Patent ID: 6361927
Filing Date: 2002-03-26
Classification: G02B

Abstract:
A method of fabricating a grating pattern, comprising the steps of:coating a first SOG solution on a glass substrate by a spin coating method to form a first SOG thin film coated on the glass substrate; heat-treating said first SOG thin film coated on said glass substrate at a first temperature of between 80 and 170Â° C. to form a first silicon oxide layer on said glass substrate; coating a second SOG solution on the first silicon oxide layer by a spin coating method to form a second SOG thin film on the glass substrate; heat-treating said second SOG thin film at a second temperature to form a second silicon oxide layer, said second temperature being lower than said first temperature and above 80Â° C.; coating a third SOG solution on the second silicon oxide layer by a spin coating method to form a third SOG thin film on the glass substrate; heat-treating said third SOG thin film at a third temperature to form a third silicon oxide layer, said third temperature being lower than said second temperature and above 70Â° C., thus forming a glass substrate with three silicon oxide layers thereon which have different etch rates; coating a photoresist layer over said first, second and third silicon oxide layers and exposing said photoresist layer by a masking process; developing said exposed photoresist layer and wet-etching said first, second and third silicon oxide layers once; and removing said photoresist layer to provide a glass substrate having a three-level stepped grating pattern thereon.