Index Changes In Films Research Articles

Evaluating Photoresist Dissolution, Swelling, and Removal with an In Situ Film Refractive Index and Thickness Monitor

Dissolution and removal of photoresist films is performed numerous times during the fabrication of electronic, optical, and mechanical devices and integrated circuits. Information regarding changes in refractive index and film thickness is of interest for the design and modeling of such processes. Spectroscopic reflectometry is a cost-effective technique that has been used to monitor film thickness, but has been limited to applications in which the film refractive index is constant during dissolution, and thus has a known value. This paper extends conventional spectroscopic reflectometry analysis to account for refractive index changes in films during processing. Results obtained by this approach correlate well with spectroscopic ellipsometry measurements. This technique is applied to the dissolution of photoresist in aqueous base solutions, swelling of photoresist in solvent vapor, and removal of photoresist in water-alcohol mixtures, and can similarly be applied to other thin film applications. In addition, the optical properties of fluids such as aqueous and non-aqueous solvents, supercritical or subcritical mixtures, and gas-expanded liquids, which can be used to process thin film materials, can be monitored using spectroscopic reflectometry. © 2004 The Electrochemical Society. All rights reserved.

Holographic recording mechanisms of gratings in indium oxide films using 325 nm helium-cadmium laser irradiation

UV (325 nm) holographic recording of gratings in indium oxide films fabricated by reactive pulsed laser deposition has been investigated as a function of growth temperature, oxygen pressure and angle of incidence of the plasma plume on the substrate. The influence of the ambient environment (air or vacuum) and the film temperature during recording has also been studied. Large steady state refractive index changes up to 6×10-3 were observed in layers grown at an oblique angle of 75°. About 77% of the magnitude of these changes residues after thermal annealing and is attributed to UV-induced permanent structural rearrangements. In contrast, refractive index changes in films grown at normal incidence were smaller in magnitude and completely reversible.