Weir PSFM Fixed Focus Analysis Dataset:blanketfocmon.XLS Features:Full-wafer exposure, fixed focus Sections: Comparison of PSFM 180, 160 and PGM response PGM whole-wafer focus model Reticle Scan-stage analysis (Up/Down scan comparison) Up-Scan analysis Down-Scan analysis of image Average Field Astigmatic behavior TEA Systems Corp. 65 Schlossburg St. Alburtis, PA

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -2- Project Summary Candidate slides for Paper ?Comparison of PSFM 180, 160 and PGM response All 3 features present a lens-characteristic signature response 3 features can be used to replicate focus behavior of features with increasing density. –PSFM 180 = isolated –PGM = dense-packed feature performance. ?PGM whole-wafer focus model Modeled focus across wafer shows high-point in central area. X-Slit (lens) and Y-scan (reticle stage travel) characteristics Methods of plotting lens signature and reticle scan characteristics are shown ?Reticle Scan-stage analysis (Up/Down scan comparison) While being well balanced, stage is shown to contribute more noise in down-scan Scan tilt is present and shown Scan-speed nonlinearity shown to be greater in down-scan Sensitivity of direction and wafer-edge on field tilt Plate bowing during scan can be seen Astigmatism across slit is shown to have a directional component. –Consistent with the concept of scan-averaging of y-direction aberrations Background slides with in-depth analysis ?Up-Scan analysis ?Down-Scan analysis of image ?Average Field ?Astigmatic behavior

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -3- PSFM 180 – data conversion Data converted to focus errors

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -4- PSFM 180 Raw Focus Data Mean Focus contour shown Note the high focus errors located at left/right edges & in lower left edge. ?“7 o’clock” location Reticle stage scan direction

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -5- PSFM 180 – raw Astigmatism Data is before conversion to focus Used to determine data culling limits ?Use a cull = um base on quartiles. A total of 24 points were removed using this method.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -6- PSFM 160 Raw Focus

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -7- PGM Raw Focus Data Lens fingerprint is obvious

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -8- Comparison PSFM 180, 160 & PGM Ranges change Field signatures are very similar PGM and PSFM replication is very close.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -9- Comparison PSFM 180, 160 & PGM Mean ?Linear change from –93 to 0 to +25 nm for mean focus ?Represents progressively increased density in feature packing. Range ?Approximately the same with PSFM 160 being slightly higher ?Recall that PSFM data used some data culling Standard Deviation. ?Same for PSFM 180,160 ?Lower for PGM Astigmatism ?Follows mean focus trend PGMPSFM 160PSFM 180

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -10- Comparison; PGM & PSFM 180 Average field was removed. Note ranges are about the same.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -11- Comparison; PGM & PSFM 180 PSFM 180 ?Focus behavior replicates isolated line performance PGM ?Responds to focus like dense- packed features Differences ?Range of PSFM 180 is about 150nm greater ?Astigmatic behavior is different Pgm = -29nm, PSFM = 4 nm ?Standard deviation about the same

TEA Systems Corp. Confidential PGM Whole-wafer Analysis

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -13- PGM Focus modeled data Sites at lower-left exhibit greatest errors on wafer Wafer Model ?X-tilt is equivalent to Field Slit-tilt and will add

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -14- Wafer-based focus variation Wafer contributes a total of 39 nm focus error ?Systematic variations mostly lie with the +5, -7 nm range. ?Note high points at top and center as well as tilt.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -15- New Algorithm

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -16- New Algorithm, Residuals

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -17- X-slit flight characteristics Objective: ?View X-slit pitch, roll and dip Aberrations removed ?Wafer aberrations ?Average row X-focus ?Average column X-focus View variation in X-slit focus across wafer ?up-scan tendency to bow the field ?down-scan Greater problems with scan-direction tilt Down- scan Up- scan

