Kenji Kitaoka

Design, fabrication and characterization of low-cost glass interposers with fine-pitch through-package-vias

This paper demonstrates thin glass interposers with fine pitch through package vias (TPV) as a low cost and high I/O substrate for 3D integration. Interposers for packaging of ULK and 3D-ICs need to support large numbers of die to die interconnections with I/O pitch below 50 μm. Current organic substrates are limited by CTE mismatch, wiring density, and poor dimensional stability. Wafer based silicon interposers can achieve high I/Os at fine pitch, but are limited by high cost. Glass is an ideal interposer material due to its insulating property, large panel availability and CTE match to silicon. The main focus of this work is on a) electrical and mechanical design, b) TPV and fine line formation and c) integration process and electrical characterization of thin glass interposers. This work for the first time demonstrates high throughput formation of 30 μm pitch TPVs in ultrathin glass using a parallel laser process. An integration process was demonstrated for glass interposer with polymer build-up layers on both sides. The glass interposer had stable electrical properties up to 20GHz and low insertion loss of less than 0.15dB was measured for TPVs at 9GHz.

TGV technology for Glass interposer

This study explored glass microfabrication technologies for TGV (Through Glass Via) formation can be applied interposer substrate of 3D packaging. Two TGV formation methods were studied and compared such as optical approach using Excimer laser and electrical approach using focused electrical discharging. Demonstration of laser microfabrication showed the result of 40um pitch of TGVs which is able to be fine pitch solution. And demonstration of focused electrical discharging method showed the result of ultrafast TGV process with 75um pitch. In this study, we compared characteristic of both technologies and pointed necessary future development for glass interposer application.