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SEMI DRAFT Document 4792
NEW STANDARD: GUIDE FOR HIGH PURITY WATER USED IN
PHOTOVOLTAIC CELL PROCESSING
1 Purpose
1.1 This guide is provided for multiple purposes. It may be used as a basis for establishing performance criteria for
purchases of new High Purity Water (HPW) equipment. It may also be used internally by facility engineers to set
process control parameters for the operation of their HPW systems. This guide may be used by process engineers to
establish reasonable expectations about the quality of the HPW being supplied to them by facilities.
NOTE 1: These suggested guidelines are published as technical information and are intended for informational purposes only.
2 Scope
2.1 Water is used extensively in the production of photovoltaic cells and association manufacturing for all wet
processing steps such as the rinsing of substrate wafers and panels. HPW is typically produced for this purpose using
Reverse Osmosis/Deionized resin bed technologies. The quality of the water impacts device yield. Requirements
for higher purity water may increase with changes in the photovoltaic cell over time.
2.2 The guidelines are targeted for HPW produced for photovoltaic manufacturing.
2.3 The guidelines consider both general photovoltaic manufacturing facilities as well as critical manufacturing
tools.
2.4 Location for water quality specification is defined at Point-of-Use (POU), which is a Point of Connection (POC)
of the manufacturing tool on the HPW distribution lateral.
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 is not intended to set an absolute performance requirement for a HPW system. Performance
requirements should be determined based on the sensitivity of the manufacturing process to the purity of the water,
the sensitivity of the instrumentation, and the costs associated with installation, maintenance, and monitoring the
water system parameters.
3.2 This set of guidelines has been established from a variety of sources and inputs including; (1) an industry survey
that SEMI PV Group provided to members of its standards activities; (2) typical HPW levels from a large selection
of photovoltaic HPW systems, as measured by independent laboratories that test high purity water for the
photovoltaic industry; (3) specifications from water system equipment manufacturers; and (4) input from producers
and users of HPW during SEMI PV Group standards committee meetings and through the balloting process.
However, it is up to each individual owner of a HPW system to set specifications for the purity of its water based on
the owner’s needs and available resources.
3.3 ASTM D5127 is considered in setting specifications for the purity of reagent grade water needed in a laboratory
for analytical testing of photovoltaic materials and process chemicals.
3.4 The guidelines are based on current state-of-the-art PV manufacturing and do not take into account enabling
future technologies.
3.5 The quality of the data measured will depend on which testing method and calibration techniques are used.
Consequently, trends observed in the values may be as meaningful as absolute values.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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LETTER (YELLOW) BALLOT
Document Number: 4792
Date: 2/16/2016
Semiconductor Equipment and Materials International
3081 Zanker Road
San Jose, CA 95134-2127
Phone:408.943.6900 Fax: 408.943.7943
DRAFT
4 Referenced Standards and Documents
4.1 SEMI Standard
SEMI C1 — Guide for the Analysis of Liquid Chemicals
4.2 ASTM Standards1
ASTM D859 — Standard Test Method for Silica in Water
ASTM D2791 — Standard Test Method for On-line Determination of Sodium in Water
ASTM D4327 — Standard Test Method for Anions in Water by Chemically Suppressed Ion Chromatography
ASTM D5127 — Standard Guide for Ultra Pure Water Used in the Electronics and Semiconductor Industry
ASTM D5173 — Standard Test Method for On-Line Monitoring of Carbon Compounds in Water by Chemical
Oxidation, by UV Light Oxidation, by Both, or by High Temperature Combustion Followed by Gas Phase NDIR or
by Electrolytic Conductivity
ASTM D5391 — Standard Test Method for Electrical Conductivity and Resistivity of a Flowing High Purity Water
Sample
ASTM D6317 — Standard Test Method for Low Level Determination of Total Carbon, Inorganic Carbon and
Organic Carbon in Water by Ultraviolet, Persulfate Oxidation, and Membrane Conductivity Detection
ASTM D7126 — Standard Test Method for On-Line Colorimetric Measurement of Silica
ASTM F1094 — Test Method for Microbiological Monitoring of Water Used for Processing Electron and
Microelectronic Devices by Direct- Pressure Tap Sampling Valve and by the Pre-sterilized Plastic Bag Method
4.3 SEMATECH document2
Technology Transfer #92010949B SEMATECH Provisional Test Method for Determining Particle Contribution and
Retention by UPW Distribution System Components Appendix 3. SEM Direct Count Method for Bacteria and
