Nitride Si Research Articles

Hybrid orientation technology and strain engineering for ultra-high speed MOSFETs

We report here RF MOSFET performance in sub-45-nm hybrid orientation CMOS technology. Based on the combination of hybrid orientation technology (HOT) and process-induced local strain engineering, MOSFET RF performance is investigated using CAD (TCAD) technology. Transistor optimization on (100) substrate via silicon nitride (Si 3 N 4 ) cap layer thickness for n-MOSFETs, Ge mole fraction optimization for p-MOSFETs on (110) substrates and channel length scaling have resulted in record RF performance, viz. the cut-off frequency, \({f_{\rm T}}\).

초임계 이산화탄소를 이용한 웨이퍼의 건식 식각에서 알콜 첨가제의 효과

초임계 이산화탄소를 이용하여 희생 <TEX>$SiO_2$</TEX>층에 대한 건식 식각 실험을 진행하였다. HF/pyridine (HF/py) 식각액과 알콜 첨가제를 사용하여 이중 챔버 시스템 방식으로 boron phosphor silica glass (BPSG), tetraethyl orthosilicate (TEOS), thermal <TEX>$SiO_2$</TEX>와 Si-nitride (SiN)의 박막 층에 대한 식각 성능을 조사하였다. 메탄올의 첨가에 의하여 실리카 희생막에 대한 HF/py의 식각률이 높아지는 것을 확인할 수 있었다. BPSG를 제외하고는 메탄올이 가장 높은 식각률을 보여줬지만, BPSG의 SiN에 대한 식각 선택비는 이소프로판올이 가장 높았다. HF/py/MeOH 계의 건식 식각반응에서 반응 온도에 따라서 박막별 식각률이 증가하였다. 특히 반응 온도 증가에 따라 BPSG의 식각 속도의 증가폭이 매우 높게 나타났다. HF/py에 알콜 공용매를 첨가하여도 식각 부산물 감소에는 크게 효과가 없었다. HF/<TEX>$H_2O$</TEX>의 식각률이 HF/py/alcohol 보다 높게 나타났지만 HF/<TEX>$H_2O$</TEX>에 알콜 공용매를 첨가하였을 때는 오히려 식각률이 감소되었다. 캔틸레버 빔 구조를 초임계 이산화탄소 건식 식각으로 제조하여 높은 종횡비의 패턴구조물을 손상 없이 성공적으로 식각할 수 있었다. The dry etching of sacrificial <TEX>$SiO_2$</TEX> was performed in supercritical carbon dioxide. The etching of boron phosphor silica glass (BPSG), tetraethyl orthosilicate (TEOS), thermal <TEX>$SiO_2$</TEX>, and Si-nitride (SiN) was investigated by using a two chamber system with HF/py etchant and alcohol additives. The etch rate of sacrificial <TEX>$SiO_2$</TEX> increased upon the addition of methanol. The etch selectivity of BPSG with respect to SiN was highest with IPA although the highest etch rate was resulted from methanol except BPSG. The etch rate increased with the temperature in HF/py/MeOH system. Especially the increase of the etch rate was much higher for BPSG with an increase in the reaction temperature. The etch residue was not reduced apparently upon the addition of alcohol cosolvents to HF/py. While the etch rate in HF/<TEX>$H_2O$</TEX> was higher than HF/py/alcohol system, the rate decreased with the addition of alcohols to HF/<TEX>$H_2O$</TEX>. The cantilever beam structure of high aspect ratios was released by the dry ething in supercritical carbon dioxide without damage.

Superstructure of self-aligned hexagonal GaN nanorods formed on nitrided Si(111) surface

We present here the spontaneous formation of catalyst-free, self-aligned crystalline (wurtzite) nanorods on Si(111) surfaces modified by surface nitridation. Nanorods grown by molecular beam epitaxy on bare Si(111) and non-stoichiometric silicon nitride interface are found to be single crystalline but disoriented. Those grown on single crystalline Si3N4 intermediate layer are highly dense c-oriented hexagonal shaped nanorods. The morphology and the self-assembly of the nanorods shows an ordered epitaxial hexagonal superstructure, suggesting that they are nucleated at screw dislocations at the interface and grow spirally in the c-direction. The aligned nanorod assembly shows high-quality structural and optical emission properties.

