快速退火气氛对300mm硅片内洁净区和氧沉淀形成的影响

300mm硅片中厚度合适的洁净区和高密度氧沉淀,有利于对器件有源区金属沾污的吸除,改善栅氧化物的完整性.文中使用Ar,N2/NHa混合气作为快速退火(RTA)气氛,研究RTA气氛对洁净区、氧沉淀形成的影响.研究发现N2/NHs混合气氛处理的硅片表层洁净区明显薄于Ar气氛处理的硅片,氧沉淀密度明显高于Ar气氛处理后的硅片.同时发现在两种气氛下,延长恒温时间都可以降低洁净区厚度,增加氧沉淀密度.基于空位增强氧沉淀成核和氮化空位注入的基本原理,就RTA气氛和恒温时间对洁净区和氧沉淀分布的影响进行了讨论.     

快速退火气氛对300mm硅片内洁净区和氧沉淀形成的影响

300mm硅片中厚度合适的洁净区和高密度氧沉淀,有利于对器件有源区金属沾污的吸除,改善栅氧化物的完整性.文中使用Ar,N2/NHa混合气作为快速退火(RTA)气氛,研究RTA气氛对洁净区、氧沉淀形成的影响.研究发现N2/NHs混合气氛处理的硅片表层洁净区明显薄于Ar气氛处理的硅片,氧沉淀密度明显高于Ar气氛处理后的硅片.同时发现在两种气氛下,延长恒温时间都可以降低洁净区厚度,增加氧沉淀密度.基于空位增强氧沉淀成核和氮化空位注入的基本原理,就RTA气氛和恒温时间对洁净区和氧沉淀分布的影响进行了讨论.     

A Process for Inline Minority Carrier Lifetime Monitoring for the Furnace Performing Denuded Zone Formation

The fluctuation in the minority carrier lifetime (MCLT) measurement is observed when monitoring the metal contamination for the furnace performing denuded zone formation, and the mechanism responsible for this phenomenon is examined in this paper. Among various possible causes, the oxygen precipitates are found to be the main contributor for this MCLT fluctuation because the amount of oxygen precipitates after denuded zone formation is strongly related to the initial oxygen concentration in the wafer and this makes the MCLT value liable to be affected even for tiny initial oxygen difference. A gate oxide recipe is suggested to be adopted for MCLT monitoring in furnace performing denuded zone formation to circumvent the problem. For the gate oxide recipe, not only is the monitoring result stable but it is feasible to produce MCLT test wafers with real products without sacrificing tool productivity.      

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.     

大直径直拉硅片的快速热处理

主要研究了快速热处理( RTP)对大直径直拉( CZ)硅片的清洁区( DZ)和氧沉淀的影响.通过在Ar、N2 、O2 三种不同气氛中,在不同温度下RTP发现在大直径CZ硅片中氧沉淀的行为及DZ的宽度与RTP的温度、气氛有很大关系.在实验的基础上,讨论了在大直径CZ硅中RTP对氧沉淀和DZ的影响机理.     

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.     

NTDCZSi内吸除技术的研究

利用中子嬗变掺杂(NTD)技术制备的CZSi(NTDCZSi)片在高温退火时,由于辐照缺陷与直拉硅中杂质氧的相互作用,可以加速内吸除(IG)效应的实现,获得理想的表面清洁区和体内吸杂区.本文探讨了将NTD技术与IG技术相结合的问题,并讨论了NTDCZSi IG效应机理.     

快速退火气氛对300mm CZ硅片吸杂效应和表面微观结构的影响

研究了N2和N2/NH3混合气两种不同气氛快速退火处理硅片对洁净区和氧沉淀分布的影响.研究发现:N2/NH3混合气氛处理的硅片在后序热处理中表层形成很薄的洁净区同时体内形成高密度的氧沉淀;而N2气氛处理的硅片的沽净区较厚、氧沉淀密度较低.但是两种气氛下延长恒温时间都可以降低洁净区厚度,增加氧沉淀密度.X射线光电子能谱和原子力显微镜扫描的结果显示N2/NH3混合气氛处理使表面出现了强烈的氮化反应,利用氮化反应町以解释快速退火气氛对洁净区分布的影响.     

