Metal silicides have played an indispensable role in the rapid developments of microelectronics since PtSi was first used to improve the rectifying characteristics of diodes in early 1960s. This wo ...

Metal silicides in CMOS technology : Past, present, and future trends

Synthesis of c-axis oriented AlN thin films on different substrates: A review

integrations and challenges of novel high-k gate stacks in advanced cmos technology

Field-Effect Transistor sensors (FET-sensors) have been receiving increasing attention for biomolecular sensing over the last two decades due to their potential for ultra-high sensitivity sensing, label-free operation, cost reduction and miniaturisation. Whilst the commercial application of FET-sensors in pH sensing has been realised, their commercial application in biomolecular sensing (termed BioFETs) is hindered by poor understanding of how to optimise device design for highly reproducible operation and high sensitivity. In part, these problems stem from the highly interdisciplinary nature of the problems encountered in this field, in which knowledge of biomolecular-binding kinetics, surface chemistry, electrical double layer physics and electrical engineering is required. In this work, a quantitative analysis and critical review has been performed comparing literature FET-sensor data for pH-sensing with data for sensing of biomolecular streptavidin binding to surface-bound biotin systems. The aim is to provide the first systematic, quantitative comparison of BioFET results for a single biomolecular analyte, specifically streptavidin, which is the most commonly used model protein in biosensing experiments, and often used as an initial proof-of-concept for new biosensor designs. This novel quantitative and comparative analysis of the surface potential behaviour of a range of devices demonstrated a strong contrast between the trends observed in pH-sensing and those in biomolecule-sensing. Potential explanations are discussed in detail and surface-chemistry optimisation is shown to be a vital component in sensitivity-enhancement. Factors which can influence the response, yet which have not always been fully appreciated, are explored and practical suggestions are provided on how to improve experimental design.

https://pubs.rsc.org/en/content/articlepdf/2017/an/c7an00455a

Field-effect sensors – from pH sensing to biosensing: sensitivity enhancement using streptavidin–biotin as a model system

Nanobiosensors based on silicon nanowire field effect transistors offer advantages of low cost, label-free detection, and potential for massive parallelization. As a result, these sensors have often been suggested as an attractive option for applications in point-of-care (POC) medical diagnostics. Unfortunately, a number of performance issues, such as gate leakage and current instability due to fluid contact, have prevented widespread adoption of the technology for routine use. High-k dielectrics, such as hafnium oxide (HfO(2)), have the known ability to address these challenges by passivating the exposed surfaces against destabilizing concerns of ion transport. With these fundamental stability issues addressed, a promising target for POC diagnostics and SiNWFETs has been small oligonucleotides, more specifically, microRNA (miRNA). MicroRNAs are small RNA oligonucleotides which bind to mRNAs, causing translational repression of proteins, gene silencing, and expressions are typically altered in several forms of cancer. In this paper, we describe a process for fabricating stable HfO(2) dielectric-based silicon nanowires for biosensing applications. Here we demonstrate sensing of single-stranded DNA analogues to their microRNA cousins using miR-10b and miR-21 as templates, both known to be upregulated in breast cancer. We characterize the effect of surface functionalization on device performance using the miR-10b DNA analogue as the target sequence and different molecular weight poly-l-lysine as the functionalization layer. By optimizing the surface functionalization and fabrication protocol, we were able to achieve <100 fM detection levels of the miR-10b DNA analogue, with a theoretical limit of detection of 1 fM. Moreover, the noncomplementary DNA target strand, based on miR-21, showed very little response, indicating a highly sensitive and highly selective biosensing platform.

/pdf/silicon-nanowires-with-high-k-hafnium-oxide-dielectrics-for-44c2ju9wmz.pdf

Silicon nanowires with high-k hafnium oxide dielectrics for sensitive detection of small nucleic acid oligomers.

