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Video Training Script for the Wyko Profilometer
Part 1: Overview of Wyko Profilometer
The Wyko Profilometer is an optical profiler. It uses non-contact interferometry for surface topography measurements. The Profilometer offers 2 different modes for measurement. The first mode is VSI and can measure a 2 mm step with a 3 nm resolution. The second mode is PSI, which can measure a 160 nm step with a 3-Angstrom resolution.
Let's get familiar with the various parts of the machine. There are four main parts to the Profilometer.
- The objective lens.
- The stage
- The keyboard
- The computer and TV monitors
Let’s also introduce our lab users.
Part 2: Loading a Sample
Before we can do anything, we must first start the software. As you might notice, the illumination is turned on as soon as the software is started. This can be seen by the reflection on a white piece of paper. Once the software has started we can now operate the Profilometer with the keyboard.
WARNING: You do not ever need to touch the Profilometer. Everything can be operated from the keyboard.
We can raise or lower the objective lens by rotating the focus knob. Rotating right moves the objective lens up and rotating left moves the objective lens down. Pressing the fast button can change the speed.
WARNING: Do not crash the objective lens into the sample.
We can tilt the objectives by pressing the tilt button and moving the joystick. This is how we can rotate the fringes or adjust the fringe spacing.
We move the stage by moving the joystick. Pressing up on the joystick moves the stage out and vice versa. Pushing right on the joystick moves the stage left and vice versa. You can think of the joystick as actually moving the objective. The button on the top of the joystick moves the stage fast for coarse adjustment. Tilting the joystick without pressing the button gives fine adjustment.
We load a sample by pressing up on the joystick in order to bring the stage out. We place the sample on the stage then move the stage in by pressing down on the joystick. We want to position the sample directly under the objective. We then lower the objective by rotating the focus knob to the left and pressing the fast button. You want to lower the objective lens until it is about half a centimeter away from the sample.
To remove a sample, rotate the focus knob to the right, move the stage outward by pressing up on the joystick, and remove the sample.
Before we perform a measurement on our sample, we need to calibrate both the VSI and PSI samples. This should be done at least once a day in order to ensure accurate data.
Part 3: VSI Calibration
The VSI calibration sample is stored in a plastic box. We store the VSI calibration sample face down to prevent contamination from landing on the surface. The sample is placed on some buttons to prevent it from coming in contact with the box. Mount the calibration sample on the stage with the label facing you.
We begin the calibration by clicking on the calipers. We select auto calibrate. We select all modes. Leave these boxes unchecked. The step height value is printed on the calibration standard and is 10 microns. To focus on the standard and observe the fringes, we open the intensity window.
Go to hardware. Make sure the 5x objective lens is selected and the 1x FOV. Also check to see that the filter is set to VSI. This slider controls the illumination. It can also be controlled by the page up and page down keys on the keyboard. Pressing page down will increase the illumination. Pressing page down will decrease the illumination. We increase the illumination until we see red in the screen. Then we will decrease illumination until we eliminate the red. Now focus on the calibration sample by pressing the fast button and rotating the focus knob to the right slowly.
The first image you see will probably be a false image from the bottom of the calibration sample. Continue raising the objective until you see the true surface. Now you can use the joystick to scan across the sample to find the step. This is the step. It is a rectangle that is etched into the calibration sample and it is 10 microns deep. Center one side of the step in the window. Move the focus until you can see the fringes.
If you are pressing the fast button, the focus is very sensitive. You must move the knob very slowly. We can rotate the fringes by pressing the tilt/tip button and moving the joystick. We tilt the fringes until they are perpendicular to the step and until we have 2 to 4 fringes in the field of view. Decrease the illumination to eliminate the red color. We can to adjust the focus until we have the best contrast. We also want to focus on both the top and bottom of the step to make sure we can determine which is higher. Move the focus to the left and we should see the fringes appear on the lower step. This is the lower step. Move the focus to the right and the fringes will appear on the upper step. We always begin a scan with the fringes on the upper step on any substrate.
Before clicking finish, let's recap the steps we have completed:
1) Place a step height standard in the field of view
2) Orient 2-4 fringes perpendicular to step direction
3) Adjust fringes for best focus at top of step
4) Select the step height value
Step 5 is to click finish. So let's go ahead and to that. Once we do, the Profilometer will perform the calibration in the VSI mode. You need now worry about the results of the calibration. Once it’s finished calibrating, replace the VSI sample in it’s box.
