Dynamic focus adjustment with optical height detection apparatus in electron beam system

摘要

The present invention generally relates to dynamic focus adjustment for an image system. With the assistance of a height detection sub-system, present invention provides an apparatus and methods for micro adjusting an image focusing according the specimen surface height variation by altering the field strength of an electrostatic lens between objective lens and sample stage/or a bias voltage applied to the sample surface. Merely by way of example, the invention has been applied to a scanning electron inspection system. But it would be recognized that the invention could apply to other system using charged particle beam as observation tool with a height detection apparatus.

主权项

1. A device for dynamic measuring height variation of a specimen to be inspected by a tool, comprising:
an optical illuminating source for emitting light on the specimen; a detecting unit for receiving light reflected from the specimen; means for calculating a focus of the tool; means for calculating bias of the specimen surface to a voltage according to the focus and scanning compensation while the specimen is inspected by a charged particle beam; and means for controlling bias of the specimen surface to the voltage.