Polycrystalline 3C-SiC Research Articles

Growth and characteristics of polycrystalline 3C–SiC films for extreme environment micro/nano-electromechanical systems

This paper presents the growth conditions, physical, chemical, mechanical and optical characteristics of polycrystalline 3C–SiC films for extreme environment micro/nano-electromechanical systems (M/NEMS). The growth of the polycrystalline 3C–SiC thin film on oxidized Si wafers was carried out by using atmospheric pressure chemical vapor deposition (APCVD) with a single-precursor of hexamethyldisilane (HMDS: Si 2(CH 3) 6). The growth temperature and the HMDS flow rate were adjusted from 1000 to 1200 °C and from 6 to 8 sccm, respectively. The effect of H 2 carrier gas addition was also evaluated to reduce surface roughness and improve mechanical properties. The grown polycrystalline 3C–SiC films grown in this work had very good crystal quality without twins, defects, or dislocations. Therefore, it is expected to have applications in harsh environment, RF and bio M/NEMS devices.

Design and Performance of an LPCVD Reactor for the Growth of 3C-Silicon Carbide

This paper discusses the design of a low pressure chemical vapor deposition (LPCVD) reactor and growth of β silicon carbide (3C-SiC) thin films on Si. The reactor’s hot-zone configuration radiatively couples the graphite heater (no physical contact) to Si substrates with realized temperatures . We implemented a four-stage growth procedure using silane and propane precursors and hydrogen as the carrier gas. Temperatures, pressures, and flows varied from , from , and from during growth, respectively. Growth of 3C-SiC was confirmed using X-ray diffraction (XRD) with the observation of a (200) peak located at 41.4°. Activation energies of 21.5 and were calculated for the kinetically and mass-transport-limited regimes for polycrystalline 3C-SiC growth. The polycrystalline 3C-SiC films with fewest defects and smallest XRD full width at half-maximum were deposited at with a growth rate of using flow rates of , , and of (conc. 1.16%). The composition of the films measured by X-ray photoelectron spectroscopy shows that the films are slightly carbon rich with oxygen as the main source of contamination. Voids were observed at the film–substrate interface for samples grown at high precursor concentrations.

Microstructure and infrared spectral properties of porous polycrystalline and nanocrystalline cubic silicon carbide

We investigated the structural and infrared spectral properties of porous polycrystalline 3C-SiC and 3C-SiC nanoparticles produced via electrochemical method. The porous sample consisted of parallel nanowires with periodic beadlike structures. It exhibited infrared spectral features quite different from that of single crystal. The 3C-SiC crystallites with an average size of 4 nm showed simple surface chemistry with the surfaces well passivated by dissociation of surrounding water molecules. Our result explains the distinctive optical properties in porous polycrystalline and nanocrystalline 3C-SiC and reveals the crucial conditions for quantum confinement photoluminescence to arise.

Residual stress characterization of polycrystalline 3C-SiC films on Si(100) deposited from methylsilane

Polycrystalline 3C-SiC thin films are deposited on 100 mm Si(100) wafers via low pressure chemical vapor deposition from the precursor methylsilane in the temperature range of 700–850 °C. Residual stress, strain, and strain gradient are characterized as functions of deposition pressure, temperature, and dichlorosilane as an additional silicon source. By optimizing the deposition parameters, the residual stress is found to decrease from 1377±10 to 196±19 MPa. The low stress film exhibits a strain of 3.4×10−4, corresponding to Young’s modulus of 455 GPa, and strain gradient of −8×10−4 μm−1. The analysis suggests that the change in stress values is due to a combination of effects, in particular, thermal mismatch, grain size effect, and chemical composition.

Pd/다결정 3C-SiC 쇼트키 다이오드형 수소센서의 제작과 그 특성

This paper describes the fabrication and characteristics of Schottky micro hydrogen sensors for high temperatures by using polycrystalline(poly) 3C-SiC thin films grown on Si substrates with thermal oxide layer using APCVD. Pd/poly 3C-SiC Schottky diodes were made and evaluated by I-V and C-V measurements. Electric current density and barrier height voltage were and 0.58 eV, respectively. These devices could operate stably at about 400 . The characteristics of implemented sensors have been investigated in terms of sensitivity, linearity of response, response rate, and response time. Therefore, from these results, Pd/poly 3C-SiC Schottky devices have very high potential for high temperature sensor applications.

