Highly Transparent Photosensitive Polybenzoxazole: Poly(o-hydroxy amide) Derived from 4,4′-(Hexafluoroisopropylidene)bis(o-aminophenol) and o-Substituted Dicarboxylic Acid Chlorides

Abstract

ABSTRACT:A novel poly(o-hydroxyamide) (PHA) as a precursor of photosensitive polybenzoxazole (PSPBO) that exhibits high transparency at 365 nm wavelength (i-line) has been developed. Time-dependent density functional theory (TD-DFT) calculations using the B3LYP hybrid functional were performed to predict the transparencies of various o-hydroxyamides in the i-line region. Based on these results, 2,2 0 -dimethyl-biphenyl-3,3 0 -dicarboxylic acid chloride was prepared and polymerized with 4,4 0 -(hexafluoroisopropylidene)bis(o-aminophenol). The resulting PHA-3 showed a high transparency (92%, 1:0 Â 10 À3 mol/L in N,N-dimethylacetamide (DMAc)), superior to that of the conventional PHA-1 (83% at the same concentration in DMAc) derived from 4, The thermal and dielectric characteristics of photosensitive polyimide (PSPI) are acceptable for a number of applications in the semiconductor industry, and a wide variety of PSPI has been developed and are made commercially available to meet requirements of different applications, such as inter-level insulation, stress buffer layer, and -ray shielding layers of semiconductor devices.1 PI, however, has numerous imide groups that increase water uptake and dielectric constant.2 Polybenzoxazole (PBO) is known as an super engineering thermoplastics, and its properties are comparable with PI. In addition, the absence of carbonyl group in PBO results in lower water uptake and dielectric constant.2 Thus, the photosensitive polybenzoxazole (PSPBO) is attracting great attention as substitute for conventional PSPI in recent years. 3-12The commercially available PSPBO is based on poly(o-hydroxy amide) (PHA), which is usually prepared by polycondensation of 4,4 0 -(hexafluoroisopropylidene)bis(o-aminophenol) (12) and 4,4 0 -oxybis-(benzoic acid) (8a) using a condensation agent, because of its high transparency at 365 nm wavelength (i-line). 13,14 There is an increasing demand for thicker films for small package to act as a buffer layer andray shielding applications, 15,16 consequently, it is quite important to develop a novel photosensitive polymer with higher transparency for UV lithography. The absorption of PI and PBO in i-line region corresponds to the excitation of electrons such as transitions involving p, s, and n electrons, charge-transfer (CT) electrons, and d and f electrons. Recently, we have demonstrated that the time-dependent density functional theory (TD-DFT) calculations using the B3LYP hybrid functional with the 6-311++G(d,p) basis set can well reproduce UV spectra in the measurements of model compounds without incorporation of empirical corrections.17 Utilizing this method, the absorption in i-line region of the above mentioned PHA was found to be the CT type transition between the benzoic acid and the o-hydroxyamide rings. Therefore, we designed and prepared a novel transparent PSPBO based on 4,4 0 -sulfonylbis(o-aminophenol) (13) and 4,4 0 -oxybis(benzoyl chloride) (8b) for i-line lithography.18 Introduction of a sulfone group as a substitute for hexafluoroisopropylidene...

An Alkaline-Developable, Negative-Working Photosensitive Polybenzoxazole Based on Poly(o-hydroxyamide), a Vinyl Sulfone-Type Cross-Linker, and a Novel Photobase Generator

“…Generally, PSPBOs are based on PHA with 20−30 wt % o -diazonaphthoquinones (DNQs), which are converted into alkaline-developable indene carboxylic acid as dissolution promoters after irradiation to give a positive pattern. However, a PSPBO resist system using DNQ requires high exposure doses in the range of 200−400 mJ/cm 2 to obtain a clear patterned film. − To improve the photosensitivity, chemical amplification by photoacid generators (PAGs), which generates sulfonic acid derivatives as catalysts, was employed by using cross-linkers or dissolution inhibitors. ,− On the other hand, the Cu circuits and bonding wires in recent high-speed-processing microchip devices have become narrower and narrower. Hence, there is concern that the acid derivatives from PAGs − and DNQs will induce the corrosion of Cu circuits and wires in next generation microchips.…”

“…[5][6][7][8][9] To improve the photosensitivity, chemical amplification by photoacid generators (PAGs), which generates sulfonic acid derivatives as catalysts, was employed by using cross-linkers or dissolution inhibitors. 4,[10][11][12][13] On the other hand, the Cu circuits and bonding wires in recent highspeed-processing microchip devices have become narrower and narrower. Hence, there is concern that the acid derivatives from PAGs [14][15][16][17] and DNQs will induce the corrosion of Cu circuits and wires in next generation microchips.…”