Hiroyuki Wakayama

A UV curable resin with reworkable properties: application to imprint lithography

Difunctional methacrylate monomers having a hemiacetal ester moiety in the molecule were used to prepare a plastic replica of an original mold for imprint lithography. UV curing of the monomers was performed with 365 nm light and photo-induced degradation of the cured resins was performed using 254 nm light.

Novel neutral under layer materials to enhance the photolithography performance and defectivity for chemo-epitaxy process

Neutral layer (NL) material is one of the key materials for aligning block-co-polymer (BCP). In this study, NLs were designed and investigated, which have the capability to enhance the photo-lithography performance, a good alignment performance of BCP, and reduce the defectivity after chemo-epitaxy process. In order to enhance the photo-lithography performance, some new polymers were prepared with chromophores to control n/k value and adhesive unit interacted with the photo resist. The surface energy of these materials was adjusted to the neutral for BCP by controlling the ratio of chromophore and adhesion unit. The defects were also investigated and achieved low defectivity by optimized materials. Since this material has the above properties, it shows a good perpendicularly alignment pattern of BCP and a photolithography performance.

Development of Si-HM for NTD process

Negative Tone Development (NTD) process with ArF immersion has been developed for the next generation lithography technology because it shows good resolution performance and process window for C/H and trench patterning. Because of the etch requirement, tri-layer process has been used popularly. However, most of the Si-HM materials are optimized for positive tone development process and most of them show poor lithography performance in NTD process. In this paper, we study the behaviors of Si-HM for NTD process, develop new concepts and optimize the formulation of Si-HM to match the resist for NTD process bellow N28 node device.

Novel resist for replica preparation of mold for imprint lithography

Two types of dimethacrylate which have hemiacetal ester moiety in a molecule were synthesized from difunctional vinyl ethers and methacrylic acid. UV curing of the monomers and photo-induced degradation of the UV cured resins were investigated. On UV irradiation at 365 nm under N2 atmosphere, these dimethacrylates containing 2,2-dimethoxy-2-phenylacetophenone and triphenylsulfonium triflate became insoluble in methanol. The UV cured resins degraded if acids were generated in the system. Present resins were applied to make a plastic replica of mold for imprint lithography and the plastic replica was prepared in good form. The effect of imprint conditions on volume shrinkage of methacrylates was investigated. Dimethacrylate that has adamantyl unit showed a low-shrinkage property.

Orientation control of silicon containing block-co-polymer with resolution beyond 10nm

Directed Self-Assembly (DSA) process is one of the attractive processes for creating the very fine pitch pattern. In this technology, block-co-polymer is the key material to achieve a fine patterning. Many reports are published with Polystyrene-b-Polymethylmethacrylate (PS-b-PMMA) for DSA applications. But it is difficult to achieve the resolution below 10 nm with PS-b-PMMA because of its low chi value. Etching transfer of PS-b-PMMA is also the key issue due to the low etching selectivity between PS and PMMA during dry etching process. In this report, block-co-polymers that include a Si-containing monomer and an organic monomer were synthesized by living anionic polymerization to supply a high resolution and a high etching contrast. These polymers with a low polydispersity demonstrated lamella morphology that can be oriented by thermal annealing with a neutral surface treatment. The effects of underlayer and top-coat materials were investigated to control the block-co-polymer orientation. These block-co-polymers also achieve a high dry etching contrast.

Novel surface treatment materials for aligning block-co-polymer in directed self-assembly processes

Directed Self-Assembly (DSA) process is one of the attractive processes for creating the very fine pitch pattern. Especially, the contact hole shrink processes with block-co-polymer (BCP) or polymer blend materials were attractive processes for creating very small size hole patterns with better CD uniformity compare to general photo-lithography patterning. In general contact hole shrink process, the pattern of Spin-on Carbon Hardmask (SOC) or the photo Resist pattern created by Negative-Tone Development (NTD) process were selected for guide patterns. Since the alignment property of BCP was affected by the surface of these guide materials, it is important to control the surface condition of guide in order to obtain good shrunk contact hole patterns. In this study, we will report the surface treatment materials to control the surface condition of guide patterns such as SOC or NTD resist to achieve the better contact hole shrink performance. These materials were attached to guide pattern surface and controlled the surface energy.

Diffusion of acid from resist to Si-hardmask layer

In a chemically amplified (CA) resist process, photochemically generated acid can diffuse in the resist matrix, inducing the de-protection reactions. The concentration of acid in resist matrix should be constant during the post-exposure-bake (PEB) treatment. In the practical resist processes, bottom anti-reflective coating (BARC) is essentially important to provide reflectivity control for resist patterning. In some cases, however, the photochemically generated acid in resist layer can diffuse into BARC layer, which causes the footing for resist patterns. In this work, we have studied the diffusion of acid from CA resist layer to Si-hardmask (Si-HM) layer. The Si-HM is essential for the multi-layer patterning process. The acid concentration in the resist layer was estimated based on the de-protection reaction kinetics for the CA resist using rapid scan FT-IR spectroscopy. It was found that the acid in resist layer diffused into the Si-HM layer. The diffusion efficiency of the acid was dependent on the crosslinking density of the Si-HM and the chemical structure of the resist.