【作者】 王俊忠；

【导师】 吉元；

【作者基本信息】 北京工业大学 ， 材料学， 2007， 硕士

【摘要】 随着微电子器件和光电子器件向着高速化和高集成度方向的迅速发展,半导体外延结构及金属互连线的微观结构特征,以及多层膜之间在制备和使用过程中引入的应力,对电子器件的可靠性、使用寿命和出光率等起着关键的作用。本论文采用高分辨热场发射扫描电镜（TFE-SEM）与电子背散射衍射仪（EBSD）的一体化分析系统,测试了微电子器件金属化系统和半导体外延系统中的微结构、微织构及微区应力/应变特征,研究了微结构与半导体材料和器件制备工艺的相关性,以及对器件失效及可靠性的影响。本项工作对EBSD菊池衍射花样的收集参数和标定参数进行了分析和优化,对TSL EBSD系统的空间分辨率进行了测评,得出空间分辨率约为30nm⁴0nm。在此基础上,测试了超大规模集成电路（VLSI）中的Al互连线和甚大规模集成电路（ULSI）的Cu互连线,以及GaN/蓝宝石系统和GaAs/AlGaAs系统中微结构及微区应力分布特征。研究了采用传统的反应离子刻蚀工艺制备的Al互连线和采用大马士革凹槽工艺制备的Cu互连线的晶粒结构、取向、大小、形态及分布。结果表明:沉积态2μm宽的Al互连线和Cu互连线的平均晶粒尺寸分别为120nm和60～70nm。Al互连线在300℃、2.5hr退火后,晶粒尺寸增大至180nm,且趋于均匀;Cu互连线随着线宽由0.5μm增加到4μm,晶粒尺寸由30～40nm增大到80～90nm。350℃退火后,Al晶粒长大并呈近竹节结构,从而减小了金属离子沿晶界的扩散,提高了互连线的电徙动失效中值寿命（MTF）和激活能（Qa）。2μm宽沉积态的Al互连线具有很强的（111）丝织构,退火后（111）织构得到进一步的发展。在Cu互连线中,沿大马士革结构的凹槽侧壁垂直生长的晶粒和孪晶使得（111）织构弱化。在Al互连线中,Σ1晶界高达16.4%,并随着退火温度的升高增加至18.7%;Cu互连线的Σ3晶界（孪晶界）高达79.5%。孪晶界和小角度晶界这些低能构型的稳定晶界,均有利于提高互连线抗电徙动的能力。此外,采用EBSD菊池花样的质量参数IQ_{Image Quality},作为应力敏感参数。Al互连线退火后,平均IQ值和（111）、（100）和（110）取向晶粒的IQ_（111）、IQ_（110）和IQ_（100）均有所提高,表明退火使Al互连线的残余应力得到释放。IQ_（111）大于IQ_（100）和IQ_（110）,反映出不同晶体学取向的弹性模量存在的差异。在GaN/蓝宝石和GaAs/AlGaAs外延系统中,采用EBSD的IQ值、Hough变换的峰值及小角度错配等参数,作为应力/应变敏感参数,表征单晶外延生长薄膜中的晶格畸变程度和微区应力分布特征。研究结果表明:在GaN结构中应力缓冲层（Buffer层）附近的菊池线明锐程度降低,IQ值和Hough峰值最低,随着与Buffer层距离的增加,菊池线的锐化程度,IQ值和Hough峰值逐渐提高,以IQ和Hough峰的统计值显示出晶格畸变范围,表明以Buffer层为中心存在一个200nm～700nm的应变场。由计算可知Buffer层附近的位错密度达8×10¹¹/m²。EBSD测量GaN外延层与蓝宝石衬底存在着30°错配,计算的二者错配度为16%。结构通过20～30nm的Buffer层使应力应变释放,提高了外延生长的晶体质量,从而可保证发光二极管有源区的出光效率。在GaAs/AlGaAs多层周期生长的外延系统中,错配度0.14%,GaAs层的IQ值沿外延生长方向逐渐下降29%,表明外延结构中缺陷逐渐累加。AlGaAs层中由于衍射强度低而未能测量出IQ值,说明IQ值能反映出由于散射因子差异而造成的衍射强度的差异。采用快速傅立叶变换（FFT）和反变换（IFFT）,对应变和非应变区域的Kikuchi花样进行处理和计算,可实现衍射强度的比较。通过对Kikuchi花样进行相关函数分析,可得到GaN/蓝宝石结构中应变区域相对于无应变区域的晶带轴的微小位移量。更多还原

