Takao Iwayanagi

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.

Peroxypolytungstic acids: A new inorganic resist material

Recently reported amorphous polytungstic acids containing peroxo groups are found to provide a new inorganic resist. A homogeneous resist film can be formed easily with the spin coating method. This film is made insoluble in water by deep ultraviolet, x ray, and electron beam irradiation. The oxygen reactive ion etching (O2 RIE) durability is found to be high enough that a bilayer resist scheme employing this resist as a top imaging layer gives a high resolution pattern (line and space: 0.38 μm). The mechanism for the radiation induced reaction is also discussed.

Tetrahydropyranyl protected polyhydroxy-styrene for a chemically amplified deep u.v. resist

Abstract Tetrahydropyranyl (TH) protected poly(p-hydroxystyrene) (PHS) was synthesized and its acid-catalysed thermal deprotection utilized in the design of an alkali developable, positive photoresist system incorporating chemical amplification. The solubility of THP-PHS films mixed with the appropriate onium salt photo acid generators in alkaline developers increases upon exposure to deep u.v. radiation and subsequent heating. A resist composed of THP-PHS and bis(tert-butylphenyl)iodonium triflate resolves 0.35 μm line-and-space patterns using a KrF excimer laser (248 nm) stepper (20 mJ cm−2).

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

Azide–novolak resin negative photoresist for i‐line phase‐shifting lithography

A negative photoresist consisting of 4,4’‐diazido‐3,3’‐dimethoxybiphenyl and a novolak resin, called micro resist for i‐line (MRI), has been prepared and evaluated for i‐line phase‐shifting lithography. MRI has a high transmittance (80%/μm) and a high resist contrast (γ) at i line (365 nm). Line‐and‐space patterns of 0.30 μm were achieved using MRI in conjunction with an i‐line phase‐shifting lithography. The insolubilization mechanism of MRI is attributed to a secondary amine formed by the reaction of nitrene with novolak resin.

Dissolution Inhibition of Phenolic Resins by Diazonaphthoquinone: Effect of Polymer Structure

In order to understand the basic mechanisms working in the dissolution of phenolic resin/diazonaphthoquinone (DNQ) positive photoresists, several polyhydroxystyrene derivatives have been studied in terms of their dissolution capabilities. The influence of the structure and the molecular weight distributions of phenolic resins on the inhibition effect were examined. In phenolic resins which have alkyl groups ortho to the hydroxy group a strong dissolution inhibition effect is found. As for the molecular weight distribution, the mixtures of a higher-molecular-weight polymer with lower dissolution rate and a lower-molecular-weight polymer with higher dissolution rate give strong dissolution inhibition by DNQ.

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.

Optimization of the composition of a new MRS-type negative resist

Sensitizer concentration is optimized for a new negative photoresist, MRL (Micro Resist for Longer wavelengths) with the assistance of computer simulation. The resist, which has photosensitivity in the ordinary UV region, resembles a deep UV resist MRS in terms of light absorption characteristic. It is found that a photosensitizer concentration of 20 wt% (based on the resin) is suitable for a reduction projection exposure system that utilizes UV light at 365 nm. A steep profile resist image of 0.7-µm lines and 0.7-µm spaces in a 1.0-µm thick resist layer is obtained using the MRL of optimized composition and the exposure system.

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.