Micromachining of CVD diamond film using a focused ion beam

Grooves of 2 - 3 mu m width were patterned on the surface of CVD diamond film by repeated straight scans of a focused gallium ion beam with an acceleration voltage of 25 kV, a beam current of 500 pA and a diameter of 2 mu m. Depth and width of the grooves depended on the volume resistivity of the diamond film. Depth was proportional to the irradiation time of the beam, i.e., the number of irradiated ions. Width increased with irradiation time, but gradually leveled off beyond the irradiation time of about 20 min. Under the same irradiation conditions, the lower the volume resistivity of the film was, the deeper and narrower the grooves were, i.e., the higher the aspect ratios of the grooves were. This was assumed to be due to the degree of electric charge on the surface. The film with high volume resistivity was charged; thus the ion beam could not be irradiated uniformly because ions were repelled electrostatically by the positive charges on the surface, and the obtained grooves were shallow and wide. The aspect ratios of the grooves became higher if the surface was uncharged. It was suggested that microparts could be cut out from a film less than 3 mu m thick by the focused ion beam irradiation.