Voltage-Driven Translocation of DNA through a High Throughput Conical Solid-State Nanopore

Nanopores have become an important tool for molecule detection at single molecular level. With the development of fabrication technology, synthesized solid-state membranes are promising candidate substrates in respect of their exceptional robustness and controllable size and shape. Here, a 30–60 (tip-base) nm conical nanopore fabricated in 100 nm thick silicon nitride (Si3N4) membrane by focused ion beam (FIB) has been employed for the analysis of λ-DNA translocations at different voltage biases from 200 to 450 mV. The distributions of translocation time and current blockage, as well as the events frequencies as a function of voltage are investigated. Similar to previously published work, the presence and configurations of λ-DNA molecules are characterized, also, we find that greater applied voltages markedly increase the events rate, and stretch the coiled λ-DNA molecules into linear form. However, compared to 6–30 nm ultrathin solid-state nanopores, a threshold voltage of 181 mV is found to be necessary to drive DNA molecules through the nanopore due to conical shape and length of the pore. The speed is slowed down ∼5 times, while the capture radius is ∼2 fold larger. The results show that the large nanopore in thick membrane with an improved stability and throughput also has the ability to detect the molecules at a single molecular level, as well as slows down the velocity of molecules passing through the pore. This work will provide more motivations for the development of nanopores as a Multi-functional sensor for a wide range of biopolymers and nano materials.

Combined Poisson and Soft-Particle DLVO Analysis of the Specific and Nonspecific Adhesion Forces Measured between L. monocytogenes Grown at Various Temperatures and Silicon Nitride

Adhesion forces between pathogenic L. monocytogenes EGDe and silicon nitride (Si(3)N(4)) were measured using atomic force microscopy (AFM) under water and at room temperature for cells grown at five different temperatures (10, 20, 30, 37, and 40 °C). Adhesion forces were then decoupled into specific (hydrogen bonding) and nonspecific (electrostatic and Lifshitz-van der Waals) force components using Poisson statistical analysis. The strongest specific and nonspecific attraction forces were observed for cells grown at 30 °C, compared to those observed for cells grown at higher or lower temperatures, respectively. By combining the results of Poisson analysis with the results obtained through soft-particle Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis, the contributions of the Lifshitz-van der Waals and electrostatic forces to the overall nonspecific interaction forces were determined. Our results showed that the Lifshitz-van der Waals attraction forces dominated the total nonspecific adhesion forces for all investigated thermal conditions. However, irrespective of the temperature of growth investigated, hydrogen bonding forces were always stronger than the nonspecific forces. Finally, by combining Poisson analysis with soft-particle analysis of DLVO forces, the closest separation distances where the irreversible bacterial adhesion takes place can be determined relatively easily. For all investigated thermal conditions, the closest separation distances were <1 nm.

Microstructure, mechanical properties and wetting behavior of F: Si–C–N films as bio-mechanical coating grown by DC unbalanced magnetron sputtering

A systematic structure and properties investigation on the deposition of fluorinated silicon–carbon–nitride (Si–C–N) films under varying CF4 flows was carried out by direct current unbalanced magnetron sputtering techniques. Significant role of fluorine and carbon-doped on growth characteristics and mechanical properties in the film was observed. The chemical bonding configurations, surface topography and mechanical properties were characterized by means of X-ray photoelectron spectroscopy (XPS), Raman and infrared spectroscopies, atomic force microscopy (AFM) and nano-indentation technique and CSM pin-on-disk tribometer. It was found that the as-deposited F: Si–C–N films are amphipathic nature, and large variations took place these films’ deposition rate, composition, microstructure and mechanical properties when CF4 flows varied from 0 to 9sccm. At CF4 gas flow rate 9sccm, the F: Si–C–N coatings demonstrated a fluorine content of 5.95at.% and a moderate friction coefficient of 0.03. It is obvious from the hardness results that the F: Si–C–N coating enhances the hardness of the Co–Cr–Mo alloy to approximately 16.3GPa on a smoother surface. The tribological characterization of Co–Cr–Mo alloy with F: Si–C–N coating sliding against ultrahigh molecular weight polyethylene (UHMWPE) counter-surface in fetal bovine serum, shows that the wear resistance of the F: Si–C–N coated Co–Cr–Mo alloy/UHMWPE sliding pair show much obviously improvement over that of uncoated Co–Cr–Mo alloy/UHMWPE sliding pair. The F: Si–C–N and Si–N films have potential properties for joint surface modification applications.

