Frequency‐comb‐referenced multiwavelength interferometry for high‐precision and high‐speed 3D measurement in heterogeneous semiconductor packaging
Jun Hyung Park, Dae Hee Kim, Huy Hoang Chu, Ji Won Hahm, Guseon Kang, Dongil Lee, Seyong Song, Min‐Gu Kang, Seung‐Woo Kim, Young‐Jin Kim
Abstract
Abstract As Moore’s law approaches its physical limits, the semiconductor industry has begun to focus on improving I/O density and power efficiency through 2.5D/3D packaging. Heterogeneous integration, which combines integrated circuit blocks from different linewidth processes into a single package, is central to these developments. To ensure stable connections with high yield in the back‐end processes, high precision and high speed 3D surface measurement is the prerequisite. Existing methods such as white‐light interferometry and confocal microscopy face challenges in balancing resolution, speed, and accuracy in 3D measurements. Here, we report a frequency‐comb‐referenced multiwavelength interferometry for the measurement of 3D sample profiles without 2π phase ambiguity for advanced packaging. Using four frequency‐comb‐referenced wavelengths with a fractional stability of 4.77 × 10 −12 , the measurement range was extended from ∼400 nm ( λ /2) to 1 mm, with the measurement repeatability of 0.258 nm for 32 measurements. The standard step‐height samples with 500‐µm and 4.5‐µm steps, as well as real industrial microbumps in heterogeneous integration packaging, were all successfully measured. Therein, we devised a sequential phase detection method, which enables 5,000 times faster solution determination than the traditional recursive excess fraction method, while maintaining its reliability under noisy conditions. As 2.5D/3D packaging architectures become increasingly complex, our approach will readily meet the critical industrial demands for high‐precision and high‐speed measurement of multiscale features in advanced semiconductor packaging.