By Jim Montague, Executive Editor
Keep it simple. For all its complexity, an automated machine’s main requirement—after making good product—is to do its job as simply as possible.
However, duplicating and replacing human movements historically required a lot of mechanical equipment, and so automating and controlling those components became equally complicated. Cable bundles and trays grew to the point of bursting, and some builders still joke that cabinet space is the world’s most expensive real estate.
In recent years, the advent of increasingly capable computers and software, and then digital networks, lightened the load on the hardware. As these assets took on more jobs that formerly were hardware-based, basic operations, changeovers between production runs, maintenance, troubleshooting and repairs became a little easier—if you knew how to write the right code and make the right network links.
Also, as these newer machines evolved, many began to draw their I/O points out of traditional cabinets, closer to the production lines and near or onto the machines. This gathering and distribution of control components resulted in increasingly modular and almost Lego-like machines, which can be plugged in and pulled out as needed, thanks largely to those simpler networking connections and software.
Linkable Wafer Handling
Semiconductors usually are made by robots in vacuum-maintaining mini-cleanrooms called cluster tools. But their traditional radial design became unwieldy and expensive as wafers grew bigger and semiconductor processing became more complex.
BlueShift Technologies, Santa Barbara, Calif., recently used a more linear design to build QuickLink, a modular wafer-handling system, which it claims is 30-40% less costly because it has a smaller footprint, easier reconfiguration, better quality and increased throughput than conventional radial handlers.
Wafers pass along a line of BlueShift’s process modules and transfer chambers that are smaller than radial chambers, and this reduces raw material and etching costs. QuickLink’s linkable design lets fab operators add processing modules as needed in a compact configuration with footprint reductions up to 40%, compared with radial footprints, and optimize throughput by balancing the workflow, while eliminating bottleneck processing chambers. BlueShift believes these building blocks make it easy for users to configure wafer-handling systems for high capacity and long process time, high throughput and short process time, or increased vacuum isolation and contamination control.
Robotic Motion Control
Robot design is critical to any wafer-handling system. High repeatability is essential to avoid damaging the wafer, while providing high throughput requires high speed. “Because these robots are designed to operate in a vacuum, they have to provide smooth and accurate motion with as few moving parts as possible,” says Chris Kiley, BlueShift’s engineering vice president. “When initial systems originally were designed there were no off-the-shelf (OTS) motion control components that could meet these needs. However, when we designed QuickLink, we saw that high-reliability, low-cost OTS components had improved enough to handle this application.” The company started with motion control cards and amplifiers based on Firewire A. “However, we found that its motion control card couldn’t run more than one robot axis at a time, and each of our robots has three axes—the alpha and beta rotational axes and a z-axis for vertical motion,” says Kiley. “Our design specifies that one card will control an entire wafer-handling system which might easily have six robots.”
Consequently, BlueShift began to work with Target Electronic Supply, a system integrator in Westwood, Mass., that concentrates on motion control. “BlueShift wanted to add axes as needed to support their modular architecture, and so I thought Danaher Motion’s XMP motion controllers were a good match,” says Les Peabody, Target’s manager. “These controllers provide up to 32 axes and support servo update rates up to 16 kHz.” The XMPs communicate via SynqNet, which Peabody says provides a synchronous real-time connection between the motion controller, servo drives, I/O modules and custom nodes.