ASTM_F_534_-_02.pdf

Designation:F 534 02Standard Test Method forBow of Silicon Wafers1This standard is issued under the fixed designation F 534;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.INTRODUCTIONWhen this test method was developed in the 1970s,non-contact bow and warp gages employingmanual positioning,which are the basis of this test method,were in routine use.More recently,faster,automated instruments have replaced these manual gages for most common uses in the semiconductiorindustry.In these automatic systems,microprocessors or microcomputers are used to control waferpositioning,operate the instrument and to analyze the data.See Test Method F 1390.Despite the fact that this test method is not commonly used in its present form,it embodies all thebasic elements of this test method and a simple analysis of data.Thus,it provides useful guidance inthe fundamentals and application of differential non-contact wafer bow measurements.1.Scope1.1 This test method covers determination of the averageamount of bow of nominally circular silicon wafers,polishedor unpolished,in the free(non-clamped)condition.1.2 This test method is intended primarily for use withwafers that meet the dimension and tolerance requirements ofSEMI Specifications M1.1.3 This test method can also be applied to circular wafersof other semiconducting materials,such as gallium arsenide,orelectronic substrate materials,such as sapphire or gadoliniumgallium garnet,that have a diameter of 25 mm or greater,athickness of 0.18 mm or greater,and a ratio of diameter tothickness up to 250.Wafers to be tested may have one or morefiducial flats provided they are located in such a way that theslice can be centered on the support pedestals(see 7.1.2)without falling off.1.4 The values stated in inch-pound units are to be regardedas the standard.The values given in parentheses are forinformation only.1.5 This standard does not purport to address the safetyconcerns,if any,associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2.Referenced Documents2.1 ASTM Standards:F 533 Test Method for Thickness and Thickness Variationof Silicon Slices2F 657 Test Method for Measuring Warp and Total ThicknessVariation on Silicon Wafers by Noncontact Scanning2F 1390 Test Method for Measuring Warp on Silicon Wafersby Automated Noncontact Scanning22.2SEMI Standard:M1Specifications for Polished Monocrystalline SiliconSlices32.3Federal Standard:Fed.Std.No.209BControlled Environment Clean Roomand Work Station Requirements43.Terminology3.1 Definitions:3.1.1 back surfaceof a semiconductor wafer,the exposedsurface opposite to that upon which active semiconductordevices have been or will be fabricated.3.1.2 bowof a semiconductor wafer,the deviation of thecenter point of the median surface of a free,unclamped waferfrom a median-surface reference plane established by threepoints equally spaced on a circle with diameter a specifiedamount less than the nominal diameter of the wafer.3.1.2.1 DiscussionIf the median surface of a free,unclamped wafer has a curvature that is everythere the same,bow is a measure of its concave or convex deformation,independent of any thickness variation that may be present.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.06 on SiliconMaterials and Process Control.Current edition approved Jan.10,2002.Published March 2002.Originallypublished as F534 77 T.Last previous edition F534 97.2Annual Book of ASTM Standards,Vol 10.05.3Available from Semiconductor Equipment and Materials International,805 E.Middlefield Rd.,Mountain View,CA 94043.4Available from GSA Business Service Centers in Boston,New York,Atlanta,Chicago,Kansas City,MO,Fort Worth,Denver,Seattle,San Francisco,and LosAngeles.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Positive values of bow denote a convex(mounded)mediansurface when the wafer is positioned with its front surface up.Conversely,negative values of bow denote a concave(dished)median surface when the wafer is positioned with its frontsurface up.Although bow may be caused by unequal stresseson the two exposed surfaces of the wafer,it cannot bedetermined from measurements on a single exposed surface.3.1.3 front surfaceof a semiconductor wafer,the exposedsurface upon which active semiconductor devices have been orwill be fabricated.3.1.4 median surfaceof a semiconductor wafer,the locusof points in the wafer equidistant between the front and backsurfaces.4.Summary of Test Method4.1 The wafer is supported,front surface upward,on threep