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PEB and CD analysis of two plates

LithoWorks PEB. PEB and CD analysis of two plates. August 14, 2003 Thermal analysis of two PEB plates: 093-08_peb_bake7.csv 093-08_peb_bake8.csv. Summary. These are preliminary results The first half of this analysis addresses PEB thermal analysis for PEB’s 7 & 8

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PEB and CD analysis of two plates

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  1. LithoWorks PEB PEB and CD analysis of two plates August 14, 2003 Thermal analysis of two PEB plates: 093-08_peb_bake7.csv 093-08_peb_bake8.csv

  2. Summary • These are preliminary results • The first half of this analysis addresses PEB thermal analysis for PEB’s 7 & 8 • Investigates Temperature cycle • Energy installed into the wafer (Temp * Time) • Variation in energy installed • Temperature over time contour plots • The second half of the analysis examines two Nanometrics OCD data sets • Fixed focus analysis of wafers 12,16 • Wafer 12 = PEB 8 • Wafer 16 = PEB 7 • The data has been modeled for across wafer variation • Residuals to the wafer model illustrate the anticipated, non-PEB influenced performance • Statement based upon expected whole-wafer variation of PEB temperature • The last slide touches on Wafer 13 & 17 • These are FEM arrays and warrant further study. LithoWorks PEB - Two plate study

  3. Initial Observations • PEB Thermal Analysis • The Bake cycle was examined as a function of: • Time-Temperature curve • Time-temp variations across wafer. • Total energy (integrated time * temperature) delivered to the wafer • Energy variation across wafer due to non-uniform heating. • PEB 7 is more uniform than PEB 8 • Not observed in the temperature or the total energy delivered • Can be seen in the plots of temperature variation from wafer mean over time and in the Energy Variation plots. • Neither bake plate is allowing enough time for the bake temperature to achieve steady state. • See slides 26 to 28 • Feature Response • Note: The On-Wafer sensor orientation has not been corrected or adjusted for this analysis. LithoWorks PEB - Two plate study

  4. Feature Response and Correlation • Feature Response • Note: The On-Wafer sensor orientation has not been corrected or adjusted for this analysis. • Examined wafers 12 (PEB 8) and wafer 16 (PEB 7) • Each feature’s variation was modeled for whole-wafer variations • Wafer-model should correlate to PEB energy variations • Residuals to wafer model should be approximate equal in response • if both wafers were exposed on same scanner • Residuals to wafer model should show exposure tool performance. • MSE Behavior • Differs significantly for Vertical (group 1) and Horizontal (group 2) features. • May be the result of scanner slit vs scan sensitivity of feature edges. • May also be from metrology tool algorithm. • There is no strong and obvious visual correlation of PEB energy and feature response. • There is a suggestion of PEB energy variation and SWA • Further studies • More thought must be given to these correlations. • FEM wafers need to be studied. LithoWorks PEB - Two plate study

  5. PEB #7 LithoWorks PEB - Two plate study

  6. PEB #7 overview • Left graphic • Details location of sensor points • Right graphic • Summary of rise/fall times vs temperature LithoWorks PEB - Two plate study

  7. Sensor variation from wafer mean • Each site contains a plot of delta-temp versus time • Area • product of (degrees * seconds), summed over all sites. This is proportional to the energy entered into the wafer during the bake. • Area Variance • Energy variation across the wafer • Summed deg-sec’s over all sites reporting total variation from mean-temperature over time. LithoWorks PEB - Two plate study

  8. Corresponding points on the graph • Moving the mouse to a point on the temp-time curve will highlight the corresponding points on the delta-temp wafer plot (50.1 sec, 113 C) LithoWorks PEB - Two plate study

  9. On-Wafer thermal loading? Area of sensor packet • Notice how the 7 wafer-center sites are the first to rise in temperature. • Note also the two sites located over the On-Wafer sensor packed lag in heading and also lag in cooling. This area also does not reach uniformity until the end of the heading cycle. • This is most probably due to the thermal-mass loading of the sensor packet. • The red-dot on each plot marks the same relative point on each site. LithoWorks PEB - Two plate study

