Background Statement for
SEMI Draft Document #4494
Revision to SEMI F15, with title change from: TEST METHOD FOR ENCLOSURES USING SULFUR HEXAFLUORIDE TRACER GAS AND GAS CHROMATOGRAPHY, to: TEST METHOD (SF6 TRACER GAS) FOR ENCLOSURES HAS BEEN MOVED TO SEMI S06
Note: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this document.
Note: Recipients of this document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, “patented technology” is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided.
Dear Colleagues,
This ballot proposes replacement of the current SEMI F15 with the draft document that follows this page. A copy of Appendix 2 of SEMI S06-0707 is provided for your reference, but is not subject to voting on this ballot.
The newly-published of SEMI S06-0707, EHS Guideline for Exhaust Ventilation of Semiconductor Manufacturing Equipment incorporates a tracer gas method for measuring the fugitive emissions from an enclosure. The method included therein is based on the method previously published in SEMI F15, but there were some substantive changes, including:
1)The removal of the default tracer gas release rate of 28.3 slm (1 cfm),
2)The removal of SF6 as the specified species to be used as the tracer gas, and
3)Permitting a choice of suitable analytical techniques for the air samples.
Throughout the S06 Rewrite project, it has been the intent of the Task Force to replace SEMI F15 with the method incorporated within the new S06. However, SEMI S02 refers to SEMI F15, so that withdrawal of F15 prior to revision of S02 would create a gap. A similar situation existed with the migration of electrical test methods from SEMI S09 to SEMI S22. Therefore, the Task Force hereby proposes a similar solution, the replacement of F15 with a document that points to the method in SEMI S06-0707.
This ballot will be discussed at the SEMI NA Standards Fall Meetings at San Diego, California, in the meeting of the SEMI S6 Task Force and the ballot is scheduled to be adjudicated in the meeting of the NA EHS Committee (scheduled to be 0800-1700 PT, Thursday, 01 November 2007).
The TF plans to hold teleconferences between the close of the voting period and the TF meeting. You are encouraged to join them to participate in the continuing development of this document. Please contact a TF co-leader, Robert Desrosiers r Eric Sklar <> for details.
If you reject or provide comments on this ballot, please send a soft copy of your responses directly to the TF co-leaders: and . (As this is a Technical Ballot, you must submit a formal response to SEMI.)
Thanks in advance for your participation,
Robert Desrosiers
Eric Sklar
Safety Checklist for SEMI Draft Document #4494
Title: Revision of SEMI F15
Developing/Revising Body
Name/Type: / S6 Rewrite TFTechnical Committee: / EHS
Region: / North America
Leadership
Position / Last / First / AffiliationCo-Leader / Sklar / Eric / Safety Guru, LLC
Co-Leader / Desrosiers / Robert / IBM
Documents, Conflicts, and Consideration
Safety related codes, standards, and practices used in developing the safety guideline, and the manner in which each item was considered by the technical committee
# and Title / Manner of ConsiderationSEMI S06 / Determined that the text of Appendix 2 of S06-0707 should replace F15.
Known inconsistencies between the safety guideline and any other safety related codes, standards, and practices cited in the safety guideline
# and Title / Inconsistency with This Safety GuidelineNone
Other conflicts with known codes, standards, and practices or with commonly accepted safety and health principles to the extent practical
# and Title / Nature of Conflict with This Safety GuidelineNone Known
Participants and Contributors
Last / First / AffiliationBarcik / Steve / HTDS
Crane / Lauren / Applied Materials
Funk / Rowland / Earth Tech
Giles / Andrew / GS3
Guild / Ed / IBM
Hamilton / Jeff / Applied Materials
Hayford / James / Semitool
Hom / Jeffrey / Underwriters Laboratory
Larsen / Sean / AMEC
Mills / Ken / GS3
O’Hehir / John / Applied Materials
Quizon / George / UL
Rehder / Alan / UL
Sklar / Eric / Safety Guru, LLC
The content requirements of this checklist are documented in Section 14.2 of the Regulations Governing SEMI Standards Committees.
Semiconductor Equipment and Materials International
3081 Zanker Road
San Jose, CA 95134-2127
Phone:408.943.6900 Fax: 408.943.7943
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SEMI Draft Document #4494
Revision to SEMI F15, with title change from: TEST METHOD FOR ENCLOSURES USING SULFUR HEXAFLUORIDE TRACER GAS AND GAS CHROMATOGRAPHY, to: TEST METHOD (SF6TRACER GAS) FOR ENCLOSURES HAS BEEN MOVED TO SEMI S06
This standard was technically approved by the global Environmental, Health, & Safety Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on ????. It was available at in???? and on CD-ROM in ????. Originally published in 1995; previously published November 2001.
NOTICE: This document was completely rewritten in 2007.
1 Purpose
1.1 The purpose of this document is to provide a permanent withdrawal notice for SEMI F15 indicating that the technical content has been superseded by Appendix 2, Test Method for Determining Fugitive Emissions by Using Tracer Gas of SEMI S06.
