Nanoelectrospray as a direct writing method for electronic circuits

纳米电喷雾作为电子电路的直接写入方法

• 批准号: EP/E03330X/1
• 负责人: John Paul Whitfield Stark
• 金额: $ 19.77万
• 依托单位: Queen Mary University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE03330X%2F1
• 关键词: Nanoelectrospray; direct; writing; method; electronic

In the electronics industry, photolithography is the standard technology used to pattern surfaces with functional materials. However, its use requires special facilities and significant multi-million pound investment due to the costs associated with the large number of process steps. Not all electronic components require the resolution of lithography. There is a growing demand for devices such as flat panel displays which can use lower resolution techniques. As a result, many groups have developed inkjet printer nozzles as a digital writing technology. The functional material is printed directly onto the surface in the liquid phase. This reduces the cost of the patterning and increases alignment accuracy and flexibility in mask design and substrate choice. Previous work in ink jets has deposited photoresist and conductive inks however, the size of the features is a few tens of micrometers. The technique is also limited by the difficulty of clogging and printing accuracy. There is a capability gap between the high resolution at high costs of photolithography and the low cost but low resolution of inkjet printing. This project aims to develop electrospray as a fabrication technology with the benefits of direct writing but with feature sizes and placement accuracy approaching that of photolithography. Electrospray has transformed the analysis of large biomolecules and is routinely used to screen small molecules for pharmaceuticals. It has been used for the production of encapsulated nanoparticles and polymer microfibers for bioscaffold applications. The use of standard electrospray would have to overcome the problem of flow control, as a liquid pump or gaseous pressure is needed to drive the flow. To obtain micrometer features requires very low flowrates, which can not currently be controlled with a sufficiently high accuracy to allow a drop on demand approach. Instead, the deposition head must be swept over the substrate at high speeds otherwise the deposited liquid builds up into large features. Nanoelectrospray is in some ways the simplest form of electrospray, where the flowrate from the nozzle is defined by the voltage applied. One of the benefits is that very low flowrates are easily achieved by selection of the correct nozzle and liquid combination. We have identified a steady state oscillating mode where a jet periodically forms and then relaxes. This pulsating spray occurs at high frequencies and each pulsation ejects a very small and fixed volume of liquid. In this way micrometer-sized dots can be made or, by overlapping these dots, micrometer wide continuous lines can be printed. The deposits are ~ 10 times smaller than the nozzle diameter. By contrast inkjet printed features are often larger than the nozzle diameter. This solves the problems of nozzle clogging experienced with the inkjet process. Proof of concept research sprayed a wide range of liquids and has demonstrated the capability to print droplets with micrometre size and placement accuracy.The proposed research will aim to use nanoelectrospray direct writing to print lines of photoresist and conductive tracks with micrometre widths. The lines of photoresist will be examined using SEM and functionally tested using a silicon etch. Micrometre wide lines of resist is the first aim of this project. The work will also test the feasibility of printing conductive tracks; a range of conductive inks will be assessed. The second principal aim of the project will be to achieve low resistivity conductive tracks with line widths and placement accuracy approaching a micrometre. If effective, the two main outcomes of this project will provide inexpensive alternatives to photolithography with a resolution and multi-layer accuracy much improved over inkjet printing.

在电子工业中，光刻是用于用功能材料图案化表面的标准技术。然而，由于与大量工艺步骤相关的成本，其使用需要特殊的设施和数百万磅投资。并非所有电子元件都需要光刻的分辨率。对于诸如平板显示器之类的可以使用较低分辨率技术的设备的需求不断增长。因此，许多小组已经开发了喷墨打印机喷嘴作为数字书写技术。功能材料以液相直接印刷到表面上。这降低了图案化的成本，并增加了掩模设计和衬底选择中的对准精度和灵活性。先前在喷墨方面的工作已经沉积了光致抗蚀剂和导电油墨，然而，特征的尺寸是几十微米。该技术还受到堵塞困难和打印精度的限制。在光刻的高成本下的高分辨率与喷墨印刷的低成本但低分辨率之间存在能力差距。本计画的目的是发展电喷雾作为一种制造技术，具有直接写入的优点，但其特征尺寸和位置精度接近光刻法。电喷雾已经改变了对大生物分子的分析，并且通常用于筛选药物的小分子。它已被用于生产生物支架应用的封装纳米颗粒和聚合物微纤维。使用标准电喷雾必须克服流量控制的问题，因为需要液体泵或气体压力来驱动流量。为了获得微米特征，需要非常低的流速，其目前不能以足够高的精度控制以允许按需滴入方法。相反，沉积头必须以高速扫过基板，否则沉积的液体积聚成大的特征。纳米电喷雾在某些方面是电喷雾的最简单形式，其中来自喷嘴的流速由所施加的电压限定。其中一个好处是通过选择正确的喷嘴和液体组合可以轻松实现非常低的流量。我们已经确定了一个稳定状态的振荡模式，射流周期性地形成，然后放松。这种脉动喷雾以高频率发生，并且每次脉动喷射非常小且固定体积的液体。以这种方式，可以制造微米尺寸的点，或者通过重叠这些点，可以印刷微米宽的连续线。沉积物比喷嘴直径小~ 10倍。相比之下，喷墨印刷特征通常大于喷嘴直径。这解决了喷墨过程中喷嘴堵塞的问题。概念验证研究喷涂了多种液体，并证明了打印微米尺寸和定位精度的液滴的能力。拟议的研究将旨在使用纳米电喷雾直接写入来打印微米宽度的光刻胶和导电轨道。光致抗蚀剂线将使用SEM检查，并使用硅蚀刻进行功能测试。微米宽的抗蚀剂线条是本项目的首要目标。这项工作还将测试印刷导电轨道的可行性;将评估一系列导电油墨。该项目的第二个主要目标是实现低电阻率导电轨道，其线宽和放置精度接近微米。如果有效，该项目的两个主要成果将提供廉价的替代品，以光刻的分辨率和多层精度大大提高了喷墨打印。