THE CHALLENGE

After more than 30 years of using aluminum as the main wiring material in semiconductor chips, technology is starting to shift to copper for wiring in advanced devices. In contrast to earlier dry chemical technologies, copper uses two primary wet processes�electroplating and chemical mechanical polishing in the process flow. This has resulted in concern about the presence of copper in the fluid waste stream of chip fabrication facilities. A highly regulated heavy metal, copper creates a variety of permit issues that can create possible delays in bringing the process from research and development and qualification into production.

For Applied Materials, these challenges were significant. Their customers�virtually every major chipmaker around the world�could be affected by permit difficulties and process delays that result from the shift to copper. Other issues were of concern. Besides the environmental concerns of copper in the waste stream and the associated regulatory challenges, copper electroplating and CMP systems have significant water requirements. The need to treat and discharge water, particularly with copper present, is potentially expensive to manufacturers. Applied Materials understood that its customers would need to consider the cost of water treatment when selecting process and equipment options. The economics of water treatment varies according to a region�s infrastructure and pricing systems, so, although the expense of treating and discharging in the United States is not prohibitive, it is much higher in Europe and Asia, where many of the company�s customers are located.

The economics, regulatory issues, and environmental concerns related to the technology all suggested the need for a new approach. As a supplier of both types of wet copper technologies, the company has an interest in seeing that the transition required by the new tools is as smooth as possible for Applied Materials� customers and that EHS issues related to its products do not impede selection of its equipment. Furthermore, as an environmentally concerned company, Applied Materials understands the importance of providing the cleanest technology available on its process equipment. Although Applied Materials� core business is chip-making equipment, the company recognized that postprocessing environmental requirements were an issue of concern for their customers. These concerns led Applied Materials to develop a comprehensive copper abatement solution for its systems that could potentially be modeled by its customers.

THE SOLUTION

As a supplier concerned about EHS factors related to its products, Applied Materials expanded the scope of its efforts beyond the physical boundaries of its tools to identify Total Solutions.� It installed a closed-loop water-recycling system in its own facility to demonstrate to customers how problems associated with the fluid waste streams could be addressed. Applied Materials was motivated by the fact that the system would not only benefit the company�s own facility: the system would potentially offer added value to its equipment customers.

In late 1998 Applied Materials opened its Equipment and Process Integration Center (EPIC), which houses all the equipment needed for customers to develop and test a completely integrated manufacturing process for building copper wiring on chips before actually installing the tools in their facilities. Because the EPIC facility contains all of Applied Materials� copper-based technologies, its waste stream is chemically similar to that of a fully operational fabrication facility (fab) manufacturing copper-based chips. In addition to the water treatment issues that the company wanted to address, EPIC also provided an opportunity to design and demonstrate a solution to the copper waste stream issue.

After lengthy design reviews, Applied Materials decided to install a closed-loop, zero-discharge waste-abatement system, illustrated below, which would purify the water used in the wet processing tools, separate the copper, and provide recycled, deionized (DI) water back into the facility�s DI water loop. The closed-loop system uses ultrafiltration for slurry separation followed by ion exchange to remove copper and other impurities from the wastewater streams. It then returns the water back to the facility as clean water feedstock for the process DI system.

Typically, the ultrapure water required for the system is generated from city water by a primary DI water system followed by an ion-exchange polish system. The goal of the copper removal system at Applied Materials is to recycle the water from the above processes and minimize the demand on the primary DI system.

The diagram shows that dionized water is used in the copper metal polishing (CMP), electroplating (ECP), and wet sink processes. Wastewater from the CMP process is then directed to an ultrafiltration system for solids removal. The wastewater from the ECP and wet sink processes is directed to the ion exchange system, where it is combined with the suspended solids-free effluent from the ultrafiltration system and deionized. The DI water is sent to the polishing ion exchange system and reused. The minimized regenerant waste from the ion exchange system is evaporated and the solid waste is sent to a recycling facility.

The integrated system was designed and installed by Hydromatix, a California company. A patent minimizing liquid waste generation from the ion exchange copper separation technology is held by Hydromatix. The fully automated ultrafiltration system was supplied by Pall Corporation.

Using the system described, copper-bearing aqueous solutions, primarily from CMP, ECP, and wet cleaning technologies, are recycled into DI water and returned to the copper facility for reuse. The only water consumed by the factory is small amounts of make-up water to replace the volume lost to evaporation. The only waste products that leave the system are highly concentrated, small-volume solids that are sent to appropriate disposal facilities.

At EPIC, the goal was to move toward zero discharge at the lowest possible cost. The benefits of a zero discharge system include both environmental and economic and business concerns.

