聚焦离子束微细加工技术实验研究

一、引言近年来,随着高亮度液态金属离子源的出现,亚微米聚焦离子束技术迅速发展。FIB(聚焦离子束)在半导体和微型特殊器件制作技术中将发挥越来越大的作用。日本日立用B~+FIB无掩模注入Si中,制作出一种新型亚微米沟道长度器件—离子束MOSFET,它在电流增益、漏极击穿电压和短沟道阈值效应等方面都优于传统方法制造的同类器件;在FIB无掩模刻蚀、曝光技术中,已获得30nm的高分辨率的图案;FIB已成功地制成分辨率小于0.25μm的同步辐射光、X射线曝光用的掩模;利用FIB还可修理亚微米的掩模缺陷,目前已有商品FIB掩模修正仪问世;用FIB刻蚀亚微米小孔阵列,可加工超导电子学器件。本文报道在我们设计加工的FIB系统上刻蚀金膜、硅片及自显影FIB曝光的实验结果。本系统已能进行亚微米级微细加工工艺研究。     

聚焦离子束系统在微米/纳米加工技术中的应用

聚焦离子束系统是微细加工和分析的主要技术之一,是一个完美的微米/纳米技术研究平台.简述了聚焦离子束系统的组成和主要功能,着重介绍了近年来该技术在离子束刻蚀、反应离子束刻蚀、离子束辅助沉积、离子注入、微区分析、掺杂和成像以及无掩膜曝光等微米/纳米加工领域的应用,并对未来的发展前景进行了简要分析.     

聚焦离子束技术及其在微纳加工技术中的应用

聚焦离子束（FIB）技术是一种集形貌观测、定位制样、成份分析、薄膜淀积和无掩模刻蚀各过程于一身的新型微纳加工技术。它突破了只能对表层成像和分析的局限，可以对样品进行三维的、表面下的观察和分析，也可以对样品材料进行切割研磨和沉积特定材料，用它可以获得以前无法得到的样品信息。从而为研究人员和制造人员提供了一种对多种样品在纳米尺度进行修改、制作和分析的有效工具。     

离子束刻蚀的束流回路控制

离子束刻蚀是70年代迅速发展起来的一种超精细加工新技术,它是利用离子束轰击固体表面的溅射现象,刻蚀固体表面,利用掩模,可加工出各种精细图形。在缺乏深度终点控制器的情况下,离子束流的稳定度关系到加工深度的精确控制,是离子束刻蚀机的重要指标。影响束流稳定的因素很多,如工作气体流量,阳极电压,真空室温度变化,阴极灯丝的蒸发,离子源栅极引出系统热变形等。因而提高束流稳定度是个重要而困难的问题。我们利用离子束刻蚀工艺制作沟槽栅声表面波器件,为了满足器件对沟槽深度分布的精度要求,需要提高束流稳定度,为此我们采用了束流回路控制方法。这方法是利用束流采样控制     

离子刻蚀的概况

离子刻蚀是利用众所周知的阴极溅射效应对表面进行选择性的剥离加工。由于轰击粒子小和离子刻蚀过程的计量极为精确,因此,用这种方法加工表面,使表面溶解深度在单原子层范围内。离子刻蚀可用来清洗,抛光或进行薄刻蚀,还可配合表面分析法测量密集图形。尤其在微电子技术方面,要求侧表面结构具有越来越高的分辨率,例如最高达0.1μm,这样,配合适当的掩模技术,离子刻蚀就可制获这种表面结构。所以,离子刻蚀在工艺上的重要性与日俱增地显示出来。 离子刻蚀分两种:一种是离子束刻蚀,刻蚀时离子的发生、加速和聚焦均不受靶室影响;另一种是溅射刻蚀,…     

RIBE-5型反应离子束刻蚀机

反应离子束刻蚀技术是近年来发展起来的一种微细加工技术，它利用反应离子束轰击团体表面时发生的溅射效应和化学反应剥离加工工作上的几何图形。具有极高的分辨率，能够控制槽深和槽壁角度，表面应力小。反应离子束刻蚀技术已有效地用于研究和制造大规模和超大规模集成电路，声表面波器件，磁泡存储器，微波器件，集成光路，超导器件，闪烁光栅等。本文叙述了一台ＲＩＢＥ－５型反应离子束刻蚀机的工作原理、结构特点、技术性能和刻蚀工艺实验结果．     

反应离子束刻蚀石英同质掩模制作小阶梯光栅

离子束刻蚀作为真空技术的一种重要应用,已广泛运用于现代微电子器件和微光学器件的制作工艺中。本文结合反应离子束刻蚀与全息光刻技术,针对线密度较低的小阶梯光栅,倾斜刻蚀石英同质掩模,制作了三种在紫外光和可见光波段透射闪耀的小阶梯光栅。第一种光栅线密度为360lp/mm,闪耀角16.8°,在325nm波长的透射衍射效率为74%;第二种和第三种光栅线密度均为400lp/mm,闪耀角为34.7°和43°,其在632.8nm波长的透射衍射效率分别为63%和57%。结果表明,使用CHF_3作为刻蚀气体的反应离子束刻蚀石英同质掩模,所制作的小阶梯光栅在其工作波段透射闪耀的衍射效率为理论值的75%以上,为全息离子束制作低线密度大闪耀角的光栅提供参考。     

