Atomistic Simulations of the Silicon Surface Structure at the Interface of Silver Thick Film Contacts on n-Type Silicon

Abstract

Nanoscale silver crystals at the interface of silver thick film contacts on n-type silicon carry the current across the contact and therefore control the contact resistance, which is a main performance limiting parameter for semiconductor devices. The silver crystals are located in pits at the silicon surface. The shape of the pits is different on Si-(111) and Si-(100). During contact formation, these pits form before the silver crystals. Hence they determine the crystal size and shape. Consequently, the pits with the crystals influence the contact resistance. We investigate these pits experimentally by scanning electron microscopy. We are the first to simulate the mechanism of pit formation at a contact interface by considering a model that is based on the removal probability of silicon surface atoms. This model leads to good agreement between experimental and simulated data. It enables the prediction of pit formation for arbitrary process parameters like temperature and duration for silver thick film contact formation on silicon.