Showing papers on "Nitride published in 2001"

Properties of advanced semiconductor materials : GaN, AlN, InN, BN, SiC, SiGe

Abstract: Contributors. Preface. Gallium Nitride (GaN) (V. Bougrov, et al.). Aluminum Nitride (AIN) (Y. Goldberg). Indium Nitride (InN) (A. Zubrilov). Boron Nitride (BN) (S. Rumyantsev, et al.). Silicon Carbide (SiC) (Y. Goldberg, et al.). Silicon-Germanium (Si-1-xGe-x) (F. Schaffler). Appendix 1: Basic Physical Constants. Appendix 2: Periodic Table of the Elements. Appendix 3: Rectangular Coordinates for Hexagonal Crystal. Appendix 4: The First Brillouin Zone for Wurtzite Crystal. Appendix 5: Zinc Blende Structure. Appendix 6: The First Brillouin Zone for Zinc Blende Crystal. Additional References.

Thermally conducting aluminum nitride polymer-matrix composites

Abstract: Thermally conducting, but electrically insulating, polymer-matrix composites that exhibit low values of the dielectric constant and the coefficient of thermal expansion (CTE) are needed for electronic packaging. For developing such composites, this work used aluminum nitride whiskers (and/or particles) and/or silicon carbide whiskers as fillers(s) and polyvinylidene fluoride (PVDF) or epoxy as matrix. The highest thermal conductivity of 11.5 W/(m K) was attained by using PVDF, AlN whiskers and AlN particles (7 μm), such that the total filler volume fraction was 60% and the AlN whisker–particle ratio was 1:25.7. When AlN particles were used as the sole filler, the thermal conductivity was highest for the largest AlN particle size (115 μm), but the porosity increased with increasing AlN particle size. The thermal conductivity of AlN particle epoxy-matrix composite was increased by up to 97% by silane surface treatment of the particles prior to composite fabrication. The increase in thermal conductivity is due to decrease in the filler–matrix thermal contact resistance through the improvement of the interface between matrix and particles. At 60 vol.% silane-treated AlN particles only, the thermal conductivity of epoxy-matrix composite reached 11.0 W/(m K). The dielectric constant was quite high (up to 10 at 2 MHz) for the PVDF composites. The change of the filler from AlN to SiC greatly increased the dielectric constant. Combined use of whiskers and particles in an appropriate ratio gave composites with higher thermal conductivity and low CTE than the use of whiskers alone or particles alone. However, AlN addition caused the tensile strength, modulus and ductility to decrease from the values of the neat polymer, and caused degradation after water immersion.

Stress and piezoelectric properties of aluminum nitride thin films deposited onto metal electrodes by pulsed direct current reactive sputtering

Abstract: Polycrystalline aluminum nitride thin films were deposited onto platinum, aluminum, and titanium electrodes by reactive magnetron sputtering in the pulsed direct current mode. The films exhibited all a columnar microstructure and a c-axis texture. The built-in stress and the piezoelectric properties of these films were studied as a function of both the processing conditions and the electrode material. Stress was found to be very much dependent on the growth conditions, and values ranging from strong compression to high tension were observed. The piezoelectric d33,f coefficient was shown to rely on substrate quality and ionic bombardment: The nucleation surface must be stable with regard to the nitrogen plasma and present a hexagonal symmetry and, on the other hand, enough energy must be delivered to the growing film through ionic bombardment.

Nonlinear macroscopic polarization in III-V nitride alloys

Abstract: We study the dependence of macroscopic polarization on composition and strain in wurtzite III-V nitride ternary alloys using ab initio density-functional techniques. The spontaneous polarization is characterized by a large bowing, strongly dependent on the alloy microscopic structure. The bowing is due to the different response of the bulk binaries to hydrostatic pressure and to internal strain effects (bond alternation). Disorder effects are instead minor. Deviations from parabolicity (simple bowing) are of order 10% in the most extreme case of AlInN alloys, much less at all other compositions. Piezoelectric polarization is also strongly nonlinear. At variance with the spontaneous component, this behavior is independent of microscopic alloy structure or disorder effects, and due entirely to the nonlinear strain dependence of the bulk piezoelectric response. It is thus possible to predict the piezoelectric polarization for any alloy composition using the piezoelectricity of the parent binaries.

