SELECTIVE METAL-DEPOSITION ON SILICON SUBSTRATES

In order to delineate n/p junctions at (100) or cleaved Si faces, different plating processes (electroless in the dark or under illumination with photons of different energy) have been investigated. The effects of metal cation concentration, of illumination upon the formation of deposits onto n- or p-type silicon substrates, and p/n Si junctions have been studied. The role of an interfacial oxide layer has been emphasized. It is shown that platinum or palladium electroless deposition can be carried out on p-Si under ultraviolet illumination, in solutions free of HF. By contrast, in presence of a Si p/n junction, platinum, and palladium are only deposited on n-type areas. Models are proposed to explain the observed selective deposition.