weiring analysis process window analysis dataset:several involving 1:1, 1:2 and 1:3 duty cycles...

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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 18011

610 682 [email protected]

October 17, 2002

Sept. 2003 Weir PW Page -2-TEA Systems Corp. Confidential

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• 87-90 degrees sidewall angle• 220-240 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.


Process Window Summary

• Results for one site per field • Five sites per field


Process Window Specs

Variable TCL UCL LCLT3 (nm) 190.0000 195.0000 180.0000SWA (°) 85.0000 87.0000 84.0000BCD (nm) 100.0000 105.0000 95.0000

1:3


1:2


1:1 Sections

• 1:1 data slide 7



• Additional surface plots slide 54


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/.05CD Target 100nm 1:1


1:1 Data RangesT2 (nm) T3 (nm) MSE BCD (nm) SWA (°) TCD (nm) Z(µm)

Count 225 225 225 225 225 191 225Mean 65.4 216.6 42.2 148.7 79.7 83.3 -173.4

Median 53.8 230.3 125.9 145.6 78.0 81.8 -173.4SEM 0.7 1.2 4.8 2.4 0.3 0.6 0.0

Maximum 74.2 262.7 251.1 200.0 85.9 113.8 -173.1Minimum 33.5 197.9 0.8 91.1 70.1 49.9 -173.6

Range 40.6 64.8 250.2 108.9 15.9 63.9 0.5MinMax 74.2 262.7 251.1 200.0 85.9 113.8 -173.6

Variance 115.9 338.4 5136.9 1295.9 15.7 70.1 0.0StDev 10.8 18.4 71.7 36.0 4.0 8.4 0.1

Mean+3Sigma 97.7 271.8 257.2 256.7 91.6 108.4 -173.7SS 988516.3 10635446.9 1550645.5 5265700.3 1433907.3 1338203.4 6764856.1

Sum 14716.5 48743.4 9486.5 33458.5 17939.8 15907.6 -39014.0RMSS 66.3 217.4 83.0 153.0 79.8 83.7 173.4


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.


MSE variation

• Model fit errors (MSE) increase dramatically above 30 mj

Dose


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

T2 (nm) T3 (nm) MSE SWA (°) BCD (nm) TCD (nm) Z(µm) Family Focus DoseT2 (nm) 1.0000 -0.7116 0.2310 0.1581 -0.5162 -0.2527 -0.0314 0.0000 0.0809 0.6036T3 (nm) -0.7116 1.0000 0.4780 -0.4232 0.1134 -0.4368 0.0222 0.0000 -0.0766 -0.2234MSE 0.2310 0.4780 1.0000 -0.4970 -0.4184 -0.9619 0.0152 0.0000 -0.0709 0.3996SWA (°) 0.1581 -0.4232 -0.4970 1.0000 -0.5316 0.3887 -0.0093 0.0000 0.3146 0.3507BCD (nm) -0.5162 0.1134 -0.4184 -0.5316 1.0000 0.5562 0.0099 0.0000 -0.1259 -0.8770TCD (nm) -0.2527 -0.4368 -0.9619 0.3887 0.5562 1.0000 -0.0101 0.0000 0.1569 -0.5635Z(µm) -0.0314 0.0222 0.0152 -0.0093 0.0099 -0.0101 1.0000 0.0000 -0.0205 -0.0205Family 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1.0000 0.0000 0.0000Focus 0.0809 -0.0766 -0.0709 0.3146 -0.1259 0.1569 -0.0205 0.0000 1.0000 0.0000Dose 0.6036 -0.2234 0.3996 0.3507 -0.8770 -0.5635 -0.0205 0.0000 0.0000 1.0000


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


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. We’ll see why in the next few slides.


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


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


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.


