Metasurface structure and fabrication method thereof

A method for forming a metasurface structure, comprising:

• providing a substrate having a first region and a second region not overlapping with the first region;
• forming a plurality of first pillar elements within the first region on the substrate;
• and
• forming a plurality of second pillar elements within the second region on the substrate, wherein the plurality of first pillar elements has a first sectional profile and the plurality of second pillar elements has a second sectional profile that is different from the first sectional profile, and wherein at least one of the first sectional profile and the second sectional profile is of a non-rectangular shape.

A method of forming a metasurface structure comprising:

• providing a substrate having a first region and a second region not overlapping the first region;
• forming an amorphous silicon layer on the substrate in the first region and the second region;
• forming a hard mask layer on the amorphous silicon layer;
• coating a first photoresist layer on the hard mask layer;
• performing a photolithography process on the first photoresist layer in the first region with a first exposure condition, and performing a photolithography process on the first photoresist layer in the second region with a second exposure condition different from the first exposure condition, thereby forming photoresist patterns with different profiles in the first region and the second region;
• using the photoresist patterns with different profiles as an etching hard mask, subjecting the amorphous silicon layer to a first etching process, thereby forming pillar elements with different profiles;
• coating a second photoresist layer on the pillar elements in the first region;
• and
• using the second photoresist layer to perform a second etching process to the pillar elements in the second region, thereby forming a plurality of first pillar element in the first regions on the substrate and a plurality of second pillar elements in the second region on the substrate, wherein the plurality of first pillar elements comprises a first cross-sectional profile and the plurality of second pillar elements comprises a second cross-sectional profile different from the first cross-sectional profile, wherein at least one of the first cross-sectional profile and the second cross-sectional profile is non-rectangular.