Oriented Si Wafers Research Articles

Design and experiments for tunable optical sensor fabrication using (1 1 1)-oriented silicon micromachining

The paper presents the design and the experiments performed for integration of a micromechanical voltage tunable Fabry–Perot interferometer structure with a silicon p–n photodiode in order to obtain a tunable optical sensor. The Fabry–Perot interferometer can be used as a voltage tunable filter for the input radiation or as a voltage controlled attenuator to regulate the light from a monochromatic source. In our approach, the top mirror of the Fabry–Perot cavity is an Au/SiO 2 movable membrane, formed by anisotropic etching of (1 1 1)-oriented Si wafers. The Au layer provides a good reflectivity of the upper mirror. The air–silicon surface acts as the lower mirror, as the anisotropic etching of (1 1 1)-oriented Si wafers provides very smooth surfaces. The upper movable mirror can be electrostatically actuated. This Fabry–Perot interferometer was realized on the top of a p–n photodiode.

Microstructure and properties of DC magnetron sputtered NiAl–Hf coatings

NiAl–0.1 at.% Hf coatings were successfully deposited via direct current magnetron sputtering from an alloy target onto a variety of substrates, including: glass; (1 1 1) oriented Si wafers and CMSX-4 ® (registered trademark of the Cannon-Muskegon Corporation, Muskegon, MI), a second generation Ni-base superalloy. The coatings were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The as-deposited coatings were found to be crystalline, consisting of the B2 structured NiAl phase, and to exhibit dense columnar Zone T microstructures. Many of the coatings were textured and the degree of texturing was observed to change with the deposition power used and substrates that were used. NiAl coatings deposited on Si at low powers (⩽50 W) tended to develop random orientations, whereas coatings deposited at higher powers developed strong growth textures. Coatings deposited on Si(1 1 1) exhibited (1 1 1) textures, while coatings deposited on glass exhibited (2 1 1) textures. Thicker coatings (10-μm thick) deposited on CMSX-4 ® superalloy substrates at 400 W exhibited random textures, which could be attributed to the use of higher Ar pressure during deposition. The hardness and the modulus of the different coatings, as measured via nanoindentation testing, varied with crystallographic orientation. Coatings with (1 1 1) and (2 1 1) textures exhibited higher reduced moduli and lower hardness values than randomly oriented coatings, which is in agreement with prior reports on the mechanical behavior of bulk NiAl alloys. Heat treatment of the coatings in argon gas at 500 and 1000 °C for 1 h resulted in decreases in coating hardness, but in no change in the coating modulus. The hardness change is attributed to a combination of grain growth and the annihilation of defects.

Structural evolution of Fe–Al multilayers submitted to thermal annealing

In this paper, we present an experimental study on the structural evolution of B2 type FeAl multilayers submitted to thermal annealing. Multilayer samples have been obtained by evaporating 15 couples of 10 nm Fe and 14 nm Al layers on (100)-oriented Si wafers in an UHV chamber. After deposition, the samples have been heat treated at temperatures ranging from 375 to 775 K. Some samples were also annealed in air to promote the formation of a surface oxide layer. Different analytical techniques were used in order to achieve a complete characterisation of the deposited layers.

Pulsed laser deposition of Nd:YAG on Si with substrate bias voltage

Polycrystalline yttrium aluminum garnet (Y 3Al 5O 12) thin films doped with neodymium have been prepared by the pulsed laser deposition (PLD) method on (1 1 1)-oriented Si wafers. Effect of external DC electrical field applied between substrate and target on the crystal quality was investigated. The growth process was carried out at a rather moderate substrate temperature of 500 °C. Obtained films were characterized by the X-ray diffraction (XRD) complete with radioluminescence spectroscopy (RLS). Intensive radioluminescence spectra of such films are reported for the first time. Laser-produced plasma plume investigations by means of time-of-flight (TOF) mass spectrometer were performed as well. Obtained results clearly indicate that the chemical composition of the plasma plume depends on the target–substrate bias voltage.

Cold ion-cutting of hydrogen implanted Si

The strength of the H-implanted layer has been measured in 〈1 0 0〉 , 〈1 1 1〉 and 〈1 1 0〉 oriented Si wafers using the crack opening method. The required annealing temperature for mechanical layer transfer increases in the order 〈1 0 0〉 , 〈1 1 1〉 and 〈1 1 0〉 . The damage induced by the implantation has been studied by Rutherford backscattering in the channeling mode (RBS/C). The same methods have been used to investigate the influence of boron and arsenic doping on the mechanical exfoliation. Boron doping reduces the strength of the H-implanted layer thereby enabling mechanical layer transfer at temperatures below 200 °C. We found that the exfoliation takes place closer to the wafer surface in highly boron doped Si as compared to the undoped Si. The RBS damage peak also appears to move closer to the surface when the boron concentration of the H-implanted layer is >10 19 cm −3. No lowering of the exfoliation temperature was observed for compensated and arsenic doped Si layers. We suggest that the lowering of the exfoliation temperature with increasing boron doping is related to Si–H bonds associated with the neutralization of shallow acceptors by hydrogen.