Optical, electronic, and transport properties of nanocrystalline titanium nitride thin films

Abstract: Spectroscopic ellipsometry (SE) was employed to get insights on the optical, electronic, and transport properties of nanocrystalline titanium nitride (TiNx) films with respect to their microstructure and stoichiometry. The films’ properties can be tailored by varying the energy of bombarding ions during sputter deposition and the substrate temperature (Td). The best metallic behavior of TiNx (resistivity 40 μΩ cm and conduction density 5.5×1022 electrons/cm3) has been observed in films developed with energy above 100 eV and Td⩾400 °C. A redshift of the optical gaps has been observed for overstoichiometric films, suggesting it as a sensitive probe to investigate the TiNx stoichiometry. The energy, strength, and broadening of the interband transitions were studied with respect to the energy of ions and Td and they were explicitly correlated with the TiNx crystal cell size and grain orientation. On the other hand, the study of intraband absorption has provided the conduction electron density with respect to ...

Incorporation of nitrogen in nitride-arsenides: Origin of improved luminescence efficiency after anneal

Abstract: A key to the utilization of nitride-arsenides for long wavelength optoelectronic devices is obtaining low defect materials with long nonradiative lifetimes. Currently, these materials must be annealed to obtain device quality material. The likely defect responsible for the low luminescence efficiency is associated with excess nitrogen. Photoluminescence and capacitance–voltage measurements indicate the presence of a trap associated with excess nitrogen which decreases in concentration upon anneal. Our films are grown by elemental source molecular beam epitaxy and the background impurity concentration is low, thus we have investigated the role of crystalline defects. High resolution x-ray diffraction showed improved crystal quality after anneal. We observed that the lattice parameter does not decrease linearly with nitrogen concentration for levels of nitrogen above 2.9 mol % GaN. The fact that Vegard’s law is not observed, despite theoretical calculations that it should, indicates that nitrogen incorporat...

Group iii nitride based fets and hemts with reduced trapping and method for producing the same

Abstract: New Group III nitride based field effect transistors (10) and high electron mobility transistors (30) are disclosed that provide enhanced high frequency response characteristics. The preferred transistors (10, 30) are made from GaN/AlGaN and have a dielectric layer (22, 44) on the surface of their barrier layer (18, 38). The dielectric layer (22, 44) has a high percentage of donor electrons (68) that neutralize traps (69) in the barrier layer (18, 38) such that the traps (69) cannot slow the high frequency response of the transistors (10, 30). A new method of manufacturing the transistors (10, 30) is also disclosed, with the new method using sputtering to deposit the dielectric layer (18, 38).

Method of forming metal nitride film by chemical vapor deposition and method of forming metal contact and capacitor of semiconductor device using the same

Abstract: A method of forming a metal nitride film using chemical vapor deposition (CVD), and a method of forming a metal contact and a semiconductor capacitor of a semiconductor device using the same, are provided. The method of forming a metal nitride film using chemical vapor deposition (CVD) in which a metal source and a nitrogen source are used as a precursor, includes the steps of inserting a semiconductor substrate into a deposition chamber, flowing the metal source into the deposition chamber, removing the metal source remaining in the deposition chamber by cutting off the inflow of the metal source and flowing a purge gas into the deposition chamber, cutting off the purge gas and flowing the nitrogen source into the deposition chamber to react with the metal source adsorbed on the semiconductor substrate, and removing the nitrogen source remaining in the deposition chamber by cutting off the inflow of the nitrogen source and flowing the purge gas into the deposition chamber. Accordingly, the metal nitride film having low resistivity and a low content of Cl even with excellent step coverage can be formed at a temperature of 500° C. or lower, and a semiconductor capacitor having excellent leakage current characteristics can be manufactured. Also, a deposition speed, approximately 20 A/cycle, is suitable for mass production.

Evolution of III-V nitride alloy electronic structure: the localized to delocalized transition.

Abstract: Addition of nitrogen to III-V semiconductor alloys radically changes their electronic properties. We report large-scale electronic structure calculations of GaAsN and GaPN using an approach that allows arbitrary states to emerge, couple, and evolve with composition. We find a novel mechanism of alloy formation where localized cluster states within the gap are gradually overtaken by a downwards moving conduction band edge, composed of both localized and delocalized states. This localized to delocalized transition explains many of the hitherto puzzling experimentally observed anomalies in III-V nitride alloys.