NOTE 1: In the event that SEMI changes their document withdrawal process so that withdrawn document notices do not automatically disappear after two years, this document may be formally withdrawn.
2 Scope
2.1 The scope of this document is all of the content of SEMI F15-0093-1104R.
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 Referenced Standards and Documents
3.1 SEMI Safety Guidelines
SEMI S06 — EHS Guideline for Exhaust Ventilation of Semiconductor Manufacturing Equipment
SEMI F15-0093-1104R — Test Method for Enclosures Using Sulfur HexafluorideTracer Gas and Gas Chromatography
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
4 Test Method
4.1 Use the test method described in Appendix 2, Test Method for Determining Fugitive Emissions by Using Tracer Gas of SEMI S06.
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.
NOTICE: The following information is provided to track revisions to this document. Negative votes may not be cast against this information. Changes can be submitted to SEMI Staff via a Publication Improvement Proposal (PIP) form.
Cycle / Authorization / Section / Description2007Cycle 5 / Letter Ballot / All / Replaced previous document, which defined a test method, with a pointer to the updated method in an Appendix to SEMI S06.
APPENDIX 2 Of SEMI S06-0707, included in this ballot for reference
TEST METHOD FOR DETERMINING FUGITIVE EMISSIONS BY USING TRACER GAS
NOTICE: The material in this appendix is an official part of SEMI S6 and was approved by full letter ballot procedures on April 25, 2007 by the global Environmental, Health & Safety Committee.
A2-1 Purpose
A2-1.1 This test method is intended to test the containment ability of a local exhaust ventilation system within an enclosure under the equipment supplier's specified operating conditions. Thus, test data obtained by means of this test method apply only to the exhaust ventilation conditions that existed within the enclosure during the testing. Extrapolation of the test data to other exhaust ventilation operating conditions is not usually valid.
A2-1.2 Use of this test method requires knowledge of the principles of gas analysis as well as flow and pressure measurement, gas analytical instrumentation, and gas sampling techniques.
NOTE 1: An acceptable enclosure does not imply a safe condition for routine equipment operation with a leak or a tubing/fitting failure. An acceptable enclosure is one that will contain potential worst-case leaks in an emergency, non-routine situation. The fact that an enclosure is acceptable does not imply that the equipment should remain in operation when a hazardous gas leak has been detected.
A2-2 Summary of Method
A2-2.1 A test is performed by releasing tracer gas at a constant flow rate (e.g., to represent a release to the enclosure under normal operation or to simulate a worst-case leak) within an enclosure and then measuring, on the periphery of the enclosure, the concentration of tracer gas. The lack of measurable tracer gas indicates that the release of potentially hazardous gases or vapors within the enclosure at the tracer gas injection point(s) will not result in their migration to the outside of the enclosure. Gas samples are taken by means of disposable syringes, sample bags, or sample vials. Gas samples are analyzed by means of electron capture gas chromatography, infrared spectrometry, or other equivalent means.
A2-3 Procedure
A2-3.1 Test Design
A2-3.1.1 Determine the volume of the enclosure.
A2-3.1.2 Measure the exhaust ventilation flow rate from the enclosure.
A2-3.1.3 Calculate the air changes per minute of the enclosure by dividing the exhaust ventilation flow rate by the enclosure volume.
A2-3.1.4 Calculate the time at which the tracer gas concentration in the enclosure will achieve approximate equilibrium. Concentration equilibrium occurs when the tracer gas concentration in the enclosure stops changing significantly as a function of time for a constant tracer gas release rate. Divide 3 by the air changes per minute to establish this time. § A2-6 provides a derivation of the equilibrium time.
NOTE 2: This test method is intended to test the containment ability of the local exhaust ventilation system within an enclosure when operated according to the equipment supplier's specifications. Thus, testing should be performed with the local exhaust ventilation operating under its equipment supplier's recommended conditions.
A2-3.1.5 Determine the release rate of the gas as described in § 7.
NOTE 3: In some cases, it may be practical to perform testing for a hypothetical release of the highest available flow of any gas at the highest toxicity of any gas, even if those conditions pertain to different gases. If, however, the available flow of the more toxic gases is substantially less than that of the less toxic gases, testing of several different model releases may be necessary to determine the optimal exhaust ventilation flow.
A2-3.2 Reagents and Materials
A2-3.2.1 Use a tracer gas diluted in an inert gas, such as nitrogen or argon, as the tracer gas source, to minimize measurement difficulties associated with small leaks of pure tracer gas from the supply cylinder and its associated piping.
A2-3.2.2 The physical characteristics, including molecular weight, density and viscosity, of the tracer gas or tracer gas mixture should be considered in determining its suitability to model the release of a particular SOC.
NOTE 4: In previous documents, sulfur hexafluoride (SF6) has been specified as the tracer gas to be used for this procedure. As SF6 has been identified as a global warming gas, it is no longer being specified. Any suitable gases or gas mixtures may be used.
NOTE 5: Historically, SF6 has been used in concentrations from 1 ppm to 1% in nitrogen for such tests. Therefore the density of the tracer gas mixture has been similar to that of air. There do not appear to have been measurement difficulties attributed to the difference between the diffusivity of SF6 and of the SOCs, although diffusivity is affected by molecular weight of the SF6 molecules, not the density of the SF6/N2 mixture.
