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Zygo White-Light 3D Surface Profiler, zygo

The Zygo White-Light 3D Surface Profiler provides fast, non-destructive, quantitative surface characterization of step heights, texture, roughness, and other surface topography parameters. The measurement technique is non-contact, three-dimensional, scanning white light and optical phase-shifting interferometry.

Picture and Location

 ZygoZygo

This tool is located at B5 on the Lab Map.

Background

The Zygo is based on scanning white-light interferometry, a traditional technique in which a pattern of bright and dark lines (fringes) result from an optical path difference between a reference and a sample beam. Incoming light is split inside an interferometer, one beam going to an internal reference surface and the other to your sample. After reflection, the beams recombine inside the interferometer, undergoing constructive and destructive interference and producing the light and dark fringe pattern.

Sample Zygo Images:

 Sample Zygo Image  Sample Zygo Image  Sample Zygo Image  Sample Zygo Image

For additional information about other Zygo products, you can visit www.zygo.com.

 

Process Capabilities

Cleanliness Standard

 The Zygo Profilometer appears in all three equipment groups (clean, semiclean, and gold).

Performance of the Tool

What the Tool CAN do

  •     * Available objectives are: 2.5X, 10X, 20X, and 50X with additional zoom from 0.5 to 2X
        * Field of view ranges from 0.14 x 0.11mm (50X) to 2.82 x 2.11mm (2.5X)
        * Vertical resolution is 0.1 nm
        * Minimum lateral resolution is 0.11 µm (50X objective, 2X zoom)

 

How to Become a User

  1.   Read all material on the SNF website concerning the Zygo.
  2. Contact SNF training contact on the Equipment Summary page.

 

Operating Procedures

 

Introduction:

  • Measurement technique: Non-contact, three-dimensional, scanning white light (600 +/- 20 nm) and optical phase-shifting interferometry
  • Vertical resolution is 0.1 nm
  • Minimum lateral resolution is 0.11 µm (50X objective, 2X zoom)
  • Objectives: 2.5X, 10X, 20X, and 50X
  • Field of View:
    2.5X: 2.82 x 2.11 mm,
    10X: 0.7 x 0.53 mm,
    20X: 0.35 x 0.26 mm,
    50X: 0.14 x 0.11 mm
  • Image zoom: 0.5, 0.75, 1.0, 1.5, 2.0
  • measurement length 5 µm to 100 µm, extended to 5300 µm
  • it is easiest to find "fringes" when there is a flat surface on your sample
  • if surface is transparent to this wavelength, consider coating the wafer with a thin film of reflecting material (>30 nm aluminum)

Instructions:

DON'T:

  1. Drop, scratch, or dirty the lens parts of the objectives. The objectives are very expensive. Be very careful.
  2. Drive objective into sample
  3. Re-calibrate ANYTHING.
  4. Ever press the CALIBRATE or RESET button in the upper left corner of the micro.app screen.
  5. Turn any positioning knob except the one labeled "TENSION."
  6. Set the Z-stop! Red light should be flashing.

Directions for using the Zygo:

  1. Enable the zygo.
  2. Turn on both monitors.
  3. Press "ctrl-alt-delete" to log into Windows.
    Username: zygo
  4. After windows loads, double click on the shortcut to Metropro 7.11.1 on the desktop.
  5. After the program loads, click on Micro.app.
  6. Install the zygo objective you wish to use. These objectives have been calibrated for this specific machine. BE VERY CAREFUL WITH THE OBJECTIVES!! You must first attach the small metal ring to the objective you wish to use, then install the objective/ring into the Zygo. There is an extra manual for the 2.5X objective.
    Either the 10X or the 20X objective should be left for the next person.
  7. In the upper left hand corner of the application screen, there is a box that says either 2.5X, 10X, 20X or 50X. Using left mouse click, toggle through the box until the number corresponds to the objective you are using.
  8. Rotate the zoom dial on the front of the Zygo to 0.5. This is the zoom dial. It is generally easiest to focus on your sample with 0.5 zoom.
  9. Place sample on stage, don't scratch the stage and don't damage the objective!!!
  10. There is ONLY ONE knob you should ever turn by hand on the Zygo. This knob says "TENSION" and is located on the microscope itself. Turn this knob for large scale focusing. DO NOT EVER turn the 3 smaller back wheels by hand as these are tied to drive motors and can be broken if turned by hand.
    Turn the large knob which says "TENSION" on it, until the image gets very bright. This means you are close to proper focusing. When the image is bright, press F5 (adjust viewing light level). This will reduce the light seen on the monitor allowing you to see your features. You can usually focus on your sample with only this large wheel.
     