Ion-Beam-Assisted Nanocrystal Formation in Silicon Implanted with High Doses of Pb+ and Bi+ Ions

In this paper we discuss ion-beam-assisted nanocrystal nucleation in amorphized silicon (a-Si) layers produced by high-dose implantation of Pb+ and Bi+. (100)-oriented Si wafers were implanted at room temperature (RT) with 50 keV Pb+ and Bi+ ions at doses ranging from 5×1013 to 1×1018 cm-2 and a constant ion current density of 10 µA cm-2. The resulting structures were studied by conventional transmission electron microscopy (CTEM), high resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectroscopy (RBS) in combination with computer simulations. The dynamics of the ion-beam-induced crystallization of new phases and precipitates evolution in the implanted layer were studied as a function of implant dose. It is established that the front of the new phase crystallization (cubic Pb and hexagonal Bi nanocrystals) starts approximately at the peaks of the implanted species profiles; the crystallography of the nucleated nanocrystal is examined as a function of the dose.

Orientation and Boron Concentration Dependence of Si Layer Transfer by Mechanical Exfoliation

ABSTRACTMechanical exfoliation strength has been measured in hydrogen implanted <100>, <111> and <110> oriented Si wafers using the crack opening method. The bonding temperature required for exfoliation increases in the order <100>, <111> and <110>. The same method has been applied to study the influence of boron doping on mechanical exfoliation in <100> Si wafers. The required bonding temperature to exfoliate mechanically decreases with increasing doping level independent of the electrical activation of boron. The enhanced crystallization rate of boron doped Si is suggested as a plausible explanation for the result.

The formation of Ti-silicides by a metal vapour vacuum arc ion source implantation and annealing process

Both 〈0 0 1〉 and 〈1 1 1〉 oriented Si wafers were implanted with Ti ions to 5×10 17ions/cm 2. Under various beam currents, X-ray diffraction (XRD) patterns show that there are different initial silicides created. The formation of C49 TiSi 2 and/or Ti 5Si 3 depends on beam currents and orientations of substrates. When larger beam current was used, C49 TiSi 2 and/or Ti 5Si 3 transformed into C54 TiSi 2. Therefore, the sheet resistance could be reduced. Anneals increase the phase transformation and the C54 TiSi 2 grows with preferential orientations. Different orientation relationships are found on two kinds of wafers. Moreover, it is noted that Ti atomic profile has only a small change after annealing.

Preparation of air-stable, low recombination velocity Si(111) surfaces through alkyl termination

A two-step, chlorination/alkylation procedure has been used to convert the surface Si–H bonds on NH4F(aq)-etched (111)-oriented Si wafers into Si–alkyl bonds of the form Si–CnH2n+1 (n⩾1). The electrical properties of such functionalized surfaces were investigated under high-level and low-level injection conditions using a contactless rf apparatus. The charge carrier recombination velocities of the alkylated surfaces were <25 cm s−1 under high-level and low-level injection conditions, implying residual surface trap densities of <3×109 cm−2. Although the carrier recombination velocity of hydrogen-terminated Si(111) surfaces in contact with aqueous acids is <20 cm s−1, this surface deteriorates within 30 min in an air ambient, yielding a high surface recombination velocity. In contrast, methylated Si(111) surfaces exhibit low surface recombination velocities in air for more than 4 weeks. Low surface recombination velocities were also observed for Si surfaces that had been modified with longer alkyl chains.

Preferential growth of C54 TiSi 2 by metal vapor vacuum arc ion source implantation and post-annealing

Both 〈100〉 and 〈111〉 oriented Si wafers (n-type) were implanted with 45-keV Ti ions to a dose of 4×10 17 ions/cm 2. X-Ray diffraction (XRD) patterns show that there are different initial silicides, such as: C54 TiSi 2, C49 TiSi 2 and Ti 5Si 3. It is interesting that the initial phases are beam current and substrate dependent. When annealing was performed at higher temperature, both the C49 TiSi 2 and Ti 5Si 3 transform into C54 TiSi 2. Moreover, C54 TiSi 2 was grown with various preferential orientations on different substrates in annealing processes. Rutherford backscattering spectrometry (RBS) results show that the Ti atomic profile has little change through annealing. In addition, sheet resistance measurements also reflect that the synthesized disilicide is excellent in electrical conductivity. This suggests that the method has potential for realizing electrical contact in very large-scale integrated (VLSI) circuits.

