High performance filtration for bulk materials: a novel HDPE membrane filter designed for EUV Lithography

Abstract

Extreme Ultra-Violet (EUV) lithography is pushing material suppliers to provide the cleanest possible products for tight quality standards. The emphasis on minimizing residual particles, metals, and organics coming from materials and equipment continues to increase. Filter design and its key sub-components such as membrane continue to play a significant role to enhance performance in EUV lithography by reducing defectivity. This necessitates an improvement in retention and cleanliness for both bulk and point-of-use (POU) filters. While POU filtration targets high retention, typica lly achieved by membrane's reduced pore size, the main requirement of bulk filtration is maximizing the amount of material recirculated through the filter per unit of time and is achieved with improved tortuosity and well-defined pore structure.

In this study, we present a novel HDPE filter specifically designed to provide a high flow (lower differential pressure) without sacrificing retention characteristics. The new membrane was assembled in a POU filter format and compared head-to-head with a state-of-the-art HDPE membrane filter for POU application. The flow performance was assessed by differential pressure (dP) measurement, which showed an enhanced performance benefit of dP reduction by 50% compared to the reference filter, while all other test parameters are improved or at least comparable. The filter cleanliness was quantified by liquid particle counter (LPC), GC-MS, and ICP/MS measurements. Finally, comparative defect data was obtained from the blanket and pattern wafers, prepared on imec EUV cluster comprised of TEL Clean Track LITHIUS Pro-Z and ASML NXE:3400B with a 16nm L/S test vehicle.