Suppressing lithography at a wafer edge
View Patent ↗Damage to the rim of a semiconductor wafer caused by etching processes is reduced by forming a rim of carbonized photoresist around the outer edge of the wafer, using a wafer edge tool to carbonize the outer rim of a positive tone photoresist.
1. A method of manufacturing a set of integrated circuits on a wafer comprising the steps of:
preparing an integrated circuit substrate;
depositing a layer of photosensitive material having a blocking thickness over said wafer;
irradiating said photosensitive material in a blocking area at the outer edge of said wafer with a radiation dose such that said photosensitive material in said blocking area is desensitized;
developing said photosensitive material to leave a layer of blocking material in said area;
exposing a layer of patterning photoresist inside said blocking area with a set of images of a component pattern of a component of said set of integrated circuits;
etching said wafer through said component pattern, while said blocking material blocks etching in said blocking area; and
continuing with processing said set of integrated circuits.
2. A method according to claim 1 , in which said photosensitive material is carbonized by said radiation dose.
3. A method according to claim 2 , in which said photosensitive material is disposed over a layer of etch-resistant material.
4. A method according to claim 2 , in which said photosensitive material is positive tone photoresist.
5. A method according to claim 2 , in which said radiation dose is delivered by deflecting said radiation along two orthogonal axes, so that said blocking area has an inner boundary comprising a set of edges at right angles.
6. A method according to claim 1 , in which said photosensitive material and said patterning photoresist are the same, so that said photosensitive material receives said set of images.
7. A method according to claim 6 , in which said photosensitive material is disposed over a layer of etch-resistant material.
8. A method according to claim 6 , in which said photosensitive material is positive tone photoresist.
9. A method according to claim 1 , in which said images of said component pattern are images of deep trench apertures in DRAM cells.
10. A method according to claim 1 , in which said photosensitive material is disposed over a layer of etch-resistant material.
11. A method according to claim 1 , in which said photosensitive material is positive tone photoresist.
12. A method according to claim 1 , in which said radiation dose is delivered by rotating said wafer about its center, so that said blocking area has an inner boundary comprising a circle.
13. A method according to claim 1 , in which said radiation dose is delivered by deflecting said radiation along two orthogonal axes, so that said blocking area has an inner boundary comprising a set of edges at right angles.