The Growth and Thermal Stability of Ti-Silicides Obtained by Metal Vapor Vacuum Arc Ion Source Implantation

(100) and (111) oriented Si wafers were implanted with 45 keV, 5 x 10(17) cm(-2) Ti ions at various beam currents. X-ray diffraction (XRD) patterns show that there are different initial silicides such as C49 TiSi2 and Ti5Si3 on various wafers. While annealing was carried out at higher temperatures, both C49 TiSi2 and Ti5Si3 transform into C54 TiSi2. However, it is noted that C54 TiSi2 indicates different preferential orientations on two kinds of wafers. The change of sheet resistance with annealing temperature reflects that the disilicide is more stable than those obtained by solid phase reaction. It is also valuable to find that Ti atomic profiles show only small changes For various anneals.

Formation of Through-Holes on Silicon Wafer by Optical Excitation Electropolishing Method

Through-holes were formed by selective partial electropolishing in a 2.5 wt% HF electrolytic solution, using an N-type, (100)-oriented Si wafer as an anode, and a Pt plate as a cathode. The obtained holes were square through-holes of 5–35 µm side length, with an aspect ratio of 109. It was possible to form such through-holes with a density of 3,500 holes/mm2 in specified areas. It was also confirmed that the pit of the square-based inverted pyramid structure could form deep capillaries. This suggests the possibility of forming microstructures such as pillars and tubes.

Co/Siバルク拡散対における反応拡散

Reactive diffusion of the Co-Si binary system has been studied by using bulk diffusion couples consisting of a 99.98% and 99.997%Co plate and a 〈100〉 oriented Si wafer in the temperature range from 973 K to 1273 K. The experimental results were compared with the previous results obtained by using Co thin film/bulk Si and bulk Co/bulk Si diffusion couples. In these bulk diffusion couples, 3 kinds of Co silicides (Co2Si, CoSi, CoSi2) were formed. All of them grew according to the parabolic law. The interdiffusion coefficients of CoSi in the bulk diffusion couples almost coincide with the values for thin film diffusion couples. However, the values of interdiffusion coefficients of Co2Si for the bulk diffusion couples and thin film diffusion couples do not agree with each other. If the first crystalline phase is Co2Si in Co/Si diffusion couples, the reason for the difference in interdiffusion coefficients between the thin film and bulk samples can be explained by the fast diffusion such as grain boundary diffusion in the thin film diffusion couples.

The Role of Iron in Ti on the Growth of Ti Silicides in Bulk Ti/Si Diffusion Couples

Reaction diffusion in the Ti-Si system has been studied to clarify the roll of iron in Ti on the growth of TiSi 2 by using sandwich type diffusion couples consisting of 99.5%(2N)Ti, 99.9999%(6N) Ti and oriented Si wafer in the temperature range between 1164 and 1323 K. The growth of TiSi 2 formed in 2N-Ti/Si diffusion couples at the lowest temperature in this experiment, 1164 K, was slower than that in a 6N-Ti/Si couples. The difference between the growth rate of 2N-Ti/Si and that in 6N-Ti/Si diffusion couples becomes to be small and to have the same value at 1213 K. These results could be expected from our previous experimental results that the higher the purity of Ti the faster the growth rate and that the lower the purity of Ti the larger the activation energy in the temperature range between 973 and 1123 K. However, the Arrhenius plot of the growth rate, k 2 , for 2N-Ti/Si couple bends at 1213 K and have the same value as the 6N-Ti/Si diffusion couples above 1213 K. As a possible explanation for this behavior of the growth of TiSi 2 in the 2N-Ti/Si couple it has been considered that in the high temperature range impurity iron atoms which segregate at grain boundaries of TiSi 2 and slow down the movement of titanium and silicon atoms diffusing through the grain boundaries in the lower temperature range will redistribute into matrix and the effects become negligible small at high temperature.

Low-temperature Si epitaxy with high deposition rate using ion-assisted deposition

Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition rate and low substrate temperature. We demonstrate epitaxial deposition of Si films on (100)-oriented Si wafers using deposition rates up to 0.3 μm/min at deposition temperatures in the range of 500–650 °C. Hall-effect measurements show a majority carrier mobility of 200 cm2/V s at a hole concentration of 1.4×1017 cm−3 in our films. A minority carrier diffusion length of 4.5 μm is determined from quantum efficiency measurements in the epitaxially grown Si films.

