Apparatus for detecting registration marks on a target such as a semiconductor wafer
US4056730A · kind A · utility
5Cited by
2References
7Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Oct 12, 1976 |
| Grant date | Nov 1, 1977 |
| Priority date | — |
| Expiry date | Oct 12, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/3045
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A square shaped beam of charged particles is passed over a registration mark in the surface of a semiconductor wafer. A signal produced by a diode detector that is responsive to backscattered electrons will peak when the beam passes over each of the edges of the registration mark. The signal is differentiated; and the resultant signal is filtered and amplified to provide information regarding the position of the beam with respect to the wafer. If more than one diode detector is used, the signals are added just before or just after the differentiation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.