热丝化学气相沉积法低温制备纳米晶态碳化硅薄膜

采用热丝化学气相沉积(HFCVD)技术以甲烷(CH4)和硅烷(SiH4)作为源反应气体在Si(111)衬底上合成了纳米晶态SiC薄膜。通过X射线衍射(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)以及光致发光(PL)检测技术对薄膜的晶体结构、表面形貌和PL特性进行了分析和表征。结果表明，在较低的衬底温度下所沉积的薄膜是由镶嵌于非晶SiC网络中的晶态纳米SiC构成。纳米晶粒平均尺寸约为6nm。室温下用HeCr激光激发样品，观到薄膜发出波长位于400～550nm范围内可见光辐射。     

nc-SiC/SiO_2镶嵌薄膜材料的制备、结构和发光特性

采用二氧化硅/碳化硅复合靶,用射频磁控共溅射技术和后高温退火的方法在Si(111)衬底上制备了碳化硅纳米颗粒/二氧化硅基质(nc-SiC/SiO2)镶嵌结构薄膜材料。用X射线衍射(XRD),傅里叶红外吸收(FTIR),扫描电子显微镜(SEM)和光致发光(PL)实验分析了薄膜的微结构以及光致发光特性。实验结果表明,样品薄膜经高温退火后,部分无定形SiC发生晶化,形成β-SiC纳米颗粒而较均匀地镶嵌在SiO2基质中。以280nm波长光激发薄膜表面,有较强的365nm的紫外光发射以及458nm和490nm处的蓝光发射,其发光强度随退火温度的升高显著增强,发光归结为薄膜中与Si—O相关的缺陷形成的发光中心。     

磁控溅射生长SiC薄膜的拉曼光谱研究

用射频磁控溅射法在Si(100)和玻璃衬底上制备出衬底温度分别为300,450,600℃的碳化硅薄膜,并对薄膜进行了拉曼光谱和原子力显微镜测试分析。结果表明,用溅射法在玻璃衬底上生长出微晶SiC(μc-SiC)薄膜和在Si(100)衬底上生长出立方碳化硅(β-SiC)薄膜。并且薄膜材料的结晶度随着衬底温度的升高而改善。     

衬底温度对微晶硅薄膜沉积与结构特征的影响

采用甚高频等离子体化学气相沉积(VHF-PECVD)技术在不同衬底温度条件下沉积了氢化微晶硅(μc—Si：H)薄膜,并通过光发射谱(OES)测量技术对沉积过程中硅烷(SiH4)等离子体进行了原位监测。结合对样品的沉积速率测量与结构表征,研究了衬底温度对薄膜沉积过程与结构特征的影响。实验结果表明：随着衬底温度的增加,μc—Si：H薄膜结晶体积分数与晶粒的平均尺寸单调增大,而沉积速率则呈现出先增后减的变化。对于当前的沉积系统,优化生长的衬底温度约为210℃,相应的μc-Si：H薄膜沉积速率为0．8nm／s,结晶体积分数与晶粒平均尺寸分别为60％和9nm。     

SiC纳米晶薄膜的制备及发光性质研究

用射频磁控溅射及后退火(800℃、1000℃和1200℃)方法,在Si(111)衬底上制备出了SiC纳米晶(nc-SiC)薄膜。傅立叶变换红外光谱(FTIR)、X射线衍射谱(XRD)及扫描电子显微镜(SEM)形貌像等研究表明,制备出的nc-SiC薄膜具有立方结构;样品经800℃、1000℃退火后,表面的纳米晶粒分别为10nm和20nm左右;而1200℃退火后,样品晶化完全。光致发光(PL)研究表明,nc-SiC薄膜室温条件下发射蓝光,发光峰峰位随退火温度的降低发生蓝移且发光峰强度变大;1000℃退火后样品的发光峰在478nm,800℃退火后发光峰在477nm,800℃退火比1000℃退火的样品发光强度高4倍。     

