Refractive indices in thick photoresist films as a function of bake conditions and film exposure

Ficner, Stanley A.; Dammel, Ralph R.; Perez, Yvette M.; Gardiner, Allen B.; Willson, C. Grant

doi:10.1117/12.275885

Cited by 3 publications

(7 citation statements)

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“…50 This difference may reflect residual solvent in the films or unintended exposure of these regions, both of which will lower the film refractive index. 52 In exposed regions of the polymer, the measured refractive index is 1.600, reflecting the expected shift to lower refractive index following UV exposure. To further explore the imaging capabilities of SRM, thin films of Teflon AF were investigated.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

“…49−51 The final refractive index change in the exposed film depends on the degree of photoactivation and the amount of residual solvent remaining in the film following postexposure baking. 52 To create refractive index test samples, standard photolithography techniques were used to expose thin films of AZ 1518 to UV radiation through the mask shown in Figure 4A. Following exposure, the films were baked to remove residual solvent but not processed further, leaving smooth polymer films with refractive index features encoded by the mask.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Scanning Resonator Microscopy: Integrating Whispering Gallery Mode Sensing with Atomic Force Microscopy

Wildgen

Dunn

2015

ACS Photonics

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Scanning resonator microscopy (SRM) is developed to integrate whispering gallery mode (WGM) sensing with atomic force microscopy (AFM). The hybrid technique combines the exquisite refractive index sensing of whispering gallery mode resonators with the topography mapping capabilities of AFM. A 45 μm diameter barium titanate microsphere is attached to the end of a conventional AFM cantilever and acts as both a WGM resonator and stylus for mapping surface topography. Calibration plots, taken in contact-mode feedback, show that the WGM spectrum responds to changes in both solution and substrate refractive index. SRM imaging of a glass substrate reveals changes in surface refractive index that correspond to a small, 36 nm high feature measured simultaneously in the contact-mode topography image. Spectral measurements confirm that the contrast arises from refractive index changes and not coupling with sample topography, thus validating the approach. Additional measurements on thin polymer films and protein-coated surfaces are presented and discussed in terms of possible areas of application for SRM.

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Section: ■ Results and Discussionmentioning

confidence: 98%

Section: ■ Results and Discussionmentioning

confidence: 99%

Scanning Resonator Microscopy: Integrating Whispering Gallery Mode Sensing with Atomic Force Microscopy

Wildgen

Dunn

2015

ACS Photonics

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“…12 At higher PAB temperatures, nearly all the solvent is baked off, and the film is annealed, reducing the intrinsic void volume to (on the order of) 3%. 26 The CI lattice model predicts the roughness to increase from 0.21 to 0.36 nm over the range of void volume presented. This small increase in roughness is difficult to confirm experimentally.…”

Section: Modeling Resultsmentioning

confidence: 99%

“…8,9 There is also a dramatic change in the extent of surface inhibition. However, the HD experiments, 15 the model by Mack 16 and the results of Ficner 26 suggest that the change in surface inhibition is not related to a residual solvent concentration gradient in the film. Therefore the oxidation theory deserves close examination for the novolac resin studied in this work.…”

Section: Oxidation Effects During Pabmentioning

confidence: 98%

“…Ficner et al studied index of refraction gradients in AZ novolac resists with a Metricon Prism coupler. 26 They observed gradients in the index of refraction for thick films (32µm), indicating a significant residual solvent gradient. But with thinner films (4-8µm), the index gradient was "too small to lead to observable bent light modes", and any index gradient was not detectable, which is consistent with our results.…”

Section: Investigating Density and Pac Gradients By Halt Developmentmentioning

confidence: 99%

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Understanding nonlinear dissolution rates in photoresists

et al. 2001

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This work focuses on understanding the dissolution phenomenon of surface inhibition, which is observed often in the development of novolac based resists. Many theories have been offered to explain this phenomenon, including a concentration gradient of resist components, oxidation of the surface, formation of a gel layer, and surface roughness effects. This work focuses on theories that propose a concentration gradient in resist components. A technique has been established to separate and analyze individual layers of thin films, and the concentration gradient in many resist components (residual solvent, low molecular weight chains, photoactive compound, density) has been compared to the observed dissolution rate. The results indicate that no significant concentration gradients exist in a 1µm novolac film, and that these hypotheses are inadequate to explain surface inhibition. Several other theories are explored, including oxidation of the surface, surface roughness effects, etc. The critical ionization dissolution model may offer an explanation for why surface inhibition is observed in novolac, but typically not in poly(p-hydroxystyrene).

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Research on the optical field distribution and micro-fabrication model in convex-surface laser lithography

Chen

Liang

Wang

et al. 2010

Optics Communications

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Refractive indices in thick photoresist films as a function of bake conditions and film exposure

Cited by 3 publications

References 0 publications

Scanning Resonator Microscopy: Integrating Whispering Gallery Mode Sensing with Atomic Force Microscopy

Scanning Resonator Microscopy: Integrating Whispering Gallery Mode Sensing with Atomic Force Microscopy

Understanding nonlinear dissolution rates in photoresists

Research on the optical field distribution and micro-fabrication model in convex-surface laser lithography

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