基于BCB键合的MEMS加速度计圆片级封装工艺

对基于BCB的圆片级封装工艺进行了研究,该工艺代表了MEMS加速度计传感器封装的发展趋势,是MEMS加速度计产业化的关键。选用3000系列BCB材料进行MENS传感器的粘结键合工艺试验,解决了圆片级封装问题,在低温250℃和适当压力辅助下≤2．5bar（1bar=100kPa）实现了加速度计的圆片级封装,并对相关的旋涂、键合、气氛、压力等诸多工艺参数进行了优化。     

用苯并环丁烯进行圆片级硅–硅气密性键合

应用苯并环丁烯(BCB)材料对硅片进行了圆片级低温键合,并研究了其在气密性封装工艺中的应用。测试表明:在250℃的低温键合条件下,封装后样品的气密性优于3.0×10–4Pa.cm3/sHe;剪切力达4.7MPa以上;封装样品合格率达94%以上;通过热循环可靠性测试之后仍具有很好的气密性。BCB是一种较理想的圆片级低温气密性健合封装材料。     

一种真空度可调的圆片级封装技术

提出了一种MEMS器件的圆片级封装技术。通过金硅键合和DRIE通孔制备等关键工艺技术,可以实现真空度从102 Pa到2个大气压可调的圆片级封装。作为工艺验证,成功实现了圆片级真空封装MEMS陀螺仪的样品制备。对封装后的陀螺仪样品进行了剪切力和品质因数Q值测试,剪切力测试结果证明封装样品键合强度达到5 kg以上,圆片级真空封装后陀螺的品质因数Q值约为75 000,对该陀螺的品质因数进行了历时1年的跟踪测试,在此期间品质因数Q的最大变化量小于7‰,品质因数测试结果表明封装具有较好的真空特性。     

MEMS低温圆片级键合密封工艺研究

研究了一种使用非光敏苯并环丁烯(BCB)材料的低温硅片级键合,并将其用于压力谐振传感器封装.采用AP3000作为BCB中的黏结促进剂,将谐振片与硅片或Pyrex 7740玻璃晶圆键合,程序简单,低成本,密封性能较高,且键合温度低于250℃.通过拉伸实验,这种键合的剪切强度高于40 MPa.所以此硅片级键合适用于压力传感器的封装.     

高g微机械加速度传感器芯片盖帽封装设计北大核心

为了提高高g微机械加速度传感器在极端恶劣环境中应用的可靠性,根据自制的高g微机械加速度传感器芯片,研究设计了一种新型＂台阶式＂传感器芯片的盖帽封装结构。利用圆片级键合工艺和有限元分析（FEA）方法确定了盖帽封装结构材料与尺寸的设计方案。优化微电子机械系统（MEMS）加工工艺流程完成对盖帽封装结构的加工,并通过数字电子拉力机对实现圆片级盖帽封装的传感器芯片进行键合强度测试。测试结果表明,键合强度为35 000 kPa,远大于抗过载封装设计要求下的键合强度值（401.2 kPa）,证明了盖帽封装结构设计的可行性和可靠性。     

基于聚合物介质的低温硅硅键合研究

聚合物低温键合技术是MEMS器件圆片级封装的一项关键技术。以苯并环丁烯(BCB)、聚对二甲苯(Parylene)、聚酰亚胺(Polyimide)、有机玻璃(PMMA)作为键合介质,对键合的温度、压力、气氛、强度等工艺参数进行了研究,并分析了其优缺点。通过改变Parylene的旋涂、键合温度、键合压力、键合时间等工艺参数进行了优化实验。结果表明,在230 ℃的低温键合条件下封装后的MEMS器件具有良好的键合强度(＞3.600 MPa),可满足MEMS器件圆片级封装要求。     

基于微谐振器的圆片级真空封装真空度测试技术

针对微电子机械系统(MEMS)圆片级封装腔体体积小、传统的真空封装测试方法适用性差的情况,研制了一种用于表征圆片级真空封装真空度的器件——MEMS微谐振器。利用此谐振器不仅可以表征圆片级真空封装真空度,也可用于圆片级真空封装漏率的测试。采用MEMS体硅工艺和共晶圆片键合技术实现了微谐振器的圆片级真空封装,利用微谐振器阻尼特性建立了谐振器品质因数与真空度的对应关系,通过设计的激励电路实现了微谐振器品质因数的在片测试,对不同键合腔体真空度下封装的MEMS微谐振器进行测试,测试结果显示该微谐振器在高真空度0.1～8 Pa范围内品质因数与真空度有很好的对应关系。     

