Formation of high-conductivity NiSi2 layers on Si at zero-mismatch temperature by high-current Ni-ion implantation

According to a thermal expansion calculation, there would be no size mismatch between NiSi2 and Si lattices at 380 degrees C, which was defined as zero-mismatch temperature. The implantation was conducted with a metal vapor vacuum are (MEVVA) ion implanter at an extraction voltage of 45 kV. Based on a thermal conduction estimation, a temperature rise of 380 degrees C required the Ni-ion current density to be 35 mu A/cm(2). For the Si(111) wafers, the high conducting NiSi2 layers were indeed directly formed after Ni-ion implantation with this specific current density to a normal dose of 2 x 10(17) ions/cm(2) and the resistivity was as low as 9 mu Omega cm. For the Si(111) wafers pre-covered with a 10-nm Ni overlayer, the resistivity of the NiSi2 layers obtained under the same conditions decreased down to about 6 mu Omega cm. The superior electrical property of the NiSi2 was thought to be related to its formation temperature, i.e. at a zero-mismatch temperature of 380 degrees C, which resulted in minimizing the stress and stress-induced defects involved in its formation as well as cooling process.