Down- scan Up- scan

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -19- Y-Scan focus, Modeled field piston Y-scan focus Modeled focus piston (offset) for each row. Objective: ?View focus-signature across lens-slit

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -20- Slit Signature – using Y-scan focus piston Note circled row on right ?All down-scan ?Alternating field left & right edges Field tilt resulting from direction of travel-to-the-field

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -21- X-slit roll Only the modeled X-slit Tilt is shown ?Illustrates the roll of the slit as it is scanned Majority of tilt lies within the +/- 25 nm range (max=261 nm, min =-56 nm) Note large tilt on right side of wafer. Reticle-stage Scan direction

TEA Systems Corp. Confidential Scan Direction Analysis Examine the contribution of the reticle-stage scan to the focus-error budget ?Results in: Loss of process window Overlay errors in registration Asymmetric errors in critical feature size Analyze ?Raw-focus data ?Variations in modeled field performance

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -23- Reticle-Stage Scan Direction Reticle-stage Scan direction

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -24- Scan Direction Contours Mean-focus plotted

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -25- Scan Direction Statistics Astigmatism ?Same Mean focus ?Same Standard Deviation ?same Range ?Up scan < Down ?194 nm < 328 nm Down scan exhibits greater range than UP! ?We’ll see why in the next few slides Up ScanDown Scan

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -26- Radial-location Dependence Mean-focus and wafer-radial position Performance very similar Wafer-edge noise increases slightly for both distributions

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -27- Modeled Field and scan Field Model ?Every row/column modeled separately Best Focus (BF) ?Same Tilt ?Down-scan > up Curvature ?Up-scan > down Residuals ?St.Dev. residuals ?Random variation of down-scan > up Down-Scan, Modeled Field Up-Scan, Modeled Field

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -28- Comparison, Scan-stage flight path “Stable” fields values are plotted Note the increased “noise” of down-scan in 3 rd & 4 th rows Down-Scan, X-slit Piston Up-Scan, X-slit Piston

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -29- Comparison, Scan-stage flight path “Stable” fields values are plotted Note the increased “noise” of down-scan in 3 rd & 4 th rows Down-Scan, X-slit Piston Up-Scan, X-slit Piston

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -30- Comparison, X-slit signature All fields are collapsed onto one graph Plot modeled Y-scan Piston (focus offset) against position in slit Fluctuation at edges of lens ?“flutter” of slit height

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -31- Comparison, X-slit focus signature stability Down-scan tilts seem to drop toward outer edge of wafer. ?Auto-leveling limitation? Slit-signature is maintained in most fields Up Scan Down Scan

Comparison, X-slit focus signature stability Down-scan tilts seem to drop toward outer edge of wafer. ?Auto-leveling limitation? Slit-signature is maintained in most fields Up Scan Down Scan

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -33- Astigmatism – Scan-stage flight comparison Astigmatism = (Y-X) focus Y-Focus ?Errors are averaged by scan of the slit ?Sensitive to: scan-speed Pitch (y-tilt) of reticle-scan path X-focus ?Sensitive to: lens focus aberrations Roll (X-tilt) of slit from auto-leveling Up-scan (upper graph) ?Center-field is near-zero Constant velocity of scan ?Scan-start (left side) Requires 7 mm of scan to settle ?Scan stop (right side) Last 2 mm exhibit acceleration Down-scan (lower graph) ?Shown to be “noisier” scan direction ?Scanning top (right side) to bottom (left side) ?Acceleration is non-zero at only one point –7mm from field bottom Shown to be a point in field where curvature and field tilt change anomalously ?Source of down-scan noise! Same sign, velocity change Opposite sign, velocity change

