Photolithographic Process Based on High Contrast Acrylate Photoresist for Multi-Protein Patterning
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Photolithographic Process Based on High Contrast Acrylate Photoresist for Multi-Protein Patterning Margarita Chatzichristidi1, Panagiota S. Petrou2, Antonios M. Douvas1, Constantinos D. Diakoumakos1, Ioannis Raptis1, Konstantinos Misiakos1, Sotirios S. Kakabakos2, and Panagiotis Argitis1 1 Inst of Microelectronics, NCSR Demokritos, Aghia Paraskevi, Athens, 15310, Greece 2 Institute of Radioisotopes and Radiodiagnostics Products, NCSR Demokritos, Aghia Paraskevi, Athens, 15310, Greece
ABSTRACT Continuing the effort of our group for biocompatible, photoresist-based lithographic processes, high contrast, near-UV photoresists are presented along with a novel multi-step lithographic scheme. The proposed lithographic scheme is based on successive lithographic steps (exposure at 310 nm) on the same substrate for the patterning of different proteins. The photoresists are based on (meth)acrylate tetrapolymers and a near UV sensitive sulfonium salt as photoacid generator and can be processed under mild baking and development conditions allowing patterning of proteins without denaturation and loss of their molecular recognition capability. Protein patterning in successive lithographic steps down to 2µm has been achieved. Sub-1µm patterning structures have been also obtained. Lithographic results were evaluated with SEM and fluorescence microscopy, after the recognition of the patterned biomolecules by their fluorescently labeled counterparts. INTRODUCTION Since the first appearance of the semiconductor manufacturing there was a continuous demand for developing new photoresist materials as well as new lithographic tools and techniques with main goal to miniaturize the integrated circuits dimensions. In addition, during the last years lithography has gained the attention of the researchers for applications in other fields like micromachining, microsystem fabrication, nanomaterials and soft matter patterning. In this context increased research effort has been focused towards materials and processes suitable for patterning biomolecules, a critical step in biosensor fabrication and other nanobiotechnology applications. Thus, different approaches such as microspotting, soft lithography, scanning probe lithography and direct photopatterning have been proposed [1-5]. However, the photoresist-based processes are still limited [6-8] in this area and are used mainly for the patterning of surface modifying layers and for oligonucleotide synthesis. In the present paper new near UV photoresists as well as a new lithographic multi-step scheme are presented for the fabrication of submicron protein microarrays following the direction proposed by our group few years ago [9-11]. Successful patterning of different proteins in ten successive lithographic cycles is demonstrated through optimization of the resist material contrast and the processing conditions. Resolution can reach the range allowed by the exposure tool used, reaching half micron with a near UV mask aligner.
EXPERIMENTAL DETAILS The copolymer synthesis has been carri
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