Numerical simulations of conduction and low-frequency noise in polysilicon thin film transistors

Numerical simulations of static conduction and low-frequency noise are carried out in N-channel polysilicon thin film transistors. The Meyer-Neldel effect associated with the drain current is related to trapping/detrapping processes of carriers from dangling bonds located at the interface. Low-frequency noise is simulated by generation-recombination processes. The sources responsible of noise in the thin film transistors are mainly located close to the interface. The microscopic parameter deduced from numerical simulation is lower than the macroscopic one deduced from noise measurements. The ratio of these two parameters is considered as a factor of merit to qualify thin film transistor technology.     

Dependence of photovoltaic parameters on grain size and density of states in n-i-p and p-i-n polycrystalline silicon solar cells

One-dimensional modeling of polycrystalline silicon (pc-Si) p⁺-i-n⁺ and n⁺-i-p⁺ homojunctions under AM1.5 light is presented. Single-crystalline grains separated by amorphous silicon transition zones are introduced to model the pc-Si structure. The usual density of states (DOS) with exponential band-tails and Gaussian-distributed deep levels is assumed in these transition regions. Effects of the grain size, the thickness of the undoped region and the DOS on the photovoltaic characteristics are presented. The calculation enables us to understand the very poor performance of the solar cells based on solid-phase-crystallized polysilicon processed at low temperature (< 600 °C). It gives the minimum value of the grain size and the maximum DOS to obtain acceptable photovoltaic performance.     

国内外多晶硅工业现状

回顾了2005～2006年国内外多晶硅生产现状及2010年前全球多晶硅生产商扩产计划和达产目标，并概括了目前多晶硅生产新工艺。提出全球在2008年以后太阳能级多晶硅产能与太阳能硅电池的需求逐渐趋于平衡，供需矛盾缓和，价格开始回落；太阳能级多晶硅的主流生产工艺仍然是化学法，冶金精炼法将来能成为一种补充；至2010年中国的太阳能级多晶硅工业将在世界上占一席之地；但国内太阳能级多晶硅厂商，在2010年尚不能掌握西门子法低成本工艺、副产品的综合利用及环保技术，将会陷入困境。     

多晶硅产业对环境的污染初探

多晶硅是太阳能电池材料之一,具有比较高的光电转换效率,但多晶硅产业的发展也导致环境污染的产生。本文主要从多晶硅太阳电池生产环节前期工序（硅提纯）和中期工序（清洁制绒、扩散制结、刻蚀清洁、化学气相沉积PECVD、丝网印刷、电极烧结）中所产生的污染进行论述。     

Boron diffusion and activation in polysilicon multilayer films for P MOS structure: Characterization and modeling

This work deals with in situ boron diffusion and activation in multilayer films: polysilicon (Poly1)/amorphous silicon (Poly2). These films are deposited by LPCVD technique. However, several heat treatments were carried in order to determine the optimal annealing conditions to suppress boron penetration from the gate to the substrate through the gate oxide in MOS structure. The boron concentration is monitored by secondary ion mass spectrometry (SIMS). To investigate SIMS profiles we proposed a model of boron diffusion into these multilayer structures. It is important to note that the parameter values of the studied films such as the diffusion coefficient, the activation percentage of boron as well as the acceleration rate of boron diffusion are deduced from adjustment of simulated profiles with experimental profiles. From these results, we inferred that the boron is electrically active and its distribution does not reach the oxide layer and consequently, the Poly2 may reduce the boron diffusion in optimal annealing conditions.     

Kaibel隔板塔用于多晶硅还原工段三氯氢硅分离的模拟研究

将Kaibel隔板塔代替常规三塔顺序分离流程用于多晶硅还原工段中三氯氢硅分离。在简捷计算基础上,利用Multifrac模型进行了严格稳态模拟。主要研究了TCS产品和STC产品采出位置、液体分配比和汽体分配比等参数的影响。结果表明：与常规三塔顺序分离流程相比,Kaibel隔板塔可节约能耗26.43%,设备数量大大减少。     

多晶硅发射极晶体管的低温频率特性研究

本文考虑低温下半导体中载流子冻析效应和浅能级杂质的陷阱效应等因素,分析了多晶硅发射极晶体管的低温频率特性。研究表明,受载流子冻析效应的影响,基区电阻在低温下随温度下降接近于指数上升,使晶体管的频率性能变环;而由于浅能级杂质的陷阱效应,低温下基区和发射区渡越时间变长,截止频率下降。这些因素在低温器件设计中应予重视。     

Ultra uniform arrays of micro patterns on large area substrate by employing wet chemical etching

A wet chemical selective etching process is presented to delineate ultra-uniform micro patterns in the form of arrays of sensor chips of 4 mm×4 mm size in the matrix of 9×9 on a 3″ diameter silicon substrate with uniform physical and electrical characteristics. The selective etching of thin film is confined to the top area by masking its outer edges. This leads to uniform etching of the entire film leading to ultra-uniform delineation of arrays of micro patterns. The process has been verified over the selective etching of doped polysilicon in defining the polysilicon resistors and subsequently has been applied on realizing Ti/Au interconnecting lines using wet chemical etchant. Experimental results are presented with physical and electrical characteristics of the patterned structures in the statistical form over the substrate surface. SEM analysis is carried out for physical dimension measurement and standard deviation of 0.0040 is observed in polysilicon micro patterning. The process is competitive with reactive ion etching (RIE) in terms of yield, reliability and repeatability with cost effectiveness in a production environment. Methodology of ultra-uniform etching on entire substrate area is developed in support of the experimental results. The ratio of Top Surface Area (TSA) and Total Exposed Surface Area (TESA) is shown as crucial parameter for the uniform etching of thin films.     

多晶硅金刚线切割废料制备Al-Si合金过程中的热力学和动力学分析

通过X射线衍射仪、X射线荧光光谱分析仪、傅里叶变换红外光谱仪分析了金刚线切割多晶硅废料的组分及其体系中存在的硅氧化物，研究了铝与切割废料合金化过程中可能存在的化学反应过程，采用HSC Chemistry 6.0软件对其反应体系进行了热力学分析，利用差热分析法研究了铝热还原切割废料中SiO2的动力学过程，对金刚线切割多晶硅废料进行了掺铝制备铝硅合金的实验研究。结果表明，金刚线切割多晶硅废料和铝粒按不同铝硅摩尔比兑掺后，在电磁搅拌的作用下，合金化的温度范围为800~1600℃，铝热反应可将废料中少量的SiO2杂质还原成单质Si，铝热还原二氧化硅的活化能为364.1 kJ/mol，反应级数为0.91，实验样品的EPMA和XRD等表征结果表明合金成分和渣相与热力学分析完全吻合，合金化效果明显。     

DDL-500型多晶硅铸锭炉的开发与设计

在降低多晶硅成本及提高生产效率的前提下,对多晶硅铸锭炉进行了研究调查,通过对多晶硅铸锭炉结构进行改进,对热场等关键部位进行了重新的开发设计,提高了单炉单次的生产量,满足生产要求。