Condensed AFM operating instructions:

Transcription

1 Condensed AFM operating instructions: 1. Log onto system at access controller 2. Take the parts you need to mount a probe out of the drawers. You need the appropriate probe holder, tweezers (these are in the top drawer), the black cylindrical mounting base (this is in the bottom drawer), and some AFM probes (you should have your own probes). (use these tweezers) 3. There should NOT be a probe in the probe holder. If there is you can keep it or put it in the used probe box. 4. Blow off the probe holder with nitrogen! 5. Take everything to a stereo-zoom microscope. When you want to look at the probe holder you should put JUST the probe holder under the microscope! Inspect the probe holder for contamination or damage, especially the groove the probe fits into. Inspect the probe you want to use. Select the cantilevers you want to use if necessary. 6. Put the probe holder onto the pins on the mounting base that have the raised pad. The pins are asymmetrical! The probe holder can only go on one way! Be careful! Press down on the springloaded tab on the probe holder and pull it back. 7. Put the probe in the probe holder. Put the spring-loaded tab onto the probe. If the probe is not all the way back in the groove in the probe holder it is better to use the spring-loaded tab to wiggle the probe to the correct position. It is very easy to flip the probe out of the probe holder if you try to push on the probe with the tweezers. 8. Take everything to the AFM. 9. Open the hood. Make sure the scanner cable is unplugged. On the right side of the scanner slot there is a knurled lock-screw, turn it clockwise until it is all the way in, then GENTLY lift the scanner and remove it from the AFM. 10. Gently place the probe holder onto the scanner, taking care not to use force and that the pins are correctly oriented. Make sure the probe holder is not tilted, but do not force it. 11. GENTLY slide the scanner back into place on the AFM; once it has slid all the way down, turn the knurled lock-screw counter-clockwise until it JUST gets loose. This will lock the scanner in place. Plug in the cable. The laser will not turn on until the controller boxes are on and the software is started. 12. Turn on the controller boxes sitting under the monitors. The switches are located in the right rear of each box. You MUST do this BEFORE you start the software! Author: Joel Pikarsky Microelectronics Research Center Page 1 of 13

2 13. Double left mouse click on the NanoScope AFM software icon on the desktop of the monitor on the left. After the software has started, a small microscope icon will appear in the upper left hand corner of the software window. Left mouse click on that icon to begin real-time startup. 14. Take a small piece of white paper and place it under the laser. This is optional but it makes the laser easier to see. You can also set the Illumination value to 0 in the Other Controls window. 15. LOOK AT DIAGRAM NEAR END OF INSTRUCTIONS! Use the two knobs on the top of the scanner to adjust the position of the laser spot. If the laser spot is visibly shining on the paper, use the x-axis positioning knob to move it to the right until it is gone. The laser spot should now be on the probe body. Move the laser spot slowly left until the laser spot just becomes visible. Now use the y-axis positioning knob to move the laser spot up and down until you see the shadow of the cantilever. 16. You will see different shadows depending on what kind of probe you are using and how many cantilevers it has. Tapping mode probes have only one cantilever. Some are rectangular and some are pointed at the tip. Contact mode probes usually have multiple cantilevers. Some are rectangular and some are triangular. Each cantilever is a different length. 17. In general, to align the laser spot on the cantilever, you want to move the laser spot to the very tip of the cantilever. Then move the laser in the Y-axis to center the laser spot on the cantilever. Then move the LS in the X-axis, to the right, to obtain the correct sum value. It is easiest to use the sum value to indicate the location of the laser spot when the laser spot is very near the tip. The final sum value should be slightly greater than 2. Remove the paper when you are finished! 18. LOOK AT DIAGRAM NEAR END OF INSTRUCTIONS! Now use the two knobs on the side of the scanner to make the reflected laser hit the center of the photodetector. Start with any knob, turn and watch the position of the red spot and the sum signal. If the red spot goes to the center of one side, stop and turn the other knob. If the red spot does not move, watch the sum signal. If the sum signal gets smaller, you must turn the knob the other way. For TappingMode, put the spot in the center. For contact mode, put the spot at 2-volts below the center (vertical deflection = -2 volts). Author: Joel Pikarsky Microelectronics Research Center Page 2 of 13

