Analysis of the Electrical Activation of P+ Implanted Layers as a Function of the Heating Rate of the Annealing Process

The surface morphology and the electrical activation of P+ implanted 4H-SiC were investigated with respect to annealing treatments that differ only for the heating rate. P+ implantation was carried out in lightly doped n-type epitaxial layers. The implantation temperature was 300 degrees C. The computed P profile was 250 nm thick with a concentration of 1x10(20) cm(-3). Two samples underwent annealing at 1400 degrees C in argon with different constant ramp up rates equal to 0.05 degrees C/s and 40 degrees C/s. A third sample underwent an incoherent light Rapid Thermal Annealing (RTA) at 1100 degrees C in argon before the annealing at 1400 degrees C with the lower ramp rate. The ramp up of the RTA process is a few hundred degrees per second. Atomic Force Microscopy (AFM) micrographs pointed out that the surface roughness of the samples annealed at 1400 degrees C increases with increasing heating rate and that the critical temperature for surface roughening is above 1100 degrees C. Independently on the annealing cycle, Scanning Capacitance Microscopy (SCM) measurements showed that the P profiles are uniform over the implantation thickness and have plateau concentration around 9x10(18) cm(-3) in all the implanted samples. The fraction of P atoms activated as donors is 13% of the total implanted fluence.