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High-speed Transmission of Large Data Volumes Using MEMS

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While incorporating an increasing number of advanced functions, mobile phones are also becoming more and more compact in design. Sending and receiving video images via mobile phone has already become a common phenomenon in Japan. In the future, the demand for more rapid transmission of large-volume data is expected to increase. MEMS is an essential element for making this happen.

RF switch under development enables stress-free transmission of video images.

RF switch under development enables stress-free transmission of video images.

A mobile phone incorporates many switches for controlling various electrical signals. To transmit and receive high-volume data such as video more speedily, switches capable of handling high-frequency requirements are necessary. RF (radio frequency) MEMS* is now in the spotlight as a means of effectively responding to this need.

*RF MEMS is one of the MEMS research projects adopted by the New Energy and Industrial Technology Development Organization (NEDO).

OMRON's MEMS technology

One type of RF MEMS device is an RF switch that can handle frequencies 10 times higher than a semiconductor-based switch. To enable smooth On/Off switching with almost unlimited reliability while keeping dimensions to a minimum, OMRON has created an "eagle" structure spring through etching. The spring is capable of extremely flexible movement, like an eagle's wings, hence the nickname "eagle."

Mechanism of OMRON's
Mechanism of OMRON's "eagle" structure multi-spring system

MEMS: The smallest "sculpture" in the world.

OMRON's MEMS chip is extremely small-measuring just a few square millimeters. But it incorporates a 3D solid structure that functions as a sensor as well as a complex system integrating numerous functions. OMRON's cutting-edge MEMS technology is what makes miniaturization of all these highly sophisticated components possible.
Creating such components requires super-high-precision micrometer or nanometer-level processing. The process of removing portions of a silicon material through etching, and bonding the silicon with a glass layer to form 3D structures is akin to creating an exquisite sculpture on the world's smallest scale. Even the most minute error or slightest deviation is unacceptable. This process is different than that used to make an LSI, which is more comparable to drawing a picture on a silicon canvas using a "wiring" technique.

With its head-start in MEMS development, OMRON has accumulated expertise and technological resources in the field, and has already advanced its capabilities to a level that enables processing with precision in the tens of nanometers. Because of this world-leading technological capability, OMRON can create a MEMS sensor that is extremely small with outstanding functionality and reliability.

H-pattern etching simulation
H-pattern etching simulation
Silicon substrate is dissolved using an etching solution to form a deep indentation.

What is the semiconductor fabrication technology that underlies MEMS production?

Semiconductor manufacturing borrows from photo development techniques. A silicon wafer is uniformly coated with light-sensitive resin solutions and exposed to a light pattern that imprints a corresponding circuit pattern. The unwanted layer is then removed from the wafer surface through etching. This series of semiconductor fabrication processes serves as the basis for MEMS micromachining.

Why is silicon the material of choice?

Silicon is a material that is present in large amounts in glass and stones. It has semi-conductive characteristics, which enables the formation of both conductors and insulators, each as small as 0.1 micrometer in width. The conductors allow electrons to pass through while insulators prevent the passage of electrons. With these unique advantages, silicon is used as a main component for all types of computing devices, from PCs to mobile phones to household appliances. As a substrate, MEMS uses a disc-shaped monocrystal silicon wafer, on which silicon atoms and molecules are aligned In addition to having the characteristics of semiconductors, monocrystal silicon is very tough and withstands repeated exposure to vibration and pressure. Therefore, when used in sensors and actuators, this material enables reliable performance to be maintained for long periods of time.

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