Potential energy hypersurfaces of the nitrogen elimination and the Wolff rearrangement were investigated for both cyclic and open-chain 2-diazoketones by means of semi-empirical MINDO/3 molecular orbital calculations with configuration interaction. In the cases of 2-diazobenzen-l-one and cis-2-diazoethan-1-one, the nitrogen elimination takes place simultaneously with the Wolff rearrangement in a concerted fashion and neither ketocarbene nor oxirene is produced. The potential energy changes were shown in Fig. 2 and Fig. 9, respectively, and the molecular structure changes following the reactions were in Figs. 4 and 10. In contrast, 2-diazoethan-1-one in trans-conformation produces oxirene through nitrogen elimination in a concerted fashion. The oxirene isomerizes to ketene via the Wolff rearrangement, passing over a second saddle point of low energy (Fig, 5). The reaction sequence is shown in Fig. 8. No ketocarbene intermediate is produced in any case. A new mechanism of the Wolff rearrangement was proposed as in Fig. 14(b). This mechanism explains experiments well while the old mechanism (Fig. 14(a)) is inconsistent with experiments occasionally. It was concluded that the photochemical reaction of the diazonaphthoquinone-novolac resist mainly taking place in microlithography process is one-step ketene formation as shown in Fig. 1(c).

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Photochemical reactions of 1-oxo-2-diazo-1, 2-dihydrobenzene (DBQ), 1-oxo-2-diazo-1, 2-dihydronaphthalene (DNQ) and 5-(4-tolyl)sulfonated DNQ (DNQ-5STL) are studied, as typical examples of six-membered ring α-diazoketones, by reverse-phase liquid chromatography. The obtained products under different reaction conditions, such as photochemical reactions of pure solid DNQ-5STL in air and in vacuo, are examined. The reactivity of the carboxy compounds produced in air or in a water-containing solution is also discussed. They exhibit decarboxylation, dimerization or azo formation in the presence of bases, being markedly dependent on the type of molecules. The azo formation rate constant of the 3-carboxyindene analogue from DNQ-5STL is much greater than that of its dimerization. Photochemical reactions of six-membered ring α-diazoketones from excitation to final product formation are also discussed.

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For uv-hardening increase in oxygen concentration accelerates crosslinking rate than in air, and uv-exposure in nitrogen retards the reaction. Surfaces of photoresist images are photo-oxidized by intense uv-irradiation in air. However, the oxidized layer never extends over several hundred Å depth as measured by ESCA. Crosslinking extends far deeper, although it depends on the irradiating wavelength. The degree of crosslinkages is far densier near the surface than in the interior. A combination of heating and uv-exposure helps uv-hardening by spreading and acclerate crosslinking in resist images. Deep-uv light never reaches deeper beyond a few micron thick layer of photoresists and of polyamic acids. Thus, uv-hardening has a limit of its application. High aspect ratio images can be fabricated with photoimageable polyamic acid. However, in high temperature curing the images flow, yielding only low aspect ratio images of polyimides. Pulsed electron beam hardening can solve these problems of thick photoresists and of polyamic acids. For both type of images about 200 pulses of electron beams at 25keV are required, each pulse having a dose from 1μC/cm² to 10μC/cm² with a duration of about 100 nsec. Another method of resist image stabilization is chemical crosslinking, using various crosslinking agents. These image hardening processes are discussed in terms of advantages and disadvantages of the processes and chemical mechanisms involved.

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The REL(Resolution Enhanced Lithography) process is one of the most simple and effective ways to improve the photoresist resolution and pattern contrast.(1) This process consists of the conventional novolak positive photoresist process steps and the deep UV flood exposure step between the image exposure and the development. The solubility rate of the surface layer in alkaline developer is suppressed by the absorption of the deep UV light, and the top parts of the resist patterns don't become round.
The chemical formation reaction of the solubility rate suppressed layer is studied, using Differential Scanning Chromatography (DSC), Thermogravimetric analysis (TGA), Gel Permeation Chromatography (GPC), and Fourier Transform Infrared Spectroscopy (FT-IR). From the results of these analyses, it is concluded that the formation of the solubility rate suppressed layer is caused by the esterification reaction under the deep UV flood exposure between novolak resin and unphotoreacted PAC(Photo Active Conpound).
Furthermore the influence of the flood exposure ligth wavelength to the pattern profile is studied. The best wavelength must be chosen for the used resist thickness to form a good pattern profile.

