Effect of Glass Transition Temperature on Compression and Elastic Properties of Poly(Meth)Acrylate Copolymer Thin Films and their Photoresist Patterns

Abstract

In order to study the effect of glass transition temperature (T g ) on the compression and elastic recovery properties of polymer, several poly(meth)acrylate copolymers having three or four segment units composed of methacrylic acid (MAA) and other vinyl monomers such as glycidyl methacrylate (GMA), styrene (STY), butyl acrylate (BAM), 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), benzyl methacrylate (BzMA), 2-ethylhexyl acrylate (EHA), octadecyl acrylate (ODA), ethyl acrylate (EAM), and lauryl methacrylate(LMA) were synthesized. The synthesized copolymers showed different glass transition temperatures depending on the component type. Thin films and micro patterns were prepared by photolithography process (spin coating=pre-baking=UV-exposure=KOH developing=post-baking) with prepared copolymer solution. The compression and recovery property of copolymer films and micro patterns were determined by nano indenter. As a result, copolymers with lower T g especially MAA=GMA=STY, MAA=GMA=STY=BAM, and MAA=GMA=STY=HEMA copolymers showed higher compression and elastic recovery ratio.

Preparation and Properties of Four-component Copolymers Applied in Negative-type Photoresists

“…Consistent with this view, the development time for Run No.4 decreased to 5 min when the AV of the binder was increased to 131.2 mg KOH g À1 solid binder, and superior mechanical properties (elastic recovery: 81.1%, compression: 300 mN) were obtained for the pattern. The elastic recovery of poly(MAA-co-benzyl methacrylate) and poly(MAA-co-STY-cobenzyl methacrylate) were 62.8 and 72.0%, respectively, as obtained from literature [14]. Therefore, it appears that superior mechanical properties of the photo spacer can be obtained by introducing components such as PMI and IBMA with rigid characteristics, a cross-linker such as DPHA with a higher capacity for inter-penetration, and high concentrations of MAA into the photoresist.…”

“…The first two functional groups can improve the thermal and development properties of the photo spacer, and the third can provide sufficient acid value of the photoresist. The properties of acrylic copolymers, such as their photosensitivity [5], thermal stability [6][7][8][9][10][11][12], pattern resolution [9,13], glass transition temperature [14], nanosilica modified [8,[15][16][17], and physical characteristics [18], have been investigated in negative-type photoresists. The T g values of pure poly(methacrylic acid), polystyrene, poly(isobornyl methacrylate), and poly(phenylmaleimide-costyrene) were obtained from literature [19][20][21][22].…”