In situ study of self-assembled GaN nanowires nucleation on Si(111) by plasma-assisted molecular beam epitaxy

Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy is studied through a combination of two in situ tools: grazing incidence x-ray diffraction and reflection high energy electron diffraction. Growth on bare Si(111) and on AlN/Si(111) is compared. A significantly larger delay at nucleation is observed for nanowires grown on bare Si(111). The difference in the nucleation delay is correlated to a dissimilarity of chemical reactivity between Al and Ga with nitrided Si(111).

Modeling of surface cracks in rolling contact

► We investigate the detrimental effect of surface cracks, which are typical defects in ceramics. ► Applying the finite element method, we model rolling of a cracked ball. ► By using fracture mechanics, the risk of fatigue crack propagation is estimated. ► Our parametric analysis boosts understanding of fatigue in engineering ceramics. Superior physical properties of engineering ceramics are well recognized in modern technology. However, high brittleness is typical for these materials, which leads to low resistance to crack initiation and propagation. In the silicon nitride (Si 3 N 4 ) balls, whose failure is studied here, the most dangerous pre-existing defect is the so called C-crack – the circumferential surface crack of conical shape, formed during the ball manufacturing process. The finite elements method is used for the simulation of rolling of the cracked ball. By applying the linear elastic fracture mechanics approach, the crack criticality in terms of the stress intensity factors is identified. The parametric study regarding the levels of the contact load, crack shape, depth and friction coefficient between crack's surfaces is presented.

The role of nitridation of nc-Si dots for improving performance of nc-Si nonvolatile memory

We report a nc-Si nonvolatile memory (NVM) device with nitrided nc-Si dots embedded in a floating gate. LPCVD was used to deposit a layer of nc-Si on the tunnel oxide layer at the pressure of 350mTorr. Subsequently as-deposited nc-Si dots were nitrided at 780°C in NH3 ambient. The role of the nitridation of nc-Si dots for improving performance of nc-Si NVM was investigated. First of all, enlarged memory windows have been observed from nitrided nc-Si NVM compared with that of un-nitrided nc-Si NVM because of the reduction of the surface defect states of nc-Si. Secondly, a faster program speed is achieved because the effective gate bias is increased in nitrided nc-Si NVM. Furthermore, the Si nitride cover layer also acts as a potential barrier which enhanced the memory retention time. The mechanism of improving performance of nitrided nc-Si NVM has been discussed.

Growth of aligned wurtzite GaN nanorods on Si(111): Role of Silicon nitride intermediate layer

ABSTRACT:We present here a report on a role of initial nitridation of Si(111) surface on GaN nanorod growth. High quality wurtzite GaN nanorods are grown by Molecular Beam Epitaxy on bare Si(111)-7x7, crystalline and amorphous silicon nitride at 750oC, under nitrogen rich conditions. Using in-situ reflection high energy electron diffraction and ex-situ X-ray photoelectron spectroscopy, field emission scanning electron microscopy and photoluminescence, the structural and chemical properties are monitored. In the first part of the study, we have optimized the conditions of the N2* RF plasma, for formation of crystalline and amorphous silicon nitride on Si(111)-7x7 surface. While in the second part, GaN nanorods are grown on clean and these modified Si(111) substrates. Anisotropic spots are observed by RHEED for GaN grown on clean Si and on the amorphous silicon nitride, while circular, sharp and intense RHEED spots have been observed for GaN grown on crystalline Si3N4. FESEM results show nanorod growth in all the three different conditions. However, GaN nanorods grown on crystalline Si3N4 surface are observed to be self aligned and oriented along &lt;0001&gt; direction, while those grown on amorphous silicon nitride and bare Si(111) surfaces show great disorder increasing, respectively. Overall, the results clearly demonstrate that high quality of dense and self aligned c-oriented GaN nanorods can be formed on Si(111) surface by modifying it by appropriate nitridation.

