Pellicle reflectivity monitoring system having means for compensating for portions of light reflected by the pellicle

US5717198A · kind A · utility

Assignee

• QC Optics, Inc. · US

Inventors

• Sergey V. Broude · Newton, US
• Nicholas Allen · Bedford, US
• Abdu Boudour · Newton, US
• Eric Chase · Andover, US
• Carl Johnson · Pilot Point, US
• Pascal Miller · North Chelmsford, US
• Jay Ormsby · Salem, US

Key dates

• Filing date: Jul 10, 1995
• Grant date: Feb 10, 1998
• Expiry date: Jul 10, 2015

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/94
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A pellicle reflectivity monitoring system comprising a radiation source for directing radiation through a pellicle to an object to be inspected, a sensor device positioned to receive the portion of the radiation reflected by the pellicle, a processor, responsive to the sensor device, for determining the intensity of the portion of the radiation reflected by the pellicle, and a lens assembly, positioned in an optical path between the pellicle and the sensor device, for directing the portion of the radiation reflected by pellicles of different heights onto the sensor device. A comparator device compares the intensity of the radiation directed at the object to be inspected with the intensity of the portion of the radiation reflected by the pellicle and outputs a correction factor based on the comparison in order to compensate for the portion of the radiation reflected by the pellicle.