The selective deposition of nickel on n-Si(100) wafer in aqueous solut
ion was investigated. It was confirmed by cross-sectional FE-TEM exami
nation that the deposition of nickel occurred from a solution of nicke
l ions prepared by excluding the hypophosphite reducing agent from the
conventional electroless nickel plating bath, and that this depositio
n reaction accompanied the formation of SiO2. This finding shows that
the electrons needed to reduce the nickel ions to the metal are suppli
ed directly from the Si wafer. By utilizing this galvanic displacement
reaction, nickel metal in the form of minute dots measuring 1 mu m in
diameter was selectively deposited using a silicon oxide layer as the
resist in combination with a two-step process, which consisted of the
first step of immersing a Si wafer into a solution containing nickel
ions but no reducing agent to form nuclei of nickel metal, and the sec
ond step of immersing the wafer with the nuclei into a conventional el
ectroless nickel plating bath to cause the growth of the nuclei to the
desired size.