Metal Contamination from Process Materials Used in Wet Cleaning of Silicon Wafer.

Contamination from process materials is an important consideration for the reduction of wafer contamination required for next generation of semiconductor devices. Traditionally, RCA based wafer cleaning process is employed for wet cleaning of silicon wafer. Commonly used chemicals are ammonium hydroxide (29 wt%), hydrogen peroxide (31 wt%), hydrochloric acid (37 wt%), hydrofluoric acid (49 wt%) blended with deionized water. Wetted materials widely used are 440 HP PFA Teflon, chemical resistance O-ring elastomers such as Kalrez, Teflon encapsulated viton, and regular or synthetic quartz. Elution of metal ions from interaction of these process materials with process chemicals can result into metal contamination of the wafer. In this paper, we have presented the level of metal elution from these process materials when exposed to the process chemicals used in wet cleaning of silicon wafer. Information obtained from the investigation can used to further reduce the metal contamination and to determine the suitability of these or other process materials, for wafer processing, based on contamination tolerance of the semiconductor device.