1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 14291:2012Vacuum gauges Definitions and specificationsfor quadrupole massspectrometersBS ISO 14291:2012 BRITISH STANDARDNational forewordThis British Standard is the UK im
2、plementation of ISO 14291:2012.The UK participation in its preparation was entrusted to TechnicalCommittee MCE/8/-/4, Vacuum technology.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovi
3、sions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 74400 6ICS 23.160Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published und
4、er the authority of theStandards Policy and Strategy Committee on 31 August 2012.Amendments issued since publicationDate Text affectedBS ISO 14291:2012 ISO 2012Vacuum gauges Definitions and specifications for quadrupole mass spectrometersManomtres vide Dfinitions et spcifications des spectromtres de
5、 masse quadripolairesINTERNATIONAL STANDARDISO14291First edition2012-07-15Reference numberISO 14291:2012(E)BS ISO 14291:2012ISO 14291:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reprodu
6、ced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01
7、 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 14291:2012ISO 14291:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Terms and definitions . 12.1 Definitions of components 12.2 Definitions of physical parameters . 5
8、3 Symbols and abbreviated terms . 84 Principle of QMS 95 Specifications for a QMS to be provided by manufacturers . 95.1 Mass range 95.2 Type of ion source . 95.3 Type of ion detector 95.4 Mass resolution .105.5 Mass number stability 105.6 Sensitivity 105.7 Linear response range .105.8 Minimum detec
9、table partial pressure 105.9 Minimum detectable concentration 105.10 Maximum operational pressure .105.11 Scanning parameter .105.12 Signal output 115.13 Potentials . 115.14 Detector specifications 115.15 Set point . 115.16 Maximum bake-out temperature . 115.17 Nominal operating conditions 115.18 Wa
10、rm-up time . 115.19 Filament material . 115.20 Electron emission current . 115.21 Filament exchange 115.22 Detector exchange 115.23 Fitting to chamber .125.24 Mounting orientation 125.25 Dimensions .125.26 Internal volume 125.27 Mass of sensor head and electronic unit 125.28 Input power of electroni
11、c unit 125.29 Cable .125.30 Software .125.31 Interface .125.32 Storage and transportation condition126 Optional specifications for QMS to be provided by manufacturers 136.1 Mass resolution .136.2 Fragmentation or cracking pattern .136.3 Temperature coefficient of sensitivity .136.4 QMS sensor cleani
12、ng .136.5 Degassing 136.6 Degassing power .136.7 Photographs .136.8 Inspection record 136.9 Outgassing rate .13Bibliography .14BS ISO 14291:2012ISO 14291:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies)
13、. The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non
14、-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part
15、2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a
16、vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 14291 was prepared by Technical Committee ISO/TC 112, Vacuum technology.iv ISO 2012 All right
17、s reservedBS ISO 14291:2012ISO 14291:2012(E)IntroductionQuadrupole mass spectrometers (QMSs) are nowadays used not only for leak detection and residual gas analysis in vacuum but also as instruments to provide quantitative analysis in processes and control processes such as physical and chemical vap
18、or deposition, and etch processes.Total pressure, composition of the gas mixture, QMS settings, environment conditions, etc., have a significant influence on the measured signal, its uncertainty and interpretation. For this reason, it is not possible to calibrate QMS for all its possible application
19、s. Instead, it has either to be calibrated for the particular conditions of use or for a standardized condition.There is also some need for standardization in order to enable QMS users to compare devices of different manufacturers and to use the QMS properly.In continuation of efforts of TC 112 duri
