Weiring Analysis Process Window Analysis Dataset:Several involving 1:1, 1:2 and 1:3 duty cycles Features:Focus Dose Matrix and Process Window Analysis TEA Systems Corp. 65 Schlossburg St. Alburtis, PA October 17, 2002

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -2- Project Summary Program:Weir Family of products Situation: ?Several FEM wafers were measured using tool. This data is coded as follows: WF#'s 24B2, 54A0: E = 26/1mJ, F = -0.1/.05 CD Target 100nm 1:1 WF#'s 50G4, 46E4: E = 18/1mJ, F = -0.1/.05 CD Target 100nm 1:2 WF#'s 38F7, 74E6: E = 16/1mJ, F = -0.1/.05 CD Target 100nm 1:3 ?The litho stack is 770A AR40, 2200A 735 resist, and measurement was done at 5pts/fld, both vertical and horizontal. ?Use the process window analysis to take these data and extract the best dose/focus for each of the 3 pitches. ?Use the following process window to define the best dose/focus: +/5% in bottom CD degrees sidewall angle nm resist (t3) thickness Summary ?We examined data sets for the 1:1, 1:2 and 1:3 duty cycles. ?Specifications for the SWA and Resist Thickness (T3) were modified to meet the BCD standard Problems may lie in the targets or in the metrology software algorithms. Non-continuous variation of SWA and T3 (resist) thickness along the focus-dose matrix suggest the problem may be with the metrology algorithm. ?Site locations on the field do vary, but all data had five points per field.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -3- Process Window Summary Results for one site per fieldFive sites per field

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -4- Process Window Specs 1:3 1:2 1:1 Sections 1:1 dataslide 7 1:2 dataslide 21 1:3 dataslide 43 Additional surface plotsslide 54

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -5- Focus & Dose Layout Focus Dose Field Layouts

TEA Systems Corp. Confidential 1:1 Duty Cycle, Dense Lines WF#'s 24B2, 54A0: E = 26/1mJ, F = -0.1/.05 CD Target 100nm 1:1

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -7- 1:1 Data Ranges

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -8- BCD Range Target value for BCD Dose is 100 nm ?Only being achieved up at 32 mj for the 1:1 isolated target structures ?The dose range > 30 mj is the area where the metrology MSE is greatest.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -9- MSE variation Model fit errors (MSE) increase dramatically above 30 mj Dose

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -10- SWA and Focus Examination of the focus data shows SWA having the strongest relationship. ?Plot above shows SWA and it median and 20%/ 80% contours of the populations We also see covariance between SWA and T3 (Resist) & BCD

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -11- BCD & T3 (Resist) T3 values change linearly. ?There is a region in which values are bimodal from 74 to 80 deg. BCD strongly changes as CD size drops below 190 nm ?Target is about 100 nm, this implies that the model may be wrong since we see a discontinuity in SWA in the BCE = 110 to 90 nm region

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -12- Parameter setup Because of the range restrictions shown in the previous slides we changed the PW centering to: ?Window for SWA was modified to 84 deg. ?Window for BCD was increase set 100 nm (delta 5%) ?T3, Resist thickness was also set per the spec NOTE: There is no common process window for these specs for the 1:1 dense lineNOTE: There is no common process window for these specs for the 1:1 dense line. ?Well see why in the next few slides.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -13- Resist (T3) thickness and Focus Plotted is the resist thickness (T3) for sites #2 and #5 (shown on inset). Spec is 220<T3<240 Notice the bimodal performance with proper thickness only at the 31 and 32 mj levels Graph on right shows T3 boxplot of population with 20%, 50% & 80% population contour lines

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -14- Process Window for BCD and Resist (T3) This spec for the isolated line results in a very small process window ?Note we used T3=240 nm and BCD=100 nm ?SWA was not included ?Used only two sites on the field, #2 and #5 (shown previous slide

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -15- SWA spec 87 to 90 deg The SWA never quite gets to the spec. SWA even seems drop for the 31,32 mj doses As a result, there is no common process window if SWA is included.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -16- Horizontal 1:1 process window 82<SWA <92 ?Spec drives process window to zero. ?Need to lower SWA spec T3=200 T3=220 T3=230 BCD Window Swa = 82

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -17- Correct Horizontal 1:1 features Horizontal 1:1 feature correct process window ?SWA values had to be essentially ignored. NOTE: Field Center Site Only T3=200 SWA=78

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -18- Problem: 1:1 Horizontal Window for 5 sites across field dont overlap. Since sites 1& 4 are located at the bottom of the field ?the problem could be with the reticle or with the exposure scan Sites #1 & 4 Sites #2,3 & 5 #1 #2 #5 #3 #4 Lot 24B2Lot 54A0

