Process to form a mold of nanoimprint technique for making diffraction grating for DFB-LD

Abstract

A process using the nanoimprint technique to form the diffraction grating for the DFB-LD is disclosed. The process includes (a) coating a resist for the EB exposure on a dummy substrate, (b) irradiating the resist as varying the acceleration voltage, (c) forming a resist pattern by developing the irradiated resist, (d) coating the SOG film on the patterned resist, (e) attaching the silica substrate on the cured SOG film, and (f) removing the dummy substrate with the resist from the SOG film and the silica substrate. Using the mold thus formed, the diffraction grating for the DFB-LD is formed by the nanoimprint technique.

1 . A method to produce a mold for the nanoimprint technique, said mold being used for fabricating a diffraction grating for a distributed feedback laser diode, comprising steps of:
 (a) coating a dummy substrate with a photo resist for the electron beam lithograph;   (b) irradiating said photo resist by electron beams as varying an acceleration voltage of said electron beams;   (c) developing said irradiated resist to form a resist pattern;   (d) coating said resist pattern with a mold resin to be converted into said mold;   (e) curing said mold resin; and   (f) removing said dummy substrate and said resist pattern from said cured mold resin.   
     
     
         2 . The method according to  claim 1 ,
 wherein said resin to be converted into said mold is a spin on glass film.   
     
     
         3 . A method to produce a mold for the nanoimprint technique, said mold being used for fabricating a diffraction grating for a distributed feedback laser diode, comprising steps of:
 (a) coating a substrate with a first resist for the electron beam lithography;   (b) irradiating a first limited region of said first photo resist by electron beams;   (c) developing said irradiated first photoresist to prepare a first resist pattern;   (d) etching said substrate under a first condition with said patterned first photo resist as an etching mask to form a first pattern on said substrate and removing said patterned first photo resist after said etching;   (e) coating said substrate with a second photo resist for the electron beam lithography;   (f) irradiating a second limited region of said second photo resist by electron beams, said second limited region being different from said first limited region;   (g) developing said irradiated second photo resist to prepare a second resist pattern; and   (h) etching said substrate under a second condition different from said first condition with said patterned second photo resist as an etching mask to form a second pattern on said substrate and removing said patterned second photo resist after said etching,   wherein said first pattern and said second pattern constitute at least a potion of patterns provided in said mold.   
     
     
         4 . The method according to  claim 2 ,
 wherein said etching to form said first pattern has a different process time from said etching to form said second pattern.   
     
     
         5 . A method to produce a mold for the nanoimprint technique, said mold being used for fabricating a diffraction grating for a distributed feedback laser diode and having a pattern for said diffraction grating, comprising steps of:
 (a) coating a substrate with a photosensitive film;   (b) irradiating said photosensitive film by electron beams as varying an acceleration voltage of said electron beams; and   (c) developing said irradiated photosensitive film to form said pattern.   
     
     
         6 . The method according to  claim 5 ,
 wherein said photosensitive film is made of spin on glass material.