By Michael Fitzpatrick, Chair of IEST contamination-control working groups 012 and 028
IEST recommended practice IEST-RP-CC012.1, Considerations in Cleanroom Design, has recently been revised and is scheduled for publication later this year. The original document has long been the primary standard for those involved in the design, construction and ownership of cleanrooms. It has frequently served as an essential first stop for users considering the use of cleanrooms.
The official scope of the document is defined as follows: This Recommended Practice (RP) makes recommendations regarding factors to consider in the design of cleanroom facilities. This discussion is limited to those environmental conditions that typically confront cleanroom designers and users.
The revised document, which will be designated as IEST-RP-CC012.2, consists of two primary sections, as does the original: planning, and design requirements. The new document contains significant revisions and updates to the original RP and includes several new topics.
New material includes a discussion of fire protection, air filtration, airborne molecular contamination (AMC), factory automation, facility monitoring, and decommissioning. The original topics on minienvironments, electrical power, and cleanroom construction protocol have been significantly expanded. The sections on noise, vibration, and contamination control have been updated to include not only current, state-of-the-art criteria, but also to anticipate future criteria.
A discussion of special requirements such as maintenance, redundancy, alterations, flexibility, ergonomics, and energy efficiency has been added to the planning section.
IEST-RP-CC012.2 will be of interest to owners, users, designers and builders of cleanrooms serving all industries.
Let’s take a closer look at the new document…
Planning
The planning section is aimed at current users of cleanrooms and at those considering the use of cleanrooms. It leads the user through a logical process that identifies the requirements of the project and provides a methodology to achieve those requirements. Employing the methodology developed by W. Pena in the 1980s, this section provides a source of information not found in other documents. It has often been observed of the original IEST-RP-CC012.1 that if one were to take the topic headings alone and eliminate all subsequent discussion, one would be left with a comprehensive checklist for the design of a cleanroom as found in Pena’s original work. The new document includes all of the original material as well as several new sections.
The planning section begins with a review of the manufacturing process and develops a utility matrix that is used to determine the manufacturing layout. The utility matrix also serves to identify contamination control, life safety and environmental issues associated with the manufacturing process.
This section offers contamination control guidelines that categorize the various types of contaminants and lists the methods commonly used to mitigate them. It includes a discussion of life safety and environmental issues, critical material flow, site selection criteria, security and access control, and government regulation.
IEST-RP-CC012.2 introduces some new topics to the planning section, including fire protection, special requirements, and energy efficiency. The special requirements portion is particularly useful since it covers issues that are frequently overlooked during the design process. These include maintainability, redundancy, and flexibility. Energy efficiency provides recommendations for reducing energy consumption and contains data from actual case studies.
Another new section covers alterations of existing facilities. It reviews the logistics involved in the remodeling of an existing cleanroom and the subsequent impact to operations.
Ergonomics, budget and schedule projections are also reviewed in the planning portion of the document.
Design requirements
While the planning portion of IEST-RP-CC012.2 helps to establish project requirements and develops the basis of design, the section on design requirements adds detail to the process. Here we find a discussion of the various facility systems and how they may best be incorporated into the final design. The section begins with a review of the types of airflow patterns found in cleanrooms-unidirectional, non-unidirectional, and mixed-and provides guidance as to the use of each. Architectural layout is discussed as it relates to maintaining the desired air-flow patterns.
The section covering airflow guidelines has also been updated and expanded and includes a new version of the recommended airflow velocity table. This table, regardless of the data contained in it, has always provoked considerable discussion. It is hoped that this new version will do the same. The air filtration section reviews the application of both in-line and terminal filters and lists appropriate testing criteria.
A central element of the original document, HVAC system configuration, remains in the revised document and provides the jumping-off point for the discussions of temperature, humidity, pressure, and exhaust. This section describes exhaust-determined systems, cooling-determined systems and cleanliness classification-determined systems, and provides the user with the information required to determine which system best suits his or her needs.
Temperature, humidity, pressure, and exhaust each offer guidelines, certification requirements and design parameters that will guide the user in specifying HVAC criteria that meet the specific needs of the project.
A section that examines airborne molecular contamination (AMC) and the systems used to control this phenomenon has been added. It reviews the integration of AMC control with the HVAC systems so that required design elements might be incorporated
The noise and vibration sections have been updated to include current criteria and technology. Of particular interest is the introduction of two new vibration criteria curves, VC-F and VC-G. Although this new criteria is not expected to be widely used, it will be essential for certain applications such as nanotechnology.
The section on cleanroom electrical power has been considerably expanded to include the topics of redundancy, safety, emergency power and back-up power systems. Electrostatic interference and cleanroom lighting are also discussed.
The life safety section now includes a discussion of toxic-gas monitoring systems and leak detection.
Minienvironment technology has advanced considerably since the original publication of IEST-RP-CC012.1. Therefore, the section on minienvironments has been expanded significantly and focuses on the integration of minienvironments with the building systems. Material from IEST-RP-CC028.1 Minienvironments has been included to assist the user in determining what types and configurations of minienvironment might be appropriate for a specific use.
Many new and existing facilities incorporate automation systems in their designs. The facility integration and operational implications of these systems can be considerable. The factory automation section of IEST-RP-CC012.2 provides guidance in the use and integration of these systems.
Many modern cleanroom facilities include facility monitoring systems designed to provide real-time information regarding operational parameters. These may include temperature, pressure, humidity, and airborne particle levels. The new document describes these systems and offers guidance regarding the type of system to employ.
The aging or technical obsolesce of many facilities requires that they be demolished, a process known as decommissioning. This process can have severe economic, environmental and life safety implications. IEST-RP-CC012.2 provides guidance regarding decommissioning with relation to process, facility and building components.
Cleanroom construction protocol is recognized as an essential element of successful cleanroom projects. IEST-RP-CC012.2 reviews the planning, logistics, and procedures required to implement such a program. Perimeter isolation, controlled access, training, and continuous cleaning requirements are reviewed. The appendix of the RP includes a sample cleanroom construction protocol program suitable for use or modification by the user.
IEST RP 12.1 Considerations in Cleanroom Design has long been recognized as the primary tool for the planning and design of cleanrooms. Rather than providing cookbook solutions, it leads the user through the planning and design considerations and assists owners and designers in developing design criteria to meet specific needs. IEST-RP-CC012.2, while retaining much of the original material, expands on its predecessor, providing additional material and updating design criteria. The document is essential reading for those involved in the planning and design of cleanrooms.
Michael A. Fitzpatrick is vice president of McGill Cleanroom Systems and has participated in the design and construction of semiconductor facilities for more than twenty-seven years. A Senior Member of the Institute of Environmental Sciences and Technology, he is Chairman of WG-CC012, Considerations in Cleanroom Design, and WG-CC0028, Minienvironments. He has also served as a vice president of IEST. He can be reached via e-mail at [email protected].
About IEST: Founded in 1953, IEST is an international not-for-profit technical society of engineers, scientists and educators that serves its members and the industries they represent (simulating, testing, controlling, and teaching the environments of earth and space) through education and the development of recommended practices and standards. IEST is an ANSI-accredited standards-developing organization; Secretariat of ISO/TC 209, Cleanrooms and associated controlled environments; Administrator of the ANSI-accredited US TAG to ISO/TC 209; Administrator of the ANSI-accredited US TAG to ISO/TC 142, Cleaning equipment for air and other gases; and a founding member of the ANSI-accredited US TAG to ISO/TC 229, Nanotechnologies.