重掺硼对直拉单晶硅片上压痕位错运动的影响

对比研究了轻掺硼(1.5×10~(16)cm~(-3))和重掺硼(1.2×10~(20)cm~(-3))直拉硅片上维氏压痕周围的残余应力分布及压痕位错在900℃滑移的情况。研究表明:重掺硼直拉硅片上压痕周围的残余应力及应力场区域显著小于轻掺硼硅片的。在900℃热处理时,轻掺硼硅片上的压痕位错发生显著的滑移,而重掺硼硅片上的压痕位错几乎不发生滑移。一方面,重掺硼降低了单晶硅的压痕断裂韧性,使侧向裂纹尺寸增大而释放更多的应力,从而使压痕的残余应力变小;另一方面,重掺硼对位错具有明显的钉扎作用,使位错的滑移需要更大的应力驱动。可以认为正是上述两方面的效应使得重掺硼硅片的压痕位错几乎不发生滑移。     

掺硼金刚石薄膜二次电子发射特性的研究

掺硼金刚石薄膜具有负电子亲和势和良好的电子运输性能且容易制备,作为冷阴极材料在图像显示技术和真空技术等方面都有着巨大的应用价值,引起人们的注意.从二次电子发射的机理以及影响二次电子发射系数的因素等方面,对如何利用MPCVD法制备出高二次电子发射系数的掺硼金刚石薄膜进行了综述.论述表明通过合适的工艺条件,对薄膜表面进行适当的处理,是可以制备出高二次电子发射系数的阴极用金刚石薄膜的.     

大尺寸掺硼宝石级金刚石单晶的高温高压合成及电学性质研究

在5.4GPa、1200～1400℃条件下,进行掺硼金刚石单晶的合成研究。成功合成出了重0.2g,径向尺寸达6.0mm的优质掺硼金刚石单晶。考察了合成体系中硼添加量对晶体透光度的影响。利用伏安特性和霍尔测试,得到了掺硼金刚石单晶常温电阻率、霍尔系数及霍尔迁移率和合成体系中硼添加量的关系。研究发现,随着合成体系中硼添加量的增加,晶体的电阻率和霍尔迁移率都呈下降趋势;霍尔系数随硼添加量的增加先下降后上升。随着硼添加量的增加:晶体常温电阻率下降,表明硼杂质已进入到金刚石晶体中。霍尔迁移率的下降,可能是晶体缺陷增多对载流子散射所致。霍尔系数先减小后增大,这可能与进入金刚石的硼元素量增大及晶体缺陷增多有关。     

掺硼浓度对金刚石薄膜二次电子发射特性的影响

掺硼金刚石薄膜具有负电子亲和势和良好的电子运输性能且容易制备,作为冷阴极材料在图像显示技术和真空技术等领域都存在巨大的应用价值,引起人们的广泛关注。采用MPCVD法利用氢气、甲烷和硼烷的混合气体,制备出不同浓度的掺硼金刚石薄膜。结果表明,掺硼浓度影响金刚石薄膜的物相结构、组织形貌,进而影响其二次电子发射性能,当硼烷的流量为4mL/min时,制备的金刚石薄膜质量最好,二次电子发射系数约为90。     

高掺杂Si/BDD薄膜电极的制备及电化学性能

近年来,掺硼金刚石(BDD)膜因具备独特的优异性能而作为电极材料已经受到很大的关注.本文通过MPCVD法在高掺杂硅衬底上生长掺硼金刚石膜,并用四探针、扫描电镜、激光拉曼和电化学工作站对其进行了检测,发现所制备的掺硼金刚石膜电导率达10-2Ω·cm,同时发现金刚石膜质量因硼原子的掺入而有所下降,采用循环伏安法研究其电化学...     

硼异质富勒烯制备过程中巴基管与巴基葱的异常生长行为

电弧法制备掺硼富勒烯过程中发现，与纯富勒烯相比，掺硼富勒烯烟灰的电导率提高一个数量级以上。电镜观察显示掺硼富勒烯烟灰中含有较多的巴基管和巴基葱，而阴极沉积物中则发现含有珠链状巴基葱。     

含硼黄铜冷凝管使用前后表面膜及耐蚀性的研究

一种加痕量硼的新型黄铜冷凝管在电厂运行4—5年中显示出较好的耐蚀性。本文用 X 射线、电子探针、离子探针及电化学等方法研究了该冷凝管在使用前后表面膜及腐蚀产物的组织和成分。结果表明:由于硼在退火过程中形成的表面膜中富集,从而提高了冷凝管的防护能力。     

掺硼金刚石/硬质合金膜基结合和摩擦磨损性能的研究

金刚石刀具涂层在碳纤维复合材料等难加工材料高效加工方面有着广阔的应用前景。在热丝化学气相沉积系统通过气体掺硼,在硬质合金表面制备了掺硼金刚石涂层。通过SEM、Raman以及压痕测试对涂层的表面形貌、成分和膜基结合性能进行了测试和分析;对涂层进行了摩擦磨损实验,研究了涂层不同环境温度下的摩擦系数及磨损率。结果表明,适量的硼掺杂可以细化金刚石晶粒,提高膜基结合力,降低摩擦系数并提高耐磨性,掺硼金刚石磨损率随温度的升高而增大,本文合适的掺硼浓度为3×10-3。     