Particle Enumeration of Ultrapure Water Samples
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 Abbreviations and Acronyms
5.1.1 HPW — High Purity Water System
5.1.1.1 High Purity quality — quality of HPW required for higher sensitivity PV processes
5.1.1.2 Standard Purity quality — quality of HPW required for lower sensitivity PV processes
5.1.2 TOC — total organic carbon, also Total Oxidizable Carbon. Refers to organic compounds.
5.1.3 UPW — Ultrapure Water System
5.2 Definitions
5.2.1 DI (deionized) water — generally refers to water that has passed through a full-train ion exchange system or
RO water that has been polished by ion exchange.
5.2.2 High Purity Water System - a lower grade than UPW, due to lower requirements for dissolved gases, ions,
TOC, bacteria and particles. There are two quality choices to be chosen by end user depending on needs:
1 American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428-2959, USA. Telephone:
610.832.9585; Fax: 610.832.9555; http://www.astm.org
2 SEMATECH, 2706 Montopolis Drive, Austin, TX 78741, http://www.sematech.org
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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LETTER (YELLOW) BALLOT
Document Number: 4792
Date: 2/16/2016
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Phone:408.943.6900 Fax: 408.943.7943
DRAFT
5.2.2.1 High Purity quality — quality of HPW required for higher sensitivity PV processes
5.2.2.2 Standard Purity quality — quality of HPW required for lower sensitivity PV processes
5.2.3 Raw water — any untreated natural water like river water, lake water, ground water, or seawater. May also
refer to the treated feed water that enters a plant from a municipal drinking water source or other source.
5.2.4 Reverse osmosis (RO) — a filtration technology that utilizes a semi-permeable membrane to remove
essentially all suspended solids and the vast majority of all dissolved solids. Generally refers to water (permeate)
that has passed through a reverse osmosis (RO) membrane.
5.2.5 Treated water — water that has passed through water treatment equipment or received chemical injections or
both in order to modify the solids content of the water.
5.2.6 Ultrapure Water System - consisting of multiple components including a Reverse Osmosis (RO) and a
Deionization (DI) process. UPW is a higher purity of water that exceeds all the requirements of HPW and is
produced by a semiconductor water treatment system, which is sent to the end users for use in manufacturing.
5.2.7
6 Units
6.1 Parts per billion (ppb) is equivalent to ng/mL or μg/L where the density of water at 1 g/mL is assumed.
6.2 Parts per million (ppm) is equivalent to mg/L where the density of water at 1 g/mL is assumed.
6.3 Micrometer is a unit of length equal to one millionth of a meter, or one thousandth of a millimeter.
6.4 Colony Forming Units (CFU) is a measurement of bacteria organisms as referred to in ASTM F1094.
7 Description of Parameter Tests
NOTE 2: Since SEMI Guidelines do not require analytical data or methods to support them, the recommendations of specific
analytical methods are only for informational purposes. Alternative methods may also be applicable (see SEMI C1 for analytical
validation methodology).
NOTE 3: Sampling methods and contamination control are of paramount importance when attempting to measure the listed
parameters at the levels specified. Sample containers and sampling techniques should be appropriate to avoid false positives at
low levels.
7.1 Resistivity (megohm-centimeters or Mohm–cm)
7.1.1 Resistivity (conductivity) is measured accurately with only on-line instrumentation. 18.25 MOhm-cm is the
theoretical upper limit for pure water at 25°C.
