可用于Ⅲ族氮化物生长的50mm 3C-SiC/Si(111)衬底的制备

利用新研制出的垂直式低压CVD(L PCVD) Si C生长系统,获得了高质量的5 0 mm 3C- Si C/ Si(111)衬底材料.系统研究了3C- Si C的n型和p型原位掺杂技术,获得了生长速率和表面形貌对反应气体中Si H4 流量和C/ Si原子比率的依赖关系.利用Hall测试技术、非接触式方块电阻测试方法和SIMS,分别研究了3C- Si C的电学特性、均匀性和故意调制掺杂的N浓度纵向分布.利用MBE方法,在原生长的5 0 mm 3C- Si C/ Si(111)衬底上进行了Ga N的外延生长,并研究了Ga N材料的表面、结构和光学特性.结果表明3C- Si C是一种适合于高质量无裂纹Ga N外延生长的衬底或缓冲材料.     

蓝宝石衬底上6H-SiC单晶薄膜的化学气相淀积生长

采用低压化学气相淀积方法以相对较低的生长温度(900～1050℃)在蓝宝石(0001)衬底上外延生长了6H-SiC单晶薄膜。其晶体质量和结构由X射线衍射谱和喇曼散射谱的测量结果得到确定。俄歇电子能谱和X射线光电子能谱的观察表明所制备的6H-SiC薄膜中的Si-C键的结合能为181．4eV,Si与C的原子比符合SiC的化学配比。扫描电子显微镜的分析显示6H-SiC外延层和蓝宝石衬底间的界面相当平整。由紫外及可见光波段吸收谱的结果得到所生长的6H-SiC的禁带宽度为2．83eV、折射系数在2．5～2．7之间。均与6H-SiC体材料的相应数据一致。     

SiNx 和SiC 材料的红外吸收特性研究

采用LPCVD和PECVD技术制作了不同厚度的SiNx和SiC材料样品,使用傅立叶变换红外光谱仪对其进行了红外吸收特性测试,并通过离子注入的方式对其红外吸收特性进行调节.实验结果表明:LPCVD SINx材料在8～14μm波段存在吸收峰,而PECVD SiNx和SiC材料在3μm～5μm波段和8～14μm波段存在吸收峰.随着材料厚度的增加,吸收度也增加,1 μm厚的LPCVD SiNx,红外吸收度可以达到0.92.离子注入可改变材料的红外吸收能力.     

Application of selective CVD tungsten for low contact resistance via filling to aluminum multilayer interconnection

Process parameters for selective chemical vapor deposition of tungsten to fill vias between aluminum or aluminum alloy multilevel metallization have been identified and demonstrated. By controlling two competing parallel reactions: Aluminum and hydrogen reductions of tungsten hexafluoride in one reduction step process, the specific contact resistivity was found to be in the range of 2.5 to 8.0 x 10⁻⁹ ohm-cm² for 1.8 micron diameter vias. This is at least one order of magnitude lower than the values reported by the previous workers. It was also observed that alloying the aluminum did not appear to affect the contact resistance significantly. In this experiment one cold wall experimental reactor, two cold wall production systems of two different models and one hot wall tube furnace were used to deposit selective CVD tungsten on aluminum or aluminum with 1% silicon first level metal. As a consequence of these findings, problems associated with filling straight wall vias of high aspect ratio in VLSI multilevel interconnection (i.e., high contact resistance, poor step coverage, electromigration, etc.) can now be alleviated or resolved. Therefore, the use of selective CVD tungsten in the existing aluminum IC metallization becomes very attractive and feasible.     

Optical properties of silicon thin films related to LPCVD growth condition

In this paper we study the changes in the microstructural and optical properties of silicon thin films produced by the variation of the parameters (temperature and pressure) of the low-pressure chemical vapour deposition (LPCVD) process. Silicon thin films prepared by LPCVD on oxidized silicon substrates over a large range of process parameters (T_dep=500-615°C, p_dep=20-100 Pa) have been characterized by Raman spectroscopy, spectroscopic ellipsometry (SE), X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. The phase transition of as-deposited silicon from an amorphous to a crystalline phase via an intermediate mixed phase (few grains in amorphous silicon matrix) can be monitored by the changes in the optical properties and in the Raman spectra. LPCVD parameters, which control the deposition kinetics, are able to influence the optical properties, the structure and/or morphology of the as-deposited LPCVD silicon films. The SE and Raman results prove that it is possible to grow by LPCVD (from pure silane), a silicon film in a (poly)crystalline state at a temperature as low as 500°C.     

