Laterally Electrostatically Driven Poly 3C-SiC Folded-Beam Resonant Microstructures

Micromachined comb-drive electrostatic resonators with folded-cantilever beams were designed and fabricated. A combination of Rayleigh＇s method and finite-element analysis was used to calculate the resonant frequency drift as we adjusted the device geometry and material parameters. Three micromachined lateral resonant resonators with different beam widths were fabricated. Their resonant frequencies were experimentally measured to be 64.5,147.2, and 255.5kHz, respectively, which are in good agreement with the simulated resonant frequency. It is shown that an improved frequency performance could be obtained on the poly 3C-SiC based device structural material systems with high Young＇s modulus.

Heteroepitaxial Growth of 3C-SiC Films on Maskless Patterned Silicon Substrates

Heteroepitaxial growth of 3C-SiC on patterned Si substrates by low pressure chemical vapor deposition (LPCVD) has been investigated to improve the crystal quality of 3C-SiC films. Si substrates were patterned with parallel lines, 1 to 10μm wide and spaced 1 to 10μm apart, which was carried out by photolithography and reactive ion etching. Growth behavior on the patterned substrates was systematically studied by scanning electron microscopy (SEM). An air gap structure and a spherical shape were formed on the patterned Si substrates with different dimensions. The air gap formed after coalescence reduced the stress in the 3C-SiC films, solving the wafer warp and making it possible to grow thicker films. XRD patterns indicated that the films grown on the maskless patterned Si substrates were mainly composed of crystal planes with (111) orientation.

Uniformity Investigation in 3C-SiC Epitaxial Layers Grown on Si Substrates by Horizontal Hot-Wall CVD

50mm 3C-SiC epilayers are grown on （100） and （111） Si substrates in a newly developed horizontal lowpressure hot-wall CVD reactor under different growth pressures and flow rates of H_2 carrier gas. The structure,electrical properties, and thickness uniformity of the 3C-SiC epilayers are investigated by X-ray diffraction （XRD） ,sheet resistance measurement, and spectroscopic ellipsometry. XRD patterns show that the 3C-SiC films have excellent crystallinity. The narrowest full widths at half maximum of the SIC（200） and （111） peaks are 0.41° and 0.21°, respectively. The best electrical uniformity of the 50mm 3C-SiC films obtained by sheet resistance measurement is 2.15%. A σ/mean value of ± 5.7% in thickness uniformity is obtained.

Effect of Silicon-on-Insulator Substrate on Residual Strain in 3C-SiC Films

One group of SiC films are grown on silicon-on-insulator （SOI） substrates with a series of silicon-overlayer thickness. Raman scattering spectroscopy measurement clearly indicates that a systematic trend of residual stress reduction as the silicon over-layer thickness decreases for the SOI substrates. Strain relaxation in the SiC epilayer is explained by force balance approach and near coincidence lattice model.

Si上外延的n型3C-SiC欧姆接触研究

用LPCVD在si（111）上异质外延了n型3C-SiC，并在所外延的3C-SiC上蒸发Au／Ti，通过不同温度下的RTA（快速热退火）形成欧姆接触。用两种不同的传输线模型对Ti／3C-SiC欧姆接触的ρc（比接触电阻率）进行测量，在750℃退火后Ti／3C-SiC的ρc达到了最低值为3．68×10^-5Ω·cm^2这满足了应用的要求。AES分析结果还表明由于Ti的氧化，更高温度下的退火会使ρc增大。

LPCVD Growth of 3C-SiC on Si Mesas and SiO2/Si Substrates for MEMS Applications

This paper presents the development of LPCVD growth of 3C-SiC thin films grown on Si mesas and thermally oxidized SiO2 masks over Si with an area of 150 × 100μm^2 and SiO2/Si substrates. The growth has been performed via chemical vapor deposition using SiH4 and C2H4 precursor gases with carrier gas of H2. 3C-SiC films on these substrates were characterized by optical microscopy, X-ray diffraction （ XRD ）, X-ray photoelectron spectroscopy （ XPS ）, scanning electron microscopy （SEM） and room temperature Hall effect measurements. It is shown that there were no voids at the interface between 3C-SiC and SiO2.

Preparation of 50mm 3C-SiC/Si(111) as Substrates Suited for Ⅲ-Nitrides

50mm SiC films with high electrical uniformity are grown on Si(111) by a newly developed vertical low-pressure chemical vapor deposition (LPCVD) reactor.Both in-situ n- and p-type doping of 3C-SiC are achieved by intentional introduction of ammonia and boron into the precursor gases.The dependence of growth rate and surface morphology on the C/Si ratio and optimized growth conditions is obtained.The best electrical uniformity of 50mm 3C-SiC films obtained by non-contact sheet resistance measurement is ±2.58%.GaN films are grown atop the as-grown 3C-SiC/Si(111) layers using molecular beam epitaxy (MBE).The data of both X-ray diffraction and low temperature photoluminescence of GaN/3C-SiC/Si(111) show that 3C-SiC is an appropriate substrate or buffer layer for the growth of Ⅲ-nitrides on Si substrates with no cracks.

