ASTM_F_1390_-_97.pdf

Designation:F 1390 97Standard Test Method forMeasuring Warp on Silicon Wafers by AutomatedNoncontact Scanning1This standard is issued under the fixed designation F 1390;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.1.Scope1.1 This test method covers a noncontacting,nondestructiveprocedure to determine the warp of clean,dry semiconductorwafers.1.2 The test method is applicable to wafers 50 mm or largerin diameter,and 100 m(0.004 in.)approximately and larger inthickness,independent of thickness variation and surfacefinish,and of gravitationally-induced wafer distortion.1.3 This test method is not intended to measure the flatnessof either exposed silicon surface.Warp is a measure of thedistortion of the median surface of the wafer.1.4 This test method measures warp of a wafer corrected forall mechanical forces applied during the test.Therefore,theprocedure described gives the unconstrained value of warp.This test method includes a means of canceling gravity-induced deflection which could otherwise alter the shape of thewafer.2The resulting parameter is described by Warp(2)inAppendix X2 Shape Decision Tree in SEMI Specification M 1.(See Annex A1.)NOTE1Test Method F 657 measures median surface warp using athree-point back-surface reference plane.The back-surface referenceresults in thickness variation being included in the recorded warp value.The use(in this test method)of a median surface reference planeeliminates this effect.The use(in this test method)of a least-squares fitreference plane reduces the variability introduced in three-point planecalculations by choice of reference point location.The use(in this testmethod)of special calibration or compensating techniques minimizes theeffects of gravity-induced distortion of the wafer.1.5 The values stated in SI units are to be regarded sepa-rately as the standard.The values given in parentheses are forinformation only.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.2.Referenced Documents2.1 ASTM Standards:F 657 Test Method for Measuring Warp and Total ThicknessVariation on Silicon Slices and Wafers by NoncontactScanning3F 1241 Terminology of Silicon Technology32.2SEMI Standard:M 1 Specifications for Polished Monocrystalline SiliconWafers43.Terminology3.1 Definitions:3.1.1 mechanical signature of an instrument,that compo-nent of a measurement that is introduced by the instrument andthat is systematic,repeatable,and quantifiable.3.1.2 median surfaceof a semiconductor wafer,the locusof points equidistant from the front and back surfaces.3.1.3 quality areathat portion of a wafer within thespecified parameter is determined.3.1.4 reference plane of a semiconductor wafer,a planefrom which deviations are measured.3.1.5 reference plane deviation(RPD)the distance from apoint on a reference plane to the corresponding point on awafer surface.A dome-shaped wafer is considered to havepositive RPD at its center;a bowl-shaped wafer is consideredto have negative RPD at its center.3.1.6 thicknessof a semiconductor wafer,the distancethrough the wafer between corresponding points on the frontand back surfaces.3.1.7 waferof a semiconductor,the difference betweenthe maximum and minimum distances of the median surface ofa free,unclamped wafer from a reference plane.3.1.7.1 DiscussionAlthough warp may be caused by un-equal stresses on the two exposed surfaces of the wafer,itcannot be determined from measurements on a single exposedsurface.The median surface may contain regions with upwardor downward curvature or both;under some conditions themedian surface may be flat(see figures in Appendix X1).3.2 Other definitions relative to silicon material technologycan be found in Terminology F 1241.1This test method is under the jurisdiction of ASTM Committee F-1 onElectronicsand is the direct responsibility of Subcommittee F01.06 on SiliconMaterials and Process Control.Current edition approved June 10,1997.Published August 1997.Originallypublished as F 139092.Last previous edition F 1390921.2Poduje,N.,“Eliminating Gravitational Effect in Wafer Shape Measurements,”NIST/ASTM/SEMI/SEMATECH Technology Conference,Dallas,TX;Technologyfor Advanced Materials/Process Characterization,February 1,1990.3Annual Book of ASTM Standards,Vol 10.05.4Available from SEMI,805 East Middlefield Road,Mt.View,CA 94043.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTM4.Summary of Test Method4.1 A calibration procedure is performed.In addition to