用于微机械器件和微电子机械系统的关键技术：微机械技术

微机械技术是研究，生产微机械器件和微电子机械诉关键技术，熟练掌握并不容易。本文总结了三个单位为时数年在微机械技术方面的研究成果，重点介绍我们首创的三项技术，即自对准的准三维加工技术，硅三维结构的无掩模腐蚀技术和硅／硅低温直接键合技术，也提到我们开展过的其他几项微机械技术以及所制作的几种微机械器件的参数或结果。     

聚焦离子束无掩模刻蚀研究

利用镓源二级透镜聚焦离子束装置在半导体基片上进行了一系列的无掩模刻蚀实验研究，在不同材料上刻蚀了各种图形，总结分析了不同参数的聚焦离子束对刻蚀的影响。     

HV‐SoP Technology for Maskless Fine‐Pitch Bumping Process

Recently, we have witnessed the gradual miniaturization of electronic devices. In miniaturized devices, flip‐chip bonding has become a necessity over other bonding methods. For the electrical connections in miniaturized devices, fine‐pitch solder bumping has been widely studied. In this study, high‐volume solder‐on‐pad (HV‐SoP) technology was developed using a novel maskless printing method. For the new SoP process, we used a special material called a solder bump maker (SBM). Using an SBM, which consists of resin and solder powder, uniform bumps can easily be made without a mask. To optimize the height of solder bumps, various conditions such as the mask design, oxygen concentration, and processing method are controlled. In this study, a double printing method, which is a modification of a general single printing method, is suggested. The average, maximum, and minimum obtained heights of solder bumps are 28.3 μm, 31.7 μm, and 26.3 μm, respectively. It is expected that the HV‐SoP process will reduce the costs for solder bumping and will be used for electrical interconnections in fine‐pitch flip‐chip bonding.     

Cubic Phase GaN on Nano‐grooved Si (100) via Maskless Selective Area Epitaxy

A method of forming cubic phase (zinc blende) GaN (referred as c‐GaN) on a CMOS‐compatible on‐axis Si (100) substrate is reported. Conventional GaN materials are hexagonal phase (wurtzite) (referred as h‐GaN) and possess very high polarization fields (～MV/cm) along the common growth direction of <0001>. Such large polarization fields lead to undesired shifts (e.g., wavelength and current) in the performance of photonic and vertical transport electronic devices. The cubic phase of GaN materials is polarization‐free along the common growth direction of <001>, however, this phase is thermodynamically unstable, requiring low‐temperature deposition conditions and unconventional substrates (e.g., GaAs). Here, novel nano‐groove patterning and maskless selective area epitaxy processes are employed to integrate thermodynamically stable, stress‐free, and low‐defectivity c‐GaN on CMOS‐compatible on‐axis Si. These results suggest that epitaxial growth conditions and nano‐groove pattern parameters are critical to obtain such high quality c‐GaN. InGaN/GaN multi‐quantum‐well structures grown on c‐GaN/Si (100) show strong room temperature luminescence in the visible spectrum, promising visible emitter applications for this technology.     

一种数字光栅无掩模光刻对准方法

针对数字微反射镜装置(DMD)无掩模光刻系统,提出并研究了一种数字光栅无掩模光刻对准方法,将硅片的微位移放大显示在数字光栅与硅片物理光栅叠加产生的叠栅条纹中。建立了基于DMD的数字光栅无掩模光刻对准模型,设计了对准标记以及具体的实现方案,并对模型进行了数值仿真和初步的实验验证。结果表明,采用频率可变、图像干净、具有良好周期性结构的数字光栅代替传统的真实掩模光栅,真正实现了零掩模成本;并且采用变频率数字光栅可以扩大测量范围,减小位移测量误差。最终可以实现深亚微米的对准精度,满足目前无掩模光刻对准精度的要求。     

Three-dimensional fluidic self-assembly by axis translation of two-dimensionally fabricated microcomponents in railed microfluidics

A method for high-throughput 3D self-assembly of 2D photopatterned microstructures using railed microfluidics is presented. Vertical device patterning of heterogeneous materials requires high-level integration using conventional microelectromechanical system (MEMS) technology; however, 3D railed assembly enables easy and fast self-assembly via a fluidic axis-translation process and simple material exchange in microfluidic channels. Individually photopatterned 2D microstructures are axis-translated from in-plane to out-of-plane and fluidically self-assembled, guided by side-rails in microfluidic channels to form a 3D morphology. Since the structures are fabricated in fluidic environments, there are no fixed initial points on the channel substrate allowing fluidic horizontal stacking of erected 2D structures. The guiding mechanism of railed microfluidics enables efficient fluidic handling and deterministic 3D self-assembly of heterogeneous components such as electronic components or polymeric microstructures using only fluidic force.     

Interconnection Technology Based on InSn Solder for Flexible Display Applications

A novel interconnection technology based on a 52InSn solder was developed for flexible display applications. The display industry is currently trying to develop a flexible display, and one of the crucial technologies for the implementation of a flexible display is to reduce the bonding process temperature to less than 150°C. InSn solder interconnection technology is proposed herein to reduce the electrical contact resistance and concurrently achieve a process temperature of less than 150°C. A solder bump maker (SBM) and fluxing underfill were developed for these purposes. SBM is a novel bumping material, and it is a mixture of a resin system and InSn solder powder. A maskless screen printing process was also developed using an SBM to reduce the cost of the bumping process. Fluxing underfill plays the role of a flux and an underfill concurrently to simplify the bonding process compared to a conventional flip‐chip bonding using a capillary underfill material. Using an SBM and fluxing underfill, a 20 μm pitch InSn solder SoP array on a glass substrate was successfully formed using a maskless screen printing process, and two glass substrates were bonded at 130°C.     

无掩膜腐蚀与伺服型电容式微加速度计

为了解决“三明治”这类微器件制作的深窄槽结构成型问题,运用无掩膜湿法腐蚀技术,成型悬臂梁雏形后再成型质量块,较好地实现了悬臂梁与质量块同时准确成型,研制出±70g和±5g两种不同量程的微加速度计。样品测试表明,利用这项技术所制作的微加速度计相对精度皆优于1×10^-4。其中,±70g量程的残差可控制在7mg以内,非线性可达0．02％;±5g量程的残差在0．4mg左右。     

Parallel DNA Synthesis on Poly(ethylene terephthalate)

The fabrication of DNA arrays directly on aminolyzed sheets of poly(ethylene terephthalate) (PET) is described. Array surfaces typically employ bifunctional linkers or layers of covalently attached polymers to provide substrate hydroxy groups as synthesis attachment points. An amine treatment is used here to expose hydroxy groups on films of PET. These hydroxy groups can then be used to couple phosphoramidites and initiate the array synthesis without further functionalization steps. Arrays fabricated on these substrates with a maskless array synthesizer are tolerant of the high number of chemical exposure steps required to synthesize relatively long oligonucleotides. The results might be of the greatest use to the synthetic biology community, for whom a flexible and robust substrate could enable new strategies to enhance the throughput of oligonucleotide synthesis.