Method of projecting printing on semiconductor substrate and workpiece including such substrate
US4405229A · kind A · utility
9Cited by
2References
7Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | May 20, 1981 |
| Grant date | Sep 20, 1983 |
| Priority date | — |
| Expiry date | May 20, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/70
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
In the projection-copying of a mask on a workpiece including a light-reflecting semiconductor substrate, the alignment of mask and workpiece is effected by illuminating marks on the substrate which appear dark relative to a surrounding area. To provide each mark with a contrasting background of sufficient brightness, a partly reflecting surface layer overlying the substrate in that area has a nonuniform optical thickness whereby cancellation of reflections due to interference is limited to isolated regions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.