    Use the left joystick (z axis adjustment) for fine tuning the focusing. I recommend reducing the z-axis speed to 2 of 4 bars to actually give yourself a chance to see your features in focus. If you try to use 3 or 4 bars you will probably just overshoot your focus plane. After you have your sample in focus, you may wish to press F5 again to adjust the viewing light level.
  11. Flatten the sample.
    To improve lateral resolution, it is generally a good idea to find a place on your sample that is flat and maximize the width of the interference fringes. To do this, use the x-y joystick (the right one) to find a relatively large, flat space on your sample. Use the left joystick (z-axis) to bring the fringes into the center of this area. Press the "axis select" button above the right joystick so that the controller reads "R-P". You are now in pitch and roll mode (not x-y mode). Adjust the sample until the interference fringe spacing is maximized. I generally find that adjusting the fringes until they are either vertical or horizontal, then using the other rotational axis to widen the fringes until you see basically one shade of gray on the screen works best.
  12. Adjust the zoom.
    On the front of the Zygo microscope is a dial with settings 0.5, 0.75, 1, 1.5, and 2. This is the zoom dial. Adjust the zoom to your liking. Play with the focus/light level again if needed.
  13. Field Stop
    You may notice a bright spot in the center of your image. You will need to turn down the light using the Field Stop located on the right side of the microscope. Pull or push the field stop knob until the image is acceptable. The Field Stop removes the non-axial rays which cause the bright spot to appear.
  14. Measurement Control Box
    Single click on the "Measurement Ctrl" button located on the left side of the application screen.
    Select the appropriate Image Zoom. Be sure to also set the magnification to the same setting as the zoom dial on the front of the Zygo. If the magnification dial and the magnification setting in the software do not match, THE X,Y DATA WILL BE WRONG. However, the z data will still be OK. Anytime you adjust the zoom dial, be sure to change this software setting.
    Select the appropriate Scan Length. The measurement length can either be 5 µm, 10 µm, 40 µm, 100 µm, or extended up to 5300 µm. Toggle through these options until you find one that best suits the topology of your sample. Understand that if you choose, for example, 10 µm, the scan will start 5 µm below the current plane of focus and end 10 µm above the current plane of focus.
    Close the Measurement Control Window.
  15. Measurement Light Level Adjustment
    Maybe the most critical issue is adjustment of the measurement light level by pressing F4. Whereas the viewing light level is adjusted automatically by pressing "F5," the measurement light level must be adjusted manually. Press "F4" and the lighting box appears on screen. The lighting level is adjusted by pressing the + and - keys, / and * for coarse. Red indicates that a CCD pixel has saturated. Press the "-" key or the "/" key to reduce the CCD integration time until all the red is removed from the screen, then press the "-" key once more for good measure. Run through the length of the scan with the z-axis joystick (left one) making sure that at no point in the scan does any CCD pixel saturate. Ideally, your scan will be (at least some of the time) in the green and never in the red. Do not turn the sensitivity of the CCD array down too far however, or you wont be able to image your sample either. If you do not adjust the light level correctly, your scan will be missing data where the sample either saturated the CCD or was not reflective enough for the CCD pixels to see.
    Click on Set or Enter.
  16. Masking (optional)
    Without masking, the zygo will define its own reference plane as level, making your data come out slightly tilted if it is not parallel with the zygo's plane. You may also wish to reduce the area over which the zygo takes data so that only your feature appears in the plots. To define a mask, press F3 or press the "Mask Data" button in the upper left hand corner of the screen. Select "Rectangle" and then draw a rectangle on the Mask Data screen that covers an area you know to be flat. Select "BG Inc" and notice that only the rectangle is colored orange. Select "Reference" and then "Define." You have just told the interferometer to call this/these areas flat. Select "Unfill" and be sure that the rectangle you just drew is still on the screen, but no longer filled. Select "Rectangle" again and draw a rectangle over the area you wish to measure. This area does not need to overlap with the reference area, but there is no harm in overlapping them. Select "Test" and then "Define." This is the area that will actually return data.
  17. Measurement
    Press "F1" or select "Measure" from the upper left hand corner of the screen to start the measurement. Results are calculated and displayed.

