Standard Operating Procedure for the Amray 1810 Scanning Electron Microscope Version: 29 NOVEMBER 2014

Transcription

1 Standard Operating Procedure for the Amray 1810 Scanning Electron Microscope Version: 29 NOVEMBER Utility Requirements a. System power is supplied by two 120 VAC/20 A circuits. When doing maintenance to electrical components, disconnect power by toggling the power switch on the back of each console. b. The SEM currently uses two compressed gasses to operate: Nitrogen and Compressed Air. Nitrogen, the vent gas, is house-supplied. This gas is externally regulated to 10 psig. Compressed Air, which is house-supplied, is used to operate system valves. The gas is externally regulated to 80 psig and internally regulated to 60 psig. c. Cooling water for the diffusion pump is provided by a recirculating chiller. The temperature should be kept at 19 C and the operational pressure should be 10 psig. 2. General Precautions a. High Voltage: The SEM employs voltages of up to 30 kv, which may be fatal to users. Do not attempt to defeat the protective interlock systems. b. Sample Loading: Use caution when loading samples in the chamber. If the sample is loaded too high, it may damage the final aperture. When the sample stage is pushed in, be careful that it does not contact the collector screen. Take care when opening and closing the door, as there are pinch points. c. Collector Screen: When positioning the sample for imaging, be sure that it does not come into contact with the collector screen, as this could push it into the final lens, which will cause an electrical short and impede imaging. Use the internal camera system if you think that this could be a problem. d. Contamination: All samples must be completely clean and dry prior to being placed in the chamber to prevent outgassing contamination. No photoresist is allowed in the SEM. Other organic materials need staff approval, require a lower kv setting and a gold coating. No adhesives are allowed in the chamber except for carbon pads, carbon and copper tape, and silver paint (paint must be completely dry.) Other adhesives will contaminate the column and damage the SEM. e. Chamber Vacuum: It is desirable to leave the system under vacuum (STAND BY LED lit) when not in use. This helps to prevent moisture accumulation and will help to desorb contaminants from the inside walls of the chamber. f. Imaging Control Panel: Unless otherwise instructed, the knobs and buttons on the imaging control panel should not be used to control the SEM. These controls are functional and will conflict with the computer software, making it unpredictable and/or inaccurate. Only adept users of the SEM may use these controls. 3. Putting a Sample in the Chamber for Imaging a. Verify that the instrument is ready for use: I. The compressed air supply is at 80 psig and nitrogen is at 10 psig II. The chiller is at 19 C III. The STAND BY, V5, and DIFF PUMP red LEDs and TC1, TC2 and TC3 green LEDs are illuminated on the vacuum control panel (VCP) on the front of the column console If one or more of these conditions are not met, notify cleanroom staff immediately. 1

2 b. To open the chamber for sample loading, press the VENT button on the VCP. After about 15 seconds, the V2 LED will illuminate and chamber venting will be audible. After about another 15 seconds, the TC2 LED will turn off and, soon after, the door will be ready to open. Use caution when opening and shutting the chamber door. There are pinch points between the door and its hinges. c. When the chamber door has been opened, press the STAND BY button on the VCP to close the nitrogen vent valve (V2). d. Place the prepared sample mount into the mount socket and lightly tighten the set screw using the provided driver. Make sure that the sample and/or mount are positioned such that, when the door is closed, they do not contact the collector screen and/or the final lens. e. Close the chamber door and press the EVACUATE button on the VCP to pump down the chamber. Press against the chamber door during the first few seconds of pump-down to ensure that the door seals. After about a minute or two, the chamber will have pumped down and the green READY LED will have illuminated, indicating that the SEM is ready for imaging. 4. Initial Instrument Setup Do not use the buttons or knobs on the Imaging Console control panel unless otherwise told in this SOP to do so. See the SEMTech Solutions SEM Interface Quick Reference Guide for an explanation of the software interface tool bar icons and scan settings. a. Press the green CONSOLE ON button on the right end of the Imaging Console control panel (ICCP). b. Ensure that the FINAL LENS button on the imaging console is on, the CAMERA POWER button is off, the Image Shift, Stigmator and Beam Alignment control knobs on the front panel are set to the 12 o clock position, and that the CONTRAST, BRIGHTNESS, X, Y, SIZE TILT, FOCUS, and GAMMA knobs are all fully counter-clockwise. c. Enter the appropriate information in the LOG BOOK as you proceed. Note the hours on the hour meter on top of the imaging console. If the reading is not the same as what was entered in the log book by the previous user, contact cleanroom staff immediately. d. Start the SEM Interface software (green STS icon.) e. Using the software, set the Gun Voltage to the desired voltage to begin acquiring an image. Application Non-conductive samples Biological specimens, delicate, or heat sensitive samples Non-sensitive, conductive samples Voltage Range 100 to 5000 V 5000 to V to V 2

