Semiconductor Equipment and Materials International
3081 Zanker Road
San Jose, CA 95134-2127
Phone: 408.943.6900, Fax: 408.943.7943
hb khghgh1000A5667
Background Statement for SEMI Draft Document 5667A
NEW STANDARD: TEST METHOD FOR DETERMINATION OF MOISTURE DRY-DOWN CHARACTERISTICS OF GAS DELIVERY COMPONENTS
Notice: 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.
Notice: 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.
Background
The test method applies to all types of in-line components used in gas delivery systems for precise delivery of gas species for semiconductor manufacturing. Any analyzer that is capable of measuring the required concentration levels of moisture with a fast response and adequate dynamic range and which is calibrated using best practices and traceable standards can be used. This ballot is to create a new test method.
The ballot results will be reviewed and adjudicated at the meetings indicated in the table below. Check http://www.semi.org/standards under Calendar of Events for the latest update.
Review and Adjudication Information
Task Force Review / Committee AdjudicationGroup: / Filters and Purifiers Task Force / NA Gases TC Chapter
Date: / Monday, July 13, 2015 / Tuesday, July 14, 2015
Time & Timezone: / 9:30 AM to 11:00 AM, US Pacific Time / 9:00 AM to 12:00 Noon, US Pacific Time
Location: / San Francisco Marriott Marquis Hotel
780 Mission Street / San Francisco Marriott Marquis Hotel
780 Mission Street
City, State/Country: / San Francisco, California 94103 / San Francisco, California 94103
Leader(s): / Mohamed Saleem (Fujikin)
Sowmya Krishnan (Semitrac) / Tim Volin (Parker Hannifin)
Mohamed Saleem (Fujikin)
Standards Staff: / Paul Trio (SEMI NA)
408.943.7041 / / Paul Trio (SEMI NA)
408.943.7041 /
*This meeting’s details are subject to change, and additional review sessions may be scheduled if necessary. Contact the task force leaders or Standards staff for confirmation.
Telephone and web information will be distributed to interested parties as the meeting date approaches. If you will not be able to attend these meetings in person but would like to participate by telephone/web, please contact Standards staff.
SEMI Draft Document 5667A
NEW STANDARD: TEST METHOD FOR DETERMINATION OF MOISTURE DRY-DOWN CHARACTERISTICS OF GAS DELIVERY COMPONENTS
1 Purpose
1.1 This Document describes the procedure for determination of the moisture dry-down characteristics of components used in gas delivery systems. The results of this test can be used for the qualitative ranking of gas delivery components based on the design as it relates to moisture dry-down performance of the system.
2 Scope
2.1 This Test Method applies to all types of in-line components used in gas delivery systems for precise delivery of gaseous species used in semiconductor manufacturing. The in-line components applicable are valves (pneumatic, manual and hybrid types), mass flow controllers, pressure regulators, filters and passive components such as pressure gauges / transducers and flow meters.
2.2 Test Medium — The test medium shall be nitrogen. Other inert gases will have different purging characteristics and may dry a system more quickly or slowly. Reactive gases shall not be used as they may react chemically with moisture. Considerations relating to corrosion resistance are outside the scope of the present document, although the test procedure may prove useful in corrosion studies. The results will provide a ranking with respect to moisture contribution arising as a result of differences in design.
2.3 Operating Situations — Moisture contribution from a gas delivery component may be the result of improper design and construction, contamination arising in its manufacture, or from subsequent exposure to ambient air or non-dry gas. Thus, it is necessary to consider two main situations:
2.3.1 The “initial dry-down” situation, which is determined by the moisture content of the component in the as-received condition, with the effects of manufacturing process and design, surface quality, pre-treatment and packaging convoluted together. This test is optional and may be omitted based on the objective of the testing.
2.3.2 The “response to an upset” situation, which is determined by the amount of moisture taken up by the component and subsequently released in any exposure after receipt during its operation independently or as part of a gas delivery system.
NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their use. It is the responsibility of the users of the Documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 This Test Method allows the determination of moisture dry-down characteristics which can be used, for example, to qualitatively rank components. Since different moisture dry-down characteristics are permissible in different situations, selecting the “best” component requires consideration of how they will be used, either qualitatively or through a numerical simulation of component behavior.
3.2 The Test Method can only be used for qualification / certification of gas delivery components based on different designs and internal materials such as seats / seals.
