Single-crystal Silicon Plates Research Articles

OPTICAL AND STRENGTH PROPERTIES OF SACRIFICIAL LAYERS
 BASED ON POLYIMIDE FILMS

Optical and strength properties of films of a polyimide composition (polyimide PI-2610) for creating a sacrificial
 layer deposited on the surface of single-crystal silicon plates of the KDB-10 brand by centrifugation are
 investigated. It has been established that they behave like elastoplastic materials. The true microhardness of polyimide
 PI-2610, measured at a load of 2 g, was ~0,5 GPa. The spectra of the disturbed total internal reflection
 (NPVO) of polyimide PI-2610 were compared with the spectra of the NPVO of pyrrole and kapton polyimide.
 In the spectrum of the polyimide PI-2610, there are bands of vibrations of the 5-membered ring and valence
 vibrations of the C–Nst and CO–Cst groups. The most intense band in the spectrum of NPVO (as in pyrrole) is the band
 of deformation vibrations C-H with a maximum at 734 cm-1. The band at ~1700 cm-1, caused by valence vibrations
 of the C=O double bond, has two closely spaced maxima at 1706 and 1692 cm-1, which indicates two variants
 of the force field around the C=O bond. The presence of hydroxyl O–H groups in the spectra of polyimide
 PI-2610 was detected due to the presence of residual water in the polyimide structure.

Quality factor boosting of bulk acoustic wave resonators based on a two dimensional array of high-Q resonant tanks

An innovative resonance excitation methodology of a two-dimensional array of uniformly patterned structure into extremely high-quality factor (Q) mode using engineered frequency-matched thin piezoelectric film on substrate (TPoS) transducer is demonstrated in this Letter. The passive Q-enhancement can be attained lithographically without adding to the power requirement of the system. A 500 nm thick piezoelectric material facilitates the inter-electrical-mechanical domain coupling, and the displacement generated at the transducer periphery drives the patterned 10 μm thick single crystal silicon plate into various resonant modes. Using this topology, unexplored modes can be generated as well by the forced vibration feature of the interacting resonant tanks. Utilizing a multiport port excitation scheme, multiple modes are explored, while the primary focus is maintained on the Lamé mode of the array. In vacuum for an operational frequency of 58.56 MHz, an exceptionally high-quality factor of 58 276 is attained with a motional resistance of 1250 Ω and this is the record-high figure of merit (f × Q = 3.4 × 1012) attained for aluminum nitride-based TPoS based resonators. This successful demonstration of the energy coupling scheme paves a path for the study of existing and investigation of unexplored high-Q modes spanning over a wide range of frequency, making these devices a potential candidate for radio frequency front-end applications. The CMOS compatibility of aluminum nitride makes it an attractive solution for achieving low phase noise monolithically integrated CMOS–microelectromechanical systems oscillators.

Structure and morphology of SiC nanostructures synthesized on Cu films

The results of experiments on the synthesis of SiC nanostructures by chemical vapor deposition in microwave plasma are presented in this article. The single crystal silicon plates with orientation [111] which previously passed chemical purification were used as substrates. Furthermore, the substrates of porous silicon were prepared in order to activate the surface during the synthesis. The synthesis temperatures were 600 °C and 700 °C. Studies by scanning electron microscopy showed that formed nanostructures have a various diameter and a rough surface. The results of studies by Raman scattering confirmed that SiC nanostructures with structure of 3C-SiC are formed. Besides, the presence of main carbon peaks on both types of substrates which correspond to the carbon nanostructures should be noted.

Ion-Beam Synthesis of Ferromagnetic Films by the Implantation of Co+ Ions into Silicon

Thin ferromagnetic films of cobalt silicide are synthesized by implanting Co+ ions into single-crystal silicon plates under an external magnetic field. Scanning magnetopolarimetry shows that the samples implanted at a dose greater than 2 × 1017 cm–2 have uniaxial magnetic anisotropy. Based on the dose dependence of the anisotropy field and the experiment on switching the direction of the easy magnetization axes, it is concluded that the induced magnetic anisotropy in the resulting films is due to the directional atomic pair ordering. The absence of the effect of external mechanical stress created during implantation on the magnetic properties of cobalt-silicide films is revealed.

