Alignment of mask and semiconductor wafer using linear Fresnel zone plate
US4999487A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 21, 1990 |
| Grant date | Mar 12, 1991 |
| Priority date | — |
| Expiry date | May 21, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B5/188
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A system for aligning a mask and a semiconductor wafer comprises radiation source for producing a radiation beam, a dual focus linear Fresnel zone plate provided on the mask for focusing the radiation beam incident thereto on a surface of the semiconductor wafer which comprises a first part having a first focal length and a second part having a second focal length substantially smaller than the first focal length, a diffraction grating provided on the surface of the semiconductor wafer in correspondence to the dual focus linear Fresnel zone plate for diffracting the radiation beam focused thereon, a detector held with a predetermined relationship with respect to the radiation source and the mask for detecting the diffracted beam, a movable stage for supporting the semiconductor wafer, and a controller for moving the stage means responsive to an output signal of the detection means.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.