Globally planarized binary optical mask using buried absorbers
US5474865A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 21, 1994 |
| Grant date | Dec 12, 1995 |
| Priority date | — |
| Expiry date | Nov 21, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F1/50
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A globally planarized binary optical mask has absorbers embedded (buried) in the mask substrate, instead of on the surface of the mask. Light scattering at rough vertical edges of absorbers of prior art masks are reduced or eliminated. Also, due to the buried nature of the absorbers, a triple singularity point encountered in prior art masks at the interface of three environments of quartz, absorber and air, no longer exists. The buried absorbers have an offset distance from the surface of the substrate so that with a minimum effective offset distance, defects and contaminants at the surface of the mask are no longer in the image plane, wherein alleviating a need for a pellicle to protect the mask surface. By reducing light scattering and distortion, the mask of the present invention allows for conventional optical lithography to be extended to ranges of shorter wavelength.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.