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

before process calibration

1. Log in (access code is boss)
2. Load desired number of Si wafers to the carrier that says " SURFSCAN" .
3. Place the carrier with wafers to the right indexer.
4. Select in the menu option "CAS" (this will read all wafers that are in the carrier)
5. Load one of standard recipes
6. Select one of the recipes:
   • UCSB Gain4 ( measuring small particles 0.16-2.8um)
   • UCSB Gain2 ( measuring larger particles 2.8-28um)
7. Select one of the recipe, modify it if needed, default the bin
8. Select the wafer you want to scan
9. Press SCAN
10. Wait until scan is finished
11. Record: LPD, particles #1, particles #8, haze
12. Take a picture of the scan (by phone)
13. Select "Home" so indexer moves up to loading/unloading positon
14. Wafers are ready for process calibration

after process calibration

1. Log in (access code is boss)
2. Load treated Si wafers to the carrier that says " SURFSCAN" .
3. Place the carrier with wafers to the right indexer.
4. Select in the menu option "CAS" (this will read all wafers that are in the carrier)
5. Load one of standard recipes
6. Select one of the recipes :
   • UCSB Gain4 ( measuring small particles 0.16-2.8um)
   • UCSB Gain2 ( measuring larger particles 2.8-28um)
7. Select one of the recipe, modify it if needed, default the bin
8. Select the wafer you want to scan
9. Press SCAN
10. Wait until scan is finished
11. Record: LPD, particles #1, particles #8, haze
12. Take a picture of the scan (by phone)
13. Select "Home" so indexer moves up to loading/unloading positon
14. Unload the wafers

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. • Log in, access code is BOSS. • Double click on the icon of the application to start application. • 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. • Before scanning: 1 Choose the recipe to be used 2 Load the cassette of substrates onto the right locator 3 Choose scan options 4 Enter a Lot ID, if desired Scanning methods: One substrate-direct access( cassette) or more( AUTO) Scanning options: 1. automatic or manual operation 2. scan sequence 3. microscope hold for MicroViewing The recipe sets: 1 Primary data of interest ( defect or haze) 2 Initial data displays (map or histogram or both) 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 To add the comment in the summary screen, press the minus key on the keypad or the minus button ( Top left corner) 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. 1.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) 2. 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 3. 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

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 Vieew/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

Recipe parameters: 1.data collection parameters substrate diameter~125mm Edge exclusion~ excluded form 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; Max: For value=8, size=0.12um or 0.005um2). 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- 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 LPDS as areas LPD count- the max number of light particle defects allowed( 0-99999) LPD/cm2- Number of LPDs allowed per square centimeter (wafer #3: 417/((4.6*4.6)*3.14)=417/66.44=6.27cm2 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 mmm Scratch mm-Selecting substrate parameters: • Edge exclusion=4mmm • 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) 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. 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.