【Abstract】 Since there is fast development of microelectronic devices and photoelectronic devices to high-speed and high-density, the microstructure character of epitaxial structure in semiconductor and metallic interconnects, and the stress introduced during the preparing and using among multi-layer films, which plays an important role on the reliability, serving life and external quantum efficiency of electronic devices.In this thesis, the integrated analytical system of electron backscatter diffraction （EBSD） equipped in a high resolution TFE-SEM to measure the microstructure, micro-texture and micro-zone stress/strain character of metallic system in microelectronic devices and epitaxial system in semiconductor. The correlations between the microstructure and the preparing technology of semiconductor materials and devices, the influence of failure and reliability of devices were investigated.The analysis and optimization on the collecting parameter and indexing parameter of Kikuchi pattern were also carried out in this research. The spatial resolution of TSL EBSD system was measured and evaluated to be about 30nm⁴0nm. The Al interconnects in VLSI and Cu interconnects in ULSI were investigated with EBSD. The micro-texture and distribution of micro-zone stress in GaN/sapphire system and GaAs/AlGaAs system were studied.The distribution of grains structure, orientation, size and shape in Al interconnects prepared by conventional reactive ion etching technology （RIE） and Cu interconnects prepared by Damascus technology were investigated. Results indicate: the average grain size of 2μm width deposited Al interconnects and Cu interconnects are 120nm and 60⁷0nm, respectively. The grains in Al interconnects increased to 180nm after 2.5hr annealing treatment at 300℃and drived to uniformity.The grains in Cu interconnects increased from 30⁴0nm to 80⁹0nm, while the width increased from 0.5μm to 4μm. After annealing at 350℃, the grains grows up with a bamboo-like structure, which decreases the diffusion of metal ion along the grain boundaries and increases the MTF and Qa of interconnects. There are very strong （111） fiber texture in the 2μm width deposited Al interconnects and gets further developing after annealing. The （111） preferred orientation was weakened by the grains along the side wall of flute in Damascus structure and twin crystals.Σ1 grain boundaries reach 16.4% in Al interconnects and increases to 18.7% with the increasing of annealing temperature.Σ3 grain boundaries reach 79.5% in Cu interconnects. Twin crystal boundaries and low angle grain boundaries, which are low-energy stable boundaries, and they are propitious to enhance the ability to the resist elctromigration of interconnects. In addition, the IQ （Image Quality） of Kikuchi pattern was adopted as the strain sensitive parameters. The average IQ value and the IQ_（111）、IQ（110） and IQ_（100） of （111）, （100） and （110） orientation grains grown after annealing, which indicates that annealing can release the residual stress in Al interconnects. IQ_（111） is bigger than IQ_（100） and IQ（110） indicating the difference of elastic ratio among the different crystal orientations. In the epitaxial system of GaN/sapphire and GaAs/AlGaAs, the parameters of IQ value, Hough peak value and low angle misorientation etc. as strain sensitive parameters, were used to characterize the distortion of lattice and the distribution of micro-zone stress. Results indicate that: the sharpness of Kikuchi bands was reduced near the Buffer layer in the GaN structure and the lowest IQ value and Hough peak value were obtained. The sharpness of Kikuchi bands, IQ value and Hough peak value increased gradually with increasing distance from the Buffer layer. The statistic of IQ value and Hough peak value of the distorted region indicate that there is a 200nm⁷00nm elastically distorted region around the Buffer layer. The dislocation density near Buffer layer was calculated to be 8×10¹¹/m². The misorientation and the lattice mismatch between GaN epilayer and sapphire substrate were determined to be 30°and 16%, respectively. With thestress released by 20～30nm Buffer layer, the quality of crystal grown by epitaxial way was enhance and the the external quantum efficiency of light emitting diode in the active region was ensured.In the epitaxial system of Multi-layer increment of GaAs/AlGaAs, the lattice mismatch was measured to be 0.14% and the IQ value in GaAs layer along the epitaxially grown direction decreased gradually 29%. The results indicate that the defects were accumulated in the epitaxial structure. Due to the low diffraction intensity the IQ value can’t be obtained, which indicate that IQ value can reflect the difference of diffraction intensity caused by the difference of dispersion factor.The Fast Fourier Transform （FFT） and Inverse Fast Fourier Transform （IFFT） were adopted to calculate the Kikuchi patterns including both distorted region and non-distorted region to obtain the comparison of diffraction intensity. The small crystal lattice shift from the distorted region to non-distorted region can be calculated using the cross-correlation function of Kikuchi pattern, the small shifts in the zone axis position about the distorted region relative to the non-distorted region can be obtained in the GaN/sapphire structure.更多还原