Preparation and properties of nano-silica modified negative acrylate photoresist Chih-Kang Lee, Trong-Ming Don, Wei-Chi Lai, Chin-Chung Chen, Dar-Jong Lin, Liao-Ping Cheng ⁎ Department of Chemical and Materials Engineering, Tamkang University, Taipei, 25137, Taiwan Received 30 May 2007; received in revised form 25 February 2008; accepted 7 April 2008 Available online 12 April 2008 Abstract A series of silica modified photoresists had been successfully developed through incorporation of a particular nanoparticles suspension. Free radical polymerization was employed to synthesize the binder, an acrylate copolymer resin of benzyl methacrylate, methacrylic acid and 2- hydroxyethyl methacrylate, of the photoresist. The acid value, viscosity, molecular weight and thermal properties of the formed binders were measured. Then, surface-modified silica particles prepared by the sol–gel method were introduced to the photoresist. Because the modified silica particles contained considerable amount of reactive double bonds (CfC) on their surfaces, they would react with the polyfunctional monomers in the photoresist to form an organic–inorganic nanohybrid. Fourier transform infrared spectrometer was used to analyze the evolution of chemical bonds at various stages of the preparation process. Thermal analyses including thermal gravimetric analyzer, differential scanning calorimeter and thermo-mechanical analyzer were used to evaluate the level of enhancement on thermal and dimensional stabilities of the photoresist due to silica incorporation. © 2008 Elsevier B.V. All rights reserved. Keywords: Photoresist; Binder; Sol–gel method; Organic–inorganic nanohybrid 1. Introduction Photoresists are widely used for the manufacture of microelectronics, silk screen printings, printed circuit boards, optical disks, color filter resists and so on. The recipe of a common negative-type photoresist consists of a binder, photo- sensitive polyfunctional monomer, photoinitiator, solvents and pigments [1–5]. For a photoresist applied in color filter, the binder plays a vital role, as it determines the adhesion strength, hardness, heat resistance, and developability of the photoresist [6]. In this research, a series of binders was synthesized from free radical copolymerization of three kinds of acrylate monomers benzyl methacrylate (BZMA), methacrylic acid (MAA), and 2- hydroxyethyl methacrylate (2-HEMA). The synthetic route of these binders is outlined in Scheme 1. The thermal behaviors, molecular weights, and acid values of the prepared binders were measured and compared so as to optimize the thermal mechanical and chemical stability properties of the photoresist. Organic–inorganic hybrid materials have been extensively investigated in recent years [7–13]. Organic polymers, as characterized by good flexibility, ductility and processability, have long been applied in various industries. In contrast, inorganic materials possess properties, such as high rigidity, mechanical strength, and thermal stability that are not achievable by polymers. Combination of the advantages of these two classes of materials to yield a composite with superior properties that meet the industrial standards is nowadays highly demanded. To prepare such organic–inorganic hybrid materials, a modified sol–gel process is generally used. Sol–gel process was originally developed for the low-temperature synthesis of glass or ceramic materials, which involves consecutive hydro- lysis and condensation of an alkoxysilane to form silicone oxide particles that suspend in an aqueous/alcoholic solution; e.g., silica can be formed from hydrolysis and condensation of tetraethoxysilane (TEOS). The related theories are built upon colloidal science, and the basic principles can be found in Available online at www.sciencedirect.com Thin Solid Films 516 (2008) 8399 – 8407 ⁎ Corresponding author. Tel.: +886 2 26215656x2614 or 2725; fax: +886 2 26209887. E-mail address: lpcheng@mail.tku.edu.tw (L.-P. Cheng). www.elsevier.com/locate/tsf 0040-6090/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2008.04.051