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


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


Problem: 1:1 Horizontal

• Window for 5 sites across field don’t 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


24B2- 1:1 Vertical Features

• 205<T3<230

• 82<SWA<92

• 95<BCD<105


Problem: 1:1 Vertical

• Window for 5 sites across field don’t 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


WF#'s 50G4, 46E4: E = 18/1mJ, F = -0.1/.05CD Target 100nm 1:2

+/5% in bottom CD87-90 degrees sidewall angle

220-240 nm resist (t3) thickness


1:2 Data Ranges - 50G4H

• From the Weir Information spreadsheet• Spec

100 +/5% in bottom CD 87-90 degrees sidewall angle 220-240 nm resist (t3) thickness

T2 (nm) T3 (nm) MSE BCD (nm) SWA (°) TCD (nm) Z(µm)Count 225 225 225 225 225 220 225Mean 72.95 199.98 13.89 93.80 86.22 68.78 -174.20

Median 75.71 220.22 251.10 90.10 84.05 62.60 -174.10SEM 0.05 0.70 2.33 1.50 0.07 1.11 0.01

Maximum 79.19 262.70 496.66 132.75 88.79 101.50 -173.80Minimum 72.22 177.74 5.53 47.44 79.31 23.70 -174.40

Range 6.97 84.96 491.13 85.31 9.48 77.80 0.60MinMax 79.19 262.70 496.66 132.75 88.79 101.50 -174.40

Variance 0.60 109.68 1222.42 505.72 1.03 271.51 0.01StDev 0.77 10.47 34.96 22.49 1.01 16.48 0.11

Mean+3Sigma 75.27 231.39 118.78 161.26 89.27 118.21 -174.53SS 1197577.06 9022396.52 317234.43 2092835.15 1673049.28 1100211.45 6828120.02

Sum 16414.16 44994.57 3125.35 21104.49 19400.62 15131.59 -39196.00RMSS 72.96 200.25 37.55 96.44 86.23 70.72 174.20


MSE measurement error

• Errors range greatly with the greatest being at the –1 focus (top) and low energy (left) side of the wafer


BCD v Dose

• Target is 100 nm


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.


• 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


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)


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 0.125 um and a dose of 20.7 mj Only examines the field center test site #5

Field Sites: 5, Variable TCL UCL LCLT3 (nm) 210.0000 220.0000 195.0000SWA (°) 86.0000 87.0000 85.0000BCD (nm) 100.0000 105.0000 95.0000

IsoFocal Dose: T3 (nm) Site: 5 17.97 mjIsoFocal Dose: SWA (°) Site: 5 19.08 mjIsoFocal Dose: BCD (nm) Site: 5 16.71 mj

____ Results ____PW Rectangle:...Best Focus 0.1250...Dept of Focus 0.2100...Best Dose 20.7000...Dose Latitude % 2.9000

PW Ellipse:...Best Focus 0.1000...Dept of Focus 0.2800...Best Dose 20.6000...Dose Latitude % 1.9418


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


PW 50G4 1:2H – 5 points X

• Dof is about the same but the Dose Latitude is reduced.

• Major influence is the BCD variance.


50G4 -1:2 H 5 Points PW summaryLot Name: 50G4__1_2H

03-Oct-03 - 08:26 AM

Data Culling...Variable: MSE.....Max: 20.0000.....Min: 5.5309Removed: MSE ... Points removed: 2...Range: 0.0000...Sigma: 0.0000

Exposure Range...Dose: 18.0000 24.0000...Focus: -0.1000 0.2000

# Points: 217.0000

Process Window Setup

Field Sites: 1, 2, 3, 4, 5, Variable TCL UCL LCLT3 (nm) 210.0000 220.0000 195.0000SWA (°) 86.0000 87.0000 85.0000BCD (nm) 100.0000 105.0000 95.0000

IsoFocal Dose: T3 (nm) Site: 1 18.49 mjIsoFocal Dose: SWA (°) Site: 1 16.60 mjIsoFocal Dose: BCD (nm) Site: 1 13.71 mjIsoFocal Dose: T3 (nm) Site: 2 15.12 mjIsoFocal Dose: SWA (°) Site: 2 18.47 mjIsoFocal Dose: BCD (nm) Site: 2 16.09 mjIsoFocal Dose: T3 (nm) Site: 3 17.99 mjIsoFocal Dose: SWA (°) Site: 3 19.16 mjIsoFocal Dose: BCD (nm) Site: 3 16.89 mjIsoFocal Dose: T3 (nm) Site: 4 20.08 mjIsoFocal Dose: SWA (°) Site: 4 15.14 mjIsoFocal Dose: BCD (nm) Site: 4 8.51 mjIsoFocal Dose: T3 (nm) Site: 5 17.97 mjIsoFocal Dose: SWA (°) Site: 5 19.08 mjIsoFocal Dose: BCD (nm) Site: 5 16.71 mj




Vertical 1:2 50G4_VxOne point – field center

Data on right is from the “Process Window” spreadsheet

Resist thickness centers about 195 to 210 nm

Lot Name: 50G4__1_2V03-Oct-03 - 07:38 AM



# Points: 44.0000







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.


