December 8, 2022
  • December 8, 2022

Thermal actuator and MEMS sensor improvements

By on June 25, 2021 0


Researchers at Carnegie Mellon University are exploring efficient alternative materials for use in thermal actuators and sensors in microelectromechanical systems (MEMS) Credit: Carnegie Mellon University De Boer Institute

Cell phone accelerometers, laptop microprocessors, and drone balancing gyroscopes each rely on microelectromechanical systems, or MEMS for short. Within these small systems are smaller devices that perform a variety of physical functions, called actuators and sensors.

The first is a thermal actuator that converts energy into motion by expanding and contracting the material due to changes in temperature. There are MEMS thermal actuators in computer disk drives, scanning probes, and micromotors.

Currently, these thermal actuators are based on polysilicon. Polysilicon is a material that requires high temperatures and consumes considerable energy during the manufacturing process. While working on related research, researchers at Carnegie Mellon University’s Faculty of Engineering found that they had found an effective alternative.

The team led by Maartende Boer, professor of mechanical engineering, prefers tantalum to polysilicon. This reduced both the operating temperature and the power consumption required for a given amount of operation. The results were published in Nature Microsystems & Nanotechnology.. Following further investigation, Journal of Microelectromechanical Systems.

Tantalum is a rare refractory metal and is often used in alloys to increase strength and durability. The researchers found that tantalum thermal actuators have a higher coefficient of thermal expansion of the metal than the silicon substrate they are made of, resulting in less than half the power for the same force and displacement as those in polysilicon. I theorized that it would take an entry.

Tantalum, which operates at lower voltages than other thermal actuators, is directly compatible with complementary metal oxide semiconductor (CMOS) circuits. Tantalum devices can also be processed near room temperature.

“In principle, this study shows the feasibility of not only making thermal actuators using tantalum, but also of using many sensors for use in a wide range of integrated nanoelectronics,” said deBoer. Said.

During the manufacturing process of microprocessors, phones, or other devices, manufacturers typically place MEMS components on one chip and CMOS electronic components on a second chip.

De Boer’s team believe that tantalum as a MEMS structural material can eliminate both the need for two separate chips and the extra wiring that sends signals between them. This allows for more efficient devices with less material, lower manufacturing costs and better performance.

Other researchers looked for a way to eliminate the second chip, but found that the high temperatures required to make MEMS were a barrier. The DeBoer team fixed this problem.

Second article published in Journal of Microelectromechanical SystemsConsidered the use of aluminum nitride to maintain low temperatures during the MEMS manufacturing process. This increases the likelihood of developing both MEMS and CMOS on the same chip with the “MEMS-last” approach. This is of interest to both foundries and so-called millless MEMS companies.

“When it comes to CMOS integration, it’s very exciting because it helps us use full CMOS under MEMS,” said Gary Fedder, professor of electrical and computer engineering. “The density of tantalum is about 7 times that of silicon, which makes it a good standard mass. This is a big problem because transducers of similar sensitivity can be 7 times smaller.

The findings have the potential to have future implications for a variety of industries that require sensing technology, such as aerospace, healthcare, optical networks, and robotics. De Boer and his students have filed three provisional patents in tantalum processing for MEMS.

Other authors of technical papers and provisional patents include Longchang Ni and Ryan Pocratsky, both with doctorates. Student in the Department of Mechanical Engineering.

Marketed photonic MEMS switch

For more information:
Demonstration of tantalum as a structural material for thermal actuators Ni, L., Pocratsky, RM & de Boer, MPMEMS. Microsyst Nanoeng (2021). DOI: 10.1038 / s41378-020-00232-z

L.Ni and MP de Boer, “Sacrificial Materials and Emission Etching Liquids for Metal MEMS to Reduce or Eliminate Residual Stress Changes Due to Hydrogen” Journal of Microelectromechanical Systems.. DOI: 10.1109 / JMEMS.2021.3069397 ..

Provided by
Mechanical Engineering from Carnegie Mellon University

Quote: Appetizing Tantalum: Improvements to MEMS thermal actuators and sensors obtained June 25, 2021 (June 25, 2021)

This document is subject to copyright. No part may be reproduced without written permission, except for fair dealing for the purposes of personal investigation or research. The content is provided for informational purposes only.