Implantation mask formation

A method, comprising:

• forming a plurality of trenches through a photoresist layer over a substrate,
• performing a surface treatment operation using a perfluorinated compound on top surfaces of the photoresist layer and on sidewalls of the plurality of trenches,
• wherein the perfluorinated compound reacts with the photoresist layer to form a hardening layer on the top surfaces of the photoresist layer and on the sidewalls of the plurality of trenches, and
• wherein a carbon density of the hardening layer is greater relative to a carbon density of the photoresist layer;
• and
• performing, after performing the surface treatment operation, an ion implantation operation to form a plurality of isolation wells in the substrate using the photoresist layer and the plurality of trenches as an implantation mask.

A method, comprising:

• forming a plurality of trenches through a photoresist layer over a substrate,
• wherein an aspect ratio, between a height of the plurality of trenches and a width of the plurality of trenches, is equal to or less than approximately 8;
• increasing, after forming the plurality of trenches, the aspect ratio of the plurality of trenches to equal to or greater than approximately 10;
• performing, after increasing the aspect ratio and using the photoresist layer, an ion implantation operation to form a plurality of isolation wells in the substrate based on the plurality of trenches;
• forming an isolation structure in the substrate and over the plurality of isolation wells;
• forming, in between the plurality of isolation wells and in between the isolation structure, a plurality of photodiodes for a plurality of pixel sensors included in a pixel array;
• forming a plurality of color filter regions over the plurality of photodiodes;
• and
• forming a micro-lens layer over the plurality of color filter regions.