Ya-Mi Chuang

EUVL compatible LER solutions using functional block copolymers

Directed self assembly (DSA) of block copolymers is an emerging technology for achieving sub-lithographic resolution. We investigate the directed self assembly of two systems, polystyrene-block-poly-DL-lactic acid (PS-b-PDLA) and PSb- poly(methyl methacrylate). For the PS-b-PDLA system we use an open source EUVL resist and a commerciallyavailable underlayer to prepare templates for DSA. We investigate the morphology of the phase separated domains and compare the LER of the resist and the PS-PDLA interface. For the PS-b-PMMA system we again use an open source resist, but the annealing conditions in this case require crosslinking of the resist prior to deposition of the block copolymer. For this system we also investigate the morphology of the phase separated domains and compare the LER of the resist and the PS-PMMA interface.

Non-CA resists for 193 nm immersion lithography: effects of chemical structure on sensitivity

Initial studies are presented on the use of polysulfones as non-chemically amplified resists (non-CARs) for 193 nm immersion lithography. Polynorbornene sulfone films on silicon wafers have been irradiated with 193 nm photons in the absence of a photo-acid generator. Chemical contrast curves and contrast curves were obtained via spectroscopic ellipsometry and grazing angle - attenuated total reflectance FTIR spectroscopy. Results were consistent with previously reported mechanisms for the degradation of aliphatic polysulfones with ionizing radiation. It was shown that E0 values could be reduced significantly by using a post exposure bake step, which propagated depolymerization of the polymer. Initial patterning results down to 50 nm half pitch were demonstrated with EUV photons.

Healing LER using directed self assembly: treatment of EUVL resists with aqueous solutions of block copolymers

Overcoming the resolution-LER-sensitivity trade-off is a key challenge for the development of novel resists and processes that are able to achieve the ITRS targets for future lithography nodes. Here, we describe a process that treats lithographic patterns with aqueous solutions of block copolymers to facilitate a reduction in LER. A detailed understanding of parameters affecting adhesion and smoothing is gained by first investigating the behavior of the polymers on planar smooth and rough surfaces. Once healing was established in these model systems the methodology is tested on lithographically printed features where significant healing is observed, making this a promising technology for LER remediation.

Electron-Beam-Induced Freezing of an Aromatic-Based EUV Resist: A Robust Template for Directed Self-Assembly of Block Copolymers

Resist freezing is routinely used in lithography applications to facilitate double patterning and the directed self-assembly (DSA) of block copolymers. Previous reports of graphoepitaxy within patterned positive-tone resists used chemical freezing agents which are known to cause significant shrinkage of critical dimensions (CD). We report the “freezing” of an aromatic-based extreme ultraviolet resist by exposure to an electron beam, so did not require the use of chemical agents. Crucially, the process did not lead to significant changes in CD and line edge roughness, where the “frozen” patterns were resistant to treatment with solvents and annealing to temperatures well above the glass transition temperature of the uncrosslinked resist. Finally, we take advantage of these properties and demonstrate the utility of this process for applications in the DSA of block copolymers leading to pattern multiplication.

Electron beam induced freezing of positive tone, EUV resists for directed self assembly applications

The commercialization of 32 nm lithography has been made possible by using double patterning, a technique that allows for an increased pattern density, potentially, through resist freezing and high precision pattern registration. Recent developments in directed self assembly (DSA) also uses resist freezing for stabilizing positive tone resists used in graphoepitaxy. We have developed a method of patterning an open source, positive tone EUV resist using electron beam lithography (EBL), and studied a novel way of freezing a positive tone EUV photoresists through electron beam induced crosslinking. Through metrological analysis, crosslinked pattern was observed to retain consistent critical dimensions (CD) and line-edge roughness (LER) after they were annealed at temperatures higher than the glass transition of the photoresist. This process has been used to freeze patterned EUV photoresists, which have been subsequently used for directed self assembly of PS-b-PMMA and has potential applications in double patterning in an LFLE scenario.