脉冲激光沉积制备立方AlN薄膜的研究

采用脉冲激光沉积(PLD)方法,在SrTiO3(100)衬底上在650℃、10Pa N2条件下成功制备了立方结构的AlN薄膜.高能电子衍射(RHEED)及X射线衍射(XRD)分析表明立方AlN和SrTiO3的外延关系为AlN[100]∥SrTiO3[100]和AlN(200)∥SrTiO3(100).其AlN(200)衍射峰的摇摆曲线半高宽(FWHM)为0.44°,说明薄膜结晶性能良好.原子力显微镜(AFM)表明外延的立方AlN薄膜表面具有原子级平整度,其表面均方根粗糙度(RMS)为0.674nm.通过X光电子能谱(XPS)分析AlN薄膜表面成分,结果表明AlN薄膜表面没有被氧化.     

中频磁控反应溅射制备c轴择优取向AlN薄膜

通过中频磁控反应溅射,在Si(100)衬底上沉积AlN薄膜,并用X射线衍射、扫描电子显微镜和Raman光谱表征AlN薄膜的微观特征.实验中,研究了氮分压、靶基距、溅射功率对AlN薄膜质量的影响,并优化参数制备高质量的c轴取向的AlN薄膜.结果表明,提高溅射功率、降低靶基距以及降低氮分压,有利于c轴择优取向AlN的生长.在优化条件下制备的AlN薄膜具有高度c轴取向,(002)摇摆曲线的半高宽为5.7°,Raman光谱E2(high)声子峰的FWHM为13.8cm-1.     

偏压对中频反应磁控溅射AlN薄膜结构与性能的影响

采用离子束辅助中频反应磁控溅射技术在单晶硅及YG6硬质合金基体上沉积AlN薄膜,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、显微硬度计、薄膜结合强度划痕试验仪等对薄膜结构及性能进行表征,着重研究了偏压对中频反应溅射沉积AlN薄膜结构和性能的影响.研究结果表明:所制备的AlN薄膜是由AIN相和A(I)相组成的,偏压的增大,有利于薄膜结晶度的提高,AlN沿(100)晶面择优取向增强;同时,随着偏压的增加,所沉积的AlN薄膜致密度和膜/基结合力均显著提高,而膜层沉积速率和膜基复合硬度则呈降低的规律.     

等离子体源增强磁控溅射沉积Al2O3薄膜研究

采用电子回旋共振微波等离子体源增强磁控溅射沉积氧化铝薄膜。X射线光电子谱和X射线衍射分析表明，在600℃沉积温度下，Si（100）基片上获得了亚稳的具有化学计量配比成分、面心立方结构的γ－Al2O3薄膜。薄膜的折射率为1．7，与稳定的α－Al2O3体材料相当。     

衬底温度对磁控溅射氮化铝薄膜组成的影响

采用高纯铝靶和氮/氩混合气氛,在玻璃衬底上用直流反应磁控溅射法制备了AlN薄膜,用X射线光电子能谱(XPS)分析了不同衬底温度下样品的组成.结果表明,AlN薄膜主要含有AlN,存在少量Al2O3及一些其它杂质;随着基片温度的升高,AlN薄膜的纯度提高.     

离子束辅助沉积制备TaN薄膜的X射线衍射分析

利用离子束辅助沉积技术制备TaN薄膜，并对其进行X射线衍射分析。掠入射的X射线衍射分析得出：离子束辅助沉积制备的TaN薄膜是面心立方结构，晶格常数a为0．4405nm。根据X射线衍射分析，用屈服强度表征的TaN薄膜的显微硬度为16～20GPa，与文献上报道的显微硬度值接近。离子束辅助沉积制备的TaN薄膜宏观内应力较小，且都为压应力。晶粒尺寸大约在10nm左右，随着注入离子能量的增加，薄膜晶粒尺寸有长大的趋势。     

