Fabrication of Silicon Nanowire Arrays with Controlled Diameter, Length, and Density

We report on an InGaN-based light-emitting diode (LED) with a top p-GaN surface microroughened using the metal clusters as a wet etching mask The light-output power for a LED chip with microroughening was increased compared to that for a LED chip without one This indicates that the scattering of photons emitted in the active layer was much enhanced at the microroughened top p-GaN surface of a LED due to the angular randomization of photons inside the LED structure, resulting in an increase in the probability of escaping from the LED structure By employing the top surface microroughened in a LED structure, the power conversion efficiency was increased by 62%

Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface

DRAM cell arrays having a cell area of about 4F 2 comprise an array of vertical transistors with buried bit lines and vertical double gate electrodes. The buried bit lines comprise a silicide material and are provided below a surface of the substrate. The word lines are optionally formed of a silicide material and form the gate electrode of the vertical transistors. The vertical transistor may comprise sequentially formed doped polysilicon layers or doped epitaxial layers. At least one of the buried bit lines is orthogonal to at least one of the vertical gate electrodes of the vertical transistors.

DRAM layout with vertical FETs and method of formation

The deposition of ionized beams of size-selected atomic clusters onto well-defined substrates represents a new method of preparing nanostructured surfaces, with lateral feature sizes in the range 1–10 nm. 'Pinning' of the incident clusters prevents the diffusion of the clusters on the surface, and thus preserves the gas-phase cluster size, even at room temperature and above. At the same time, advances in diblock copolymer techniques allow the preparation of ordered two-dimensional arrays of clusters. Here we discuss the creation and applications of these nanostructured surfaces, ranging from the fabrication of semiconductor nanostructures to the immobilization of protein molecules.

Nanostructured surfaces from size-selected clusters.

Substrate topography plays a vital role in cell and tissue structure and function in situ, where nanometric features, for example, the detail on single collagen fibrils, influence cell behaviour and resultant tissue formation. In vitro investigations demonstrate that nanotopography can be used to control cell reactions to a material surface, indicating its potential application in tissue engineering and implant fabrication. Developments in the catalyst, optical, medical and electronics industries have resulted in the production of nanopatterned surfaces using a variety of methods. The general protocols for nanomanufacturing require high resolution and low cost for fabricating devices. With respect to biological investigations, nanotopographies should occur across a large surface area (ensuring repeatability of experiments and patterning of implant surfaces), be reproducible (allowing for consistency in experiments), and preferably, accessible (limiting the requirement for specialist equipment). Colloidal lithography techniques fit these criteria, where nanoparticles can be utilized in combination with a functionalized substrate to produce in-plane nanotopographies. Subsequent lithographic processing of colloidal substrates utilizing, for example, reactive ion etching allows the production of modified colloidal-derived nanotopographies. In addition to two-dimensional in-plane nanofabrication, functionalized structures can be dip coated in colloidal sols, imparting nanotopographical cues to cells within a three-dimensional environment.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2006.0149

Colloidal lithography and current fabrication techniques producing in-plane nanotopography for biological applications

We have developed a simple fabrication process which allows the production of nanoscale silicon structures. Rough silver films are used as an etching mask for reactive ion etching at 10 °C. Variation of the etching parameters, such as the rf power, allows control over the shape of the features; the production of both pillars and cones is possible. The density and diameter of these features are controlled by the etching time. Pillars with diameters as small as 5 nm are reported.

/pdf/fabrication-of-silicon-cones-and-pillars-using-rough-metal-angszdiwmu.pdf

Fabrication of silicon cones and pillars using rough metal films as plasma etching masks

We have investigated the deposition of size-selected metal clusters (Ag400) onto a stepped graphite surface. The clusters were produced with an inert gas condensation cluster source and were imaged on the surface with a high-resolution scanning electron microscope. For modest cluster deposition energies, cluster aggregation is much more limited at the steps than on the flat terrace regions of the surface, suggesting the possibility of the fabrication of structured arrays (e.g., chains) of size-selected particles. A theoretical analysis of the particle-particle gap size distribution along the step probes the 1D mobility of the particles trapped at the step.

Trapping of size-selected Ag clusters at surface steps

We report the fabrication of ordered arrays of silicon nanopillars via reactive ion etching (RIE). Self-assembled polymer spheres are used as masks for the deposition of hexagonal arrays of Ag islands on a silicon substrate. Following the removal of the polymer spheres, the sample is etched with SF6 and CF4 at 100 W leading to hexagonal arrays of silicon nanopillars. The aspect ratio of the pillars can be influenced by the etching time; maximum aspect ratios of 15:1 have been produced.

https://iopscience.iop.org/article/10.1088/0022-3727/32/24/102/pdf

Fabrication of ordered arrays of silicon nanopillars

The formation of 10 nm scale Si pillars using deposited metal clusters of various kinds (Au, Ag etc) as nuclei for the creation of etch masks has been investigated via microwave plasma etching at about . Experiments using size-selected Ag clusters indicate that the cluster size affects the efficiency of pillar formation but has little effect on the diameter of the fabricated pillars. The average diameter of pillars fabricated with Au clusters is 9 nm, while that with Ag clusters is 19 nm. This is attributed to the difference in chemical reactivity of the clusters with S or F, the components of the etching gas, which results in a different ability to form etch masks by condensation of species.

https://iopscience.iop.org/article/10.1088/0022-3727/31/7/001/pdf

Formation of 10 nm Si structures using size-selected metal clusters

We have studied the formation of Cu clusters from Cu atoms deposited onto a Si (111) surface patterned with (2–5 μm width) lines of photoresist. In addition to a thin Cu layer on the exposed Si surface, large (∼150 nm) clusters nucleate at the boundary between the Si and the resist strips, which remain after removal of the resist by dissolution. The results show how it is possible, using the resist to collect deposited atoms, to assemble nanoscale cluster structures with a precision (∼150 nm feature size) which is much better than the resolution of conventional optical lithography (∼μm linewidth).

Katrin Seeger

Papers

Fabrication of silicon cones and pillars using rough metal films as plasma etching masks

Trapping of size-selected Ag clusters at surface steps

Fabrication of ordered arrays of silicon nanopillars

Formation of 10 nm Si structures using size-selected metal clusters

Microfabrication of nanoscale cluster chains on a patterned Si surface