快速退火气氛对300mm CZ硅片吸杂效应和表面微观结构的影响

研究了N2和N2/NH3混合气两种不同气氛快速退火处理硅片对洁净区和氧沉淀分布的影响.研究发现:N2/NH3混合气氛处理的硅片在后序热处理中表层形成很薄的洁净区同时体内形成高密度的氧沉淀;而N2气氛处理的硅片的沽净区较厚、氧沉淀密度较低.但是两种气氛下延长恒温时间都可以降低洁净区厚度,增加氧沉淀密度.X射线光电子能谱和原子力显微镜扫描的结果显示N2/NH3混合气氛处理使表面出现了强烈的氮化反应,利用氮化反应町以解释快速退火气氛对洁净区分布的影响.     

Anisotropic Etching of SiO2 in High-Voltage Gas-Discharge Plasmas

An experiment is reported on anisotropic etching in a CF₄–O₂plasma produced by high-voltage gas discharge. The process is applied to SiO₂and is also effected on SiC, Si, C (diamond), and As₂S₃. It is shown that the etch rate is mainly dependent on the oxygen percentage, plasma parameters, and the wafer temperature. It is established that etch rate is maximal at oxygen percentages of 0.8–1.5%, discharge currents of 80–140 mA, and wafer temperatures of 390–440 K. The etching is found to be uniform within 1%.     

Reliability studies of barrier layers for Cu/PAE low-k interconnects

Electromigration and electrical breakdown are two of the most important concerns in the reliability of modern electronic devices. The electromigration lifetimes and electrical breakdown field (E_BD) in single damascene copper lines/porous polyarylene ether (PAE) dielectric with different diffusion barrier materials (i.e., amorphous-SiC:H and TaN/Ta) were studied. The results showed a “wafer edge effect” in both groups of samples. The electromigration lifetime of samples taken from the center of the wafer is five to nine times longer of those taken from the wafer edge in the accelerated test. The samples from wafer edge showed a bi-modal failure characteristic. It was also found that electromigration resistance of the structure with new diffusion barrier a-SiC:H/Ta was comparable to that with the conventional TaN/Ta. On the other hand, the electrical testing showed that E_BD of the a-SiC:H/Ta structure is about twice of that with TaN/Ta barrier, indicating a significant improvement of the electrical performance.     

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.     

New oxygen donors formed at 700 °C in silicon

Donor formation at 700 °C was studied by infrared absorption, etching, transmission electron microscope, resistivity, and spreading resistance measurements in Czochralski grown silicon. The donor concentration is related to the oxygen-precipitate density, oxygen reduction, and carbon reduction by annealing at 700 °C. The donor distribution corresponds to the distribution of oxygen precipitates observed after annealing. The proposed donor is an oxygen precipitate nucleated at a carbon site. The oxygen-related donor formation not only occurs in the bulk of samples but also in the denuded zone. Donor-related microdefects do not seriously influence the threshold voltage in metal-oxide-silicon field-effects-transistors, but are expected to decrease carrier lifetime at the surface of the denuded zone.     

Quantifying charging damage in gate oxides of antenna structures for WLR monitoring

A new method to quantify the reliability risk for gate oxide with plasma induced charging damage (PID) is established. Based on existing antenna test methodology the quantity of inflicted damage is expressed in a physical meaningful number by means of a simple model applicable for thick oxides (>5 nm).This model takes trap activation, trap filling, detrapping and also traps generation under constant current test condition (“revealing stress”, “diagnostic stress”) into account. For the corresponding development of the measurable external supply voltage with time an equation is derived. Experimental test data from different oxide thicknesses are fitted to this model equation to obtain its main parameters, the cross section values. These cross section values describe the probabilities for the different trap/detrap processes during stress. Cross section values thus found extend published data for lower electric fields to high electric fields necessary for a fast test.The number of plasma induced traps, which was added to the oxide during wafer processing, can now be determined by applying an electron trapping rate (ETR) test method, and combining it with our dynamic trap generation/filling model. The obtained number of PID related traps opens a path to calculate the corresponding reduction of oxide lifetime. Real measurement data are used to illustrate the method and its applicability to fast wafer level reliability (fWLR) monitoring.     

