CONTACT RESISTIVITY OF RE, PT AND TA FILMS ON N-TYPE BETA-SIC - PRELIMINARY-RESULTS

Contact resistivities of as-deposited and annealed Pt, Re and Ta films on n-type single-crystalline beta-SiC(001) are characterized using a circular contact pattern and the circular transmission-line model method. The beta-SiC substrates used in the experiment are n-type doped either non-intentionally to a carrier concentration of about 10(17) cm(-3), or by nitrogen implantation and annealing to a concentration of 5 x 10(19) cm(-3). The effect of a finite resistance along the circular contact rings on the measured potentials is corrected with a resistance network model. On the non-intentionally doped beta-SiC substrates, Pt contacts are non-ohmic regardless of the heat treatment. The as-deposited Ta and Re contacts are ohmic with contact resistivities of 5 x 10(-5) Ohm cm(2) and 4 x 10(-4) Ohm cm(2) respectively. Upon annealing at 500 degrees C for 30 min, the resistivity of Ta increases slightly while that of Re decreases slightly. Both Ta and Re contacts become non-ohmic by annealing at 900 degrees C for 30 min. The as-deposited Ta, Pt and Re contacts are all ohmic on the nitrogen-implanted beta-SiC substrate. The contact resistivity of the as-deposited Ta contact is the lowest and in the order of high 10(-7) Ohm cm(2), stays about the same at 500 degrees C and degrades to 4.3 x 10(-6) Ohm cm(2) at 1000 degrees C. The as-deposited Re contact has the highest contact resistivity of 1 x 10(-4) Ohm cm(2) but it improves to 1 x 10(-5) Ohm cm(2) upon annealing at 900 degrees C. The contact resistivity of the as-deposited Pt contacts is 6 x 10(-6) Ohm cm(2) and increases to 1 x 10(-5) Ohm cm(2) at 500 degrees C. After annealing at 900 degrees C for 30 min, the Pt contact on the nitrogen-implanted beta-SiC is no longer ohmic. The results are compared with the reactions that take place in those systems.