|What is MEMS Technology?
MEMS is an acronym for MicroElectroMechanical Systems. Chances are you use MEMS every day and may not even know it. A MEMS device will activate an airbag in your car if there is a crash. Every time you use an inkjet printer, MEMS devices pump the ink. And if you visit someone in the hospital, their blood pressure might be monitored by a MEMS pressure sensor.
MEMS is a platform technology that is used to create tiny devices, ranging in size from a few microns to a millimeter across. They are typically fabricated from silicon or glass wafers, but MEMS technology has grown far beyond its roots in the semiconductor industry. A typical device is an integrated microsystem on a chip that can incorporate moving mechanical parts in addition to electrical, optical, fluidic, chemical and biomedical elements. The resulting products can respond to many types of inputchemical, light, pressure, vibration, and acceleration. Because these devices are smaller than conventional machines used for sensing, communication and actuation, it is possible to use them in places where mechanical devices could not be previously be put, such as inside a blood vessel of a human body. MEMS devices also act faster and consume less power than conventional machines.
Many believe that MEMS will have an even larger impact in the 21stcentury than computer chips had in the 20th. MEMS are driving revolutionary changes in communications, life sciences, and micro-instrumentation fields. Soon substantial parts of the Internet will use MEMS-based optical switches, speeding up your connection to the web. Thanks to MEMS, the electronics of a cellular phone will shrink to fit inside a wristwatch. High definition television outfitted with millions of microscopic MEMS mirrors will provide crisper, cleaner pictures. The medical field will go through tremendous changes as it exploits MEMS to enable implantable monitoring devices, blood and DNA analysis chips, and microfluidic devices that reduce the size and expense of diagnostic and therapeutic equipment.
Q. What do MEMS, MOEMS, and MST stand for?
A. MEMS stands for MicroElectroMechanical Systems, a class of small devices that integrates tiny mechanical and electrical components on a silicon chip. MOEMS stands for MicroOpticalElectroMechanical Systems, which in addition to mechanical and electrical components, integrate waveguides or other optical features into the body of the silicon chip. MST, commonly used in Europe, stands for Micro System Technology and is often used to describe MEMS.
Q. Is MEMS a new technology?
A. No. MEMS have been studied in research labs for some time, beginning in the late 1960s. The first commercialized MEMS devices appeared in the early 1990s in the automotive industry. Later in the decade many industries began to recognize the promise of the technology to reduce costs and systems sizes.
Q. How small are MEMS?
A. MEMS themselves are typically measured in microns (By comparison, the diameter of human hair is about 100 microns). A MEMS device, which may include an array of MEMS or other packaging solutions, ranges from a few millimeters to several centimeters.
Q. What are some MEMS products? Who uses them?
A. Youve probably encountered MEMS in your everyday life and you may not have realized it. Because of their reliability and small size, MEMS devices were first used in automobile airbag systems, compact computer display projectors, and inkjet printers. A MEMS accelerometer tells all car airbags when to deploy, a MEMS mirror array creates the dazzling clarity of many modern projectors, and a MEMS nozzle allows inkjet printers to create high-definition print.
Q. What are future MEMS applications?
A. MEMS is a platform technology with a myriad of possibilities. MEMS devices will almost certainly be used in advance yaw-control systems for automobiles and aircraft. They will also be used increasingly in implantable medical devices and surgical equipment to minimize the intrusion of medical procedures. MEMS devices will be used to create portable biochemical test systems that deliver instant chemical analyses. In perhaps one of the most significant applications, MEMS could be used to create tiny integrated optical systems and, eventually, an all-optical Internet that will operate at speeds unimaginable today.
Q. How are MEMS made?
A. MEMS devices start from a wafer made of silicon, polysilicon, glass or other material. In some processes, a series of etch steps are used to carve features, such as a micromirror or cantilevered beam into a wafer. In other processes, multiple layers of a material, typically polysilicon, are deposited on the surface of a wafer and then etched away selectively, leaving complex multi-layered features such as comb drives, hinges, and latches on the surface. MEMS devices are then tested, cut into dies, and often mounted on electronic circuit boards. Getting the process right is difficult and typically requires either extensive trial-and-error prototyping or sophisticated design tools that are linked closely to and validated by the specialized manufacturing processes used to produce MEMS.
Q. How are MEMS different from semiconductors?
A. MEMS processes grew from traditional semiconductor technology. Over the last decade, the processing methodology for MEMS devices has evolved independently. While on the surface, both semiconductor and MEMS batch-process wafers patterned by photolithography, MEMS-specific manufacturing creates moving parts on wafers by removing sacrificial layers beneath desired mechanical structures. This fundamental difference has several processing implications. MEMS processing typically involves deeper, more specialized etches, and may fuse wafers into a stack to create a large multilayer device. MEMS devices may often have features on both sides of a wafer. Finally, while semiconductor foundries typically have process lines that are optimized for commodity production, MEMS foundries have become highly specialized and flexible to accommodate newly developed MEMS processes.