3 19. The stage should be all the way to the front, if it is not, left click on the Stage menu on the toolbar and left click on Load new sample option. The stage will come all the way to the front. Put the sample on the chuck. Only the hole in the center of the chuck uses vacuum, turn the vacuum on (the vacuum switch is to the upper right of the scanner). 20. If your sample is tall, check the distance between your sample and the probe. If you sit in front of the AFM and look straight at the probe you should be able to see the distance between your sample and the probe. If the probe is very close to your sample, raise the scanner by left clicking on the Withdraw icon a few times. You do not want the probe to hit your sample when you move it under the probe. 21. Before you can do Locate Tip you must move the stage so that something reflective (usually the chuck) is under the probe. 22. Left click on the Focus Surface icon. Left click on Zoom Out. Press and HOLD the Lock button on the trackball, spin the trackball in the direction you want the stage to move. The stage will continue to move as long as the Lock button is pressed. Left click on Ok when you are done. WATCH YOUR SAMPLE AS IT MOVES TOWARDS THE PROBE!!! DO NOT HIT THE SCANNER WITH YOUR SAMPLE!!! You can also move your sample under the probe by Left clicking on the Stage menu on the toolbar and left click on Move To (x,y). Set Y position change to 30,000 um or 40,000 um. Left click on Move. Left click on Quit. 23. You must do Locate Tip BEFORE you do Focus Surface! Left click on the Locate Tip icon. The system will initialize. Left click on Zoom Out. If the tip is not visible, use the two knobs on the microscope/camera unit, which is to the lower left of the scanner to find it. Press and HOLD the focus button on the trackball. Smoothly roll the trackball toward or away from you to focus on the tip. When the tip is in focus, increase the illumination to 100. Press and HOLD the Zoom button on the trackball and SLOWLY move the trackball to zoom in on the tip. Stop when the image gets dark. Focus again. 24. Adjust the cross until it is in the center of the cantilever near the tip. Left click on Ok. 25. Left click on the Focus Surface icon. Left click on Zoom Out. Move your the stage by moving the trackball. Move the stage so your sample is under the probe. 26. The probe should be several millimeters above your sample. When you are correctly focused on the surface the probe will be about 1 or 2 millimeters above your sample. Press and HOLD the focus button on the trackball. Smoothly roll the trackball TOWARD you. This moves the probe Author: Joel Pikarsky Microelectronics Research Center Page 3 of 13

4 (and scanner) DOWN (closer to your sample)! WATCH THE DISTANCE BETWEEN THE PROBE AND YOUR SAMPLE, NOT THE MONITOR! When the distance is about 1 or 2 millimeters start to look at the image on the monitor. The image will not be in focus. To make the focus better, FIRST move the probe UP! This may not help but you won t crash your probe into your sample! If this does not help, THEN move the probe down. If you move the probe too far down you will crash the tip into your sample. When this happens the sum signal will go to zero, you will see an error message on the screen, and the trackball will stop working. Congratulations, you have just destroyed your probe. Continue focusing until the image is sharp. 27. Use the trackball to move the stage until the part of your sample you want to see is under the cross. If you are doing TappingMode this is when you do AutoTune. 28. Put in the correct scan parameters in the NanoScope Control window. 29. Double check the position of the laser spot on the photodetector, the position of your sample, and the scan settings and close the hood. 30. Left click on the Green Engage icon. 31. When the probe engages the surface, the screen on the right changes and shows the image scan. Change the Setpoint to press a little harder on the surface. Watch the Z Center Position bar on the right monitor. If the Z Center Position Voltage changes by more than a few volts, you have a false Engage. Left click on the Withdraw icon. Left click on the Green Engage icon and try again. 32. Set the scan size to desired area and tune the system. 33. Click on the sine waves icon (Scope mode or Wave mode). 34. Left click on the Integral Gain value to highlight it. ALWAYS tune the Integral Gain first! 35. You can use the left (decrease) and right (increase) arrow keys to change the Integral Gain value or you can type in the value. Increase the value until feedback is seen (fuzzy lines). Decrease the Integral Gain value until the feedback goes away and then decrease 3 more left arrow key clicks. 36. Repeat the previous step for Proportional Gain. If you increase the Proportional Gain value to about 5 times the Integral Gain value and there is not any feedback, stop. Author: Joel Pikarsky Microelectronics Research Center Page 4 of 13

