Process optimization and PFC emission reduction using a c-C/sub 4/F/sub 8/ chamber cleaning process on a novellus concept 1 dielectric PECVD tool

While the new generation of chemical vapor deposition (CVD) tools adapts NF/sub 3/ as a chamber clean gas to reduce perfluorocompound (PFC) reductions, process optimization (C/sub 2/F/sub 6/) and alternative C/sub x/F/sub y/ clean chemistries are options for the installed-base tools. From a previous study comparing the various C/sub x/F/sub y/ chamber clean chemistries, we further conducted a production test in a 150-mm wafer fabrication facility comparing the best alternative C/sub x/F/sub y/ clean chemistry (C/sub 4/F/sub 8/ clean) with an optimized C/sub 2/F/sub 6/ clean process on a Novellus Concept 1 Dielectric tool running TEOS-based SiO/sub 2/ CVD. Gas flow rates, chamber pressure, and oxygen volume percentages were studied as variables to develop an optimal c-C/sub 4/F/sub 8/ process recipe for maintaining or improving cleaning efficiency while reducing gas consumption and PFC emissions compared to the optimized C/sub 2/F/sub 6/ process. After the initial experimental matrix was completed, several single-variable experiments were run to fine tune the recipe. Based on the data analysis and the model results from the design of experiment, two optimal C/sub 4/F/sub 8/ cleaning processes were identified. Both processes significantly lowered gas consumption and PFC emissions. Marathon process testing showed no adverse impact on film properties or device yield.     

Thermal CVD of homoepitaxial diamond using CF/sub 4/ and F/sub 2/

For the first time, diamond has been grown using low-pressure thermal CVD. No additional excitation such as plasmas or filaments was used. The authors report the homoepitaxial growth of diamond on type II-A diamond     

Spectroscopic analysis and diode-pumped laser results of Nd:BaY/sub 2/F/sub 8/

Single crystals of monoclinic BaY/sub 2/F/sub 8/, doped with different Nd/sup 3+/ concentrations, were successfully grown by means of the Czochralski method. Here, we present a polarized infrared (IR) spectroscopic investigation and diode-pumped continuous-wave laser results in the 1 /spl mu/m wavelength region. Moreover for the first time 1.3 /spl mu/m laser emission has been characterized. Q-switching results in the 1-/spl mu/m region are also presented.     

Geometric Reed-Solomon codes of length 64 and 65 over F/sub 8/

We determine the actual parameters for a class of one-point codes of length 64 and 65 over F/sub 8/ defined by Hansen and Stichtenoth (1990). Several codes have a minimum distance that exceeds the Feng-Rao bound. The codes with parameters [64,5,51], [64,10,42], [64,11,42], [64,12,40], [65,5,52], [65,10,43], [65,11,42], [65,12,41], and [65,13,40] are better than any known code.     

Efficient amplification using the /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica fiber

Amplification characteristics of the three-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica glass fiber are investigated under strong signal saturation and high pump power (150 mW). Aluminum codoped Nd-silica fibers exhibit strong superfluorescent behavior in the four-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 11/2/ transition which limits the optical conversion efficiency into the three-level transition. Ge-doped silica fibers do not exhibit this limitation and can efficiently amplify in the three-level transition with current laser-diode pump technology.     

A 4-kB 500-MHz 4-T CMOS SRAM using low-V/sub THN/ bitline drivers and high-V/sub THP/ latches

The design and physical implementation of a prototypical 500-MHz CMOS 4-T SRAM is presented in this work. The latch of the proposed SRAM cell is realized by a pair of cross coupled high-V/sub THP/ pMOS transistors, while the bitline drivers are realized by a pair of low-V/sub THN/ nMOS transistors. The wordline voltage compensation circuit and bitline boosting circuit, then, are neither needed to enhance the data retention of memory cells. Built-in self-refreshing paths make the data retention possible without the appearance of any external refreshing mechanism. The advantages of dual threshold voltage transistors can be used to reduce the access time, and maintain data retention at the same time. Besides, a new design of cascaded noise-immune address transition detector is also included to filter out the unwanted chip select glitches when the SRAM is asynchronously operated.     

Pulsed laser action in Tm,Ho:LuLiF/sub 4/ and Tm,Ho:YLiF/sub 4/ crystals using a novel quasi-end-pumping technique

A number of good quality thulium and holmium-codoped LuLiF/sub 4/ and YLiF/sub 4/ single crystals were successfully grown by the Czochralski crystal growth method under a CF/sub 4/ atmosphere. Using a novel diode-pumped, quasi-end-pump scheme incorporating two lens ducts, pulsed laser action is achieved in 5%Tm, 0.5% Ho:LuLiF/sub 4/ and 5%Tm, 0.5% Ho:YLiF/sub 4/ crystals, at various pulse repetition frequencies and temperatures. At 10 Hz and at an operating temperature of 273 K, slope efficiencies (optical to optical efficiencies) with respect to the incident pump energies of 12.9% (9.2%) and 7.4% (5.2%) were demonstrated in the grown Tm, Ho:LuLiF/sub 4/ and Tm, Ho:YLiF/sub 4/ crystals, respectively. Free running laser output energies in excess of 30 mJ (LuLiF/sub 4/) and 17 mJ (YLF) were measured.     

