Shang-Chen Wu, Ying-Hung Chen, Ping-Yen Hsieh, Ju-Liang He, Feng Chia University, Taiwan
Glass has emerged as a promising interposer material for advanced 2.5D and 3D IC (integrated circuit) packaging due to its excellent thermal, mechanical, and dielectric properties. In such architectures, TGV (Through-Glass Via) technology plays a vital role in enabling vertical electrical interconnections. However, the HAR (high-aspect-ratio) geometry and insulating nature of glass impose substantial challenges on the PVD (physical vapor deposition) of copper seed layers. Conventional sputtering often leads to inadequate sidewall coverage, weak adhesion, and void formation, thereby degrading the uniformity and reliability of subsequent via-filling processes.
To address these limitations, this study proposes a TGV metallization strategy using HiPIMS (High-Power Impulse Magnetron Sputtering) for copper seed-layer deposition. The high-density metal-ion flux and energetic ion bombardment intrinsic to HiPIMS were exploited to enhance film conformality and adhesion. Process parameters- including working pressure, target-to-substrate distance, and HiPIMS power- were systematically varied to evaluate their effects on film coverage. OES (Optical emission spectrometry) monitoring was employed to optimize the ion-to-neutral ratio within the plasma.
Experimental results confirm that HiPIMS enables the deposition of uniform, dense, and conformal Cu seed layers within TGV structures exhibiting an aspect ratio of approximately 10:1. The thickness distribution along the via sidewalls was quantitatively analyzed, and electrical resistance measurements across the glass substrate verified continuous conductive pathways. This work effectively resolves the long-standing challenges of seed-layer deposition in glass vias and demonstrates a reliable, scalable, and environmentally compatible route toward robust metallization for high-density advanced packaging applications.