INFLUENCE OF THE WETTABILITY OF SILICON SUBSTRATES ON THE THICKNESS OF SOL-GEL SILICA FILMS

The fabrication of thick optical films by spinning from solution on si licon substrates is an important technique for integrated optics appli cations. In particular, several authors have studied the conditions un der which the thickness of set-gel silica films deposited on silicon w afers from solutions of water, tetraethoxysilane (TEOS) and ethanol ca n be maximized. The influence of processing parameters, such as compos ition, ageing period of the solution and spinning rate, have been stud ied. The effect of the wettability of the silicon substrate on the fil m thickness was investigated. The wetting characteristics of the silic on surface may be changed by adequate chemical cleaning methods. The h ydrophilic wafers obtained by controlled oxidation of the silicon were found to have greater affinity to the film forming solution and to le ad to thicker films than hydrophobic wafers obtained by etching the si licon surface with HF solution.