The environmental benefits of a closed loop water system include:

• Substantially reduced water requirements. This is particularly beneficial in arid areas or those that experience water shortages, but is of value anywhere, because it means that less water is diverted from municipal supplies for the chip-making facility.

• Zero discharge. This alleviates the environmental risks and challenges of water treatment. Removing the potential for heavy metal contamination of water supplies is an obvious advantage. Lowering the demand on energy- and resource-intensive waste treatment processes is also a significant benefit.

• Other factors. A number of environmental and ecological problems are associated with industrial water use, even with proper water treatment facilities. These include such local disturbances as elevated temperatures in streams and rivers.

The economic and business benefits of the type of closed-loop system that Applied Materials installed are also considerable. They include:

• Recycles DI water. By putting DI water back into the copper system, the expense of and infrastructure needs for an ultra-pure water source are diminished.

• Avoids water and sewer costs. These can be particularly high in Asia and Europe. Such cost avoidance can mean that the zero discharge system is considerably less expensive over time than continuing to treat and discharge water (see chart below.)

• Avoids regulatory procedures. The closed loop system requires little or no regulation.

• Alleviates risk. As a more environmentally sound method, the process lessens the likelihood of liability claims and so on. Rather than producing a sludge with low metal content, which needs to be sent to a hazardous waste facility, the by-product of the system is a solid high in metal content that can be sent to a metal recycler without liability.

Notes: ZD is zero discharge. T&D is treat and discharge. The daily cost bar includes the average daily cost of capital depreciation for equipment. The additional capital investment for zero discharge is $200K (20 GPM) so the zero discharge payback period for Europe and Asia is ~500 days.

This chart demonstrates the cost differences between a zero discharge system and conventional treat and discharge methods. It compares the costs of water use and treatment in three regions (the United States, Europe, and Asia) for both zero discharge and treat and discharge systems. The capital costs are represented in thousands and are higher for the zero discharge systems than for treat and discharge systems. The operating costs (the second bar in each example) are fairly consistent across both regions and system type. Note that no water/sewer costs occur in the zero discharge examples, whereas these costs are significant in the treat and discharge cases, particularly in Europe and Asia. Capital costs are included in the daily cost totals on a depreciated capital cost per day basis. The daily cost figures, therefore, are a sum of the daily depreciated capital cost, along with daily operating and water and sewer costs.

The chart shows that the zero discharge system is cost effective, even though it has higher up-front capital costs. This can be seen most clearly by comparing the daily cost columns within each region. It is particularly true in Europe and Asia, where higher water and sewer costs make treat and discharge systems extremely expensive. For example, the daily cost figures (the fourth bar in each example) for the U.S. zero discharge system and the U.S. treat and discharge system are about the same. This is because the higher capital costs (the first bar) of the zero discharge system are offset by the water and sewer costs (the third bar) of the treat and discharge system. In Asia, on the other hand, the daily cost for the zero discharge system is significantly lower than for the treat and discharge system. This is because of the high cost of water and sewers in the Asian treat and discharge example. Daily treat and discharge costs in Europe and Asia are nearly twice the total cost of the zero discharge system.

THE RESULTS

The pilot system at EPIC commenced operations in May 1999. The team working with the system is making minor adjustments to optimize the process and its performance. Performance data will be available sometime in summer 1999, when the system is fully operational.

According to John Egermeier, director of operations, PSI Division at Applied Materials, "Our results to date indicate that with minor modifications, the EPIC copper abatement system should meet our performance goals for copper removal and recycled water quality."

Because Applied Materials� system is still in the commissioning phase, the company has not yet decided how it will make the technology available to its customers. Nevertheless, the example demonstrates the fact that equipment suppliers are going beyond just selling a process tool; rather, their product�s value can be dramatically enhanced if it is available with associated environmental control technology. Rather than waiting for its customers to battle with the environmental, economic, and regulatory issues associated with its products, Applied Materials proactively took steps to demonstrate how these concerns could be alleviated. This indicates the increased importance of life-cycle product issues and represents a significant step toward early intervention on issues of concern. Combined with the fact that the story highlights a promising new clean technology and a situation in which a supplier is being proactive rather than reactive to these issues, it is an exciting convergence and a hopeful indicator of current trends.

COMPANY INFORMATION

Applied Materials is the world�s largest supplier of wafer fabrication systems and services to the global semiconductor industry. In 1998 revenues were $4 billion, and the company employed 12,000 people in fourteen countries. Corporate headquarters are in Santa Clara, California, USA; research and development and manufacturing centers are located in the United States, Israel, Europe and Japan; and technology centers are located in South Korea and Taiwan.

CONTACT INFORMATION

Pall Corporation�s web site is http://www.pall.com.