Method of CMP integration for improved optical uniformity in advanced LCOS back-plane

A method of forming a filled contact hole on a mirror layer of a semiconductor substrate, the method comprising:

• forming a contact hole through a mirror layer of the semiconductor substrate by an etch process;
• filling the contact hole with a fill material, wherein a portion of the fill material extends over the mirror layer and the mirror layer is electrically isolated from a metal layer below the mirror laver;
• removing a portion of the fill material external to the contact hole by a removal process selective to the fill material;
• polishing an upper surface of the mirror layer to a surface roughness less than 10 nm;
• and
• forming an optical stack overlying the mirror layer and the fill material, wherein the optical stack comprises a distributed Bragg reflector (DBR) that forms an interface with the mirror layer and the fill material, and the DBR is characterized by a reflectance exceeding 95% across a wavelength range of 450 nm-650 nm.

A semiconductor structure comprising:

• a semiconductor substrate;
• a metal layer overlying the semiconductor substrate;
• a spacer layer overlying the metal layer;
• a mirror layer overlying the spacer layer;
• a fill material filling a contact hole formed in the mirror layer, the fill material substantially level with an upper surface of the mirror layer, the upper surface of the mirror layer characterized by an average roughness less than 5 nm;
• and
• an optical stack overlying the mirror layer and the fill material, wherein the optical stack comprises a distributed Bragg reflector (DBR) that forms an interface with the mirror layer and the fill material, and the DBR is characterized by a reflectance exceeding 95% across a wavelength range of 450 nm-650 nm.