On-line surface inspection of roll-to-roll film processing

纳米尺度和超精密结构表面的使用迅速增加，广泛应用于许多应用范围，包括光伏薄膜，光学，硅片，硬盘，MEMS/NEMS，微流体和微成型行业。这些行业都非常依赖超精密表面。然而，这种表面的制造有一个基本的限制因素，即在制造环境中快速测量产品的能力。据报道，目前制造的质量在很大程度上取决于过程工程师的经验，这些经验是由昂贵的试错方法支持的。因此，许多这些制造项目遭受高废品率高达50-70%。在那些生产大量大面积箔产品的行业，如纸张和包装产品，以及新兴市场部门，如柔性电子产品，制造过程通常涉及在大面积基板和箔上沉积和绘制多层薄膜。对于这些类型的产品，产品性能和功能的提高可以来自层数的增加，或者单个层的厚度或图案特征的大小从微观到纳米尺度的减少。为了在涂层和图案加工过程中获得高产量，薄膜必须均匀且在箔的大部分区域上基本完美。然而，随着多层膜中界面数量的增加，缺陷形成的风险增加，并且随着层厚度缩小到纳米级，这些缺陷的大小和性质也会发生变化。镀层缺陷可能由以下因素引起：箔表面异常（例如划痕和表面刺状或孔），环境颗粒或仅几个原子厚的化学污渍形式的污染，以及不正确的工艺条件（例如颗粒产生或反应副产物的积累）。图案缺陷是由不正确的图案转移引起的，例如划痕或成型错误。为了确保高产品成品率，关键的挑战是在生产速度下以足够的分辨率检查箔表面，以检测i)开始箔表面存在的问题缺陷和ii)在涂层和图案加工过程中出现的缺陷。由于这些过程的性质，检测方法必须与薄膜表面不接触。有效的检测是进一步处理的关键，如应用局部修复技术从薄膜表面去除缺陷。目前尚无有效的检测方法可用于上述应用。本项目试图通过研究一种基于白光光谱干涉测量和使用通用图形处理单元（GPGPU）并行信号处理的高速在线表面轮廓光学测量技术来解决我们目前用于表面检测的技术的缺点。这些技术结合起来有可能应用于高精度表面的实时在线测量，例如由卷对卷薄膜加工、光刻蚀刻加工、掺杂、CVD/PVD涂层、研磨和生产线上的CMP加工产生的表面。该系统是大批量生产高质量、高效率光伏薄膜和其他卷对卷薄膜的关键。这种产品的成功将帮助我们更有效地将太阳能转化为电能，而且成本更低。

The rapidly increasing use of nano scale and ultra-precision structured surfaces is widely spread in many applications ranges and covers photovoltaic thin film, optics, Si wafers, hard disks, MEMS/NEMS, micro fluidics and the micro moulding industries. These industries all critically rely on ultra precision surfaces. There is however a fundamental limiting factor to the manufacture of such surfaces, namely the ability to measure the product rapidly in the manufacturing environment. It has been reported that currently the quality of fabrication depends largely on the experience of process engineers backed up by an expensive trial-and-error approach. Consequently many of these manufactured items suffer from high scrap rates as high as 50-70%. In the industries those making high volume large area foil products such as paper and packaging products and emerging market sectors such as flexible electronics, the manufacturing processes often involve the deposition and patterning of multi-layer thin films on large area substrates and foils. For these types of product, increased product performance and functionality can come from an increase in the number of layers, or a decrease from micro- to nano-scale in the thickness of individual layers or size of pattern features. To achieve high yield in the coating and patterning processes the films must be uniform and largely perfect over most of the area of the foil. However there is an increased risk of defects forming as the number of interfaces increases in the multi-layer films, and the size and nature of those defects changes as the layer thicknesses shrink to the nano-scale. Coating defects can be caused by surface anomalies on the foil (e.g. scratches and surface spikes or holes), by contamination in the form of ambient particles or chemical stains only a few atoms thick, and by incorrect process conditions (e.g. particle generation or build-up of reaction by-products). Patterning defects arise from incorrect pattern transfer, e.g. scribing or moulding faults. In order to ensure high product yield the key challenge is to inspect the foil surface at production speed with sufficient resolution to detect i) the presence of problem defects on the starting foil surface and ii) defects as they appear during the coating and patterning processes. Due to the nature of these processes the inspection methods have to be in noncontact with the film surfaces. Effective inspection is the key for further process such as applying local repair techniques to remove the defects from the film surface. Currently there is no effective inspection methods that can be applied for the above applications. This project attempts to address shortcomings of the techniques that we currently employed for surfae inspections by investigating a high speed on-line surface profile optical measurement technique based on white light spectral interferometry and parallel signal processing using general purpose graphic processing unit (GPGPU). These techniques combined have the potential to be applied to real-time on-line measurement of high precision surfaces such as those resulting from roll-to-roll film processing, lithographic etching processing, doping, CVD/PVD coatings, lapping, and CMP processing on the production line. The proposed system is a key for mass production of high quality, high efficiency photovoltaic thin film and other roll-to-roll film productions. The success of this product will help us to convert solar power to electricity more efficiently and cost effectively.