Mask blanks for extreme ultraviolet lithography: Ion beam sputter deposition of low defect density Mo/Si multilayers

We report on the growth of low defect density Mo/Si multilayer (ML) coatings. The coatings were grown in a deposition system specifically designed for extreme ultraviolet lithography mask blank fabrication. Complete, 81 layer, high reflectance Mo/Si ML coatings were deposited on 150 mm diam (100) oriented Si wafer substrates using ion beam sputter deposition. Process added defect densities correspond to 2×10−2/cm−2 larger than 0.13 μm as measured by optical scattering. This represents a reduction in defect density of Mo/Si ML coatings by a factor of 105.

Modeling and Analysis of the Silicon Epitaxial Growth with SiHCl3 in a Horizontal Rapid Thermal Chemical Vapor Deposition Reactor

The growth of epitaxial Si on (100)‐oriented Si wafers in a horizontal rapid thermal chemical vapor deposition (RTCVD) reactor has been investigated. Trichlorosilane was employed as a precursor diluted in carrier gas at 1 atm reactor pressure. The growth rates in dependence of the deposition uniformity, the input partial pressure of the precursor, and the fluid dynamics were analyzed by a three‐dimensional numerical simulation. Good agreement between predicted and measured growth rates were found. Moreover, the experimental growth rates under mass transport limitation were discussed in terms of gas‐phase supersaturation and its impact on the surface morphology. Finally, it is demonstrated that hydrodynamic effects in the RTCVD reactor influence strongly the Si growth in the delivery rate limited regime.

Rotational twins in heteroepitaxial CuInSe2 layers on Si(111)

The microstructure of (112) oriented CuInSe2 heteroepitaxial layers grown with molecular beam epitaxy on (111) oriented Si wafers was investigated by transmission electron microscopy. Experimental and calculated diffraction patterns of different zone axes were compared. Extra spots are caused by rotational twins on (112) growth planes. Six twin variants rotated by ±120°, ±60° and 180° about the [221] axis were identified in the layers. The tetragonal chalcopyrite structure of CuInSe2, the crystal symmetry of the substrate and variations of the growth conditions during the growth are responsible for the formation of these rotational twins. Coherent twin boundaries as well as partly coherent boundaries of twin variants rotated by ±60° and 180° were imaged by high resolution transmission electron microscopy. The boundaries can be formed by inserting partial dislocations with Burgers vectors a/6〈111̄〉 into the CuInSe2 structure. This suggests that the annealing of the samples induces the annihilation of these partial dislocations and consequently reduces the density of twins in the CuInSe2 layers.

Effect of Impurities on Growth of Ti Silicides in Bulk Ti/Si Diffusion Couple

Reaction diffusion and the Kirkendall effect in Ti-Si binary system have been studied by using sandwich-type bulk diffusion couples consisting of 99.99% Ti, 99.9999% Ti plates and a oriented Si wafer. The results have been compared with our previous one obtained by using 99.99% Ti/Si and 99.5% Ti/Si couples. The faster growth of TiSi 2 formed in these Ti/Si diffusion couples, the higher the purity of titanium. To identify the element which slows down the growth rate of TiSi 2 , the effects of oxygen, nitrogen, carbon and iron were studied by adding oxygen and nitrogen into 99.9999% Ti or by depositing carbon and iron on the Ti surface. It has been clarified that iron atoms slow down the growth of TiSi 2 . Silicon atoms diffuse 50 to 100 times faster than titanium atoms in TiSi 2 . Iron affects the diffusivity of Si more effectively than that of Ti. On the basis of these results the role of iron in the Ti/Si bulk reaction diffusion couple has been discussed by taking into account a possibility of diffusion barrier effect or grain boundary diffusion.

Xe +-beam sputtered YBa 2Cu 3O x thin films on Si wafers

Xe-doped Y-Ba-Cu-O films were deposited on p-type (100)-oriented Si wafers by sputtering YBa 3Cu 5O x targets by 3 keV Xe +-beams. The deposited thin films were annealed in O 2 at temperatures of 100–300°C for 48 h. Many of Xe atoms still remained in the thin films annealed at 200°C. The lattice constant of YBa 2Cu 3O x in the thin films was smaller than that in the ASTM cards. Their resistivities started to decrease at 280–300 K and became very small values at 100–140 K.