Wafer scanning process traveler

The wafers used for process calibration are ordered from SVM. These are 4 inch silicon wafers with low particle count (LPD= light particle detection<100). The box with 25 wafers is stored in the cleanroom and used only for process calibration. Wafers are handled very carefully, because with every loading and unloading some particles will be added.

Scanning procedure

Scan before process calibration

1. Log in (access code is boss)
2. Load wafers(face up) to the carrier that says " SURFSCAN" .
3. Place the carrier with wafers to the right indexer.
4. In the menu option select "CAS" (this will read all wafers that are in the carrier).
5. Go to "Recipes" and load one of standard recipes.
6. Select one of the recipes:
   • UCSB Gain4 (measuring small particles 0.16-1.6um)
   • UCSB Gain2 (measuring larger particles 1.6-28um)
7. View the recipe and modify it if needed, default the bin.
8. Select the wafer you want to scan.
9. Select START.
10. Wait until scan is finished.
11. Record: LPD, particles #1, particles #8, haze region.
12. Take a picture of the scan (by phone).
13. Select "Home" so indexer moves up to loading/unloading position.
14. Unload wafers (ready for process calibration).
15. Log out.

Scan after process calibration

1. Log in (access code is boss)
2. Load wafers(face up) to the carrier that says " SURFSCAN" .
3. Place the carrier with wafers to the right indexer.
4. In the menu option select "CAS" (this will read all wafers that are in the carrier).
5. Go to "Recipes" and load one of standard recipes.
6. Select one of the recipes :
   • UCSB Gain4 (measuring small particles 0.16-1.6um)
   • UCSB Gain2 (measuring larger particles 1.6-28um)
7. View the recipe and modify it if needed, default the bin.
8. Select the wafer you want to scan.
9. Select START.
10. Wait until scan is finished
11. Record: LPD, particles #1, particles #8, haze region.
12. Take a picture of the scan (by phone)
13. Select "Home" so indexer moves up to loading/unloading position
14. Unload wafers.
15. Log out.

Plotting data

Make an excel sheet.

Enter info for Gain4 (particles#1, particles#8, LPD, haze) before and after process calibration.

Enter info for Gain2 (particles#1, particles#8, LPD, haze) before and after process calibration.

For each gain figure out delta ( LPD after- LPD before).

Make a plot delta vs. time.

Surfscan additional information

Surfscan 6200 locates, sizes, and counts defects in semiconductor substrate material down to 0.157um at a 95% capture rate and down to 0.09um at an 80% capture rate. The instrument uses laser beam scanning for detecting defect contamination and displays scan results in color-coded wafer maps, histograms, and summaries. The instrument scans wafers contained in a cassette. Cassettes can be loaded onto the left indexer, right indexer, or both indexers. Cassette configuration can be ( R only, L only, Right to left, Left to right, Sort wafers). When manually aligning wafers, one of the flats of each wafer should face the front of the cassette. When using a mechanical aligner, the flats should face the rear of the cassette. If wafers get scratched, damaged or mishandled immediately perform cassette calibration. The instrument communicates with an operator using the Microsoft Windows. To use an application, choose menus or commands displayed in the menu bar, or use keypad commands. The system menu is an icon-based menu. Double click on the application icon to start an application. In the Scan window , the menu bar displays: ID, CASS, AUTO, HOME, SAVE, and PRINT commands.

