Patent ID: 6974549

Claim:
A method for forming fine grooves, comprising: forming a first silicon-nitride layer on a substrate; forming a first poly-silicon layer on said first silicon-nitride layer; forming a second silicon-nitride layer on said first poly-silicon layer; patterning said second silicon-nitride layer; etching said first poly-silicon layer using said patterned second silicon-nitride layer as a mask; forming at least one patterned oxidized portion of said first poly-silicon layer by oxidizing the substrate, first silicon-nitride layer, etched first poly-silicon layer, and patterned second silicon-nitride layer; removing the patterned second silicon-nitride layer and etched first poly-silicon layer such that the first silicon-nitride layer and at least one patterned oxidized portion of said first poly-silicon layer remain on the substrate; forming a second poly-silicon layer on said at least one oxidized portion of said first poly-silicon layer and first silicon-nitride layer; forming a third silicon-nitride layer on said second poly-silicon layer; forming a pattern of said third silicon-nitride layer at a position of the at least one oxidized pattern formed previously; etching said second poly-silicon layer using said third silicon-nitride layer as a mask; oxidizing an entirety of the substrate, first silicon-nitride layer, second poly-silicon layer and third silicon-nitride layer; selectively etching said third silicon-nitride layer and remaining second poly-silicon layer such that the first silicon-nitride layer and at least one patterned oxidized portion of said second poly-silicon layer remain on the substrate; and forming a plurality of fine grooves over the substrate by plasma etching said first silicon-nitride layer using the at least one patterned oxidized portion of said first and second poly-silicon layer as a mask.