离子束辅助真空电弧沉积TiO_(2-x)N_x薄膜及抗菌性能研究

采用离子束辅助真空电弧沉积技术在玻璃衬底上制备了氮掺杂的TiO_2薄膜样品,通过X射线衍射(XRD)、XPS以及UV-Vis分光光度计等测试手段对离子束辅助沉积样品的结构、表面成分及抗菌活性进行了分析,研究了经离子束辅助沉积氮掺杂的TiO_2薄膜的抗菌性能。结果表明:离子束辅助沉积的氮掺杂的TiO_3薄膜为非晶态结构,热处理后向锐钛矿转变,出现(101)面的择优取向。离子束流越大,TiO_(2-x)N_x薄膜红移的越少;抗菌活性随着离子束流的增加而减弱,但离子束辅助沉积的掺氮TiO_2薄膜抗菌活性均比传统真空电弧沉积的薄膜抗菌活性高。离子束辅助沉积的掺氮TiO_2薄膜对大肠杆菌、金黄色葡萄球菌自然光照的抑菌率的抗菌率均可达99.9%以上。     

Al预沉积层对金属有机物化学气相沉积方法在Si衬底上生长AlN缓冲层和GaN外延层的影响

采用金属有机物化学气相沉积法(MOCVD)在硅(Si)衬底制备铝/氮化铝/氮化镓(Al/AlN/GaN)多层薄膜,使用光学显微镜(OM)、原子力显微镜(AFM)、X射线衍射(XRD)等手段表征AlN和GaN薄膜的微观结构和晶体质量,研究了TMAl流量对AlN薄膜和GaN薄膜的形核和生长机制的影响。结果表明,预沉积Al层能促进AlN的形核和生长,进而提高GaN外延层的薄膜质量。TMAl流量太低则预沉积Al层不充分,AlN缓冲层的质量取决于由形核长大的高结晶度AlN薄膜与在气氛中团聚长大并沉积的低结晶度AlN薄膜之间的竞争,AlN薄膜的质量随着TMAl流量的升高而提高,GaN薄膜的质量也随之提高。TMAl流量太高则预沉积Al层过厚,AlN缓冲层的质量取决于由形核长大的高结晶度AlN薄膜与Al-Si回融蚀刻之间的竞争,AlN薄膜的质量随着TMAl流量的升高而降低,GaN薄膜的质量也随之降低。     

高速钢基体离子注氮对c-BN薄膜制备的影响研究

采用射频磁控溅射法在离子注氮的高速钢基体上沉积制备c-BN薄膜,主要研究离子注氮层对c-BN薄膜相结构和内应力的影响;采用各种现代分析方法对沉积的薄膜进行了表征分析,包括傅立叶红外光谱(FTIR)、X射线光电子能谱(XPS)和原子力显微镜(AFM)等分析方法;试验结果表明:高速钢基体上离子注氮有利于立方氮化硼含量的提高和薄膜内应力的降低,同时注氮处理的高速钢基体上沉积的薄膜表面形貌平整,结晶性较好.并采用X射线衍射分析(XRD)对高速钢基体的离子注氮层进行了相结构分析,探索研究了离子注氮层对c-BN薄膜生长的影响.     

离子束辅助脉冲激光沉积硼碳氮薄膜

以烧结B4C为靶材料、在氮离子束辅助下用脉冲激光沉积方法制备了三元化合物硼碳氮（BCN）薄膜.用X光电子谱和傅立叶变换红外谱方法表征了制备的薄膜.结果表明,膜层中包含B-C、N-C、B-N键等复合结构,以B-C-N原子杂化的形式结合成键,而并非各种成分的简单混合.还探讨了成膜过程和相关机理,离子束中的活性氮有效地和脉冲激光对B4C靶烧蚀产生的硼和碳结合成键,氮离子束的辅助还能在一定程度上抑制氧杂质进入膜层,给衬底适当加温有利于提高氮的含量并影响薄膜的化学结构.     

