As “lights out” scenarios increase, standards and best practices are still needed for safe gas and chemical remediation during fab decommissioning

By Arnold R. Canales

In response to current trends within the semiconductor industry, such as poor market acceptance, the lack of new consumer devices and the transition to restrictive technology node shifts in geometry and wafer size,¹ many facility owners are realizing the need to close existing fabs.

As this situation has been thrust upon it, the semiconductor industry is responding to the requirements for the decommissioning of existing manufacturing facilities, known in the industry as “End of Life” or “Lights-Out” scenarios. The management of decommissioning, decontaminating and the demolition (3D) of the specialty systems, such as gases and chemicals, is an important area of the process that requires intense evaluation.

In the realm of these specialty systems, there remains an industry-wide need to determine and discuss the practices, guidelines and pitfalls encountered from the decontamination and de-installation aspects of the decommissioning process as it pertains to existing Hazardous Production Materials (HPMs) systems and subsystems.

Don't overlook the HPM plan

From 1991 through December 2002, some 229 fabrication facilities were decommissioned. Of these, 50 percent were shut from 1999 through the end of 2002.²

Facilities have been closed utilizing both internal and external resources, and many concerns have been raised and documented in Decommissioning Task Force Report (Draft), July 2003, which was composed for the SEMI Environmental Health & Safety Standards Committee. While the report addresses challenges and recommendations for the decommissioning of tools and the facility, little thought was given to associated equipment, such as gas cabinets, valve manifold boxes (VMBs), chemical distribution units (CDUs) and gas and chemical distribution systems.

For example, owners have many assets, such as the production tools or manufacturing tool lines, that are being relocated to Asia or other viable locations. Many associated pieces of equipment will also need to be relocated with the manufacturing tools or tool lines.

According to Tim Burrows of Air Products and Chemicals Inc. (APCI), many wafer manufacturers have a “slash and burn” mentality when it comes to the removal of the associated equipment during a decommissioning effort. “Owners often have trouble realizing that when they have decommissioned a system incorrectly, and relocate and re-start the equipment…that causes more money to be spent to fully recover,” says Burrows.

The loss of the asset, and/or the cost to refurbish the equipment, such as gas panels, gas cabinets, and chemical distribution units, costs third-party equipment buyers and new equipment owners millions of dollars.

HPM procedures, processes, /closure

3D issues are most challenging when they're boiled down to HPM distribution systems. The worst-case scenario, and an area of high concern for HPM, is the conversion to a “brownfield site”—or, essentially, returning the property to “bare dirt.”

Solid contamination hazards—arsenic, mercury or lead—must be removed and eliminated in an environmentally safe manner. When dealing with decommissioning and demolition of process piping and distribution systems that contain highly toxic and pyrophoric gases—Diborane (B₂H₆), Arsine (AsH₃) or Phosphine (PH₃)—it's critical that there be tightly managed controls over the methodologies used to perform these activities. This is to ensure that the methodologies are done safely and with a compassionate eye on the environment.

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According to APCI's Dave Jones, safety and environmental requirements need to be the predominant factor in the 3D process. “It is felt by many industry leaders that safety and environmental concerns in the decommissioning of HPM systems often take a back seat to schedule and financial pressures,” says Jones. “The true financial burden of managing the safety and environmental issues in properly planning and executing a 3D project are often overlooked or underestimated by the exiting owners.”

Many procedures and processes have been developed for the design, installation and operations of HPM management—by either the owners or the industry suppliers. This includes the handling and product change-out for gases and chemicals within the facility and supporting infrastructure.

But many industry service providers do not clearly understand the liability, risk and hazards involved in decommissioning, and especially the interrelationships of other systems with the HPMs. Pre-planning and execution is paramount to the success of the decommissioning for HPM equipment and systems.

Development of a Closure Plan will address most of the issues (such as end-state conditions) while dealing with the regulatory issues of the particular area. In addition, the plan will determine the disposition of the assets (tools), which could include sale or re-use, storage, scrap or salvage, donation or disposal.

Before the service provider or contractor is engaged to provide decommissioning services, a concise Scope of Work, together with a detailed execution strategy, will need to be developed to assess risk and liability and identify the actual work to be performed during this phase of the project.

