Apparatus for, and methods of, determining the characteristics of semi-conductor wafers

US4732473A · kind A · utility

Inventors

• Josef F. Bille · Heidelberg, DE
• Siegfried Hunklinger · Heidelberg, DE

Key dates

• Filing date: Jun 7, 1985
• Grant date: Mar 22, 1988
• Expiry date: Jun 7, 2005

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B21/002
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

This invention enables examination of semi-conductor chips either on a planar basis or on a three-dimensional basis to determine the characteristics of the chips. Laser light is passed through a first pinhole and is focussed on a wafer. The light reflected from the wafer is passed through a second pinhole and is focussed on a photomultiplier. The focal length between the first pinhole and the wafer is the same as the focal length between the second pinhole and the multiplier. This arrangement provides for a high signal-to-noise ratio to be produced and image information data to be provided within minimal time lags such as a small fraction of a second. An electrically controllable active mirror operable within the beam-shaping optics of the scanning field may be included to displace the plane of the examination field. This active mirror may be controlled to assume the shape of different types of mirrors including a planar mirror. By controlling the operation of the active mirror, the etchings of first materials on the wafer and the depositions of other materials on the wafer may be examined at different depths. The control of the active mirror may be provided at a different frequenc…