Increasing Wafer Probe Testing Throughput by Means of Servo
A leading manufacturer for precision technologies for the semiconductor industry is now developing an advanced wafer probing inspection machine for highly automated, high-throughput, wafer testing . The machine with an XY stage, contains a total over 15 axes of motion, of which 4 Elmo axes perform the critical/high performance machine motion. Platinum Maestro was also chosen as the master controller for all axes of motion.
Wafer probing machines are automatic testing machines used during semiconductor fabrication to electrically test the integrated circuits of each wafer die, before the wafer is cut into individual dies. During this process two probes move from one integrated circuit to another (as quickly as possible), measuring and evaluating the electrical characteristics of the transistors, interconnections, and other elements within the circuit. Because these measurements need to be extremely accurate, electrical noise within the system must be kept to a minimum.
Elmo’s complete solution proved to be advantageous for several main reasons. Better servo and motion than the competition resulted in settling time between moves of 10ms (with spec was for 30ms). This is a combined results of excellent servo and multi-axis control capability, which means less time between each probe, and better overall throughput. Additionally, Elmo’s servo control allowed for stand-still jitter <20nm (with spec <100nm).
Elmo’s inherent negligible EMI, thanks to its fast and soft switching technology (FASST), is critical for such probing machines. The electrical measurements of the probes are the critical element of the process, and any EMI could be a disturbance, therefore requiring the addition of EMI filters. With Elmo’s negligible EMI, the bulky, expensive, and time consuming filters became obsolete, resulting in a better performing machine that is also leaner. The customer reached desired performance, yet did not have to invest time and effort into developing immunity solutions for an electrically complex environment.
Beyond contributions to the overall machine productivity, Elmo’s unique physical characteristics further improved the machine. The miniature yet ultra-powerful servo drives were mounted within the machines and on moving loads. The drives extreme power conversion efficiency, a major contributor to their minimal size, also means that the machine itself is more efficient with less energy consuming cooling methods which often require maintenance and other overheads. The drives’ ability to withstand mechanical shocks and high accelerations meant their installation deep within the machine and on moving mechanics could save the machine not only cables and cable-carriers running in and out of the machine, but in-fact the entire electrical box. Removal of the electrical box, resulted in approximately 30% volume reduction.
This project exemplifies how the customer was able to cut costs through innovative motion technology, while also significantly improving the overall machine productivity. The overall throughput was improved drastically while reducing machine footprint. This was achieved without having to change any of the existing machine mechanics, but rather focusing on better servo control, along with Elmo’s capabilities in efficiency, negligible EMI operation, and robust operation.
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