在Si(111)上脉冲ArF准分子激光淀积晶态定向α-SiC薄膜

报道用脉冲ArF激光烧蚀SiC陶瓷靶,在800℃Si(111)衬底上淀积SiC薄膜,再经920℃真空(10-3Pa)退火处理,制备出晶态α-SiC薄膜.用FTIR、XPS、SEM、XRD、TEM、PL谱等分析方法,研究了薄膜的表面形态、晶体结构、微结构、组成、化学态和光致发光等.结果表明,在920℃较低温度下,SiC薄膜经非晶核化--长大过程,生成了晶态α-SiC(0001)∥Si(111)高度定向外延膜,薄膜内C/Si比约为1.01.表面有污染C及少量氧化态Si和C.室温下用280nm光激发薄膜,在341nm处有较强发光峰,半峰宽45nm,显示出较好的短波发光性质.     

AIN/Si(111)复合衬底上4H-SiC薄膜的异质外延

利用化学气相淀积(CVD)的方法在AlN/Si(111)复合衬底上成功实现了4H-SiC薄膜的异质外延生长,用X射线衍射(XRD)、扫描电子显微镜(SEM)、阴极荧光(CL)等方法对所得样品的结构特征、表面形貌和光学性质进行了表征测量.XRD测量结果显示得到的SiC薄膜的晶体取向单一;室温CL结果表明所得SiC薄膜为4H-SiC,且随着生长温度的升高,SiC薄膜的CL发光效率提高.生长温度、反应气源中C/si比等工艺参数对SiC薄膜的外延生长及其性质影响的研究表明在AIN/Si(111)复合衬底上外延4H-SiC的最佳衬底温度为1230～1270℃,比通常4H-SiC同质外延所需的温度低200～300℃;较为合适的C/Si比值为1.3.     

溅射法制备高取向Pt薄膜的工艺研究

采用射频磁控溅射工艺在SiO2／Si衬底上成功制备了适用于pZT铁电薄膜底电极的180nm厚、沿(111)晶向强烈取向的Pt薄膜。厚约50nm的Ti膜被用作过渡层，以增强Pt薄膜与衬底之间的黏着性。实验表明，在Pt薄膜的制备过程中，较高的衬底温度有利于薄膜晶化，促使Pt薄膜沿(111)晶向择优取向生长。而在薄膜沉积后加入适当的热处理工艺，能有效地提高Pt薄膜的择优取向性，同样可以得到沿(111)晶向强烈取向的Pt薄膜。原子力显微镜分析表明，制得的薄膜结构相对致密，结晶状况良好，晶粒尺寸约为50nm。     

激光脉冲频率对纳米Si晶薄膜形貌的影响

在气压为10 Pa的惰性气体Ar环境下,采用XeCl准分子激光器(波长308 nm),调整激光单脉冲能量密度为4 J/cm2,激光烧蚀电阻率为3000Ω.cm的高纯单晶Si靶,在玻璃或Si衬底上沉积制备了纳米Si晶薄膜。实验中靶和衬底间距离保持为3 cm,对衬底既没有加温也没有冷却。拉曼(Raman)谱测量结果表明,所制备的薄膜中已有纳米Si晶粒形成。保持脉冲总数不变,分别取激光脉冲频率为1 Hz,3 Hz,10 Hz和20 Hz,相应沉积时间约为10 min,3.3 min,1 min和0.5 min,采用扫描电子显微镜(SEM)观察所得样品的表面形貌,不同脉冲频率下的结果比较显示,脉冲频率越大,制备的纳米Si晶薄膜的平均晶粒尺寸就越小,晶粒尺寸分布也越均匀。沉积动力学过程的非线性是导致实验出现该结果的原因。     

硅基AlN薄膜制备技术与测试分析

采用直流磁控反应溅射法,在Si(100),Al/Si(100)和Pt/Ti/Si(100)等多种衬底上制备了用于MEMS器件的AlN薄膜.用XRD和AES对薄膜的结构和组分进行了分析,通过优化工艺参数,得到了提高薄膜择优取向的方法,并分析了不同衬底上AlN晶粒生长的有关机理.制备的AlN薄膜显示出良好的〈002〉择优取向性,摇摆曲线的半高宽达到5.6°.     