20、ng the 1990s, this International Standard takes a first step towards establishment of a standardized calibration procedure for QMS by defining the terms and parameters. ISO 2012 All rights reserved vBS ISO 14291:2012BS ISO 14291:2012Vacuum gauges Definitions and specifications for quadrupole mass sp
21、ectrometers1 ScopeThis International Standard defines terms relevant to quadrupole mass spectrometers (QMSs) and specifies the parameters required for specification by QMS manufacturers necessary for proper calibration and for maintaining the quality of partial pressure measurement.This Internationa
22、l Standard applies to QMSs with an ion source of the electron impact ionization type. Such QMSs are designed for the measurement of atomic mass-to-charge ratios m/z typically 300. QMSs with other ion sources, such as those of the chemical ionization, photoionization, and field ionization types, as w
23、ell as the measurements of m/z above 300, which are mainly used to specify organic materials, lie outside the scope of this International Standard.2 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.2.1 Definitions of components2.1.1quadrupole mass spe
24、ctrometerQMSmass spectrometer in which ions are injected axially into a quadrupole lens consisting of a system of four electrodes, usually rods, to which radio frequency and d.c. electric fields in a critical ratio are applied, so that only ions with a certain mass/charge ratio emergeSOURCE: ISO 352
25、9-3:1981,23.5.2.2Note 1 to entry Such a QMS consists of a sensor head and electronic unit.2.1.2sensor headanalyser tubesensorsensor unitsensing headgauge headequipment consisting of an ion source, quadrupole mass filter, and ion detector in one enclosure2.1.3ion sourcepart of the QMS in which ions o
26、f gas molecules and atoms are producedNote 1 to entry For the production of positive ions, the ion source generally uses an electron impact ionization process.2.1.3.1open ion sourceion source with a high conductance to the surrounding vacuum environment, often designed as an open grid structureNote
27、1 to entry All of the operational components of this ionization hardware are exposed to the same vacuum region.INTERNATIONAL STANDARD ISO 14291:2012(E) ISO 2012 All rights reserved 1BS ISO 14291:2012ISO 14291:2012(E)2.1.3.2closed ion sourceenclosed ion sourcedifferential pressure ion sourceion sourc
28、e that uses a nearly sealed container to ionize the gas to be analysed with openings only for passing; sample gas; energetic electrons (for impact ionization); and exciting ionsNote 1 to entry This type of ion source permits ionization at pressures that are higher than the mass filter and detector.
29、It should be used in a sample pressure reduction system with a high vacuum pump on the mass filter.2.1.3.3molecular beam ion sourcecrossed beam ion sourceion source that accepts a focused beam of neutral gas molecules directed at the ion formation region without interference from any ion source comp
30、onentsNote 1 to entry The molecular beam traverses the ion formation region and is usually at right angles to the electron beam and mass filter axes.Note 2 to entry For molecular beam epitaxy, the crossed beam ion source is also designed to accept molecular beams at various acceptance angles. Some m
31、olecular beam ion source designs include a protective shroud around the ion source with an aperture to the ion formation region. As the molecular beam exits the ion source, it may be trapped or pumped to minimize contribution to background from scattered molecules.2.1.4quadrupole mass filterdevice c
32、onsisting of four parallel conductive rods arranged in a square array with opposite rods connected electrically in parallelNote 1 to entry A quadrupole mass filter separates the ions coming from the ion source on the basis of their mass-to-charge ratios by a critical ratio of radio frequency (r.f.)
