Effect of Ni on the Formation of ${hbox {Cu}}_{6}{hbox {Sn}}_{5}$ and ${hbox {Cu}}_{3}{hbox {Sn}}$ Intermetallics

In this paper, the effect of Ni on the formation of Cu₆Sn₅ and Cu₃Sn intermetallics between tin and (Cu,Ni) substrates has been studied by making use of the thermodynamic assessment of the Sn-Cu-Ni system. The driving forces for the diffusion of the elements in the intermetallic layers were calculated as a function of Ni content. Assuming constant mobilities of component atoms, the results suggest that the diffusion fluxes of all the components in the (Cu, Ni)₆Sn₅ layer increase with increasing content of dissolved Ni, while the Cu and Sn fluxes in the (Cu, Ni)₃Sn layer decrease. Therefore, the dissolution of Ni retards the growth of (Cu, Ni)₃Sn. When the Ni content of the (Cu,Ni) substrate is high enough, the intermetallic compound growth in the reaction zones is dominated by (Cu, Ni)₆Sn₅, and the (Cu, Ni)₃Sn layer disappears gradually. The small thickness of (Cu, Ni)₃Sn is associated with large difference between Sn and Cu fluxes in (Cu, Ni)₃Sn that encourages also the "Kirk-endall void" formation. In addition, the calculated driving forces suggest that the growth rate of (Cu, Ni)₆Sn₅ should further increase if (Cu, Ni)₃Sn disappears, resulting in an unusually thick (Cu, Ni)₆Sn₅ layer. The results of thermodynamic calculations supplemented with diffusion kinetic considerations are in good agreements with recent experimental observations.     

Improved Electrical Properties of Ge p-MOSFET With $ hbox{HfO}_{2}$ Gate Dielectric by Using $hbox{TaO}_{x} hbox{N}_{y}$ Interlayer

The electrical characteristics of germanium p-metal-oxide-semiconductor (p-MOS) capacitor and p-MOS field-effect transistor (FET) with a stack gate dielectric of HfO₂/TaOxNy are investigated. Experimental results show that MOS devices exhibit much lower gate leakage current than MOS devices with only HfO₂ as gate dielectric, good interface properties, good transistor characteristics, and about 1.7-fold hole-mobility enhancement as compared with conventional Si p-MOSFETs. These demonstrate that forming an ultrathin passivation layer of TaOxNy on germanium surface prior to deposition of high-k dielectrics can effectively suppress the growth of unstable GeOx, thus reducing interface states and increasing carrier mobility in the inversion channel of Ge-based transistors.     

Improvement of On–Off-Current Ratio in $ hbox{TiO}_{rm x}$ Active-Channel TFTs Using $hbox{N}_{2} hbox{O}$ Plasma Treatment

Without sacrificing the on-current in the transfer characteristics, we have successfully reduced the off-current part by the optimal $hbox{N}_{2}hbox{O}$ plasma treatment to improve the on–off-current ratio in n-type titanium oxide $( hbox{TiO}_{rm x})$ active-channel thin-film transistors. While the high-power (275 W) $hbox{N}_{2}hbox{O}$ plasma treatment oxidizes the whole $hbox{TiO}_{rm x}$ channel and results in the reduction of both on- and off-current, the optimized low-power (150 W) process makes the selective oxidation of the top portion in the channel and reduces only the off-current significantly. Increase in on–off ratio by almost five orders of magnitude is achieved without change in on-current by using the presented method.      

Fabrication of Self-Aligned Enhancement-Mode $ hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ MOSFETs With $ hbox{TaN/HfO}_{2}hbox{/AlN}$ Gate Stack

In this letter, we report the fabrication and characterization of self-aligned inversion-type enhancement-mode In_0.53Ga_0.47As metal-oxide-semiconductor field-effect transistors (MOSFETs). The In_0.53Ga_0.47As surface was passivated by atomic layer deposition of a 2.5-nm-thick AIN interfacial layer. In_0.53Ga_0.47As MOS capacitors showed an excellent frequency dispersion behavior. A maximum drive current of 18.5 muA/mum was obtained at a gate overdrive of 2 V for a MOSFET device with a gate length of 20 mum. An I_on/_off ratio of 104, a positive threshold voltage of 0.15 V, and a subthreshold slope of ~165 mV/dec were extracted from the transfer characteristics. The interface-trap density is estimated to be ~7-8 times 10¹² cm^-2 ldr eV^-1 from the subthreshold characteristics of the MOSFET.     

