Weir PSFM Focus uniformity calculations for lens aberrations

Weir PSFM Focus uniformity calculations for lens aberrations, stage & scan characterization and reticle-platen tuning Weir PSFM and the Benchmark PSFM/PSG reticle form a wavefront engineering toolset unique in the industry for • critical focal-plane element analysis, • Tool control calculation, • yield estimation, • behavioral visualization and • automated modeling for capability optimization. TEA Systems Corp. Nov. 2003 Weir PSFM Overview 65 Schlossburg St. Alburtis, PA 18011 610 682 4146 TZavecz@enter. net

Weir PSFM/ Highlights Program Weir PSFM/PSG Operation Mode Engineering – analytical tools Manufacturing – Daily Monitor templates Automation – APC model engine Platform Window 2000, XP etc. Data Input Any overlay or registration metrology Automated input. Data Storage Microsoft Excel workbooks. Organization “Open” system with easy access to data and analysis results Applications Metrology verification and setup Reticle verification Exposure tool ? setup and analysis of lens, reticle-platen and wafer chuck ? Lens matching ? uniformity analysis ? Sub-system precision calculation ? focus budget optimization Process ? Optimization ? Error budget analysis ? Yield estimation Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 2

Agenda • Weir PSFM Overview • Data acquisition & setup • The three modes of operation ? PSFM & PGM Reticle Calibration ? Lens aberrations in the “Best Focus” field ? Fixed Focus analysis • Wafer and Field Modeling • Example: Astigmatism and wafer model • Resolution of topographic steps • Tool Precision calculation • Analysis Automation with Weir DM • Summary Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 3

Weir Data Import • manual data import ? Data is selected from the Weir Analysis import screen • Weir can import Binary, ASCII or Excel data formats ? The data is stored in an Excel spreadsheet. ? Weir uses user-defined variable names from the raw data set. Therma-Wave Optiprobe CD Supports any metrology data including overlay, CD, thickness etc. • “Test” numbers correlate to information shown on the “Sites” spreadsheet. • The information sheet contains additional setup parameters Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 4

Layout optimizer • Provides ? Layout fine tuning for centering and parameter updates. • Point-and-click updates of scan, NA, focus, dose coherence etc. ? Basic metrology with statistics and visualization graphics such as histograms, XY-scatter, wafer, field plots, contour and 3 D plots ? Exposure tool library maintenance and selection ? Access to Weir focus, process window and daily monitor modules. Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 5

Operational Modes Weir Software Suite • PSFM Reticle Patterns ? Perform isolated –feature based analysis • PGM or PSG Patterns ? Analyze performance for dense -packed features • Weir Calibration ? lens aberrations ? calibration templates for reticles ? tuning Nov. 2003 • Weir Fixed-Focus ? Wafer stage performance ? Slit & scan characterization ? tuning Weir PSFM Overview TEA Systems Corp. Confidential • Weir DM ? Calibration, fixed focus & raw data ? Trend charts ? Lot analysis 6

Analysis Flow - Reticle Calibration/ Calibration Template Generation: Perform one-time for a given Reticle and NA/Sigma Optional: Calculate the Calibrate the Import and “Best Focus” PSFM layout data Aerial Image Reticle response Templates are needed for each unique Reticle, NA & Sigma value used Save the calibration to a Calibration Template Library Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 7

Automated calibration of every site 2 1 3 4 1. Field object shows site layout 2. Calibration can be restricted by layout variable setup. 3. Set automated range & sigma data culling, press calibrate and every site on the reticle is calibrated. 4. Calibrations are displayed and stored in the spreadsheet. 5. Accuracy (l= 193 nm) 1. PSFM < 12 nm focus 2. PSFM < 1. 5 nm - 3 sigma Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 8

Best Focus – the lens Aerial Image 1. Most accurate calculation of lens aberrations • Piston, Tilt, Astigmatism, Curvature “What if” Simulations 2. Focus budget: • Astigmatism: 0. 034 um • After tilt & bow are accounted for • Tilt; loss of • Curvature: 0. 019 um 0. 017 um • -9 nm in X, +9 nm in Y • Residuals 0. 143 um • Residuals are also contributing to astigmatism. 3. Best Focus Setting • The best focus Tool setting is at um. Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential – 0. 042 9

