富硅二氧化硅薄膜的光致荧光特性研究

【作者】 肖淑娟；

【导师】 薛成山；

【作者基本信息】 山东师范大学 ， 微电子学与固体电子学， 2001， 硕士

【摘要】 含Si的纳米晶粒的SiO₂介电膜又叫富硅二氧化硅薄膜，属于nc-Si薄膜的一种。它的重要特性是在可见光范围内的电致发光和光致发光。它具有稳定性好、工艺重复性好的特点，而且SiO₂作为钝化层和电绝缘层广泛应用在硅器件和集成电路方面。虽然富硅二氧化硅薄膜的发光强度尚有待于提高，但已看出由于它有可能用于制成硅光电器件以及便于实现集成化而受到瞩目。本文详细介绍了纳米硅薄膜的光致发光机制、制备方法、实验设计和测量结果。 本文首先概括介绍纳米硅薄膜的研究现状。人们对采用各种方法在不同衬底表面上制备的高质量的nc-Si:H膜或硅微晶粒镶嵌在各种介质如a-Si:H，SiO₂或Si₃N₄中的介电膜的发光特性进行了深入研究。但是迄今为止，不管是对纳米晶硅薄膜的光致发光还是电致发光。其发光机制尚不清楚，还很难给出一个圆满确切的统一解释。 以Canham为代表的观点认为，多孔硅或纳米硅膜中的可见发光源自于与微晶粒纳米尺寸结构相应的量子限制引起的能隙加宽和载流子从间接跃迁向直接跃迁的转变。另一种观点认为纳米硅薄膜中的可见光发射来自界面或介质层中的发光中心。还有人认为对于镶嵌在SiO₂中的纳米晶粒来说，与氧有关的缺陷可能是导致可见光或蓝绿光发射的主要原因。量子限制/发光中心（QCLC） 详细内容摘要模型是指对干氧化多孔硅，电子－空穴对的光激发发生在纳米硅晶粒和氧化硅中，光激发出的电子和空穴转移到二氧化硅层中及硅与二氧化硅界面上的发光中心（如缺陷、杂质等）上复合而发光。 为了能够制备出具有高质量的硅纳米相材料，国内外许多研究者己尝试了多种生长方法，如①化学气相淀积法，②射频溅射法③硅离子注入S。法等。 第二章介绍我们制备富硅二氧化硅所用的溅射系统。溅射靶的设计、样品制备过程以及组成结构和荧光特性的测量。我们采用配有SY型500W射频电源的JCK－500W型磁控溅射仪来制备hnC／Sic。薄膜。靶材采用h／Sic。复合靶。溅射时，使载有衬底的基片架转动。结构特性采用 X射线衍射仪（XRD）和工R透射谱测量。用960CRT荧光分光光度计测样品的发光谱。 第三章给出了我们的实验结果及其分析情况。用IR透射谱分析样品成分的相关信息。T／1000℃时，显示了ao8 键的伸展模式的两个特征吸收峰。薄膜样品结构模型为 ILMM和 NM两种极端情形的混合态。高温退火后 出－O毛 键的伸展振动模式吸收峰蓝移，实际上表明了；温升引起了系统转变，热力作用使本来分布均匀的ax相长成ncS侣。混合相，其化学反应表示为：St－St刀。。一二 SISi。。＋门－H)Si－O。k二1，2，3〕，温升引起a相 4”““4“一、－··和 SIO，的形成。 室温测量PL谱，激发波长为365urn，在445n－m处有一发光 －4－ 详纫呐容摘要带。峰位不随T。改变，强度随T。升高而增强。我们的实验中，随T。升高，nc毛尺寸大小虽然改变，但PL峰位不变，未退火样品也有蓝光发射。因此PL不能用量子限制效应解释。我们的样品的蓝光发射也不来源于氧空位，首先因为我们的激发能量3．4ev小于sev，不能激发民带吸收。其次是PL强度随T。升高而增强，与出注入a。的现象相反。因此，这种蓝光发射可能是与氧相关的另一种缺陷发光中心有关，即非桥键氧空穴中心NBOHC。 我们的样品在T。较低时，主要成分是a｛ ／ Sicx的混合。随T。上升，开始形成h颗粒，逐渐形成＊七 与Smx的结构形式，但两者之间仍有 a｛工过渡层。随 T。进一步升高，由 a｛工膜的 XRD图矛前人的实验推车如 T＞800℃硅晶化自分急后增力，相应的 a七 减少，nc｛ 和 a七。之间较陡的界面形成。这个陡的界面由于明显的晶格结构的差别而有较大的应力。界面的形成伴随着界面发光中心的增加，同时PL强度在L户800℃有一个大的增强。这个结果提示我们，界面上h －0－S工键断裂形成的 NBOHC应是蓝光发射的主要原因。更多还原

