Enabling energy efficiency in semiconductor manufacturing
As the economy bounces back in 2010, demand and energy prices are beginning to inflate and increasing regulatory attention is being given to environmental protection. Consequently, the need to reduce energy consumption and increase efficiency is more crucial than ever. This imperative is no exception in the semiconductor industry, which is revered as a potential savior for the pending global energy crisis as much as it is condemned for using vast amounts of energy to manufacture its technology. This article discusses activities undertaken by Texas Instruments to continue reducing the amount of energy usage in its facilities.
Sunil Thekkepat, Texas Instruments, Dallas, TX USA
In the past, semiconductor factories have implemented a typical expense-cutting approach during downturns: across-the-board cost reductions, including the reduction of energy use, which makes up one of the largest cost segments for manufacturing operations. Manufacturing tools are idled or shutdown completely, consumption is reduced to the minimum required, temperature is raised in offices, lighting levels are reduced and certain factory operating specifications are relaxed. These are certainly effective means of achieving greater efficiency, but are they sustainable, long-term solutions?
To effectively reduce energy consumption for the long-term, companies must identify energy-intensive operations, develop a strategy to achieve appropriate reductions in the near- and long-term, and encourage a corporate culture committed to further improving energy efficiency in all aspects of operation.
A focused approach in 2009
Texas Instruments takes a global approach to energy efficiency, focusing first on reducing use at its source, sharing best practices between sites worldwide and also seeking "next practices" to enable even greater energy efficiency.
Reducing energy use at its source starts with identifying easy-to-implement projects and includes investing in projects to achieve even greater energy efficiency. TI has long invested in these types of projects. However, since 2005, the company has taken a more focused approach, sustaining capital towards energy reduction projects with simple payback of up to three years At the start of 2009, although there was minimal available capital to invest, sites were focused on reducing consumption. By year's end, TI had successfully implemented 86 projects, which resulted in energy reduction of approximately 34,000mWh (Fig. 1).
|Figure 1. Annual energy savings.|
Sharing best energy efficiency practices between sites has also been a successful means of reducing consumption and saving costs. Equipped with a best practice list of 49 energy reduction practices, buildings globally can comparatively review their performance and identify conservation projects to implement. Each manufacturing site's performance was benchmarked in 2008 and showed an average improvement of 4.5% in 2009. TI plans to refine and expand the list for use as a standard internal process to implement energy best practices at all sites.
A few key projects implemented in 2009 included:
• Implementation of a wider humidity specification for wafer multi-probe area for winter and summer months;
• Reduction of recirculation air velocity;
• Reduction of wafer fab pressure in areas that have closed cassettes;
• Shut down of excess air handling units;
• Installation of variable-frequency drives (VFDs) for datacenter computer room air conditioner (CRAC) units;
• Lowered compressed air pressure;
• Installation of VFD on cooling tower fans;
• Replacement of point of use triple loop chillers for implants with heat exchanger system;
• Implementation of heat recovery from volatile organic compounds (VOC) exhaust system for pre-heating other facilities systems; and
• Installation of our first "green" living roof on a portion of the new assembly/test facility in the Philippines.
TI's continued focus on efficiency and conservation through building best practice sharing, executive support and education campaigns has helped develop an energy-conscious work force. This has enabled greater energy efficiency achievements in operations and product design – inspiring new ideas for tackling energy conservation in the future. Today, in addition to reviewing and implementing best practices between sites, we are focused on the "next practices" to enable even greater energy efficiency.
2010 and beyond
There are three areas that Texas Instruments is concentrating its efforts that will further enable effective energy savings: infrastructure retrofits, equipment upgrades and manufacturing variability. Because Texas Instruments maintains factories and buildings that have been in operations for almost 50 years, this approach is necessary.
As new reliability and efficiency standards for equipment are implemented, TI buildings and infrastructure, especially older facilities, require retrofits to comply. For example, one of TI's Japanese fabs, had to replace its aging and inefficient chillers. TI invested $7 million in the project, including a $2 million subsidy from the New Energy and Industrial Technology Development Organization, NEDO (a government-funded initiative) to replace the old chillers. Through the NEDO subsidy, TI was able to reduce its overall capital investment for a building retrofit, while successfully reducing energy consumption and improving long-term reliability. It was a winning endeavor for all parties. These kinds of investment will be necessary to continue to reduce energy consumption and integrate newer technology in semiconductor manufacturing.
Another challenge in improving energy efficiency is upgrading manufacturing equipment. During the downturn, as several U.S.-based factories shut down, older equipment has become available for purchase at a fraction of its original cost – but without the benefit of energy efficiency measures developed in the past few years. For example, energy efficient vacuum pumps are an excellent choice when purchase of new equipment is needed. With the surplus of available older equipment, however, companies have had little economic imperative to replace older working equipment with new, energy efficient equipment. Equipment manufacturers need to work with semiconductor manufacturers to make it economically viable for fabs to remove functional, yet inefficient equipment, from service and replace it with new, more efficient equipment.
Older, energy-intensive equipment is still used at nearly every TI manufacturing site. As feasible, we phase in new, more efficient models, however, this area is still a rich source of cost savings for TI and other semiconductor companies. Although equipment replacement is often prioritized below fab productivity, there is increasing pressure to reduce energy consumption wherever possible, especially as energy prices and fab loadings are once again on the rise.
|Figure 2. Semiconductor factory energy usage curve.|
Figure 2 illustrates that energy usage for a semiconductor fab is not highly variable. This is primarily because the energy-intensive manufacturing equipment operations are not flexible and they stay on – even when they are not processing wafers.
To make energy consumption more variable, tools and support equipment have to come to a reduced energy state similar to "start stop" engines commonly found in today's hybrid vehicles – they shut down when stationary. Texas Instruments – through International SEMATECH Manufacturing Initiative – has been working on improving the variability through "idle mode" studies and evaluation. A few areas have been identified for reduced energy use in this manner such as RF generators, vacuum pumps, point of use chillers, and abatement equipment. But companies, industry groups and equipment vendors can expand the focus to other areas. Increasing variability in consumption based on processing of wafers will create a flexible and more efficient manufacturing environment as the industry goes through its cycles of economic ups and downs.
Energy use reduction and efficiency improvements in semiconductor manufacturing require sustained focus and investment. Energy efficiency and conservation initiatives can be incorporated in every aspect of operations – from sharing best practices, to investing in infrastructure retrofits and new equipment. Increasing variability in energy consumption within manufacturing tools and improving energy efficiency of mature and older equipment will greatly benefit the industry. Broader, long-lasting energy efficiency achievements may also be made possible through collaborating with industry peers and equipment suppliers.
Sunil Thekkepat received his MS in chemical engineering from the U. of Toledo, Toledo and an MBA from Southern Methodist U., Dallas and is a worldwide energy strategy manager at Texas Instruments,13452 North Central Expressway, MS 386, Dallas, Texas, 75243; ph.: 214-567-7320 and email: email@example.com.