Endurance Reliability of Multilevel-Cell Flash Memory Using a $ hbox{ZrO}_{2}/hbox{Si}_{3}hbox{N}_{4}$ Dual Charge Storage Layer

The mechanisms of programming/erasing (P/E) and endurance degradation have been investigated for multilevel-cell (MLC) Flash memories using a $hbox{Si}_{3}hbox{N}_{4}$ (NROM) or a $hbox{ZrO}_{2}/hbox{Si}_{3}hbox{N}_{4}$ dual charge storage layer (DCSL). Threshold-voltage $(V_{rm th})$ -level disturbance is found to be the major endurance degradation factor of NROM-type MLCs, whereas separated charge storage and step-up potential wells give rise to a superior $V_{rm th}$ -level controllability for DCSL MLCs. The programmed $V_{rm th}$ levels of DCSL MLCs are controlled by the spatial charge distribution, as well as the charge storage capacity of each storage layer, rather than the charge injection. As a result, DCSL MLCs show negligible $V_{rm th}$-level offsets ($ ≪ $ 0.2 V) that are maintained throughout the $hbox{10}^{5}$ P/E cycles, demonstrating significantly improved endurance reliability compared to NROM-type MLCs.      

Structure Effects on Resistive Switching of $ hbox{Al/TiO}_{x}/hbox{Al}$ Devices for RRAM Applications

Resistive switching characteristics are investigated for Al/TiO_x/Al devices, particularly for the structural effects in crossbar and via-hole-type devices. The via-hole structure shows more reliable switching characteristics than the crossbar structure, owing to the elimination of possible edge effects. The asymmetric switching behavior is analyzed with top Al/TiO_x, and bottom Al/TiO_x interfaces. A trap-controlled space-charge- limited-current model is proposed as a possible switching mechanism, and it is verified that switching mainly occurs on the top electrode/TiO_x, interface side.     

Frequency-Independent Scattering From a Flat Strip With ${rm TE}_{z}$-Polarized Fields

The surface current for scattering from a PEC strip naturally decomposes into three slowly varying functions modulating rapidly oscillating phase factors. We exploit this structure to derive a numerical solution that is error-controllable and exhibits a bounded error over the full range of frequencies. Frequency independence is obtained by expanding the current in terms of slowly-varying amplitude functions, stretching coordinates in the boundary layer, and employing a frequency-independent quadrature rule. Though the total current solution is always well-defined, unique, minimally-varying amplitude functions may also be found by using the minimum norm concept.     

Analysis of the ${rm TE}$ -Pass or ${rm TM}$-Pass Metal-Clad Polarizer With a Resonant Buffer Layer

A metal-clad optical polarizer with a resonant buffer layer has been investigated by the finite-element method in this paper. Important waveguide design parameters, such as the refractive index, thickness, interaction length, fabrication tolerance, and band-stop characteristics, have been analyzed in detail. Mode coupling within the polarizer and the losses due to coupling between the polarizer and the input and output waveguides are considered using the normal mode analysis. The loss behaviors of and modes are explained and the roles of the resonant buffer layer are interpreted. By using ultralow index layers, resonance, as well as its phase-matching conditions and excellent performance, has also been presented and discussed for this structure for the first time. Simulations show that high performance can be achieved in a wide range of the cladding thicknesses (ges 2 mum) and interaction length for both TE-pass and TM-pass polarizers. With optimized parameters under 3-mm length, it is possible to obtain a broadband TE-pass polarizer with an extinction ratio of more than 40 dB and insertion loss below 0.2 dB over 200 nm, and a TM-pass polarizer with an extinction ratio of more than 30 dB and insertion loss below 0.4 dB over 28 nm.     

Numerical Study of Flicker Noise in p-Type $ hbox{Si}_{0.7}hbox{Ge}_{0.3}/hbox{Si}$ Heterostructure MOSFETs

Device-level simulation capabilities have been developed to investigate low-frequency noise behavior in p-type Si_0.7Ge_0.3/Si heterostructure MOS (SiGe p-HMOS) transistors. The numerical model is based on the impedance field method; it accounts for a trap-induced carrier number fluctuation, a layer-dependent correlated mobility fluctuation, and a Hooge mobility fluctuation in the buried and parasitic surface channels, respectively. Simulations based on such models have been conducted for SiGe p-HMOS transistors, and the results have been carefully correlated with experimental data. Quantitative agreement has been obtained in terms of the noise level dependence on gate biases, drain currents, and body biases, revealing the important role of the dual channels in the low-frequency noise behavior of SiGe p-HMOS devices.     