High doped MBE Si p–n and n–n heterojunction diodes on 4H-SiC

The physical and electrical properties of heavily doped silicon (5×10¹⁹ cm⁻³) deposited by molecular beam epitaxy (MBE) on 4H-SiC are investigated in this paper. Silicon layers on silicon carbide have a broad number of potential applications including device fabrication or passivation when oxidised. In particular, Si/SiC contacts present several atractive material advantages for the semiconductor industry and especially for SiC processing procedures for avoiding stages such as high temperature contact annealing or SiC etching. Si films of 100 nm thickness have been grown using a MBE system after different cleaning procedures on n-type (0 0 0 1) Si face 8° off 4H-SiC substrates. Isotype (n–n) and an-isotype (p–n) devices were fabricated at both 500 and 900 °C using antimonium (Sb) or boron (B), respectively. X-ray diffraction analysis (XRD) and scanning electronic mircorscope (SEM) have been used to investigate the crystal composition and morphology of the deposited layers. The electrical mesurements were performed to determine the rectifiying contact characteristics and band offsets.     

脉冲激光沉积法制备红外光学SiC薄膜特性研究

采用脉冲激光沉积法在锗基底制备无氢SiC薄膜,研究了激光能量对SiC薄膜显微结构、成分和红外光学性能的影响规律。利用傅里叶红外光谱仪测量了锗基底SiC薄膜样品的红外透射光谱,其在785 cm-1附近有一个强烈Si-C键特征吸收峰,并在红外波数4 000~1 300 cm-1之间具有良好的透过性。通过对透射光谱拟合计算可知:在红外波段2.5~7.7 m之间,SiC薄膜的折射率和消光系数均随着激光能量的增加而增大,折射率大约从2.15上升到2.33,激光能量从400 mJ增加到600 mJ,且当激光能量为400、500 mJ时,消光系数均在10-3量级以内,光学吸收很小。研究表明,SiC薄膜在红外2.5~7.7 m波段是一种优异的光学薄膜材料。     

3英寸半绝缘4H-SiC单晶的研制

报道了采用物理气相传输(PVT)法进行SiC单晶生长方面取得的最新进展,成功研制得到固态微波器件急需的3英寸(75 mm)半绝缘4H-SiC衬底。使用计算机模拟技术,进行了3英寸(75 mm)4H-SiC晶体生长的热场设计,并在此基础上研制出适合3英寸(75 mm)4H-SiC PVT生长的晶体生长设备,采用喇曼光谱对晶体生长表面5点进行测试,结果均为单一的4H晶型,采用非接触电阻率面分布(COREMA)方法测得晶片电阻率为109~1012Ω.cm。微管道缺陷(MPD)测量采用熔融KOH腐蚀法,测得平均微管道密度为104个/cm2,其中晶片的30%区域微管道缺陷小于10个/cm2。使用X射线双晶衍射测试得到其半高宽(FWHM)为31 arcsec,说明所获得的晶体具有良好的结晶完整性。     

Irradiation as a possible method for producing SiC heterostructures

Certain aspects of the physics of heteropolytypic junctions based on silicon carbide are examined. It is known that the introduction of certain impurities into the growth zone during epitaxy of silicon carbide results in the growth of films whose polytype is different from that of the initial substrate. It is also known that these impurities lead to the formation of certain deep centers in the band gap of the conductor. Analysis of published data performed in this paper shows that irradiation of SiC with various charged particles also leads to the formation of these deep centers. It is assumed that under certain experimental conditions transformation of the polytype of the already grown epitaxial SiC structure is possible under the action of irradiation and subsequent annealing. Fiz. Tekh. Poluprovodn. 33, 1102–1104 (September 1999)     

