Photoinduced Effects in Thin Amorphous Chalcogenide Films

Abstract

Chalcogenide glasses are of practical interest for optics, optoelectronics and microelectronics due to their high infrared transmittance, chemical and physical durability, spectral sensitivity and high resolution. The practical utilization of As-S films as inorganic photoresist is based on the presence of a difference in the dissolution rates of the exposed and unexposed areas of the films and on the secure protection they give during etching of chromium coatings used in the metal photomasks fabrication. This paper offers results from the study of changes in transmittance and refractive index in the visible region of the spectrum and, dissolution rate in alkaline solutions and anisotropy of chalcogenide thin films after light illumination. Bulks from the systems As-S-I, As-S-Bi( Tl, Ge) have been synthesized. The results of the X-ray microanalysis performed showed that the composition of bulk samples as well as the evaporated layers are very closed to the expected compositions. From the transmittance measurements, the refractive indices have been calculated and the limits of their variations have been determined. The addition of surfactants lowered considerably the dissolution rates of the unexposed parts of the films. Most suitable for developing an inorganic photoresist are the films with composition As 42 S 58, since they feature the highest selective solubility, widest limits of processing, a selectivity, close to that of organic photoresist, and good reproducibility.