4 Referenced Standards and Documents
4.1 SEMI Standards
SEMI C15 — Test Method for ppm and ppb Humidity Standards
SEMI F112 — Test Method for Determination of Moisture Dry-Down Characteristics of Surface-Mounted and Conventional Gas Delivery Systems by Cavity Ring Down Spectroscopy (CRDS)
4.2 ASTM Standard[1]
ASTM F1397-93 — Standard Test Method for Determination of Moisture Contribution by Gas Distribution System Components
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 Abbreviations and Acronyms
5.1.1 APIMS — Atmospheric Pressure Ionization Mass Spectroscopy
5.1.2 CRDS — Cavity Ring Down Spectroscopy
5.1.3 DUT — Device Under Test, gas delivery component subjected to test.
5.1.4 EPSS — electropolished stainless steel
5.1.5 ppm — molar parts per million (µmole / mole). The same as ppmv.
5.1.6 ppb — molar parts per billion (nmole / mole). The same as ppbv.
5.1.7 ppt — molar parts per trillion (pmole / mole). The same as pptv.
5.1.8 slpm — standard liters per minute, the gas volumetric flow rate measured in liters per minute at 0°C and 1 atm.
5.2 Definitions
5.2.1 baseline — an instrument response under steady state conditions.
5.2.2 glove box — an enclosure that contains a controlled atmosphere, usually inert.
5.2.3 induction time — the elapsed time between when humidified gas is introduced to the DUT and when moisture is detected at the moisture analyzer. For a DUT which is perfectly transparent to moisture, the induction time is equal to the residence time of the gas in the system.
5.2.4 peak height — the maximum moisture concentration recorded when a moisture input of pre-defined length and concentration is introduced to a DUT.
5.2.5 response time — the time required for the DUT to reach steady state after a change in concentration.
6 Summary of Test Method
6.1 This Test Method consists of initial dry-down and moisture input tests for gas delivery components such as mass flow controllers (MFCs), pneumatic and manual valves (including hybrid valves), pressure regulators and filters.
6.2 MFCs will vary in dry-down performance based on their flow rating and therefore the dry-down performance of only comparable flow rate MFCs should be compared. In addition, the flow rates of MFCs to be tested shall be within the specified flow requirements of the analyzer.
6.3 Pressure regulators shall be tested in the fully open condition, i.e., the regulator adjusted for minimal pressure drop through it. The effect of varying the pressure drop across the regulator on the moisture dry-down is outside the scope of this standard.
6.4 Manual valves shall be tested at the fully open condition so as to allow maximum flow through the valve. For pneumatic valves, manufacturer-recommended air actuation pressures shall be supplied to actuate the valve for normally closed valves. For normally open valves, air actuation will be necessary to turn off the valve during testing.
6.5 Particle filters shall be tested at the maximum flow rating as specified by the manufacturer.
7 Required Equipment
7.1 Moisture Analyzer — Any moisture analyzer capable of a dynamic range of 1 ppb to 2 ppm and capable of measuring the required concentration levels with a fast response and which is calibrated using best practices and traceable standards can be used. Examples of such moisture analyzers are: (a) CRDS: The CRDS analyzer used for moisture detection is a self-calibrating instrument that is easy to use and operate. CRDS analyzers can be mobile and deployed to the field for in-field validations. (b) APIMS: APIMS analyzers are typically stationary and the most sensitive technology available, with sufficient dynamic range. APIMS systems are usually more sensitive than CRDS and may be preferred for low concentration applications (c) Electrochemical: Electrochemical based sensors are usually inexpensive, small, portable and easy to operate, but not as stable as CRDS, and they require more frequent recalibration. They are usually not as sensitive as APIMS or CRDS, but may suffice for many applications.
7.2 All analyzer types shall be installed, calibrated and operated following the manufacturer’s guidelines.
7.3 Dry Gas — A source of dry nitrogen (1ppb or less moisture).
7.4 Moisture Generator — A moisture generator capable of delivering nitrogen doped with 1-2 ppm moisture up to the rated flow of the component. The output of the generator shall be verified according to SEMI C15.
7.5 Connectors — Most ultra-high purity components are currently fitted with metal gasket type connectors. The same type of connector shall, therefore, be incorporated into the test bench for connection to the DUT. The DUT shall not be modified, but an adaptor may be used to establish connection to the test bench.
