A periodic acid aqueous solution has been shown to remove thermally unstable hydrocarbons from silicon surfaces resulting in residual hydrocarbon concentrations which are much lower than those after RCA cleaning. Bonded pairs of silicon wafers cleaned in the periodic acid solution prior to bonding generate no bubbles after annealing at any temperature. The powerful oxidizing reaction of periodic acid solution with hydrocarbons is believed to be responsible for the performance. Periodic acid solution is environmentally friendly, hazard-free, and compatible to mainstream semiconductor technology.