TEA Systems Corp. Confidential Sept. 2003Weir PWPage B2- 1:1 Vertical Features 205<T3<230 82<SWA<92 95<BCD<105

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -20- Problem: 1:1 Vertical Window for 5 sites across field dont overlap. Since sites 2 & 3 are located at the top of the field ?the problem could be with the reticle or with the exposure scan Sites #2 & 3 Sites #1,4 & 5 #1 #2 #5 #3 #4

TEA Systems Corp. Confidential WF#'s 50G4, 46E4: E = 18/1mJ, F = -0.1/.05 CD Target 100nm 1:2 +/5% in bottom CD degrees sidewall angle nm resist (t3) thickness

TEA Systems Corp. Confidential Sept. 2003Weir PWPage :2 Data Ranges - 50G4H From the Weir Information spreadsheet Spec ?100 +/5% in bottom CD ?87-90 degrees sidewall angle ? nm resist (t3) thickness

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -23- MSE measurement error Errors range greatly with the greatest being at the –1 focus (top) and low energy (left) side of the wafer

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -24- BCD v Dose Target is 100 nm

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -25- Resist (T3) v Dose Target is 220 to 240 nm so we will not reach Process window on this variable. BoxPlot population contours are at 10, 50 & 90% levels.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -26- There is a small change in SWA with focus The primary response is the spread of measurements with focus This is data for all five points in the field. ?The spec of 87 to 90 deg. Is never reached. SWA v Dose

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -27- Setup and data culling – 50G4_H 1:2 Based on the previous slides data, we set the BCD, SWA and T3 as shown Data culling used the MSE variable with a maximum allow value of 20. ?This is shown to have removed 2 data points (upper right figure)

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -28- Process Window 50G4_H 2:1 X Process window has 0.21 um Depth of focus and a dose latitude of 2.9% ?Window center: Best focus at um and a dose of 20.7 mj ?Only examines the field center test site #5

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -29- Exposure latitude and DoF Depth of focus does not change significantly for increased exposure latitude but there is not much there to start with. 50G4_H

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -30- PW 50G4 1:2H – 5 points X Dof is about the same but the Dose Latitude is reduced. Major influence is the BCD variance.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage G4 -1:2 H 5 Points PW summary

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -32- Vertical 1:2 50G4_Vx One point – field center Data on right is from the Process Window spreadsheet Resist thickness centers about 195 to 210 nm

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -33- Vertical 1:2 50G4_V – 5 sitesX Field layout is shown above Five sites selected along with previous specs for SWA and Resist (T3) ?SWA spec was widened to allow overlaps.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -34- Vertical 1:2 50G4_V – 5 sitesX Results summary for five sites in field from the Weir Process Window spreadsheet

TEA Systems Corp. Confidential Sept. 2003Weir PWPage G4 1:2 Vertical Lines – MSE X MSE, Metrology measurement error

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2H Response items MSE is very uniform with dose so it will not be a good culling factor with this data set. SWA varies from 84 to 89.6 degrees and is influenced by both dose and focus

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2H Center Field Site PW

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2H – 5 points in field

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2H – 5 points -Summary

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2Vertical – Field Center

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2Vertical – five points

TEA Systems Corp. Confidential Sept. 2003Weir PWPage E4_1:2Vertical – summary

TEA Systems Corp. Confidential Duty Cycle 1:3 data

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7_3H Horizontal Field Center

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7 1:3H Problem with T3 at Site 1

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7 1:3H Problem with T3 at Site 1 Problem is for data from Focus = -0.1, um for dose >20 mj ?The focus value can be seen by hovering the mouse over the two points circled on the Dose plot ?Data view is shown to the right ?Well restrict the PW analysis for this setup

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7_3:1H restriction method Well use the variable cull method. ?This removes 2 points as shown above Response is improved considerably.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7 1:3H – 5 points

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7 1:3H – 5 points summary

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7_1:3Vertical - Resist (T3) gating MSE seems to vary more at the lower doses However, T3 again is the gating variable particularly here at the 1:3 grating

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7_1:3Vertical - Center Field

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7_1:3Vertical – 5 points

TEA Systems Corp. Confidential Sept. 2003Weir PWPage F7_1:3Vertical – 5 points Summary

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -54- Across wafer modeled SWA Major modeled SWA variation across wafer with dose and focus

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -55- Modeled BCD variation

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -56- Residuals to Modeled BCD Now we can see the change across the field without the direct influence of focus and dose.

TEA Systems Corp. Confidential Sept. 2003Weir PWPage -57- BCD Variation on field by row location With more points per field, we could see the scan and slit variation across the exposure field.