By Inna Skvortsova, SEMI
Electromagnetic interference (EMI) is an increasingly important topic across the global electronics manufacturing supply chain. Progressively smaller geometries of ICs, lower supply voltages, and higher data rates all make devices and processes more vulnerable to EMI. Electrical noise, EMI-induced signal generated by equipment, and factors such as power line transients affect manufacturing processes, from wafer handling to wire bonding to PCB assembly and test, causing millions of dollars in losses to the industry. Furthermore, conducted emission capable of causing electrical overstress (EOS) can damage sensitive semiconductor devices. Intel consistently names EOS as the “number one source of damage to IC components.” (Intel® Manufacturing Enabling Guide 2001, 2010, 2016).
While EMC (Electromagnetic Compatibility) standards, such as the European EMC Directive and FCC Testing and Certification, etc. provide limits on allowed emission levels of equipment, once the equipment is installed along with other tools, the EMI levels in actual operating environments can be substantially different and therefore impact the equipment operation, performance, and reliability. For example, (i) Occasional transients induce “extra” pulses in rotary feedback of the servo motor which in time contributes to robotic arm’s erroneous position eventually damaging the wafer; (ii) Combination of high-frequency noise from servo motors and switched mode power supplies in the tool creates difference in voltage between the bonding wire/funnel and the device which causes high current and eventual electrical overstress to the devices; (iii) Wafer probe test provides inconsistent results due to high level of EMI on the wafer chuck caused by a combination of several servo motors in the wafer handler. Field cases like these illustrate the gap between EMC test requirements and real-life EMI tolerance levels and its impact on semiconductor manufacturing and handling.
EMI on AC power lines
New standard, SEMI E176-1017, Guide to Assess and Minimize Electromagnetic Interference (EMI) in a Semiconductor Manufacturing Environment, developed by the NA Chapter of the Global Metrics Technical Committee bridges this gap. Targeted to IC manufacturers and anyone handling semiconductor devices, such as PCB assembly and integration of electronic devices, SEMI E176 is a practical guide as well as an educational document. SEMI E176 provides a concise summary of EMI origins, EMI propagation, measurement techniques and recommendations on mitigation of undesirable electromagnetic emission to enable equipment co-existence and proper operation as well as reduction of EOS in its intended usage environment. Specifically, E176 provides recommended levels for different types of EMI based on IC geometries.
“SEMI E176 is likely the only active Standard in the entire industry providing recommendations on both acceptable levels of EMI in manufacturing environments and the means of achieving and maintaining these numbers,” said Vladimir Kraz, co-Chair of the NA Metrics Technical Committee and president of OnFILTER, Inc. “E176 is also unique because it is not limited just to semiconductor manufacturing, but has application across other industries. Back-end assembly and test, as well as PCB assembly are just as affected by EMI and can benefit from SEMI E176 implementation as there are strong similarities between handling of semiconductor devices in IC manufacturing and in PCB assemblies and prevention of defects is often shared between IC and PCBA manufacturers.”
The newly published SEMI E176 and recently updated SEMI E33-0217, Guide for Semiconductor Manufacturing Equipment Electromagnetic Compatibility (EMC),provide complete documentation for establishing and maintaining low EMI levels in the manufacturing environment.
Undesirable emission has operational, liability and regulatory consequences. Taming it is a challenging task and requires a comprehensive approach that starts from proper system design practices and ends with developing EMI expertise in the field. The new SEMI 176 provides practical guidance on reducing EMI to the levels necessary for effective high yield semiconductor manufacturing today and in the future.
SEMI Standards development activities take place throughout the year in all major manufacturing regions. To get involved, join the SEMI International Standards Program at: www.semi.org/standardsmembership.