5 37. If the Trace and Retrace lines do not appear to track the surface adjust the tip velocity and the Amplitude Setpoint. The maximum tip velocity for best resolution is 10 um/s. Slower is better. If the Trace and Retrace lines are not symmetrical, adjust the setpoint to press harder on the surface. Be careful! It is better to press too soft than too hard! (In TappingMode do not decrease the Amplitude Setpoint below 50% of the Target Amplitude!) Re-tune the Integral Gain and Proportional Gain! If you change the scan size or go to another place on your sample you should tune everything again! 38. When you are ready to capture an image, left click on the Capture menu. Left click on Capture Filename. Type in the filename you want. The filename can only have 8 characters, (letters, numbers, and the underscore). If you want to start a capture left click on Capture. If you left click on Ok the AFM will save your filename and use it the next time you start to capture an image. 39. If you want to go to a different place on your sample, left click on the Withdraw icon, left click on the Focus Surface icon, and move the trackball so the cross is on the place you want to see. If your sample is the same everywhere you do not have to put the scan parameters back to the initial values. You should make the scan size about 1 um. 40. When you are done, left click on the withdraw icon. Left click on the Stage menu on the toolbar and left click on Load new sample option. The stage will come all the way out. 41. Turn off the vacuum and unload your sample. 42. Unplug the cable to the scanner. Turn the knurled clamp-screw clockwise until it just gets tight. Lift out the scanner, pull off the probe holder and put the probe holder down and put the scanner back on the microscope. DO NOT clamp the scanner in place since the next user has to remove it. 43. Close the AFM hood. 44. Put the probe holder onto the pins on the mounting base that have the raised pad. The pins are asymmetrical! The probe holder can only go on one way! Be careful! 45. Remove the probe and put it back into your box of probes. 46. Put the probe holder back in the box. Put the box and the tweezers in the upper drawer. 47. Put the black cylindrical mounting base in the bottom drawer. Author: Joel Pikarsky Microelectronics Research Center Page 5 of 13

6 >>> The sections below describe operations in the OFFLINE mode. <<< VIEWING SCANS When you capture a scan the DI software automatically saves the data in the!:/ directory. Sometimes the! symbol is called a bang. During training the!:/ directory will be called the bang directory AFM scan data is saved as a 2-D array of values that represent the topography of the surface of your sample. The column number represents the X co-ordinate, the row number represents the Y co-ordinate, and the value of each array element represents the Z co-ordinate. There is also a plain-text section at the beginning that lists the scan parameters. To view the scan data as an image you must go to the offline mode in the NanoScope software. Left click on the offline icon, the!:/ directory and a top-view image of the first data file will appear. The NanoScope control window will show a list of data files. You can look at other drives by left clicking on the drive icons at the top of the Files window. There are many ways to look at an AFM scan. The most common are Section, which displays a cross-section, and Surface Plot, which displays an interactive 3-D image. SAVING IMAGES If you want to save an image of a scan that was generated in offline mode, left click on Utility, left click on the TIFF Export option, a window will open. For Background, select Reverse, (this will make the background white in the saved image). Type in the directory where you want the image to be saved. Type in the filename. The filename must be DOS compatible (see below). Left click on Ok. One method is to first save your images to the E:/ directory, rename them, and then use Windows Explorer to move them to your user directory. Author: Joel Pikarsky Microelectronics Research Center Page 6 of 13

