Reflective Absorption IR Fourier-Spectroscopy of Photoresistive Films on Silicon

A comparative analysis of the reflectance-absorption spectroscopy method’s application using the diffuse reflection factory prefix DRIFT of the ALPHA IR spectrophotometer and the method of attenuated total reflection for study of the optical characteristics of the FP9120, AZ nLOF 2020, 2070, 5510 and KMP E3502 photoresist films with a thickness of 0.99–6.0 μm formed on the plates of monocrystalline silicon by centrifugation has been carried out. In the reflective absorption IR spectra absorption bands are observed on the background of interference bands which makes it possible to determine the refractive index of a photoresist at a known geometric film thickness. It is shown that the reflective absorption spectroscopy method using the diffuse reflection factory prefix DRIFT has both a higher sensitivity compared with the attenuated total reflection method and is suitable for non-destructive interoperative control during semiconductor electronics devices’s manufacturing. The most intense in the reflective absorption spectra of AZ nLOF and KMP E3502 photoresistive films are bands of valence vibrations of the aromatic ring (≈ 1500 cm -1 ), pulsation vibrations of the aromatic ring carbon skeleton (double maximum ≈ 1595 and 1610 cm -1 ) and a band with a maximum of ≈ 1430 cm -1 due to vibrations of the benzene ring, connected to the CH bridge. It was established that differences in the reflective absorption spectra of negative photoresist of different manufacturers – MicroChemicals (AZ nLOF series 2000) and Kempur Microelectronics (KMP E3502) are associated with various technologies of phenol-formaldehyde resin production and the residual solvent presence in the films.