Manufacturing Bits: March 31

Shish kebab nano necklaces; direct-write litho; nano-scale lasers.


Shish kebab nano necklaces
Using a directed self-assembly (DSA) process, Georgia Institute of Technology has developed a method to make nanometer-scale, chip-based necklaces.

The technique could enable organic-inorganic structures, which resemble a tiny shish kebab or a centipede. The structures are made with various materials, such as semiconductors, magnetics, ferroelectrics and others.

So far, researchers have made nano-necklaces with up to 55 nanodisks. The nanodisks are about 10nm in diameter and 4nm in thickness. They are about 2nm apart.

Nano-scale worms provide route to nano-necklace structures (Source: Georgia Institute of Technology)

Nano-scale worms provide route to nano-necklace structures (Source: Georgia Institute of Technology)

Researchers have made nano-necklaces from various materials, such as cadmium selenide (CdSe), barium titanate (BaTiO3) and iron oxide (Fe3O4). Future applications include electronics, optoelectronics, sensing and magnetics.

The template-based process grows worm-like diblock copolymers, which are assembled in a chain. In the flow, researchers start with a complex, which consists of alpha-cyclodextrins and cyclic oligosaccharides. The alpha-cyclodextrins are hollow in the center. They thread themselves onto a polyethylene glycol chain via a DSA process. The thread is capped by an agent to retain the tiny structures.

“Our goal was to develop an unconventional, yet robust, strategy for making a large variety of organic-inorganic hybrid shish kebabs,” said Zhiqun Lin, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology, on the university’s Web site. “This is a general technique for making these unusual structures. Now that we have demonstrated it, we believe there is a nearly endless list of materials we can use to craft these nano-necklaces.”

Direct-write litho
Mapper Lithography has officially rolled out the world’s first multi-beam e-beam tool for direct-write lithography applications.

The system, dubbed the FLX-1200, has been in the development stage for at least a decade. Over the years, Mapper has delayed the introduction of the tool, due to an assortment of issues. In multi-beam, the electrons tend to repel each other, making it difficult to control the beams.

Originally, Mapper’s goal was to devise a 13,000 beam system. Now, the goal is to get 1,300 beams up and running by year’s end, which enables a throughput of one wafer an hour.

Over time, though, the FLX-1200 will eventually produce up to two wafers per hour and can be used for sub-90nm technology nodes, down to 14nm. The system is available in 200mm and 300mm configurations.

The industry is interested in Mapper’s tool and for good reason. With direct-write, there is no need for an expensive photomask. This makes the system suitable for higher node designs with low-volume requirements. It can also be used for use in “cutting patterns” in leading-edge designs.

The first FLX-1200 was installed at CEA-Leti in 2014. In December of 2014, the first customer pattern exposures were performed on a 300mm wafer. In CEA-Leti’s “Imagine” program, the FLX-1200 has been tuned to operate in a “mix-and-match” environment.

Nano-scale lasers
The University of Washington and Stanford have developed a nanometer-sized laser using a single atomic sheet.

Researchers are developing so-called nano-laser technology. Nano-lasers are tiny systems that can be modulated at fast speeds. Applications include on-chip optical computing, medical chips and others.

Nano-scale lasers have been developed by embedding quantum dots into a photonic crystal cavity (PCC), but there are several challenges with this approach, according to researchers. There are issues with the random positions and compositional fluctuations of the dots.

Researchers from the University of Washington and Stanford have taken a different approach. Researchers have basically devised monolayer semiconductor nano-cavity lasers with ultralow thresholds.

In the lab, researchers developed a nano-laser, which consists of an atomically thin crystalline semiconductor, based on a tungsten diselenide monolayer technology. This material is the gain medium at the surface of a pre-fabricated PCC. A continuous-wave nano-laser is enabled with an optical pumping threshold as low as 27 nanowatts at 130 kelvin.

“We all want to make devices run faster with less energy consumption, so we need new technologies,” said Xiaodong Xu, UW associate professor of materials science and engineering and of physics, on the university’s Web site. “The real innovation in this new approach of ours, compared to the old nanolasers, is that we’re able to have scalability and more control.”

The semiconductor material stretches across the top of a photonic cavity. (Source: U of Washington)

A semiconductor stretches across the top of a photonic cavity, forming a nano-laser. (Source: U of Washington)

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