Film and CD Metrology Solutions for Critical Challenges in Advanced Packaging

Abstract

Advanced packaging (AP) technologies introduce unique metrology challenges due to the diversity of materials, structures, and substrate conditions. This work presents a set of optical metrology solutions designed to address four critical application areas in advanced 2.5D/3D IC manufacturing: 

1. Thin and Thick Film Metrology:
   AP processes involve a wide range of film thicknesses, from ultra-thin CMP stop layers to thick polymer coatings such as photoresist and polyimide. Accurate measurement across this broad range (20 Å to 150 µm) is achieved using a dual-channel optical approach combining spectroscopic ellipsometry and reflectometry. This enables precise control of film stacks essential for dielectric isolation, planarization, and mechanical support. 

1. TSV Depth and Profile Measurement:
   Through-silicon vias (TSVs) are central to 3D integration but pose significant metrology challenges due to their high aspect ratios and depth variability. The proposed solution provides non-destructive, high-resolution depth measurements using model-based optical critical dimension (OCD) techniques, ensuring process control and structural integrity. 

1. Copper Dishing and Recess Characterization:
   Cu dishing during chemical-mechanical polishing (CMP) can degrade electrical performance and reliability. The metrology system enables accurate measurement of Cu recess and step height, supporting process optimization and uniformity control across the wafer. 

1. Wafer Handling for Warped and Non-Standard Substrates:
   AP often involves thinned, bonded, or glass wafers, which are prone to warpage and mechanical instability. The system supports up to 4 mm warpage and accommodates heavy substrates and film frame carriers, enabling reliable metrology on fragile or non-planar wafers. 

These application-focused solutions provide a robust metrology framework to support yield improvement, process control, and design enablement in advanced packaging environments.