Investigation of SiC and C Nanostructures Obtained by MWCVD

The results of experiments on the synthesis of SiC and C nanostructures by chemical vapor deposition in microwave plasma are presented in this article. The single crystal silicon plates with orientations [100] and [111] which previously passed chemical purification were used as substrates. Also, the substrates of porous silicon were prepared in order to activate the surface during the synthesis. The synthesis temperature ranged from 700 to 900 °C in steps of 100 °C. The pressure in the chamber was changed depending on the power of the plasma. Studies by scanning electron microscopy (SEM) showed that formed nanostructures have a diameter of 200‒350 nm and a rough surface. The formation of nanostructures on the polished Si occurs on the SiC buffer layer. Analysis of SEM images of the samples shows that growth of NS on the surface of porous silicon is more widespread in contrast to the polished Si. The results of X-Ray spectral microanalysis showed that the carbon content in samples of nanostructures on polished Si varies from 10 to 20% and remains constant on porous silicon ~ 25%. The results of studies by Raman scattering confirmed that SiC film with structure of 3C-SiC is formed on the polished Si. Besides, the presence of main carbon peaks on both types of substrates in the range of 1338.2 and 1583 cm‒1 should be noted, which correspond to the carbon nanostructures.

Photoemission electron microscopy of arrays of submicron nickel rods in a silicon dioxide matrix

Arrays of Ni rods (∼500 nm diameter) formed by the ion-track technology in combination with electrochemical deposition into a SiO2 matrix on the surface of single-crystal silicon plates have been investigated using photoemission electron microscopy with high-intensity synchrotron (undulator) radiation. An analysis of the Ni L 2,3 X-ray absorption near-edge structure (XANES) spectra has demonstrated that rod-like structures in pores and connecting bridges between the rods are formed by a metallic nickel phase, which is stable to oxidation by atmospheric oxygen. No formation of intermediate compound phases (nickel silicides and oxides) is observed at the Ni/SiO2 heterojunction, whereas oxidized nickel(II) species are identified on the surface of the SiO2 matrix, which presumably can be attributed to nickel silicate and hydroxide compounds formed upon nickel(II) chemisorption in electrochemical deposition electrolytes.

An anomalous increase in the fill factor of the current-voltage characteristic in the short-wave region of the solar spectrum for a silicon photocell containing a porous-silicon structure

The possibility of increasing the efficiency of a silicon photocell by forming a porous-silicon structure in its bulk has been proposed and studied. Photocells produced from p-type single-crystal silicon plates by the diffusion method were investigated. Porous-silicon structures were formed by photoelectric anodic etching in HF-ethanol mixture. Current density and etching time were assigned by a computer in ranges of 6–14 mA/cm2 and 10–20 s, respectively. It has been found that the porous-silicon structure located in the emitter bulk substantially improves efficiency of photocells. At wavelength λ ∼ 550 nm, an anomalously large (by five to nine times) increase in efficiency was observed.

3-D airborne ultrasound synthetic aperture imaging based on capacitive micromachined ultrasonic transducers

In this paper, we present an airborne 3-D volumetric imaging system based on capacitive micromachined ultrasonic transducers (CMUTs). For this purpose we fabricated 89-kHz CMUTs where each CMUT is made of a circular single-crystal silicon plate with a radius of 1mm and a thickness of 20μm, which is actuated by electrostatic force through a 20-μm vacuum gap. The measured transmit sensitivity at 300-V DC bias is 14.6Pa/V and 24.2Pa/V, when excited by a 30-cycle burst and a continuous wave, respectively. The measured receive sensitivity at 300-V DC bias is 16.6mV/Pa (−35.6dB re 1V/Pa) for a 30-cycle burst. A 26×26 2-D array was implemented by mechanical scanning a co-located transmitter and receiver using the classic synthetic aperture (CSA) method. The measurement of a 1.6λ-size target at a distance of 500mm presented a lateral resolution of 3.17° and also showed good agreement with the theoretical point spread function. The 3-D imaging of two plates at a distance of 350mm and 400mm was constructed to exhibit the capability of the imaging system. This study experimentally demonstrates that a 2-D CMUT array can be used for practical 3-D imaging applications in air, such as a human–machine interface.

A numerical approach to the analysis of failure modes in anisotropic plates

This study is motivated by the attempt to characterize failure modes of silicon chips commonly used in electronic industries. Previous experimental investigations provided the failure probability of dies made of a single-crystal and produced a large variety of crack patterns, but were not able to elucidate the link between defect distributions and crack initiation and propagation. To get some insight in the fracture activation and propagation mechanisms, we resort to finite element analyses and adopt an explicit methodology for crack tracking, based on the self-adaptive insertion of cohesive elements into a coherent mesh of solid elements. Finite kinematics material models with anisotropic features for both bulk and cohesive surfaces are employed to describe the behavior of single-crystal silicon plates undergoing a particular bending test up to failure. The cohesive model adopted in the calculation is fully anisotropic and newly formulated to accomplish the present study. Numerical simulations considering different material properties were able to ascertain the effects of particular flaws on failure modes of brittle silicon plates.

