High Resolution Dry Film Photo-imageable Dielectric Enabling Dual-side Panel Level Fine Line RDL

There is an increasing demand for advanced substrates and interposers with fine line RDL to support complex 2.5D/3D packaging structures and thereby increasing data rate transmission on substrates/interposers. In addition, multiple interposer material designs, such as organic, glass, and silicon, are being explored in the industry to suit a wide variety of end applications. Novel dielectric dry film materials are needed to meet this demand across different designs. Filler-rich buildup films are well-suited for panel-level processing and have a well-established track record for reliability. With nanofiller technology, buildup film resolution has significantly improved. However, it remains a challenge for this strategy to deliver a smooth interface with high filler content and achieve high throughput with the laser ablation process. While polyimide-based materials have shown good utility in wafer level applications, they face additional rheological challenges in a dry film format, limiting their conformal planarization performance over topology and through cavity filling, such as through glass vias (TGV) and die-encapsulation in substrates. To meet the needs for finer pitch redistribution layer (RDL) designs with panel-level processing, the CYCLOTENETM photoimageable dielectric (PID) dry film (DF) platform has been developed. This PID platform is based on an aqueous-developable benzocyclobutene (AD-BCB) material and is suitable for embedded trace dual damascene processes with plasma descum and sputtering for seed layer deposition. The AD-BCB based PID has excellent cavity filling capability via vacuum lamination and is able to fill void-free up to 100µm diameter TGVs in a 400µm thick glass panel with 20µm thickness PID dry film. Over L/S 10/10µm Cu trace, 10µm PID dry film can achieve perfect filling between Cu traces without detectable top surface dimples with a two-stage Meiki laminator. Early generation DF6800 PID has been fabricated over a wide range of coating thicknesses, from 5µm to 40µm, with <10% thickness variation. DF6800 has high resolution patterning capability for single-side PET-off processing. It can achieve >2:1 aspect ratio for 20µm films with i-line stepper or LDI lithographic exposure tools. Cured films have passed bias HAST testing (130°C, 85% RH, 96hr, 5V) with line space patterning of 13 µm and 9 µm with no change in resistance and no copper dendrite formation. To further improve the utilization of the CYCLOTENE™ PID dryfilm platform in panel-level processing, a new generation of PID DF6800M has been developed to enable a PET-on dual-sided RDL buildup process. DF6800M is a PFAS-free formulation with a US-based material and supply chain. It is self-priming on Cu surfaces treated with MEC Etch Bond CZ8401 and achieves a 5B rating in the cross-hatch peel test post 96hr HAST. It retains high-resolution patternability with a low NA stepper, achieving <10µm vias and <7µm trenches on a copper-coated substrate treated with MEC Etch Bond CZ8100 & CZ8401. Furthermore, DF6800M demonstrates robust post exposure delay (PED) stability for more than 24 hours. Since DF6800M is based on the same AD-BCB material, we expect it to deliver the same excellent cavity filling capability and reliability performance as demonstrated by DF6800. Based on these attributes, we believe DF6800M is highly suitable as a photo-imageable dielectric for advanced substrates and interposers needing fine line RDL required by 2.5D and 3D advanced heterogeneous chiplet integration schemes.