Manufacturing Bits: Feb. 18

Molecular layer etch
The U.S. Department of Energy’s Argonne National Laboratory has made new advances in the field of molecular layer etching or etch (MLE).

MLE is related to atomic layer etch (ALE). Used in the semiconductor industry, ALE selectively removes targeted materials at the atomic scale without damaging other parts of the structure.

ALE is related to atomic layer deposition (ALD). In ALD, a system deposits a material one layer at a time. Both ALD and ALE deal with inorganic films, according to Argonne National Laboratory. In contrast, MLE can be used to remove organic films as well, according to researchers.

Let’s say you want to remove layers of film on a wafer. In an MLE system, pulses of gas are injected inside a vacuum chamber. The chamber consists of wafers.

The first gas (gas A) reacts to the surface of the film on the wafer. A second gas (gas B) is pumped into the system. This process is repeated until the desired thickness is removed from the film, according to Argonne National Laboratory.

Source: Argonne National Lab

In the lab, Argonne National Laboratory tested MLE using alucone. Alucone, an organic material similar to silicone rubber, could be used in flexible electronics.

First, a lithium-containing salt compound was injected in an MLE system. Then, a trimethyl aluminum (TMA) compound was injected. TMA is an organometallic aluminum compound.

“The etching process results in the removal of 0.4nm/cycle of alucone at 160°C and up to 3.6nm/cycle of alucone at 266°C in ex situ etching experiments on silicon wafers,” according to researchers in Chemistry of Materials, a technology journal. “This halogen-free etching process enables etching of MLD films and provides new fabrication pathways for the control of material geometries at the nanoscale.”

Matthias Young, an assistant professor at the University of Missouri and former postdoctoral researcher at Argonne, said: “Our ability to control matter at the nanoscale is limited by the kinds of tools we have to add or remove thin layers of material. Molecular layer etching is a tool to allow manufacturers and researchers to precisely control the way thin materials, at microscopic and nanoscales, are removed.”

“MLE has the potential to help usher in new pathways for fabricating and controlling material geometries at the nanoscale, which could open new doors in microelectronics and extend beyond traditional Moore’s Law scaling,” said Argonne chemist Jeff Elam.

ALD conformality
Atomic Limits, a blog site that focuses on ALD and ALE, has posted a new paper that provides insights on the conformality of thin films grown by ALD.

The paper looks at film conformality during the ALD process in relation to fundamental parameters, such as the reaction probabilities. It also describes an analytical model, which provides insights of the growth process in terms of these parameters.

“One of the most important messages here is that the loss of reactant molecules through surface adsorption and surface recombination may seem similar, but results in very different growth behavior,” according to Karsten Arts, Erwin Kessels and H.C.M Knoops in the blog. “This is explained in the three following sections. First, the general approach for modeling ALD conformality, in terms of sticking probabilities and recombination probabilities, is described. Then, we show how the sticking probability determines the growth regime during thermally-driven ALD. Finally, we demonstrate how the recombination probability can limit film conformality during plasma ALD, where we note that plasma ALD can yield very conformal films as well.”

This blog is an initiative of members of the Plasma & Materials Processing group at Eindhoven University of Technology.

IRPS
The 2020 IEEE International Reliability Physics Symposium (IRPS), a technical conference that focuses on the latest research in microelectronics reliability, will be held in Dallas, Texas from March 29 to April 2.

IRPS involves a multitude of topics. It will also feature a number of special focus sessions highlighting novel and emerging areas of electronic reliability, as well as topics relating to conventional semiconductors, integrated circuits, and microelectronic assembly reliability.

The focus sessions involve the following topics: silicon carbide device reliability; neuromorphic computing reliability; IC reliability and aging; and reliability in RF/mmW/5G.

“The Symposium program is expanding beyond the traditional areas of CMOS device, circuit, and systems reliability to include emerging microelectronics reliability topics, including circuit reliability & aging, wide bandgap semiconductors, neuromorphic computing reliability, and RF/mmW/5G device reliability, reflecting major trends in the industry,” said Charles Slayman, IRPS 2020 technical program chair. “In addition, this year IRPS is privileged to have five keynote speakers for the plenary sessions from both industry and academia.”