by Miles Budimir, Senior Editor for Design World—
It’s a truism that we live in the digital age characterized by easy electronic communication, both in our personal and professional lives. Cell phones, tablets, slim laptops and so many more consumer and business products all take advantage of the steady march of Moore’s Law which has described (and predicted) the growth of the electronics revolution since the mid 1960s.
At the heart of that revolution is the integrated circuit (or IC) and the semiconductors that make up those circuits. These days, technological advances in semiconductors are happening in the realm of power electronic circuitry. Lee Stauffer, senior staff technologist at Keithley Instruments, sees the most significant changes in the area of semiconductor materials. “Silicon carbide and gallium nitride are having a major impact on the development of high-power semiconductor devices like MOSFETs and diodes,” he said. “They offer significant advantages over silicon devices in that they can handle higher temperatures, have a higher breakdown voltage and are intrinsically faster. These advantages open up a world of new design opportunities for power electronics, allowing designers to improve efficiency and reduce the size or cooling requirements.”
A key driver of these changes is the energy industry. “In the industrial sector, better electronics provide for higher efficiency in motor controllers, lighting and power supplies,”said Stauffer. “In the energy generation arena, new energy conversion electronics are bringing unprecedented efficiency in areas that include dc-to-ac, ac-to-ac and ac-to-dc conversion.”
The semiconductor industry, from production to testing, relies on extreme precision motion control, living as it does in the nanometer world. Bob Setbacken of Heidenhain explained the key role that encoders play in this extreme precision environment.
“An example where extreme demands upon encoder performance are being made is in semiconductor manufacturing. As circuit geometries approach 10 nm, there is a concurrent need for positioning systems capable of supporting motion control at these extremely fine resolutions. In addition, the focal length of the imaging equipment is measured in microns, so the demands for positioning extend to not just x-y, but also z. Wafer sizes are now heading towards 450 mm and are so thin that the simple act of putting the wafer into a chuck will cause distortions which much be accounted for. The result is a motion system that must control not just the three linear axes, but also three rotational, and with resolution approaching the atomic level. These systems are truly complex and are crafted to the equipment by teams of scientists and engineers,” he said.
Such extreme precision requirements place demands on the electric motors used in semiconductor manufacturing as well. “The semiconductor and medical laboratories are measuring items in the low nanometer (less than 50 nm) region,” said Dan Jones, president of Incremotion and a motor design consultant. “The coordinate measuring machines (CMM) need electric motors with extremely smooth speed responses, meaning no cogging and no ripple,” he added.
One of Jones’ clients, Applimotion, provides the direct drive brushless motor family needed to create the necessary position accuracy. “No gear boxes can be used so the lower motor speeds (less than 200 rpm) can be achieved magnetically,” he said. Jones also noted that because “the direct drive brushless permanent magnet motor growth is three times the traditional brushless permanent magnet motors, they are finding new applications as tighter position accuracies are needed.”