ASTM_F_728_-_81_1997e1.pdf

Designation:F 728 81(Reapproved 1997)e1Standard Practice forPreparing An Optical Microscope for DimensionalMeasurements1This standard is issued under the fixed designation F 728;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made throughout in December l997.1.Scope1.1 This practice covers the preparation of an optical mi-croscope for dimensional measurements.It is intended forpreparing an optical microscope to measure the width of lines,in the range from 0.5 to 12 m,inclusive,on hardsurfacephotomasks and processed silicon wafers.1.2 This practice is applicable for a microscope equippedwith a micrometer attachment,such as an optical filar,videofilar,optical image-shearing with optical or video display,optical image-scanning,or video image-scanning micrometer.Adjustment and calibration of the micrometer attachment is notincluded in this practice.1.3 This practice is intended for observing optically trans-parent specimens in bright-field transmitted illumination oroptically opaque specimens in bright-field reflected illumina-tion.It is not intended for dark-field illumination.1.4 This practice is limited to an optical microscope with anillumination system that is an integral part of the microscopebody and includes a condenser lens.1.5 No useful figure capable of showing the arrangement ofcomponents for all microscope designs is available;therefore,this practice does not contain illustrations and procedureswhich would suggest a specific microscope.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For more specifichazard statements,see Note 7,Note 8,and Note 17.2.Referenced Documents2.1 ASTM Standards:E 175 Terminology of Microscopy2F 127 Definitions of Terms Relating to Photomasking Tech-nology for Microelectronics33.Terminology3.1 Definitions:3.1.1 Other terms used in this practice are defined inTerminology E 175 and Definitions F 127.3.2 Definitions of Terms Specific to This Standard:3.2.1 coherencein optics,a measure of the ability of lightto interfere.3.2.1.1 DiscussionCoherence arising from the finite ex-tent of the light source is spatial coherence.Coherence arisingfrom the finite spectral width of the light source is temporalcoherence.3.2.2 coherence parameterin microscopy,the ratio of thecondenser numerical aperture to the objective numerical aper-ture for wide-field,bright-field,Kohler illumination.3.2.3 condenser aperture diaphragmin microscopy,afixed or variable opening that controls the light passing throughthe condenser and determines the value of the condensernumerical aperture.3.2.4 condenser lens or substage condenserin micros-copy,a lens that collects light for the purpose of illuminatingthe specimen.3.2.5 condenser numerical aperturein microscopy,theproduct of the index of refraction in object space multiplied bythe sine of half the angular aperture of the condenser.3.2.6 condenser systemin microscopy,lenses and mirrorsthat collect light for the purpose of illuminating the specimen.3.2.6.1 DiscussionAcondenser system usually consists ofmirrors,a lamp collector,relay lenses,and a condenser lens.3.2.7 contrastin microscopy,the ratio of the transmittanceor reflectance of two different areas on the specimen.3.2.8 cover glassin microscopy,a thin glass plate that isplaced over the specimen.3.2.8.1 DiscussionSome microscope objectives are de-signed for use with a cover glass of a specified thickness,anduse of these objectives without a cover glass or with a coverglass of a different thickness from the specified thicknessintroduces spherical aberration in the observed image.3.2.9 epi-objectivein microscopy,an objective with anannular mirror that acts as a lens to illuminate the specimen.3.2.9.1 DiscussionAn epi-objective is commonly used indark-field reflected illumination,but it is also useful in bright-field illumination.1This practice is under the jurisdiction of ASTM Committee F-1 on Electronicsand is the direct responsibility of Subcommittee F01.06 on Silicon Materials andProcess Control.Current edition approved June 26,1981.Published September 1981.2Annual Book of ASTM Standards,Vol 14.02.3Discontinued;see 1992 Annual Book of ASTM Standards,Vol 10.05.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTM3.2.10 field diaphragmin optics,a usually variable open-ing that controls the field of view.3.2.11 field of viewin microscopy,the area or solid angleviewed through the microscope.3.2.11.1 DiscussionFie