Vertical 1:2 50G4_V – 5 sitesX

• Results summary for five sites in field from the Weir “Process Window” spreadsheet



# Points: 216.0000







50G4 1:2 Vertical Lines – MSE X

MSE, Metrology measurement error


46E4_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


46E4_1:2H Center Field Site PW

Lot Name: 46E4__1_2H03-Oct-03 - 09:50 AM

Data Culling...Variable: None...Range: 0.0000...Sigma: 0.0000


# Points: 45.0000







46E4_1:2H – 5 points in field


46E4_1:2H – 5 points -SummaryLot Name: 46E4__1_2H

03-Oct-03 - 10:38 AM

Data Culling...Variable: None...Range: 0.0000...Sigma: 0.0000


# Points: 225.0000







46E4_1:2Vertical – Field Center

Data Culling...Variable: MSE.....Max: 20.0000.....Min: 4.4411Removed: Variable...Range: 0.0000...Sigma: 0.0000


# Points: 45.0000







46E4_1:2Vertical – five points


46E4_1:2Vertical – summary



Lot Name: 46E4__1_2V03-Oct-03 - 11:08 AM



# Points: 224.0000





Duty Cycle 1:3 data


38F7_3H Horizontal Field CenterLot Name: 38F7__1_3H

03-Oct-03 - 08:18 AM

Data Culling...Variable:MSE.....Max: 8.0000.....Min: 0.4655Removed: MSE ... Points removed: 4...Range: 0.0000...Sigma: 0.0000


# Points: 41.0000


Field Sites:5, Variable TCL UCL LCLT3 (nm) 190.0000 195.0000 180.0000SWA (°) 85.0000 87.0000 84.0000BCD (nm) 100.0000 105.0000 95.0000


38F7 1:3H Problem with T3 at Site 1


38F7 1:3H Problem with T3 at Site 1

• Problem is for data from Focus = -0.1, -0.05 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 We’ll restrict the PW analysis for this setup

FocusT3 (nm) Dose 21 Dose 22

0.2 174.720.15 182.83 179.36

0.1 182.93 179.110.05 182.8 178.82

0 179.57 175.21-0.05 170.97 286.07

-0.1 285.71


38F7_3:1H restriction method

• We’ll use the variable cull method. This removes 2 points as

shown above

• Response is improved considerably.

Data Culling...Variable: T3 (nm).....Max: 230.0000.....Min: 168.7800Removed: T3 (nm) ... Points removed: 2...Range: 0.0000...Sigma: 0.0000


38F7 1:3H – 5 points


38F7 1:3H – 5 points summaryLot Name: 38F7__1_3H

03-Oct-03 - 09:49 AM



# Points: 212.0000




PW Rectangle:...Best Focus 0.1675...Dept of Focus 0.0750...Best Dose 18.8000...Dose Latitude % 2.1300



38F7_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


38F7_1:3Vertical - Center Field

Data Culling...Variable: T3 (nm).....Max: 200.0000.....Min: 175.0000Removed: Variable...Range: 0.0000...Sigma: 0.0000


# Points: 40.0000







38F7_1:3Vertical – 5 points


38F7_1:3Vertical – 5 points Summary

Lot Name: 38F7__1_3V03-Oct-03 - 10:50 AM



# Points: 187.0000




PW Rectangle:...Best Focus 0.1500...Dept of Focus 0.1300...Best Dose 18.9000...Dose Latitude % 1.0600



Across wafer modeled SWA

• Major modeled SWA variation across wafer with dose and focus


Modeled BCD variation


Residuals to Modeled BCD

• Now we can see the change across the field without the direct influence of focus and dose.


BCD Variation on field by row location

With more points per field, we could see the scan and

slit variation across the exposure field.

weiring analysis process window analysis dataset:several involving 1:1, 1:2 and 1:3 duty cycles...

Documents

weir pwpage

t3 resist bcd slide

mj dose slide

field slide

resist thickness t3

t3 resist thickness

nm resist t3 thickness

bcd t3 resist t3 values