Weir PSFM Fixed Focus Analysis Dataset blanketfocmon XLS

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. 0304 Weir PSFM - Fixed Focus Analysis 65 Schlossburg St. Alburtis, PA 18011 610 682 4146 TZavecz@enter. net

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 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 ? ? 0304 Up-Scan analysis Down-Scan analysis of image Average Field Astigmatic behavior Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 2

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

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

PSFM 180 – raw Astigmatism • Data is before conversion to focus • Used to determine data culling limits ? Use a cull = 0. 013 um base on quartiles. • A total of 24 points were removed using this method. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 5

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

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

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

Comparison PSFM 180, 160 & PGM PSFM 180 PSFM 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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 9

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

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

PGM Whole-wafer Analysis 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 13

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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 14

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

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

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

Down- scan Up- scan 0304 Weir PSFM - Fixed Focus Analysis 18

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

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 20

X-slit roll Reticle-stage Scan direction • 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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 21

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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

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

Scan Direction Statistics Up Scan Down Scan • 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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 25

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

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

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

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

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 30

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

Comparison, X-slit focus signature stability • Down-scan tilts seem to drop toward outer edge of wafer. Up Scan ? Auto-leveling limitation? • Slit-signature is maintained in most fields Down Scan 0304 Weir PSFM - Fixed Focus Analysis 32

Astigmatism – Scan-stage flight comparison Same sign, velocity change • 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) Opposite sign, velocity change ? 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 • – 7 mm from field bottom • Shown to be a point in field where curvature and field tilt change anomalously ? Source of down-scan noise! 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 33

Astigmatism – Scan-stage flight comparison Same sign, velocity change • 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) Opposite sign, velocity change ? 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 • – 7 mm from field bottom • Shown to be a point in field where curvature and field tilt change anomalously ? Source of down-scan noise! 0304 Weir PSFM - Fixed Focus Analysis 34

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

Up-Scan analysis Detailed analysis of focus performance of exposure tool during the Up-scan stage of exposure 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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

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

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 39

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 40

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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 41

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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 42

Up-Scan, modeled Y-scan Tilt • Horizontal feature focus ? Wafer aberrations removed • Pitch-variation of reticle scanstage • 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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 43

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 44

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? 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 45

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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

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

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

Down-scan focus behavior 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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

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

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

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

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 55

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 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 56

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

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

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

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

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

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

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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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

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

Up-Scan Direction piston Lens-slit focus • 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 Scan glide-path • Bottom: scan glide-path ? Up-Scan exhibits a tilt ? Field-center point • “bump” in scan • This noise seen in earlier slides. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 66

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

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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential

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

Astigmatism – Up Scan Artemis Astigmatic Zernike Lens-slit • Slit-astigmatic behavior (upper left) Scan glide-path ? Tracks Z 5 coefficient ? Note: • Zernike analysis is from fy 2002 using a ringaperture ? Estimated magnitude of Z 5 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 turnaround 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 70

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

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

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. 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 73

Astigmatism • Wafer aberrations were removed • Edge-field data culled • Up and Down scans ? Up/down averaging removes signature resemblance to Z 5 Zernike (upper right) 0304 Weir PSFM - Fixed Focus Analysis TEA Systems Corp. Confidential 74