This work deals with the application of ozonated water for the BEOL stripping of DUV-resists. For this purpose analytical techniques for the quantification of molecular O3 in the water as well as methods for the non-destructive analysis of resists on wafers have been studied. The aim is to be able to determine the concentrations of O3, its decomposition, under the influence of various parameters, and to correlate these data with the polymer structure of the resist on the wafer and the efficiency of resist removal.

Chromium-free preferential etching techniques in combination with light optical microscopy were compared with the non-destructive Laser Scattering Tomography (LST) for the evaluation of crystal defect densities in Czochralski substrates grown under different conditions. Dichromate containing etching solutions (original Secco etch and dilute Secco etch) were included into the study as reference. The chromium-free etching solutions with high etch rates comprised mixtures of nitric, hydrofluoric and acetic acid with water (JEITA 1, MEMC). Those with low etch rates consisted of mixtures of nitric and acetic or propanoic acid with hydrogen peroxide which form peracetic or perpropanoic acid (Organic Peracid Etches). OPE solutions provide improved discrimination of different types of defects and work also on highly doped substrates. As a general result, it turned out that the defect densities determined by the preferential etching solutions applied were significantly higher than those evaluated by LST. Relatively close to the LST defect densities are those determined by original Secco etch for larger etch pits.