Preparing an acrylic ester copolymer as an ultrathick negative photo resist

The characteristics of the acrylic ester copolymer as an ultrathick negative photo resist are investigated in this paper, which analyzed both thermal property and film performance. Several materials are involved in this experiment. Dimethyl-acryl-tricyclo[5,2,1,0^2,6]decame dimethyl ester (TA) of difunctional photo monomer is produced by esterifying tricyclo[5,2,1,0^2,6 ]decame dimethanol (TDMol) and methyl acrylate (MA). The acrylic ester resin base of the photo resist is obtained by copolymerizing methacrylic acid (MAA), benzyl methacrylate (BzMA) and 2-hydroxyl ethyl methacrylate (2-HEMA). A few designed formulas at different ratios are conducted by co-mixing 1-(4-methylthiophenyl-2-(N-morpholino) propan-1-one) (PI-777) of the photo initiator, 2-isopropylthioxanthone (ITX) of the photo sensitizer, TA, dipentaerythrithol hexaacrylate (DPHA) of the multifunctional photo monomer, and the acrylic ester resin base. Comparison with characteristics among formulas is also proposed. It is found that the thermal reliability of ultrathick negative photo resist is extremely excellent by I-line lithography process and scanning electronic microscopy (SEM) and thermal gravimetric analyzer (TGA) measurements.