Astigmatism – Scan-stage flight comparison Astigmatism = (Y-X) focus Y-Focus ?Errors are averaged by scan of the slit ?Sensitive to: scan-speed Pitch (y-tilt) of reticle-scan path X-focus ?Sensitive to: lens focus aberrations Roll (X-tilt) of slit from auto-leveling Up-scan (upper graph) ?Center-field is near-zero Constant velocity of scan ?Scan-start (left side) Requires 7 mm of scan to settle ?Scan stop (right side) Last 2 mm exhibit acceleration Down-scan (lower graph) ?Shown to be “noisier” scan direction ?Scanning top (right side) to bottom (left side) ?Acceleration is non-zero at only one point –7mm from field bottom Shown to be a point in field where curvature and field tilt change anomalously ?Source of down-scan noise! Same sign, velocity change Opposite sign, velocity change

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -35- Astigmatism – Across slit Comparison Signatures appear “Balanced” Up scan signature is mirror image of down-scan. ?Reason: unknown Suggestions? Up-scan Down-scan

TEA Systems Corp. Confidential Up-Scan analysis Detailed analysis of focus performance of exposure tool during the Up-scan stage of exposure

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -37- Wafer aberrations – Up-scan Mean focus plotted Objective: ?Examine and remove wafer aberrations. ?Obtain clearer picture of field variations

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -38- Modeled Field Aberrations Wafer Aberrations removed Mean Focus plotted ?Piston, tilt, curvature Model fitted to each field independently

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -39- Up-Scan, piston X-slit focus Objective: ?View reticle flight-path in up-scan direction Wafer aberrations removed. Display modeled focus-piston (offset) of each row ?Illustrates the variation in scan uniformity across wafer. Range of 50 nm ?seen in the plot of stable fields shown

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -40- Up-Scan, Y-scan focus Piston Modeled focus piston (offset) of each column. Objective: ?Observe slit-focus signature Graph is average of all fields ?Excluding top field at 12 o’clock

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -41- Up-Scan, Y-scan focus Piston Modeled focus piston (offset) of each column. Objective: ?Observe slit-focus signature Note retention of signature in all but the 4 th column ?Reticle bowing? Variation is in the average offset of each field and tilt.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -42- Up-Scan, Modeled X-slit Tilt Objective ?Observe “Roll” of slit along it’s glide path during scan. Slit tilt varies by 54 nm across wafer Note behavior of tilt at left and right edges of wafer ?Equivalent to the “Roll” of the reticle Platen.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -43- Up-Scan, modeled Y-scan Tilt Horizontal feature focus ?Wafer aberrations removed Pitch-variation of reticle scan- stage Objective: ?View pitch of scan stage as it travels from bottom to top ?Tilt modeled for each column of each field. Exhibits a 68 nm focus range contribution

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -44- Up-Scan, Y-scan flutter Y-scan curvature variation Objective: ?View 2 nd order, curvature, stability of each column ?Reticle is “flexed” as it scans This is a measure of the variation in focus at the start/stop of scan. Note the “flutter” at the extreme edges of the slit

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -45- Up-Scan – X slit curvature variation Variation in curvature of slit. ?Measured for each row of each field. Objective: ?Direct measure of 2 nd order flexure of reticle during scan Caused by bowing of the reticle during the scan?

TEA Systems Corp. Confidential Up-Scan, Residuals to modeled wafer & field Wafer aberrations are removed Field Piston, tilt and 2 nd order systematics are removed Residuals contain: ?Higher-order focus variations (systematic errors) ?Random noise

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -47- Up-Scan, Mean - Focus Note presence of higher –order scan signature. High-point “bumps” in scan center ?Viewed earlier in slit profile box-plots

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -48- Up-Scan, Residuals to Wafer & Field Y-scan ?Sensitive to noise during scan-travel Bearing chatter, stage flex X-slit ?Sensitive to lens aberrations Y-Scan Focus – Horizontal FeaturesX-slit Focus – Vertical Features

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -49- X-Slit Focus, across slit residuals High-order focus errors due to lens aberrations.