1. Log in, access code is BOSS.
2. Double click on the icon of the application to start application.
3. Log off the system, to exit the current application.
   • The Tencor Instrument banner at the top of the screen contains a disk status. If it is green the database space is available. If it is yellow, free disk or data space is getting low, so it needs to be increased free space. It is red, there is no free space.
4. Before scanning:
   • Choose the recipe to be used
   • Load the cassette of substrates onto the right locator
   • Choose scan options
   • Enter a Lot ID, if desired
5. Scanning methods:
   • One substrate-direct access( cassette) or more( AUTO)
6. Scanning options:
   • automatic or manual operation
   • scan sequence
   • microscope hold for MicroViewing
7. The recipe sets:
   • Primary data of interest ( defect or haze)
   • Initial data displays (map or histogram or both)
8. Using the summary box:
   • LPD- the total of all light point defects and their total surface area
   • Bins (1-8)- Bin splits intervals and the count of LPDs for each bin
   • Mean-the mean of collected LPDS
   • Std Dev-the standard deviation of collected LPDs
   • Area Count –The count of all areas( areas and scratches) on the substrate and the their total surface area
   • Scratch Count-The total number of scratches and their total surface area
   • Sum of all defects-The sum of all LPDs and areas, including scratches
   • Haze Region-The percentage of the measurable surface area containing haze
   • Haze average
   • Haze peak
9. To add the comment in the summary screen, press the minus key on the keypad or the minus button (Top left corner)
10. A LPD histogram plots the LPD count versus LPD diameter or cross-sections specified in the recipe. A haze histogram plots the number of defects versus haze values. Defect histograms display a red total area bar at the right.
11. Using the histogram
    • Zooming the histogram-allowing you to narrow the data range
    • Can be done using keypad or using the mouse (double click-left button and two markers will appear)
12. Using the wafer map-locating defects and dimensions f the LPD
    • You can magnify (zoom) the wafer map, apply user defined coordinates to the map(X-Y coordinate option required), and MicroView an area of the wafer.
    • To magnify( zoom) a map- double click the left button in the map
13. Examining a microview
    • Allows to examine a three dimensional representation of the surface of the substrate
    • To display a MicroView- press microscope, scan the substrate, double click the left mouse in the map, press zoom. The instrument displays the panning window and magnifies the map. Move the panning cursor to the area of interest, then press microscope.
    • To view the Micro View in full-screen, press ZOOM
14. Recipes:
    • A recipe name can be up to 19 characters long, and can contain any combination of alphabetic, numeric, or special characters.
    • Load- open and load a selected recipe
    • View/Modify – to view or change the recipe
    • New- create a new recipe
    • Save- save the recipe using the current recipe name
    • Save as- save the current recipe using a new name
    • Delete- delete the recipe
    • Recipe can be created, modified or viewed by opening the Recipe dialog box from the Scan or Setup applications
15. Recipe parameters:
    • substrate diameter
    • Edge exclusion-excluded from scan results, min=1mm. max=1/2 of wafer diameter
    • Gain/Max size- gain determines the range of data collected during a scan
    • For Surfscan 6200 gain is value from 1-8.
      • For value=1, size=63um or 250um2 ( GAIN 1).
      • For value=8, size=0.12um or 0.005um2 (GAIN8).
    • When you change Gain, the instrument automatically sets Area Form to Max Size.
    • Threshold specifies the smallest LPD size to be included in the scan results
    • Throughput is the speed at which the wafer is processed through the instrument: High, medium, normal, low.
    • Area From - this value determines the LPD size above which the instrument classifies LPD as areas
    • LPD count- the max number of light particle defects allowed( 0-99999)
    • LPD/cm2- Number of LPDs allowed per square centimeter
    • Area count-total number of areas allowed ( areas+ scratches)
    • Area mm2- total of all areas allowed in mm2
    • Scratch count-number of scratches allowed in mm
    • Selecting substrate parameters:
      • Edge exclusion=4mm (choose the select button at the bottom left of the recipe dialog box-to select a new substrate and thickness)
      • T (Tencor Instruments supplied calibration curve is used)
      • C (Customer supplied calibration curve is used)
16. The instrument collects defects and haze data from a wafer by illuminating the wafer surface with a laser beam, collecting the scattered light through an optics system, and amplifying the scattered light with a photomultiplier tube(PMT). The gain of the PMT determines the dynamic range for collecting data.
17. Selecting an LPD range
    • To specify the LPD range, use Gain, Threshold, and Area From parameters.
    • The gain setting determines the maximum LPD size of interest.
    • The threshold determines the smallest LPD collected during a scan. Using a combination of gain and the threshold settings, you can scan for a broad or narrow band of LPDs.