High Temperature Characteristics of 3C-SiC/Si Heterojunction Diodes Grown by LPCVD

The high temperature (300～480K) characteristics of the n-3C-SiC/p-Si heterojunction diodes (HJD) fabricated by low-pressure chemical vapor deposition on Si (100) substrates are investigated.The obtained diode with best rectifying properties has 1.8×104 of ratio at room temperature,and slightly rectifying characteristics with 3.1 of rectification ratio is measured at 480K of an ambient temperature .220V of reverse breakdown voltage is acquired at 300K.Capacitance-voltage characteristics show that the abrupt junction model is applicable to the SiC/Si HJD structure and the built-in voltage is 0.75V.An ingenious equation is employed to perfectly simulate and explain the forward current density-voltage data measured at various temperatures.The 3C-SiC/Si HJD represents a promising approach for the fabrication of high quality heterojunction devices such as SiC-emitter heterojunction bipolar transistors.

Si衬底上无坑洞3C-SiC的外延生长研究

在冷壁式不锈钢超高真空系统上，利用低压化学气相淀积（LPCVD）方法在直径为50 mm的单晶Si(100)和Si(111)晶向衬底上生长出了高取向无坑洞的晶态立方相碳化硅（3C-SiC）外延材料，利用反射高能电子衍射（RHEED）和扫描电镜（SEM）技术详细研究了Si衬底的碳化过程、碳化层的表面形貌及缺陷结构，获得了界面平整光滑、没有空洞形成的3C-SiC外延材料，并采用X- 射线衍射（XRD)、双晶X- 射线衍射（DXRD）和霍尔(Hall）测试等技术研究了外延材料的结构和电学特性。

Si(100)衬底上n-3C-SiC／p-Si异质结构研究

利用LPCVD方法在Si(100)衬底上获得了3C-SiC外延膜，扫描电子显微镜(SEM)研究表明3C-SiC／p—Si界面平整、光滑，无明显的坑洞形成。研究了以In和Al为接触电极的3C-SiC／p—Si异质结的I—V，C-V特性及I—V特性的温度依赖关系，比较了In电极的3C-SiC／p—Si异质结构和以SiGe作为缓冲层的3C-SiC／SiGe／p—Si异质结构的I—V特性，实验发现引入SiGe缓冲层后，器件的反向击穿电压由40V提高到70V以上。室温下A1电极3C-SiC／p—Si二极管的最大反向击穿电压接近100V，品质因子为1．95。

Heteroepitaxial Growth and Heterojunction Characteristics of Voids-Free n-3C-SiC on p-Si(100)

Highly oriented voids-free 3C-SiC heteroepitaxial layers are grown on φ50mm Si (100) substrates by low pressure chemical vapor deposition (LPCVD). The initial stage of carbonization and the surface morphology of carbonization layers of Si(100) are studied using reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM). It is shown that the optimized carbonization temperature for the growth of voids-free 3S-SiC on Si (100) substrates is 1100 ℃. The electrical properties of SiC layers are characterized using Van der Pauw method. The I-V, C-V, and the temperature dependence of I-V characteristics in n-3C-SiC-p-Si heterojunctions with AuGeNi and Al electrical pads are investigated. It is shown that the maximum reverse breakdown voltage of the n-3C-SiC-p-Si heterojunction diodes reaches to 220V at room temperature. These results indicate that the SiC/Si heterojunction diode can be used to fabricate the wide bandgap emitter SiC/Si heterojunction bipolar transistors (HBT's).

Raman Investigatins of 3C-SiC Films Grown on Si (100) and Sapphire (0001) by LPCVD

The Raman measurements have been performed with the back-scattering geometry on the SiC films grown on Si(100) and sapphire (0001) by LPCVD. Typical TO and LO phonon peaks of 3C-SiC were observed for all the samples grown on Si and apphire substrates, indicating the epilayers are 3C-SiC polytype. Using a free-standing 3C-SiC film removed from Si(100) as a free-stress sample, the stresses of 3C-SiC on Si(100) and sapphire (0001) were estimated according to the shift of TO and LO phonons.

Improved Epitaxy of 3C-SiC Layers on Si(100) by New CVD/LPCVD System

Single crystalline 3C-SiC epitaxial layers are grown on φ50mm Si wafers by a new resistively heated CVD/LPCVD system, using SiH_4, C_2H_4 and H_2 as gas precursors. X-ray diffraction and Raman scattering measurements are used to investigate the crystallinity of the grown films. Electrical properties of the epitaxial 3C-SiC layers with thickness of 1 ～ 3μm are measured by Van der Pauw method. The improved Hall mobility reaches the highest value of 470cm~2/(V·s) at the carrier concentration of 7.7 * 10~(17)cm~(-3).

Si（001）衬底上APCVD生长3C-SiC薄膜的微孪晶及含量

于2010-11-23批量导入

Si（001）衬底上方形3C-SiC岛的LPCVD生长

于2010-11-23批量导入