Lithography process on high topology features

A method comprising:

• forming a target feature protruding above a base structure;
• forming a first photo resist layer over both the base structure and the target feature, wherein the first photo resist layer comprises:
• a corner portion having a sidewall contacting a sidewall of the target feature, and a bottom surface contacting a top surface of the base structure;
• and
• additional portions over and contacting the target feature and the base structure;
• performing a first exposure on the first photo resist layer, wherein the corner portion of the first photo resist layer is partially cross-linked after the first exposure;
• developing the first photo resist layer, wherein after the step of developing, the corner portion of the first photo resist layer remains, and the additional portions of the first photo resist layer are removed;
• forming a second photo resist layer over the corner portion of the first photo resist layer, the target feature, and the base structure;
• performing a second exposure on the second photo resist layer using a patterned lithography mask;
• and
• developing the second photo resist layer to form a patterned photo resist.

A method comprising:

• forming a first positive tone photo resist layer over a base structure and a target feature, with the target feature protruding over the base structure, wherein the first positive tone photo resist layer comprises a first portion over and contacting the base structure, a second portion over and contacting the target feature, and a corner portion at a corner formed between a top surface of the base structure and an edge of the target feature;
• performing a first exposure on the first positive tone photo resist layer, wherein the first exposure is an over exposure, and the first exposure results in partial cross-linking to be generated in the corner portion, and no cross-linking generated in additional portions of the first positive tone photo resist that are directly over the base structure and the target feature;
• developing the first positive tone photo resist layer, wherein after the step of developing, the corner portion of the first positive tone photo resist layer remains, and the additional portions of the first positive tone photo resist layer are removed;
• forming a second positive tone photo resist layer over the corner portion of the first positive tone photo resist layer, the target feature, and the base structure;
• performing a second exposure on the second positive tone photo resist layer using a patterned lithography mask;
• developing the second positive tone photo resist layer to form a patterned photo resist;
• and
• etching the target feature using the patterned photo resist as an etching mask.