Subsurface metrology using scanning white light interferometry : absolute z coordinates deep inside displays

Mobile devices with interactive displays are ubiquitous commodities. Efficient quality control (QC) drives competitiveness. Scanning white light interferometry imaging offers a fast and nondestructive tool for QC purposes. Relying on optical compensation and image stitching, one can rapidly and cost-effectively produce sharp 3D images of a display's inner structures with a few nanometers' accuracy along the z direction. As a practical example, 3D images of a mobile device display revealed 0.92 +/- 0.02 mu m height variation in the top glass assembly. The proposed method improves quality assurance methods of display manufacturing. (c) 2017 Optical Society of AmericaPeer reviewe

Elastic and fracture properties of free-standing amorphous ALD Al2O3 thin films measured with bulge test

We have investigated elastic and fracture properties of amorphous Al2O3 thin films deposited by atomic layer deposition (ALD) with bulge test technique using a free-standing thin film membrane and extended applicability of bulge test technique. Elastic modulus was determined to be 115 GPa for a 50 nm thick film and 170 GPa for a 15 nm thick film. Residual stress was 142 MPa in the 50 nm Al2O3 film while it was 116 MPa in the 15 nm Al2O3 film. Density was 3.11 g cm(-3) for the 50 nm film and 3.28 g cm(-3) for the 15 nm film. Fracture strength at 100 hPa s(-1) pressure ramp rate was 1.72 GPa for the 50 nm film while for the 15 nm film it was 4.21 GPa, almost 2.5-fold. Fracture strength was observed to be positively strain-rate dependent. Weibull moduli of these films were very high being around 50. The effective volume of a circular film in bulge test was determined from a FEM model enabling future comparison of fracture strength data between different techniques.Peer reviewe

Wide field of view 3D label-free super-resolution imaging

Recently, 3D label-free super-resolution profilers based on microsphere-assisted scanning white light interferometry were introduced having vertical resolution of few angstroms (angstrom) and a lateral resolution approaching 100 nm. However, the use of a single microsphere to generate the photonic nanojet (PNJ) limits their field of view. We overcome this limitation by using polymer microfibers to generate the PNJ. This increases the field of view by order of magnitude in comparison to the previously developed solutions while still resolving sub 100 nm features laterally and keeping the vertical resolution in 1 nm range. To validate the capabilities of our system we used a recordable Blu-ray disc as a sample. It features a grooved surface topology with heights in the range of 20 nm and with distinguishable sub 100 nm lateral features that are unresolvable by diffraction limited optics. We achieved agreement between all three measurement devices across lateral and vertical dimensions. The field of view of our instrument was 110 mu m by 2 mu m and the imaging time was a couple of seconds.Peer reviewe

Label-free 3D super-resolution nanoscope with large field of view

Photonic nanojet interferometry (PM) permits three dimensional (3D) label-free and super-resolution surface characterization. PM is based on coherence scanning interferometry (CSI), featuring Angstrom level vertical resolution. Being an optical far-field technique, CSI is diffraction limited and according to the Abbe criteria, can laterally resolve, points that are separated by a few hundred nanometers. We overcame this limitation by using dielectric microspheres that generate photonic nanojets. Now sub 100 nm features can laterally be resolved while preserving the vertical resolution of the CSI system. The microsphere material could be polymer or glass with a diameter between 8 and 12 mu m, which limits the field of view (FoV) of the PNI system to similar to 10 mu m(2). Here we present a method to increase the FoV of a PNI based device by stitching a sequence of adjacent 3D images. We imaged a recordable Blu-ray Disc (BR-D) using a custom built Mirau type scanning white light interferometer with enhanced lateral resolution. Four 3D super-resolution images with constant 80% overlap, were stitched together using in-house software. The resulting high fidelity image shows that 45% overlap and the above described procedure could be used to enlarge the FoV of label-free 3D super-resolution imaging systems.Peer reviewe

