多晶硅薄膜制备方法与压阻特性的研究

对磁控溅射和低压化学气相淀积(LPCVD)2种方法制备的多晶硅薄膜的电学和压阻特性进行了研究,并讨论了结晶化工艺对磁控溅射薄膜性质的影响。实验表明:LPCVD薄膜稳定性、重复性较好,应变系数可达到20以上;磁控溅射薄膜经适当结晶化工艺处理具有纳晶硅的结构特征,应变系数可达到80以上。利用扫描电镜(SEM)图片结合电阻率和应变系数的测试结果,讨论了2种方法制备出的多晶硅薄膜应用于压阻式力学量传感器的可行性。     

PECVD 工艺中氮化硅薄膜龟裂研究

PE 氮化硅薄膜优异的物理、化学性能使其在半导体分立器件、IC 电路中常被用作绝缘层、钝化层而使用。然而,氮化硅龟裂问题是影响其作为钝化层使用的阻碍因素,因此,科学的氮化硅工艺条件对其薄膜质量的影响非常关键。给出了等离子体化学气相淀积（PECVD）氮化硅薄膜技术的原理,通过实验验证,确定了诱发氮化硅龟裂现象的原因,优化工艺条件,确定了 PECVD氮化硅的最佳工艺条件,杜绝了龟裂现象对氮化硅作为钝化层使用的影响。     

不同淀积温度多晶硅纳米薄膜的压阻特性

重掺杂多晶硅纳米薄膜具有较大的应变系数和良好的温度特性,是制作力学量传感器的理想压阻材料.为优化多晶硅纳米薄膜的压阻特性,就淀积温度对低压化学气相淀积多晶硅纳米薄膜的压阻特性的影响进行了实验研究.在扫描电镜观测和X射线衍射实验基础上,利用隧道压阻模型分析了薄膜结构和压阻特性的关系.结果表明薄膜结构对应变系数的影响非常显著,但对应变系数的温度特性影响却很小.综合淀积温度对压阻特性和电导特性的影响,多晶硅纳米薄膜的最佳淀积温度在620℃左右.     

等离子体化学气相淀积TiO2薄膜材料

本文报导了以钛酸丁酯((C_4H_9O)_4Ti)为反应源物质,采用等离子体化学气相淀积(P-CVD)技术,在不同衬底上淀积出性能良好的TiO_2薄膜材料,并对其结构和气敏特性进行了初步研究。     

CVD淀积SiC薄膜SiH4,CH4的分解反应的计算机模拟研究

采用化学气相淀积淀积ＳｉＣ薄膜中ＳｉＨ４、ＣＨ４的分解产物种属进行数学建模,并结合相关热力学数据进行计算机模拟,得出ＳｉＨ４分解产物中以ＳｉＨ２为最多,ＣＨ４以ＣＨ２为最多,表明它们在淀积薄膜中是主要因素。     

一种降低影像传感器小丘的方法

正本发明涉及一种降低影像传感器小丘的方法,包括淀积粘合层、铝遮蔽、破真空和淀积抗反射层,粘合层为一层厚度为20~100的金属钛层,且金属钛层上淀积有一层厚度为200~300的氮化钛层,铝遮蔽的厚度为1000~3000,抗反射层厚度为300~600。在铝淀积完成后进行破真空处理,即离开腔体依靠空气缓慢冷却,释放应力,为尽可能的减少对产能的影响,破真空的时间控制在20~30min。本发明优化了铝遮蔽传统工艺,在铝淀积后采用破真空的方法来缓解铝薄膜的应力,解决小丘现象,本发明对比起传统铝遮蔽工艺,减少了小丘,降低了串扰,提高了传感器的质量。。A。A。A。A     

碳化硅薄膜的ICP浅刻蚀工艺研究

选用SF6/O2 混合气体对等离子体增强化学气相淀积( PECVD)法制备的碳化硅( SiC)薄膜进行了浅槽刻蚀,并通过正交试验设计方法,研究了感应耦合等离子体( ICP)刻蚀技术中反应室压强、偏压射频( BRF)功率、O2 比例三个工艺参数对碳化硅薄膜刻蚀速率的影响及其显著性.实验结果表明:BRF功率对于刻蚀速率的影响具有高度显著性,各因素对刻蚀速率的影响程度依次为BRF功率>反应室压强>O2 比例,并讨论了所选因素对碳化硅薄膜刻蚀速率的影响机理.     

