Habib Hichri

Novel Process of RDL Formation for Advanced Packaging by Excimer Laser Ablation

The continuous trend in miniaturization, increasing performance and mobility of electronic devices drives not only the requirements of the chip itself, but also its package type. The current integration processes encompassing photolithography may be reaching their capability limits for developing cost effective and innovative package designs to meet the markets most stringent requirements. In addition, there are significant challenges in these legacy processes that manufactures will need to overcome. In support of this technology trend and to address the current photolithography process integration challenges, we introduce excimer laser ablation as a direct patterning process that uses proven industrialized excimer laser sources to emit high-energy pulses at short wavelengths to remove materials. The combination of a high-power excimer laser source, large-field laser mask and precision projection optics enables the accurate replication and placement of fine resolution circuit patterns without the need for any wet-processing. In addition, with excimer laser patterning technology the industry gains a much wider choice of dielectric materials (photo and non-photo) to help achieve further reductions in manufacturing costs as well as enhancements in chip or package performance. In this paper, we propose a new process based on the front-end-of-line (FEOL) dual damascene integration flow for building multilayer embedded RDL for Advanced Packaging. The new process uses excimer laser ablation to integrate via and RDL traces in one patterning process step, followed by seed layer deposition, plating and planarization processes. We will explain in detail the new proposed integration flow and further demonstrate its technical robustness and commercial advantages. We will also cover the capability of this excimer laser process to extend the current material portfolio to non-photo materials and highlight its commercial benefits as compared to the current process of record (POR).

Innovative laser enabled dual damascene process for ultra-fine line multi-layer routing for advanced packaging

Fan out wafer level packaging (FOWLP) continues to be the main driver for advanced packaging. The major application nowadays is the single chip packaging with low routing. The continuous trend towards miniaturization, increasing performance and mobility of electronic devices drives interconnect density and integration, not only at the chip level, but also at interposer and package level. However, there is a continuing need for low cost packaging. While traditional organic flip-chip substrates using semi-additive processes (SAP) have not been able to scale to ultra-fine RDL pitches and via opening below 10um, photo-sensitive spin-on dielectrics and RDL processes used for wafer level packaging do not sufficiently address the cost reduction need. This paper presents the latest results from cost effective and innovative package RDL and micro via processes using excimer laser ablation, to meet the markets most stringent requirements. To enable panel and wafer based interposers to reduce RDL cost and scale interconnect pitch to 40um and below, excimer laser ablation is introduced as a direct patterning process that uses proven industrialized excimer laser sources to emit high-energy pulses at short wavelengths to remove polymer materials with high precision and high throughput. The combination of a high-power excimer laser source, large-field laser mask and precision projection optics enables the accurate replication and placement of fine resolution circuit patterns without the need for any wet-processing. In addition, with excimer laser patterning technology the industry gains a much wider choice of dielectric materials (photo and non-photo) to help achieve further reductions in manufacturing costs as well as enhancements in interposer and package performance. In this paper, we propose new pattering process that uses excimer laser ablation to integrate via and RDL traces in one patterning process step, followed by seed layer deposition, plating and planarization steps. A new integration process flow is proposed, and its technical robustness and commercial advantages have been demonstrated. The capability of this excimer laser patterning process in non-photo materials will be discussed. We will present electrical and reliability data of Via and RDL traces patterned by Excimer laser in non photo material. The commercial benefits of the new laser based patterning process as compared to the current process of record (POR) will be highlighted.

Embedded Trench Redistribution Layers (RDL) by Excimer Laser Ablation and Surface Planer Processes

This paper reports the demonstration of 2-5 µm embedded trench formation in dry film polymer dielectrics such as Ajinomoto build-up film (ABF) and Polyimide without using chemical mechanical polishing (CMP) process. The trenches in these dielectrics were formed by excimer laser ablation, followed by metallization of trenches by copper plating processes and overburden removal with surface planer tool. The materials and processes integrated in this work are scalable to large panel fabrication at much higher throughput, for interposers and high density fan-out packaging at lower cost and higher performance than silicon interposers.

Innovative Excimer Laser Dual Damascene Process for Ultra-Fine Line Multi-layer Routing with 10 µm Pitch Micro-Vias for Wafer Level and Panel Level Packaging

The demands of higher routing density on wafer level are driven by multi-chip integrated fan-out packages and high I/O CSPs. New technologies and materials are necessary to generate lines and spaces down to 2 µm. Multi-metal layers are necessary for the higher wiring effort on panel level packaging (PLP) for example to contact dies which are embedded together. This places higher demands on the mechanical properties of the materials that are used for the redistribution layer. This paper presents a new excimer laser-enabled dual damascene process for ultra-fine routing for BEOL which was developed in a joint project with SUSS MicroTec. In the project, various materials e.g. low temperature cure polyimide, BCB and dry-film ABF materials were structured by using an excimer laser stepper with a reticle mask to pattern feature sizes below 4 µm with a high throughput. Micro-vias with a diameter below 5 µm were ablated with an aspect ratios up to 4 which is exceeding the photolithographic resolution limits of the established photosensitive thin-film polymers. The laser structuring allows the usage of innovative dielectric materials for WLPs/PLPs with optimized mechanical and electrical parameters, for example polymers with inorganic fillers like dry-film ABF material. Also, the ablations depth per laser pulse was investigated. The ablated lines and micro-vias were metallized by applying a galvanic process and CMP. The stepper-like system allows a sub-micron alignment accuracy with no need of a capture pad in the redistribution layers. Test multi-layer structures have been designed and fabricated with lines and spaces below 10 µm to demonstrate the dense routing capability with an excellent reliability which was verified by air-to-air thermal cycling (from -55 °C up to 125 °C).