3D Super-Resolution Optical Profiling Using Microsphere Enhanced Mirau Interferometry

We present quantitative three dimensional images of grooves on a writable Blu-ray Disc based on a single objective Mirau type interferometric microscope, enhanced with a microsphere which is considered as a photonic nanojet source. Along the optical axis the resolution of this microsphere assisted interferometry system is a few nanometers while the lateral resolution is around 112 nm. To understand the physical phenomena involved in this kind of imaging we have modelled the interaction between the photonic jet and the complex disc surface. Agreement between simulation and experimental results is demonstrated. We underline that although the ability of the microsphere to generate a photonic nanojet does not alone explain the resolution of the interferometer, the nanojet can be used to try to understand the imaging process. To partly explain the lateral super-resolution, the potential role of coherence is illustrated. The presented modality may have a large impact on many fields from bio-medicine to nanotechnology.Peer reviewe

System spectrum conversion from white light interferogram

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Super-resolution photonic nanojet interferometry : photonic nanojet interaction with a polymer sample

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Preventing Formation of Metal Dendrites During Electroplating Using External Ultrasonic Actuators

Metal dendrites are tree-like formations caused by the uneven deposition of ions onto a substrate. In electroplating, dendrites are generally undesired due to the resultant uneven and brittle surface. Furthermore, in metal batteries dendritic growth irreversibly consumes active metals and can eventually cause a short-circuit between the electrodes. Applying ultrasound to reduce dendrite growth has previously been achieved with integrated actuators. However, implementation of integrated actuation has significant drawbacks: it compromises optimal design and needs to be incorporated in early development, since retrofitting to existing designs is cumbersome or impossible. External actuation would solve these limitations. We show that external ultrasound reduces non-uniform dendrite growth during electroplating up to a threshold deposition current. Below the threshold dendrite growth was significantly inhibited and a uniform plating was formed. The results demonstrate that external ultrasonic transducers could be retrofitted to existing systems to suppress dendrite growth.Peer reviewe

Round Robin test on V-shape bio-imaging transfer standard for determination of the Instrument Transfer Function of 3D optical profilers

A V-shape Bio-Transfer-Standard (V-BTS), developed and produced at the University of Helsinki (UH), was measured in two laboratories. In comparison to Siemens Star calibration specimens, the V-BTS performs better at high lateral frequencies close to the diffraction limit of the optical instrument. This peunits deteunining of the Instrument Transfer Function (ITF). The V-BTS features two lipid bilayer steps that partly overlap each other at an angle of 20, with an average height of 4.6 +/- 0.1 nm. The Round Robin (RR) test aims to determine whether the V-BTS and the developed application protocol work with different optical profilers in different laboratories. First the artefact was measured at Sensofar-Tech, S.L. using an S-neox profiler working in Phase Shifting Interferometry mode. Then V-BTS was measured at UH using a custom-built Scanning White Light Interferometer. All measurements done by four different operators at the two laboratories have a range or standard deviation of 0.1 nm which agrees with the theoretical estimates and with measurements done using an atomic force microscope and with a surface plasmon resonance based instrument. The RR results show the applicability of the V-BTS for calibration and for ITF characterization of 3D optical profilers.Peer reviewe

Microsphere-assisted phase-shifting profilometry

In the present work, we have investigated the combination of a superresolution microsphere-assisted 2D imaging technique with low-coherence phase-shifting interference microscopy. The imaging performance of this technique is studied by numerical simulation in terms of the magnification and the lateral resolution as a function of the geometrical and optical parameters. The results of simulations are compared with the experimental measurements of reference gratings using a Linnik interference configuration. Additional measurements are also shown on nanostructures. An improvement by a factor of 4.7 in the lateral resolution is demonstrated in air, thus giving a more isotropic nanometric resolution for full-field surface profilometry in the far field. (C) 2017 Optical Society of AmericaPeer reviewe