Lithography potentials of UV-nanoimprint

In the past decade nanoimprint has been developed to a serious alternative for next generation lithography (NGL). In this work, the most recent developments of UV-nanoimprint Lithography (UV-NIL) with special emphasis to the work accomplished at AMO and the IHT-RWTH Aachen are reviewed and functional applications demonstrated. Further the potentials of various UV-NIL concepts are evaluated and possible interests in certain application areas are discussed.     

纳米压印光刻技术--下一代批量生产的光刻技术

纳米压印光刻技术已被证实是纳米尺寸大面积结构复制的最有前途的下一代技术之一。这种速度快、成本低的方法成为生物化学、μ级流化学、μ-TAS和通信器件制造以及纳米尺寸范围内广泛应用的一种日渐重要的方法,如生物医学、纳米流体学、纳米光学应用、数据存储等领域。由于标准光刻系统的波长限制、巨大的开发工作量、以及高昂的工艺和设备成本,纳米压印光刻技术可能成为主流IC产业中一种真正富有竞争性方法。对细小到亚10nm范围内的极小复制结构,纳米压印技术没有物理极限。从几种纳米压印光刻技术中选择两种前景广阔的方法——热压印光刻(HEL)和紫外压印光刻(UV-NIL)技术给予介绍。两种技术对各种各样的材料以及全部作图的衬底大批量生产提供了快速印制。重点介绍了HEL和UV-NIL两种技术的结果。全片压印尺寸达200mm直径,图形分辨力高,拓展到纳米尺寸范围。     

Imprinted polymer stamps for UV-NIL

Thermal step and stamp nanoimprint lithography (SSIL) offers an alternative to fabricate transparent polymer stamps for UV-imprinting. The fabrication process does not require any other subsequent steps, e.g. dry etching or anti adhesive coating.In this work, we have manufactured UV-stamp by combining patterns of two different silicon masters. The patterns of the silicon masters were transferred into resin coated quartz plate by sequential imprinting. The first master consisted gratings with 50 nm features and the second master consisted dot arrays of 350 nm diameter features. The novel idea is the ability to create a large UV-stamp using a combination of small masters. Thus fabricated UV-stamps were used for demonstrating step and repeat UV-imprinting. The quality of the UV-stamps and imprints were analyzed by AFM. High fidelity patterns were achieved in respect to patterns in the original silicon master.     

Soft UV-nanoimprint lithography on non-planar surfaces

We report on a simple and effective process that allows direct UV-imprinting of micro- and nanostructures on non-planar surfaces, even at sharp edges such as step surfaces. The key for the process is the use of a thin flexible polymer stamp, which was fabricated by spin-coating poly(dimethylsiloxane) (PDMS) on a pre-patterned Si or poly(methyl methacrylate) (PMMA) master and releasing the thin PDMS layer after curing. The thin PDMS stamp was used to conformally mold a UV resist layer coated on various non-planar substrates with different radii of curvature. With this method, we have successfully demonstrated micro- and nanopatterns down to 63 nm on curved surfaces as well as sharp step-like structures. The process so developed will improve the versatility and applicability of molding technologies in many applications that require patterning non-planar substrates, considering that most molding technologies allow for patterning only on planar substrates or surfaces with large curvature radii.     

UV-curable nanoimprint resin with enhanced anti-sticking property

This paper reports on a newly developed anti-sticking resin obtained by mixing a fluorine-containing monomer (F-monomer) for UV nanoimprinting lithography (UV-NIL) to reduce the contact adhesion force during the demolding process. The new resin system shows an enhanced reliability and resolution of pattern transfer with no treatment on the surface of the quartz stamp. We fabricated various nanopatterns with F-monomer resins of various concentrations in the low pressure UV-NIL. The number of process steps of a release layer treatment for UV-NIL was reduced by using F-monomer with anti-sticking property.     

硅油稀释PDMS法制备紫外纳米压印软模板

软模板的制作是紫外纳米压印中关键的技术,模版的分辨率直接决定了压印图形的最小分辨率。使用具有高度均匀、100nm级孔洞阵列结构的多孔氧化铝作为母版,使用基于液态浇铸的硅油稀释聚二甲基硅氧烷(硅油和聚二甲基硅氧烷的质量比为1:2)法制备出具有规则点阵结构的软模板。通过SEM和AFM表征发现,特征图形得到了有效转移,特征尺度保持在100nm左右。相对于传统的模板制备方法,此方法成本低、流程简单、适合大规模生产,是一种非常有前途的软模板制备方法。     

Design and validation of a novel master-making process chain for organic and large area electronics on flexible substrates

This paper presents a novel process chain for fabrication of replication masters for serial manufacture. The proposed process chain is validated for serial fabrication of (large area) organic electronic devices on flexible substrates. The advantages and limitations of the component technologies in the proposed manufacturing route are discussed and their interdependencies in a process chain for producing both 2.5D and 3D nano- and micro-structures are analysed. The proposed master-making route relies on using different technologies for micro-structuring and sub-micron and nano patterning that are applied to the fabrication of Ni shims incorporating different length scale features. In particular, the capabilities of photolithography as a micro-structuring technology were combined with those of FIB machining to add sub-micron and nano-features on micro patterned fused silica templates. Then, by applying UV nanoimprint lithography such templates were validated and their nano and micro-structures were consistently replicated in one step. Finally, the feature transfer of such imprints onto Ni shims was also successfully accomplished with only minor deviations from the target dimensions.     

新型高抗粘紫外纳米压印光刻胶的工艺研究

为了减少紫外纳米压印技术脱模过程中的接触粘附力,开发了一种新型高流动、抗粘的紫外纳米压印光刻胶。光刻胶以BMA为聚合单体,添加特定配比的交联剂和光引发剂配置而成。紫外纳米压印实验在本课题组自主研发的IL-NP04型纳米压印机上完成。实验得到光刻胶掩膜膜厚为1.21μm,结构尺寸深246nm,周期937.5nm。实验结果表明,在没有对石英模板表面进行修饰的情况下,该光刻胶依然表现出高可靠性和高图形转移分辨率,有效减少了紫外纳米压印工艺中的模板抗粘修饰的工艺步骤。     

Applications of UV-nanoimprint soft stamps in fabrication of single-frequency diode lasers

We show how to use a modified poly-dimethyl-siloxane (PDMS) soft stamp to reduce pattern deformation and residual layer thickness in soft UV-nanoimprint lithography. A soft stamp thinned with toluene reduces the residual layer of a resist by as much as 50% compared to an unthinned stamp. We apply the soft UV-nanoimprint to prepare nanopatterned waveguides for a single-frequency diode laser. This laser operates with a side-mode suppression ratio of 50 dB, which indicates that the patterns are precise and uniform over the whole imprint field. To the best of our knowledge, this is the first single-frequency laser fabricated by soft UV-nanoimprint technology.     

Press and release imprint: Control of the flexible mold deformation and the local variation of residual layer thickness in soft UV-NIL

We report on a two step soft UV nanoimprint process termed “Press and Release Imprint (PRI) that enables the reduction of both the mold deformation and the local variation of the residual layer thickness, thereby allowing high fidelity pattern replication with a uniform local residual layer thickness. The effect of imprint pressure on the mold deformation, local variation of residual layer thickness as well as required mold release time has been investigated for microscale patterns in the range of 10-100 μm. The potentials of PRI are demonstrated by high fidelity replication of micro-patterns with a uniform residual layer of minimum thickness.