SECONDARY-ION MASS-SPECTROMETRY STUDY OF SILICON SURFACE PREPARATION AND THE POLYSTYRENE SILICON INTERFACE/

Secondary ion mass spectrometry (SIMS) is now routinely employed to ob tain depth profiles in polymer films on silicon substrates, where diff usion, segregation, and ordering of deuterated polymer blend component s are typically examined with a depth resolution of less than 100 Angs trom. In some cases, diffusion or segregation behavior near the silico n surface is influenced by the extent of surface oxidation. There is a lso the potential for remnant moisture at the polymer/silicon interfac e to influence the redistribution of blend components. The effect of s tandard wet chemical wafer cleaning procedures on the polystyrene/sili con interface is investigated here. Deuterated solutions are employed to allow detection of remnant moisture from the cleaning/etching steps , and to indicate the extent of hydrogen termination at the polystyren e/silicon interface. Implant standards and deuterated polystyrene blen ds are employed to quantify the detected interfacial contaminants. The SIMS data indicate that the surface is effectively terminated by appr oximately one monolayer of hydrogen after an HF etch step, and by a th in oxide layer after an HCl/peroxide etch, in accord with numerous stu dies. There is no evidence of remnant moisture. Interfacial deuterium and oxygen are stable under 190 degrees C anneals. The absence of CD- secondary ions at the interface indicates that the interfacial deuteri um does not become associated with adjacent polystyrene chains. Low le vels of fluorine are also monitored, and the integrated fluorine conce ntration at the polystyrene/silicon interface is less than 0.01 monola yers of coverage. (C) 1997 American Vacuum Society.