Effect of sintering conditions and heat treatment on the properties, microstructure and machining performance of α-β-SiAlON ceramics

Abstract The properties of SiAlON ceramics are strongly affected by the composition and structure of the intergranular phase, which are controlled by dopants, sintering conditions and starting silicon nitride (Si 3 N 4 ) powder characteristics. In this study, 25α:75β SiAlON compositions were designed with different molar ratios of Y:Sm:Ca (9:0.5:0.5 and 3:6:1). The effects of cation ratios, different cooling profiles (50 °C/min and 5 °C/min) and further heat treatment under different conditions (at 1600 °C for 2, 4 and 6 h) on the final phase composition, the type of the intergranular phase (amorphous or crystalline) formation, the resulting microstructures and the machining performance were studied. It is found that slow cooling and heat treatment have a great influence on crystallisation behaviour and in turn the crystallisation enhance the machining performance of SiAlON materials in cutting tool applications.

Physical properties of thermally evaporated silicon films nitrided at different rf plasma-processing time

Nitrided surfaces and composition gradients in thin films exhibit interesting mechanical, electrical, and optical properties. Therefore, amorphous hydrogen-free silicon (a-Si) thin films were deposited by electron beam evaporation and subsequently nitrided by an inductively coupled rf plasma. The effects of successive plasma-processing cyclic time on structural and optical properties as well as electrical resistivity were examined by different characterization techniques. It was found that the rf plasma treatment has a massive effect on the physical properties of the Si films. The Si thin films were transformed gradually into nitrides compound and the amount of nitrogen in the film increased with increasing the rf plasma-processing time. The Si nitrided films showed structural, optical, and electrical properties dependent on the plasma-nitriding time. Increasing the rf plasma-processing time reduced the thickness, increased transmittance, increased resistivity, and decreased the reflectance of the nitrided Si films. The electrical resistivity increased to about nine orders of magnitude when the film was nitrided at a plasma-processing time of 25 min. The optical band gap increased from 2.42 to 3.52 eV with increasing the plasma-processing time from 10 to 35 min. The decrease in the refractive index with the increase in the plasma-processing time is attributed to the possible change in the bucking density as well as to the increase in the band gap.

Durability characteristics of nano-GFRP composite reinforcing bars for concrete structures in moist and alkaline environments

In this study, nano glass fibre-reinforced polymer (nano-GFRP) composite reinforcing bars (rebar) for concrete structures were fabricated, and their performance during prolonged exposure to water and alkaline solutions was evaluated. Nano-GFRP rebar was prepared using the pultrusion method by adding nanomaterials to vinyl ester resin. The nanomaterials, including silica (SiO 2), alumina (Al 2O 3), and silicon nitride (Si 3N 4), were added to vinyl ester resin at 1, 3, and 5 wt.%. After exposure to water and alkaline solutions for 50 and 115 days, tensile strength tests were carried out, and the moisture diffusion coefficient was determined and compared with that of general GFRP rebar. The results indicated that the tensile residual strengths of nano-GFRP rebar and general GFRP rebar were almost the same after exposure to water, whereas the tensile residual strength of nano-GFRP rebar was higher than that of general GFRP rebar after exposure to alkaline solution. The moisture diffusion coefficient of the alumina and silicon nitride samples increased slightly after exposure to alkaline solution, but the silica sample had a higher moisture diffusion coefficient; however, the moisture diffusion coefficients of all nano-GFRP rebar samples were comparable to that of general GFRP rebar.

