Total reflection X-Ray Fluorescence Spectroscopy (TXRF)
Total reflection x-ray fluorescence is a sensitive method for analysis of trace metals on the wafer surface. Transition metals such as Cr, Fe, Ni and others can be analyzed with a detection limit of 1E9 atoms/cm2. The spot size of the analysis is ~ 2 cm diameter and the penetration depth is about 400 A for a single crystal Si wafer. Analysis is non-destructive and a 50 point map can be generated across the wafer. Typically a W anode can provide satisfactory results for most applications – however an alternate anode such as Ag or Mo can also be used to access higher Z elements such as Br and As. TXRF is particularly useful for volatile elements as Ar, S, Cl and Br. These elements cannot be measured with other trace methods that require solution chemistry. On the other hand TXRF is not suitable for light elements such as Li, B, N, F, and Na. Sensitivity for Mg and Al is also poor.