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

Log in (access code is boss)
Load wafers(face up) to the carrier that says " SURFSCAN" .
Place the carrier with wafers to the right indexer.
In the menu option select "CAS" (this will read all wafers that are in the carrier).
Go to "Recipes" and load one of standard recipes.
Select one of the recipes:
- UCSB Gain4 (measuring small particles 0.16-1.6um)
- UCSB Gain2 (measuring larger particles 1.6-28um)
View the recipe and modify it if needed, default the bin.
Select the wafer you want to scan.
Select START.
Wait until scan is finished.
Record: LPD (sum of all particles #1- #8), particles #1(0.160-0.213)um, particles #8(1.20-1.60)um, haze region(%).
Take a picture of the scan (by phone).
Select "Home" so indexer moves up to loading/unloading position.
Unload wafers (ready for process calibration).
Log out.

Scan after process calibration

Log in (access code is boss)
Load wafers(face up) to the carrier that says " SURFSCAN" .
Place the carrier with wafers to the right indexer.
In the menu option select "CAS" (this will read all wafers that are in the carrier).
Go to "Recipes" and load one of standard recipes.
Select one of the recipes :
- UCSB Gain4 (measuring small particles 0.16-1.6um)
- UCSB Gain2 (measuring larger particles 1.6-28um)
View the recipe and modify it if needed, default the bin.
Select the wafer you want to scan.
Select START.
Wait until scan is finished
Record: LPD (sum of all particles #1- #8), particles #1(0.160-0.213)um, particles #8(1.20-1.60)um, haze region(%).
Take a picture of the scan (by phone)
Select "Home" so indexer moves up to loading/unloading position
Unload wafers.
Log out.

Surfscan photo

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

Introduction

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.

Basic skills

This chapter describes instrument controls, including keypad, mouse, floppy drive, and cassette indexer. This chapter also describes how to load a cassette and introduces you to basic program operation using the mouse or keypad.

Getting started

This chapter provides basic startup procedures for the instrument, including: (Powering up the instrument , Logging on to the instrument , Starting Scan , Quitting from an application, Logging off the system, Setting up the system for first use, Using the DOS shell (advanced use), Monitoring disk and database space)

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.

Scanning

Start the scan application

At the System Menu, choose the Scan icon. A blank Scan window appears. The Scan window is divided into areas that display results of scans.The Scan window displays the recipe name in the title bar and the scan sequence in the status box. Scan sequence indicates the order in which slots are scanned: from top-to-bottom or bottom-to-top.

Choose the recipe to be used

Load the cassette of substrates onto the right locator

Choose scan options

Enter a Lot ID, if desired

Scanning methods

This section describes scanning methods. The procedure describes how to scan all substrates, selected substrates, or one substrate from a cassette(called direct access). The table at the end of this section tells you where to go in this manual to use advanced scan features and options. The recipe sets the primary data of interest (defect or haze) and the initial data displays (map or histogram or both). For each scan, the instrument displays the primary data and lists the results of the scan in the summary. If the recipe specifies alternate data, the data can be manually chosen for display. The recipe also can specify automatic saving or printing of data. When the last substrate in the cassette is scanned or when you press HOME, the instrument homes the cassette and displays the Lot Summary window. (The Lot Summary screen does not appear if Suppress Lot Summary Display is enabled in the User Configuration dialog box.) The Cassette catalog lists the occupied slots of the cassette. The catalog can be numbered from bottom-to-top (the default) or top-to-bottom and the scanning sequence can be set to bottom-to-top or top-to-bottom.

Scanning options are: automatic or manual operation, scan sequence, and microscope hold for MicroViewing.

Using the scan window

When you scan a substrate, the instrument displays the results in the scan summary. Depending upon recipe settings, the instrument also displays scan results in a map, histogram, or both. Data are color-coded as shown by the bin splits in the summary. The cassette catalog displays the contents of the cassette and can be used to select individual substrates for scanning. The Scan window contains the following areas: summary box, wafer map, cassette catalog, histogram, and status box. In the Scan menu bar, choosing ID, Cass, Start, Auto, Home, or Save is the same as pressing the key of the same name on the instrument keypad. Recipe, XY, Print, and Display are pull-down menus.

The Recipe menu allows you to load a new recipe, view and modify the current recipe, create a new recipe, save a recipe, set user IDs, delete a recipe, enter the Lot ID, extend the puck for inspection and cleaning, and exit the Scan application. For details on recipes, see Chapter 5, “Recipes.” The Print menu allows you to print wafer summaries and lot summaries on the text printer. Summaries can be printed in 40, 80, or 132 column format. The Select Printers item allows you to select the text and graphics printers for the system. The Resume Printer item starts a suspended print job. See Section 4.11, “Printing Summaries,” for details on printing. The Display menu provides data display combinations: defect map only, defect histogram only, defect map plus histogram, haze map only, haze histogram only, or haze map plus histogram. The recipe specifies the initial data display. The Help menu provides help topics. Choose Using Scan to view the help topics related to the Scan application or choose Contents to open the help system. Choosing Using Help displays the Microsoft Windows Using Help topics.

Quick reference

This section summarizes the actions available when using the Scan application (change the scan order, change the data display, choose automatic scan, enter the Lot ID, enter the wafer (substrate) ID and etc.)

Using the summary box

The summary displays the date and time of the scan, the results of the scan, bin splits, overlay controls, and a selection of recipe parameters. The bin splits are color-coded, as shown by the numbered buttons. You can enable or disable a bin from the map or histogram by selecting a bin split button. The summary updates when you enable or disable a bin split, edit a defect or haze bin, or magnify the map. Buttons 1 through 8 control the bin splits for the primary data. Button 0 overlays the alternate data. Button 9 overlays area data. For example, all haze data can be overlayed onto a defect map by selecting button 0. The summary lists primary data and alternate data (if one is selected in the recipe).

The recipe sets: Primary data of interest (defect or haze); Initial data displays (map or histogram or both).

Data from 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.

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)

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

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
- 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
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)
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.