment and the silicide formed; ohmic behaviour has been

reported to appear for samples annealed above 900°C when

forming Ni2Si as the main silicide. The role of the silicide itself is not

fully clarified, even if it is clear that increasing annealing

temperature is a means of transforming a contact from Schottky to

ohmic, while actually preserving the same silicide . Thus, the

silicide itself cannot be a major cause for the contact behaviour.

. The aim of this study is to understand the effect of processing

procedures on the properties of nickel silicide onto single-crystal

SiC. In order to address this problem experimentally, cleaning of 

the SiC samples was done by means of the normal RCA method.

In a second series, argon ion etching was added as a pre-

treatment prior to Ni deposition. The development of the contactbehaviour is shown to be related to the final characteristic of the Ni-

silicide/SiC interface, which in turn is a result of the preparation

procedure and coating process. Comparison of the classical Ni/SiC

contact formation and a novel Ni+Si co-deposited contact formation

was achieved..

 ACKNOWLEDGMENTS 

The financial supports by CONACYT (Mexico) and STINT (Sweden) are

acknowledged. 

Two different procedures were employed using Kaufmann ion beam

sputtering as means of thin film deposition. Irrespective of 

procedure, the deposition rate was calibrated by controlling the

deposited thickness of thicker layers with stylus profilometry. In a

first series, Ni was sputter-deposited onto the SiC sample at room

temperature using Kaufmann ion beam sputtering. In order to form

the silicide before annealing a second series was accomplished by

applying co-deposition technique with two targets (Ni and Si). Nickeland Si were in this way simultaneously co-sputtered and deposited

on the SiC sample at room temperature. Thereafter, annealing was

performed in both series. In order to control the result of the

processing, X-ray photoelectron spectroscopy (XPS) was employed

after each step of the samples preparation.

Fig. 3 Current-voltage characteristic curves of the Ni/SiC contact

with a)RCA and b)RCA+ Ar ion etching pre-treatment for different

annealing temperatures

a)b)

Fig. 4 Current-voltage characteristic curves of the (Ni+Si)/SiC

contact with a)RCA and b)RCA+ Ar ion etching pre-treatment for 

different annealing temperatures

a) b)

Fig. 2 .1XRD diffractograms from thefirst series samples annealed at 950ºC;

a) RCA cleaning; b) RCA cleaning and

subsequent Ar ion etching in the UHV

chamber. 

Fig.-1 XPS depth profiles for 

the first series samples after 

annealing with different

pre-treatment prior to Ni

deposition: a) RCA cleaning;

b) RCA cleaning, subsequent

Ar ion etching in the UHV

chamber and c) second series

of samples after annealing

a) b)

c)

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Fig. 2 .2XPS Ni2p3/2 peak after heat

treatment of SiC sample co-sputtered

Ni and Si. Peaks corresponding to Ni2Si

through the contact layer recorded from

a) top surface, and b) after about 10 nm

of depth profiling.