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Universités et écoles d'ingénieurs

Published on 22 October 2018

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Stanford University

‘Leti Is the Best Choice’ for Visiting Researchers 

Stanford University Prof. Yoshio Nishi came to Grenoble to head the Chair of Excellence Project funded by the Grenoble Nanosciences Foundation, and to work on the OxRAM project with Leti and IMEP-LaHC. The four-year project focused on developing a new memory technology: oxide-based resistive memories, in particular HfO2-based. 

Among its achievements, the team studied the impact of alloying/doping HfO2 with other materials for improved RRAM performances. Using ab-initio calculations, they pointed out that incorporating aluminium in HfO2 results in better thermal stability of devices, due to shorter bond lengths associated with their higher atomic concentration. This has been confirmed by experiments. 

Prof. Nishi, a professor of electrical engineering, spent several months in Leti’s memory lab, and co-tutored a PhD student and a post-doc. The team also published eight papers.

His relationship with Leti began about 30 years ago, when he was director of R&D at Toshiba and he met Leti scientists at conferences.

“I have known Leti for a very long time,” he said. “The culture is very welcoming and there is a very strong work ethic. When I left the office at 7:30 p.m., oftentimes people were still working, which is very different than in the U.S. and Japan. But I also was impressed at how the French people spent their weekends focused on their families.”
He found that Leti’s openness and commitment to innovation provide an encouraging setting for serious researchers.

After lunch in the cafeteria, people gathered in a space for coffee, with a wonderful view of the snow-covered mountains,” Prof. Nishi recalled. “It was very nice to speak with Leti people in that setting and, in fact, some very interesting ideas came from those discussions. I tell my colleagues that if they have the chance to work in a foreign country, Leti in Grenoble is the best choice.”

Massachusetts Institute of Technology 

“Not only were the people we worked with at Leti very creative, they were also very warm and welcoming.
These things fueled our interaction,” said Professor Manalis.

The partnership between the Massachusetts Institute of Technology (MIT) and Leti began in late 2012, initially involving Leti manufacturing devices that were historically designed in labs at MIT. According to Professor Manalis,

A colleague at Caltech had often told me great things about Leti. I knew that Leti had an excellent team that made very complicated devices with high precision and reproducibility.” 

In 2016, the partnership evolved to focus on a scientific research and development project, involving suspended microchannel resonators (SMRs). This technology is based on a hollow cantilever beam oscillating in vertical flexural mode, with a buried microchannel inside, to allow fluid to flow within it, while the resonator is suspended in a vacuum cavity. Leti helped to design the SMR components and then manufactured them using state-of-the art techniques.

Professor Manalis said, “What Leti did involved three different types of bonding steps—an anodic bond, a fusion bond, and a eutectic bond. Each of those bonding steps can be challenging to do well. Doing two of them in a process is certainly a lot harder than one. And Leti did three! In addition to those three bonding steps, there were many others that, taken one at a time aren’t terribly hard, but when done in combination with multiple bonding steps, become increasingly complex. These other steps include making piezo resistors, drilling holes in glass, etching glass channels, etching silicon channels, and etching deep p into silicon to undercut the underside.
The ability to make these sophisticated devices is unique and is a distinguishing quality of Leti. Importantly, the devices were delivered on schedule and they performed well.”

Setting up serial SMR arrays, and using piezoresistive readout to monitor several SMRs in real-time, the research and development project made it possible to measure and compare the growth rates of individual cells in a very short period of time. This technology will impact a number of applications, including those requiring the ability to assess the reactions of individual cells to drugs.

“Everybody at Leti was very supportive of our project and collaboration. They have an extremely talented team and state-of-theart resources,” said Professor Manalis.