According to Joel Galliher, semiconductor industry manager, Bosch Rexroth Corp., the semiconductor industry is moving away from its focus of perfecting microelectronic processes. As wafers become larger and feature smaller widths, issues like productivity, throughput, reliability, and automation have gained importance.
Moving wafers into and out of a fabrication tool, positioning and repositioning them within the tool, and changing setups and job parameters significantly influence the overall productivity of the tool. “As tools process wafers faster and more accurately, it becomes more apparent that the bottleneck is material handling,” noted Galliher. “The more time the tool spends waiting to receive a wafer, the less efficient is the overall production. Thus, efficient wafer handling between tools is increasingly viewed as critical to improving productivity.”
Semiconductor fabs are significantly increasing the levels of automation, replacing manual transport with automated material handling systems and turning more attention to the flow of materials throughout the fab. Thus, process integration, such as enabling in-line metrology to detect errors faster and earlier to increase yields, is needed.
Automation components must also deliver product to the processing area more efficiently. “For example,” noted Galliher, “simply increasing the speed of motion in transferring wafers is not sufficient. The mechatronic handling systems must be tailored to meet cycle time requirements, yet still protect delicate, high-value wafers.”
Toolmakers in the semiconductor industry are beginning to outsource non-core engineering. For example, one wafer-processing equipment manufacturer looked outside to develop a high-performance wafer lift subassembly. “The company had been purchasing about 30 separate components from a handful of vendors and was building the lift assembly in-house,” said Galliher. “While the existing design worked well, the OEM wanted to reduce engineering expenses for a new lift, lower the cost of the assembly, and streamline the supply chain by obtaining the item as a single part number.” Just a few years ago, such a move was virtually unthinkable.
Toolmakers and fab designers emphasize reliability. It is important to evaluate not only basic performance criteria, but also maintainability, durability, environmental characteristics, mean time to failure, cycle life, and similar metrics that will give some measure of reliability.
Another important factor is the ease with which various components are integrated. “It’s not unthinkable that you would find multiple motion control devices - servo controls, pneumatics, and linear motion - within just a few feet of each other as you move through the fabrication process,” said Galliher. Making sure those devices work well together is a major concern, one solvable through distributed intelligence.
However, distributed intelligence in the drive does more than warn of deviations in ideal running conditions. It can also pinpoint the cause and degree of deviation-telling you whether shutdown is needed immediately or can be scheduled at a later time.
“As they focus more on throughput and efficient material handling,” said Galliher, “fabs are beginning to evaluate their purchase of new equipment on the total cost of ownership principle (TCO). “Investing to buy superior equipment can save in the long run through reduced downtime and time savings. If a fab produces 50,000 wafers a month, downtime costs almost $250,000 an hour. So, there’s a huge incentive to keep operations running smoothly, whether by preventing failures or reducing unscheduled or even scheduled maintenance.
In addition, establishing solid purchasing relationships with experienced, sophisticated suppliers can pay significant benefits, not just in filling orders, but also in helping to solve any number of production problems as they arise. And a supplier who knows the industry can even be a partner in anticipating future needs.
Bosch Rexroth
www.boschrexroth-us.com
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