Gwiy Sang Chung

Raman Characteristics of Poly 3C-SiC Thin Films Deposited on AlN Buffer Layer

This paper presents the Raman scattering characteristics of poly 3C-SiC thin films deposited on AlN buffer layer by atmospheric pressure chemical vapor deposition (APCVD) using hexamethyldisilane (MHDS) and carrier gases (Ar + H2). The Raman spectra of SiC films deposited on AlN layer of before and after annealings were investigated according to the growth temperature of 3C-SiC. Two strong Raman peaks, which means that poly 3C-SiC admixed with nanoparticle graphite, were measured in them. The biaxial stress of poly 3C-SiC/AlN was calculated as 896 MPa from the Raman shifts of 3C-SiC deposited at 1180 °C on AlN of after annealing.

Effects of 3C-SiC Intermediate Layer on the Properties of AlN Films Grown on SiO2/Si Substrate

Aluminum nitride thin films were deposited on polycrystalline 3C-SiC intermediate layer by pulsed reactive magnetron sputtering system. Characteristics of AlN/SiC structures were investigated experimentally by means of FE-SEM, AFM, X-ray diffraction, and FT-IR. The columnar structure of AlN thin films was observed by FE-SEM. The surface roughness of AlN films on 3C-SiC layer was measured using AFM. X-ray diffraction pattern of AlN films on SiC layers highly were oriented as (002). Full width of half maximum (FWHM) of the rocking curve around (002) reflections was 1.3°. It was determined from infrared absorbance spectrum that the residual stress of AlN thin films grown on SiC layers was almost free. The presented results show that AlN thin films on 3C-SiC buffer layers can be used for various applications.

Characteristics of Porous 3C-SiC Thin Films Formed with Nitrogen Doping Concentrations

This paper describes the characteristics of porous 3C-SiC with in-situ N-doping concentrations. Polycrystalline (poly) 3C-SiC thin films were deposited on p-type Si (100) substrates by APCVD using hexamethyildisilane (HMDS: Si2(CH3)6). The porous 3C-SiC (pSiC) was achieved by anodized with 380 nm UV-LED. The characteristics of the N2 doped pSiC were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and photo luminescence (PL). Average pore diameter is about 50 nm and etched area was increased with N2 doping rate. These results are attributed to decrease the crystallinity by N2 doping. The band gaps of poly 3C-SiC films and porous 3C-SiC films were 2.5 eV and 2.7 eV, respectively.

Effect of In Situ Doped Nitrogen Concentrations on the Characteristics of Poly 3C-SiC Micro Resonators

This paper describes the characteristics of polycrystalline 3C-SiC micro resonators with 3 ×1017 - 1×1019 cm-3 in-situ N-doping concentrations. In this work, the 1.2 μm thick cantilevers and the 0.4 μm thick doubly-clamped beam micro resonators with various lengths were implemented using in-situ doping poly 3C-SiC thin films. The characteristics of the poly 3C-SiC micro resonators were evaluated using quartz actuator and optical read-out vibrometer under vacuum conditions at room temperature. The resonant frequencies of the SiC micro resonators decreased with doping concentrations owing to the reduction of the Youngs modulus of the poly 3C-SiC thin films. It was confirmed that the resonant frequencies of the poly 3C-SiC micro- resonators are controllable by adjusting the doping concentrations.

Fabrication and Characteristics of Micro Heaters Based on Polycrystalline 3C-SiC for High Temperature and Voltage

This paper describes fabrication and properties of polycrystalline 3C-SiC micro heaters built on AlN(0.1 μm)/3C-SiC(1.0 μm) suspended membranes using surface micromachining technology. 3C-SiC and AlN semiconductors which have a large energy band gap and very low lattice mismatch were used as sensors in harsh environment micro electromechanical system (MEMS) applications in this work. The 3C-SiC thin film was simultaneously used as a resistance of temperature detector (RTD) and micro heater for detecting heated temperature correctly. The thermal coefficient of resistance (TCR) of the implemented 3C-SiC RTD is about -5200 ppm/°C in the temperature range from 25°C to 50°C and -1040 ppm/°C at 500°C. The 3C-SiC micro heater generates about 500°C of heat at 10.3 mW. Moreover, 3C-SiC micro heaters stand at higher applied voltages than case of Pt micro heaters.