33、and direct current (d.c.) electrical fields applied to the rods. The rod pairs are driven with opposite r.f. phase and d.c. polarity.2.1.5ion detectorion collectordevice collecting the positive ions that have passed through the mass filter to measure the ion currentNote 1 to entry Two types of ion d
34、etectors are common: Faraday cup and secondary electron multiplier (SEM).2.1.5.1Faraday cupmetal plate or open cylinder or similar on which the ions from the mass filter are collectedNote 1 to entry An actual Faraday cup ion detector is illustrated in Figure 1 a). However, a metal plate, Figure 1 b)
35、, open cylinder, Figure 1 c), or similar on which the ions from the mass filter are collected is usually called a Faraday cup-type ion detector. A Faraday cup generally has a gain of unity, i.e. for each ion collected, one electron flows from the detecting electrometer.2.1.5.2secondary electron mult
36、iplierSEMdetector in which the ions from the mass filter strike the entrance surface and release electronsNote 1 to entry The released electrons are accelerated and strike another surface of the SEM resulting in multistage amplification of the electron current. SEMs can use discrete dynodes or a con
37、tinuous dynode surface with a potential gradient to increase the electron current and microchannel plate electron multiplier.2 ISO 2012 All rights reservedBS ISO 14291:2012ISO 14291:2012(E)a) Faraday cup type b) Metal plate type c) Open cylinder typeFigure 1 Faraday cup type ion detector2.1.5.2.1dis
38、crete dynode electron multipliersecondary electron multiplier that uses discrete dynodes between which secondary electrons are acceleratedNote 1 to entry The voltages applied to each dynode establish the potential gradients that accelerate the secondary electrons and lead to increased numbers of ele
39、ctrons at each stage. Figure 2 is a schematic diagram of a discrete dynode electron multiplier.Key1 ammeter2 electron3 negative high voltageFigure 2 Discrete dynode electron multiplier2.1.5.2.2continuous dynode electron multiplier1)CEMtype of secondary electron multiplier with a continuous dynode, o
40、ften with a horn-like channelNote 1 to entry See Figure 3.Note 2 to entry The applied voltage from entrance to exit of the channel establishes the potential gradient along the channel which accelerates secondary electrons and leads to increased numbers of electrons from entrance to exit. 1) One of t
41、he original CEMs is known as Channeltron. Channeltronis the trademark of a product supplied by Burle. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product named. ISO 2012 All rights reserved 3BS ISO 14291:2012ISO 14291:2
42、012(E)Key1 ammeter2 electron3 negative high voltageFigure 3 Continuous dynode electron multiplier (CEM)2.1.5.2.3microchannel plate electron multiplierMCP electron multipliertype of secondary electron multiplier which consists of a large number of small, parallel continuous-dynode channels (typically
43、 5 m to 25 m in diameter), in a planar array, or “plate”2.1.6electronic unitunit consisting of a radio frequency source and several regulated power supplies and amplifiers which operate the ion source and mass filter as well as measure detected ion currentNote 1 to entry The electronic unit usually
44、incorporates a microprocessor and firmware to control the electronics and usually pass data to an external computer. Electronic units may be integrated or separate.2.1.6.1integrated typeelectronic unit mounted directly on sensor headNote 1 to entry See Figure 4.2.1.6.2separated typeelectronic unit s
45、eparated from the sensor head but connected to it via one or more cablesNote 1 to entry See Figure 5.Key1 electronic unit2 computerFigure 4 Integrated electronic unit4 ISO 2012 All rights reservedBS ISO 14291:2012ISO 14291:2012(E)Key1 electronic unit2 computerFigure 5 Separated electronic unit2.2 De
46、finitions of physical parameters2.2.1sensitivitySratio of the change in spectrum peak height (ion current), I - I0, to the corresponding change in partial pressure, p - p0SpIIpp()=()00(1)whereI is the ion current measured at partial pressure p;I0is the ion current measured at residual pressure p0Not
47、e 1 to entry Sensitivity is expressed in amperes per pascal.Note 2 to entry Sensitivity is defined differently in ISO 27894:20094for an ionization gauge with an emissive cathode. The sensitivity of a hot-cathode ionization gauge is defined asSIIIpp=()ce00(2)whereIcis the ion current measured at pres
48、sure p;I0is the ion current measured at residual pressure p0;Ieis the emission current.2.2.2relative sensitivity factorrxsensitivity Sxfor a specified gas species, x, divided by sensitivity SN2for nitrogen for the same device at the same pressure and the same operation conditions:rSSxxN2= (3) ISO 20
49、12 All rights reserved 5BS ISO 14291:2012ISO 14291:2012(E)Note 1 to entry Relative sensitivity factors depend on the operational parameters of QMS as shown in References 131617. If necessary for reasons of accuracy, it is recommended that relative sensitivity factors be measured before each measurement.2.2.3mass resolutionsmallest mass difference m between two equal magnitude peaks so that the valley between them is a specified fraction of the peak heightNote 1 to entry See Figure 6.KeyI ionic currentm/z mass