7.6 Test Blank — Any series of tests shall include the results of testing a blank. The blank shall be the shortest convenient length (no more than 1 m) of 0.63 cm (1/4”) EPSS tubing with suitable fittings and/or adapters at either end to enable it to be inserted in place of the DUT.
7.7 Moisture Pulse Generator — A valve arrangement capable of switching instantaneously between dry and humidified nitrogen is also required. An example of such a design is shown in Figure 1. In this design, flow is maintained in both the humidified and dry gas lines at all times. By simultaneously switching valves V1a, V1b, or V2a, V2b , either humidified or dry gas is directed through the DUT while the other gas stream is directed to vent. Note that there is a bypass loop so that flow can be maintained to the analyzer when the DUT is removed. In this design, all gas lines should be constructed of EPSS tubing of high quality and kept as short as possible, with valve porting as shown in Figure 1, to minimize dead legs.
Figure 1
Moisture Test Schematic
7.7.1 The bypass loop will contain a stagnant volume of gas during testing. To avoid exposing the analyzer to a large moisture upset whenever it is fed with the gas contained in the bypass loop, the loop shall be thoroughly baked out (at ≥ 200°C) and protected from atmospheric contamination thereafter. Valve V3b shall be such that some flow can be maintained through the bypass loop and the DUT simultaneously as well as independently. Use of pneumatic valves to facilitate rapid and simultaneous switching is recommended.
7.7.2 Other arrangements for the test setup than that shown may also be used. The moisture pulse generator shall be designed so as to give the fastest possible response of the blank to a change in input moisture level.
7.8 Temperature Control and Measurement — A stable temperature during the test is of critical importance. The DUT shall be kept at 21°C. TESTS AT DIFFERENT TEMPERATURES CANNOT BE COMPARED. Ideally, the blank and DUT should be maintained in a temperature-controlled chamber. However, if this is impractical, a heating tape can be used. Temperature control should be to ±1ºC. A continuous record of temperature during the test shall be maintained.
8 Procedure
8.1 Blank Tests — If initial dry-down testing of DUT is not of interest, the initial dry-down test of the test blank may be omitted and the test blank brought to equilibrium with zero gas (less than or equal to 1ppb) in whatever manner that is most convenient, except that the test blank shall not be heated above 200ºC. Permanent changes in moisture interaction have been observed at temperatures above this level.
8.1.1 Initial Dry-down — Start the experiment with the blank in place of the DUT and a flow of dry gas through the analyzer. Follow the analyzer manufacturer’s procedure for initial dry-down and start-up.
8.1.1.1 Switch the gas flow to pass primarily through the bypass loop while maintaining a small flow through the test blank. Remove the test blank completely from the system. If a glove box or other such enclosure is used, do not remove the test blank from the glove box. Immediately reconnect the test blank to V3a, leaving it disconnected from V4a. Allow dry nitrogen to flow through the test blank for five minutes to purge the air from inside before reconnecting to V4a. Switch the gas to flow only through the blank and not through the bypass loop. The analyzer will show an increase in moisture concentration. Record the analyzer output until it reaches a steady state value.
8.1.1.2 Repeat the above test twice for a total of three data sets.
8.2 Tests on Actual DUT
8.2.1 Initial Dry-down Test — This portion of the test is designed to determine the out-of-bag dry-down time of the DUT in the condition in which it is typically supplied. Thus, the results of this test will reflect, by design, any precautions which the supplier has taken to remove moisture and maintain its dryness during shipping.
8.2.1.1 Start the test as in § 8.1.1. The DUT shall not be unpacked until after the analyzer has equilibrated with the background moisture level. If a glove box or other such enclosure is used, unpack the system in the glove box. Switch the dry nitrogen flow to pass through the bypass loop while maintaining a small flow through the test blank. Undo the final layer of packing and any shipping caps or plugs on the system at this point. Remove the sample blank and connect the DUT to valve V3a as quickly as possible. Ensure that the gas lines going to analyzer will be under N2 purge during the removal of test blank and installation of DUT. Allow the dry nitrogen flow to purge out any ambient air in the system for five minutes and then connect the system to V4a. Switch the gas to flow only through the DUT and not through the bypass loop and as per recommended flow based on the analyzer used. The analyzer will show an increase in moisture concentration. Record the analyzer’s output until it reaches 1ppb or less (as noted in 8.1.1.1).