Group III nitride compound semiconductor device

Abstract: A titanium layer and a titanium nitride layer are successively laminated on a substrate and a group III nitride compound semiconductor layer is further formed thereon. When the titanium layer is removed in the condition that a sufficient film thickness is given to the titanium nitride layer, a device having the titanium nitride layer as a substrate is obtained.

Chemical vapor deposition of barriers from novel precursors

Abstract: The present invention provides a method and precursor for forming a metal and/or metal nitride layer on the substrate by chemical vapor deposition. The organometallic precursor has the formula of (Cp(R)n)xMHy-x, where Cp is a cyclopentadienyl functional group, R is a substituent on the cyclopentadienyl functional group comprising an organic group having at least one carbon-silicon bond, n is an integer from 0 to 5, x is an integer from 1 to 4, M is a metal, and y is the valence of the metal M. A metal, metal nitride, metal carbon nitride, or metal silicon nitride film (118; 119) is deposited on a heated substrate (112) by thermal or plasma enhanced decomposition of the organometallic precursor in the presence of a processing gas, such as hydrogen, nitrogen, ammonia, silane, and combinations thereof, at a pressure of less than about 26.66 hPa (20 Torr). By controlling the reactive gas composition either metal or metal nitride films may be deposited. The deposited metal or metal nitride film (118; 119) may then be exposed to a plasma to remove contaminants, densify the film, and reduce film resistivity.

Iii-v nitride substrate boule and method of making and using the same

Abstract: A boule formed by high rate vapor phase growth of Group III-V nitride boules (ingots) on native nitride seeds (Figure 1), from which wafers may be derived for fabrication of microelectronic structures (Figure 5). The boule is of microelectronic device quality, e.g., having a transverse dimension greater than 1 centimeter, a length greater than 1 millimeter, and a top surface defect density of less than 107 defects cm-2. The Group III-V nitride boule may be formed by growing a Group III-V nitride material on a corresponding native Group III-V nitride seed crystal by vapor phase epitaxy at a growth rate above 20 micrometers per hour.

Multilayer dielectric stack and method

Abstract: A multilayer dielectric stack is provided which has alternating layers of a high-k material and an interposing material. The presence of the interposing material and the thinness of the high-k material layers reduces or eliminate effects of crystallization within the high-k material, even at relatively high annealing temperatures. The high-k dielectric layers are a metal oxide of preferably zirconium or hafnium. The interposing layers are preferably amorphous aluminum oxide, aluminum nitride, or silicon nitride. Because the layers reduce the effects of crystalline structures within individual layers, the overall tunneling current is reduced. Also provided are atomic layer deposition, sputtering, and evaporation as methods of depositing desired materials for forming the above-mentioned multilayer dielectric stack.

Metalorganic chemical vapor deposition of GaN on Si(111): Stress control and application to field-effect transistors

Abstract: Two schemes of nucleation and growth of gallium nitride on Si(111) substrates are investigated and the structural and electrical properties of the resulting films are reported. Gallium nitride films grown using a 10–500 nm-thick AlN buffer layer deposited at high temperature (∼1050 °C) are found to be under 260–530 MPa of tensile stress and exhibit cracking, the origin of which is discussed. The threading dislocation density in these films increases with increasing AlN thickness, covering a range of 1.1 to >5.8×109 cm−2. Films grown using a thick, AlN-to-GaN graded buffer layer are found to be under compressive stress and are completely crack free. Heterojunction field effect transistors fabricated on such films result in well-defined saturation and pinch-off behavior with a saturated current of ∼525 mA/mm and a transconductance of ∼100 mS/mm in dc operation.