多孔Al_2O_3薄膜的研制

在单晶Si片上热生长一层SiO2薄膜,再利用真空淀积的方法制备一层Al薄膜,然后通过铝阳极氧化的方法获得一层多孔Al2O3薄膜。利用JSM 35C扫描电子显微镜观测了该Al2O3薄膜的形貌。通过对Al2O3薄膜电阻与相对湿度关系的测试,发现其具有较好的感湿特性和较宽的感湿范围。     

透明导电氧化物AZO薄膜的制备与性能研究

利用直流磁控溅射法,采用氧化锌铝(98%ZnO+2%Al2O3)为靶材,在普通载玻片上制备了AZO(Z n O:Al)薄膜。采用X射线衍射仪、场扫描电镜对薄膜的结构及表面形貌进行了分析,采用分光光度计和四探针法对薄膜的光电学性能进行了测试。结果表明:控制好工艺参数可以制备出致密、均匀并具有良好的光电性能的AZO薄膜;并计算了带隙能量和折射率。     

光湿度传感器的折射率感湿机理

在综合分析了Maxwell-Garnett理论和有效介质理论的基础上,针对半导体湿敏陶瓷材料提出了一种新颖的复合模型,给出了以吸附参数和陶瓷材料气孔率为变量的薄膜折射率随湿度变化的理论关系。随着吸附参数的增大,SiO2薄膜的折射率增大;随着陶瓷材料气孔率的增大,SiO2薄膜的折射率将减小。利用薄膜折射率的变化检测湿度,灵敏度可以达到10^-3数量级。通过计算机理论模拟与AlbertoAH等人所做的实验结果对比,证明了该模型的正确性。     

PECVD-SiOxNy films for large area self-sustained grids applications

In this work we study the structural properties and mechanical stress of silicon oxynitride (SiO_xN_y) films obtained by plasma enhanced chemical vapor deposition (PECVD) technique at low temperatures (320 °C) and report the feasibility of using this material for the fabrication of large area self-sustained grids. The films were obtained at different deposition conditions, varying the gas flow ratio between the precursor gases (N₂O and SiH₄) and maintaining all the other deposition parameters constant. The films were characterized by ellipsometry, by Fourier transform infrared (FT-IR) spectroscopy and by optically levered laser technique to measure the total mechanical stress. The results demonstrate that for appropriated deposition conditions, it is possible to obtain SiO_xN_y with very low mechanical stress, a necessary condition for the fabrication of mechanically stable thick films (up to 10 μm). Since this material (SiO_xN_y) is very resistant to KOH wet chemical etching it can be utilized to fabricate, by silicon substrate bulk micromachining, very large self-sustained grids and membranes, with areas up to 1 cm² and with thickness in the 2–6 μm range. These results allied with the compatibility of the PECVD SiO_xN_y films deposition with the standard silicon based microelectronic processing technology makes this material promising for micro electro mechanical system (MEMS) fabrication.     

Smart ultrasonic sensors systems: potential of aluminum nitride thin films for the excitation of the ultrasound at high frequencies

We investigated the potential of the aluminum nitride films to excite ultrasonic waves at frequencies >50?MHz. The deposition process of the aluminum nitride thin film layers on silicon substrates was investigated and optimized regarding their piezoelectric behavior. Large single element transducers were deposited on silicon substrates with aluminum electrodes, under different parameters for the magnetron sputter process, like pressure and bias voltage. Special test setup and a measuring station were created to characterize the sensors. Acoustical measurements were carried out in pulse echo mode up to 500?MHz and the values of piezoelectric charge constant (d₃₃) were determined. As a result, two parameter sets were found for the sputtering process to obtain an excellent piezoelectric charge constant of about 7.2?pC/N maximum. Then the sputtering process with these parameters was used to deposit sensors on various substrate materials and with different electrode sizes.     