应用BCB材料进行硅-玻璃气密性封装的实验与理论研究

应用苯并环丁烯(BCB)材料对硅片和玻璃片进行了250℃下的圆片级低温键合实验,同时进行了300℃下的硅片与玻璃片阳极键合实验,并对其气密性和剪切力特性进行了对比研究.测试结果表明:在250℃的低温键合条件下,经过500kPa He气保压2h,BCB封装后样品的气密性达到(5.5±0.5)×10-4Pa cc/s He;剪切力在9.0～13.4 MPa之间,达到了封装工艺要求;封装成品率达到100%.这表明应用BCB材料键合是一种有效的圆片级低温气密性封装方法.还根据渗流模型理论,讨论了简易模型下气密性(即渗流率)和器件腔体边缘到划片边缘的间距的关系.     

应用BCB材料进行硅-玻璃气密性封装的实验与理论研究

应用苯并环丁烯(BCB)材料对硅片和玻璃片进行了250℃下的圆片级低温键合实验,同时进行了300℃下的硅片与玻璃片阳极键合实验,并对其气密性和剪切力特性进行了对比研究.测试结果表明:在250℃的低温键合条件下,经过500kPa He气保压2h,BCB封装后样品的气密性达到(5.5±0.5)×10-4Pa cc/s He;剪切力在9.0～13.4 MPa之间,达到了封装工艺要求;封装成品率达到100%.这表明应用BCB材料键合是一种有效的圆片级低温气密性封装方法.还根据渗流模型理论,讨论了简易模型下气密性(即渗流率)和器件腔体边缘到划片边缘的间距的关系.     

应用BCB材料进行硅-玻璃气密性封装的实验与理论研究

应用苯并环丁烯(BCB)材料对硅片和玻璃片进行了250℃下的圆片级低温键合实验，同时进行了300℃下的硅片与玻璃片阳极键合实验，并对其气密性和剪切力特性进行了对比研究. 测试结果表明：在250℃的低温键合条件下，经过500kPa He气保压2h, BCB封装后样品的气密性达到(5.5±0.5)E-4Pacc/s He；剪切力在9.0~13.4MPa之间，达到了封装工艺要求；封装成品率达到100%. 这表明应用BCB材料键合是一种有效的圆片级低温气密性封装方法. 还根据渗流模型理论，讨论了简易模型下气密性（即渗流率）和器件腔体边缘到划片边缘的间距的关系.     

Zero-level packaging using BCB adhesive bonding and glass wet-etching for W-band applications

A small size zero-level packaging method, by using wafer-level benzocyclobutene (BCB) adhesive bonding and a pyrex glass wet-etching technique, is presented. A simple process was developed to make a pyrex glass to have housing cavities and BCB sealing ring for a packaging. During a wet-etching of glass for making a cavity and pad feedthroughs, BCB was protected by 1.2 /spl mu/m-thick AZ1512 photoresist. To estimate a pyrex 7740 packaging material in W-band, a 50 W coplanar waveguide (CPW) was designed and an insertion loss (S/sub 12/) was measured. The insertion loss change of CPW lines by the fabricated package is below 0.1 dB from DC to 110 GHz.     

BCB-to-oxide bonding technology for 3D integration

Process optimization of BCB polymer to silicon oxide bonding was investigated. The suitable bonding temperature is about 300 °C, while bond failure of BCB-to-oxide bonding is observed starting from 400 °C. Bonding interface morphologies and bond strengths of BCB-to-oxide bonding were investigated as well. PECVD oxide to BCB bonding has better bonding quality than that of thermal oxide to BCB bonding. Si–O–Si bonds may be the reason of a strong BCB to oxide bonding. Water molecules link BCB and oxide surfaces during the initial contact, while Si–O–Si bonds are formed during bonding. This proposed mechanism of BCB-to-oxide bonding provides a guideline for polymer to oxide hybrid bonding technology in 3D integration.     

Intermediate wafer level bonding and interface behavior

The paper presents a new silicon wafer bonding technique. The high-resolution bonding pad is defined through photolithography process. Photosensitive materials with patternable characteristics are served as the adhesive intermediate bonding layer between the silicon wafers. Several types of photosensitive materials such as SU-8 (negative photoresist), AZ-4620 (positive photoresist), SP341 (polyimide), JSR (negative photoresist) and BCB (benzocylbutene) are tested and characterized for their bonding strength. An infrared (IR) imaging system is established to examine the bonding results. The results indicate that SU-8 is the best bonding material with a bonding strength up to 213 kg/cm² (20.6 MPa) at bonding temperature less than 90 °C. The resolution of bonding pad of 10 μm can be achieved. The developed low temperature bonding technique is particularly suitable for the integration of microstructures and microelectronics involved in MEMS and VLSI packaging processes.     

