Speed up wafer testing by 30% with Elmo’s fast-settling servo drives

Background

Semiconductor fabrication requires a complex sequence of time-consuming steps using highly sophisticated and expensive equipment. The microelectronics industry can deliver massive computing power at a reasonable price only because of batch processing—the ability to fabricate hundreds of identical chips simultaneously on “wafers” the size of dinner plates. However, the economics of batch processing only holds if the chips are operational. Therefore, rigorous testing is essential for process control, quality assurance, and standards compliance.

Machine requirements

When semiconductor test-equipment manufacturer Proaut Technology GmbH began to upgrade its PMA wafer-testing series, the goal was to achieve a throughput of 40,000 components per hour from their existing machines, up from their existing throughput of 30,000.

The system tests sections of the wafer sequentially, taking measurements and then advancing and aligning the wafer to place the next area beneath the measurement tips. But, with quick move-and-settle positioning, inertia can cause the load to overshoot and oscillate, which can introduce measurement errors or slow down the process.

Controller and drives are installed in a centralized cabinet in the system. This simplifies wiring and integration, but packing multiple drives into a small, enclosed space traps heat that could potentially degrade performance and cause early failure of the electronics. Downtime in the semiconductor industry can cost hundreds of thousands of dollars per hour, so the team needed to avoid this problem.

Moreover, with individual devices measuring in mere millimeters, test equipment needed to be both compact and precise, and the process needed to be fast enough to keep up with the output of the microlithography machines.

Motion control solution

• Gold Whistle Servo Drive

The Proaut team chose the Gold Whistle servo drive family to meet their needs. Gold Whistle drives include a function called “gain scheduling” in which an algorithm enables the system to define separate sets of controller parameters to optimize system performance for each of several distinct application conditions. During operation, the drive can automatically change from one set of controller parameters to another based on the working point of the servo drive. The filtering helps smooth the effect of changing controller parameters, leading to faster settling.

Gold Whistle drives operate at >99% efficiency, which minimizes the amount of heat that needs to be dissipated. In addition, their small size enables the use of a smaller cabinet, minimizing machine footprint. “The PMA machines are very compact, with a small internal switch cabinet,” said Thiol Wicht, Managing Director of Proaut Technology GmbH. “The mini size of the Gold Whistle servo drive is very beneficial to our latest technology machines.”

Gold Whistle drives also feature built-in safety functionality such as “safe torque off” which enables the drive to remain energized while removing torque from the axis. The combination speeds up restart while ensuring the safety of operators, equipment, and product. In addition, Gold Whistle drives are available with a choice of EtherCAT or CANopen. The ultrafast cycle times and minimal jitter of these protocols support best-in-class real-time performance.

Results

Elmo’s Gold Whistle drives enabled Proaut to increase the throughput of its latest-generation semiconductor test platform by 30%. The compact and efficient drives support a high-reliability solution with a small footprint. “The servo controllers of Elmo Motion Control fully meet all the criteria for our application,” says Mr. Walsh. “They are ruggedly constructed and predestined for use in our precision measurement machines.”