【Abstract】 As one kind of Si nanostructures, Si-rich Si02 films are theimportant Si-based light-emitting materials.Moreover, silicon is theleading semiconductor in the microelectronic industry .FurthermoreSi02 films as passitive and insular layers are widely used in Si deviceand integrated circuit.So Si-rich films are considered suitable foroptoelectronic applications.The first part of the dissertation mainly discuss the intenseresearch activity in the last decade devoted towards the study ofdifferent approaches able to solve the nanocrystalline silicon film as alight emitter.The great progress in the communication technology in the lastyears has resulted in an increased demand for optoelectronic functionsintegrated with electronic circuits.They woud allow one to couple theinformation processing capabilities of microelectronics with the theefficient interconnection properties of optoelectrtonics.In principle,Siwould be the best material because of its mature technology and itsdomain in microelectronics.Sinee the discovery of intense visible lightemission in porous Si by Canham at the beginning of the 1 990’s,a lotof work has been done in studying Si nanostructures whichcomprehend porous Si,Si nanocrystals（nc） produced with severaldifferent techniques（namely,high-dose Si implantation in Si02,plasma-- 52 -Abstrctenhanced chemical vapor deposition,sputter deposition）.But Sinanocrystals present the advantage of being much morestable .Experiment and theoretical studies have been performed on Sinc in order to understand the physical mechanisms underlying thislight emission.Several models have been proposed ascribing thevisible light emission to quantum confinement effects in Sinanocrystals or to defects （0 vacancy or nonbridging 0 centers）in theSi oxide matrix containing Si nc,but the discussion is still open.Inparticular,many authors have observed that there is a quantitativediscrepancy between the luminescence energy from Si no and thewidth of the energy band gap calculated for Si no on the basis of thequantum confinement theory Such observation has been explainedinvolving a defect center at the Si nc/Si02 inerface as an intermediatestate for electron-hole recombination.After the current study status of the nanocrystalline Si films aresummarized, the second chapter gives out the detailed process of ourexperiment. Si-rich Si02 films have been prepared by a rf magnetronsputter method and their photoluminescence,as well as infraredspectroscopy,has been measured for the as-deposited and annealedfilms. We designed a new type of sputter target whose distributionstructure made Si no embedded in 8102 more homogeniously.Experiment results are presented. IR spectrum analyses havedemonstrated that the structure mode of the substoichiometric silicon- 53 -Abstrctoxide films（SiO^） can be described as a mixture of RMM and RBMxat relatively low annealing temperature. The reaction, Si-Si^O4^--- ?4^x=l,2,3,takes place upon annealing. As a result4the rising annealing temperature induces Si02 phase to form,alsoivolves the formation of a Si phase.In high-temperature-annealedSiO^, films the excess silicon atoms are present as Si-Si4tetrahedra,randomly dispersed in the amorphous Si02matrix.Photoluminescent spectra were observed for the samplesexcided by the laser whose wavelength is 365nm.The PL peak islocated at about 445nm,which dosen’t shift as the annealingtemperature changes.As the annealing temperature is raised,theluminescent intensity increases.The phenomena suggest that the Si-O-Si bond as a defect center which is broken down by the stress at the Sinc/Si02 interface is the primary source of blue luminescence.Conclusions and improvements are represented at last.更多还原