Packaging using microelectromechanical technologies and planarcomponents

A novel millimeter-wave packaging structure was developed in which a micromachined low-loss planar component and flip-chip devices were integrated on a silicon substrate. A low-loss planar filter was achieved on a 7-mm-square silicon substrate employing an inverted microstrip line and a unique resonator. High attenuation in the stopband was also obtained by introducing a pole control technique. Fabrication of a compact K-band receiver front-end incorporating a built-in filter was realized using multilayered benzocyclobutene (BCB) and flip-chip bonding techniques. Furthermore, we propose an alternative BCB suspended structure and demonstrate a planar antenna for Ka-band applications. These technologies bring to reality high-performance compact packaged systems in millimeter-wave region applications     

Processing and Characterization of Dry-Etch Benzocyclobutene as Substrate and Packaging Material for Neural Sensors

Electrode substrate is one of the most important factors affecting the recording or stimulation efficiency and long-term stability of chronically implanted neural sensors for laboratory research. Various biocompatible polymers have been investigated as potential substrate and packaging material for neural sensors in neuroscience research applications. Dry-etch benzocyclobutene (BCB) is one candidate due to its desirable combination of electrical, mechanical, and thermal properties and its biocompatibility. In this paper, processing techniques were investigated to control the uniformity and pin-pole density of dry-etch BCB film. Dry-etch BCB film as thick as 25 mum with a surface roughness less than 1000 A and a pinhole density less than 1.5 x 10^-3 mm^-2 has been acquired using an optimized coating and curing recipe. A traditional surface micro-machining technique was used to form the metallization and etch masks during the fabrication of the neural electrode based on dry-etch BCB substrate. Special consideration was given to the study of dry-etch BCB thin film patterning using plasma reactive ion etching dry etching. The optimized plasma etch condition shows that greater than 1 mum etch rate and 65deg via angle are the most suitable for the packaging and patterning of the neural probes. The results show that this fabrication process is optimal for chronically implantable neural sensors based on dry-etch BCB thin film as substrate. The process may find applications in other devices using BCB as substrate.     

A wafer-level 3D packaging structure with Benzocyclobutene as a dielectric for multichip module fabrication

A new wafer-level 3D packaging structure with Benzocyclobutene (BCB) as interlayer dielectrics (ELDs) for multichip module fabrication is proposed for application in the Ku-band wave. The packaging structure consists of two layers of BCB films and three layers of metallized films, in which the monolithic microwave IC (MMIC), thin film resistors, striplines and microstrip lines are integrated. Wet etched cavities fabricated on the silicon substrate are used for mounting active and passive components. BCB layers cover the components and serve as ILDs for interconnections. Gold bumps are used as electric interconnections between different layers, which eliminates the need to prepare vias by costly dry etching and deposition processes. In order to get high-quality BCB films for the subsequent chemical mechanical planarization (CMP) and multilayer metallization processes, the BCB curing profile is optimized and the roughness of the BCB film after the CMP process is kept lower than 10 nm. The thermal, mechanical and electrical properties of the packaging structure are investigated. The thermal resistance can be controlled below 2 ℃/W. The average shear strength of the gold bumps on the BCB surface is around 70 N/mm~2. The performances of MMIC and interconnection structure at high frequencies are optimized and tested. The 5 -parameters curves of the packaged MMIC shift slightly showing perfect transmission character. The insertion loss change after the packaging process is less than 1 dB range at the operating frequency and the return loss is less than -8 dB from 10 to 15 GHz.     

Indirect Wafer Bonding and Epitaxial Transfer of GaSb-Based Materials

Results from a study of indirect wafer bonding and epitaxial transfer of GaSb-based materials are presented. Benzocyclobutene (BCB) was used as a bonding agent to bond GaSb and epitaxial structures lattice matched to GaSb onto Si, GaAs, and sapphire carrier substrates. To better understand sources of stress during the bonding process, which can result in cracking and subsurface damage of the GaSb-based materials, BCB’s hardness and reduced elastic modulus were measured at various stages during the curing process. Based on the results of curing experiments, a bonding and epitaxial transfer process for GaSb-based materials was then developed. Following bonding, using an experimentally determined low-stress cure cycle, GaSb substrates were removed from epitaxial layers of InAsSb using a combination of mechanical thinning and polishing followed by selective chemical etching using a hydrofluoric and chromic acid solution. Etch selectivity data are also presented where selectivity greater than 100:1 is achieved for GaSb:InAsSb.