Acid and base diffusion in chemically amplified DUV resists

Itani, Toshiro; Yoshino, Hiroshi; Hashimoto, Shuichi; Yamana, Mitsuharu; Samoto, Norihiko; Kasama, Kunihiko

doi:10.1016/s0167-9317(96)00176-1

Cited by 12 publications

(18 citation statements)

References 9 publications

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“…The performance of T-top free resist patterns of organic-base added DUV resists were also consistent with the work of Kawai et al 1 The above results indicated that the space width was not caused by the acid diffusion, because additional base component (NMP) not only quenched photogenerated acid, but also suppressed acid diffusion reaction within resist film. 8 For a positive DUV resist, a radiation sensitive acid generator is decomposed during exposure, and the subsequent acid-catalyzed thermal reaction at elevated temperature makes the resist soluble. It is assumed herein that the added organic base neutralized some of the photogenerated acid and the depletion of acid reduced the space width.…”

Section: Resultsmentioning

confidence: 99%

“…During postexposure delay, some of the added base will "trap" the acid and become deactivated, while the organic base, which is left, will remain activated because of the limited acid diffusion length. 8 As Fig. 8 presents, the reduction of the latent acid image becomes more significant as the pattern size shrinks.…”

Section: Effect Of Energy On Space Width Variation-mentioning

confidence: 93%

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Postexposure Delay Effect on Linewidth Variation in Base Added Chemically Amplified Resist

Shieh

Chiou

et al. 2000

J. Electrochem. Soc.

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Chemically amplified resist based on acid catalysis for deep UV lithography is a promising technology for patterns of 0.18 m or less. To improve the process stability and resist performance, extensive efforts have been made to understand how each component in resist formation influences lithographic performance. 1-13 Previously, the main problems for deep ultraviolet (DUV) resists were airborne contamination and linewidth change with different delay times. For the positive DUV resist, the generation of "T-top" at the resist-air interface is attributed to neutralization of the photogenerated acid by airborne organic bases, such as ammonia, during postexposure delay (PED). Employing a carbon filtration system, overcoat films and pretreating the substrate, can minimize the effects of contamination. 1-5 Linewidth variation is mainly induced by the effect of acid diffusion during exposure and baking. Therefore, the diffusion behavior of photogenerated acid has been widely investigated for both high and low activation energy (Ea) resist systems. 7-20 Adding base additives has been reported to reduce linewidth slimming of low Ea system such as acetal-based resists owing to reducing acid diffusion. 7,21 To stabilize the latent acid image of high Ea resist systems such as tertbutoxycarbonyl (t-BOC) containing resins, an additional base component was added not only to quench photogenerated acid, but also to suppress the acid diffusion reaction within the resist film. 8 Theoretical studies have also indicated that limited diffusion is essential for achieving high resolution chemically amplified DUV resists. 26,27 While inherent resist characteristics such as acid diffusion behavior, the effect of base components, and phenomenon of linewidth variation have been widely studied, presently no relationship has been established for these three components. This work evaluated the influence of organic base additive on acid concentration and lithographic performance in t-BOC-protected type chemically amplified positive DUV resist. A resist system comprising of a chemically amplified positive resist and an organic base, such as N-methyl pyrrolidone (NMP), not only prevents a T-top formation, but also suppresses acid diffusion reaction within resist film. 1 Based on the mechanism of neutralization of organic base and photogenerated acid, a model is established herein to describe the behavior of linewidth variation. Furthermore, a very useful equation has also been derived based on the diminution of photogenerated acid in resist film. This equation can accurately predict linewidth variation based on the delay time for various pattern sizes.The concentration of photogenerated acid is defined by the aerial image of the resist by a power equal to the reaction order of the acid. Therefore, the effect of exposure energy was investigated to clarify the behavior of linewidth variation during postexposure delay. The simulation result, calculated from the lithographic modeling tool PROLITH/2, has been used to evaluate exposure energy dependence...