石英和BK7玻璃的离子束刻蚀特性研究

石英和BK7玻璃是常用的光学材料和微系统材料.用Ar作为工作气体对石英和BK7玻璃及其掩模材料AZ1350的离子束刻蚀特性进行了研究,分析了离子能量、离子束流密度和离子束入射角等几种因素对刻蚀速率和选择比的影响,结合相关理论得到了相应的刻蚀速率拟合方程.AFM测量结果表明刻蚀工艺对材料的低损伤.由于与光刻胶的刻蚀选择比较低,随着石英和BK7玻璃刻蚀深度的增加,图形转移精度下降.因此提高刻蚀选择比是获得高分辨率图形的前提.     

FIB／SEM双束系统在微纳加工与表征中的应用

简要回顾了聚焦离子束／扫描电子显微镜双束系统在国家纳米科学中心的应用。围绕透射电镜样品制备、扫描电子显微镜与扫描离子显微镜、纳米材料的二维与三维表征等材料表征,以及离子束直接刻蚀加工如光子晶体阵列器件原型加下、材料沉积加工如用于电学性能测试的四电极制作、指定点加工如原子力显微镜针尖修饰、三维加工、电子束曝光及其与聚焦离子束联合加工等纳米结构加工两方面,以一些具体实例分类进行了介绍。针对限制其应用的一些不利因素,如加工效率低、面积小、精度不足、加工损伤等问题,一些新技术如新型离子源Plasma、He^＋／Ne^＋离子等与现有Ga^＋聚焦离子束系统配合将成为未来发展方向。     

离子束刻蚀技术

一、概述离子束刻蚀技术是从70年代起随着固体器件向亚微米级线宽方向发展而兴起的一种超精细加工技术,它是利用离子束轰击固体表面时发生溅射效应来剥离加工器件上所需要的几何图形的。离子束刻蚀这种新工艺与机械加工、化学腐蚀、等离子体腐蚀、等离子体溅射等工艺相比较,具有以下特点:(1)对加工材料具有非选择性,任何材料包括导体、半导体、绝缘体都可以刻蚀;(2)具有超精细的加工能力。它能刻蚀加工非常精细的沟槽图形,是属于微米级和亚微米级加工,甚至能刻出0.008μm 的线条。(3)刻蚀的方向性好,分辨率高.     

Focused ion beam nanofabrication: a comparison with conventional processing techniques

Focused ion beam and dual platform systems are versatile tools for nanoengineering and nanoscience applications. These systems complement conventional processing methods and can be used to prototype and modify a diverse range of nano-devices and sensors. This article discusses FIB nanofabrication and compares it with other fabrication techniques such as electron beam lithography and reactive ion etching. Aspects such as the minimum feature size and side wall profiles are discussed and compared. In addition, the limitations and detrimental effects of FIB processes are discussed.     

Focused ion beam lithography and anodization combined nanopore patterning

In this study, focused ion beam lithography and anodization are combined to create different nanopore patterns. Uniform-, alternating-, and gradient-sized shallow nanopore arrays are first made on high purity aluminum by focused ion beam lithography. These shallow pore arrays are then used as pore initiation sites during anodization by different electrolytes. Depending on the nature of the anodization electrolyte, the nanopore patterns by focused ion beam lithography play different roles in further pore development during anodization. The pore-to-pore distance by focused ion beam lithography should match with that by anodization for guided pore development to be effective. Ordered and heterogeneous nanopore arrays are obtained by the focused ion beam lithography and anodization combined approach.     

Nanostructure fabrication by ultra-high-resolution environmental scanning electron microscopy

Electron beam induced deposition (EBID) is a maskless nanofabrication technique capable of surpassing the resolution limits of resist-based lithography. However, EBID fabrication of functional nanostructures is limited by beam spread in bulk substrates, substrate charging, and delocalized film growth around deposits. Here, we overcome these problems by using environmental scanning electron microscopy (ESEM) to perform EBID and etching while eliminating charging artifacts at the nanoscale. Nanostructure morphology is tailored by slimming of deposits by ESEM imaging in the presence of a gaseous etch precursor and by pre-etching small features into a deposit (using a stationary or a scanned electron beam) prior to a final imaging process. The utility of this process is demonstrated by slimming of nanowires deposited by EBID, by the fabrication of gaps (between 4 and 7 nm wide) in the wires, and by the removal of thin films surrounding such nanowires. ESEM imaging provides a direct view of the slimming process, yielding process resolution that is limited by ESEM image resolution ( approximately 1 nm) and surface roughening occurring during etching.     

