p型硅片表面氧化雾缺陷的吸除

利用快中子辐照在ｐ型硅片中产生辐照缺陷，利用其作为热处理时硅中氧沉淀的成核中心，在硅片表面层形成洁净区和在体内形成吸杂区，能有效地抑制硅片表面氧化雾缺陷的形成。提出了较为实用的退火工艺和简单的解释。     

区熔硅近表面洁净区和体内微缺陷的形成

中子辐照区熔 (氢 )硅片经退火后在近表面形成洁净区 ,在硅片内部形成体内微缺陷 .微缺陷的形成与中子辐照造成的损伤及单晶硅内氢杂质的催化加速有关 ,还与后续退火条件有关 .第一步退火的温度对微缺陷的尺度有很大的影响 ,中低温要比高温所形成的微缺陷小 .在退火过程中微缺陷有一个生长过程 ,110 0℃退火 2 h微缺陷已达最大 .硅片表面的粗糙度影响表面洁净区的形成 ,洁净区出现在未抛光面 ,双面抛光硅片不会形成表面洁净区.     

区熔硅近表面洁净区和体内微缺陷的形成

中子辐照区熔(氢)硅片经退火后在近表面形成洁净区,在硅片内部形成体内微缺陷.微缺陷的形成与中子辐照造成的损伤及单晶硅内氢杂质的催化加速有关,还与后续退火条件有关.第一步退火的温度对微缺陷的尺度有很大的影响,中低温要比高温所形成的微缺陷小.在退火过程中微缺陷有一个生长过程,1100℃退火2h微缺陷已达最大.硅片表面的粗糙度影响表面洁净区的形成,洁净区出现在未抛光面,双面抛光硅片不会形成表面洁净区.     

区熔硅近表面洁净区和体内微缺陷的形成

中子辐照区熔(氢)硅片经退火后在近表面形成洁净区,在硅片内部形成体内微缺陷.微缺陷的形成与中子辐照造成的损伤及单晶硅内氢杂质的催化加速有关,还与后续退火条件有关.第一步退火的温度对微缺陷的尺度有很大的影响,中低温要比高温所形成的微缺陷小.在退火过程中微缺陷有一个生长过程,1100℃退火2h微缺陷已达最大.硅片表面的粗糙度影响表面洁净区的形成,洁净区出现在未抛光面,双面抛光硅片不会形成表面洁净区.     

中子辐照对硅片表面氧化层错的抑制作用

对硅片表面氧化层错形成机理进行了探讨。并通过中子辐照在直拉硅中引入缺陷，利用辐照缺陷和硅中氧的相互作用，强烈抑制硅片表面氧化层错的产生。     

快速预热处理对大直径CZ-Si中FPDs及清洁区的影响

研究了不同气氛下快速预热处理(RTA)后,硅片中的流动图形缺陷(FPDs)密度和随后两步热处理形成的魔幻清洁区(MDZ)之间的关系.硅片经过高温快速预热处理后,再经过800℃(4h) 1000℃(16h)常规退火,以形成MDZ.研究发现,当硅片在Ar气氛或N2/O2(9%)混合气氛下RTA预处理后,FPDs密度较低,随后热处理出现的氧沉淀诱生缺陷密度较高、清洁区较宽.对于N2/O2混和气氛,随着O2含量的增加,FPDs和氧沉淀诱生缺陷密度变小,纯O2气氛下预处理后硅片中FPDs和氧沉淀诱生缺陷密度最低.因此,可以通过调节N2/O2混合气氛中两种气氛的比例来控制空洞型微缺陷和硅片体内氧沉淀诱生缺陷的密度.     

快速预热处理对大直径CZ-Si中FPDs及清洁区的影响

研究了不同气氛下快速预热处理(RTA)后,硅片中的流动图形缺陷(FPDs)密度和随后两步热处理形成的魔幻清洁区(MDZ)之间的关系.硅片经过高温快速预热处理后,再经过800℃(4h)+1000℃(16h)常规退火,以形成MDZ.研究发现,当硅片在Ar气氛或N2/O2(9%)混合气氛下RTA预处理后,FPDs密度较低,随后热处理出现的氧沉淀诱生缺陷密度较高、清洁区较宽.对于N2/O2混和气氛,随着O2含量的增加,FPDs和氧沉淀诱生缺陷密度变小,纯O2气氛下预处理后硅片中FPDs和氧沉淀诱生缺陷密度最低.因此,可以通过调节N2/O2混合气氛中两种气氛的比例来控制空洞型微缺陷和硅片体内氧沉淀诱生缺陷的密度.     

单晶硅中过渡族金属镍对洁净区形成的影响

研究了过渡族金属镍在快速热处理作用下对直拉单晶硅中洁净区形成的影响.实验结果发现:硅中魔幻洁净区(MDZ)形成后,氧沉淀及其诱生缺陷能有效地吸杂金属镍;而沾污金属镍的硅中,随后的快速热处理工艺不能形成MDZ,硅片近表面出现大量沉淀.采用传统的内吸杂工艺,镍沾污的次序对洁净区的形成没有影响.实验表明由于硅片表面形成的镍硅化合物的晶格常数比硅小,所以在硅片近表面产生高浓度的空位,导致近表面的氧依然能够在MDZ工艺中形成沉淀.     

