Efficient phase defect detection system and method

US6674522B2 · kind B2 · utility

Assignee

• KLA-Tencor Technologies Corp. · US

Inventors

• Matthias C. Krantz · Altenholz, DE
• Mark J. Wihl · San Jose, US
• Stanley Stokowski · Danville, US

Key dates

• Filing date: May 4, 2001
• Grant date: Jan 6, 2004
• Expiry date: May 30, 2021

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F1/26
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The ability to inspect photomasks for errors or defects in phase-shifters is greatly enhanced using optical techniques based on multiple modified radiation collection techniques. In particular, the apparatus and methods of the invention allows for errors in phase-shifters to be more accurately detected, even in the presence of regular amplitude objects such as grid lines. In one embodiment, the intensities of two slightly defocused images of phase objects corresponding to the same photomask location are compared. In a second embodiment, radiation having two Zernike point spread functions is used to obtain two slightly different phase sensitive images. Data collected and analyzed using this method provides much greater sensitivity to phase objects and errors in phase objects than prior art inspection systems. Embodiments include both scanning-type and projector-type optical architectures and may utilize radiation transmitted or reflected by a sample.