Analysis Flow for Fixed Focus Reticle Calibration/ Calibration Template Generation: Perform one-time for a given Reticle and NA/Sigma Import and layout data Calibrate the PSFM Reticle Optional: Calculate the “Best Focus” Aerial Image response Save the calibration to a Calibration Templates are needed for each unique Reticle, NA & Sigma value used Template Library Fixed-Focus Analysis: Analysis Perform daily or as needed. Select “Analysis” tab to continue FOCUS analysis Nov. 2003 Import and layout data Wafer Graphic will appear to show you the focus data selected Go to Focus uniformity Analysis Window Select the proper Calibration Template Press “(re)Calculate” command button to convert overlay to Focus Weir PSFM Overview TEA Systems Corp. Confidential Select the Conversion Option. “All-Sites” is default. Optional: select data sub-set of wafer, dose, NA, PC etc values 10

Fixed Focus: Wafer & Field Modeling Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential • Wier’s Zernike wafer analysis clearly resolves the 10 urad of chuck tilt (shown here as a correction of – 10 urad) and 15 urad of reticle tilt. • Modeled results are stored in the excel spreadsheet along with the data (see below). 11

Astigmatic variation • Top – View of wafer modeled tilt & bow • Bottom, view of horizontal focus, systematic Previous Horizontal Feature plot errors. Note baseline focus drift Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 12

Residuals re-plotted Slit & scan by column Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 13

Modeled Residuals plotted by Rows plotted by Column Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 14

Tool Precision budget 1. Click on the Precision tab to calculate the precision dataset. 1. Values are displayed in “onesigma” variations. 2. Definitions & method of calculated can be viewed by pressing the F 1 key or by going into the help menu. 2. Values in the “Scan” (Y) direction varied more than along the slit (X) 3. Wafer-to-wafer or Inter. Wafer variation is small. 4. Inter. Field variation from stage stepping, leveling and focusing is greater than Intra. Field, or fixed field variation. 5. Overall lot precision is (64. 5, 85. 9) nm one-sigma. 6. Results are stored on the “Precision” spreadsheet of the workbook. Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 15

Weir DM: Analysis Automation Any analysis sequence can be automated for implementation in the production environment using the Weir Daily Monitor (DM) • Weir DM Setup Screen • entered through the Weir Engineer “Tools/Daily Monitor Setup” menu item. • Statistics displayed will be specified in the second “Graphics Display” tab. Reticle data or Component (Mean or Best Focus fields) can be removed. Nov. 2003 • Statistics and trend charts maintained are specified in the “Statistics Display” tab. Weir PSFM Overview TEA Systems Corp. Confidential 16

Running Weir DM The Weir DM is a “stand-alone” program that can also be called from the Weir Engineering interface. Current DM Templates The analysis for a calibration uses the layout specified in the template. Files in the data directory. Sorted alphabetically. Starts the calibration. • pre-selected templates in dropdown listings “One-Click” Analysis • Data files, sorted and pre-selected in a drop-down listing. Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 17

Weir DM Trend Charts • Here we observe “Mean” feature settings. Vertical (X) and Horizontal (Y) focus data can also be viewed. • The Weir DM software plots one template chart for each data variable selected. Above is shown the data for the “Mean 3 sigma statistic”. Corresponding data for the Best Focus, or data mean is shown on the right Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential Measurement date shown on the abscissa. 18

Field Focus • Field modeled best focus is changing with wafer number (right). • If we look at vertical (slit) focus, we can see the focus drift until about the 6 th wafer. • Horizontal (scan) focus remains constant. • This is consistent with lens heating effects. Average Lens (slit) focus Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential Scan focus 19

Astigmatism • Astigmatism, also sensitive to lens heating, is shown to settle after the 8 th wafer. Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 20

Summary of Weir PSFM • Any metrology data can be imported ? Weir PW contains a layout optimizer and basic metrology analysis capabilities ? Data is stored in Microsoft Excel® worksheet and workbooks • Layout of Dose, Focus, NA, PC and stage/scan direction ? Supported by graphic tools as well as simple point-and-click entry. • Modes of operation ? Calibration • PSFM/PGM reticle template generation • “Best Focus” lens aberration analysis ? Fixed-Focus • Stage and wafer-edge performance • Average or selected field analysis. • User can remove mean-field, best-focus or selected modeled aberrations prior to performing analysis. • Modeled wafer and field ? Weir DM • Automation of frequently performed Calibration, Fixed-Focus or Raw Data. • Automation ? Weir DM can be used to automate process-monitor points for any variable series. Nov. 2003 Weir PSFM Overview TEA Systems Corp. Confidential 21