Grain size control of (111) polycrystalline 3C-SiC films by doping used as folded-beam MEMS resonators for energy dissipation

This manuscript presents an analysis of the energy dissipation mechanisms in microelectromechanical systems (MEMS)-based, flexural-mode polycrystalline silicon carbide (SiC) lateral resonators. The grain structure with columnar (111) polycrystalline 3C-SiC was unintentionally and intentionally doped by low pressure chemical vapor deposition (LPCVD). Device testing was conducted using a transimpedance amplifier-based circuit to measure the total quality factor. It was found that thermoelastic damping (TED) in SiC MEMS-based lateral resonators contributes only in a small way to the overall energy dissipation in these devices. In contrast, the dominant material property appears to be the grain size for lightly and heavily doped film, with smaller grain sizes correlating to higher solid internal losses. The data suggest that conductivity does not play a direct role in determining the quality factor despite the fact that an electrical measurement technique was used. In fact, the lowest quality factors were associated with the lowest resistivities.

다결정 3C-SiC 마이크로 공진기의 온도특성

This paper describes the temperature characteristics of polycrystalline 3C-SiC micro resonators. The <TEX>$1.2{\mu}m$</TEX> and <TEX>$0.4{\mu}m$</TEX> thick polycrystalline 3C-SiC cantilever and doubly clamped beam resonators with <TEX>$60{\sim}100{\mu}m$</TEX> lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonance was measured by a laser vibrometer in vacuum at temperature range of <TEX>$25{\sim}200^{\circ}C$</TEX>. The TCF(Temperature Coefficient of Frequency) of 60, 80 and 100 On long cantilever resonators were -9.79, -7.72 and -8.0 ppm/<TEX>$^{\circ}C$</TEX>. On the other hand, TCF of 60, 80 and <TEX>$100{\mu}m$</TEX> long doubly clamped beam resonators were -15.74, -12.55 and -8.35 ppm/<TEX>$^{\circ}C$</TEX>. Therefore, polycrystalline 3C-SiC resonators are suitable with RF MEMS devices and bio/chemical sensor applications in harsh environments.

양단이 고정된 빔형 다결정 3C-SiC 마이크로 공진기의 제작과 그 특성

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with <TEX>$60{\sim}100{\mu}m$</TEX> lengths, <TEX>$10{\mu}m$</TEX> width, and <TEX>$0.4{\mu}m$</TEX> thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the <TEX>$60{\sim}100{\mu}m$</TEX> long cantilevers, the fundamental frequency appeared at <TEX>$373.4{\sim}908.1\;kHz$</TEX>. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

Surface acoustic wave characteristics of AlN thin films grown on a polycrystalline 3C-SiC buffer layer

In this study, AlN thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) applications using a pulsed reactive magnetron sputtering system. AFM, XRD and FT-IR were used to analyze structural properties and the morphology of the AlN/3C-SiC thin film. Suitability of the film in SAW applications was investigated by comparing the SAW characteristics of an interdigital transducer (IDT)/AlN/3C-SiC structure with the IDT/AlN/Si structure at 160 MHz in the temperature range 30–150 °C. These experimental results showed that AlN films on the poly (1 1 1) preferred 3C-SiC have dominant c-axis orientation. Furthermore, the film showed improved temperature stability for the SAW device, TCF = −18 ppm/°C. The change in resonance frequency according to temperature was nearly linear. The insertion loss decrease was about 0.033 dB/°C. However, some defects existed in the film, which caused a slight reduction in SAW velocity.

Single Crystal and Polycrystalline 3C-SiC for MEMS Applications

Cantilever resonators have been fabricated from two types of materials, single crystal and polycrystalline 3C-SiC films. The films have been grown in a hot-wall chemical vapor deposition reactor on 100 mm diameter p-type boron-doped (100) Si wafer without rotation of the wafer. The crystal structure of the films have been accessed with X-ray diffraction. The cantilever devices have been fabricated using a one-step etch and release process; the beam length has been varied between 50 and 200 µm. Resonant frequencies in the range 110 KHz – 1.5 MHz and 50 – 750 KHz have been obtained for single crystal and polycrystalline SiC devices, respectively. Furthermore, the experimental resonance frequencies have been used to calculate the Young’s Modulus E for the two different types of SiC. The single crystal SiC, possessing a very high Young’s Modulus (446 GPa), should be an optimal material for RF-MEMS applications.