微量硼对镁合金耐腐蚀性能的影响

镁合金中加入微量硼,可以细化晶粒,但硼对镁合金耐腐蚀性能的影响,国内外未见报道.通过测定自腐蚀电位、极化曲线、盐雾腐蚀速率和对盐雾腐蚀试样表面形貌扫描等技术,研究了微量硼对镁合金(Mg-7Al-0.4Zn-0.2Mn)耐腐蚀性能的影响.结果表明:微量硼的加入显著细化了镁合金的组织和晶粒,从而提高了其自腐蚀电位,降低了盐雾腐蚀速率,使耐腐蚀性能得以改善;当硼的加入量为0.15%时,镁合金的自腐蚀电位比未加时约提高25 mV,腐蚀速率比未加时降低31.7%.     

掺硼金刚石膜的热敏特性

用微波ＰＣＶＤ法将掺硼金刚石膜淀积在Ｓｉ３Ｎ４基片上，用Ｔｉ薄膜作为欧姆接触电极蒸发在金刚石表面上，为防止Ｔｉ在高温下氧化，上面镀上了Ａｕ薄膜，从室温到６００℃范围内测试了这些金刚石膜样的电阻（Ｒ），发现Ｔ＾－１和Ｒ之间呈线性关系，若改变掺硼浓度以及热处理条件可以控制掺硼金刚石膜的热敏特性，结果表明掺硼金刚石膜显示了高的敏感性和好的稳定性，是一咱优良的热敏电阻材料。     

Aktuelle Entwicklungen in der Zühtungstechnologie von CZ‐Si‐Kristallen

Current Developments in CZ Si Crystal Growing Technology The industrial growing of increasingly large and perfect silicon (Si) monocrystals for applications in microelectronics and photovoltaics requires continuous improvement of process control and growing technology. Continuous adaptation and optimization of system technology in terms of reliability, process flexibility and dimensioning are also necessary. The basic principles of industrial silicon crystal growing and the resultant requirements for the Si process andsystem technologies are described in the first part of this series of articles. The constantly increasing requirements for the performance and complexity of the electronic circuits (chips) in accordance with Moore's Law mean that the requirements for the perfection and dimensions of monocrystalline Si wafers and Si crystals are also continuously rising. After the introduction of the 300 mm Si wafer generation in recent years, the next Si wafer generation (450 mm) is therefore being discussed already. The technological and economic effects of these constantly increasing requirements for the necessary system technologies will be set out and discussed in the subsequent articles on the basis of current Si CZ crystal growing systems as well as new system concepts.     

Improved efficiency of p-type quasi-mono silicon blanket emitter solar cell by ion implantation and backside rounding

A novel type of silicon material, p-type quasi-mono wafer, has been produced using a seed directional solidification technique. This material is a promising alternative to traditional high-cost Czochralski (CZ) and float-zone (FZ) materials. This study evaluates the application of an advanced solar cell process that features a novel method of ion-implantation and backside rounding process on p-type quasi-mono silicon wafer. The ion implantation process substituted for thermal POCl₃ diffusion leads to better R _sheet uniformity (<3 %). After screen-printing, the interface of Al and back surface field (BSF) layers was analyzed for the as prepared samples and the samples etched to three different depth. SEM showed that increased etch depth improved both BSF layer and Al-Si layer. The IQE result also showed that the samples with higher etching depth had better performance at long wavelength. The I–V cell tester showed that the sample with the etching depth of 6 μm ± 0.1 μm had the greatest efficiency, due to the highest V _oc and I _sc . The solar cell fabricated in this innovative process on 156 × 156mm p-type quasi-mono silicon wafer achieved 18.82 % efficiency.     

Impurity engineering of Czochralski silicon

Microelectronic devices with high integration level and functional complexity are always requiring larger diameter and more perfect Czochralski (CZ) silicon wafers. Therefore, the defects, playing the key role in the quality control of silicon materials, have to be well controlled during crystal growth and device fabrication. Co-doping nitrogen (N), germanium (Ge) or carbon (C) into CZ silicon to control defect dynamics and to change defect evolution, so-called “impurity engineering”, has been developed in recent years, and has been widely applied in the fabrication of higher quality CZ silicon used for microelectronics nowadays. This article is to present an overview of the current status of impurity engineering in CZ silicon, based on the co-doping technologies of N, Ge and C. The fundamental properties of these three co-dopants and their interaction with point defects in CZ silicon are firstly introduced. The bulk of the article is focused on the effects of co-dopants on the formation of oxygen precipitates related to internal gettering (IG) of devices for metal contaminants, and voids associated with the gate oxide integrity (GOI) of devices in CZ silicon. Finally, the improvement of CZ silicon mechanical strength by co-doping technology is described.     

Characterization of nanoporous silicon layer to reduce the optical losses of crystalline silicon solar cells

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated using SEM. The formation of a nanoporous Si layer on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900 nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.     

