Maskless lithography

D Optofluidic Maskless Lithography Using Soft Membrane Deformation... 

Lee SA, Chung SE, Park W, Lee SH, Kwon S (2009) Three-dimensional fabrication of heterogeneous microstructures using soft membrane deformation and optofluidic maskless lithography. Lab Chip 9 1670-1675... 

This increase in storage capacity has been accomplished by lowering LW j from 0.8 jtm to 0.04 jtm. Additional approaches to enhance resolution, such as zone-plate array lithography [250], or the use of phase-shifting masks and maskless lithography [251] cannot be treated here. 

One application of lasers to lithography is a maskless patterning technology. In this application, the spatial coherence of the laser is the essential property ... 

The two principal modes of operation of electron-beam exposure systems include the maskless direct-write electron-beam machines and the mask-based electron-beam machines. Direct-write electron-beam machines operate directly from design data and are capable of extremely high resolution. Mask-based electron-beam systems utilize masks in their imaging process. The implementation of electron-beam lithography in mix-and-match mode with optical lithography in a manufacturing environment has been demonstrated. 

Kurihara, A focused ion beam system for submicron lithography, J. Vac. Set Technol. B 3, 41 (1985) E. Miyauchi, H. Hashimoto, and T. Utsumi, Lateral spreads of Be and Si in GaAs implanted with a maskless ion implantation system, Jpn. J. Appl. Phys. 22, L225 (1983) K. Gamo, T. Matsui, and S. Namba, Characteristics of Be Si Au ternary alloy liquid metal ion sources, Jpn. J. Appl. Phys. 22, L692 (1983). 

The principle of maskless ion projection lithography is illustrated in Fig. 15.10. A hroad ion beam is used to illuminate a programmable aperture plate with thousands of apertures of micrometer-scale dimensions, generating up to 4000 beams. In the vicinity of the apertures are tiny deflection plates, each of which can be individually controlled with the aid of integrated CMOS electronics. The slightly deflected beams are blocked at the stopping plate, and the nondeflected... 

Figure 15.10 Schematic of a maskless ion projection lithography system developed at IMS, Vienna, Austria. (Courtesy of G. Gross.)...

Figure 15.11 Resolution SEM images of features ranging in size from 22-nm half-pitch (hp) to 90 nm (1 1.5 pitch), printed with maskless ion projection lithography system on 20-nm hydrosilesquixane resist, using 10-keV argon ions at an exposure dose of...

Figure 15.12 SEM image of directly patterned 70-nm Cr on quartz mask blanks with maskless ion projection lithography system, using 10-keV argon ions at a sputtering dose of 39 xC/cm. ...

Figure 15.13 SEM image of directly patterned cone structures (formed by redeposition processes at the lens edges following prolonged sputtering GaAs substrate) with maskless Ion projection lithography system, using 250,000 parallel 10-keV argon...

Groves, T. R., Pickard, D., Rafferty, B., Crosland, N., Adam, D., and G. Schubert. 2002. Maskless electron lithography Prospects, progress, and challenges. Microelectronic Engineering 61-62 285-293. 

Imprinting lithography is another maskless technique capable of generating sub-100 nm patterns. It is essentially a nanomolding process, in which a transparent patterned template is pressed into a low-viscosity monomer layer dispensed onto the surface of a wafer. Thereby, the relief structure of the template is fiUed. After photopolymerization of the monomer with the aid of UV light (see Chapter 10), the template is separated, leaving a solid polymer replica of the template on the surface of the wafer. With the aid of subsequent etching processes, the pattern is fixed on the wafer s surface [4]. 

Such confined etchant layer technique has been applied to achieve effective three-dimensional (3D) micromachining on n-GaAs and p-Si. It operates via an indirect electrochemical process and is a maskless, low-cost technique for microfabrication of arbitrary 3D structures in a single step [109]. It has also been presented that free-standing Si quantum wire arrays can be fabricated without the use of epitaxial deposition or lithography... 

Micro stereo lithography is a rapid prototyping method to generate 3D molds. It is a maskless process with layer-by-layer fabrication of microstructures via the projection of sliced images of 3D objects, as shown in Fig. 9. 

Chemically amplified resists are quite effective in improving pattern sizes in photofabrication. However, optical limitations in resolution must be overcome to improve further progress. Several processes contribute to improving the resolution of photofabrication. In this chapter, immersion, double-patterning, multipatterning maskless, multielectron beam, and direct self-assembly lithography processes are introduced. 

Micro stereo lithography is a rapid prototyping method to generate 3D molds. It is a maskless process with layer-by-layer fabrication of microstructures via the projection of sliced images of 3D objects, as shown in Fig. 9. A laser beam directs to the photocurable resin which can be classified as an epoxy, vinylether, or acrylate. The 3D structure or mold is built on a platform which can be controlled by an XYZ positioner. When one layer is complete, the plat-... 

Ranunohan, A., et al., 2011. One-step maskless grayscale lithography for the fabrication of 3-dimensional structures in SU-8. Sens. Actuators B 153,125-134. 

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