在(111)Si衬底上磁控溅射纳米SiC薄膜的退火效应

用射频磁控溅射法在常温硅衬底上制备出了纳米碳化硅薄膜,并研究了退火温度对薄膜的影响。用傅里叶红外透射谱（FTIR）、x射线衍射（XRD）、x光电子能谱（XPS）及原子力显微镜（AFM）对薄膜样品进行了结构、组分和形貌分析。AFM表明,随着退火温度的升高,碳化硅颗粒尺寸增大;在高于1000℃退火3h后,碳化硅颗粒呈现出勺状拖尾。     

Infrared spectroscopy and transmission electron microscopy of polycrystalline silicon carbide

The polycrystalline structure of silicon carbide was investigated by infrared spectroscopy and transmission electron microscopy (TEM). The films were obtained by annealing in the temperature range 950–1250°C of amorphous silicon carbide films deposited on a silicon substrate by PECVD. The broad absorption band at around 750 cm⁻¹ in the infrared spectrum of amorphous material after annealing at high temperature changes from a Gaussian to a Lorentzian shape, corresponding to the transition from an amorphous to a polycrystalline phase. The SiC peak becomes sharper with increasing the annealing temperature, this effect being related to the growth of crystalline grains. TEM microscopy indicates that the crystallisation occurs homogeneously in the films and the diffraction pattern shows that the film crystallises into cubic 3C–SiC. The distribution of polycrystalline grains as determined by TEM evidences an increase of the grain size with increasing the annealing temperature. A correlation between infrared peak width and mean grain radius has been found.     

Ultra-short pulsed laser deposition and patterning of SiC thin films for MEMS fabrication

A Ti:Sapphire (IR 800-nm) femtosecond (fs) pulsed laser was used to ablate a sputtering grade of silicon carbide (SiC) in an ultra-high vacuum chamber. The laser-induced plasma species were then driven and grown to form 3C-SiC films of about 1 μm thick on single crystal silicon wafers at 20 °C (room temperature) and 500 °C. Scanning electron microscopy, atomic force microscopy, X-ray photoelectron microscopy, X-ray diffraction and nanoindentation were used to characterize the structure, composition, thickness and properties of the SiC films. Results of the femtosecond-pulse laser deposited (fs-PLD) films were compared with those obtained by atmospheric pressure chemical vapor deposition (APCVD) and nanosecond-pulse laser (excimer laser at 248-nm) deposition (ns-PLD). The distinctive features of fs-PLD films are their extremely smooth surfaces, stoichiometry, amorphous structure and low defect density compared to APCVD films, along with better film quality and higher growth rates than ns-PLD films. In addition to film growth studies, a SiC microgripper (to grab 20-μm-sized objects) was micromachined by use of the fs-pulsed laser to demonstrate the utility of ultra-short PLD in SiC-device fabrication.     

SiC薄膜红外及紫外-可见光谱的研究

报道了在单晶Si衬底上采用RF磁控溅射技术异质外延生长SiC薄膜的研究。由傅立叶红外谱用双声子组合法计算出SiC的基本声子能量是TO=0．049eV，LO=O．048eV，TA=0．0045eV，LA=0．0078eV；SiC的所有傅立叶红外吸收峰均可用这些声子能量按不同组合方式得到，并在紫外-可见光谱中，光跃迁引起的吸收或放射的声子的能量也可以用这些基本声子能量按不同方式组合得到。     

Cryogenic Temperature Measurement Using Silicon Carbide-Based Wireless Optical Sensor

Demonstrated is a novel silicon carbide (SiC)-based wireless optical sensor for cryogenic temperatures. The proposed design uses two wavelength processing and free-space optical beam interrogation of a remoted single crystal SiC chip placed in the cryogenic vacuum chamber to enable wireless temperature measurement. Experimental temperature sensing using the proposed sensor is reported from near room temperature to 100 K with an estimated 0.2 K resolution. The sensor uses eye safe laser wavelengths at 1550 and 1540 nm to implement the signal processing to determine the temperature value