SEMI F47: Increased Power Quality Concerns in Chinese Fabs

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SEMI F47: Increased Power Quality Concerns in Chinese Fabs

Due to the sensitivity of equipment and process controls, semiconductor fabs require high levels of power quality. Voltage sags are the number one power quality problem for equipment, because a 200 millisecond voltage sag could easily trigger EMO (emergency off) on various tools and cause productions lines to go down for hours. SEMI F47-0706: Specification for Semiconductor Processing Equipment Voltage Sag Immunity defines the voltage sag immunity required for semiconductor processing, metrology, and automated test equipment. However, for semiconductor fabs, the decision whether or not to adopt F47-compliant solutions must strike a balance between reduced vulnerability to voltage sags and increased equipment cost. Based on feedback recently received by SEMI China, awareness of SEMI F47 is steadily increasing across the Chinese semiconductor industry.

During the early boom years of China’s semiconductor manufacturing industry, the SEMI China office organized several educational workshops for local fabs, addressing voltage sag mitigation through adoption of existing industry standards and other relevant sag immunity solutions. Although all major local IDMs and foundries participated in these workshops, the majority of attendees came from facilities-related departments, because fab engineers had generally assumed that power problems were directly related to factory facility divisions.

During these workshops, discussion on F47 and voltage sag immunity solutions often focused on cost concerns because costs are especially critical for local foundries during industry downturns.

  • Which solution is more costly—improving the quality of power or making the loads tougher?
  • Why should tool owners and key account managers increase their cost of equipment if both solutions work?
  • Will uninterruptable power supplies (UPS) be able to deal with most power dip problems, and are they cost effective?

The cost of voltage sag mitigation is not the only big concern. Tool owners have found it difficult to quantify losses attributable to voltage sags, as local industry still lacks statistical data to characterize power quality. While it is known that voltage sag triggered EMO shutdowns in Beijing and in Shanghai’s Zhangjiang Industry Park, where China’s top three foundries are located, there is little data to show how strongly correlated these were to poor power quality, or what the main characteristics of the poor power quality were.

Recent years have seen improvements, fabs, equipment suppliers, and solution providers have raised the awareness of power quality problems at the tool level. Several fabs in Shanghai have started monitoring power quality, and the industry is now discussing collaboration to collect comprehensive data for larger areas such as industrial parks or for districts such as the Yangzte Delta. This awareness is not only among semiconductor manufacturers - photovoltaic materials factories are also showing interest in monitoring how voltage sags affects their dicing tools. In addition, some tool makers are performing SEMI F47 sag immunity characterization tests in their facilities in China. With comprehensive power quality data, tool owners will have enough confidence to choose tool-level options for damage mitigation.

Making tools immune to voltage sags could be both cheaper and more reliable. The involvement of local technical experts in the SEMI International Standard Program will be needed to convince local industry to adopt compliance solutions. Input from local industry will help determine whether existing standards have covered all the scenarios that occur in the local power grid.

For more information, and to get involved in SEMI Standards activities in China, please contact Mr. Steven Gan at

September 1, 2009