A parametric study of AlN thin films grown by pulsed laser deposition

High quality AlN thin films were grown at 200–450°C on sapphire substrates by laser ablation of Al targets in nitrogen reactive atmosphere. The nitrogen pressure was varied between 10⁻³ and 10⁻¹ mbar. The reactive gas pressure during irradiation and the temperature of the substrate were found to essentially influence the quality of the layers. X-ray diffraction analysis evidenced the formation of highly orientated layers for a very restrictive set of parameters. Other analysis techniques, like X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, optical transmission spectroscopy have been used to evidence the good stoichiometry and purity of the films. The characteristics of these films were compared with those of AlN thin films deposited in similar experimental conditions, on Si (100) and Si (111) substrates.     

Preparation of AlN thin films by nitridation of Al-coated Si substrate

AlN thin films have been grown on Al-coated Si(100) and Si(111) substrates by using nitridation in high-purity nitrogen ambient, where the Al layer was previously deposited on Si by ultra-high vacuum (UHV) electron beam evaporation. The temperature of nitridation was found to play an important role in the formation of AlN films. XRD results showed AlN films formed by nitridation at 1000°C for 30 min exhibited good crystallinity with the preferred orientation of (002) for both Si(111) and Si(100) cases. Other analysis techniques, like Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy have been used to evidence the formation and purity of the AlN films. Scanning electron microscope observations of the films revealed a closely-packed granular texture.     

Effect of microstructure on degradation of AlN films prepared by ion beam assisted deposition

Two kinds of aluminum nitride (AlN) films were prepared by ion beam assisted deposition (IBAD) by changing the nitrogen ion beam energy; one was deposited with a 0.2 keV ion beam, showing a columnar structure, and the other was deposited with a 1.5 keV ion beam, showing a granular structure. The effect of microstructure on degradation of AlN films was studied by immersing them in aqueous HNO₃, HCl, and NaOH solutions at room temperature. Degradation was examined mainly in terms of changes in optical transmittance and surface morphology. After immersion in HNO₃ and HCl solutions, the average transmittance of the columnar film decreased gradually from the beginning of immersion, while that of the granular film maintained the initial level of transmittance for about 60 h immersion in HNO₃ solution and about 80 h immersion in HCl solution. In NaOH solution, both films were detached readily from the substrate and no remarkable difference in the degradation behavior was observed between the two films. It is concluded that the IBAD AlN films with the granular structure show higher durability against aqueous acid solutions than the films with the columnar structure.     

Growth of GaN and AlN thin films by laser induced molecular beam epitaxy

Hexagonal GaN and AlN thin films were grown by laser induced molecular beam epitaxy using Al or Ga metal as target material and N₂as nitrogen source. The films were deposited on sapphire (0001) and SiC (0001) substrates. Epitaxial growth of GaN has been achieved at 730°C and 10⁻³ mbar N₂ pressure. The AlN films were polycrystalline with predominant (0001) orientation.     

超高真空电子束蒸发合成晶态AlN薄膜的研究

用超高真空蒸发Ａｌ膜，结合氮化合处理工艺在Ｓｉ（１００）衬底上制备了ＡｌＮ晶态薄膜，用Ｘ射线衍射，傅立叶变换红外光谱和Ｘ射线光电子能谱等测试分析技术研究了薄膜的微结构特征。结果表明：经过１０００℃分钟氮化处理后，能形成具有（００２）择优取向的ＡｌＮ薄膜。     

Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition

We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ammonia (NH₃). At 185 °C, deposition rate saturated for TMA and NH₃ doses starting from 0.05 and 40 s, respectively. Saturative surface reactions between TMA and NH₃ resulted in a constant growth rate of ~ 0.86 Å/cycle from 100 to 200 °C. Within this temperature range, film thickness increased linearly with the number of deposition cycles. At higher temperatures (≥ 225 °C) deposition rate increased with temperature. Chemical composition and bonding states of the films deposited at 185 °C were investigated by X-ray photoelectron spectroscopy. High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.02 and 396.07 eV, respectively. Films deposited at 185 °C were polycrystalline with a hexagonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray diffraction. High-resolution transmission electron microscopy images of the AlN thin films deposited on Si (100) and glass substrates revealed a microstructure consisting of nanometer sized crystallites. Films exhibited an optical band edge at ~ 5.8 eV and an optical transmittance of > 95% in the visible region of the spectrum.     

