Attenuated phase shift mask comprising phase shifting layer with parabolically shaped sidewalls
US5601954A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 5, 1995 |
| Grant date | Feb 11, 1997 |
| Priority date | — |
| Expiry date | Jun 5, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F1/32
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An attenuated phase shift mask comprises a first layer having a thickness to provide a transmission in the range of about 3 to 10% formed on a transparent substrate and a second layer comprising a transparent material having a thickness to provide a desired phase shift, formed on said first layer. For a phase shift of 180.degree. and i-line wavelength (365 nm), where chromium is used as the first layer, then a thickness within the range of about 25 to 75 run is employed; where silicon dioxide is used as the second layer, then a thickness of about 400 to 450 nm is employed. While the oxide may be dry-etched, an isotropic wet etch provides superior aerial images.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.