Defect engineering of Czochralski single-crystal silicon

Modern microelectronic device manufacture requires single-crystal silicon substrates of unprecedented uniformity and purity. As the device feature lengths shrink into the realm of the nanoscale, it is becoming unlikely that the traditional technique of empirical process design and optimization in both crystal growth and wafer processing will suffice for meeting the dynamically evolving specifications. These circumstances are creating more demand for a detailed understanding of the physical mechanisms that dictate the evolution of crystalline silicon microstructure and associated electronic properties. This article describes modeling efforts based on the dynamics of native point defects in silicon during crystal growth, which are aimed at developing comprehensive and robust tools for predicting microdefect distribution as a function of operating conditions. These tools are not developed independently of experimental characterization but rather are designed to take advantage of the very detailed information database available for silicon generated by decades of industrial attention. The bulk of the article is focused on two specific microdefect structures observed in Czochralski crystalline silicon, the oxidation-induced stacking fault ring (OSF-ring) and octahedral voids; the latter is a current limitation on the quality of commercial CZ silicon crystals and the subject of intense research.     

Fracture toughness measurement of thin-film silicon

The fracture toughness of single‐crystal silicon thin films oriented to (100) and (110) was investigated by tensile testing under both 〈100〉 and 〈110〉 loading conditions. The specimen was fabricated from a p‐type Czochralski (CZ)‐grown wafer and passed through a thermal process during the fabrication of the test device. The measured fracture toughness is dependent on the loading direction in the tensile test and independent of the specimen surface orientation. The test results were 1.94 MPa√m in the 〈100〉 direction and 1.17 MPa√m in the 〈110〉. In these tests, no longitudinal size effect on the fracture stress or fracture toughness was observed. The SEM photographs obtained from the fracture specimens after the tensile test show that the crack initiated from the notch tip and propagated straight in the across‐the‐width direction on the (110) or (111) cleavage plane.     

一种新型腐蚀剂——醋酸钠溶液对单晶硅太阳电池表面织构化的作用

对晶向为(100)的p型单晶硅片进行表面刻蚀,制作减反射绒面。选用了一种新型的腐蚀剂,即醋酸钠(CH3COONa)溶液,用来腐蚀单晶硅太阳电池。通过分别改变醋酸钠溶液的浓度、温度以及腐蚀时间对硅片表面进行腐蚀发现,经醋酸钠溶液腐蚀后在硅片表面形成腐蚀坑大小适中、分布均匀的绒面结构。在醋酸钠溶液的质量分数为20%、温度为95℃、时间为40min的条件下腐蚀单晶硅片,在波长为700～1000nm之间获得较低的平均表面反射率,且最佳平均反射率为12.14%。从实验结果和成本因素考虑,这种腐蚀剂的成本很低,不易污染环境且重复性好,有利于大规模工业化制绒。     

太阳电池用掺氮直拉单晶硅中氧沉淀行为的研究

利用傅立叶红外光谱仪研究了掺氮直拉单晶硅(NCZ)和普通直拉单晶硅(CZ)的原生氧沉淀以及模拟太阳电池制备热处理工艺下的氧沉淀行为.结果发现,掺氮直拉单晶硅的原生氧沉淀浓度比普通直拉单晶硅的略高,这是因为氮在晶体生长过程中可以促进氧沉淀.但是在模拟太阳电池制备热处理工艺中掺氮直拉单晶硅和普通直拉单晶硅一样,没有氧沉淀产生.这表明在太阳电池的短时间热处理工艺中,氮不会对氧沉淀产生影响,不会影响磷吸杂的效果.     

Züchtung von Silizium-Einkristallen mit 300 mm Durchmesser

Perfect and homogeneous mono crystalline silicon wafers, made from Si-crystals, grown by the Czochralski (CZ) or Floatzone (FZ) process, are basis material and substrate for nearly most of all semiconductor devices of modern microeletronic. The growth of Si-crystals with a high degree of perfection and homogeneity requires a highly developed process and equipment technology. In addition, also the requirements for Si-crystals and wafer dimensions are more and more increasing by economic reasons. At the moment, the mainly used standard Si-wafer diameters are 6″ (150 mm) and 8″ (200 mm). The introduction of 300 mm Si-Wafer just takes place now, requiring substantial efforts for process and equipment development, evaluation as well as very high investment costs. The new 300 mm Si-crystal puller generation EKZ 3000 of Leybold systems is an example for the development and evaluation of 300 mm Si-equipment and will be described here more in detail. First experiences and results will be reported.     

Synthesis and characterization of well-defined polymer brushes grafted from silicon surface via surface reversible addition-fragmentation chain transfer (RAFT) polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to prepare polymer brushes grafted onto silicon wafer surface. Novel RAFT agent was prepared and immobilized on the silicon wafer surface. RAFT polymerizations were then conducted from the silicon surface to graft polymer brush to the silicon. Analysis of the polymer brush layers was conducted using ellipsometry, XPS, AFM and contact angle measurements, respectively.