The phase and microstructure of CrAlN films deposited by pulsed dc magnetron sputtering with synchronous and asynchronous bipolar pulses

CrAlN films have been deposited from a Cr target and an Al target using pulsed dc magnetron sputtering. The Cr and Al targets were pulsed in asynchronous and synchronous pulsing modes at different pulsing frequencies and duty cycles. The ion energy distributions of the plasma were characterized by a Hiden mass spectrometer. The pulsed plasma contains a wide range of energetic ions. The ion energies depend on the pulsing parameters and the pulsing mode of the two targets. The ion energy and ion flux increased as the pulsing frequency was increased. The plasma exhibited higher ion energies and ion fluxes in the synchronous pulsing mode than those in the asynchronous pulsing mode for the same pulsing frequency and duty cycle. A decrease in the N content and an increase in the Al/(Cr + Al) ratio were observed as the pulsing frequency was increased in both pulsing modes. When the pulsing frequency was increased to 350 kHz, the films deposited in the asynchronous pulsing mode exhibited a NaCl cubic structure, whereas a mixture of the cubic and hexagonal phases was formed in the films deposited in the synchronous pulsing mode. The hardness of the films increased with an increase in the pulsing frequency in the asynchronous pulsing mode. In contrast, a decrease in the hardness was found in the synchronously deposited films as the pulsing frequency was increased due to the formation of hexagonal AlN phase and the stress relaxation in the films.     

氧离子能量对离子束辅助沉积Al2O3薄膜的结构及光学性能的影响

利用氧离子束辅助脉冲反应磁控溅射技术在聚酰亚胺基底上沉积Al2O3薄膜。这项技术在溅射高纯铝靶材的同时利用低能氧离子进行氧化来控制薄膜的化学配比。研究了薄膜沉积过程中离子束辅助的作用以及离子束放电电压对Al2O3薄膜的化学成分、结构、表面形貌、光学性能以及沉积速率的影响。结果发现,离子束放电电压对薄膜的化学成分具有显著影响,当电压增加到200 V,薄膜已基本达到完全化学计量比且薄膜为非晶结构;薄膜表面粗糙度随着离子束放电电压的增加而减小,当电压达到300V时,薄膜具有最小的表面粗糙度;通过对Al2O3薄膜透射谱的测量,分析薄膜的光学特性,获得了薄膜的光学常数随离子束放电电压的变化规律,发现氧离子束辅助沉积的薄膜具有较高的折射系数和较低的消光系数;另外,薄膜的沉积速率在电压增加到300V时达到最大值70 nm/min,是未采用离子束辅助时沉积速率的5倍。     

Ion beam synthesis of aluminium nitride: characterisation of thin AIN layers formed in microelectronics aluminium

Abstract

Buried AlN thin layers have been formed by high dose N⁺ ion implantation into microelectronics grade Al films (containing 1 at.-%Si), which were deposited on Si wafers. The structures obtained have been characterised by spreading resistance measurements, transmission electron microscopy, secondary ion mass spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show the formation of buried dielectric precipitates of crystalline AlN at implantation doses below the threshold and a continuous polycrystalline AlN layer at doses above the threshold. The AlN grains have the wurtzite structure, sizes of about 10–15 nm, and a preferred orientation in relation to the Al matrix, namely, <110>_AIN parallel to <110>_Al. The data also show that, under certain conditions, the main impurities (Si and O) are gettered in the buried layer. Moreover, for thin Al films, the formation of a Si rich surface layer is observed. This surface layer is formed by Si diffusion from the substrate, probably due to the penetration of N⁺ ions into the Si substrate. The distribution and evolution of these impurities and the different phases formed are studied as a function of the thickness and grain size of the Al film, as well as of the annealing processes.

MST/3304