Method of controlling exposure
US5965308A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 29, 1996 |
| Grant date | Oct 12, 1999 |
| Priority date | — |
| Expiry date | Mar 29, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70558
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The exposure quantity with respect to a wafer is correctly measured under each illumination condition even when illumination conditions are changed over. Under each of conditions where the .sigma. value (coherence factor) of an illumination optical system is set to various values including its small, standard, and large values, a correlation data between the output (E) of a reference illuminance meter and the output (I) of an integrator sensor is obtained. With respect to the correlation data for the respective .sigma. values, approximate lines (24A, 24B, 24C, etc) are determined by the method of least squares and then gradients of these lines are stored as correlation coefficients (.alpha.). Under the illumination condition corresponding to each .sigma. value, the output (I) of the integrator sensor is divided by its corresponding correlation coefficient (.alpha.) so as to compute the exposure energy on the image surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.