Sang-Soo Noh

The Fabrication by using Surface MEMS of 3C-SiC Micro-heaters and RTD Sensors and their Resultant Properties

The electrical properties and the microstructure of nitrogen-doped poly 3C-SiC films used for micro thermal sensors were studied according to different thicknesses. Poly 3C-SiC films were deposited by LPCVD (low pressure chemical vapor deposition) at 900C with a pressure of 4 torr using SiH2Cl2 (100%, 35 sccm) and C2H2 (5% in H2, 180 sccm) as the Si and C precursors, and NH3 (5% in H2, 64 sccm) as the dopant source gas. The resistivity of the poly SiC films with a 1,530 A thickness was 32.7 Ω-cm and decreased to 0.0129 Ω-cm at 16,963 A. The measurement of the resistance variations at different thicknesses were carried out within the 25C to 350C temperature range. While the size of the resistance variation decreased when the films thickness increased, the linearity of the resistance variation improved. Micro heaters and RTD sensors were fabricated on a Si3N4 membrane by using poly 3C-SiC with a 1um thickness using a surface MEMS process. The heating temperature of the SiC micro heater, fabricated on 250 μmx250 μm Si3N4 membrane was 410C at an 80 mW input power. These 3C-SiC heaters and RTD sensors, fabricated by surface MEMS, have a low power consumption and deliver a good long term stability for the various thermal sensors requiring thermal stability.

Characteristics of Polycrystalline β-SiC Films Deposited by LPCVD with Different Doping Concentration

The physical and electrical properties of polycrystalline -SiC were studied according to different nitrogen doping concentration. Nitrogen-doped SiC films were deposited by LPCVD(1ow pressure chemical vapor deposition) at and 2 torr using (35 sccm) and in (180 sccm) as the Si and C precursors, and in (20-100 sccm) as the dopant source gas. The resistivity of SiC films decreased from with of 20 sccm to with 100 sccm. The surface roughness and crystalline structure of -SiC did not depend upon the dopant concentration. The average surface roughness for each sample 19-21 nm and the average surface grain size is 165 nm. The peaks of SiC(111), SiC(220), SiC(311) and SiC(222) appeared in polycrystalline -SiC films deposited on substrate in XRD(X-ray diffraction) analysis. Resistance of nitrogen-doped SiC films decreased with increasing temperature. The variation of resistance ratio is much bigger in low doping, but the linearity of temperature dependent resistance variation is better in high doping. In case of SiC films deposited with 20 sccm and 100 sccm of , the average of TCR(temperature coefficient of resistance) is -3456.1 ppm/ and -1171.5 ppm/, respectively.

A Study of Properties of 3C-SiC Films deposited by LPCVD with Different Films Thickness

The electrical properties and microstructure of nitrogen-doped poly 3C-SiC films were studied according to different thickness. Poly 3C-SiC films were deposited by LPCVD(low pressure chemical vapor deposition) at and 4 Torr using (100 %, 35 sccm) and (5 % in , 180 sccm) as the Si and C precursors, and (5 % in , 64 sccm) as the dopant source gas. The resistivity of the 3C-SiC films with of thickness was and decreased to at . In XRD spectra, 3C-SiC is so highly oriented along the (1 1 1) plane at

Nitrogen Doped Polcrystalline 3C-Sic Films Deposited by LPCVD for MEMS Applications

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Characteristics of Surface Micromachined Capacitive Pressure Sensors for High Temperature Applications

This paper reports our latest results in developing and characterizing low-stress, heavily- nitrogen-doped polycrystalline 3C-silicon carbide (poly-SiC) films by low pressure chemical vapor deposition. Deposition pressure and NH3 gas concentration are used to control residual stress, stress gradient and conductivity at a deposition temperature of 900degC using SiH2O2 (100%) and C2H2 (5% in H2) as the Si and C precursors. The residual stress is tensile and increases from near zero to near a maximum of 250 MPa with increasing doping concentration; the resistivity decreases from 0.14 Omega-cm to 0.006 Omega-cm in the same doping concentration range. The average TCR decreases from -2050.3 ppm/degC to -1957.0 ppm/degC over approximately the same doping concentration range. The Youngs modulus of the films is estimated at 330 GPa, assuming a Poissons ration of 0.163 for poly-SiC.

The Deposition and Characteristics of Ni Thin Films according to Annealing Conditions for the Application of Thermal Flow Sensors

This paper reports the fabrication and characterization of surface micromachined poly 3C-SiC capacitive pressure sensors on silicon wafer operable in touch mode and normal mode for high temperature applications. FEM(finite elements method) simulation has been performed to verify the analytical mode. The sensing capacitor of the capacitive pressure sensor is composed of the upper metal and the poly 3C-SiC layer. Measurements have been performed in a temperature range from 25°C to 500°C. Fabrication process of designed poly 3C-SiC touch mode capacitive pressure sensor was optimized and would be applicable to capacitive pressure sensors that are required high precision and sensitivity at high pressure and temperature.

Characteristics of CrOx Thin-films for High Precision Resistors

In this work, Ni thin films with different thickness from were deposited for the application of micro thermal flow sensors by a magnetron sputtering and oxidized through annealing at with increasing annealing time. The initial variation of resistivity decreased radically with increasing films thickness, then gradually stabilizes as the thickness increases. The resistivity of Ni thin films with increased suddenly with increasing annealing time at , then gradually stabilizes as the thickness increases after the annealing time 9 h. In case of films, the average of TCR values, measured for the operating temperature range of , were , respectively. Because of their high resistivity and very linear TCR, Ni oxide thin films are superior to pure Ni and Pt thin films for flow and temperature sensor applications.

Characteristics of chromium oxide thin-films for high temperature piezoresistive sensors

This paper presents characteristics of CrOx thin-film, which were deposited on O wafer by DC reactive magnetron sputtering in an argon-oxide atmosphere for high temperature applications. The present paper deals with a study of the technological characteristics of thin film resistors to provide a control in obtaining temperature coefficients of resistance of given value. The optimized condition of CrOx thin-film were thickness range of 2500 and annealing condition(350 , 1 hr) in oxide partial pressure(3.510 torr). Under optimum conditions, the CrOx thin-films is obtained a high resistivity, p

Formation of nickel oxide thin film and analysis of its electrical properties

This paper present characteristics of chromium oxide thin-film as piezoresistive sensors, which were deposited on Si substrates by DC reactive magnetron sputtering in an argon-Oxide atmosphere for high temperature applications. The chemical composition, physical and electrical properties and thermal stability ranges of the sensing elements have studied. thin films with a linear gauge factor(GF15), high electrical resistivity (

A study of electrical properties and microstructure of nitrogen-doped poly-SiC films deposited by LPCVD

Ni oxide thin films with thermal sensitivity superior to Pt and Ni thin films were formed through annealing treatment after Ni thin films were deposited by a r.f. magnetron sputtering method. Resistivity values of Ni oxide thin films were in the range of to according to the degree of Ni oxidation. Also temperature coefficient of resistance(TCR) values of Ni oxide thin films depended on the degree of Ni oxidation from 2,188 ppm/ to 5,630 ppm/ in the temperature range of . Because of the high linear TCR and resistivity characteristics, Ni oxide thin films exhibit much higher sensitivity to flow and temperature changes than pure Ni thin films and Pt thin films.