DOF for both dense and isolated contact holes
US6261727A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 28, 1999 |
| Grant date | Jul 17, 2001 |
| Priority date | — |
| Expiry date | Dec 28, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70308
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A process and apparatus are described for a projection system having improved depth of focus. This has been achieved by introducing into a standard projection system, of the type suitable for photolithography, both a quadrupole mask in the pupil plane of the illuminator lens and a phase-type filter in the pupil plane of the projection lens. Detailed data for the design of both these filters is provided. If these guidelines are followed the result is a projection system whose depth of focus has been increased to a sufficient degree to allow the formation, in a single exposure, of a photoresist wafer suitable for simultaneously etching both isolated and densely packed contact holes.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.