3C-SiC Films on Si for MEMS Applications: Mechanical Properties

Single crystal 3C-SiC films were grown on (100) and (111) Si substrate orientations in order to study the resulting mechanical properties of this material. In addition, poly-crystalline 3C-SiC was also grown on (100)Si so that a comparison with monocrystaline 3C-SiC, also grown on (100)Si, could be made. The mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates were measured by means of nanoindentation using a Berkovich diamond tip. These results indicate that polycrystalline SiC thin films are attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging. MEMS cantilevers and membranes fabricated from a 2 µm thick single crystal 3C-SiC grown on (100)Si under similar conditions resulted in a small degree of bow with only 9 µm of deflection for a cantilever of 700 µm length with an estimated tensile film stress of 300 MPa. Single crystal 3C-SiC films on (111)Si substrates have the highest elastic and plastic properties, although due to high residual stress they tend to crack and delaminate.

Structural and Electrical Properties of Poly-3C-SiC Layer Obtained from P Ion Implanted 4H-SiC

We investigate the structural and electrical properties of polycrystalline 3C-SiC obtained from P ion implanted 4H-SiC with the box-shaped doping profile (NP: 6 x 1020/cm3, thickness: 400 nm, ion dose: 1.6 x 1016/cm2, room temperature). RBS measurement reveals that the highly defective region is formed by P ion implantation, which remains even after annealing at 1700 oC. X-TEM observation shows the P ion induced amorphous layer is recrystallized to twinned-3C-SiC. After annealing at 1300 oC, a sheet resistance of 950 /sq. and sheet carrier concentration of 1 x 1015/cm2 was obtained. By increasing the annealing temperature from 1500 to 1700 oC, the sheet resistance was drastically decreased to about 200 /sq., while there was a small change in the sheet carrier concentration. For the sample annealed at 1700 oC, the electrical activity of the P impurity was estimated to be about 10 % which is comparable to the case of hot implanted sample.

Low Temperature Growth of 3C-SiC Film on Si (111) by Plasma Assisted CVD

In order to demonstrate the formation of 3C-SiC film on Si (111) at low substrate temperature, the effects of C3H8 on the crystallinity of the films on Si (111) have been investigated by changing the flow rate of C3H8 at the substrate temperature of 850 °C. Oriented polycrystalline 3C-SiC film grew under the C/Si of 3 – 5 with a-C. It is suggested that etching effects of growing surface by hydrogen radicals generated from C3H8 decomposition is lowered by lowering the substrate temperature. The crystallinity has been investigated by reflection electron diffraction (RED) and a X-ray diffraction (XRD). The thickness and the surface roughness of the films were investigated by an ellipsometric measurement.

APCVD로 in-situ 도핑된 다결정 3C-SiC 박막의 기계적 특성

This paper describes the mechanical properties of poly (Polycrystalline) 3C-SiC thin films with <TEX>$N_2$</TEX> in-situ doping. In this work, the poly 3C-SiC film was deposited by APCVD (Atmospheric Pressure Chemical Vapor Deposition) method using single-precursor HMDS (Hexamethyildisilane: <TEX>$Si_2(CH_3)_6)$</TEX> at <TEX>$1200^{\circ}C$</TEX>. The mechanical properties of doped poly 3C-SiC thin films were measured by nono-indentation according to the various <TEX>$N_2$</TEX> flow rate. In the case of 0 sccm <TEX>$N_2$</TEX> flow rate, Young's Modulus and hardness were obtained as 285 GPa and 35 GPa, respectively. Young's Modulus and hardness were decreased according to increase of <TEX>$N_2$</TEX> flow rate. The crystallinity and surface roughness was also measured by XRD (X-Ray Diffraction) and AFM (Atomic Force Microscopy), respectively.

Room-Temperature Wet Etching of Polycrystalline and Nanocrystalline Silicon Carbide Thin Films with HF and HNO3

Polycrystalline 3C-SiC films deposited using low-pressure chemical vapor deposition from the precursors 1,3-disilabutane and dichlorosilane (DCS) are etched at room temperature in a mixed acid solution consisting of a 1:1 mixture of . DCS flow rate fractions from 0 to 0.47, which yield a range of films with varying grain sizes, are examined. Etch rates vary from for smaller grained films to for larger grained films. A kinetic model of the etch rate with first-order dependence on free silicon concentration and inverse power-law dependence on grain size is developed that fits the data well. The change in roughness of most polycrystalline SiC films is nominal upon etching; however, films deposited with 0.16 DCS fraction exhibit an increase in roughness accompanied by the exposure of larger grains at the etched surface. Furthermore, films deposited without DCS exhibit an increase in roughness accompanied by the formation of deep “nanocraters” on the surface of individual grains. The room-temperature wet-etch capability thus presented enables new process flows for the realization of micro- and nanoelectromechanical system devices for harsh environments.