A2-3.3 Sampling
A2-3.3.1 In selecting the location of samples collected outside the enclosure, consider 1) potential leak points, 2) the direction of the release, 3) laminar flow characteristics in the area surrounding the enclosure and 4) that high air velocities at the air sample point will result in dilution of the sample. Samples should be collected from all sides of the enclosure, downstream in the prevailing room airflow, and in the operating personnel occupancy areas.
NOTE 6: Results with room air velocities greater than 0.13 m/s (25 linear feet per minute) may not be representative of the conditions at the user's location and may produce results that are not applicable to equipment that is in locations with lower airflow rates around the equipment.
A2-3.3.2 Collect background (baseline) samples from the area surrounding the enclosure at predetermined locations. When logistics permit, analyze the background samples before releasing the tracer gas. If background levels above approximately 1 ppb are detected, evaluate the integrity of the tracer gas delivery system, and postpone the test until the concentration is less than 1 ppb. Other sources of tracer gas in the immediate test area may also cause this background.
A2-3.3.3 Measure and record the air flow velocity (direction and speed) at each of the sampling locations.
NOTE 7: If testing is performed with atracer gas background, the background concentration must be measured and subtracted from any subsequently measured tracer gas concentration value.
A2-3.3.4 Release tracer gas within the enclosure being tested by means of an injection manifold, shown schematically in Figure A2-1. The tracer gas injection manifold must be capable of measuring flow rates to an accuracy of ±5%. The tracer gas delivery line must be routed into the enclosure and positioned at a potential leak point without violating the integrity of the enclosure.
Figure A2-1
Schematic Drawing of Injection Manifold
NOTE 8: To minimize tracer gas contamination of the area surrounding an enclosure during a test, the end of the tracer gas injection line should be capped, except when performing an injection test.
A2-3.3.5 The time required for the enclosure to reach equilibrium should be considered when establishing the time to begin sampling. The first sample after initiating tracer gas flow should be taken at the enclosure equilibrium time. Additional samples should be collected at 1, 3 and 5 minutes thereafter. After taking the sample at 5 minutes, shut off the tracer gas source. The final set of samples should be collected 1 minute after shutting off the tracer gas source.
A2-3.3.6 Perform the test so that the location and direction of release, relative to any opening or penetration in the enclosure, effectively simulate an actual or foreseeable gas release, as described in §Error! Reference source not found.. More than one test should be performed if it is not obvious which release location and direction represent the "reasonably foreseeable worst case".
A2-3.3.6.1 A worst-case failure can be simulated by locating the tracer gas injection point at the potential leak location closest to a penetration or opening within the enclosure with the direction of tracer gas injection pointed as close as is reasonably foreseeable to directly at the opening or penetration. The flow velocity of the tracer gas release should be no less than the flow velocity of the realistic worst-case leak. Details of release (flow rate, velocity, direction, foreseen failure) should be provided in test report (see § A2-5.)
A2-3.3.7 After initiation of tracer gas injection, collect grab air samples from the area surrounding the enclosure at predetermined times and locations. These samples should be analyzed immediately after collection. If this is not possible, they should be sealed. Label the samples as to time and location. Samples may be taken with a) containers that are non-absorbent, inert, and that have low permeability (such as polyvinyl fluoride film or polyester film sample bags or polyethylene, polypropylene, nylon, or glass bottles) or b) disposable syringes. Disposable syringes can be used to inject samples into the gas chromatograph directly when using gas chromatography to analyze samples.
A2-3.3.8 Record a) the actual (measured) tracer gas release rate, b) the actual tracer gas concentration in the tracer gas being used, and c) the actual release time during a test.
A2-3.3.9 Collect air samples as described in § A2-3.3.6, and analyze them for the presence or absence of tracer gas using a gas chromatograph, infrared spectrometry, or other suitable method with sufficient sensitivity. The measurement of a tracer gas concentration above background in the area surrounding an enclosure indicates incomplete containment of contaminants within the enclosure.
A2-3.3.10 Analyze samples according to recognized test methods for the analytical equipment to be used. Samples may be analyzed immediately after a test, or they may be stored for future analysis. Experience has shown no degradation of concentration of SF6in polypropylene syringes when stored for several months as long as the needle or syringe is plugged.
A2-4 Calculations and Interpretation of Results
A2-4.1 The maximum concentration of tracer gas measured in a sample collected outside the enclosure is used to calculate the Equivalent Release Concentration (ERC) by the following formula:
(A2-1)
NOTE 9: Related Information 6 presents the derivation of this formula.
A2-4.2 Compare the Equivalent Release Concentration to the relevant control limits. If the ERC is above the prescribed limits, the enclosure is not considered to be acceptable for the SOC and conditions tested; if the ERC is less than or equal to the prescribed limit, the enclosure is considered acceptable for the SOC and conditions tested. SEMI S2 recommends appropriate control limits for an enclosure.