Self-Aligned Thin-Film Patterning by Area-Selective Etching of Polymers

Patterning of thin films with lithography techniques for making semiconductor devices has been facing increasing difficulties with feature sizes shrinking to the sub-10 nm range, and alternatives have been actively sought from area-selective thin film deposition processes. Here, an entirely new method is introduced to self-aligned thin-film patterning: area-selective gas-phase etching of polymers. The etching reactions are selective to the materials underneath the polymers. Either O2 or H2 can be used as an etchant gas. After diffusing through the polymer film to the catalytic surfaces, the etchant gas molecules are dissociated into their respective atoms, which then readily react with the polymer, etching it away. On noncatalytic surfaces, the polymer film remains. For example, polyimide and poly(methyl methacrylate) (PMMA) were selectively oxidatively removed at 300 °C from Pt and Ru, while on SiO2 they stayed. CeO2 also showed a clear catalytic effect for the oxidative removal of PMMA. In H2, the most active surfaces catalysing the hydrogenolysis of PMMA were Cu and Ti. The area-selective etching of polyimide from Pt was followed by area-selective atomic layer deposition of iridium using the patterned polymer as a growth-inhibiting layer on SiO2, eventually resulting in dual side-by-side self-aligned formation of metal-on-metal and insulator (polymer)-on-insulator. This demonstrates that when innovatively combined with area-selective thin film deposition and, for example, lift-off patterning processes, self-aligned etching processes will open entirely new possibilities for the fabrication of the most advanced and challenging semiconductor devices.

Precise Synthesis and Thin Film Self-Assembly of PLLA-b-PS Bottlebrush Block Copolymers

The ability of bottlebrush block copolymers (BBCPs) to self-assemble into ordered large periodic structures could greatly expand the scope of photonic and membrane technologies. In this paper, we describe a two-step synthesis of poly(l-lactide)-b-polystyrene (PLLA-b-PS) BBCPs and their rapid thin-film self-assembly. PLLA chains were grown from exo-5-norbornene-2-methanol via ring-opening polymerization (ROP) of l-lactide to produce norbornene-terminated PLLA. Norbonene-terminated PS was prepared using anionic polymerization followed by a termination reaction with exo-5-norbornene-2-carbonyl chloride. PLLA-b-PS BBCPs were prepared from these two norbornenyl macromonomers by a one-pot sequential ring opening metathesis polymerization (ROMP). PLLA-b-PS BBCPs thin-films exhibited cylindrical and lamellar morphologies depending on the relative block volume fractions, with domain sizes of 46–58 nm and periodicities of 70–102 nm. Additionally, nanoporous templates were produced by the selective etching of PLLA blocks from ordered structures. The findings described in this work provide further insight into the controlled synthesis of BBCPs leading to various possible morphologies for applications requiring large periodicities. Moreover, the rapid thin film patterning strategy demonstrated (>5 min) highlights the advantages of using PLLA-b-PS BBCP materials beyond their linear BCP analogues in terms of both dimensions achievable and reduced processing time.

Colloidal Self-Assembly of Inorganic Nanocrystals into Superlattice Thin-Films and Multiscale Nanostructures

The self-assembly of colloidal inorganic nanocrystals (NCs) offers tremendous potential for the design of solution-processed multi-functional inorganic thin-films or nanostructures. To date, the self-assembly of various inorganic NCs, such as plasmonic metal, metal oxide, quantum dots, magnetics, and dielectrics, are reported to form single, binary, and even ternary superlattices with long-range orientational and positional order over a large area. In addition, the controlled coupling between NC building blocks in the highly ordered superlattices gives rise to novel collective properties, providing unique optical, magnetic, electronic, and catalytic properties. In this review, we introduce the self-assembly of inorganic NCs and the experimental process to form single and multicomponent superlattices, and we also describe the fabrication of multiscale NC superlattices with anisotropic NC building blocks, thin-film patterning, and the supracrystal formation of superlattice structures.

Silicon Wafer Integrated Fan-out Technology

The tremendous growth in the mobile handset, tablet, and networking markets has been fueled by consumer demand for increased mobility, functionality, and ease of use. This, in turn, has been driving an increase in functional convergence and 3D integration of IC devices, resulting in the need for more complex and sophisticated packaging techniques. A variety of advanced IC interconnect technologies are addressing this growing need. These include Through Silicon Via (TSV), Chip-on Chip (CoC), and Package-on-Package (PoP) approaches. In particular, emerging Wafer Level Fan-Out (WLFO) technology provides unique and innovative extensions into the 3D packaging realm. Traditional WLFO technologies are limited in design rules and 3D integration capabilities due to the processes and equipment used for circuit patterning. For more aggressive designs, TSV processes must be incorporated, which often times exceed the cost budget and design requirements needed for the device. Consequently, a gap exists between the design capabilities of WLFO and TSV that needs to be addressed. A new, innovative fan-out structure called Silicon Wafer Integrated Fan-out Technology (SWIFT™) packaging incorporates conventional WLFO processes with leading-edge thin film patterning techniques to bridge the gap between TSV and traditional WLFO packages. The SWIFT methodology is designed to provide increased I/O and circuit density within a reduced footprint and profile for single and multi-die applications. The improved design capability of the technology is due, in part, to the fine feature capabilities associated with this new, innovative wafer-level packaging technique. The fine feature capabilities can allow much more aggressive design rules to be applied compared to competing WLFO and laminate-based technologies. In addition, the unique characteristics of the SWIFT process enable the creation of innovative 3D structures that address the need for IC integration in emerging mobile and networking applications. This paper will review the development of the SWIFT technology and its extension into unique 3D structures. In addition, the advantages of SWIFT designs will be reviewed in comparison to current competing packaging technologies. Process information, material characterization, and design simulation data will be presented to show how the SWIFT process is poised to provide robust, reliable, and low-cost 3D packaging solutions for advanced mobile and networking products. SWIFT is a trademark of Amkor Technology, Inc.