Continuous and uniform Ni(Si,Ge) layers are formed on polycrystalline Si and Si042Ge058 substrate films at 500 degreesC by rapid thermal processing The germanosilicide is identified as NiSi042G 

Morphological and phase stability of nickel–germanosilicide on Si1−xGex under thermal stress

Hillocks, small outgrowths on a film surface, form when compressional stresses in an aluminum film are relaxed at elevated temperature (≥90 °C), for instance during the phase of rising temperature in an annealing cycle. This paper reports a study of hillock formation in Al films of thicknesses in the interval 0.25–2.2 μm and which have been deposited by electron beam evaporation. Hillock sizes, shapes, number and formation temperatures were determined, the latter on a heating stage in situ in a scanning electron microscope. The internal structure of the hillocks was studied by cross‐sectional transmission electron microscopy technique. These studies provided strong support for the idea that hillocks are formed by migration of material along grain boundaries, presumably at triple junctions, up to the surface where it is deposited in a growing hillock. Initially, the hillocks are separated from the original film surface by a grain boundary‐like interface, but prolonged annealing will cause underlaying grain...

A transmission electron microscopy study of hillocks in thin aluminum films

The formation of nanometric Ni silicide films on a Si wafer is analyzed using differential scanning calorimetry (DSC) and isothermal x-ray diffraction measurements. The sensitivity of DSC is remarkable even in this experimental configuration constituted of a Ni∕Si bilayer deposited on a Si substrate. Both methods confirm the sequential growth of Ni2Si and NiSi (for T<700°C). However the kinetics of growth of the first silicide formed (Ni2Si) cannot be fitted, for the two sets of measurements, by a simple parabolic law. Better agreement is obtained using a linear-parabolic growth law and a smaller activation energy for the linear term (0.8 eV) than for the parabolic one (1.5 eV).

Differential scanning calorimetry analysis of the linear parabolic growth of nanometric Ni silicide thin films on a Si substrate

This article reports a systematic study of local stress relaxationeffects in thin Alfilms,deposited on silicon substrates by sputtering or electron beam evaporation. The stresses were induced thermally during an annealing cycle, as well as thermomechanically by micromechanical technique. The latter experiments were performed i n s i t u in the vacuum chamber of a scanning electron microscope(SEM), which made it possible to monitor the reconstruction of the film surface as it happened, and simultaneously register applied forces, strains, and temperatures. Three fundamental, local stress relaxation phenomena were observed. Compressive film stresses were, at elevated temperature, relaxed by hillock formation. The i n s i t u experiments in the SEM, combined with cross‐sectional transmission electron microscopy of hillock structures, provided important information on the growth mechanism of hillocks. Tensional film stresses at elevated temperature were relaxed by two modes of local stress relief. One mode of tensional stress relief occurred in films of thickness 1 μm or more. Singular Al grains were observed to ‘‘collapse’’ and become wider and thinner than neighboring grains. Such grain collapses are scarcely reported by previous workers, and were in the present investigation seen to occur very suddenly, in a second or less, as the strain and the temperature reached critical levels. A collapse mechanism, based on local plastic yield and interfacial slip, is suggested. Films of submicron thickness relaxed by a second mode: hole formation. Essentially two types of holes were observed: small, circular holes and large branched‐out holes. A hole formation mechanism, based on creep cavitation and interfacial slip, is suggested. The observed holes resemble the ‘‘voids’’ many other workers have reported in narrow, passivated Al lines. The present results show that passivation coatings and narrow geometries are not necessary prerequisites for holes in Alfilms; a high tensional film stress is enough.

Local stress relaxation phenomena in thin aluminum films

The morphological stability of NiSi1−uGeu ternary alloy films formed by reacting Ni with single-crystal (sc) and polycrystalline (poly) Si1−xGeu is studied (u can be different from x). The agglomeration of NiSi1−uGeu films on Si0.7Ge0.3 occurs at 550°C after rapid thermal processing for 30 s, independently of the crystallinity of the Si1−xGeu. This behavior distinctly different from NiSi: NiSi films on poly-Si display a poorer morphological stability and degrade at lower temperatures than NiSi on sc-Si. On strained Si1−xGex, the presence of Ge simultaneously gives rise to two effects of different origin: mechanical and thermodynamic. The main driving forces behind the agglomeration of NiSi1−uGeu on sc-Si1−xGex are found to be the stored strain energy in the Si1−xGex and the larger (absolute) free energy of formation of NiSi compared to NiGe. The latter constitutes the principal driving force behind the agglomeration of NiSi1−uGeu on poly-Si1−xGex and is not affected by the degree of crystallinity of Si1−x...

Morphological instability of NiSi1−uGeu on single-crystal and polycrystalline Si1−xGex

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