Resistless microfabrication of Cu thin films on n-type GaAs by projection patterned excimer laser doping

Resistless microfabrication of Cu thin films on n-type GaAs by projection patterned laser doping using a KrF excimer laser and a SiH4 gas is described. Copper thin films with a linewidth as narrow as 2.35μm are deposited selectively on the doped region by electroplating in a CuSO4 aqueous solution. The resistivity of the deposited Cu films is evaluated to be 2.45 x 10-6 Ω cm, which is compared to that of bulk Cu. Using this technique, nonalloyed ohmic contacts can be formed with a specific contact resistance of 2.32 x 10-5Ω cm2, which is one-thirtieth of that of the conventional alloyed contacts. The mechanism of Cu film deposition by electroplating is discussed