Schottky Barrier Height of Erbium Silicide on $ hbox{Si}_{1 - x}hbox{C}_{x}$

In this letter, the Schottky barrier height of erbium silicide contacts formed on $hbox{Si}_{1 - x}hbox{C}_{x}$ alloys was measured. The alloys were pseudomorphically grown on Si wafers with 0% to 1.2% C occupying the substitutional sites. Schottky barrier diodes were fabricated with an ideality factor of 1.13 or less. The hole barrier height was found to be 0.73 eV independent of the C concentration. This suggests that the electron barrier height should decrease with increasing C concentration due to the reduction in the semiconductor bandgap. For 1.2% C, the electron barrier is estimated to be 0.29 eV.      

Improved Sellmeier Equations and Phase-Matching Characteristics in Deep-Ultraviolet Region of ${hbox {KBe}}_{2}{hbox {BO}}_{3}{hbox {F}}_{2}$ Crystal

A 3.0-mm-thick KBe ₂BO₃F₂ (KBBF) crystal has been successfully grown and used to fabricate a right angle prism. Its refractive indices were accurately measured with a prism technique at seven wavelengths from 0.4047 to 0.6562 mum . Its phase-matching characteristics in deep-ultraviolet (UV) region were investigated. Using the measured indices and phase-matching angles from deep-UV to near infrared, improved Sellmeier equations for KBBF have been derived.     

High Density and Low Leakage Current in $ hbox{TiO}_{2}$ MIM Capacitors Processed at 300 $^{circ} hbox{C}$

We report Ir/TiO₂/TaN metal-insulator-metal capacitors processed at only 300degC, which show a capacitance density of 28 fF/mum² and a leakage current of 3 times 10^-8 (25degC) or 6 times 10^-7 (125degC) A/cm² at -1 V. This performance is due to the combined effects of 300degC nanocrystallized high-kappa TiO₂, a high conduction band offset, and high work-function upper electrode. These devices show potential for integration in future very-large-scale-integration technologies.     

Gate Influence on the Layout Sensitivity of $ hbox{Si}_{1 - x}hbox{Ge}_{x} hbox{S/D}$ and $hbox{Si}_{1 - y}hbox{C}_{y} hbox{S/D}$ Transistors Including an Analytical Model

We present a simulation study on the effect of the gate module on the channel stress in Si_1-xGe_x and Si_1-yC_y S/D MOS transistors. Stiff gate materials, such as titanium nitride, lead to a decreased channel stress, while a replacement-gate scheme allows the increase of the effectiveness of the Si_1-xGe_x and Si_1-yC_y S/D techniques significantly, independent of the gate material used. The drawback of using a replacement gate is that the channel stress becomes more sensitive to layout variations. In terms of effect on Si_1-xGe_x/Si_1-yC_y S/D stress generation, using a thin metal gate capped by polysilicon is similar to a full metal gate if the thin metal gate thickness exceeds 10 nm. Even metal gates as thin as 1 nm have a clear influence on the stress generation by Si_1-xGe_x/Si_1-yC_y S/D. Removing and redepositing the polysilicon layer while leaving the underlying metal gate unchanged increases the stress, although not to the same extent as for complete gate removal. A simple analytical model that estimates the stress in nested short-channel Si_1-xGe_x and Si_1-yC_y S/D transistors is presented. This model includes the effect of germanium/carbon concentration, active-area length, as well as the effect of gate length and the Young's modulus of the gate. Good qualitative agreement with 2-D finite element modeling is demonstrated.     

BST-Varactor Tunable Dual-Mode Filter Using Variable ${Z}_{C}$ Transmission Line

Ferroelectric materials like barium-strontium-titanate (BST) have become attractive for microwave tunable circuit applications. This letter presents an investigation of BST-varactor tunable dual-mode filter using variable characteristic impedance or Z_C transmission line. The interdigital BST varactors are fabricated and modeled, which are then deployed to realize a bandpass filter with tunable bandwidth capability. The use of tunable impedance line provides additional flexibilities in the design of microwave tunable circuits. A tunable bandpass filter of this type with a center frequency of 1.8 GHz and a bandwidth tuning ratio of 1.15:1 is demonstrated experimentally.     

A Comparative NBTI Study of $hbox{HfO}_{2}$, $hbox{HfSiO}_{x}$, and SiON p-MOSFETs Using UF-OTF $I_{rm DLIN}$ Technique

The time, temperature, and oxide-field dependence of negative-bias temperature instability is studied in $hbox{HfO}_{2}/hbox{TiN}$, $ hbox{HfSiO}_{x}/hbox{TiN}$, and SiON/poly-Si p-MOSFETs using ultrafast on-the-fly $I_{rm DLIN}$ technique capable of providing measured degradation from very short (approximately microseconds) to long stress time. Similar to rapid thermal nitrided oxide (RTNO) SiON, $hbox{HfO}_{2}$ devices show very high temperature-independent degradation at short (submilliseconds) stress time, not observed for plasma nitrided oxide (PNO) SiON and $hbox{HfSiO}_{x}$ devices. $hbox{HfSiO}_{x}$ shows lower overall degradation, higher long-time power-law exponent, field acceleration, and temperature activation as compared to $hbox{HfO}_{2}$, which are similar to the differences between PNO and RTNO SiON devices, respectively. The difference between $ hbox{HfSiO}_{x}$ and $hbox{HfO}_{2}$ can be attributed to differences in N density in the $hbox{SiO}_{2}$ IL of these devices.      