This is where many people fail to clearly delineate the requirements and expectations of the project. Failure is inevitable if pre-planning, Scope of Work and execution of the Closure Plan are not properly understood and performed.

Assuming the risks

Fab owners are struggling with the remediation of HPM systems and subsystems because the industry is still trying to define just how clean the tools need to be when they are decommissioned, removed for repackaging and transported to new locations worldwide. The same holds true for support equipment and materials. Whether the 3D process is performed by the owner or a service provider, a level of risk exists and must be recognized.

There is, however, a gap in the standardization of procedures to purge and clean specialty gas equipment or gas process lines. Some service providers, such as gas or chemical manufacturers, have comprehensive procedures or practices to identify hazards, provide contaminate characterization and decontaminate equipment and piping materials to render them safe for storage, salvage or disposal.

Technicians have been performing this type of work for decades and have been following site-specific guidelines and procedures, ensuring that decommissioning and decontamination are performed correctly before the gas cabinets, panels, CDUs and piping are removed or changed-out safely and properly. This is especially true where minor bay renovations take place in an operating facility.

But with complete facilities scheduled to be taken down, the number of risks increases due to the shear number of systems to be removed. The risks are especially high during the initial line-break at the source—at the gas cabinets or from the source at the tool.

When the line-breaks occur for hazardous gases or chemicals, such as silane (SiH₄) or hydrogen fluoride (HF) the risk increases (see Figure 1, page xx). In addition to the procedures and the checklist that must be used, appropriate use of personal protection equipment (PPE) must also be evaluated for proper safety practices. Once again, this is an imperative safety requirement that must be evaluated and followed to prevent injury to personnel.

During decontamination phases that involve HPMs, the industry needs to identify best-known methods (BKMs) for the systems that will be removed and transported with the manufacturing tools. Common questions regarding purging include:

• Length of time required to purge gas cabinets and process lines from the source to the tool?
• At what pressure should the equipment and the piping systems be purged?
• How many purge cycles should be performed?

The lack of industry guidelines, practices and procedures were annotated within the recent SEMI Decommissioning Task Force daft; however, concise industry standards are not available that identify industry minimum requirements to answer the questions posed above.

Understanding the associated risks, using the appropriate devices when decontaminating and providing supporting papers for the equipment all need to be part of the 3D procedure.

Liquid chemical issues

Where use of liquid chemicals is concerned, the issues pertaining to the decontamination and disposal of lines and devices are less imposing. In this case, the distribution piping from the bulk chemical distribution units can be rinsed with water and routed to the acid waste neutralization (AWN) system.

Residual rinse water tested will need to have the pH neutral—somewhere between a pH of 6.5 to 7.5. At this point, the piping can be removed without significant harm to the facility or personnel. Decontamination of CDUs offers fewer risks than the equipment as far as decontamination of specially gases is concerned.

In addition to the lack of specific guidelines or practices, as well as lack of standardization for the use of terms, definitions and training are also considerations for the industry to undertake. Inconsistent terms are used for many of the aspects of the fab 3D process. Uses of current terms vary widely within regions, companies and manufacturers.

Within this newly emerging sector, training of qualified contractors and technicians for the proper execution of 3D in HPM services will be a key to success. Without qualifying or certifying individuals or companies, this part of the industry remains unregulated and puts individuals and companies at risk, both for safety and environmental concerns.

The semiconductor industry must also recognize the potential for short- and long-term airborne exposures to personnel, as well as the effects on communities when it comes to airborne exposure or transfer of contaminates through ground water.

Many highly qualified and talented people already work to assist in the development of gas and chemical remediation within this emerging sector. Such organizations as SEMI and ASU CREATE³ will continue their quest to develop these standards, define the terms, and document the general requirements to decommission, decontaminate and demolish facilities and systems. As for the remediation of gas and chemical systems, gas supply giants must continue to develop concise and comprehensive procedures to address the purging of gas systems and supporting equipment—and this work must find its way into the industry standards.

While the future appears to be bleak for the semiconductor industry, existing service providers can help manufacturing owners determine how best to address the systems within their facilities and move forward with a safe and appropriate 3D plan.

ARNOLD R. CANALES is a member of Kinetics Systems Inc., is involved in both the design and construction phases within the industry and is a past board member and current technical advisor of ASU-CREATE. He can be reached at: [email protected].