  10. PEB 7; Thermal Energy Delivered • Plot of thermal area (deg-sec) across wafer. • Notice that there is a range of 168,714 deg-sec with the upper left of the wafer receiving the most energy • Thermal-package sensor area is relatively cool • No activation threshold was set for this plot thermal sensor area LithoWorks PEB - Two plate study

  11. PEB 7; Thermal Energy Delivered • Plot of area (deg-sec) integrated over time • Notice that there is a range of 168,174 deg-sec with the upper left of the wafer receiving the most energy LithoWorks PEB - Two plate study

  12. PEB 7: Thermal Energy Variance across wafer • Variation in energy (integrated temperature*time) delivered • Variation is greatest at wafer’s upper left corner, least in center & right. LithoWorks PEB - Two plate study

  13. Thermal Energy Variance Across Wafer - Contour LithoWorks PEB - Two plate study

  14. PEB 8 Data

  15. Plate PEB 8, Bake Curve • Top: PEB 8 • Bottom: PEB 7 • Curves appear very similar in shape. LithoWorks PEB - Two plate study

  16. PEB 8; Delta-Temperature Response • Same point is marked on the time-temp curve. • Distribution in upper left of wafer is now very uniform. (50.1 sec , 113 C) LithoWorks PEB - Two plate study

  17. Comparison PEB 8 vs PEB 7 • Time-Temp Area Differences • PEB 8 • has a higher energy area. • Exhibits greater excursion range and variation across the plate. PEB 8 PEB 7 LithoWorks PEB - Two plate study

  18. Comparison: Delta temperature with time • PEB 8 exhibits more variation at the bottom of the wafer. PEB 8 PEB 7 LithoWorks PEB - Two plate study

  19. PEB 8; Thermal energy delivered LithoWorks PEB - Two plate study

  20. Thermal Energy Delivered – Bake 8 Contour LithoWorks PEB - Two plate study

  21. PEB 8 Thermal Energy LithoWorks PEB - Two plate study

  22. PEB 8; Thermal Energy Variation LithoWorks PEB - Two plate study

  23. Comparison: Thermal Energy Delivered – PEB 8/ PEB 7 • Both wafers as plotted on the same scale. • More thermal energy delivered to PEB 7 PEB 8 PEB 7 LithoWorks PEB - Two plate study

  24. Thermal Energy Variation – Bake 8 Contour • Energy delivered as a delta from the wafer average temperature. • Energy = Sum((Temperature-Activation Temp.) * DeltaTime) • DeltaTime = time interval of sample LithoWorks PEB - Two plate study

  25. PEB 8: Greatest variation in thermal energy LithoWorks PEB - Two plate study

  26. Comparison: Thermal Energy Variation – PEB 8/ PEB 7 • Scales vary but characteristic is same • PEB 7 has has significantly better energy uniformity PEB 8 PEB 7 LithoWorks PEB - Two plate study

  27. Comparison energy variation statistics • PEB 8 exhibits • A greater mean temperature, range and variance of temperature than PEB 7 PEB 8 PEB 7 LithoWorks PEB - Two plate study

  28. PEB 8/ PEB 7; thermal variation • PEB 8 and 7 variations plotted to the same scale. PEB 8 PEB 7 LithoWorks PEB - Two plate study

  29. Thermal range study Bake8 • Temperature range about the average temperature of the wafer at each time-slice. • The cycled-temperature rose a total of 98.07 degrees. • Steady state uniformity is 0.18 degree across wafer. • Notice that the wafer at 121 degrees (max. temp at 134 sec.) did not reach steady-state uniformity. LithoWorks PEB - Two plate study

  30. Thermal range study Bake7 • Same study with PEB 7 • This study shows a red square at each transition start/stop point on the curve. LithoWorks PEB - Two plate study

  31. Range Uniformity Summary • Plots exhibit the thermal range across the wafer at each time-slice • Both plates exhibit the same steady-state thermal resolution. • Thermal range and maximum temperatures differs by approximately one degree • Neither plate reaches steady state while at the maximum temperature. • Bake 8 has • greater across-wafer variations (9.6 v 7.0 degrees) • Greater range at the final temperature (0.9 v 0.6 degree) • Smoother cooling curves than 7 • Near identical rise/cool thermal slopes and time at the maximum temperature compared with Bake 7 • Conclusion: Bake 8 has more thermal variation across the wafer. Bake 8 Bake 7 Bake 8 LithoWorks PEB - Two plate study

