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ABSTRACT: The spatial resolution and high sensitivity of tip-enhanced Raman spectroscopy allows the characterization of surface features on a nano-scale. This technique is used to visualize silicon-based structures, which are similar in width to the transistor channels in present leading-edge CMOS devices. The reduction of the intensive far-field background signal is crucial for detecting the weak near-field contributions and requires beside a careful alignment of laser polarization and tip axis also the consideration of the crystalline sample orientation. Despite the chemical identity of the investigated sample surface, the structures can be visualized by the shift of the Raman peak positions due to the patterning induced change of the stress distribution within lines and substrate layer. From the measured peak positions the intrinsic stress within the lines is calculated and compared with results obtained by finite element modeling. The results demonstrate the capability of the tip-enhanced Raman technique for strain analysis on a sub-50 nm scale.Highlights► We visualize SiGe nanostructures by mapping the sample with tip-enhanced Raman spectroscopy. ► Appropriate alignment of SiGe sample reduces intensive far-field background signal. ► Results demonstrate non-destructive strain characterization on sub-50 nm scale in semiconductors.
Ultramicroscopy 09/2011; 111(11):1630-1635. · 2.47 Impact Factor
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ABSTRACT: We present the first dynamic study of damage mechanisms in nanosized on-chip Cu interconnects caused by stress-induced voiding in advanced integrated circuits. Synchrotron-based transmission x-ray microscopy is applied to visualize the void evolution and conical dark-field analysis in the transmission electron microscopy to characterize the Cu microstructure. Our x-ray microscopy measurements showed, in contradiction to electromigration studies, no void movement over large dimensions during the stress-induced void evolution. We observed in via/line Cu interconnect structures that voids are formed directly beneath the via, i.e., in the Cu wide line at the edge of the via bottom. It is concluded that voids are originally formed at the site where eventually the catastrophic failure occurs. During stress migration tests, Cu atoms migrate from regions of low stress to regions of high tensile stress, and simultaneously, vacancies migrate along the stress gradient (within a limited range of some microns) in the opposite direction to the location where small vias connect wide Cu lines. The stress distribution and the driving forces for atomic transport depend strongly on the particular geometry of the tested structure but also on interface bonding and metal microstructure. Vacancies form agglomerates and subsequently voids that grow further. The void growth rate depends on the Cu thin film material and its microstructure, particularly the grain size and the grain orientations. The Cu microstructure in the surroundings of the formed void shows that Cu grains are predominantly (111) oriented relatively to the wafer surface. Interfaces and grain boundaries, and particularly their orientation, determine the void evolution dynamics.
Journal of Applied Physics 12/2009; · 2.17 Impact Factor
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ABSTRACT: The adhesive and cohesive properties of organosilicate thin films are remarkably insensitive to UV curing. We demonstrate how to maximize these properties with UV standing waves together with an optical spacer underlying layer. Using a simulation of the UV cure profile through the film thickness, we demonstrate how a UV transparent SiN optical spacer layer can be selected to maximize curing at both sides of the organosilicate film with marked increases in interfacial fracture energy. On the contrary, a UV absorbing SiCN underlying layer resulted in significantly reduced UV intensities and small improvements of the interfacial fracture energies.
Applied Physics Letters 08/2009; 95(7):071902-071902-3. · 3.84 Impact Factor
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ABSTRACT: This study demonstrates that ultraviolet (UV) radiation curing can control depth profiles of organosilicate films. Striking differences between the effects of monochromatic and broadband UV irradiation were observed. For the same as-deposited organosilicate film and cure duration, monochromatic radiation has a greater impact on film structure, elastic modulus, and fracture resistance, but also results in a greater degree of depth dependent properties. Oscillating elastic modulus through the film thickness was observed with force modulation atomic force microscopy. We present a new standing wave model that accurately predicts the resulting depth dependent stiffness variations considering changes in film shrinkage and refractive index in terms of curing time, and can further be used to account for initial film thickness dependence of UV curing and film absorption. Promising applications of the depth dependent UV curing to produce multifunctional ultralow- k layers with a single postdeposition curing process are discussed.
Journal of Applied Physics 11/2008; · 2.17 Impact Factor
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ABSTRACT: For successfully developing and controlling BEoL structures of the 32 nm CMOS technology node and beyond, advanced analytical techniques are needed for process development and control, for physical failure localization and analysis as well as for the investigation of reliability-limiting degradation mechanisms. These challenges are discussed from the point of view of a high volume leading-edge manufacturing.
Interconnect Technology Conference, 2008. IITC 2008. International; 07/2008
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ABSTRACT: UV radiation curing has emerged as a promising postdeposition curing treatment to strengthen organosilicate interlayer dielectric thin films. We provide the evidence of film depth dependent UV curing which has important effects on through thickness mechanical and fracture properties. Force modulation atomic force microscopy measurements of the elastic modulus through the thickness of the films revealed evidence of periodic modulations of the glass stiffness which increased in magnitude with UV curing time. Furthermore, while significant increases in fracture energy were observed with UV curing time at the top of the organosilicate film, much lower increases were observed at the bottom. The increase in fracture energy with UV curing was film thickness dependent. The cohesive fracture resistance was less sensitive to UV curing. Possible explanations for the stiffness modulations through the film thickness involving UV light interference or phase separation by spinodal decomposition during the cure process are described. © 2008 American Institute of Physics.
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ABSTRACT: Nanolithography based on local anodic oxidation (LAO) by atomic force microscopy is a promising technique for patterning strained film nanostructures on the silicon substrates. Due to its versatility and precise control, LAO is suited for preparing well defined calibration structures for local strain measurements. We investigated silicon–germanium patterns prepared by LAO and subsequent selective anisotropic wet etching. By combining the nanolithography and etching, dedicated strain test structures with a line width of 65 nm were achieved and utilized for calibration of tip-enhanced Raman measurements.
Thin Solid Films 518(12):3267-3272. · 1.89 Impact Factor
