Printing methods are becoming important in the fabrication of flexible electronics. A transfer printing method
has been developed for the fabrication of organic thin-film transistors (OTFT), capacitors, resistors and inductors onto
plastic substrates. The method relies primarily on differential adhesion for the transfer of a printable layer from a
transfer substrate to a device substrate. A range of materials applications is illustrated, including metals, organic
semiconductors, organic dielectrics, nanotube and nanowire mats, a patterned inorganic semiconductor and graphene.
Transfer printing can be used to create complex structures including many disparate materials sequentially printed onto
the flexible substrate, with no mixed processing steps performed on the device substrate. Specifically, the fabrication
and performance of model OTFT devices consisting of a polyethylene terephthalate (PET) substrate, gold (Au) gate and
source/drain electrodes, a poly(methyl methacrylate) (PMMA) dielectric layer and either a pentacene (Pn) or a poly(3-
hexylthiophene) (P3HT) organic semiconductor layer will be presented. These transfer printed OTFTs on plastic outperform
non-printed devices on a Si substrate with a SiO2 dielectric layer (SiO2/Si). Transfer printed Pn OTFTs on a
plastic substrate have exhibited mobilities of 0.237 cm2/Vs, compared to non-printed Pn OTFTs on a SiO2/Si substrate
with mobilities of 0.1 cm2/Vs. Transfer printed P3HT TFTs on a plastic substrate have exhibited mobilites of 0.04
cm2/Vs, compared to non-printed P3HT TFTs on a SiO2/Si substrate with mobilities of 0.007 cm2/Vs.
Atomic force microscopes (AFMs) are used in the semiconductor industry for a variety of metrology purposes. Step height measurements at the nanometer level and roughness measurements at sub-nanometer levels are often of interest. To perform accurate measurements, the scales of an AFM must be calibrated. We have been exploring the use of silicon single atomic steps as height standards for AFMs in the sub-nanometer regime. We have also designed and developed the calibrated AFM (C-AFM) to calibrate standards for other AFMs. Previously, we measured the step height of silicon single atomic steps on Si (111) (with native oxide) using the C-AFM. The value we obtained was 304 +/- 8 pm (k=2). From three independent measurement techniques, including our C-AFM result, we estimate an accepted value for the silicon step height of 312 pm +/- 12 pm (k=2), which corresponds to an expanded uncertainty of about 4 %. We have also completed a NIST led comparison of AFM measurements of silicon step samples to further evaluate their suitability as standards in industrial applications. If the reproducibility of the participants' measurements is sufficient, the accepted value could be used to calibrate the scale of the measuring tools in this sub-nanometer regime. The participants sent the data to NIST for analysis. This was done so that all of the data would be analyzed in a uniform manner. The results of our analysis indicate that these samples can be used effectively as standards. The average standard deviation of all of the participants results was 6 pm. Hence, it should be possible to use these specimens as sub-nanometer z-axis calibration standards with an expanded uncertainty of about 6 %.
KEYWORDS: Calibration, Metrology, Atomic force microscopy, Surface roughness, Interferometers, Atomic force microscope, Standards development, Polarization, Capacitance, Digital signal processing
NIST personnel (J.S. and T.M.) visited 23 IC manufacturing companies and equipment suppliers during 1994 to determine semiconductor industry needs for scanned probe metrology. NIST has initiated projects addressing some of the need identified. When complete these projects will enable improved metrology using the scanned probe microscope. Industry needs include pitch, height, angle, and width calibration artifacts, and understanding of the effect of humidity on AFM measurements, and tip metrology techniques. To meet these needs we have designed and built a Calibrated Atomic Force Microscope (C-AFM) with interferometric position control. This AFM is capable of making accurate measurements. We present the operational characteristics of the instrument, accurate X, Y, and Z pitch measurements on a commercially available artifact, measurements on a prototype surface roughness artifact, and a promising technique by which to make accurate linewidth measurements.
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