Method of adjusting lithography tool through scattered energy measurement
US5989764A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 9, 1999 |
| Grant date | Nov 23, 1999 |
| Priority date | — |
| Expiry date | Feb 9, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7026
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method to achieve good stepper focus and exposure over an entire wafer for a particular mask level before the start of a product run is described. This method can also be used to produce a characterization of lens field curvature (i.e., a surface of optimum focus across the lens) and to characterize lens astigmatism, defocus sensitivity, relative resolution, and other characteristics, and to check the stepper for optical column tilt. The process prevents the complexities of resist development from affecting determination of focus. The process involves forming an array of latent images in a resist and examining the scattered light from the edges of the latent images. Analysis of the scattered light quickly provides information on correct exposure and focus together with lens characteristics over the printing field.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.