US 12,456,693 B2
Method for dual wavelength overlay measurement with focus at a photoresist top surface and apparatus for using same
Katsuya Kato, Yokkaichi (JP)
Assigned to Sandisk Technologies, Inc., Milpitas, CA (US)
Filed by SANDISK TECHNOLOGIES LLC, Addison, TX (US)
Filed on Sep. 7, 2022, as Appl. No. 17/930,156.
Prior Publication US 2024/0079341 A1, Mar. 7, 2024
Int. Cl. H01L 23/544 (2006.01); G03F 7/00 (2006.01)
CPC H01L 23/544 (2013.01) [G03F 7/0002 (2013.01); G03F 7/707 (2013.01); G03F 7/70716 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method, comprising:
forming an alignment mark in a kerf region;
forming at least one material portion over the alignment mark;
patterning the at least one material portion to expose the alignment mark located in the kerf region;
forming a photoresist material layer over the patterned portions of the at least one material portion located in die regions and over the alignment mark located in the kerf region;
lithographically patterning the photoresist material layer into die-region photoresist material portions that are formed within die regions and kerf-region photoresist material portion that is formed within the kerf region; and
measuring an overlay between the kerf-region photoresist material portion and the alignment mark using radiation having a peak wavelength that is less than 380 nm and that is focused at a focal plane located a height that is vertically raised above a horizontal plane including a top surface of the alignment mark by a vertical distance that is in a range from 50% to 100% of a maximum thickness the kerf-region photoresist material portion.