Y. Mizokami et al., CHEMICAL-ANALYSIS OF METALLIC CONTAMINATION ON A WAFER AFTER WET CLEANING, IEEE transactions on semiconductor manufacturing, 7(4), 1994, pp. 447-453
The chemical analysis of trace metallic contamination on a wafer can b
e achieved by using total reflection X-ray fluorescence (TRXRF) with H
F condensation and with poly silicon encapsulation secondary ion mass
spectroscopy (PC-SIMS). HF condensation can concentrate almost all ato
ms, such as Fe, Cr, and Ni, within 10 mm of the center of a wafer, whi
ch leads to lower detection limits. Poly silicon encapsulation elimina
tes the surface problems that tend to occur with normal SIMS, which re
sults in good reproducibility. A combination of both methods is suitab
le for analyzing lower-level contaminations up to 10(8) atoms/cm2 leve
l for many elements such as transient metals and lightly elemental met
als. The application of the analyses to wet cleaning reveals the conta
mination removal and adhesion effects for various solutions and cleani
ng procedures, as well as variation between experimental cleaning batc
hes.