TEA Systems Corp. Confidential Down-scan focus behavior

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -51- Down-scan, raw data analysis

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -52- Down-Scan, Wafer aberrations

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -53- Down-scan, Wafer aberrations removed

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -54- Down-Scan, X-slit piston

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -55- X-Slit focus, Down-scan Objective: ?View reticle flight-path in up-scan direction Field Piston plotted Analysis and up-scan comparison in next slide

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -56- Down-Scan, Scan flight path using X-slit piston Modeled X-focus piston (offset) for each row Graph (above) summarizes five (5) fields shown Illustrates average path of reticle-scan table

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -57- Down Scan, Slit Signature Display of Modeled Y-scan piston (offset) ?One model for each column of each field Results in focus signature across lens- slit Slit signature (below) is average of all fields ?Note large variation at field edges

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -58- Down-scan, Y-scan Focus piston

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -59- Down-Scan, X-slit focus tilt

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -60- Down-Scan, X-slit curvature Note that the lower-left corner of the wafer is typically the location of the greatest focus errors.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -61- Down-scan, Y-scan focus Tilt

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -62- Down-scan, Y-scan focus Curvature

TEA Systems Corp. Confidential Average Field Analysis Fields across the wafer are “collapsed” or overlaid. Metrology for each field-site is averaged Objective: ?View average performance of field ?Attempt to estimate the aberrations of the aerial scan image.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -64- Mean Field & Scan Direction Up-scan Scan glide-path Lens-slit

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -65- Up-Scan – Wafer & Field tilt/piston removed Aberrations removed ?Wafer ?Field tilt ?Field piston Focus-error contributors ?Lens-aberrations ?Higher-order scan errors

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -66- Up-Scan Direction piston View modeled piston variation ?Top: for each column Focus errors across lens-slit ?Bottom: for each row Focus errors caused by scan- travel of slit Up-scan only Lens slit errors (top) ?Characteristic lens signature. ?On average, very level Bottom: scan glide-path ?Up-Scan exhibits a tilt ?Field-center point “bump” in scan This noise seen in earlier slides. Scan glide-path Lens-slit focus

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -67- Up-Scan – Field Tilt Vertical Features (left) ?X-slit tilt ?Note abrupt change in tilt at field center Vertical FeaturesHorizontal FeaturesMean Focus

TEA Systems Corp. Confidential Astigmatic Behavior (Y-X) Focus behavior The net-effect of this variation is to reduce the process window for this tool Objective: ?Analysis validation by comparison of values with those calculated from an Artemis Zernike study.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -69- Astigmatism – Up Scan Residuals to wafer aberrations Y-scan focus ?Primarily contributed by the scan- stage X-scan focus ?From lens focus errors ?From stage-scan errors

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -70- Astigmatism – Up Scan Artemis Astigmatic Zernike Scan glide-path Lens-slit Slit-astigmatic behavior (upper left) ?Tracks Z5 coefficient ?Note: Zernike analysis is from fy 2002 using a ring- aperture ?Estimated magnitude of Z5 errors is much less than measured. Scan-glide path (bottom left) ?Scanning averages & removes errors ?Errors at scan-start and end Caused by scan-speed nonlinearity. –Acceleration errors in scan stabilize out in frist 7 to 12 mm –Acceleration errors at end of scan indicate start of turn- around

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -71- Astigmatism – Up Scan No wafer removal ?Wafer aberrations previously also included piston Otherwise, calculations same as in previous analysis.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -72- Astigmatism – Down Scan Wafer aberrations removed

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -73- Astigmatism – Down Scan Slit signature (top) ?Classic lens signature at center ?Wings vary from up-scan Scan signature (bottom) ?Fairly level ?Scan now moving down Right to left on graph ?Non-flat performance suggest acceleration component present ?After the 3 rd row (from left), acceleration component again rises.

TEA Systems Corp. Confidential 0304Weir PSFM - Fixed Focus AnalysisPage -74- Astigmatism Wafer aberrations were removed Edge-field data culled Up and Down scans ?Up/down averaging removes signature resemblance to Z5 Zernike (upper right)