Electron-beam resist self developing

In this article we will describe two different types of positive electron-beam resists, which were briefly reported in our previous communications (2,3). One is the homopolymer or copolymer with methyl methacrylate and a-substituted benzyl methacrylate, which forms methacrylic acid units in the polymer chain on exposure to an electron-beam and can be developed by using an alkaline solution developer. In this case, the structural change in the side group of the polymer effectively alters the solubility properties of the exposed polymer, and excellent contrast between the exposed and unexposed areas is obtained. The other is a self developing polyaldehyde resist, which is depolymerized into a volatile monomer upon electron-beam exposure. The sensitivity was extremely high without using any sensitizer. 

Aldehyde Copolymer Self Developing Electron-beam Resists. The ceiling temperature for the copolymerization of aliphatic aldehydes is usually below 0°C and the copolymers are easily depolymerized into monomeric aldehydes above 150°C under vacuum. This depolymerization into monomers also occurs on electron-beam or X-ray exposure as evidenced by combined gas-liquid partition chromatography-mass spectrometry. As a result, the copolymers of aldehydes behaved as self-developing positive resists and almost complete development was accomplished without any solvent treatment. Electron-beam exposure characteristics of the aliphatic aldehyde copolymers studied here are... 

Films of polyphthalaldehyde, sensitized by cationic photoinitiators, have been imaged at 2-5-mJ/cm in the deep ultraviolet (DUV) (see Section 3.10), at 1 pC/cm (20 kV) electron beam radiation and at an unspecified dose of Al-A x-ray radiation. The ultimate utility of this "self-developing" resist system will depend upon its efficacy as an etch barrier. It seems clear that such materials would not serve as adequate etch masks for... 

When resist films coated with formulations comprising this endcapped polymer with 10% by weight of various onium salts are exposed to DUV photons or an electron beam, acids are generated from the onium salts that go on to catalyze the hydrolytic scission process of the endcap moieties, as shown in Scheme 7.45, with the net result being the evaporation of the irradiated areas, with rather catastrophic implications for the contamination of the optical elements of exposure tools. In this mechanism, the acid attacks the lone electron pair on oxygen and brings about the depolymerization of the entire polymer. This, in essence, was the first resist system that self-developed reliably at room temperature without any further processing or special conditions. ... 

Patterning of hydrophilic/hydrophobic alkanethiols combining electron beam lithography (EBL) and self-assembly of alkanethiol molecules, (a) 150 nm thick polymethyl methacrylate (PMMA) resist spin coated onto the gold deposited on a silicon wafer (b) Patterned PMMA trenches were defined by electron beam and development (c) a hydrophilic ll-amino-l-un-decanethiol hydrochloride (MUAM) assembled in the PMMA trench area (d) PMMA resists were removed by acetone to produce patterned MUAM on gold (e) backfilled by hydrophobic octadecanethiol (ODT) yielding the final chemical pattern. (Reprinted with permission from Wiley.)... 

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