Effect of Nickel Contamination on Formation of Denuded Zone in Czochralski Silicon

研究了过渡族金属镍在快速热处理作用下对直拉单晶硅中洁净区形成的影响.实验结果发现:硅中魔幻洁净区(MDZ)形成后,氧沉淀及其诱生缺陷能有效地吸杂金属镍;而沾污金属镍的硅中,随后的快速热处理工艺不能形成MDZ,硅片近表面出现大量沉淀.采用传统的内吸杂工艺,镍沾污的次序对洁净区的形成没有影响.实验表明由于硅片表面形成的镍硅化合物的晶格常数比硅小,所以在硅片近表面产生高浓度的空位,导致近表面的氧依然能够在MDZ工艺中形成沉淀.     

NTDCZSi中辐照缺陷的电镜观察

利用硅中固有杂质与缺陷的相互作用来改善硅片质量以适应硅器件日趋严格的技术要求,逐步形成了目前的“缺陷工程”的内容,而将直拉硅(czsi)进行中子嬗变掺杂(NTD)不仅解决了掺杂的均匀性问题,且因大剂量中子辐照在czsi中引入大量的辐照缺陷并与czsi中氧等杂质的相互作用为缺陷工程增添了新的内容,最近的研究表明,中子辐照能强烈地抑制硅片表面缺陷,促进了硅中氧沉淀,并使czsi中氧沉淀定量控制,定域分布,定型转化。从而可改善器件质量,使器件成品率大大提高,因此对NTDCZSi中辐照缺陷的性质,结构及与硅中杂质的相互作用的研究,无疑对解释NTDCZSi中其它实验事实,对改善VLSI器件的材料性能都会具有十分重要的意义。     

Increased oxygen precipitation in CZ silicon wafers covered by polysilicon

Increased oxygen precipitation in CZ silicon wafers covered by a polysilicon layer has been observed after a high temperature anneal. This study established that the low temperature anneal, inherent in the LPCVD polysilicon deposition process, is so responsible for the enhanced oxygen precipitation effect. Temperature-time parameters were developed to match oxygen concentration in the wafer material with preannealing (polysilicon deposition) temperatures to achieve various degrees of oxygen precipitation. Data from this work show that interstitial oxygen reduction (δ C_ox) saturation can be achieved after 100 min oxidation at 1150°C, if the polysilicon deposition temperature is between 670–700°C (150 min for a 1.3 Μm polysilicon layer) and the interstitial oxygen concentration in the wafer is between 22 and 24 ppm. A denuded zone of 20 Μm was obtained and can be observed on a chemically etched cross section. Chemically etched and decorated defects in these samples with various degrees of oxygen precipitation are also displayed in these optical micrographs.     

Adhesion of NCF to oxidized Si wafers after oxygen plasma treatment

The effect of oxygen plasma treatment on the adhesion between nonconductive film (NCF) and oxidized Si was investigated. Oxidized Si wafers were treated with oxygen plasma for 5 min and then rinsed in de-ionized water (DIW). The water contact angle was measured by means of the sessile drop technique and the surface roughness was measured by means of atomic force microscopy. The adhesion of the NCF to the oxidized Si wafer was evaluated by means of a single-lap shear test after bonding at 150°C for 5 s. Oxygen plasma treatment decreased the water contact angle. The roughness of the oxidized Si wafer decreased when oxygen plasma treatment was applied alone, but was increased when both oxygen plasma treatment and DIW rinse were applied. Similarly, the shear strength decreased when oxygen plasma treatment was applied alone, but the adhesion of NCF increased when both oxygen plasma treatment and DIW rinse were applied. The increased surface roughness of the oxidized Si wafer played an important role in increasing the adhesion between the NCF and the oxidized Si wafer. The shear strength further increased after post-heat treatment at 170°C for 1 hr or at 280°C for 15 s. Low shear strength observed before post-heat treatment was ascribed to incomplete NCF curing. Differences observed in the adhesion strength between two types of NCF were attributed to differences in their curing degrees and their degrees of surface coverage of the oxidized Si substrates.     

线切割机加工半导体晶片质量控制的研究

根据线切割机的工作原理,切片过程中硅片因机械作用造成的刀痕、损伤、破损产生包括机械应力和热应力在内的应力,进而产生滑移位错.当机械应力和热应力在高温处理过程中的作用超过晶体滑移临界应力时,会产生硅片的破碎.对于翘曲度、弯曲度、总厚度误差、中心厚度误差等方面的质量控制,通过调整线张力、进给速度、冷却剂流量等一系列工艺措施可达到目的及要求,大大降低了生产成本,提高了生产效率.实验证明,线切割机切出的硅片的厚度和质量都很好地满足了下一道工序的要求.     

