STUDIES ON A NEW CLEANING PROCEDURE FOR PFA SURFACES

An easy to perform procedure is presented for cleaning PFA (''Perfluor oalkoxy'') molds, especially for demanding and large scale application s. The leaching of PFA-vessels with diluted aqueous solutions of hydro gen peroxide, ammonia and triethanolamine (TEA) reveals cleaning effec ts comparable to the effectiveness of more hazardous procedures, such as leaching with concentrated nitric acid or with cleaning solutions c ontaining hydrofluoric acid. The method is suitable even for demanding applications in the field of semiconductor production. Differential t hermal desorption analysis (DTDA) gave no hints on chemical ''carry ov er'' effects of the organic ligand from pre-cleaned PFA molds to wafer surfaces. Furthermore, the results of TXRF-studies on Si-wafers have opened up promising prospects for the employment of TEA in wafer clean ing technology itself. The Fe deposition on Si-wafer surfaces from Fe- spiked SC-1-type cleaning solutions can evidently be suppressed for Fe concentrations up to 0.1 mg/l by the addition of TEA in 10(4)-fold ex cess.