Stress Suppression of Backside Metal in GaAs Devices
Keywords: Backside electrode, Viahole, Plating, Stress, Nickel, Palladium
In a Ni-P/Au electroless plating backside electrode, the stress of a thin Ni –P film induced by annealing has been investigated using Stress gage, AES depth profile, X-ray diffraction measurements. Over around 100ºC temperature annealing, Ni diffusion was observed and the stress increased. With Ni diffusion, the Ni-P layer changed to P rich composition and to crystal from amorphous. The stress was caused by the crystallized Ni- P layer and the Ni diffusion layer. The increase of the stress is effectively suppressed by inserting the Pd barrier metal under Ni-P. The Pd/Ni-P/Au backside electrode makes it possible to form highly uniform and highly thermally stable metallization through via-hole on GaAs substrate.