Neon Focussed-Ion-Beam Nanofabrication

我们的愿景是建立一个最先进的三维纳米制造设施，用于开发电子，光子和纳米流体器件，以霓虹灯聚焦离子束（FIB）仪器为基础。它将通过提供特征尺寸小于10纳米的设备的快速原型，改变英国科学和工程界的纳米制造能力。与传统的镓离子FIB相比，采用氖离子作为主要离子，从根本上降低了采样中毒效应。霓虹灯还允许高质量的纳米级硅加工，这是最近引入的氦离子FIB无法实现的。此外，溅射率（最终限制吞吐量）比氦离子高一个数量级，允许在实验室时间尺度内加工大量材料。在过去的二十年中，FIB已经成为研究实验室的主要纳米制造工具。它特别适合于研究环境，因为原型设备可以非常快速地创建，而不需要广泛的工艺开发。然而，商业FIB系统的致命弱点是（直到最近）它们都使用镓离子。一旦这些镓离子（不可避免地）被植入纳米样品中，它们的反应性和高迁移率往往会导致有害的样品中毒效应。例如，功能氧化物中相关电子系统的性质密切依赖于氧的化学计量和顺序；在大多数氧化物中，这些会被镓离子不可逆地扰动。类似地，等离子体纳米孔中的光学损耗也受限于对镓离子研磨介质的损伤。此外，镓注入对纳米电子器件的电学性能也有直接影响。意识到这些局限性，卡尔蔡司在五年前发布了一种新的FIB显微镜，其中Ga源被氦气场离子源（GFIS）取代。与Ga相比，主要的优点是这种离子现在是一种惰性气体，从而一举消除了样品中毒问题。因此，氦GFIS FIB显微镜是成像应用领域的场发射扫描电子显微镜的竞争对手。然而，使用氦的明显缺点是，He离子的溅射率（即入射离子去除材料的速率）通常比Ga离子小30倍。这大大增加了制造时间，使得氦离子不适合许多应用。这自然意味着在GFIS中使用较重的惰性气体，这是卡尔蔡司现在通过其新的霓虹灯GFIS FIB系统实现的机会。（该产品计划于2012年9月发布。）氖离子的溅射产额通常是氦离子的十倍。对于纳米制造应用来说，使用氖代表了快速制造和最小中毒的理想组合。在卡尔蔡司发展实验室的氖-离子纳米制造的演示显示，机械分辨率优于10纳米。这可以与最先进的电子束光刻技术相媲美，电子束光刻技术具有快速成型和三维纳米图案的可能性（因为FIB是一种无电阻技术，允许光束与样品表面以任意角度对齐）的附加优势。

Our vision is to create a state-of-the-art three-dimensional nanofabrication facility for development of electron, photonic and nanofluidic devices, based on the neon focussed-ion-beam (FIB) instrument. It will transform the nanofabrication capabilities of the UK science and engineering community by offering rapid prototyping of devices with feature sizes below 10 nm. By using neon as the primary ion species, sampling poisoning effects will be radically reduced by comparison with conventional gallium-ion FIB. Neon beams also permit high-quality nanoscale machining of silicon, which is not possible with the recently-introduced helium-ion FIB. Furthermore sputtering rates (which ultimate limit throughput) are an order of magnitude higher than with helium ions, allowing significant volumes of material to be machined within laboratory timescales.Over the last twenty years, FIB has become a dominant nanofabrication tool for research labs. It is particularly well suited to the research environment since prototype devices can very quickly be created without the need for extensive process development. The Achilles heel of commercial FIB systems, however, is that (until recently) they all use gallium ions. The reactivity and high mobility of these gallium ions once they have been (unavoidably) implanted into a nanofabricated sample often leads to deleterious sample poisoning effects. For example, the properties of correlated electron systems in functional oxides intimately depend upon the oxygen stoichiometry and order; in most oxides these are irreversibly perturbed by Ga ions. Similarly the optical losses in plasmonic nano-apertures are limited by the damage done to the Ga-ion-milled dielectric. Furthermore, the electrical properties of nanoelectronic devices are also directly affected by Ga implantation. Recognising these limitations, Carl Zeiss released a new FIB microscope five years ago in which the Ga source is replaced by a helium gas field-ion source (GFIS). The main advantage over Ga is that the ion species is now an inert gas, thereby removing the sample poisoning problem at a stroke. The helium GFIS FIB microscope is therefore a rival to the field-emission scanning electron microscope for imaging applications. The obvious disadvantage of using helium, however, is that the sputter yield (i.e. the rate at which material is removed by incident ions) is typically 30 times smaller for He ions than for Ga ions. This greatly increases the fabrication time, rendering He ions unsuitable for many applications.This naturally suggests the use of heavier inert gases in the GFIS, an opportunity which Carl Zeiss are now realising with its new neon GFIS FIB system. (This product is scheduled to be released in September 2012.) The sputter yield for neon ions is typically ten times greater than that for He ions. For nanofabrication applications the use of neon represents an ideal combination of rapid fabrication and minimal poisoning. Demonstrations of neon-ion nanofabrication at Carl Zeiss's development laboratory show machined resolution better than 10 nm. This rivals that obtainable with state of the art electron-beam lithography, with the added advantages of rapid prototyping and the possibility (since FIB is a resist-less technique, allowing the beam to be aligned at an arbitrary angle with respect to the sample surface) of three-dimensional nanopatterning.