DEPOSITION OF COPPER FROM A BUFFERED OXIDE ETCHANT ONTO SILICON-WAFERS

The deposition of copper from a buffered oxide etchant (BOE) onto bare silicon, silicon dioxide, and patterned silicon wafers has been investigated. Deposition does not occur on surfaces of silicon dioxide, while deposition on regions of patterned silicon dioxide are observed at levels which fall between the deposition on bare silicon and silicon dioxide. The duration of a wafer rinse, which follows each immersion into a BOE solution, the silicon material as well as substrate doping do not affect the amount of deposition. The process of copper deposition from a BOE solution occurs uniformly across the surface of the wafer. The deposition on bare silicon surfaces shows an Arrhenius behavior, with two distinct activation energies: 0.40 eV (38.6 kJ mol(-1)) when the surface concentration is less than 6 x 10(14) Cu atom cm(-2) and 0.20 eV (19.3 kJ mol(-1)) when the surface concentration is greater than 6 x 10(14) Cu atom cm(-2). Surface roughness is observed to increase with the extent of deposition. An electrochemical reduction is used to describe the deposition of copper onto a silicon surface from a BOE solution.