The coherence of excimer laser radiation in projection photolithography

• Published in: Microelectronic engineering Vol. 11; no. 1; pp. 173 - 181
• Main Authors: Valiev, K.A., Velikov, L.V., Volkov, G.S., Zaroslov, D.Yu
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 1990; Elsevier Science
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/0167-9317(90)90094-A

The coherence properties of light sources used in the projection lithographic systems strongly affect the photomask image quality reproduced on semiconductor wafer, because they determine the minimum resolvable feature size and the level of speckle in the image. The spatial coherence of excimer laser radiation is measured. A simple relation between the coherence of the excimer laser radiation and its divergency is presented. The dependence of excimer laser coherence on the width of intracavity apertures and the pulse duration is shown. The influence of the spatial coherence on the image quality in the projection system equipped with fly's eye element is considered. The optimization procedure of the radiation parameters and the fly's eye illuminator is described.