Dependence of resist profile on exposed area ratio

Shiobara, Eishi; Kawamura, Daisuke; Matsunaga, Kentaro; Onishi, Yasunobu

doi:10.1117/12.436896

Cited by 5 publications

(6 citation statements)

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“…This results in decreased amount of photoacid available for deprotection and chemical amplification reactions, which transform the exposed part of the lipophilic resist to a hydrophilic material that is easily washed away in aqueous developer. However, should such evaporated acids get condensed perhaps on the top-cover of the PEB oven and redeposit back as droplets on the resist feature as reported by Shiobara et al, 8 they should leave footprints like top surface erosions on an order greater than micrometer scale. Contrary to the "T-top" formation and surface webbing of patterned resist line features, 8 resist line features patterned with full-field ArF laser scanners and steppers typically have rounded and tapered top surface and do show significant resist erosion (see Section 3.4).…”

Section: Introductionmentioning

confidence: 85%

“…However, should such evaporated acids get condensed perhaps on the top-cover of the PEB oven and redeposit back as droplets on the resist feature as reported by Shiobara et al, 8 they should leave footprints like top surface erosions on an order greater than micrometer scale. Contrary to the "T-top" formation and surface webbing of patterned resist line features, 8 resist line features patterned with full-field ArF laser scanners and steppers typically have rounded and tapered top surface and do show significant resist erosion (see Section 3.4). In addition, the boiling points of typical photoacids used in commercially available ArF resists are greater than the PEB temperature, precisely to prevent photoacid evaporation.…”

Section: Introductionmentioning

confidence: 85%

“…10 While evaporation of photoacids with low boiling point is possible and has been reported in the literature, 11 the manifestation of its effect is typically "T-topping" and webbing of the top part of the resist feature. 8 T-top formation in this instance is due to photoacid loss by evaporation. This results in decreased amount of photoacid available for deprotection and chemical amplification reactions, which transform the exposed part of the lipophilic resist to a hydrophilic material that is easily washed away in aqueous developer.…”

Section: Introductionmentioning

confidence: 95%

“…A number of papers have been written on this subject, all attempting to explain the cause of the problem. [8][9][10] While some of these papers attribute the problem to acid evaporation from the resist during the post-exposure bake (PEB) step, 8 others attribute the cause of the problem to scattered light, 9 or even formation of acids from gaseous molecules, particularly oxygen and nitrogen in air. 10 While evaporation of photoacids with low boiling point is possible and has been reported in the literature, 11 the manifestation of its effect is typically "T-topping" and webbing of the top part of the resist feature.…”

Section: Introductionmentioning

confidence: 98%

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Impact of photo-induced species in O 2 -containing gases on lithographic patterning at 193-nm wavelength

et al. 2002

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In order to prevent contaminants and impurities from being deposited on the optical elements of the tool, ArF lithographic patterning of photoresists is currently done in the exposure chamber of a scanner or stepper that is purged with clean dry air. Unfortunately, the 6.4 eV (193 nm) ArF laser photons can dissociate molecular oxygen in air into atomic oxygen, 1,2,3 form ozone, 1 form singlet molecular oxygen and atomic oxygen from the photodissociation of ozone, 1-4 and mediate singlet molecular oxygen formation in polymers by energy transfer mechanisms from impurities or specially added sensitizers (S) (e.g. dyes). 5-7 Once formed, these species mediate photo-oxidative degradation processes of resist polymers, including cross-linking, chain scission, oxidation, and other secondary reactions by free radical mechanisms, resulting in resist feature erosion, poor resist feature profiles, particularly under bright field illumination in full field scanners and steppers. The occurrence of these photo-oxidative degradation processes has been experimentally verified in photoresist films exposed in commercially available ArF laser scanners and steppers that are purged with clean dry air. Using a custom-built ultra-high vacuum (UHV) chamber equipped with ArF laser beam line, mass spectrometer, and infra-red spectrometer, as well as an ex-situ Xray photo-electron spectrometer and a Fourier Transform infra-red (FTIR) spectrometer, the effects of different exposure environments (dry air, nitrogen, oxygen, ozone/oxygen mixture, and vacuum) in either contributing to or mitigating these photo-oxidative degradation processes during exposure of photoresist films were studied. The effects of these photo-oxidative degradation processes have been quantified, and it was observed that the processes are initiated at the surface of resist polymers by photo-induced species, and proceed inwards, giving rise to a gradient of deteriorated material across the specimen thickness.

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Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 98%

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Impact of photo-induced species in O 2 -containing gases on lithographic patterning at 193-nm wavelength

et al. 2002

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“…Figure 1 shows process flow with the over-coating process. (1) Forming over-coat layer onto resist film on wafers (2) First exposure of only line-and-space (L/S) array regions to wafers with mask A (3)…”

Section: Introductionmentioning

confidence: 99%

How to separate CD variation on local pattern density into error sources?

Kawano

Satõ

Hayasaki

et al. 2005

Optical Microlithography XVIII

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We propose a methodology that separates critical dimension (CD) variation depending on local pattern density into error sources; CD error on exposure mask, mid-range flare of exposure tool, and acid evaporation during post exposure baking (PEB). This methodology consists of two particular processes. One is over-coating process onto resist film before exposure, and the other is double exposure process using test reticles. The test reticles have line-and-space (L/S) array region and peripheral region that contains opaque area to avoid overlapping with L/S array region in double exposure process. Over-coating process allows separation of acid evaporation from other error sources. On the other hand, double exposure process enables elimination of CD error on exposure mask depending on local pattern density since double exposure process can make various pattern densities around fixed L/S mask pattern. In fact, the experimental CD results could provide the good agreement with estimated CD results using mid-range flare model. It has become clear that the influence of local pattern density increases with design rule shrinkage. Furthermore, the methodology revealed that the influence of each error source is greatly dependent on local pattern density. Consequently, the methodology is effective to separate CD variation on local pattern density into error sources.

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