scope:

INTRODUCTION

World production of semiconductors was valued at US$256 billion in 2007, with average annual growth 12-13% per year over the last two decades (Semiconductor Industry Association 2008). Previous studies have shown that the energy and materials intensity of semiconductor manufacturing is surprisingly large given the tiny physical scale of products (Williams et al. 2002, Murphy et al. 2003). The high energy intensity required is due to needs for pure inputs and tightly controlled environments for semiconductor processing. In addition, purity standards for input materials are elevated with the decrease in feature size for microelectronic circuits (Krishnan et al. 2008). Attaining and maintaining the purity standards in controlled environments induces substantial energy and materials uses. Since the Kyoto Global Warming Conference in December 1997, understanding and mitigating the emission of carbon dioxide (CO₂) from industrial processes has become an important issue.

In Taiwan, up to 98% of energy supply is from imports. In 2006, the industrial sector accounted for 58% of the total national energy consumption annually, with the integrated circuit (IC) industry used 12% of the total annual energy. Since the Kyoto Global Warming Conference in December 1997, understanding and mitigating the emission of carbon dioxide (CO2) from industrial processes has become an important issue. The electronics industry such as integrated circuit industry is primarily composed of high-tech Original Equipment Manufacturers (OEMs) and Original Design Manufacturers (ODMs) in Taiwan. The electronics IC industry is not only capital- and technology-intensive, but also energy-intensive. The characteristics of energy use in a wafer- or IC-fab include:

1. A high recirculation rate of filtered airflow in order to maintain a high air cleanliness level, resulting in high fan power demand.

2. Precise and tight controls of cleanroom air temperature and humidity (e.g., 24±0.5oC and 40±5% RH), resulting in high energy demand and use for the simultaneous cooling and heating of air.

3. The manufacturing tools and process equipment consume significant energy, which in turn impose high heat load that need to be removed from the controlled environments.

4. A large amount of ultra-pure water and pure gases are used, which must be supplied by processes with highenergy consumption.

5. High flow rates of exhaust air and outside air require significant transport and treatment energy.

Limited open literatures on investigating energy uses in wafer or IC fabs exist. Yao et al. (2003) compared energy use to produce two generations of computer chip products (i.e., Pentium Pro and a Pentium IV), which showed that producing a latter generation chip required 29% less energy than its processor. Xu (2003, 2004, 2008) reported energy consumption and particle control of facility systems of various microelectronics fabs including minienvironments in the USA and characterized fab energy use in terms of energy use or power demand normalized by cleanroom floor area. Hu and Chuah (2002) studied the energy consumption of wafer fabrication plants in Taiwan. Naughton (2007) proposed SEC data in meeting the requirements or goals set in the International Roadmap for Semiconductors. Prior to this investigation, however, published energy demand data for IC A/T fabs in Taiwan are essentially non-existent. This is perhaps due to a combination of the following reasons: energy consumption data of the mission facilities in IC A/T fabs are often not readily available or sharable. In addition, a certain level of sophistication and expertise is required for obtaining the data through measuring and monitoring power demand or consumption of the complex facility and process systems. Added to the complexity, energy conservation has not yet been on the highest priority list in the semiconductor industry in Taiwan, and very few survey studies have been conducted. Given that Taiwan is now a major manufacturing base for semiconductors in the world, with IC A/T industry most notable in that Taiwan has a worldwide market share of more than 45% of IC assembly and 60% of IC testing (Industry Technology Research Institute 2006), it is important to develop information on energy use and assess energy saving potentials in the industry.

The overall goals of this study are to develop referencing information by obtaining specific energy consumption (SEC) data from the IC industry, which can be used by the industries, plant builders, energy companies, and government agencies to identify opportunities and enhance energy efficiency in the IC industry. Specifically, this study focuses on SEC for two sectors in the IC industry - the IC assembly and testing that are the back-end stage processes in IC manufacturing.

The technical objectives of this study include (1) to quantify and compare the SEC levels for IC A/T fabs, and (2) to identify the opportunities for energy-savings in the IC fabs in Taiwan. This study covers all the power uses in the fabs, including the facility systems, process tools, offices and garages, etc. The facility systems include chiller plants, makeup air, recirculation air, exhaust air, nitrogen, compressed dry air, process cooling water, vacuum and ultra-pure water systems.