Advanced imaging with 1.35 NA immersion systems for volume production

摘要

The semiconductor industry has adopted water-based immersion technology as the mainstream high-end litho enabler for 5x-nm and 4x-nm devices. Exposure systems with a maximum lens NA of 1.35 have been used in volume production since 2007, and today achieve production levels of more than 3400 exposed wafers per day. Meanwhile production of memory devices is moving to 3x-nm and to enable 38-nm printing with single exposure, a 2nd generation 1.35-NA immersion system (XT:1950Hi) is being used. Further optical extensions towards 32-nm and below are supported by a 3rd generation immersion tool (NXT:1950i).This paper reviews the maturity of immersion technology by analyzing productivity, robust control of imaging, overlay and defectivity performance using the mainstream ArF immersion production systems. We will present the latest results and improvements on robust CD control of mainstream 4x-nm memory applications. Overlay performance, including on-product overlay control is discussed. Immersion defect performance is optimized for several resist processes and further reduced to ensure high yield chip production even when exposing more than 15 immersion layers.