Thickness-Dependant Electrical Characteristics of Nitrogen-Doped Polycrystalline 3C-SiC Thin Films Deposited by LPCVD

AbstractThe effect of film thickness on the electrical resistivity of heavily-nitrogen-doped polycrystalline SiC (poly-SiC) thin films is investigated. The resistivity of poly-SiC thin films decreases by a factor of ˜7 for thickness increasing from 100 nm-thick to 1.78 μm-thick; the resistivity begins to stabilize as thickness approaches 1 μm. The increased resistivity for the thinner films is shown to be related to the grain boundary effect. Secondary ion mass spectrometry indicates a nitrogen concentration of 9×1020 atoms/cm3 in the films. However, Hall measurements reveal that only 45% of the dopants are electrically active in the 100 nm-thick film. The percentage of active dopants rises to 80% when film thickness increases to 680 nm. From the studies of surface roughness and microstructure, it is seen that small grains are formed at the initial stage of deposition, which then grow into larger columnar grains as film thickness increases. The presence of a large density of grain boundaries and limited grain growth for the very thin films contribute to increased electrical resistivity from increased trapped mobile carriers and reduced carrier mobility. The free carrier trapping phenomenon can further be observed in the temperature-dependence of resistance measurement.

다결정 SiC 마이크로 공진기의 제작과 그 특성

This paper describes the resonant characteristics of polycrystalline SiC micro resonators. The thick polycrystalline 3C-SiC cantilevers with different lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonance was measured by a laser vibrometer in vacuum at room temperature. For the long cantilevers, the fundamental frequency appeared at . The and long cantilevers have second mode resonant frequency at 857.5.kHz and 1.14.MHz, respectively. Therefore, polycrystalline 3C-SiC resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

Fabrication of beam resonators from hot-wall chemical vapour deposited SiC

Single crystal and polycrystalline 3C–SiC have been grown in a hot-wall chemical vapour deposition reactor on 100 mm diameter p-type boron-doped (1 0 0) Si wafer. The crystal structure of the films has been determined by X-ray diffraction. Moreover, cantilever resonators have been fabricated from the two grown 3C–SiC films using a one-step dry etch and release process. The designed beam length has been varied between 50 and 200 μm. Resonant frequencies in the range between 110 kHz–1.5 MHz and 50–750 kHz have been obtained for single crystal and polycrystalline SiC devices, respectively. Furthermore, the experimental resonance frequencies have been used to calculate Young’s Modulus E for both types of SiC. The single crystal SiC has shown a relatively high Young’s Modulus (446 GPa) and should be an optimal material for RF–MEMS applications.

Design of Polycrystalline 3C-SiC Micro Beam Resonators with Corrugation

On the purpose of increasing resonant frequency without sacrificing quality factor as well as much decreasing dimensions, corrugated micro beam resonator based on polycrystalline 3C-SiC films is the applicable solution. In this work, appropriate corrugated structure is suggested to increase resonant frequency of resonators. Micro beam resonators based on 3C-SiC films which have a two-side corrugation along the length of beams were simulated by finite element method and compared to a same-size flat rectangular. With the dimension of 36x12x0.5 , the flat cantilever has resonant frequency of 746 kHz. Meanwhile, with this size but corrugation width of 6 and depth of 0.4 , the corrugated cantilever reaches the resonant frequency at 1.252 MHz.

Electrical and Mechanical Characterization of Doped and Annealed Polycrystalline 3C-SiC Thin Films

+Deposition of doped polycrystalline 3C-SiC thin films from the precursors 1,3-disilabutane (DSB) and dichlorosilane (DCS), and the dopant precursor ammonia is investigated in a large-scale low-pressure chemical vapor deposition (LPCVD) reactor for micro- and nanoelectromechanical systems (M/NEMS) applications. Films deposited from only DSB and have residual stresses in excess of tensile and resistivity values of . Addition of DCS yields films that exhibit mechanical and electrical properties more favorable for M/NEMS devices. For films deposited with DCS, electrical resistivity varies between for undoped, as-deposited films to for films doped with nitrogen. Residual stress of films deposited from DSB, DCS, and varies little for as-deposited films with different doping concentrations; however, annealing in an argon ambient shifts residual stress toward, and in some cases, into the compressive regime. The strain gradient, which is less than in magnitude for all as-deposited films from DSB, DCS, and , shifts to large negative values in excess of upon annealing for at in an argon ambient. Two sources of stress shift with annealing are identified, namely oxygen diffusion and a change in N atom bonding.