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Nanometre components require sub-nanometre precision


Semiconductors are an integral part in most electronicdevices, and the racehorse in the charge towards greater computing power.Without these tiny components, we would not have been able to enjoy oursmartphones and hyper-realistic video games. Semiconductors have evolved tremendously since they werefirst developed; as more and more computing power is sought after, the siliconchips shrink in size and, today, the smallest wafers are just 2 nm - a fractionof the width of a strand of DNA. Smaller chips means that the distance theelectrons need to travel is decreased, allowing much faster processing.Unfortunately, it makes both the manufacturing and validation processesextremely difficult.

Time is money
Since semiconductors are necessary in virtually all types oftechnology, they are constantly in high demand, and it is important that themanufacturing process is efficient. A single chip can take a month tomanufacture and, depending on the design, the process can consist of 1,000 to2,000 steps. It is common to check the device for faults between processingsteps, since moving to the end phase of the manufacture would be a waste oftime and money if the semiconductor has a defect.

Challenges at every step
Scanning semiconductors for flaws requires extremelyaccurate motion control. As precision cannot come at the cost of speed, thesystem must be able to move from point A to point B as quickly as possible.Ideally, the motion will start instantaneously after the command has beengiven, and come to a full stop as soon as the exact position has been reached.In addition, when used in dynamic processes, for example when measurements areperformed during movement, the inspection head needs to be triggered at exactlythe right spot. However, in practice, there will always be some latency - adelay before the inspection head is activated, and some settling time beforethe motion of the stage stops completely. There will also be some positioninginaccuracy, especially during acceleration. This latter issue can be affectedby many factors, such as flaws in position feedback system or drive mechanism,or guidance errors in the bearings. Another common issue is vibrations causedby the movement of the stage. These interferences will disturb the system and,if the vibrations occur at one of the natural frequencies of the appliance,they will be amplified. One way to fix this issue is to make the system asstable and robust as possible, but these disturbances are hard to remove completelyduring fast movements.

Innovative motion control powered by smart software
ACS Motion Control is a global supplier of motion controlsystems, including controllers, motor drives, specialised IOs and various smartsoftware tools. The company was founded in Israel in 1985, and has since spreadall over the world - with offices in the USA, Germany, China and Korea - andjoined the Physik Instrumente (PI) group in 2017. ACS's products are used in arange of applications that require high precision motion control, fromoptical-, ultrasonic- and e-beam inspection to X-ray, dimension metrology andmaskless lithography.

Software that can learn
ACS's high performance motion solutions are powered byintelligent software that helps the hardware to perform at its best. Itspatented NanoPWM technology uses both PWM- and linear power amplifiers,allowing the stage to move at high speed and settle in nanometre-sized windows.The MotionBoost algorithm creates motion profiles aimed at minimising vibrationand settling times, by reducing the energy supplied to the stage throughfriction or moving parts. The effects of disturbances are further reduced bythe ServoBoost software, which works in real time to identify and compensatefor perturbations caused by cogging, load changing and cross-axis interactions.This ensures faster settling, lower jitter and decreased dynamic error comparedto standard PID-based algorithms. The newest addition to the ACS portfolio isLearningBoost, a state-of-the-art control algorithm that can not only sense andcancel out disturbances, but also predict them, by learning the way the systemperforms and which movements usually cause perturbations. CouplingLearningBoost with the other software packages from ACS will enable previouslyunachievable throughput and accuracy, making a huge difference for applicationssuch as semiconductor production that rely on high-precision motion control.

PI in brief
PI (Physik Instrumente), headquartered in Karlsruhe, is themarket and technology leader for high precision positioning technology andpiezo applications in the semiconductor industry, life sciences, photonics, andin industrial automation. In close cooperation with customers from all over theworld and for 50 years now, PI's specialists (approx. 1,300) have, again andagain, been pushing the boundaries of what is technically possible anddeveloping customized solutions from scratch. More than 350 granted and pendingpatents underline the company's claim to its leadership. PI has six production sitesand 15 sales and service offices in Europe, North America, and Asia.

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