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SEMI F98-0305 © SEMI 2005 2 4.2 Other Standards “Strategies for Water Reuse Reduction i n Semiconduct or Manufact uring”, Tec hnology Transfe r 97013232A-ENG 1 2004 International Technol ogy Roadmap for Semiconduct ors 1…
SEMI F98-0305 © SEMI 2005 1
SEMI F98-0305
GUIDE FOR TREATMENT OF REUSE WATER IN SEMICONDUCTOR
PROCESSING
This guide was technically approved by the Global Facilities Committee and is the direct responsibility of the
North American Facilities Committee. Current edition approved by the North American Regional Standards
Committee on December 10, 2004. Initially available at www.semi.org February 2005; to be published
March 2005.
1 Purpose
1.1 This guide establishes definitional requirements for industrial water systems that reuse water in a semiconductor
manufacturing facility. It is intended to establish a common basis for developing detailed specifications in
subsequent documents concerning design, performance, optimization, and monitoring of such systems.
1.2 This document may be used by users and suppliers as a basis for developing site-specific specifications and
performance criteria.
2 Scope
2.1 This guide applies to water systems designed for reuse of water including reclaim and recycle, used in
semiconductor manufacturing facilities, supplying water to a variety of uses. Such uses include directing waters to
the front end of a UPW system, to cooling systems, scrubbers, thermal processes, and to irrigation systems,
depending on the quality of the water.
2.2 This guide can be used to understand the design elements and functionality of water systems that support reuse
of water. Although such systems can be retrofitted into existing manufacturing factories, there is a broader range of
opportunities available in new facilities that can be designed with water saving applications in mind.
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish appropriate safety and health practices and determine the
applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 This guide does not define the actual specifications generally negotiated between the user and the manufacturer
of the reclaim or recycle system.
3.2 This guide does not address the methodology for optimizing the reuse of spent rinse waters.
3.3 This guide does not address the frequency or scope of ongoing maintenance for reuse water systems including
change-out of resin beds and replacement of filters.
3.4 This guide does not describe the broad range of possible reuse opportunities and the associated water quality
required for each.
3.5 This guide does not intend to cover any of the important safety considerations that relate to the proper
installation, operation, or maintenance of a reuse water system.
4 Referenced Standards
4.1 SEMI Standards
SEMI E49 — Guide for High Purity and Ultrahigh Purity Piping Performance, Subassemblies, and Final Assemblies
SEMI F63 — Guide for Ultrapure Water System Used in Semiconductor Processing
SEMI S2 — Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment
SEMI F98-0305 © SEMI 2005 2
4.2 Other Standards
“Strategies for Water Reuse Reduction in Semiconductor Manufacturing”, Technology Transfer 97013232A-ENG
1
2004 International Technology Roadmap for Semiconductors
1
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 Acronyms and Abbreviations
5.1.1 UPW — Ultrapure Water
5.2 Definitions
5.2.1 spent water — any discharge water that is consumed or processed and is ready to be discharged to drain.
5.2.2 UPW reclaim — the reuse of spent water as feed water for a process different from the one that discharged it,
e.g. RO reject fed into cooling towers.
5.2.3 UPW recycle — the reuse of spent water as feed water for the same process that discharged it (Point-of-
Discharge (POD) recycling), or the plant UPW system.
5.2.4 UPW reuse — the secondary use of spent water.
6 Design Components and Elements
6.1 Collection of Waste Streams — The most common collection system includes fab-wide gravity collection
piping using PVC or PVDF transfer piping and associated pipe racks and tunnels to the collection tanks. Proper
venting is also critical to correct operation. The system may also include a reclaim pit, pumps, tanks, and controls.
Separate holding tanks are used for each grade of water or type of waste stream so that routing of waste and types of
treatment can be matched to specific needs (see Figure 1).
6.1.1 A key consideration for the design of a water reuse system is the ability to separate different grades of water
and collect each type of effluent. Typical types of segregation include: segregation of clean rinse water from acid
waste; separation of waste streams that contain organics, (e.g. from IPA drying); and isolation of waste streams that
require specific treatment such as for hydrofluoric acid, CMP processing, copper solutions, or phosphoric acid.
6.1.2 A recent initiative by semiconductor fabs encourages tool manufacturers to include multiple drain lines within
the tool so that waste streams can be easily segregated. Diverter valves can be used to segregate chemicals and are
also useful when organics exceed recommended levels. Tool manufacturers can also incorporate plumbing and
treatment modules for returning spent water discharged from a tool as feed water for that tool (Point of Discharge
[POD] recycling). Purchasing tools with recycle hardware already built-in eliminates the need for users to design
and install customized water reuse systems unique to their site.