DNA-Based Strategies for Site-Specific Doping

The development of novel doping strategies compatible with high-resolution patterning and low cost, large-scale manufacturing is critical to the future development of electronic devices. Here, an approach to achieve nanoscale site-specific doping of Si wafer using DNA as both the template and the dopant carrier is reported. Upon thermal treatment, the phosphorous atoms in the DNA diffuse into Si wafer, resulting in doping within the region right around the DNA template. A doping length of 30 nm is achieved for 10 s of thermal treatment at 1000 °C. Prototype field effect transistors are fabricated using the DNA-doped Si substrate; the device characteristics confirmed that the Si is n-doped. It is also shown that this approach can be extended to achieve both n-type and p-type site-specific doping of Si by using DNA nanostructures to pattern self-assembled monolayers. This work shows that the DNA template is a dual-use template that can both pattern Si and deliver dopants.     

SIMOX材料顶层硅膜中残余氧的行为

利用光致发光谱 (PL)和二次离子质谱 (SIMS)检测了不同退火条件下处理的 SIMOX材料的顶层硅膜 .实验结果显示 ,SIMOX顶层硅膜的 PL 谱有三个峰 :它们是能量为 1.10 e V的 a峰、能量为 0 .77e V的 b峰和能量为0 .75 e V的 c峰 .与 RBS谱相比 ,发现 a峰峰高及 b/ a峰值比是衡量顶层硅膜单晶完整性的标度 .谱峰 b起源于SIMOX材料顶层硅膜中残余氧 ,起施主作用 .SIMS测试结果显示 ,谱峰 c来源于 SIMOX材料顶层硅膜中的碳和氮 .     

Room-temperature microfluidics packaging using sequential plasma activation process

A sequential plasma activation process consisting of oxygen reactive ion etching (RIE) plasma and nitrogen radical plasma was applied for microfluidics packaging at room temperature. Si/glass and glass/glass wafers were activated by the oxygen RIE plasma followed by nitrogen microwave radicals. Then, the activated wafers were brought into contact in atmospheric pressure air with hand-applied pressure where they remained for 24 h. The wafers were bonded throughout the entire area and the bonding strength of the interface was as strong as the parents bulk wafers without any post-annealing process or wet chemical cleaning steps. Bonding strength considerably increased with the nitrogen radical treatment after oxygen RIE activation prior to bonding. Chemical reliability tests showed that the bonded interfaces of Si/Si could significantly withstand exposure to various microfluidics chemicals. Si/glass and glass/glass cavities formed by the sequential plasma activation process indicated hermetic sealing behavior. SiO/sub x/N/sub y/ was observed in the sequentially plasma-treated glass wafer, and it is attributed to binding of nitrogen with Si and oxygen and the implantation of N/sub 2/ radical in the wafer. High bonding strength observed is attributed to a diffusion of absorbing water onto the wafer surfaces and a reaction between silicon oxynitride layers on the mating wafers. T-shape microfluidic channels were fabricated on glass wafers by bulk micromachining and the sequential plasma-activated bonding process at room temperature.     

Investigation of Al back contacts and BSF formation by in situ TEM for silicon solar cells

Back contacts for Si solar cells made by Al evaporation and screen printing Al paste were studied by transmission electron microscopy. Si was found to diffuse into the Al during heating. Si diffusion formed vacancies in the Si wafer and Al could then penetrate the Si wafer in spiked formations. The Al spikes retracted during cooling, leaving a doped back surface field region. Copyright © 2012 John Wiley & Sons, Ltd.     

掺锗直拉硅片三步退火本征吸除清洁区形成的研究

运用高温-低温-高温三步退火的本征吸除工艺研究了锗的存在对硅片清洁区形成的影响。发现直拉硅中杂质锗的存在可促进氧的外扩散,抑制氧沉淀的发生并可形成较宽的清洁区。     

Diffusion and trapping of implanted hydrogen in a Si/Si:B/Si structure

H implantation in Si/Si:B/Si structures is a promising route to improve the Smart Cut™ process and transfer thin Si layers of reduced roughness and controlled thickness onto regular Si wafers. However, the mechanisms driving this process are unknown and thus difficult to model or optimize. For this reason, we have experimentally studied the redistribution of H which takes place in such structures after implantation and during annealing using SIMS and TEM. We show that the Si:B layer already traps H during implantation and form platelets parallel to the wafer surface. During annealing, the H atoms implanted in the Si regions are slowly transferred toward the Si:B layer where they are trapped on large platelets which grow further during annealing. Routes to optimize this process go through the minimization of H precipitation in the pure Si regions. This can probably be achieved by optimizing the implantation conditions.     

Study of thinned Si wafer warpage in 3D stacked wafers

3D (three-dimensional) wafer stacking technology has been developed extensively recently. One of the many technical challenges in 3D stacked wafers, and one of the most important, is wafer warpage. Wafer warpage is one of the root causes leading to process and product failures such as delamination, cracking, mechanical stresses, within wafer (WIW) uniformity and even electrical failure. In this study, the wafer warpage of thinned Si wafers in stacked wafers has been evaluated. Si wafer or glass was used as a thick substrate, and Cu or polyimide was used as the bonding material. The top Si wafer in the bonded stack was ground down to 20–100 μm, and wafer curvature was measured. Wafer curvature and how it relates to bonding material, substrate material of the stacked layers, and thickness of thinned Si wafer will be discussed.