Behavior of N atoms after thermal nitridation of Si1 − xGex surface

Behavior of N atoms after thermal nitridation of Si1−xGex (100) surface in NH3 atmosphere at 400°C was investigated. X-ray photoelectron spectroscopy (XPS) results show that N atomic amount after nitridation tends to increase with increasing Ge fraction, and amount of N atoms bonded with Ge atoms decreases by heat treatment in H2 at 400°C. For nitrided Si0.3Ge0.7(100), the bonding between N and Si atoms forms Si3N4 structure whose amount is larger than that for nitrided Si(100). Angle-resolved XPS measurements show that there are N atoms not only at the outermost surface but also beneath surface especially in a deeper region around a few atomic layers for the nitrided Si(100), Si0.3Ge0.7(100) and Ge(100). From these results, it is suggested that penetration of N atoms through around a few atomic layers for Si, Si0.3Ge0.7 and Ge occurs during nitridation, and the N atoms for the nitrided Si0.3Ge0.7(100) dominantly form a Si3N4 structure which stably remains even during heat treatment in H2 at 400°C.

Dielectrically stabilized electrowetting on AF1600/Si 3N 4/TiO 2 dielectric composite film

In this paper, we propose a dielectrically stabilized and reversible electrowetting-on-dielectric (EWOD) platform based on a multi-layered insulator composed of amorphous fluoropolymer (AF1600), silicon nitride (Si 3N 4), and titanium dioxide (TiO 2). Although TiO 2 can reduce the electrowetting voltage owing to its high relative permittivity, κ, an EWOD platform composed of only TiO 2 is vulnerable to current leakage. The proposed AF1600/Si 3N 4/TiO 2 (20 nm/20 nm/20 nm) EWOD platform exhibited enhanced dielectric strength as well as a low contact angle hysteresis within 2° of the droplet. Because a Si 3N 4 film has excellent dielectric strength as compared to AF1600 and TiO 2 films, it can safeguard the EWOD platform from both current leakage and dielectric breakdown. The electrowetting capability of the AF1600/Si 3N 4/TiO 2 EWOD platform was improved by means of a thin fluoropolymer film with a thickness of less than 20 nm.

Modeling and simulation of long-wave infrared InAs/GaSb strained layer superlattice photodiodes with different passivants

Current–voltage characteristics of long-wave infrared (LWIR) InAs/GaSb strained layer superlattice photodiodes (cut-off wavelength ∼10 μm), passivated with different surface passivants, have been modeled and simulated using ATLAS software from SILVACO. The simulated results are fitted to previous experimental results obtained on unpassivated devices and those passivated by silicon-dioxide (SiO 2), silicon nitride (Si x N y ) and zinc sulfide (ZnS). Surface parameters in terms of surface recombination velocity, shunt resistance and interface trap density are extracted for different passivants. The performance of silicon-dioxide passivated diode is solely dominated by a shunt leakage path with a shunt resistance value of 0.56 Ω-cm 2. Extracted electron and hole surface recombination velocities have values of 10 5 cm/s and 10 7 cm/s for unpassivated, 10 3 cm/s and 10 5 cm/s for Si x N y passivated and 10 2 cm/s and 10 3 cm/s for ZnS passivated devices. Interface trap density follows a similar trend with values of 10 15 cm −2, 8.5 × 10 14 cm −2 and 10 10 cm −2 for unpassivated, Si x N y passivated and ZnS passivated devices respectively. The suitability and limitations of the simulation tool are discussed.

A Mechanical Nanomembrane Detector for Time-of-Flight Mass Spectrometry

We describe here a new principle for ion detection in time-of-flight (TOF) mass spectrometry in which an impinging ion packet excites mechanical vibrations in a silicon nitride (Si(3)N(4)) nanomembrane. The nanomembrane oscillations are detected by means of time-varying field emission of electrons from the mechanically oscillating nanomembrane. Ion detection is demonstrated in the MALDI-TOF analysis of proteins varying in mass from 5729 (insulin) to 150,000 (Immunoglobulin G) daltons. The detector response agrees well with the predictions of a thermomechanical model in which the impinging ion packet causes a nonuniform temperature distribution in the nanomembrane, exciting both fundamental and higher order oscillations.

