Manufacturing Bits: Aug. 15

Self-collapse lithography; molecular chips; select dep blog.


Self-collapse lithography
The University of California at Los Angeles (UCLA) has developed a technology called self-collapse lithography.

The technology, reported in the journal Nano Letters, resembles the combination of nanoimprint, selective removal and a chemical lift-off process. More specifically, though, the technology provides insights into patterning using a chemical lift-off lithography technique.

In the flow, researchers first devised a substrate. The substrate is patterned with conventional lithography techniques at feature sizes blow 30nm, according to UCLA. Then, a chemical composition is applied on the substrate. The chemical composition self assembles into a pattern formed by the original lithographic technique. This is called a self-assembled monolayer (SAM) process.

Following those events, an elastomeric stamp is applied to the SAM layer. The stamp is based on a polydimethylsiloxane (PDMS) material.
The roof of the stamp collapses on the surface, according to UCLA. Then, the stamp is raised, which, in turn, selectively removes various SAM molecules on the surface. This is sometimes called a chemical lift-off process.

With the technology, researchers devised patterns from ∼2μm to sub-30nm, according to UCLA. This is done by decreasing the stamp relief heights from 1μm to 50nm, according to researchers

Molecular chips
Columbia University has made a breakthrough in the field of molecular electronics.

Using a scanning tunneling microscope (STM) technique, researchers have deposited and formed a single cluster of geometrically ordered atoms. The cluster is made up of 14 atoms, which has a diameter of about 0.5nm.

Then, they wired the core atoms to two gold electrodes. This enabled researchers to characterize its electrical response by applying a voltage on the structure.

Columbia researchers wired a single molecular cluster to gold electrodes. (Photo courtesy of Bonnie Choi/Columbia University)

This, in turn, enabled researchers to demonstrate the so-called “current blockade effect.” This is the ability to switch a device from the insulating to the conducting state. “We found that these clusters can perform very well as room-temperature nanoscale diodes whose electrical response we can tailor by changing their chemical composition,” said Latha Venkataraman, a professor of applied physics and chemistry at Columbia. “Theoretically, a single atom is the smallest limit, but single-atom devices cannot be fabricated and stabilized at room temperature. With these molecular clusters, we have complete control over their structure with atomic precision and can change the elemental composition and structure in a controllable manner to elicit certain electrical response.”

Giacomo Lovat, a postdoctoral researcher, added: “Most of the other studies created single-molecule devices that functioned as single-electron transistors at four degrees Kelvin, but for any real-world application, these devices need to work at room temperature. And ours do. We’ve built a molecular-scale transistor with multiple states and functionalities, in which we have control over the precise amount of charge that flows through. It’s fascinating to see that simple chemical changes within a molecule, can have a profound influence on the electronic structure of molecules, leading to different electrical properties.”

Select dep blog
A group has launched a new blog that provides the latest research into the world of atomic-level processing for IC manufacturing.

The site, called Atomic Limits, provides the latest on selective deposition, atomic layer etch (ALE) and other subjects. In one of its latest postings, the site reported the latest finding from the recent 2nd Area Selective Deposition workshop (ASD2017).