Early Zone Correction for Enhanced Overlay Precision in Next-Generation FOPLP Lithography

By John Chang

Abstract

Advanced packaging technologies, such as ultra high density fan out packaging and 2.5D/3D integration, are essential for the continued advancement of chiplet-based AI applications. Achieving the stringent manufacturing requirements for AICS: specifically larger packaging areas, reduced line and space dimensions, finer ball pitches, and increased layer counts; necessitates the implementation of sophisticated lithography processes characterized by extremely large exposure fields coupled with fine resolution capabilities.

Despite these lithographic advancements, significant challenges persist, particularly concerning overlay accuracy. Overlay errors frequently result from alignment solution inaccuracies and can severely limit the achievable overlay yield, posing substantial impediments to scaling advanced packaging technologies. Addressing alignment solution errors effectively is critical for meeting the increasingly strict overlay budgets anticipated for next generation AI driven applications.

This study rigorously investigates process-induced alignment solution errors within large-panel lithography processes. By systematically analyzing overlay measurement data from a 510mm × 515mm panel substrate, we quantify and characterize alignment solution errors and their direct impact on overlay precision. Further, we propose an innovative early zone correction technique aimed at compensating alignment inaccuracies during the lithographic exposure phase. The early zone correction approach leverages algorithmic analysis to identify correctable zone-based overlay error components, subsequently applying these corrections proactively during lithographic exposure. The efficacy of this approach was validated experimentally using substrates exhibiting known alignment errors. The experimental outcomes indicate substantial improvements in overlay precision and yield, underscoring the robustness of early zone correction in addressing alignment inaccuracies. These findings demonstrate that the combination of extremely large exposure field lithography, fine resolution capability, and early zone correction significantly mitigates the overlay challenges inherent to advanced packaging manufacturing.