Characterization of deep UV photoresist properties by infrared near-field scanning optical microscopy and related methods [Elektronische Ressource] / vorgelegt von Jan Preußer
Characterization of deep UV photoresist propertiesby infrared near- eld scanning optical microscopyand related methodsD i s s e r t a t i o nzur Erlangung des Grades eines Doktorsder Naturwissenschaftenvorgelegt vonJan Preu eraus Otterndorfgenehmigt von derMathematisch-Naturwissenschaftlichen Fakult atder Technischen Universit at ClausthalTag der mundlic hen Prufung7. Juli 2003Vorsitzender der Prufungsk ommission..........................Prof. Dr. D. MayerHauptberichterstatter ........................................ Prof. Dr. W. SchadeBerichterstatter .................................................. Prof. Dr. D. KipDie vorliegende Arbeit wurde im Zeitraum vom November 1998 bis Juni 2003 am Institutfur Physik und Physikalische Technologien der Technischen Universit at Clausthal sowieam JILA, University of Colorado in Boulder, USA angefertigt.Contents1 Introduction 12 Fundamentals of lithography 52.1 Introduction to optical lithography in semiconductor device manufacturing 52.2 Chemically ampli ed photoresists . . . . . . . . . . . . . . . . . . . . . . . . 72.2.1 Nonlinear chemistry in latent image formation . . . . . . . . . . . . 72.2.2 Poly(t-butoxyoxycarbonylstyrene) (PTBOCST) . . . . . . . . . . . . 72.2.3 Poly(t-butylmethacrylate) (PTBMA) . . . . . . . . . . . . . . . . . . 102.3 Di usion in polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 Image formation in optical microscopy 153.
Die vorliegende Arbeit wurde im Zeitraum vom November 1998 bis Juni 2003 am Institut für Physik und Physikalische Technologien der Technischen Universität Clausthal sowie am JILA, University of Colorado in Boulder, USA angefertigt.
With advancing needs for higher packaging densities in chip technology, smaller and smaller feature sizes have to be realized in substrate materials used for microchip fabrication. It was proposed that the development in decreasing structure size follows an exponential behavior, also termed ”Moore’s Law” [1].
Today probably the most limiting factor is given by the photolithographic process, which is used to transfer an image of the designed structure onto the semiconductor. Polymeric photoresists are the key component in industry for patterning semiconductors, flat panel displays and data storage device components. An important step towards even smaller features was taken by Ito and coworkers [2, 3] by developing chemically amplified photoresists, which allow for an optical lithography process beyond Rayleigh’s resolution limit. While the smallest dimensions possible scaled directly with the wavelength of light used in the lithographic process, the new resists open a range of possibilities due to their nonlinear response to UV irradiation.
With the introduction of acidcatalyzed chemically amplified photoresist chemistry, a microscopic understanding of dynamics in the photopolymers is needed. Latent image metrology provides the means to study the evolution of resist profiles at different steps of the pattern formation: after exposure, postexposure bake and development. Image spreading and surface roughness are only two examples of parameters that have to be understood and controlled on a nanometer length scale.
While optical microscopy utilizes fluorescent tracers to track diffusion properties and feature broadening at a microscopic level, other work employs atomic force microscopy to perform topographic profiling and examine local shrinkage, which is related to the acidcatalyzed process. Fourier transform infrared spectroscopy (FTIR) is used to deliver macroscopic information on bulk samples but none of the techniques above allow to gain unperturbed insitu information on the dynamics in patterned photolithographic polymers.
Nearfield scanning optical microscopy (NSOM) offers the possibility to obtain images at lateral resolutions far beyond the diffraction limit impinged on conventional microscopy. This is achieved by illuminating the sample through a subwavelength aperture in