Fabrication and characterization of high-quality uniform and apodized Si/sub 3/N/sub 4/ waveguide gratings using laser interference lithography

A method is presented for fabricating high-quality ridge waveguide gratings by combining conventional mask lithography with laser interference lithography. The method, which allows for apodization functions modulating both amplitude and phase of the grating is demonstrated by fabricating a grating that is chirped by width-variation of the grated ridge waveguide. The structure was optically characterized using both an end-fire and an infrared camera setup to measure the transmission and to map and quantify the power scattered out of the grating, respectively. For a uniform grating, we found a Q value of /spl sim/8000 for the resonance peak near the lower wavelength band edge, which was almost completely suppressed after apodization.     

Optical pumping of CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers by means of a new pulsed CO/sub 2/ laser: characterization of new far-infrared laser emissions

We have reinvestigated CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers as sources of far-infrared laser radiation using the optical pumping technique. A new waveguide pulsed CO/sub 2/ laser was used, that delivers high peak powers also in the 10-HP CO/sub 2/ band and has allowed us to observe 19 new far-infrared emissions from CHD/sub 2/OH and 8 new far-infrared emissions from CH/sub 2/DOH. Each of them is characterized in wavelength, pump offset from the center of the exciting CO/sub 2/ line, relative polarization, optimum operating pressure and intensity.     

15-nm base type-II InP/GaAsSb/InP DHBTs with F/sub T/=384 GHz and a 6-V BV/sub CEO/

Type-II InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with a 15-nm base were fabricated by contact lithography: 0.73/spl times/11 /spl mu/m/sup 2/ emitter devices feature f/sub T/=384GHz (f/sub MAX/=262GHz) and BV/sub CEO/=6V. This is the highest f/sub T/ ever reported for InP/GaAsSb DHBTs, and an "all-technology" record f/sub T//spl times/BV/sub CEO/ product of 2304 GHz/spl middot/V. This result is credited to the favorable scaling of InP/GaAsSb/InP DHBT breakdown voltages (BV/sub CEO/) in thin collector structures.     

Remote plasma etching of titanium nitride using NF3/argon and chlorine mixtures for chamber clean applications

To avoid plasma induced erosion of chamber hardware, the application of remote plasma sources to activate the etch gases was introduced. We present results on the etch behaviour of titanium nitride (TiN) using mixtures of NF₃, Cl₂ and argon. The gas mixture was excited in a remote plasma source and then routed through a reaction chamber to study the etch behaviour of TiN samples which simulate the situation at the chamber walls. The dependency of the TiN etch rate on temperature, gas flow, composition and pressure was examined. While the temperature (studied in the range 25-300 °C) turned out to be the most sensitive parameter, the general etch rate was mainly dependent on the availability of atomic fluorine. Etch products and NF₃/Cl₂ dissociation have been monitored by quadrupole mass spectrometry and infrared spectroscopy. While NF₃ showed a high decomposition up to 96%, chlorine decomposition was not observed. However the addition of chlorine increased the etch rates up to 260% in the low pressure/low temperature regime. Surface effects of chlorine addition are indicated by X-Ray Photoelectron Spectrometry and REM surface analysis.     

Inductively coupled plasma reactive ion etching of sapphire using C2F6- and NF3-based gas mixtures

Inductively coupled plasma reactive ion etching (ICP-RIE) of sapphire wafers using C₂F₆- and NF₃-based plasma was investigated as a function of ICP power, bias power, pressure, and plasma chemistry. Etch rate of about 150 nm/min in the case of C₂F₆ plasma and about 260 nm/min in the case of NF₃ plasma was obtained at the optimum condition, with anisotropic profiles and smooth surfaces. No chamber corrosion was observed after the etching, indicating that ICP-RIE using the fluorine-related gases is a promising technique for sapphire patterning.     

Characteristics and mechanism of tunable work function gate electrodes using a bilayer metal structure on SiO/sub 2/ and HfO/sub 2/

In this letter, we investigate a method to adjust the gate work function of an MOS structure by stacking two metals with different work functions. This method can provide work function tunability of approximately 1 eV as the bottom metal layer thickness is increased from 0 to about 10 nm. This behavior is demonstrated with different metal combinations on both SiO/sub 2/ and HfO/sub 2/ gate dielectrics. We use capacitance-voltage (C-V) characteristics to investigate the effect of different annealing conditions and different metal/metal bilayer couples on the work function. By comparing the as-deposited and annealed films, and by comparing with metals that are relatively inert with each other, we deduce that the work function tuning behavior likely involves metal/metal interdiffusion.     