6.2 Treatment of Waste Streams — In addition to choosing the most effective and technically sound design choices,
other considerations for treatment choices include easy access to all major components for operations and
maintenance, availability of consumables and spare parts, and a high level of automation and reliability. There are
several choices related to treatment choices:
6.2.1 TOC (total oxidizable carbon) destruction by UV is commonly used for removal of organics found in reclaim
waters and is sometimes combined with ozone or hydrogen peroxide.
6.2.2 Activated Carbon or other adsorbents (e.g. GAC) are used for removal of organics and decomposed
hydrogen peroxide, and is a common type of treatment in recycle water systems.
6.2.3 Electrodeionization (EDI) enables ion exchange reactions to be carried out continuously, without off-line
regeneration, by introducing a dc electric field across the resin bed. This electric filed is oriented transverse to the
direction of water flow through the ion exchange column. Under the influence of the applied electric field, impurity
ions, chemically captured by the ion exchange reactions, drift from resin bead to neighboring resin bead and
1 International SEMATECH, 2706 Montopolis Drive, Austin, TX 78741, USA, Website: www.sematech.org
SEMI F98-0305 © SEMI 2005 3
ultimately through a semipermeable membrane that isolates the feed water channel from adjacent circulating water
flows (“concentrate channels”) that sweep away the impurities entering through the semipermeable membranes.
This continuous regeneration action eliminates the need to take ion exchange columns off-line for resin regeneration
and also eliminates the need for storing regeneration chemicals on site.
6.2.4 Reverse Osmosis Membrane Treatment provides extremely high rejection of dissolved ions (charged atoms
and molecules), organic (carbon containing) compounds, silica (silicon containing) compounds, and virtually
complete rejection of suspended contaminants, but will not reject dissolved gases and volatile organic compounds as
well. For reclaim systems, special types of high rejection or low fouling RO membranes may be selected.
6.2.5 Often RO Systems are combined with ion exchange processes either with the purpose of increasing the
recovery rate of the RO or by combining the high efficiency of a membrane process with the lower fouling potential
of ion exchange resins, e.g. Weakly Acidic Cation Resin (WAC) is designed to remove Ca and Mg ions in the
water. The system design should reflect that most of the contaminants of rinse waters are anionic in nature and may
foul RO membranes, but recycling water may be mixed with other water qualities and may therefore contain
hardness, which can react with the Fluoride of the recycling water.
6.2.6 Biological processes are used to treat water with higher organic contents. They can be either fixed bed
systems or fluidized bed systems. These processes typically require both upstream and downstream processes, such
as neutralization, and maintaining a stable feed concentration for the biological process upstream and removal of
bacteria downstream. The operation of such systems is quite sensitive, but most of the organics used in
semiconductor manufacturing can be treated by such systems, including TMAH and chemicals used for lithography
and stripping.
6.2.7 Other Treatment — Includes microfiltration, ultrafiltration, and other types of water treatment typically used
to protect RO Membranes. Pretreatment equipment may include media filtration (bulk suspended solids removal),
1–5 micron cartridge filtration (polishing step for suspended solids removal), sodium-cycle cation exchange
(softening, to remove scale-forming cations), acid injection (to minimize cellulose acetate membrane damage and/or
to control carbonate scales), scale inhibitor injection (to control scaling), and sulfite ion injection (to remove
oxidizing agents).
6.3 Monitoring — TOC, pH, conductivity, and temperature are typical parameters that can be monitored on-line
and tracked over time to optimize performance. The set points and level of monitoring depends on the chemistries
being used and what the ionic and organic loads are in each waste stream after the application and the treatment. To
ensure the accuracy of certain on-line measurements, a minimum residence time and volume of sample is required
and can be provided through the use of a buffer station and separate sample tanks. Other parameters such as fluoride
levels, specific organics, and oxidants from undeveloped ammonia must be measured in the laboratory.
7 Grades of Water Effluent
7.1 Rinse Water — The second and third rinses from wafer cleaning processes are sufficiently high quality to be
reused without further treatment either for make-up water in a UPW system, or directly for use in a lower grade
application such as CMP cleaning.
7.2 Non-treated Reclaim Water — Is a lower grade of water with possible applications including fab air pollution
abatement scrubbers, fab point-of-use hazardous gas burn boxes, and drain flushing for CMP drains.
8 Special Issues
8.1 Difficulty of Identifying and Treating Organics — It is difficult to evaluate rinse waters after solvent use. Real
time, on-line instruments are not available to easily quantify and identify the complete composition of the organic
molecules for proper segregation. In addition, treatment of waste water containing organics is more difficult in
some cases, depending on the organic molecules being removed or converted.
8.2 Managing Excursions — Excursions in reuse water quality can occur due to various reasons such as human
error in operating non-automated manufacturing equipment.
8.2.1
It is important to detect and redirect such water before it can contaminate the system for which it directed for
reuse or possibly even damage the treatment equipment. Excursions from organics are particularly difficult because
they cannot be detected in real time. Two methods have been used to compensate for this delay: locate the