Wafer level reliability: Process control for reliability

Wafer Level Reliability test techniques can be used to provide fast feedback process control information regarding the reliability of the product of a semiconductor process. The purpose of wafer level reliability (WLR) tests is the measurement of variation in the materials comprising the semiconductor device. They are not intended as modeling tools for the quantification of the effect of stress on these materials. As such, WLR tests must provide a repeatable stress, independent of normal process variation. The results of these tests will be a measurement of the “rate of degradation” of the basic circuit elements caused by a standard stress.     

In situ ageing, a development of the in situ techniques for building-in-reliability

A wafer level in situ accelerated ageing method is proposed. A development of in situ techniques for building-in approach to reliability is introduced, because “in situ” does not refer to the electrical testing during the ageing but it is referring to the ageing process itself. A He-Ne laser irradiation of the reverse biased junction is used for accelerating the local degradation by deep level generation currents - the hot spots formation. The efficiency of the method for wafer reliability monitoring was experimentally proved on RF power transistors.     

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。     

Unraveling the Mechanism of the Persistent Photoconductivity in Organic Phototransistors

Persistent photoconductivity (PPC) in organic phototransistors provides an opportunity and broad prospects to achieve many emerging applications in optoelectronic devices. However, a fundamental understanding of PPC behavior is still a key challenge impeding its practical applications. In this study, for the first time, a mechanism for electron trapping is presented in oxygen‐induced deep levels in organic semiconductors for the clarification of PPC behavior with solid evidence. Both theoretical simulation and experimental investigation unveil that oxygen in air atmosphere plays a decisive role in determining the PPC behavior. Oxygen molecules can induce deep defect levels in the energy bandgap of organic semiconductors, which will act as deep traps for photogenerated electrons. The trapped electrons will be maintained in the traps and undergo a very slow releasing process after light illumination, thus leading to a noticeable PPC behavior for the organic phototransistors. The proposed mechanism shows good universality and can be applicable to a host of organic semiconductors for explaining the PPC behaviors. This work reveals the significant role of oxygen in PPC behavior and also provides guidelines for controlling the unique PPC behavior toward device applications.     

Pheromone Propagation Controller: The Linkage of Swarm Intelligence and Advanced Process Control

Statistical process control (SPC) is traditionally used in advanced process control (APC). However, SPC, which treats measurements as a series of isolated statistical data, employs different methods to deal with different problems. In this paper, we present a new perspective on process control, which treats the intercepts of the process in different runs as a social insect colony. Our novel algorithm, called the pheromone propagation controller (PPC), is a meta-heuristic method based on the assumption that the intercepts of the linear regression model have their own behavior and affect others nearby on different runs. The pheromone basket is an environment initially filled with intercepts, and then the “intercepts pheromones” in the basket propagate according to the modified digital pheromone infrastructure. After propagation, the intercept in the next run can be forecast by extrapolating the last two entities of the pheromone basket. Consequently, a revised process recipe can be obtained from the forecast intercepts and the linear regression model. We also propose a workable scheme for adaptively tuning the PPC propagation parameter. We discuss the PPC stability region and the strategy for tuning the propagation parameter as well as the effects of size of pheromone basket, model mismatch on the performance. Our simulation results show that the standard deviation and the mean square error for PPC, whether fixed or self-tuning, are more consistent than that of the EWMA, the predictor corrector control (PCC), and the double EWMA for five types of anthropogenic disturbance. We also examined a hybrid disturbance obtained from semiconductor fabrication. When system drifts, the PPC was superior to the other candidate controllers for all values of the PPC propagation parameters and weightings of the other controllers, whether fixed or self-tuning.      

Onefold coordinated oxygen atom: an electron trap in the silicon oxide

It has been long suggested that the SiOH defect is an electron or “water” trap in silicon dioxide based on some indirect evidences. In this work, quantum calculation on the capturing properties of non-bridging oxygen hole center with unpaired electron SiO^√ and hydrogen defect SiOH in silicon oxide are performed with the ab initio density-functional method. It was found that the SiO^√ defect is an electron trap and this defect should be the responsible candidate for better hardness against radiation for the metal–oxide-semiconductor gate oxide produced by wet oxidation. We found that the SiOH defect could not be an electron trap according to the present calculation results.