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A single layer resist process called "LENOS" (Latitude Enhancement Novel Single Layer Lithography) is proposed. LENOS process needs only two steps in addition to a conventional single layer process, which are the soak step of a resist film into an alkaline solution after the prebake step and the bake step after the exposure step. These two steps accelerate the dissolution rate of the resist of the exposure area during development on the one hand, and form the insoluble layer to a developer at the resist surface of the unexposed area on the other. As the result, LENOS process enhances the difference in dissolution rate between the exposed area and the unexposed area. It is found that LENOS process shows from 1.3 to 3.0 times wider focus depth compared with the conventional single layer process and this focus depth is equal to that in the tri-layer resist process.

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The mechanism of resolution improvement in novolak-based positive photoresists was investigated from the stand-point of the image formation process. The image formation process in the novolak-quinonediazide system involves the dissolution inhibition in unexposed parts and the dissolution promotion in exposed parts. The γ(gamma)-value, which is one of the indexes of resolution capabilities, depends greatly on the difference between the solubility of unexposed parts and that of exposed parts, i.e.- the lower dissolution rate in unexposed parts(Ro) and the higher one in exposed parts (Rp) are desirable to obtain high γ-values.
Dissolution rates(Ro, Rp) were measured on the positive photoresists containing various kinds of cresol-formaldehyde type novolak resins, and the influence of factors of novolak resins-such as molecular weight, isomeric structure of cresols, methylene bond position-on the dissolution rates was investigated.
The results indicates that there are two methods to raise γ-values; (1) to increase the ratio of para-cresol to meta-cresol (2) to raise S₄ value (which represents the ratio of "unsubstituted" carbon-4 atoms in benzene rings of cresols)- in other words, to make the novolak resin "high-ortho bonding" structure. (The ortho positions of cresols are highly used for methylene bondings.) In the case of (1), however, there was a trade-off relationship between γ-values and resist sensitivity because of the solubility decrease of the novolak resin itself. On the other hand, the method (2) was found to make it possible to raise γ-values without the decrease in the resist sensitivity.
These novolak designs make it possible to obtain fine pattern fabrications with line and spaces down to 0.4μm.

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Fundamentals and mechanism of a direct image reversal process, which switches the tone of a resist from positive to negative without added bases are presented. A sulfonic acid generated photochemically from an aryl naphthoquinonediazidesulfonate catalyzes the crosslinking of exposed resist areas. Based on this principle a concept for a new naphthoquinonediazide with sufficient absorptivity at g-line and preserved acid generating capability was developed. The desired functionality of the PAC, prepared in a multistep synthesis, is proven. Guidelines for optimization of the most important process parameters are established for the newly formulated g-line image reversal resist. Lithographic results include 0.6μm equal lines and spaces with nearly vertical side walls using a 0.35 NA g-line stepper,

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This paper describes further work on XP-8843, a novel Advanced Negative Resist (ANR) system developed specifically for Kr-F excimer laser and broadband DUV advanced imaging systems. Optical changes in the resist film have been measured for exposed and post-exposure baked samples. At lithographically useful doses, 10mJ/cm², virtually no change in % transmittance occurs upon exposure. The post-exposure bake at 130°C leads to slight darkening (62 to 54%T). Resist modelling studies have shown that 10^-6 moles of acid per gram of resist are necessary to induce sufficient crosslinking to decrease resist dissolution rate in aqueous base by fifty-fold. Based on the concentration of acid, the average distance between nearest acid neighbors is 100Å in the exposed film. Contrast curves were generated on a 0.35 NA GCA ALS Laserstep^TM 200 5:1 stepper. Contrast was as high as 6 at 130°C post-exposure bake. Arrhenius plots of XP-8843 and the poly(p-vinyl)phenol-modelled resist vs. post-exposure bake temperature both gave E_a of 43kJ/mole. The XP-8843 resist exhibited high resolution (0.45 micron 1/s pairs) and vertical sidewalls when imaged at 1.35 micron thickness. The XP-8843 resist also shows high thermal resistance, maintaining linewidth at 210°C.

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