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Energy On Space Width Variation-mentioning

confidence: 93%

Postexposure Delay Effect on Linewidth Variation in Base Added Chemically Amplified Resist

Shieh

Chiou

et al. 2000

J. Electrochem. Soc.

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“…In this study, a material system of CA photoresist has been designed to have patternable and mesoporosity formable through the combination of photo exposure and thermal treatment. These chemically amplified photosensitive polymers are typically combined with a cationic PAG,35, 36 such as a polymer that contains a t ‐BOC group with an iodonium salt. Such advanced design of photoresist systems based on CA has attracted much interest because it is highly sensitive to deep UV applications 37, 38.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced mesoporosity of Tert‐butoxycarbonyl acrylic photosensitive material with low dielectric constant

Lin

Chan

Lee

2012

J of Applied Polymer Sci

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We have developed a photosensitive system having low dielectric constant with mesoporous. The photosensitive system we developed is patternable and the mesoporosity is generated through the combination of photo exposure and thermal treatment. The mesopores were formed in a photosensitive material to reduce its dielectric constant. Tert-butoxycarbonyl (t-BOC) containing acrylic copolymer was activated as a photosensitive material via photochemical reactions. Iodonium salt as a photo acid generator was exposed to ultraviolet light with a wavelength of under 365 nm to form the corresponding Lewis acid. The side chains of t-BOC were cleaved by this Lewis acid to yield isobutylene and acrylic acid groups. The small molecules thus formed were further heated in the polymer matrix to generate mesopores. Notably, the t-BOC content and heat affect the dimensions and number of mesopores. The dielectric constant decreased as the density of mesopores increases. The formation of mesopores was observed by transmission electron microscope and scanning electron microscopy. We have also studied the mechanisms of formation of mesopores and their effects on the dielectric constant.

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“…As was shown previously acid diffusion is strongly influenced by resist materials and process conditions. [6][7][8][9] The material factors include the size and volatility of the photoacid, the glass transition temperature of the polymer binder, and the residual solvent. The process factors comprise the exposure, the pre bake (PB), and the PEB conditions.…”

Section: Introductionmentioning

confidence: 99%

Novel Diffusion Analysis in Advanced Chemically Amplified DUV Resists Using Photometric Methods.

Richter

Hien

Sebald

1999

J. Photopol. Sci. Technol.

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The demand for smaller device dimensions in microlithography drives the need to understand and control diffusion during photoresist processing. In advanced chemically amplified systems the lithographic performance is strongly influenced by diffusion of acid and base additives. Photoacid generation efficiencies and diffusion parameters were quantitatively evaluated using an established in situ photometric method employing a pH-sensitive organic dye. [ 1-3 ] A kinetic model for the post-exposure bake (PEB) has been proposed, transferred to molecular reaction dynamics and extanded to transport properties. The experimental data for this model have been obtained from UV/VIS spectroscopy measurements. The UV/VIS data show that a photoacid loss reaction during post-exposure bake has to be taken into account. Rough estimations of the acid diffusion lengths are given by the rate of the diffusion-controlled neutralization reaction for blanket exposures. The acid diffusion range was minimized, as the temperature of pre baking was raised and the PEB temperature was reduced. Chemical kinetics around the glass transition temperature of the resist are discussed. Furthermore, a face-to-face contact experiment (wafer-sandwich) involving the dye was used to determine acid loss during PEB. Comprehensively, the acid diffusion within the matrix and acid evaporation out of the matrix could be quantified. Results are used to improve the lithographic performance of the dual-wavelength CARL® [4,5] resist system presently used at Infineon Technologies.

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Acid and base diffusion in chemically amplified DUV resists

Cited by 12 publications

References 9 publications

Postexposure Delay Effect on Linewidth Variation in Base Added Chemically Amplified Resist

Postexposure Delay Effect on Linewidth Variation in Base Added Chemically Amplified Resist

Photoinduced mesoporosity of Tert‐butoxycarbonyl acrylic photosensitive material with low dielectric constant

Novel Diffusion Analysis in Advanced Chemically Amplified DUV Resists Using Photometric Methods.

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