Reactive ion beam etching of multilayer diffraction gratings with SiO2 as the top layer

Multilayer dielectric: grating plays an important role in the laser inertial confinement fusion, which is fabricated by using holographic lithography and ion beam etching. In this paper details the reactive ion beam etching of multilayer dielectric grating with SiO2 as the top layer. The etching Of SiO2 was carried out by a radio frequency reactive ion beam etcher with CHF3 chemistry to increase the etch selectivity and get a high fidelity grating pattern transfer from photoresist into SiO2 coating. The photoresist gratings with different profiles as masks were used to create SiO2 corrugations with different profiles separately. The etching results were analyzed in detail, including the facet and recleposition effects. In conclusion, it is essential that the photoresist grating mask should be high and steep enough to get SiO2 grating with vertical profiles. The multilayer dielectric grating with SiO2 as the top layer exhibited an efficiency of about 95% in the I order at TE polarization of 1064 nm light at Littrow mounting.