Equilibrium and metastable phase transitions in silicon nitride at high pressure: A first-principles and experimental study

We have combined first-principles calculations and high-pressure experiments to study pressure-induced phase transitions in silicon nitride (Si${}_{3}$N${}_{4}$). Within the quasi-harmonic approximation, we predict that the $\ensuremath{\alpha}$ phase is always metastable relative to the $\ensuremath{\beta}$ phase over a wide pressure-temperature range. Our lattice vibration calculations indicate that there are two significant and competing phonon-softening mechanisms in the $\ensuremath{\beta}$-Si${}_{3}$N${}_{4}$, while phonon softening in the $\ensuremath{\alpha}$-Si${}_{3}$N${}_{4}$ is rather moderate. When the previously observed equilibrium high-pressure and high-temperature $\ensuremath{\beta}$ $\ensuremath{\rightarrow}$ $\ensuremath{\gamma}$ transition is bypassed at room temperature (RT) due to kinetic reasons, the $\ensuremath{\beta}$ phase is predicted to undergo a first-order structural transformation to a denser $P\overline{6}$ phase above 39 GPa. The estimated enthalpy barrier height is less than 70 meV$/$atom, which suggests that the transition is kinetically possible around RT. This predicted new high-pressure metastable phase should be classified as a ``postphenacite'' phase. Our high-pressure x-ray diffraction experiment confirms this predicted RT phase transition around 34 GPa. No similar RT phase transition is predicted for $\ensuremath{\alpha}$-Si${}_{3}$N${}_{4}$. Furthermore, we discuss the differences in the pressure dependencies of phonon modes among the $\ensuremath{\alpha}$, $\ensuremath{\beta}$, and $\ensuremath{\gamma}$ phases and the consequences on their thermal properties. We attribute the phonon modes with negative Gr\"uneisen ratios in the $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ phases as the cause of the predicted negative thermal expansion coefficients (TECs) at low temperatures in these two phases, and predict no negative TECs in the $\ensuremath{\gamma}$ phase.

Transient thermoelastic waves in an anisotropic hollow cylinder due to localized heating

This paper presents a theoretical study of transient ultrasonic guided waves generated by concentrated heating of the outer surface of an infinite anisotropic hollow circular cylinder. Generalized thermoelastic theory proposed by Lord and Shulman is adopted to model the dynamic thermoelastic behavior of the cylinder. The concentrated heat source model used is to represent heating due to a pulsed laser beam, which is focused on the outer surface of the cylinder. A semi-analytical finite element (SAFE) method is employed to evaluate guided wave modes in the cylinder. Using integral transform techniques, the modal wave forms are obtained in frequency and wave number domains. Time histories of the propagating modes are then calculated by applying inverse Fourier transformation in the time domain. Numerical results showing the dispersion curves for the group velocities of the propagating modes and transient radial displacements are presented. For this purpose it is assumed that the cylinder is made of transversely isotropic silicon nitride (Si 3N 4). Attention is focused on the propagation characteristics of longitudinal and flexural modes separately.

Blue–green to near-IR switching electroluminescence from Si-rich silicon oxide/nitride bilayer structures

Blue-green to near-IR switching electroluminescence (EL) has been achieved in a metal-oxide-semiconductor light emitting device, where the dielectric has been replaced by a Si-rich silicon oxide/nitride bilayer structure. To form Si nanostructures, the layers were implanted with Si ions at high energy, resulting in a Si excess of 19%, and subsequently annealed at 1000 °C. Transmission electron microscopy and EL studies allowed ascribing the blue-green emission to the Si nitride related defects and the near-IR band with the emission of the Si-nanoclusters embedded into the SiO(2) layer. Charge transport analysis is reported and allows for identifying the origin of this two-wavelength switching effect.