The mechanism of formation and some properties of thin fluorocarbon films deposited onto silicon plates by electron-beam polymerization of hexafluoropropylene from the vapor phase

The results of studying thin fluorocarbon films deposited onto single-crystal silicon plates through electron beam polymerization of hexafluoropropylene from the vapor phase are presented. The films are deposited under the action of an electron beam with an energy of 40 keV at a monomer vapor pressure of 5- 20 hPa. It is shown that plastic solid films consisting of a low-molecular-mass polymer with low thermal stability are formed at a beam current density on the order of 20 μA/cm2, while at current densities on the order of 150 μA/cm2, rigid brittle films of three-dimensional crossl inked polymer are formed with a thermal stability of about 350°C. It is assumed that the films are formed via chain polymerization, which at high current densities, is accompanied by polyrecombination processes leading to efficient chain crosslinking. It is found that polymer clusters are ordered in the course of film formation.

Studying diffusion in multilayer thin-film structures on silicon by the contact melting technique

Features of the contact melting in thin-film structures comprising an aluminum layer with a thickness of h1 = 5 μm and a metal (Ti, Ni, Mo) or semiconductor (Si, Ge) sublayer (h2 = 0.1 μm) on a single crystal silicon plate (h3 = 500 μm) have been studied. The contact melting was caused by single rectangular electric pulses with a current density of j < 9 × 1010 A/m2 and a duration of τ = 100–1000 μs passing through the Al layer. The duration and rate of melting in the samples were determined using voltage waveforms measured by an oscillograph. A method has been developed based on an analysis of the mechanisms of contact interaction in the Al film—sublayer system (with allowance for experimental data on the time of sublayer dissolution in the Al film) for estimating the coefficients of mutiphase diffusion of the system components during the passage of a current pulse.

P-MNS-05 FRICTION ANISOTROPY BETWEEN DIFFERENT MATERIALS MEASURED UNDER HIGH-VACUUM CONDITIONS(Micro/Nanosystem Science and Technology,Technical Program of Poster Session)

Friction force was measured between single-crystal silicon plates and a single-crystal-tipped gold pin under a high vacuum of 1.5×10^<-5> Pa. A reciprocating micro-tribotester was used to rub a gold pin that had a (111) and (100) surface on its spherical tip against the (111) and (100) surfaces of silicon plates, respectively. The external applied normal load was 10μN. By rotating the silicon plate, difference between each crystal orientation was changed and the relationship between the friction force and mutual angle was examined. A maximum anisotropy factor of about ten was found between the combinations of the (111) surfaces.

Generation of highly uniform droplets using asymmetric microchannels fabricated on a single crystal silicon plate: Effect of emulsifier and oil types

Uniform droplets of soybean oil, MCT (medium-chain fatty acid triglyceride) oil and n-tetradecane with a mean diameter of 26–29 μm have been generated using a silicon 24 × 24 mm microchip consisting of 23,489 asymmetric microchannels fabricated by photolitography and deep-reactive ion etching. Each microchannel consisted of a circular 10-μm diameter straight hole with a length of 70 μm and a 50 × 10 μm rectangular microslot with a depth of 30 μm. At the constant oil flux of 10 L m − 2 h − 1 , the percent of active channels increased with increasing the oil viscosity and ranged from 4% for n-tetradecane to 48% for soybean oil. The size distribution span for SDS (sodium dodecyl sulphate)- and Tween 20 (polyoxyethylene (20) sorbitan monolaurate)-stabilized soybean and MCT oil droplets was 0.21–022. The ability of asymmetric microchannels to generate monodisperse soybean oil droplets at the very low SDS concentration of 0.01 wt.% has been demonstrated. At the SDS concentration below the CMC, the generated droplets tend to attach to the plate surface, whereas at the higher SDS concentration they detach from the plate as soon as they are formed. The agreement between the experimental and CFD (Computational Fluid Dynamics) simulation results was excellent for soybean oil and the poorest for n-tetradecane.

Contouring of polished single-crystal silicon plates by wire electrical discharge machining

We investigate the effect of cutting by wire electrical discharge machining (WEDM) on the shape accuracy of polished single-crystal silicon. Single-crystal silicon plates are polished, and then contoured in deionized water or in oil by WEDM. The shape accuracy of the polished surfaces is measured with an interferometer. As a result, the polished surfaces are deformed into convex shapes by WEDM cutting. The polished surfaces tend to become flat as the roughness of the cut sections decreases, and the flatness is independent of the type of cutting liquid. Cutting in oil is advantageous for maintaining the smoothness of polished surfaces. These findings confirm that, in the contouring process of polished single-crystal silicon blocks, smooth and high-accuracy surfaces are achieved by conducting rough- and finish-cutting WEDM processes in oil.