3 A lower voltage setting usually improves the surface image but also adds noise to the detector signal. For maximum resolution and high magnification work, use 20 kv or above, if the sample allows. The higher the voltage the better the resolution, but the greater the heat that is generated on the specimen. f. If necessary, adjust the BIAS VOLTAGE knob (at knee height on the imaging console, behind a sliding door) to bring the Emission Current to within spec: 45 to 50 µa for voltages up to 10 kv; and 90 to 100 µa for voltages from 10 to 30 kv. g. After about 5 minutes, Check the filament current setting by turning the FILAMENT CURRENT knob (at knee height on the imaging console, behind a sliding door) to about 40, and then turning it back up to the saturation point. See the graph to the right as an aid to find the saturation point; be aware of the false peak. h. If necessary, readjust the BIAS VOLTAGE knob to bring the Emission Current to within spec, as defined in step 4f. i. Using the Mag and Mag + buttons, adjust the magnification to about 50X. j. Use the Condenser button to set the spot size to 5.0 (a higher spot size number correlates to a smaller beam diameter.) k. Adjust the X and Y Beam Alignment sliders to get the brightest image. CONTRAST may have to be decreased to optimize beam alignment. l. Manipulate the stage adjustments on the chamber door to bring the sample into view. Be careful not to contact the collector screen with your sample. Use the (Toggle Chamber View) button on the STS software tool bar to view the inside of the chamber. Press the CAMERA POWER button on the ICCP to provide power to the chamber view camera; press it again to turn it off when you are done. m. Focus the image. Press the AUTO FOCUS button on the ICCP if necessary. n. Adjust the Brightness and Contrast to improve the image visibility. o. Degauss the final lens by clicking the DF icon in the tool bar. Degaussing should be done in approximately 15 minute intervals during operation of the SEM. p. Adjust the Condenser to a spot size of 12. q. Adjust the COLL. BIAS knob on the ICCP to a voltage of XXXXX. r. Check alignment of the apertures. I. Adjust the magnification to 10,000X. II. Click the Partial button for a partial field view. III. Click the W icon in the tool bar to wobble the image. If the image is shifting up and down and/ or side to side, contact cleanroom staff immediately if the final aperture alignment seems to be out of adjustment. A pulsing image is considered normal. IV. Click the W icon again to turn off the wobbler. s. Adjust the Condenser to a spot size of 20. t. Adjust the COLL. BIAS knob on the ICCP to a voltage of XXXXX. u. Correct the beam astigmatism. I. Adjust the magnification to 20,000X. Focus on a round feature for best results. 3

4 II. Click the Partial button for a partial field view. III. Increase the Contrast, and decrease the Brightness. Focus if necessary. IV. Coarse adjust the Stig X to get the sharpest image possible. Repeat with fine adjustment. V. Refocus and repeat the previous step with Stig Y. VI. Press the AUTO STIG. button on the ICCP if necessary. 5. Sample Image Final Adjustments and Image Capture a. If necessary, readjust the Gun Voltage. If a significant change in the voltage setting is made, the FILAMENT CURRENT and BIAS VOLTAGE must be readjusted, as described in steps 4g and 4h, respectively. b. Make necessary adjustments to the Stage, Mag +/, Brightness, Contrast, Focus and any of the other features offered in the software, such as Tilt Focus or Line Scan, as needed. No particular order is required. Switching between scan rates other than rapid scan (RS) will make this process easier. Using the Partial field view can also speed up the process of optimizing your final image, especially when using slower scan rates. Additionally, the following ICCP controls may be used to enhance your image (these controls have no software equivalent): Control GAMMA DIFF LOW PASS FILTER INVERT Description Gamma Control A signal processing feature to bring out the information in the dark regions without excessive loss of information in the light regions. Used primarily to view down holes. The knob should be fully counter-clockwise when not in use. Differential Amplifier button activates the differential (derivative) amplifier, which processes the image to give increased edge contrast. (Slow Scan mode only) LOW PASS FILTER button applies filters to reduce noise from the video signal. (Slow Scan mode only) INVERT button inverts the gray scale of the video signal. c. If necessary, adjust the Condenser (spot size). Generally speaking, use a large spot size (5 or lower) for low magnification work under 1000X magnification. Adjust the Smaller spot size (5 to 20) is used for higher magnifications. d. If necessary, adjust the COLL. BIAS knob on the ICCP. As spot size is reduced (higher number), the collector bias voltage must be increased (and visa versa,) as fewer secondary electrons are generated with smaller spot sizes. e. Select the Scan Rate of your choice. f. Click the Freeze button to prepare for saving your image. The Freeze button will flash during this process and turn solid blue when complete. The time to completion depends on the scan rate. g. Save your image by selecting File Save As... and selecting your preferred save location. Save your images in your group s folder in the Documents folder, preferably in a sub-folder with your name. Images saved to the Desktop or in the Documents top folder will be deleted! 4

5 6. Venting the Chamber for Sample Removal and Putting the SEM in Standby Mode a. Set the Gun Voltage to 0 V. b. Close the SEM Interface software. c. Enter the reading from the hour meter in the LOG BOOK d. Press the red POWER OFF button on the right end of the imaging console. e. Press the VENT button on the VCP. After about 15 seconds, the V2 LED will illuminate and chamber venting will be audible. After about another 15 seconds, the TC2 LED will turn off and, soon after, the door will be ready to open. Use caution when opening and shutting the chamber door. There are pinch points between the door and its hinges. f. When the chamber door has been opened, press the STAND BY button on the VCP to close the nitrogen vent valve (V2). g. Remove the sample mount using the provided driver. h. Close the chamber door and press the EVACUATE button on the VCP to pump down the chamber. Press against the chamber door during the first few seconds of pump-down to ensure that the door seals. After about a minute or two, the chamber will have pumped down and the green READY LED will have illuminated. i. Press the STAND BY button on the VCP to put the SEM in standby mode. 5