Lithography

About: Lithography is a research topic. Over the lifetime, 23507 publications have been published within this topic receiving 348321 citations.

Hydrodynamic Focusing Lithography

Abstract: Anisotropic multifunctional particles hold great promise for drug delivery, imaging, and construction of building blocks for dynamic mesostructures such as self-assembled tissues and 3-D electrical circuits. Of particular interest, multifunctional particles with unique barcodes have been suggested as diagnosis tools for rapid screening of biomolecules. For these applications, particle design is at least as important as size and requires a fabrication technique with precise control over shape and chemical patchiness. Methods currently used to generate multifunctional particles include microcutting, co-jetting, core–shell systems, photo resist-based lithography, and the PRINT method (particle replication in non-wetting templates). The morphology of particles prepared by co-jetting, microcutting, and core–shell systems has been limited to spheres and cylinders. Although multilayer lithography overcomes this limitation, the use of photoresist materials renders this approach suboptimal for many applications. While the PRINT method has its strength in producing small sub-mm particles, to date multiphasic particles beyond a 1-D stripe have not been synthesized. Furthermore, during multifunctional particle synthesis, the technique needs multiple steps and does not provide flexibility as particle shapes are restricted to the pre-defined stamping molds. Previously, we have shown that flow lithography (FL) can be used to generate multifunctional particles—we exploited several microfluidic characteristics such as co-flow of liquid monomers, rapid fluidic exchange, and simple controllability. In FL, we can use a combination of adjacent flowing photocurable monomers with lithographic masks to simultaneously define the shape and chemical pattern of particles. Recently, we also developed lock release lithography (LRL) to extend chemical patterning to multiple dimensions. However, these FL-based approaches for generating particles with patterned chemistries require precise alignment of masks at flow interfaces and concomitant modest particle throughput. Currently, FL cannot be used to synthesize multifunctional particles with chemical anisotropy in the channel height direction (z direction in this article, c.f. Figure 1A). Here, we introduce a new method called hydrodynamic focusing lithography (HFL) that harnesses flow focusing to create stacked flows in two-layered channels for particle synthesis. Contrary to our prior methods to create multilayered particles, here the fluid interface can be perpendicular to the UV light propagation direction and precise mask alignment at the interface is no longer needed. This change in geometry also allows us to polymerize 2-D arrays, compared to 1-D in the prior method, which can increase throughput substantially. In HFL, multiple monomer streams can be simultaneously stacked in both the z and y direction leading to more complex particles than before. Finally, we demonFigure 1. Hydrodynamic focusing lithography (HFL) for high-throughput synthesis of Janus microparticles. A) Microfluidic device used in HFL. P1 and P2 represent the inlet pressures of top and bottom channel respectively. All inlet dimensions are 40 40 mm. Particles are synthesized after layered flows are widened up to 1 mm in a 40 mm tall region of the channel. B) A side view of flow focusing and particle polymerization. C) A fluorescent image of 50 mm triangular particles with green (200 nm, green fluorescent beads) and red (rhodamine A) layers. H1 and H2 are the heights of top (red) and bottom (green) layer in a particle. D) Comparison of measured H2/H1 versus estimated flow ratio Q2/Q1 (see Supporting Information). The dashed line is the prediction from a hydrodynamic model (Eq. (12) in Supporting Information). E) Uniformity of Janus particles synthesized at a, b, c, d, and e spots across a 1 mm width channel. The intervals between spots are 100 mm. Scale bars are 50 mm (C,E) and 20 mm (D).

Directed Self-Assembly of Polystyrene-b-poly(propylene carbonate) on Chemical Patterns via Thermal Annealing for Next Generation Lithography.

Abstract: Directed self-assembly (DSA) of block copolymers (BCPs) combines advantages of conventional photolithography and polymeric materials and shows competence in semiconductors and data storage applications. Driven by the more integrated, much smaller and higher performance of the electronics, however, the industry standard polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) in DSA strategy cannot meet the rapid development of lithography technology because its intrinsic limited Flory–Huggins interaction parameter (χ). Despite hundreds of block copolymers have been developed, these BCPs systems are usually subject to a trade-off between high χ and thermal treatment, resulting in incompatibility with the current nanomanufacturing fab processes. Here we discover that polystyrene-b-poly(propylene carbonate) (PS-b-PPC) is well qualified to fill key positions on DSA strategy for the next-generation lithography. The estimated χ-value for PS-b-PPC is 0.079, that is, two times greater than PS-b-PMMA (χ = 0.029 at ...

Ultrafast deep UV Lithography with excimer lasers

Abstract: The use of high-power pulsed excimer lasers for photolithography is described for the first time. Short exposure times, high resolution and absence of speckle are experimentally demonstrated. Using a XeCl laser at 308 nm and a KrF laser at 248 nm, excellent quality images are obtained by contact printing in two positive photoresists. Resolution down to 1000 line-pairs/mm is demonstrated. These images are comparable to state-of-the-art lithography done with conventional lamps; the major difference is that the excimer laser technique is ∼ 2 orders of magnitude faster. Preliminary results on reciprocity behavior in several resists are also presented.

Using soft lithography to fabricate GaAs/AlGaAs heterostructure field effect transistors

Abstract: This letter describes the fabrication of functional GaAs/AlGaAs field effect transistors using micromolding in capillaries—a representative soft lithographic technique. The fabrication process involved three soft lithographic steps and two registration steps. Room temperature characteristics of these transistors resemble those of field effect transistors fabricated by photolithography. The fabrication of functional microelectronic devices using multilayer soft lithography establishes the compatibility of these techniques with the processing methods used in device fabrication, and opens the door for their development as a technique in this area.

Lift-off lithography using an atomic force microscope

Abstract: We present a technique to fabricate nanostructures with an atomic force microscope (AFM). By taking advantage of the AFM tip sharpness, we engrave a narrow furrow in a soft polyimide layer. The furrow is then transferred using dry etching to a thin germanium layer which forms a suspended mask. Metallic layers are then evaporated through this mask. Metallic lines with a 40 nm linewidth and single‐electron transistors have been fabricated. This lift‐off technique can be used on any substrate and allows easy alignment with previously fabricated structures.