Laser-assisted maskless microdeposition of silver nano-particles on a magnesium substrate

Laser-assisted maskless microdeposition and silver nano-particles are used to create micro-scale patterns with nano-scale topography on a magnesium substrate for potential biomedical applications. By controlling the processing parameters, various patterns and properties are achieved. The electron microscopy analysis of a sample prepared by focused ion beam microscope provides evidence for excellent bounding and effective surface alloying across the interface.     

Nanoscale patterning of Zr-Al-Cu-Ni metallic glass thin films deposited by magnetron sputtering

Completely glassy thin films of Zr-Al-Cu-Ni exhibiting a large super-cooled liquid region (deltaTx = 95 K), very smooth surface (Ra = 0.65 nm), and an extremely high value of Vicker's hardness (Hv = 940), as compared to bulk Zr-Al-Cu-Ni metallic glass, were deposited by radiofrequency magnetron sputtering. Nanoscale patterning ability of Zr-Al-Cu-Ni metallic glass thin films was demonstrated by a focused ion beam etching. The capability to write nanometer-scale patterns (line width approximately 12 nm) opens up a variety of possibilities for fabricating nanomolds for imprint lithography, and a wide range of two- or three-dimensional components for future nanoelectromechanical systems.     

Effect of molecular adsorption on the electrical conductance of single au nanowires fabricated by electron-beam lithography and focused ion beam etching

Metal nanowires are one of the potential candidates for nanostructured sensing elements used in future portable devices for chemical detection; however, the optimal methods for fabrication have yet to be fully explored. Two routes to nanowire fabrication, electron-beam lithography (EBL) and focused ion beam (FIB) etching, are studied, and their electrical and chemical sensing properties are compared. Although nanowires fabricated by both techniques exhibit ohmic conductance, I-V characterization indicates that nanowires fabricated by FIB etching exhibit abnormally high resistivity. In addition, the resistivity of nanowires fabricated by FIB etching shows very low sensitivity toward molecular adsorption, while those fabricated by EBL exhibit sensitive resistance change upon exposure to solution-phase adsorbates. The mean grain sizes of nanowires prepared by FIB etching are much smaller than those fabricated by EBL, so their resistance is dominated by grain-boundary scattering. As a result, these nanowires are much less sensitive to molecular adsorption, which mediates nanowire conduction through surface scattering. The much reduced mean grain sizes of these nanowires correlate with Ga ion damage caused during the ion milling process. Thus, even though the nanowires prepared by FIB etching can be smaller than their EBL counterparts, their reduced sensitivity to adsorption suggests that nanowires produced by EBL are preferred for chemical and biochemical sensing applications.     

The fabrication of metal silicide nanodot arrays using localized ion implantation

We propose a process for fabricating nanodot arrays with a pitch size of less than 25?nm. The process consists of localized ion implantation in a metal thin film on a Si wafer using a focused ion beam (FIB), followed by chemical etching. This process utilizes the etching resistivity changes of the ion beam irradiated region that result from metal silicide formation by ion implantation. To control the nanodot diameter, a threshold ion dose model is proposed using the Gaussian distribution of the ion beam intensities. The process is verified by fabricating nanodots with various diameters. The mechanism of etching resistivity is investigated via x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).     

Nanofabrication of polymer surfaces utilizing colloidal lithography and ion etching

In this paper, we utilize colloidal lithography based on electrostatic self-assembly of polystyrene colloidal particles onto a polymer surface as a nanoscale mask. The pattern is then transferred to the surface by ion beam etching. Each particle acts as an individual mask, resulting in an array of identical structure. Ion beam exposure etches away the unmasked surface between the particles, so the particle mask pattern can be transferred into the polymer surface. This method allows to nanofabricate bulk polymeric surfaces with systematic variation in relief, structure sizes, and aspect ratios. It is a fast, simple, and reliable method to fabricated different polymeric surfaces even on large area samples (>1 cm/sup 2/). The structural variation is achieved by use of different conditions during the self-assembly of the mask (e.g., different particles sizes) or different ion etching conditions during the pattern transfer (e.g., ion energy, ion flux, ion incident angle, etching time, gas environment).     

EBL- and AFM-based techniques for nanowires fabrication on Si/SiGe

Two approaches for sub-100 nm patterning are applied to Si/SiGe samples.The first one combines electron beam lithography (EBL) and anisotropic wet etching to fabricate wires with triangular section whose top width is narrower than the beam size. Widths as small as 20 nm on silicon and 60 nm on Si/SiGe heterostructures are obtained.The second lithographic approach is based on the local anodization of an aluminum film induced by an atomic force scanning probe. Using atomic force microscopy (AFM) anodization and selective wet etching, aluminum and aluminum oxide nanostructures are obtained and used as masks for reactive ion etching (RIE). Sub-100 nm wide wires are fabricated on Si/SiGe substrates.