Leo Schlegel

Determination of acid diffusion in chemical amplification positive deep ultraviolet resists

A new method was developed to study the diffusion of photogenerated acid in chemical amplification resist systems which allowed an estimation of the diffusion range by simple means. The acid mobility was investigated for two different resist systems under various process conditions. It was found that solvent traces in the film cause a very strong increase of the acid mobility. In order to control the diffusion range, the post‐exposure‐bake temperature must be below the glass transition temperature. For one resist system, the increase in resist sensitivity with increasing baking temperature was much smaller than the corresponding increase in diffusion range. The results corresponded well with those obtained by lithography with the same resist.

Determination of Acid Diffusion in Chemical Amplification Positive Deep-UV Resists

The diffusion of photogenerated acid in chemical amplification resist systems was examined by a newly developed method which allowed an estimation of the diffusion range by simple means. The acid mobility was investigated for various process conditions. It was found that prebake and post-exposure-bake conditions have strong influence on the mobility of acid. The diffusion range of acid is much larger than values estimated from the catalytic volume. Large differences in diffusion characteristics were found for two different resist systems. The diffusion of various sulfonic acids decreased strongly with increasing molecule size.

Highly sensitive positive deep UV resist utilizing a sulfonate acid generator and a tetrahydropyranyl inhibitor

Abstract A new positive deep UV resist composed of the sulfonic acid ester MeSB as the acid generator and a tetrahydropyranyl inhibitor in a novolak matrix resin was investigated. The resist is very sensitive (D

Chemical amplification positive deep-UV resist using partially tetrahydropyranyl-protected polyvinylphenol

Chemical amplification positive resists using tetrahydropyranyl-protected polyvinylphenol (THP-M) were investigated for deep UV lithography. Infrared spectroscopy measurements showed that THP-M in the resist film cannot be completely deprotected by photo-generated acid. This causes a poor developability of the resist containing highly tetrahydropyranyl (THP)-protected polyvinylphenol in an aqueous base developer. In order to improve the developability in the pure aqueous base developer, we utilized partially THP-protected polyvinylphenol. To determine the optimum protection degree, we examined the relation between the dissolution rate of THP-M films and THP-protection degree in developers. A resist formulated from 20% THP-protected polyvinylphenol and bis(tert-butylphenyl)iodonium triflate resolved 0.30 micrometers line-and-space patterns with the aqueous base development using a KrF excimer laser stepper with a dose of 46 mJ/cm2.

Dissolution Behavior of Novolak/Dissolution Inhibitor Resist Systems in an Aqueous Base Developer

In order to understand the basic mechanisms working in the dissolution of novolak/dissolution inhibitor systems model compounds have been studied in terms of their dissolution inhibition capabilities. The influences of the structure of small size molecules on the inhibition effect were examined as well as the effects of the intramolecular composition and of the molecular weight of polymeric dissolution inhibitors. The role of the novolak type in the inhibition mechanism was also investigated. It was found that an amphiphilic character of the inhibitor molecule and an appropriate structure of the novolak matrix polymer are the most important features for systems with high dissolution inhibition capability. The intramolecular composition of polymeric dissolution inhibitors also has a strong effect, whereas the molecular weight of polymeric dissolution inhibitors has less influence.

Polyvinylphenols protected with tetrahydropyranyl group in chemical amplification positive deep-UV resist systems

Tetrahydropyranyl(THP) protected poly(p-vinylphenol)s were synthesized and their acid-catalyzed thermal deprotection has been utilized in the design of alkali developable, positive deep UV resist systems incorporating chemical amplification. Solubility of poly(p- tetrahydropyranyloxystyrene)(THP-M) films mixed with appropriate photoacid-generator (PAG) in alkaline developers increases upon exposure to deep UV radiation and subsequent heating. In a three component application where THP-M and PAG are mixed with a novolak resin, THP-M acts as an acid-labile dissolution inhibitor. Its dissolution inhibition ability was higher than that of a conventional photo-active dissolution inhibitor, diazonaphthoquinone. It is found that simple sulfonic esters such as 1,2,3-tri(methane sulfonyloxy) benzene (MeSB) are superior to onium salts in the three component approach because no negative tone side effect occurs when these esters are used as PAG. Fine patterns of 0.35 micrometers lines and spaces are obtained using KrF excimer laser steppers for the 3-component resists.

Chemical amplification positive deep ultraviolet resist by means of partially tetrahydropyranyl-protected polyvinylphenol

The design requirements of successive generations of VLSI circuits have led to a reduction in the lithographic critical dimensions. Among the several competing strategies utilizing shorter wavelength, deep-UV lithography is one candidate for hightly dense semiconductor device fabrication. Recently, much attention has been focused on chemically amplified resist systems for deep-UV lithography originally reported by Frechet, Ito and Willson. We showed in a previous article that polyvinylphenol protected with a tetrahydropyranyl-group(THP-M) is deprotected by photogenerated acid from an onium salt. The problem of this resist system is the difficulty in obtaining fine patterns with a pure aqueous base development. It is necessary to add some n-propanol to the aqueous base developer. In another paper, we described an aqueous-base-developable three-component system that uses THP-M as an inhibitor in combination with a sulfonic acid ester as an acid generator in a novolak matrix. A drawback of this resist is its low transmittance at 248 nm due to the high absorbance of the novolak. In this paper, we describe a two-component system composed of a partially tetrahydropyranyl (THP) protected polyvinylphenol to improve the transmittance at 248 nm as well as the developability in aqueous base. We also discuss its postexposure effect.