Tantalum nitride CVD deposition by tantalum oxide densification

Abstract: The invention provides a method for forming a metal nitride film by depositing a metal oxide film on the substrate and exposing the metal oxide film to a nitrating gas to densify the metal oxide and form a metal nitride film. The metal oxide film is deposited by the decomposition of a chemical vapor deposition precursor. The nitrating step comprises exposing the metal oxide film to a thermally or plasma enhanced nitrating gas preferably comprising nitrogen, oxygen, and ammonia. The invention also provides a process for forming a liner/barrier scheme for a metallization stack by forming a metal nitride layer over the substrate by the densification of a metal oxide layer by a nitrating gas depositing a metal liner layer. Optionally, a metal liner layer may be deposited over substrate prior to the metal nitride layer to forma metal/metal nitride liner/barrier scheme. The invention further provides a process to form a microelectronic device comprising forming a first electrode, forming a metal nitride layer over the first electrode by densifying a metal oxide layer by a nitrating gas to form a metal nitride layer, depositing a dielectric layer over the metal nitride layer, and forming a second electrode over the dielectric layer. Alternatively, the metal nitride film may comprise the first and second electrodes.

Low resistance magnetic tunnel junction device with bilayer or multilayer tunnel barrier

Abstract: A low resistance magnetic tunnel junction (MTJ) device has a bilayer or multilayer as the insulating tunnel barrier. In one embodiment the tunnel barrier is a bilayer of a first layer of magnesium oxide on the bottom magnetic electrode and an aluminum oxide layer on the magnesium oxide layer. This bilayer is formed by oxidizing a bilayer of Mg/Al. In a second embodiment the tunnel barrier is a bilayer of first layer of aluminum nitride and a second layer of aluminum oxide on top of the aluminum nitride first layer, with this bilayer formed by oxidizing a bilayer of AlN/Al. MTJ devices with trilayer barriers, such as AlN/Al2O3/AlN, MgO/Al2O3/MgO and Al2O3/MgO/Al2O3 are also possible. The resulting magnetic tunnel junction devices have resistance-area values less than 1000 Ω(μm)2 and preferably in the range of 0.1 to 100 Ω(μm)2, making the devices suitable for magnetic read sensors.

Raman and infrared modes of hydrogenated amorphous carbon nitride

Abstract: Features in the Raman and infrared (IR) spectra of highly sp3 bonded hydrogenated amorphous carbon nitride films are assigned The Raman spectra show three main features all found in a-C itself, the G and D peaks at 1550 and 1350 cm−1, respectively, and the L peak near 700 cm−1 The intensity ratio of the D and G peaks, I(D)/I(G), is found to scale as (band gap)−2, which confirms that nitrogen induces carbon to form sp2 graphitic clusters The intensity of the L mode is found to scale with the D mode, supporting its identification as an in-plane rotational mode of sixfold rings in graphitic clusters A small feature at 2200 cm−1 due to C≡N modes is seen, but otherwise the Raman spectra resembles that of a-C and shows no specific features due to N atoms The hydrogen content is found to have a strong effect on the IR spectra at 1100–1600 cm−1 making this band asymmetric towards the 1600 cm−1 region

Large area dense nanoscale patterning of arbitrary surfaces

Abstract: We demonstrate a large-area fabrication of hexagonally ordered metal dot arrays with an area density of ∼1011/cm2. We produced 20 nm dots with a 40 nm period by combining block copolymer nanolithography and a trilayer resist technique. A self-assembled spherical-phase block copolymer top layer spontaneously generated the pattern, acting as a template. The pattern was first transferred to a silicon nitride middle layer by reactive ion etch, producing holes. The nitride layer was then used as a mask to further etch into a polyimide bottom layer. The metal dots were produced by an electron beam evaporation followed by a lift-off process. Our method provides a viable route for highly dense nanoscale patterning of different materials on arbitrary surfaces.

Method for forming nitride spacer by using atomic layer deposition

Abstract: The present invention provides a method for forming a silicon nitride spacer by using an atomic layer deposition (ALD) method. The procedure of the ALD is to use a first kind of excess gas as a reactant air and thus produce a first mono-layer solid phase of the first reactant air on the wafer. When the first chemical reaction is completed, the first excess air is drawn out, and then the second excess air is released to deposit a second mono-layer solid phase of the second reactant air on the first mono-layer solid phase. In this way, a whole deposited layer with a layer of the first mono-layer solid phase, a layer of the second mono-layer solid phase, and so on are stepwise formed on the wafer surface. The ALD method is a time consuming task in deposition process such as in the generation of 0.35 μm to 0.5 μm of VLSI ages. However, in the generation of 0.18 μm, 0.13 μm or beyond of VLSI ages, because the device is getting smaller than ever before, the deposition speed of the ALD method is just right on time to meet the demand and is an appropriate method in depositing silicon nitride spacer.