  32. Thermal Uniformity at any point in time • Generate single or matrix graphics of all of the plots. • A “movie” video will also be added to allow you to watch wafer heating. LithoWorks PEB - Two plate study

  33. PEB 8 – Steady State Temperature LithoWorks PEB - Two plate study

  34. PEB 8 Steady State Temp LithoWorks PEB - Two plate study

  35. Thermal changes during the up-ramp LithoWorks PEB - Two plate study

  36. CD data review

  37. Data Setup and Organization Wafer 12: processed on PEB plate 8, const. exp/focus 18.5/0 Wafer 13: processed on PEB plate 8, FEM 18.5/0 +- 0.5/0.05 Wafer 16: processed on PEB plate 7, const. exp/focus 18.5/0 Wafer 17: processed on PEB plate 7, FEM 18.5/0 +- 0.5/0.05 • The measurements are taken on a nominal 150:150 grating, • somewhat overexposed here (~140nm average linewidth). • All wafers have PAB step on plate 1, also attached. • For the PEB data, there are several measurements for each plate, each corresponding to a different orientation of the sensor wafer. • '3_oclock', for example, means that the wafer module is at the 3o'clock position relative to the cassette. • 1-2 o'clock is the position between 1 and 2, which appears to be 3/4 of a full rotation from the orientation of the process wafer when it's on the PEB plate-since OnWafer formats the data such that the module is situated at 3 o'clock, this means we just have to rotate the 1-2 data 180 degrees and should have the right orientation. • Within the Nanometrics data set, there are two "groups" of data for each wafer • group 1 corresponds to measurements made on gratings with lines of vertical orientation • group 2 corresponds to the horizontal orientation. LithoWorks PEB - Two plate study

  38. Wafers 13,15; Assumed Dose and Focus layout • Wafers 12 & 16 are fixed focus/dose LithoWorks PEB - Two plate study

  39. MSE behavior (12 & 16) • MSA can be used to determine the measurement quality • Variation is in fact a little better for the FEM wafers than the fixed exposure. • Probably due to the bi-modal distribution of the fixed-exposure data. Layout, all sites LithoWorks PEB - Two plate study

  40. MSE; Wafer 12 (PEB 8) • Horizontal and vertical features are responding differently to MSE LithoWorks PEB - Two plate study

  41. Wafer 12, TCD (fixed focus, Group #1) • Vertical Features All features LithoWorks PEB - Two plate study

  42. Wafer 12, TCD group 2 (Horizontal) • Field layout is shown on the left. LithoWorks PEB - Two plate study

  43. Wafer #12 –T3 (PR) Group 1 • Photoresist thickness behaves quite differently for vertical vs horizontal feature orientation. Group 2 LithoWorks PEB - Two plate study

  44. Wafer 12, BCD • Have about 3 nm of difference in mean values. • Range of values is the same to within 0.7 nm LithoWorks PEB - Two plate study

  45. Wafer #12, BCD Residuals to Wafer variation • Aberrations of scan or slit are influencing the CD variation • Left = vertical features so edges are influenced by the scan • Right = horizontal features so there is more slit influence. LithoWorks PEB - Two plate study

  46. Wafer 12; SWA LithoWorks PEB - Two plate study

  47. Wafer #12; SWA Residuals to wafer model • The horizontal line behavior (right) is very surprising. • Metrology Algorithm? LithoWorks PEB - Two plate study

  48. Wafer #12 model; BARC T2 • Good, repeatable to about 0.1 nm LithoWorks PEB - Two plate study

  49. Wafer #12; BARC residuals • Vertical features (#1) have characteristic ring. Ring is not as evident in the horizontal features on the left. • Scale on left is wider because of the difference in noise. LithoWorks PEB - Two plate study

  50. Wafer #16 (PEB 7)

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