Chemical mapping of patterned polymer photoresists by near-field infrared microscopy

Dragnea, Bogdan; Preusser, Jan; Szarko, Jodi M.; McDonough, Laurie; Leone, Stephen R.; Hinsberg, William D.

doi:10.1016/s0169-4332(01)00068-x

Cited by 15 publications

(27 citation statements)

References 14 publications

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“…While the use of a free electron laser source limits applications to the relatively few researchers who can access such a device, in principle the general technique could be applied to alternative tunable IR laser sources. Recently interesting IR-SNOM measurements have been done using a color center laser pumped by a Kr + laser [18,19]. We use the shear force feedback mechanism to control the tip-to-surface distance.…”

Section: Methodsmentioning

confidence: 99%

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Vobornik

Margaritondo

Sanghera

et al. 2005

Journal of Alloys and Compounds

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Scanning near-field optical microscopy (SNOM or NSOM) is the technique with the highest lateral optical resolution available today, while infrared (IR) spectroscopy has a high chemical specificity. Combining SNOM with a tunable IR source produces a unique tool, IR-SNOM, capable of imaging distributions of chemical species with a 100 nm spatial resolution. We present in this paper boron nitride (BN) thin film images, where IR-SNOM shows the distribution of hexagonal and cubic phases within the sample. Exciting potential applications in biophysics and medical sciences are illustrated with SNOM images of the distribution of different chemical species within cells. We present in this article images with resolutions of the order of λ/60 with SNOM working with infrared light. With our SNOM setup, we routinely get optical resolutions between 50 and 150 nm, regardless of the wavelength of the light used to illuminate the sample.

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Section: Methodsmentioning

confidence: 99%

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Vobornik

Margaritondo

Sanghera

et al. 2005

Journal of Alloys and Compounds

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“…Similar effects were also observed in chemical imaging of similar photoresists by optical techniques such as CARS microscopy 15 and IR NSOM. 10,11 In imaging by IR NSOM, the narrowing of the valleys ͑the exposed regions of the polymer͒ was in part attributed to the limited reach of the probing IR light at the edges of the deep regions due to the conical shape of the tip. 10,11 However, this is not the case in the present experiment which does not employ a tip.…”

Section: Resultsmentioning

confidence: 99%

“…This has also been observed before in samples patterned by exposure through a mask and has been attributed to interference of light leaking under the mask into the unexposed regions. 10 Chemical changes between the exposed regions of the patterned photoresist and the nonexposed regions include loss of a carbonyl group and the formation of a phenolic OH group. In addition, the fluorine containing photoacid generator may decompose or diffuse, creating a spatial distribution of the photoacid generator.…”

Section: Resultsmentioning

confidence: 99%

“…7,8 Chemical contrast images ͑due to selective absorption͒ have been obtained with a spatial resolution of 300 nm at 3 m ͑the OH stretching vibration͒ along with a simultaneous topographical image by using infrared near field scanning optical microscopy ͑IR NSOM͒. [9][10][11][12] Considerably higher spatial resolution is expected to be achieved by apertureless near field scanning optical microscopy when used with infrared absorption contrast. 13,14 However, this method also faces significant challenges in detecting the small signal ͑light scattered from a͒ Present address: Ecole Normale Supérieure, 75005 Paris, France.…”

Section: Introductionmentioning

confidence: 99%

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Chemical mapping of polymer photoresists by scanning transmission x-ray microscopy

Muntean

Planques

Kilcoyne

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Scanning transmission x-ray microscopy (STXM) is shown to be a powerful imaging technique that provides chemical selectivity and high spatial resolution (∼35nm) for studying chemically amplified photoresists. Samples of poly(4-t-butoxycarbonyloxystyrene) PTBOCST resist, imprinted by deep ultraviolet lithography with a line∕space pattern of 1.10μm∕0.87μm followed by a post-exposure bake, are used to demonstrate STXM imaging capabilities to extract photoresist latent images. Chemical contrast is obtained by measuring the x-ray absorption at an energy of 290.5 eV, corresponding to a carbon K shell electronic transition to the unoccupied π* molecular orbital of the PTBOCST carbonyl group. A quantitative analysis provides the spatial distribution of the fraction of the unexposed and deprotected polymers remaining after the post-exposure bake stage as well as the thickness of both regions. Both chemical and topographical contributions to the total contrast are estimated. Advantages and limitations of STXM in comparison with other imaging techniques with chemical specificity are discussed.

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“…The frequency dependence of the recorded near-field contrast for PMMA is also in a good agreement with the theoretically predicted scattering amplitude, 34 and with the results of previous studies on bulk co-block polymer films. 20,21,23 Further experiments were performed with 32 nm thick Y-shaped PS-PMMA mixed polymer brushes after exposure to two selective solvents: acetone (selective for PMMA) and toluene (selective for PS). When using only nanomechanical information, as obtained by AFM, it is challenging to locally distinguish the two polymer components.…”

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confidence: 99%

Local chemical composition of nanophase-separated polymer brushes

Filimon

Kopf

Schmidt

et al. 2011

Phys. Chem. Chem. Phys.

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Using scattering scanning nearfield infrared microscopy (s-SNIM), we have imaged the nanoscale phase separation of mixed polystyrene-poly(methyl methacrylate) (PS-PMMA) brushes and investigated changes in the top layer as a function of solvent exposure. We deduce that the top-layer of the mixed brushes is composed primarily of PMMA after exposure to acetone, while after exposure to toluene this changes to PS. Access to simultaneously measured topographic and chemical information allows direct correlation of the chemical morphology of the sample with topographic information. Our results demonstrate the potential of s-SNIM for chemical mapping based on distinct infrared absorption properties of polymers with a high spatial resolution of 80 nm Â 80 nm.

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Chemical mapping of patterned polymer photoresists by near-field infrared microscopy

Cited by 15 publications

References 14 publications

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Chemical mapping of polymer photoresists by scanning transmission x-ray microscopy

Local chemical composition of nanophase-separated polymer brushes

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