SHORT COMMUNICATION: Surface passivation by rehydrogenation of silicon‐nitride‐coated silicon wafers

A silicon wafer with a silicon nitride layer deposited by low pressure chemical vapour deposition may be subjected to high‐temperature treatments without adversely affecting the electronic properties of the silicon on the condition that a thin oxide is present under the nitride. After high‐temperature treatments there is an apparent degradation in effective lifetime, probably due to a loss of hydrogen from the silicon/oxide interface. Effective lifetimes can be completely recovered by thermal treatment in a hydrogen‐containing ambient. This work has useful applications for solar cells as many of the properties of these nitrides can be used to advantage. Copyright © 2004 John Wiley & Sons, Ltd.     

Preparation and properties of Ta2O5 film capacitors using TiSi2 bottom electrode

Thin Ta₂O₅ films were grown in a low pressure chemical vapor deposition(LPCVD) reactor. The Al/Ta₂O₅/p-Si and Al/Ta₂O₅/TiSi₂/p-Si capacitors were fabricated and their capacitor characteristics were investigated. During a dry O₂ annealing process of the Ta₂O₅, the oxidation of Si substrate and TiSi₂ layer underneath the Ta₂O₅ layer was observed resulting in formation of SiO₂ and TiO₂ on their surfaces, respectively, due to the oxygen diffusion through the Ta₂O₅ layer. As-deposited 100 nm thick Ta₂O₅ film was found to be crystallized to δ-Ta₂O₅ at a temperature of about 700°C. The crystallized Ta₂O₅ film showed a higher leakage current density for the Al/Ta₂O₅/p-Si capacitor, compared to an amorphous Ta₂O₅ film. For the Al/Ta₂O₅/TiSi₂/p-Si capacitor, on the other hand, the leakage current characteristic was improved as the annealing temperature increased. Capacitance of the capacitor was found to also increase as the annealing temperature increased. The Al/Ta₂O₅/TiSi₂/p-Si capacitor, however, has failed to show the better capacitor characteristics over the conventional Al/Ta₂O₅/p-Si capacitor.     

Spatial batch optimal design based on self-learning Gaussian process models for LPCVD processes

Low pressure chemical vapor deposition (LPCVD) is one of themost important processes during semiconductor manufacturing. However, the spatial distribution of internal temperature and extremely few samples makes it hard to build a good-quality model of this batch process. Besides, due to the properties of this process, the reliability of the model must be taken into consideration when optimizing the MVs. In this work, an optimal design strategy based on the self-learning Gaussian processmodel (GPM)is proposed to control this kind of spatial batch process. The GPMis utilized as the internalmodel to predict the thicknesses of thin films on all spatial-distributed wafers using the limited data. Unlike the conventional model based design, the uncertainties of predictions provided by GPM are taken into consideration to guide the optimal design of manipulated variables so that the designing can be more prudent. Besides, the GPM is also actively enhanced using as little data as possible based on the predictive uncertainties. The effectiveness of the proposed strategy is successfully demonstrated in an LPCVD process.     

低压CVD氮化硅薄膜的沉积速率和表面形貌

以三氯硅烷(TCS)和氨气分别作为低压化学气相沉积(LPCVD)氮化硅薄膜(SiN_x)的硅源和氮源,以高纯氮气为载气,在热壁型管式反应炉中,借助椭圆偏振仪和原子力显微镜,系统考察了工作总压力、反应温度、气体原料组成等工艺因素对SiN_x薄膜沉积速率和表面形貌的影响.结果表明:随着工作压力的增大,SiN_x薄膜的沉积速率逐渐增加,并产生一个峰值.随着原料气中NH³/TCS流量比值的增大,SiN_x薄膜的沉积速率逐渐增加,随后逐步稳定.随着反应温度的升高,沉积速率逐渐增加,在830℃附近达到最大,随着反应温度的进一步升高,由于反应物的热分解反应迅速加剧,使得SiN_x薄膜的沉积速率急剧降低.在730-830℃的温度范围内,沉积SiN_x薄膜的反应表观活化能约为171kJ/mol.在适当的工艺条件下,制备的SiNx薄膜均匀、平整.较低的薄膜沉积速率有助于提高薄膜的均匀性,降低薄膜的表面粗糙度.     

LPCVD制备SIPOS薄膜淀积工艺的研究

SIPOS薄膜的含氧量是一个非常重要的工艺参数 .文中研究了用LPCVD法制备SIPOS薄膜的各种特性参数与含氧量的变化关系 ,提出了SIPOS薄膜生长的最佳工艺条件 .为SIPOS薄膜钝化技术的实用化奠定了基础 .