Comparative Study of the Low-Frequency-Noise Behaviors in a-IGZO Thin-Film Transistors With $hbox{Al}_{2}hbox{O}_{3}$ and $hbox{Al}_{2}hbox{O}_{3}/hbox{SiN}_{x}$ Gate Dielectrics

A comparative study is made of the low-frequency noise (LFN) in amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) with $hbox{Al}_{2}hbox{O}_{3}$ and $hbox{Al}_{2}hbox{O}_{3}/hbox{SiN}_{x}$ gate dielectrics. The LFN is proportional to $hbox{1}/f^{gamma}$, with $gamma sim hbox{1}$ for both devices, but the normalized noise for the $hbox{Al}_{2}hbox{O}_{3}/hbox{SiN}_{x}$ device is two to three orders of magnitude lower than that for the $hbox{Al}_{2} hbox{O}_{3}$ device. The mobility fluctuation is the dominant LFN mechanism in both devices, but the noise from the source/drain contacts becomes comparable to the intrinsic channel noise as the gate overdrive voltage increases in $hbox{Al}_{2}hbox{O}_{3}/hbox{SiN}_{x}$ devices. The $hbox{SiN}_{x}$ interfacial layer is considered to be very effective in reducing LFN by suppressing the remote phonon scattering from the $hbox{Al}_{2}hbox{O}_{3}$ dielectric. Hooge's parameter is extracted to $sim !!hbox{6.0} times hbox{10}^{-3}$ in $hbox{Al}_{2}hbox{O}_{3}/hbox{SiN}_{x}$ devices.      

Actively $Q$ -switched and Mode-Locked Diode-Pumped ${hbox {Nd:GdVO}}_{4}{hbox {--KTP}}$ Laser

By using a comparative simple configuration and a short cavity length, a diode-pumped actively Q -switched and mode-locked intracavity frequency doubled Nd:GdVO₄-KTP green laser with the modulation depth 100% was realized, from which the great average output power, the high efficiency were obtained and the mode-locked pulse inside the Q -switched pulse has a repetition rate of 476 MHz. Using the hyperbolic secant function methods and by considering the Gaussian distribution of the intracavity photon density, the influences of continuous pump rate, the upper state lifetime of the active medium and the turnoff time of the acousto-optic Q -switch, we proposed a developed rate equation model for actively Q -switched and mode-locked green lasers. With this developed model, the theoretical calculations are in good agreement with the experimental results and the width of the mode-locked green pulse is estimated to be about 185 ps.     

Electrical Characteristics of Passivated Pseudomorphic HEMTs With $hbox{P}_{hbox{2}}hbox{S}_{hbox{5}}/(hbox{NH}_{hbox{4}})_{hbox{2}}hbox{S}_{hbox{X}}$ Pretreatment

This paper elucidates the dc, pulse I-V, microwave, flicker noise, and power properties of AlGaAs/InGaAs pseudomorphic high electron mobility transistors (pHEMTs) after various ex situ sulfur pretreatments. The pHEMTs were pretreated with NH₄OH, (NH₄)₂S_X, and P₂S₅/(NH₄)₂S_X solutions before SiO₂ passivation to reduce the GaAs native oxide-related surface states. Stable phosphorus oxides and sulfur bound to the Ga and As species can be efficiently obtained using P₂S₅/(NH₄)₂S_X pretreatment; therefore, the leakage current in pHEMT was reduced following this process. Atomic force microscopy measurements indicated that the phosphorus oxides formed by P₂S₅/(NH₄)₂S_X treatment also provided a better surface roughness than obtained following traditional (NH₄)2S_X-only pretreatment, reducing mobility degradation after sulfur pretreatment. Based on the dc and 1 mus pulse I-V measurement results, P₂S₅/(NH₄)₂S_X-treated pHEMT exhibited very similar I_ds trends, especially at high currents; however, NH₄OH, (NH₄)₂S_X treatments clearly reduced the current upon pulse measurement because of the presence of surface traps. Hence, this novel pretreatment method has great potential for highly linear microwave power transistor applications.