Yield Enhancement thru Modeling TEA Systems TEA Systems Confidential & Proprietary Copyright © 2007...

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TEA Systems Confidential & ProprietaryCopyright © 2007 TEA Systems Corp.

Advanced Overlay Analysis & Modeling Model raw data for each structure separately Remove outliers by using the model

Use at most a second order polynomial? Use 3 sigma or the range from the population median as a control threshold

Agenda Interface Overview Spatial model generation & graphics

“What-if” scenario Graph generation using mouse selection

Vector Raptor Excel Workbook Data Storage Data Storage Organization Example Reports

Interactive graph customization Radial Wafer Analysis & Radial Culling Multi-Pattern Lot Splits (Families)

Results by family Reports & mouse generated graphics

Model Editor

Vector Raptor



Concept

Vector Raptor; Classic Overlay Modeling Employs all classic models for stepper & scanners WITH additional sophistication in:

Graphics & control Analysis Portability Results reporting Ability to apply models to whole field, row (reticle scan response) and column (scan-slit response)

Advanced Features Proprietary modeling engine using adaptive model elements and singular value decomposition

Models adaptive to both singularities and fit-culling Multi-level, automate and manual methods for data culling Multi-Family Analysis

For true overlay-structure and pattern-split analysis Error Source Discrimination

Ability to resolve error sources from between: Process Wafer-chuck Field Reticle Scan Lens Slit



Poly DP Solution

193i – 1.2 NA

X-Y Polarized light

K1 = 0.28Pitch 90 nm

Double Patterning (DP) is a split of the pattern layers to provide sub-0.45 nm lithograph

Double Patterning can actually be more than two splits

Situations are envisioned of up to five (5) patterned splits that must each undergo multiple alignment, exposure, develop deposition and etch steps.



Double Patterning Concepts

“Double Patterning” Actually adds multiple alignment and process levels for each split

Mask Critical Overall mask registration errors will be critical:

Alignment accuracy to scanner registration marks for the layer Overall mask magnification, uniformity, rotation and skew will become more

critical Processing

Variations in processing can influence not on CD size but the mask response to lens aberrations when wafer is exposed Greater or less sensitivity to variation in focus, polarization and dose

Process Critical Alignment sensitivity of the scanner to the registration on the mask Mask bow/distortion while mask is chucked varies from scanner to scanner Overlay distortion across a single field is now sensitive to lens-placement

distortions from tool response to Dose and deFocus Problems will exist in trying to understand the sources of these overlay errors

due as they vary across the finished device layer.



Vector Raptor Interface

Vector Raptor is an engineering interface May be used with Weir DM

for script automation of any engineering analysis

Data Data is stored in the TEA

Standard metrology format Microsoft Excel

Workbooks are used for data storage “VR Workbooks”

Any metrology may be imported and stored into VR Workbooks

Reports etc. All reports, analyses and

extractions are stored in the VR data workbook.

Microsoft Windows XP, 2000, 2004 Server etc.



Vector Raptor Button Bar

Model Editor Create and/or modify substrate and field surface models

Layout Editor Enter exposure information for each die including focus, dose, NA, Sigma and reticle scan direction Adjust wafer size, die size, offset, notch etc.

Active Workbook By default this is the metrology data workbook Analyses and modeling generate additional data that can also be analyzed and graphed

Import Metrology Data

Load Workbook Data

Print screen

View current data in workbook format Copy Screen

Copy Graphic only

Model Editor

Layout Editor

Variable Under Analysis

Family Member Selection

Active data worksheet in workbook



Loading Data

With Vector Raptor Load RV Workbooks directly Import any metrology data Drag & drop any ASCII or

workbook into the interface

With Daily Monitor analysis using Vector Raptor models & methods Load data directly Drag & drop Load data, and start analysis,

using calls from external programs

Drag & drop with mouse

Data Import



Data Selection & culling

Field Layout

Wafer Layout

“Field Sites” data sheet

• Exposure Subset Selection for:

• Wafer

• Focus Dose

• Reticle Scan direction

• NA

• Partial Coherence (Sigma)

• Exposure Subset Selection for:

• Wafer

• Focus Dose

• Reticle Scan direction

• NA

• Partial Coherence (Sigma)

Data culling by variable

range

‘one-click’ histogram for range selection aid



Data Culling & Sub-Set Plotting

Box-in any set of data during selection With ‘wafer’ you can plot or cull individual data points With the ‘field’ plot on left, you can remove selected ‘sites’ on the field

Mouse-box



Spatial Models

Raw Data analysis of wafer & field Mouse-sensitive data

viewing/graphing

Histogram of corner site dataCreated by boxing in site with mouse



Contour & 3D plots



1-D Vector Plots



Wafer & Field Modeled results

Apply models as needed

Perform “What-if” scenarios for terms

Colored vector-amplitude can be switched off



“What-if” Scenarios

Left – full-field model Each field individually modeled & results plotted

Right- response with “Piston” or the “offset” removed.