Mechanical Properties of Poly 3C-SiC Thin Films According to Carrier Gas (H2) Concentration

This paper presents the mechanical properties of 3C-SiC thin film according to 0, 7, and 10 % carrier gas (H2) concentrations using Nano-Indentation. When carrier gas (H2) concentration was 10 %, it has been proved that the mechanical properties, Young’s Modulus and Hardness, of 3C-SiC are the best of them. In the case of 10 % carrier gas (H2) concentration, Young’s Modulus and Hardness were obtained as 367 GPa and 36 GPa, respectively. When the surface roughness according to carrier gas (H2) concentrations was investigated by AFM (atomic force microscope), when carrier gas (H2) concentration was 10 %, the roughness of 3C-SiC thin was 9.92 nm, which is also the best of them. Therefore, in order to apply poly 3C-SiC thin films to MEMS applications, carrier gas (H2) concentration’s rate should increase to obtain better mechanical properties and surface roughness.

Characteristics of Polycrystalline 3C-SiC Thin Films Grown on AlN Buffer Layer by CVD

This paper describes the characteristics of poly (Polycrystalline) 3C-SiC grown on SiO2 and AlN buffers, respectively. The crystallinity and the bonding structure of poly 3C-SiC grown on each buffer layer were investigated according to various growth temperatures. The crystalline quality of poly 3C-SiC was improved from resulting in decrease of FWHM (Full width half maximum) of XRD and FT-IR by increasing the growth temperature. The minimum growth temperature of poly 3C-SiC was 1100 °C. The surface chemical composition and the electron mobility of poly 3C-SiC grown on each buffer layer were investigated by XPS and Hall Effect. The chemical compositions of surface of poly 3C-SiC grown on SiO2 and AlN were not different. However, their electron mobilities were 7.65 ㎝2/V.s and 14.8 ㎝2/V.s, respectively. Therefore, since the electron mobility of 3C-SiC/AlN was two times higher than that of 3C-SiC/SiO2, AlN is a suitable material, as buffer layer, for SiC growth with excellent crystalline quality.

Etching Characteristics of Polycrystalline 3C-SiC Films Using Enhanced RIE

This paper describes magnetron reactive ion etching (RIE) characteristics of polycrystalline (poly) 3C-SiC thin films grown on thermally oxidized Si substrates by atmospheric pressure chemical vapor deposition (APCVD). The best vertical structures were obtained by the addition of 40 % O2, 16 % Ar, and 44 % CHF3 reactive gas at 40 mTorr of chamber pressure. Stable etching was achieved at 70 W and the poly 3C-SiC was undamaged. These results show that in a magnetron RIE system, it is possible to etch SiC with lower power than that of the commercial RIE system. Therefore, poly 3C-SiC etched by magnetron RIE has the potential to be applied to micro/nano electro mechanical systems (M/NEMS).

Characteristics of polycrystalline 3C-SiC thin films grown on thermal oxided Si wafers by single precursor hexamethyldisilane

This paper presents the growth conditions and characteristics of polycrystalline (poly) 3C-SiC thin films for micro/nano-electromechaical systems (M/NEMS) applications. The growth of the poly 3C-SiC thin film on oxided Si wafers was accomplished by APCVD using single precursor hexamethyldisilane (HMDS: Si2(CH3)6). Depositions were performed under various temperatures and HMDS flow rates, which were adjusted from 1000 to 1200degC and from 6 to 8 sccm, respectively. Moreover, the effect of the addition of H2 was studied as a means to improve surface roughness. The thermal and mechanical properties of poly 3C-SiC were investigated. The optimal growth conditions for the poly 3C-SiC thin film are a deposition temperature of 1100degC, HMDS flow rate of 8 sccm and a H2 flow rate of 100 sccm.