System and method for characterizing lithography effects on a wafer
View Patent ↗In the manufacture of semiconductors, it is often necessary to characterize the effect of line width and line width shape on yield. In an example embodiment, there is a method ( 200 ) for randomizing exposure conditions across a substrate. The method comprises generating a list of random numbers ( 210 ). A random number is mapped ( 220 ) to an exposure field, forming a list of random numbers and corresponding exposure fields. The list or random numbers and corresponding exposure fields is sorted ( 230 ) by random number. To each exposure field in the list sorted by random number, an exposure dose is assigned ( 240 ). The list is sorted is sorted by exposure field ( 250 ).
1. A method for randomizing exposure conditions across a substrate comprising:
generating a list of random numbers;
mapping a random number to an exposure field, forming a list of random numbers and corresponding exposure fields;
sorting the list of random numbers and exposure fields by random number;
assigning an exposure dose to each exposure field in the list sorted by random number; and
sorting the list by exposure field.
2. The method of claim 1 farther comprising: printing the exposure field at the assigned exposure dose.
3. A method for characterizing lithography effects on a wafer, the method comprising:
determining an effect to study;
determining a number of exposure fields to print;
selecting at least one reference die location;
performing a randomization procedure;
printing the reference die at an exposure to make the reference die conspicuous; and
printing each exposure field at the assigned exposure dose.
4. The method of claim 3 , further comprising, performing electrical measurements on the wafer; and correlating the electrical measurements with line width.
5. The method of claim 3 , wherein the reference-die location is off-center.
6. The method of claim 3 wherein, selecting reference die locations is in four quadrants on the wafer.
7. The method of claim 3 wherein performing a randomization procedure comprises,
generating a list of random numbers;
mapping a random number to an exposure field,
forming a list of random numbers and corresponding exposure fields;
sorting the list of random numbers and exposure fields by random number;
assigning an exposure dose to each exposure field in the list sorted by random number; and
sorting the list by exposure field.
8. System for characterizing lithography effects on a wafer, comprising:
means for generating a list of random numbers;
means for mapping a random number to an exposure field, forming a list of random numbers and corresponding exposure fields;
means for sorting the list of random numbers and exposure fields by random number;
means for assigning an exposure dose to each exposure field in the list sorted by random number;
means for sorting the list by exposure field; and
means for printing the exposure field at an assigned dose.
9. The system of claim 8 farther comprising, means for selecting at least one reference die location; and means for printing the reference die at an exposure to make the reference die conspicuous.
10. A method of manufacturing an electronic device comprising a step of exposing a photosensitive layer with a predetermined dose, which predetermined dose is determined with a method according to claim 3 .
11. A method of manufacturing an electronic device comprising:
coating the wafer with a photo resist forming a photo-sensitive layer;
exposing the photo resist with a predetermined dose, the dose predetermined with a method comprising,
characterizing lithography effects on the photo-sensitive layer of the wafer, the characterization comprising:
determining an effect to study;
determining a number of exposure fields to print;
selecting at least one reference die location;
performing a randomization procedures;
printing the reference die on the photo-sensitive layer at an exposure to make the reference die conspicuous; and
printing each exposure field on the photo-sensitive layer at an assigned exposure dose.