Note: for this example the field model used here is a simple A +Bx –Cy –DX2 –EY2

And does not represent any valid overlay model.For demo purposes only



Scale change

Vector-scale, as shown or Magnitude bar-scale can be

changed independently



Graph Generation using mouse

Mouse hovered over point to see data value

Use mouse to graph, delete or spreadsheet-view a section of data



Interactive Index Sheet for data workbook



Detailed field-by-field aberrations



Field Response Report



Graph interface for customization

XY line graphs can also Create box-plots Population-density plots Fit general polynomial trend-

lines Add comments & messages Rescale with the mouse or by

this interface Etc.



Field Sites with “split” families

http://www.TEAsystems.com


Radial Wafer Analysis & Radial Culling



Cull Radius control

Data sets of over 22,000 data sites have been measured



Radial Analysis

Press the “cull radius” command button

Screen appears Graphic & report generated



Population response for Range & Sigma Cull

Compares multiple “family’s” or pattern-splits

Only one shown here



Multi-Pattern Lot Splits (Families)

Lot contains data with three (3) overlay splits

Splits are defined in the single data file as different site family values.



Field Model

This summarizes all splits



Results by family

Graphs are automatically created

Fitted Range of values



Fitted Reports

Focus and Dose response can also be evaluated



Modeled X & Y overlay split response across wafer

Response across wafer



Model Editor

Vector Raptor comes with standard ASML, Nikon and CANON models

User customization and model additions are performed using the Model Editor



Models Editor



Precision & Covariance



Overlay Precision Analysis



Covariance

Covariance chart in workbook shown



X-Y Covariance plot

First order fitted line (red) and fit-polynomial message added by graph editor



U7 Overlay wafer & field model



Wafer model

Wafer offset not included



Wafer (Process) Modeled Errors



Field Component



Field Mag, rotation & trap



Field Mag, Rot & Trap



After data point removal

14,861 data points ASML XT1400 XYSMO data



X & Y Overlay

X and Y overlay Note center-of-wafer “hot”

spot



Model Editor

Any number of sequential models• Model coefficients are

summarized into one algorithm for each sub-model

Coefficient Control Area• Display name is used in reports• Units-of-measure

• Select from drop-down or enter any format such as “nm/cm2” or “ergs/mm2” or ppm etc.

• Equation can use any format with variables “X,Y,R and Theta”

• Threshold = number of points that must be in the data to use this coefficient

• Control bar allows individual coefficient to be created, copied, pasted, deleted or moved up/down in the analysis.

This analysis shows three wafer-based models available for analysis from the library. User can add/delete models

Field models can be seen if the user clicks on the field



Excluded data points

Registration/overlay data excluded by ASML.



Wafer Model



Wafer Residuals



Field Residuals



Fitted Field values



Full field model, trap & wedge contribution

Note that lower row on each field is changing X direction

Noise in scan-start/end



X-Reg, Trapezoid & Wedge

Wafer #1 Wafer #2 Wafer #3



Xreg, Trap2 (X*Y)



Wafer #2 Fitted errors without offset



Wafer #2, Trapezoid



Wafer #2, field rotation



Rotation: Field and Scan-Slit

Scan-Slit Rotation Field Rotation



Field Rotation Analysis

+ =

X-Rotation varies by 2 nm from field-to-field.

Y-Rotation varies by 5 nm

X-Rot

Y-Rot

+ =

X-Rotation varies by 2 nm from field-to-field.

Y-Rotation varies by 5 nm

X-Rot

Y-Rot



Mag, Rotation, Trap & Wedge

Double -Pattern Overlay

Field & Lens Slit Rotation Component

Modeled X-Registration for Trap & Wedge

Modeled Comonent Analysis



Raw vectored data and sites on field

Total of 14,918 sites

20 sites excluded by culling (> 10 nm error)



X & Y offset

Y-reg alignment error

Process error in both X & Y

Fine-structure rib variation of 3-5 nm due to reticle-scan



Wafer Model, magnitude variation



Wafer-modeled X overlay



Residuals to wafer model, X-overlay

Note cycle every 4 mm on scan

Variation along a field vertical axis



X & Y Vector residuals to wafer registration



Variation across wafer diameter

Residuals to wafer model



VR Matching Interface



X-overlay at two NA settings

Yield Enhancement thru Modeling TEA Systems TEA Systems Confidential & Proprietary Copyright © 2007...

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