 

Saving Data

  1. To save an Image:
    Left click on the word "Zygo" in the window bar of the plot you wish to have a picture of.
    Choose "File", then ".tif" or ".bmp", then "Print" from the window that appears.
    Choose "Dirs" to change directories to your user directory (".." brings you up one directory).
    Press "Done" when in your user directory.
    Click on "current selection" and type a file name with extension (.bmp),
    press [Enter] when done.
    Click "Done."
  2. To save Desktop Data for later use by metro pro only:
    Click on "Save Data" in the upper left corner of the screen. Navigate the directory structure to your user folder, type in a name for the data, add file extension ".dat", press [Enter], and then click the Done button.
  3. To save numerical Data (for later use with Excel)
    Right click a surface profile. Choose "Window Control", then "Print", then choose "Data" and "File" and the way you wish the data to be formatted (Columns, Tabs, or Commas). Click "Print", navigate to your directory, and save. Extension of file is needed, like ".txt" for text file.

    Save your files temporarily in your own folder on the F drive in the "newusers" folder. 
    Burn your files on a CD, CD-R only (please bring your own CDs).
    How to use the CD burner:
    On the desktop, open the 'NTI CD Maker 6 Platinum' program.
    Select Data and then Data CD. Select your files from your folder, follow the Easy Step 1, drag and drop the selected items to the Data Track Layout field, and follow the Easy Step 2, insert your CD (CD-R only) into the lower disk drive, hit OK, select write and hit Start. Once the burning has been finished, the disk drive opens automatically, remove your CD, click on OK, close the disk drive and the program.

 

Helpfull Hints:

Several words (OK, maybe more than several):

  1. Zoom to increase lateral resolution
    The vertical resolution of the Zygo is 0.1 nm. Minimum lateral resolution is 0.11 µm (50X objective, 2X zoom). To get the best resolution, the maximum power objective is required and the maximum amount of zoom is required. There are only so many pixels in the CCD array, imaging them to a smaller area decreases the amount of sample they each look at, thereby increasing the resolution of each pixel.
  2. 50X objective
    The 50X objective has its own focus on the objective itself. This can make using the 50X a little annoying. The procedure that I have found works for me is to first focus on the sample you are trying to measure with the Zygo knob (TENSION) and joystick. After you have focused, unless you are lucky, you won't see any interference fringes. Carefully rotate the focus of 50X objective itself until the interference fringes appear. You want the fringes and the focus to be in the same plane.
  3. Leveling profiles:
    There are many MANY functions which analyze and alter your data. For example, lets say you want to level your sample (without using the masking feature discussed above).
    Right mouse click a surface profile and choose Show Controller. Toggle Inspect Off to Inspector 2.
    In surface profile: left mouse click, grab and move two inspectors to level surface.
    Click on Level.
    Results:
    yDist: step height
    xDist: distance between two inspectors
    Or go to the profile window and toggle the "remove" field until it says "line." Then press the "Analyze" button in the upper left hand corner of the screen. A line will be fit to the profile and then this line will be subtracted from the profile.
    This method may not work for your profile if, for example, you have a step profile. In this case, you may wish to define 2 specific points in your profile between which the line will be fit. To do this, click on "Ref Pt 1:" in the profile window, define the location of the 1st reference point, then do the same thing for "Ref Pt 2:". Be sure "Remove:" displays "line" and press the "Analyze" button.
  4. Data Analysis
    There are many other functions which analyze your data for you. To find some of these, right click on "Surface Profile", choose "New Result", and (for instance) choose "RadCrv". You should see a new field appear in the profile window which calculates the radius of curvature of the profile in the profile window.
  5. More things on the profile plots:
    If you wish to remove a profile from the profile window, hold down "Ctrl-d" and click on the profile line you wish to remove in the 2D surface map.
    You can also inspect profiles with cross hairs. Right click on the profile and choose "Show Controller." Click on "Inspectors" either once or twice if you want one or two cross hairs.

 

Shutdown Procedures:

  1. Quit the program with the window close button (upper right hand corner). Quit: YES
  2. Press "control-alt-delete" ONCE and choose "logoff" to log out of windows. OK
  3. Turn off both monitors.
  4. Leave the 10X or 20X objective in the Zygo for the next person.
  5. Rotate zoom dial back to 0.5.
  6. Disable the zygo.
  • Clean up around the area.
  • Report problems and notify the responsible people of any machine problems.

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