7.2 Total Organic Carbon (TOC) (ppb)
7.2.1 Involves oxidation of organic materials and detection of carbon dioxide produced by the reaction, as measured
by conductivity or infrared photometry and reported as carbon (C).
7.3 Particulate Matter (Particles/L)
7.3.1 On-line methods using laser technology are recommended for accurate trend analysis.
7.3.2 As an alternative, collection of particles on a track etch membrane, followed by counting with Scanning
Electron Microscopy can be used, as described in Technology Transfer #92010949B.
NOTE 4: This method will not provide a real time analysis. Therefore, the frequency of sample collection might fail to capture
excursion events.
7.4 Bacteria (CFU/L)
7.4.1 Triplicate samples are cultured based on the ASTM F1094 using a minimum sample size of 1L.
7.5 Silica
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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LETTER (YELLOW) BALLOT
Document Number: 4792
Date: 2/16/2016
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3081 Zanker Road
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Phone:408.943.6900 Fax: 408.943.7943
DRAFT
7.5.1 Total Silica (ppb) may be measured by Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS),
Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) or High Resolution Inductively Coupled
Plasma Mass Spectroscopy (ICP-MS).
7.5.2 Dissolved Silica (ppb as SiO2) may be measured by heteropoly blue photometry or by Ion Chromatography.
7.6 Ions and Metals (ppb)
7.6.1 Many anions and cations, including ammonium, bromide, chloride, fluoride, nitrate, nitrite, phosphate, and
sulfate, may be determined using Ion Chromatography.
7.6.2 The 20 elements included in this guide are listed in Table 1.
NOTE: Up to 68 elements, including the 20 of interest may be determined by GFAAS, ICP-AES, or ICP-MS.
8 Parameters and Typical Concentrations
8.1 Table 1 lists each parameter with its range of performance.
Table 1 Parameters and Range of Performance
PARAMETER
RANGE OF PERFORMANCE
High Purity
Standard Purity
Resistivity on-line @ 25°C (Mohm–cm)
>17.5
>10
TOC on-line (ppb)
<20
<200
Dissolved Oxygen on-line (ppb)
NA
NA
On-line Particles/L (micron range)
0.1–0.2
<1000
NA
0.2–0.3
<100
<10,000
0.3–0.5
<10
<1000
>0.5
<1
<100
Bacteria (CFU/L)
<10
<100
<20
<50
<20
<50
Ammonium
<1
<10
Bromide
<1
<10
Chloride
<1
<10
Fluoride
<1
<10
Nitrate
<1
<10
Nitrite
<1
<10
Phosphate
<1
Sulfate
<1
Aluminum
<1
Antimony
<1
Arsenic
<1
Barium
<1
Cadmium
<1
Calcium
<1
Chromium
<1
<10
<10
<10
<10
<10
<10
<10
<10
<10
Silica
Silica — total (ppb)
Silica — dissolved (ppb as SiO2
)#1
Ions & Metals (ppb)
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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Copper
<1
Iron
<1
Lead
<1
Lithium
<1
Magnesium
<1
Manganese
<1
Nickel
<1
Potassium
<1
Sodium
<1
Tin
<1
Titanium
<1
Vanadium
<1
Zinc
<1
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
#1 Total Si is defined as the leading specification parameter. Typically dissolved Si presents the majority of the total Si
in the defined specification range. Measuring dissolved Si may be chosen for convenience or for cost optimization.
NOTICE: SEMI makes no warranties or representations as to the suitability of the standard(s) set forth herein for
any particular application. The determination of the suitability of the standard(s) is solely the responsibility of the
user. Users are cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other
relevant literature respecting any materials or equipment mentioned herein. These standards are subject to change
without notice.
By publication of this standard, Semiconductor Equipment and Materials International (SEMI) takes no position
respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this
standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and
the risk of infringement of such rights are entirely their own responsibility.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
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Document Number: 4792
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