In the mask shop the challenges associated with today’s advanced technology nodes, both
technical and economic, are becoming increasingly difficult. The constant drive to continue
shrinking features means more masks per device, smaller manufacturing tolerances and more
complexity along the manufacturing line with respect to the number of manufacturing steps
required. Furthermore, the extremely competitive nature of the industry makes it critical for
mask shops to optimize asset utilization and processes in order to maximize their competitive
advantage and, in the end, profitability.
Full maximization of profitability in such a complex and technologically sophisticated
environment simply cannot be achieved without the use of smart automation. Smart
automation allows productivity to be maximized through better asset utilization and process
optimization. Reliability is improved through the minimization of manual interactions
leading to fewer human error contributions and a more efficient manufacturing line. In
addition to these improvements in productivity and reliability, extra value can be added
through the collection and cross-verification of data from multiple sources which provides
more information about our products and processes.
When it comes to handling mask defects, for instance, the process consists largely of time
consuming manual interactions that are error prone and often require quick decisions from
operators and engineers who are under pressure. The handling of defects itself is a multiple
step process consisting of several iterations of inspection, disposition, repair, review and
cleaning steps. Smaller manufacturing tolerances and features with higher complexity
contribute to a higher number of defects which must be handled as well as a higher level of
complexity.
In this paper the recent efforts undertaken by ZEISS to provide solutions which address these
challenges, particularly those associated with defectivity, will be presented. From automation
of aerial image analysis to the use of data driven decision making to predict and propose the
optimized back end of line process flow, productivity and reliability improvements are
targeted by smart automation. Additionally the generation of the ideal aerial image from the
design and several repair enhancement features offer additional capabilities to improve the
efficiency and yield associated with defect handling.
Whispering gallery modes (WGM) in fluorescent dielectric microcavities have recently become an attractive alternative
to state-of-the-art label-free optical biosensors due to their high sensitivity to molecular adsorption and their ease of
operation under a variety of environmental conditions. In particular the true microscopic dimension of the sensor as well
as its purely radiative control without any need for external coupling opens new opportunities for label-free biosensing
on microscopic scale.
While these are obvious advantages, a direct comparison of the performance of WGM biosensors with well-established
techniques of known high sensitivity, such as surface plasmon resonance sensors, has not been undertaken to date, thus
obscuring the opportunities of the newly rising approach.
We have therefore studied the performance of both WGM biosensors and a commercial SPR sensor using a selection of
specifically and non-specifically binding biomolecules in-situ and under same conditions. The WGM biosensors consist
of 10 μm dye-doped polystyrene beads immobilized in a flow cell. The performance of the two techniques is compared
in view of the efficiency and sensitivity towards detection of both model interaction pairs (e.g. biotin/Streptavidin) and
specific interaction pairs such as antigen-antibody with a lower degree of interaction affinities.
We present some recent results of our work on cavity mode excitations in metal-coated microspheres, which aims at the
development of a novel type of bio-chemical sensor. In contrast to the well-known whispering gallery modes (WGM) of
dielectric particles, metal-coated dielectric microspheres also allow for excitation of modes in radial direction, the so-called
Fabry-Perot modes (FPM). One hurdle of such excitation is the proper adjustment of the reflectivity of the
metallic coating, which either causes a low quality factor of the modes in case of insufficient thickness, or, otherwise,
shields the inner cavity from outside excitation. The talk will present a novel concept on how such intricacies may be
overcome by proper selection of excitation wavelength and materials choice, and will demonstrate that FPM modes may
be excited in metal-coated microspheres with diameters down to 1 μm. First examples of utilization of such cavity modes
for bio-chemical sensing will be given. Besides sensing, potential applications of metallic microcavities are related to the
development of optical point sources, microscopic lasers, and to nonlinear nano-photonics.
We present a novel concept for an optical biosensor based on Whispering Gallery Mode (WGM) excitations in clusters
of spherical microresonators. WGM are specific optical modes that arise when light is trapped by Total Internal
Reflection (TIR) inside of a sphere and circulates close to its circumference. These modes are sensitive to the adsorption
of (bio-) molecules onto the resonator surface upon which the WGM spectrum is shifted towards higher wavelengths.
Compared to single particles, clusters of microresonators offer the advantage of being more easily detected due to their
higher radiative emission power. Further, the lineshape of the spectra obtained from clusters depends crucially on their
composition and therefore may be used as a fingerprint for their identification, e.g., for sensing applications in array
formats. Our results demonstrate that clusters of microresonators show the same sensitivity and performance as single
spheres. The adsorption of layers of polyelectrolytes and bovine serum albumin (BSA) onto clusters of spheres with
10 μm diameter has been monitored in situ. Depending on the choice of materials, we achieved a mass sensitivity limit
of 50 fg, which is about 100 times more sensitive than that of state-of-the-art WGM biosensors.
In this work, we aim at enhancing the sensitivity of surface plasmon resonance sensors towards the detection of
biomolecule interactions by means of nanopatterning of the sensor surface. Use of nanostructured interfaces in
combination with SPR is a promising step towards realizing biosensors with high efficiency and sensitivity.
Nanopatterned surfaces enable multi-dimensional control over the behavior of surface-immobilized probe molecules. By
means of a combination of self-assembled monolayer technology, colloidal lithography, and reactive ion etching,
nanopatterns with either antibody confining or non-confining characteristics were produced and analyzed via
photoelectron spectroscopy and infrared reflection absorption spectroscopy. Antibody immobilization on the patterns and
subsequent specific binding of antigen was traced in real time by means of a surface plasmon resonance sensor. It was
found that confining nanopatterns yield an increase in antibody activity towards antigen capture on surface of up to
120%, depending on the protocol used for their immobilization.
The utilization of self-assembly mechanisms for the controlled deposition of nanoparticles at surfaces and interfaces recently has gained increasing popularity. A variety of methods, ranging from the use of purely physical phenomena to the application of chemical functionalization of the particles and/or the surface, have been proposed for the fabrication of two-dimensional mesoscopic structures based on nanoparticle assemblies. Potential applications are found in chemical and biological sensing, photonics, mesoscopic optics, and mesoscale electronics. Here, we present our recent results on the controlled deposition of monodisperse polystyrene (PS) latex particles onto chemically modified surfaces by use of small organic molecules added in proper amounts to the suspensions. In particular, the role of entropic forces in screening chemical selectivity for surface adsorption is elucidated. Thereby, a route for the controlled deposition of the PS particles onto carboxyl-functionalized surface areas utilizing carbodiimide chemistry is developed.
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