Microstenciling: a generic technology for microscale patterning of vapor deposited materials

The fabrication of microstencils for patterning on unconventional substrates was demonstrated. Stencil feature sizes ranging from 6 to 370 /spl mu/m with aspect ratios (stencil feature height :width) in the range of 0.5 : 1 to 15 : 1 were fabricated using ICP etching of silicon. The stenciling process was demonstrated for the deposition of metals (Ti/Au) and dielectrics (silicon dioxide) onto silicon, glass, and polymer based substrates for microfluidic system development. The results demonstrated some dependency of the deposition rate on the stencil feature size and aspect ratio. Results from adhesion studies showed excellent adhesion on all substrates with the exception of PMMA.     

LIGA fabrication of nanocrystalline Ni–W alloy micro specimens from ammonia-citrate bath

Ammonia-citrate bath has been investigated for the deposition of nano crystalline Ni–W alloy micro components using the LIGA process. First the bath stability and deposit characteristics were studied. Fabrication of micro specimens were then carried out on silicon substrates covered with novolac as well as thick PMMA resist for LIGA. Effects of different parameters like current density, nickel ion and tungsten ion concentration in the bath, deposition time etc. on the deposit characteristics and current efficiency were studied. The deposited Ni–W samples were characterized by scanning electron microscopy, energy depressive X-ray spectroscopy, light optical microscopy and X-ray diffraction. Results show that during a few tens of hours of deposition, ammonia loss from the covered bath used is minimal and the bath remains stable. Selection of proper bath and deposition parameters allows a window for the deposition of crack free, thick, nano crystalline nickel–tungsten alloys. Using the optimum parameters, it has been possible to fabricate Ni-12 at% W micro tensile specimens with a nominal thickness of 120 μm by the LIGA process.     

Neural network modeling of inter-characteristics of silicon nitride film deposited by using a plasma-enhanced chemical vapor deposition

Neural network have been widely used to model a relationship between process parameters (or in situ diagnostic variables) and film qualities. A new neural network model relating inter-relationship between the film qualities, not the process parameters is constructed by using a generalized regression neural network and a genetic algorithm. This approach is applied to the lifetime of silicon nitride films deposited by using a plasma-enhanced chemical vapor deposition system. The lifetime is an important quality that determines the efficiency of solar cells. The other film qualities examined are a deposition rate, a refractive index, and a charge density. For a systematic modeling, the deposition process was modeled by using a statistical experiment. Compared to conventional and statistical regression models, the optimized GRNN model demonstrated an improvement of 73% and 81%, respectively. The model predicted important and useful clues to optimizing the lifetime. It is noticeable that higher lifetime was achieved at lower deposition rate. This was also noted as the charge density was decreased. The refractive index played a critical role in improving the lifetime.     

中国微米纳米 基于光诱导电化学沉积的金属微电极加工方法

纳米材料具有独特的物理化学性质,在纳米电子器件和生物传感等方面显示了巨大的应用潜力.基于二维纳米材料的器件,需要利用金属电极来构建传感器或者场效应晶体管结构.目前,已有一些方法来制备金属电极,如光刻、聚焦离子束及纳米压印等方法,但是这些方法通常需要昂贵的设备,并且操作非常复杂.提出采用基于光诱导的金属纳米电极沉积方法,通过对多个实验参数(包括输入交流电信号的频率、幅值、溶液浓度以及氢化非晶硅层厚度)的分析,得到了优化的金属电极沉积条件.在此基础上,利用光学显微镜、原子力显微镜和扫描电子显微镜对制备的金属电极进行了表征.     

