Apparatus for measuring the distribution of irregularities on a mirror surface
US4291990A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 22, 1979 |
| Grant date | Sep 29, 1981 |
| Priority date | — |
| Expiry date | Jan 22, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/88
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An optical apparatus for measuring irregularities on the mirror surface of, for example, a silicon wafer used to provide a semiconductor integrated circuit. Irradiates on the mirror surface light fluxes arranged in a special form, for example, in the lattice form. By observing the pattern of light fluxes reflected from said mirror surface, one can measure the surface irregularities. A light flux issued from a light source is divided by a photomask or diffraction grating into first light fluxes irradiated all over the mirror surface and second light fluxes surrounding the respective first light fluxes in the continuous or discontinuous annular form, thereby ensuring the simultaneous measurement of the distribution of extensive irregularities over the entire mirror surface by the first light fluxes and the distribution of local irregularities on said mirror surface by the second light fluxes.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.