7 TRANSFERRING FILES On the AFM computer in the cleanroom you should create your own directory. 1. Open Windows Explorer and left click on the + next to the E:/ drive 2. Left click on the Users directory. You will see directories for other users 3. Make a New Folder. The name should be the capital letter of your first initial, an underscore (_), your last name with the first letter capitalized, and no spaces, i.e. G_Burdell. 4. Keep all your files here. If there are files in other places they will be erased. DO NOT leave your files in the!:/ directory, they will be erased! 5. You can create as many subdirectories as you want in your user directory and you can name them anything you want. The NanoScope software can only handle DOS compatible filenames. A DOS compatible filename can only have 8 characters. The characters can be letters, numbers, and the underscore. No spaces or other punctuation marks are allowed. The filenames are NOT case sensitive (capital letters are the same as small letters)! If you use the NanoScope to look at a directory (folder) or filename that is not DOS compatible the software will truncate the name, e.g., if the name of a directory is MICROELECTRONICS, the software will display microeµ1 as the name. The software ignores capital letters and shortens the name to six characters followed by a µ (mu) followed by a number. To type the µ character in the Nanoscope software, use shift + ~ (tilde). IMPORTANT!: If you use the NanoScope software to look in your user directory you must double left click to see any subdirectories! Don t leave your files in the!:/ directory, they will be erased. You should move your files out of the!:/ directory. One way is to select all the files you want to move, left click on the Files Menu and then left click on the Move option. A window will open where you can specify the destination directory for the files. It is easiest to move all your files to the E:/ directory and then use Windows Explorer to rename your files and move them to your user directory. DON T leave your files in the root of E:/, they will be erased. After you move your files out of the!:/ directory into a standard Windows directory, file and directory names can be up to 255 characters long, including extensions, names can contain any character, including spaces, except the following:? " / \ < > * : DO NOT USE SPACES IN YOUR FILENAMES!!! You will not be able to download your files from Grover (the cleanroom server) if the filename has a space! You can use the underscore ( _ ) instead e.g. no_spaces_allowed. It is a VERY good idea to rename your files. You should use a name that is a good description of what you are scanning. I promise that if you capture a scan with the name gb_sys03.004, three weeks later you will have no idea what it is. An example of a good name would be: CMOS_test_structure_01_gate_oxide_layer_planefit.003. You do not need to include a lot of information on scan parameters. If you open the raw data file with a text editor (like notepad) there is a section at the beginning that lists ALL the scan parameters. Author: Joel Pikarsky Microelectronics Research Center Page 7 of 13

8 You should also copy your files to Grover. Grover is the F:/ drive. You are not allowed to create directories (folders) on Grover. This makes it difficult to organize your files. One method is to compress all the files you want to copy to Grover and then just move the compressed file to F:/. The AFM computer in the cleanroom and the AFM computer in room 133 have a compression program called WinRAR. To compress your files right click in Windows Explorer, move the pointer to New, and then left click on WinRAR archive. A new file will appear. Type in the name you want to use. Make sure to keep the.rar extension. Any file you drag into this file will automatically be added to the archive. The original file will not be changed. Author: Joel Pikarsky Microelectronics Research Center Page 8 of 13

9 Aligning the Laser 1 2 When you begin the laser spot will be at some random location. Move the laser spot to the right until it disappears. 3 4 Move the laser spot to the left until it is just visible. Move the laser spot up and down to find the cantilever. Author: Joel Pikarsky Microelectronics Research Center Page 9 of 13

10 5 6 Move the laser spot to the very end of the cantilever. Move the laser spot up and down to maximize the sum signal. This will center the laser spot. 7 8 Move the laser spot to the right to get the correct sum signal. The sum signal will be different for different probes. Don t move the laser spot too far to the right. Author: Joel Pikarsky Microelectronics Research Center Page 10 of 13

11 Aligning the laser on the photodetector Author: Joel Pikarsky Microelectronics Research Center Page 11 of 13

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