Copper-encapsulated silicon micromachined structures

Selective copper encapsulation on silicon has been used to fabricate micromachined devices such as inductors with quality factors over 30 at frequencies above 5 GHz. The devices are fabricated using either polysilicon surface micromachining, or integrated polysilicon and deep reactive ion etching bulk silicon micromachining. Their exposed silicon surfaces are selectively activated by palladium activation, which allows the subsequent copper deposition on the activated silicon surfaces only. This silicon encapsulated-with-copper technique takes advantage of both the excellent mechanical properties of silicon (to maintain structural integrity), and the high conductivity of copper (for electrical signal transmission). Furthermore, the process not only minimizes interfacial forces typical of physical metal deposition on silicon, but also balances the forces by metal encapsulation on all sides of the silicon structures     

Microstructuring of silicon by electro-discharge machining (EDM) — part I: theory

Currently, nearly all microcomponents are fabricated by micro-electronic production technologies like etching, deposition and other (photo) lithographic techniques. In this way, main emphasis has been put on surface micromechanics. The major challenge for the future will be the development of real three-dimensional microstructures. The main objective of the proposed research is the development of a production technology for three-dimensional micromechanical structures together with a study of the mechanical properties of these structures. Electrodischarge machining (EDM) is a versatile technique which is very well suited for machining complex microstructures. This paper starts with an overview of EDM technology, the current state-of-the-art of micro EDM, and a comparison of EDM with other micromachining technologies. Afterwards, the basic parameters for EDM of silicon are derived. It will be demonstrated that EDM of silicon is not only feasible, but also forms an interesting, powerful and complementary alternative to traditional silicon micromachining.     

Realisation and characterisation of mass-based diamond micro-transducers working in dynamic mode

We report on novel MEMS micro-transducers made of diamond and targeted for bio-sensing applications. To overcome the non-straightforward micromachining of diamond, we developed a bottom up process for the fabrication of synthetic diamond micro-structures involving the patterned growth of diamond using the CVD (chemical vapour deposition) technique, inside micro-machined silicon moulds. Here typical resonant MEMS structures including cantilevers fabricated using this method were characterized by measuring their first mode resonance (frequency and Q-factor) by Doppler laser interferometry. The experimental data matched the simulation data. Data from bare diamond cantilevers and from diamond cantilevers with actuation gold track on the surface were compared and showed a significant decrease in the resonant frequency in the presence of gold tracks. Nevertheless, comparisons with equivalent silicon structures demonstrated the superior performances of diamond cantilevers: the resonance frequencies were twice higher and the Q-factors 2.5 times higher for the diamond transducers. Diamond cantilevers sensitivity were measured using PMMA deposition and values as high as 227.4 Hz ng⁻¹ were found. It was shown that diamond mass sensitivity values are typically two times higher than identical silicon devices. Finally, the limit of detection (LOD) of diamond cantilevers was found experimentally to be as low as 0.86 pg using our set up. This is suitable for many bio-sensing applications.     

Wafer-Scale Manufacturing of Bulk Shape-Memory-Alloy Microactuators Based on Adhesive Bonding of Titanium–Nickel Sheets to Structured Silicon Wafers

This paper presents a concept for the wafer-scale manufacturing of microactuators based on the adhesive bonding of bulk shape-memory-alloy (SMA) sheets to silicon microstructures. Wafer-scale integration of a cold-state deformation mechanism is provided by the deposition of stressed films onto the SMA sheet. A concept for heating of the SMA by Joule heating through a resistive heater layer is presented. Critical fabrication issues were investigated, including the cold-state deformation, the bonding scheme and related stresses, and the titanium–nickel (TiNi) sheet patterning. Novel methods for the transfer stamping of adhesive and for the handling of the thin TiNi sheets were developed, based on the use of standard dicing blue tape. First demonstrator TiNi cantilevers, wafer-level adhesively bonded on a microstructured silicon substrate, were successfully fabricated and evaluated. Intrinsically stressed silicon dioxide and silicon nitride were deposited using plasma-enhanced chemical vapor deposition to deform the cantilevers in the cold state. Tip deflections for 2.5-mm-long cantilevers in cold/hot state of 250/70 and 125/28 ${rm mu}hbox{m}$ were obtained using silicon dioxide and silicon nitride, respectively. The bond strength proved to be stronger than the force created by the 2.5-mm-long TiNi cantilever and showed no degradation after more than 700 temperature cycles. The shape-memory behavior of the TiNi is maintained during the integration process.$hfill$[2009-0085]