Direct electrolytic reduction of solid SiO 2 in molten CaCl 2 for the production of solar grade silicon

The direct electrolytic reduction of solid SiO 2 has been investigated in molten CaCl 2 at 1123 K aiming at the production of solar grade silicon (SOG-Si). A new type of SiO 2 contacting electrode was prepared to prevent the metal contamination from a conducting wire; the top end of an SiO 2 glass plate was put between two single crystal silicon plates and they were wound by a molybdenum wire. A silicon ingot was successfully produced from the electrochemically reduced samples by separating the silicon from the unreduced SiO 2 by means of a melting process under vacuum at 1773 K. The purity of the silicon ingot was 99.80 at.% at this stage, due to the metal contamination from the stainless vessel. However, the concentrations of boron and phosphorus were very low in the ingot, which verifies the applicability of this electrochemical process for the SOG-Si production.

Formulation of monodisperse emulsions using submicron-channel arrays

Microchannel (MC) emulsification is a promising technique for formulating monodisperse emulsions using a microfabricated channel array. This study used submicron-channel (SMC) arrays with an equivalent diameter as small as 0.57 μm microfabricated on a single-crystal silicon plate to formulate soybean oil-in-water (O/W) emulsions with fine droplets. Monodisperse O/W emulsions with average droplet diameters of 1.4–3.5 μm and minimum coefficients of variation (CV) of approximately 9% were successfully formulated using the SMC arrays. The droplet production rate of an SMC plate reached up to 2.2 × 10 4 droplets/s.

Investigation of the Casimir force between metal and semiconductor test bodies

The measurement of the Casimir force between a large gold coated sphere and single crystal silicon plate is performed with an atomic force microscope. A rigorous statistical comparison of data with theory is done, without use of the concept of root-mean-square deviation, and excellent agreement is obtained. The Casimir force between metal and semiconductor is demonstrated to be significantly different than between two similar or dissimilar metals.

Cutting of polished single-crystal silicon by wire electrical discharge machining

Smoothly polished single-crystal silicon plates were cut by wire electrical discharge machining (WEDM) in water and in oil in order to investigate the effect of WEDM on the polished surfaces. For cutting in water, polished surfaces near cut sections have chips and cracks, and are extremely rough; the rough regions are upheaved. Examinations suggest that the upheaved region is silicon dioxide and results from oxidization of the surfaces by WEDM. Moreover, the polished surfaces far from the cut section are somewhat rough. For cutting in oil, polished surfaces near a cut section are smooth and almost flat although they have chips and cracks. These findings indicate the WEDM in oil is better than that in water for cutting polished single-crystal silicon to obtain high-quality surfaces.

A CMOS-MEMS mirror with curled-hinge comb drives

A micromirror achieves up to ±4.7° angular displacement with 18 Vdc by a comb-drive design that uses vertical angled offset of the comb fingers. Structures are made from a combination of CMOS interconnect layers and a thick underlying silicon layer. Electrical isolation of the silicon fingers is realized with a slight silicon undercut etch, which disconnects sufficiently narrow pieces of silicon under the CMOS microstructures. The 1 mm by 1 mm micromirror is made of an approximately 40 μm-thick single-crystal silicon plate coated with aluminum from the CMOS interconnect stack. The mirror has a peak-to-peak curling of 0.5 μm. Fabrication starts with a conventional CMOS process followed by dry-etch micromachining steps. There is no need for wafer bonding and accurate front-to-backside alignment. Such capability has potential applications in biomedical imaging, optical switches, optical scanners, interferometric systems, and vibratory gyroscopes.

Modeling and simulation of the tool wear in nanometric cutting

Tool wear is a significant factor affecting the machined surface quality. In this paper, a molecular dynamics (MD) simulation approach is proposed to model the wear of the diamond tool in nanometric cutting. It includes the effects of the cutting heat on the workpiece property. MD simulation is carried out to simulate the nanometric cutting of a single crystal silicon plate with the diamond tip of an atomic force microscope (AFM). The wear mechanism is investigated by the calculation of the temperature, the stress in the diamond tip, and the analysis of the relationship between the temperature and sublimation energy of the diamond atoms and silicon atoms. Microstrength is used to characterize the wear resistance of the diamond tool. The machining trials on an AFM are performed to validate the results of the MD simulation. The results of MD simulation and AFM experiments all show that the thermo-chemical wear is the basic wear mechanism of the diamond cutting tool.