Fine-Pitch RDL with Excellent Signal Transmission Performance Formed on Glass for Heterogeneous Integration

As the industry moves toward High Performance Computing(HPC) for huge data transmission with low power consumption. The requirements for PKG structure have become more challenging. The major engineering requirements for HPC application are high-density, high-speed data transmission, low loss, precision manufacturing with low-cost process. High pin count need large area package with high mechanical stability and low warpage. The demand for high density and high-speed data transmission becomes strong needs for leading edge semiconductor packaging. 2.5D and 3D heterogenous package realize this solution. On the 2.5D heterogenous package structure, key technology is fine wiring connected with CPU chip and HBM chips. The fine wires needed high speed transmission. Silicon interposers with through silicon vias (TSVs) have developed to meet this demand, but face three major barriers high electrical loss, package size and cost. On the other hand, glass has many properties that make it an ideal substrate for BGA core substrates such as ultra-low loss tangent, adjustable thermal expansion (CTE), mechanical stability and manufacturability with large panel size. This paper presents the demonstration of Fine line Redistribution Layer (RDL) on Glass and Glass Core Substrate with fine pitch metalized through via. The ultra-high density RDL process using non-organic protective layer fabricated on the glass substrate. High aspect ratio 3 traces enable to minimum 3um pitch, high transmission rate and high reliability. We also focus on the potential for applying high-speed transmission performance to the next generation such as HBM3 and UCIe 1.0 based on the analysis of electromagnetic field simulation and the measurement results obtained from the fine pitch wiring composed on the glass material. We conducted experimental measurement on the electrical transmission characteristics of fine-wiring with a width ranging from 1.5 µm to 3 µm. Furthermore, our proposed fine wiring structure of covered with inorganic material had less influence on signal transmission performance. We have done actual measurement comparison with inorganic protective layers and without inorganic protective layers. we checked a comparative evaluation of eye patterns using measured S-parameters at the high-speed signal transmission condition with transient analysis. Furthermore, we utilized the obtained measurement results to validate their applicability for next- generation high-speed transmission, and we report the findings of our verification.