Reliability challenges for copper low-k dielectrics and copper diffusion barriers

The performance of interconnects containing micro- (pore size smaller than 2 nm) and meso-porous (pore size larger than 2 nm) interlevel dielectrics is influenced by material selection, integration scheme and virtually all fabrication steps. It is generally reported that the reliability margin of the dielectric/barrier/copper system is shrinking. Barrier and dielectric integrity play a most important role in line-to-line leakage and Time Dependent Dielectric Breakdown (TDDB) reliability. TDDB has never been an issue for Cu-SiO₂ interconnects, but for sub-100 nm copper/barrier/low-k systems it becomes challenging. When monitoring the integrated dielectric properties early failures can be caused by weak integration interfaces, dielectric damage during the integration, defective diffusion barrier or other non-uniformities related to the damascene process. Recent advances are reviewed along with examples and reference to state of the art.     

CMOS and SiGe bipolar circuits for applications up to 110 GHz

Recently, CMOS has been demonstrated to be a viable technology for very-high-bit-rate broad-band and wireless communication systems up to 40 Gb/s and 50 GHz. Advances in device scaling and doping-profile optimization have also resulted in SiGe bipolar transistors with impressive performance, including cut-off frequencies of more than 200 GHz. This paper presents advances in circuit design which fully exploit the high-speed potential of a 0.13 µm CMOS technology up to 50 GHz and of a high-performance SiGe bipolar technology up to 110 GHz operating frequency. The combination of advanced circuit techniques and a state-of-the-art fabrication-process technology results in continuing the upward shift of the frequency limits.     

Influence of metal gate and capping film stress on TANOS cell performance

In this work it is shown that film stress in the gate stack of TANOS NAND memories plays an important role for cell device performance and reliability. Tensile stress induced by a TiN metal gate deteriorates TANOS cell retention compared to TaN gate material. However, the erase saturation level as well as cell endurance is improved by the use of a TiN gate. This trade-off between retention and erase saturation for TANOS cells is elaborated in detail.     

Germanium islands embedded in strained silicon quantum wells grown on patterned substrates

Germanium islands were embedded in strained silicon quantum wells in order to provide an improved electron confinement in vicinity of the islands. Growth was performed on relaxed SiGe layers. Patterned substrates were used, favouring lattice relaxation as well permitting the fabrication of small Ge islands at deposition temperatures above 500 °C. Photoluminescence analysis reveals a strongly reduced dislocation related signal. The low temperature spectra are dominated by intense signals from the germanium islands. The origin of these signals were investigated by removing the islands by etching, analysing reference samples without a silicon quantum well, varying the germanium deposition and the growth temperature.     

InGaAsSb(Gd)/InAsSbP double heterostructure lasers (λ=3.0–3.3 µm) for diode laser spectroscopy

Data on threshold currents, the differential quantum efficiency, the emission spectrum, current tuning, and radiation power of mesastripe InGaAsSb(Gd)/InAsSbP double heterostructure lasers with λ=3.0–3.3 µm and a cavity length of 70–150 µm in a temperature range of 50–107 K are reported. In the experiments, the threshold currents I _th<10 mA, a total output power of 0.5 mW/facet, and a single-mode power of 0.43 mW at 77 K in the cw regime were obtained. Lasers operated in the single-mode regime at currents I≤6I _th, the spectral purity was as high as 650: 1, the tuning rate was 210 cm^?1/A, and the tuning range was 10 cm^?1 wide. An example of methane detection at 3028.75 cm^?1 is presented.     

Inwards Interweaving of Polymeric Layers within Hydrogels: Assembly of Spherical Multi‐Shells with Discrete Porosity Differences

The unique inwards interweaving morphology of polyamines and polyacids within agarose hydrogels that leads to the formation of striated shells with different porosities within the spherical scaffold is reported. Microcompartments with sophisticated structures are commonly used in drug delivery, tissue engineering, and other biomedical applications. However, a method capable of producing well‐defined, multiporous shells within a single compartment is still lacking. By the alternating deposition of polyallylamine (PA) and polystyrenesulfonic acid (PSS) in 1‐butanol, at equal mass ratios, multiple levels of porosity are generated within an agarose microsphere. Each level of porosity is represented by a well‐defined, concentric shell of interweaving PA and PSS layers. The number, thickness, and porosity of the striated shells can be easily controlled by varying the number of PA/PSS bilayers and the polymer concentration, respectively. The feasibility of utilizing this morphology for the assembly of a multi‐shell porous spherical scaffold is validated by trapping different molecular weight dextrans within different regions of porosity. The unique interaction of polyacids and polyamines in hydrogels represents a facile and inexpensive approach to the development of intricate scaffold architectures.     

Erhitzen von Weizen

Zusammenfassung Teige aus erhitzten Weizenkörnern (45–75 °C/6 min bei 20% Wassergehalt) wurden mit der Capillarviscosimetrie und mit einem Mikrobackversuch untersucht. Beide Methoden zeigten eine erhitzungsbedingte Verfestigung des Klebers an. Eine Untersuchung der Mehlproteine ergab bei der Osbornefraktionierung eine Verschiebung von Albuminen/Globulinen in den Rückstand. Zugversuche sowie calorimetrische Messungen mit hitzebehandeltem Kleber lassen auf Konformationsänderungen der Proteine als Ursache für die Kleberverfestigung schließen.

---

Heating of wheat. 2. Rheological and baking behaviour, changes in Osborne fractions

Dough from heated wheat kernels (45–75° C/ 6 min, 20% water content) were examined by capillary viscosimetry and by a micro-baking test. Both methods showed an increase in gluten strength. Osborne fractionation of the proteins showed a shift of albumins/globulins to the residual protein. Load-extension tests and calorimetric measurements with heat-treated gluten led to the conclusion that changes in protein conformation are responsible for the increase in gluten strength.