Accurate calculation of polarization-related quantities in semiconductors

Abstract: We demonstrate that polarization-related quantities in semiconductors can be predicted accurately from first-principles calculations using the appropriate approach to the problem, the Berry-phase polarization theory. For III-V nitrides, our test case, we find polarization, piezoelectric constants, and polarization differences between nitride pairs, and piezoelectric constants quite close to their previously established values. Refined data are nevertheless provided for all the relevant quantities.

Highly reflective ohmic contacts to III-nitride flip-chip LEDs

Abstract: An inverted III-nitride light-emitting device (LED) with highly reflective ohmic contacts includes n- and p-electrode metallizations that are opaque, highly reflective, and provide excellent current spreading. The n- and p-electrodes each absorb less than 25% of incident light per pass at the peak emission wavelength of the LED active region.

Analog characteristics of metal-insulator-metal capacitors using PECVD nitride dielectrics

Abstract: The frequency dependence of PECVD nitride and LPCVD oxide metal-insulator-metal (MIM) capacitors is investigated with special attention for precision analog applications. At measurement frequencies of 1.0 MHz, nitride MIM capacitors show capacitance linearity close to that of oxide MIM capacitors, indicating potential for precision analog circuit applications. Due to dispersion effects, however, nitride MIM capacitors show significant degradation in capacitor linearity as the frequency is reduced, which leads to accuracy limitations for precision analog circuits. Oxide MIM capacitors are essentially independent of frequency.

Single-crystal aluminum nitride nanomechanical resonators

Abstract: Aluminum nitride is a light, stiff, piezoelectrically active material that can be epitaxially grown on single-crystal Si. AlN is beginning to play a role in the integration of semiconducting electronic and surface acoustic wave devices, and may prove useful for the integration of other types of mechanical devices as well. We describe the growth and subsequent electron-beam patterning and etching of epitaxial AlN-on-silicon films into nanomechanical flexural resonators. We have measured resonators with fundamental mechanical resonance frequencies above 80 MHz, and quality factors in excess of 20 000.

Influence of electron-phonon interaction on the optical properties of III nitride semiconductors

Abstract: The electronic band structures of III nitride semiconductors calculated within the adiabatic approximation give essential information about the optical properties of materials. However, atoms of the lattice are not at rest; their displacement away from the equilibrium positions perturbs the periodic potential acting on the electrons in the crystal, leading to an electron-phonon interaction energy. Due to different ways that the lattice vibration perturbs the motions of electrons, there are various types of interaction, such as Frohlich interaction with longitudinal optical phonons, deformation-potential interactions with optical and acoustic phonons and piezoelectric interaction with acoustic phonons. These interactions, especially the Frohlich interaction, which is very strong due to the ionic nature of III nitrides, have a great influence on the optical properties of the III nitride semiconductors. As a result of electron-phonon interaction, several phenomena, such as phonon replicas in the emission spectra, homogeneous broadening of the excitonic line width and the relaxation of hot carriers to the fundamental band edge, which have been observed in GaN and its low dimensional heterostructures, are reviewed.

Microneedles for minimally invasive drug delivery

Abstract: The present invention provides a microneedle incorporating a base that is broad relative to a height of the microneedle, to minimize breakage. The microneedle further includes a fluid channel and a beveled non-coring tip. Preferably arrays of such microneedles are fabricated utilizing conventional semiconductor derived micro-scale fabrication techniques. A dot pattern mask is formed on an upper surface of a silicon substrate, with each orifice of the dot pattern mask corresponding to a desired location of a microneedle. Orifices are formed that pass completely through the substrate by etching. A nitride pattern mask is formed to mask all areas in which a nitride layer is not desired. A nitride layer is then deposited on the bottom of the silicon substrate, on the walls of the orifice, and on the top of the silicon substrate around the periphery of the orifice. The nitride layer around the periphery of the orifice is offset somewhat, such that one side of the orifice has a larger nitride layer. Anisotropic etching is used to remove a substantial portion of the substrate, creating a plurality of angular, blunt, and generally pyramidal-shaped microneedles. A subsequent removal of the nitride layer, followed by an isotropic etching step, softens and rounds out the blunt angular microneedles, providing generally conical-shaped microneedles. The uneven nitride layer adjacent the orifice ensures that the microneedles will include a beveled tip. Such microneedle arrays are preferably incorporated into handheld diagnostic and drug delivery systems.