WARNING: Be sure to place the sample face down on the buttons
Part 4: PSI Calibration
This is the PSI calibration sample. We keep the sample covered to prevent damage. To remove the cover, twist the screws. A point will come when the screw will lift up. The lid will capture it. This prevents the screws from being lost. Be sure to place the lid face up. This will prevent any contamination from coming in contact with the lid.
WARNING: The PSI calibration sample is an optical flat. It is extremely important to be careful with the flat and prevent the sample from getting scratched.
We return to the intensity window. Go to the hardware window. Choose filter. We must select PSI Low Mag.
We now calibrate the sample the same way in which we did the VSI sample. Refer to the VSI Calibration section of this video for reference. The only difference is that the fringes are at 45-degree angle.
Let’s recap the steps to complete a PSI Calibration:
1) Place a reference surface the field of view.
2) Adjust 2-3 fringes at a 45-degree angle for best focus.
Step 3 is to click finish, so let’s go ahead and do that. The profilometer will display the results of the calibration. You need not worry about them.
Remove the PSI sample and place the lid back on.
Part 5: Measuring a Sample
You can check the hardware to check magnification, filter, and FOV. We open the measurement options window. We have to make sure we have the same magnification and FOV in the measurement options window. We are doing a VSI measurement, so we have to select the VSI radio button. You can choose the resolution you want to do.
There are options for both VSI and PSI modes. The settings for each section only matter if we are doing that kind of measurement. In our case, we are looking to do a VSI scan.
Let’s take a look at the VSI options. If you click on the VSI options tab, there are many choices. The 1x speed gives you higher resolution but takes longer. 5 microns is the minimum back scan at the 1x speed. You must guess the correct length of scan, but it must be at least as large as your features. You can also select the modulation threshold. This controls how sensitive the machine is to detecting fringes.
Let’s take a look now at the PSI settings. Remember, the PSI settings only matter if we are doing a PSI scan and the VSI settings will only take affect if we are doing a VSI scan. Averaging number when it's turned on will take the average of this number scans. The modulation threshold is as the same as in VSI mode. The vibration detection threshold automatically compensates for vibration. Leave the intensity selections blank, phase unwrapping at standard, reference blank, measurement filter at default and the phase algorithm at standard.
The other tabs are for advanced operation. You should not use them until you are familiar with the basic operation machine. In the measurement options you can also select intensity and calibration from the bottom of the menu.
Part 6: Analysis tools
You can either click the new icon or ctrl+n to begin a scan. The machine will then show you the results of the scan and you can select different analysis options from the toolbar. One of the most useful options is the 2-D analysis. This is similar to a Stylus Profilometer. This will show you the profile of your sample along a cross section that you choose.
You can measure a step height by clicking on the triangle and moving the cursor to the feature of interest. You can move the coordinate windows. The vertical distance will be displayed on the right and the horizontal distance on the top. You can also zoom in. Position the cursors on either side of the area you want to zoom in on Right click between the cursors and click on zoom in.
All the windows you open are saved. You can select any window by going to the window menu and clicking on any window.
The 3-d icon gives you a 3-d image of your scanned area. By left clicking in the window and moving the track ball, you can rotate the 3-d image. If you right click on any window, it gives you a menu. You can choose analysis options, which changes the way the machine interprets the data. Plot options, allows changing the way in which the machine displays the image. In plot options you can zoom the image, change the scale, and change the appearance. In analysis options you can choose a variety of analysis operations. One useful operation is data restore, which interprets missing data.
To save your data, go to the file menu, go to save data set as, and save your data set on the server Grover. When you save your data you are saving all the raw data, not the window that is open at the time.
Part 7: Finishing Tasks
When you are ready to stop using the system remove your sample from the stage.
WARNING: Be sure to move the stage back in. This helps prevents injury from occurring in the lab.
Open the intensity window and set the intensity to zero. If you do not do this, the light will remain on. Now you can exit out of the program by going to file, exit, and clicking yes.
Part 8: Closing Remarks
After watching this training video you should have a good understanding of how to:
1) Calibrate a VSI Sample
2) Calibrate a PSI Sample
3) Measure your own sample
4) Use the analysis tools
If you have any questions, please direct them to the trainer for this equipment. Do not direct your comments to Charlie.