Formation of nanoparticles of sparingly soluble salts (CaSO/sub 4/ and CaSO/sub 4/:Dy) using liquid?liquid separation method and application for detection of /spl alpha/-radiations

This is one of the first reports to demonstrate the formation of nanosize particles (radius of 75-150 nm) of a sparingly soluble salt, calcium sulphate (CaSO₄), using the liquid-liquid separation method. First, the monomer reservoir of nuclei is formed by reacting Ca-salt of dodecyl sulphate in ethylene glycol with sulphuric acid. Secondly, ethanol (i.e. a poor solvent) is added drop by drop to the monomer reservoir under constant stirring to precipitate CaSO₄ (or CaSO₄:Dy) particles. The concentration of the surfactant (SDS), which forms the Ca-salt of dodecyl sulphate, helps to control the size of the nanoparticles. The 75-nm CaSO₄ :Dy particles thus formed are useful for the detection of alpha-radiations     

Amplifying active reflect-antenna using a microstrip-T coupled patch /sub e/sign and measurement

A compact design of an amplifying active reflect-antenna using a novel microstrip-T coupled-patch antenna is proposed. The dual-polarized ports of the microstrip-T coupled-patch antenna provide excellent RF isolation as well as dc isolation. The dc isolation helps in avoiding additional coupling capacitors in the RF path, thereby achieving reduced layout size and cross-polarization levels for the active reflect-antenna. The gain and monostatic radar cross section (RCS) measurement of the active reflect-antenna has been carried out using a time-domain technique based on a single dual-polarized antenna and vector network analyzer. The measured monostatic RCS and gains are then compared with the calculated ones using two different modeling approaches.     

Blue, green and yellow upconversion lasing in Er:YLiF/sub 4/ using 1.5 mu m pumping

The authors report blue, green and yellow upconversion laser action in Er/sup 3+/:YLiF/sub 4/ following pumping at 1.500 mu m below 80 K. For the blue transition the ratio of the output frequency to the input frequency is 3.3, the highest yet reported for an upconversion laser. In spite of the multiple upconversion steps, the thresholds for laser action were less than 80 mW. It is proposed that the nonlinear upconversion pumping proceeds via a sequence of several pairwise cross-relaxation steps.<>     

Matrix and vector multiplications using a 2/sup 1///sub 2/-dimensional systolic array

A pseudo-three-dimensional network, called a 2/sup 1///sub 2/-dimensional systolic array, to compute matrix-vector and matrix-matrix multiplications is introduced. The new architecture achieves twice the throughput rate as that of the conventional systolic arrays with the same number of processing elements. This new approach provides a practical means for the implementation using current integration technology.<>     

Mobility using IEEE 802.21 in a heterogeneous IEEE 802.16/802.11-based, IMT-advanced (4g) network

Industry is defining a new generation of mobile wireless technologies, called in cellular terminology "fourth generation" or "4G." This article shows that a system combining extensions of two radio access technologies, IEEE 802.11 and IEEE 802.16, meets the ITU-R's "IMT-Advanced" or 4G requirements. The extensions are 802.16 m (100 Mb/s, 250 km/h) and 802.11VHT (1 Gb/s, low velocity). The focus of this article is to show how IEEE 802.21 (the emerging IEEE standard for media-independent handover services) supports ";seamless"; mobility between these two radio access technologies. This mobility integrates the two radio access technologies into one system. We conclude that an 802.11VHT + 802.16 m + 802.21 system is likely to be proposed to the ITU-R for IMT- Advanced 4G.     

A 4-in.-based single-step UV-NIL tool using a low vacuum environment and additive air pressure

Ultraviolet nanoimprint lithography (UV-NIL) is a promising technology for the fabrication of sub-10-nm features. Research has focused on employing a large-area stamp to improve UV-NIL throughput, but a large-area stamp makes it difficult to obtain an acceptable uniform residual layer thickness and/or avoid defects such as air entrapment. This paper presents the development of a single-step UV-NIL tool in which a 4-in. Pyrex stamp is first used to imprint coated resin against a 4-in. Si wafer in a low vacuum environment. Pressurized N₂ is subsequently applied to the wafer bottom to improve the quality of imprint results. This UV-NIL tool was used to successfully imprint a 4-in. stamp with recessed patterns engraved over the entire stamp areas onto a 4-in. Si wafer.     

Kinetics of Reactive Ion Etching of Si,SiO2, and Si3N4 in C4F8 + O2 + Ar Plasma: Effect of the C4F8/O2 Mixing Ratio

Russian Microelectronics - The kinetics of reactive ion etching of an Si, SiO2, and Si3N4 in the C4F8 + O2 + Ar mixture with a varied C4F8/O2 mixing ratio under the conditions of an rf inductive...