Semiconductor processing equipment having improved particle performance

Abstract: A ceramic part having a surface exposed to the interior space, the surface having been shaped and plasma conditioned to reduce particles thereon by contacting the shaped surface with a high intensity plasma. The ceramic part can be made by sintering or machining a chemically deposited material. During processing of semiconductor substrates, particle contamination can be minimized by the ceramic part as a result of the plasma conditioning treatment. The ceramic part can be made of various materials such as alumina, silicon dioxide, quartz, carbon, silicon, silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum nitride or titanium carbide. The ceramic part can be various parts of a vacuum processing chamber such as a liner within a sidewall of the processing chamber, a gas distribution plate supplying the process gas to the processing chamber, a baffle plate of a showerhead assembly, a wafer passage insert, a focus ring surrounding the substrate, an edge ring surrounding an electrode, a plasma screen and/or a window.

METHOD FOR ACHIEVING IMPROVED EPITAXY QUALITY (SURFACE TEXTURE AND DEFECT DENSITY) ON FREE-STANDING (ALUMINUM, INDIUM, GALLIUM) NITRIDE ((Al,In,Ga)N) SUBSTRATES FOR OPTO-ELECTRONIC AND ELECTRONIC DEVICES

Abstract: A III-V nitride homoepitaxial microelectronic device structure comprising a III-V nitride homoepitaxial epi layer on a III-V nitride material substrate, e.g., of freestanding character. Various processing techniques are described, including a method of forming a III-V nitride homoepitaxial layer on a corresponding III-V nitride material substrate, by depositing the III-V nitride homoepitaxial layer by a VPE process using Group III source material and nitrogen source material under process conditions including V/III ratio in a range of from about 1 to about 105, nitrogen source material partial pressure in a range of from about 1 to about 103 torr, growth temperature in a range of from about 500 to about 1250 degrees Celsius, and growth rate in a range of from about 0.1 to about 500 microns per hour. The III-V nitride homoepitaxial microelectronic device structures are usefully employed in device applications such as UV LEDs, high electron mobility transistors, and the like.

Thermal cross-linking and pyrolytic conversion of poly(ureamethylvinyl)silazanes to silicon-based ceramics

Abstract: The aim of this work was to study the pyrolytic conversion of a novel commercial polysilazane, poly(ureamethylvinyl)silazane (PUMVS; Ceraset™, Allied Signal Composites Inc., USA), into silicon-based ceramics. The precursor was thermally cross-linked and pyrolyzed between 200 and 1700 °C under argon or nitrogen atmosphere and the products were investigated by spectroscopic techniques (FTIR and Raman spectroscopy, solid-state NMR), elemental analysis and simultaneous thermal analysis coupled with mass spectrometry. Upon heating under argon, the starting liquid precursor transformed into an infusible solid polymer at T > 250 °C with a conversion yield of >95 wt%. The cross-linking solidification occurred predominantly through hydrosilylation or addition reaction involving vinyl groups. Subsequent pyrolysis of the cross-linked products around 1000 °C in argon yielded amorphous silicon carbonitride ceramics with a composition of SiN0.82C0.86. The overall ceramic yield (with respect to the starting PUMVS) was around 70 wt%, which was found to be independent of the initial cross-linking step. Solid-state NMR (29Si and 13C) revealed that the amorphous silicon carbonitrides contain predominately CSiN3 units. There is evidence for the formation of free amorphous carbon between 700 and 800 °C. Graphitic phases were detected by X-ray diffraction in the samples heated to T > 1000 °C at high heating rates. Upon annealing at T > 1500 °C, the excess carbon reacted completely with the silicon (carbo)nitride to form SiC and nitrogen. The final ceramics contained a large amount of crystalline SiC (∼90 wt%), and were free of excess carbon or silicon. Therefore, PUMVS is an ideal precursor for the formation of high-quality SiC-based ceramics. Copyright © 2001 John Wiley & Sons, Ltd.