Cbr(contrast boosted resists) using halomethylaryl ketone as a base-labile water-repellent compound.

Abstract

In recent years, contrast enhanced resists using base-labile compounds, such as phenolphthalein [1,2,3] or acetoxybenzene [4] derivatives have been reported. All of these contrast enhanced resists have been positive resists. We previously reported a new contrast enhancement method [5] which can be applied to both negative and positive resists. The resists made using this method are called contrast boosted resists (CBRs) and they consist of a phenolic resin, a photoactive compound, and a base-labile water-repellent compound. The patterning process of a negative CBR is shown in Fig. 1. The CBR offers high resolution because the photochemically induced solubility difference between the exposed and unexposed regions is enhanced by the base-labile water-repellent compound. In the exposed region, the photochemically produced hydrophobic compounds and the added water-repellent compound work together to retard permeability of the base developer penetrating into the resist. Thus, the exposed region of the CBR is completely insolubilized in the base developer. On the other hand, the base developer permeates into the unexposed region of the CBR and converts the waterrepellent compound into hydrophilic compounds that do not inhibit dissolution in phenolic resin.Therefore, CBRs exhibit a large dissolution rate contrast compared to conventional resists.To find base-labile water-repellent compounds suitable for CBRs, the halomethylaryl ketones listed in Table 1 were evaluated as the base-labile water-repellent compounds. A halomethylaryl ketone was doped into a conventional negative resist composed of 4,4'-diazido-3,3'-dimethoxybiphenyl (DMDA) and m,p-cresol novolak resin (DMDA/novolak=1O/100; in weight ratio). The sensitivity curves of the resists consisting of DMDA, a halomethylaryl ketone, and an m,p-cresol novolak resin (DMDA/halomethylaryl ketone/ novolak=10/20/100: in weight ratio) are shown in Fig. 2. The resist doped with TBAB gave the highest resist contrast, and followed by BBAB and BAB.The contrast enhancement of the resist using TBAB can be explained as follows. When the resist is exposed to UV light (i-line: 365 nm), DMDA crosslinks the novolak resin. The crosslinked novolak resin and TBAB work together to retard the permeability of the base developer penetrating the resist in the exposed region. Then, the exposed region is completely