Globally planarized binary optical mask using buried absorbers

A method of fabricating a binary optical photolithography mask for use in projecting an image onto a target, comprising the steps of:

• forming a photoresistive layer over a mask substrate;
• patterning said photoresistive layer to expose portions of said substrate underlying said photoresistive layer;
• etching said exposed portions of said substrate to a predefined depth to form trenches in said substrate;
• removing remaining portions of said photoresistive layer;
• depositing a layer of light absorbing material over said substrate and filling said trenches;
• selectively etching back said layer of light absorbing material until only said trenches are filled with said light absorbing material;
• forming a dielectric layer of a predefined thickness over said substrate and said trenches to form an upper boundary region of said mask in order to bury said light absorbing material below a surface of said mask now formed by exposed surface of said dielectric layer;
• wherein said absorbing material forms an absorber pattern below said surface of said substrate but not adjacent to said surface, such that light scattered from surface areas of said absorber pattern are reflected back into said substrate at a surface interface of said substrate, in order to improve image feature definition at said target;
• and
• wherein having said absorber pattern buried below said surface at a depth d, determined by said predefined thickness of said dielectric layer, is of sufficient depth in order to provide for a maximum depth of focus of an exposure system being utilized to reside within said substrate, such that surface defects and contaminants at said surface interface are not imaged.

A method of fabricating a binary optical photolithography mask for use in projecting an image onto a target, comprising the steps of:

• forming an oxide layer over a mask substrate;
• forming a photoresistive layer over said oxide layer;
• patterning said photoresistive layer to expose portions of said oxide layer underlying said photoresistive layer;
• etching said exposed portions of said oxide layer to expose portions of said underlying substrate;
• removing remaining portions of said photoresistive layer, but leaving patterned portions of said oxide layer;
• implanting doped ions into exposed portions of said substrate to a set depth d below exposed surface of said substrate to form patterned light absorbing regions in said substrate but not adjacent to said surface;
• removing remaining portion of said oxide layer such that said substrate has a substantially planar surface with buried light absorbing regions below surface of said substrate;
• wherein said buried absorbing regions allow for light scattered from surface areas of said absorbing regions to be reflected back into said substrate at a surface interface of said substrate, in order to improve image feature definition at said target;
• and
• wherein having said patterned absorbing regions buried below said surface at said depth d is of sufficient depth in order to provide for a maximum depth of focus of an exposure system being utilized to reside within said substrate, such that surface defects and contaminants at said surface interface are not imaged.