SEM LEO 1550 MANUAL RESERVATION POLICY: 2 booking slots maximum per day and per person (ie. 1h). 6 booking slots maximum per week and per person (ie. 3h). Reservation names must correspond to the operators. I. Introduction Generality The CMI SEM LEO 1550 is composed of one GEMINI column (cf. Figure 2), one process chamber with a motorized stage on 5 degree of freedoms (X, Y, Z, Tilt and Rotation) and one airlock. You can use 4 diferents holder according to the needs (cf. Figure 1). (1) for small sample(s) which are fixed with the help of a conductor double side adhesive (2) for cleaved sample(s) (3) for 150 mm wafer (4) for 100 mm wafer Figure 1: Different SEM holders 1
the Field Emission Gun (3), which provides the source of the electron beam the Condenser Lens (7), used only in special operating modes the Beam Booster, composed of Anode (5), Vacuum Tube (6), Apertures (8), Alignment Coils (9a, b, c), Stigmator (13), and Isolating Valve (15) The GEMINI Objective Lens (10,11) which focuses the electron beam onto the specimen (12), also containing the Deflecting System (14) Figure 2: Schematic view of the GEMINI column GEMINI column The GEMINI column s electron source is a Schottky Field Emission type made of tungsten and Zirconium (ZrO2). Two secondary electrons detectors have been installed: InLens: installed inside the column (high resolution detector). SE2: installed out of the column axis (better topography visualization). The chamber vaccum (few 10-7 mbar) is held thanks to a couple primary/turbomolecular pumps and the secondary vaccum (few 10-10 mbar) is held thanck to an ionic pump. The GEMINI column advantages: We can use a low electronic acceleration from 0.5 kev to several kev according to the sample. So the charging effects dues to the insulators materials are limited. Both detectors are complementary and it s very easy to compare these performances. II. Access conditions 1. The CMI SEM LEO is reserved to the regular CMI users. 2. It is exclusively reserved to the control of processes which have been done with the CMI installation. 3. The maximal booking time per day is 1 hour (so 2 slots). 4. Saved pictures are available on STI network (EPFL local or VPN): "\\sti1files\cmi-transfert\z01-zeiss-leo". III. Basic operation 1. Login on the zone computer 2. Login on the SEM control computer 3. Place your sample(s) on the appropriate holder 4. Load your sample into the SEM airlock 5. Start the "Specimen Change via Airlock" routine (button 1 Figure 3) 6. Load the holder into the chamber (cf. Sample loading and unloading) 7. Set the SEM (cf. Sample observation) 8. Observe your sample(s) (cf. Sample observation) 9. Unload the holder into the airlock (cf. Sample loading and unloading) 2
nb Left Button (LB) Middle Button (MB) 1 Specimen Change via Airloock Resume exchange 2 Stage initialize Stage stop 3 Pixel averaging 1, 2, 3, 4 : the larger the number longer is the averaging 4 Full frame scan Reduced raster Split scan 5 Stigmation setting Brightness/Contrast Switch camera/detector Detector selection Magnification/Working distance (= Focal Distance) 6 Save picture (increase the picture number automatically) Print picture Figure 3: Software tools bar Continuous averaging 1, 2, 3 : bigger is the number longer is the averaging Scanning dialog Appertures dialog Detectors dialog Aperture alignment setting Auto-contrast and brightness Detectors dialog Detectors dialog Auto focus and stigmatisme Save Image dialog Printer dialog Sample loading and unloading Initial SEM state: The EHT is off and the airlock is at atmospheric pressure. Loading 1. Install your sample(s) on the appropriate holder 2. Initial airlock state, everything is closed 3. Open the number 1 (unlock the front door) 4. Unlock the black slider by pulling out the number 2 button. 3
5. Slide the door by holding it with the black part and lift at the same time to avoid vibration. Once you start to move the black part release the number 2 button. Continue to move the black slider until the number 2 locks again 6. Release 3 and open the door 7. Screw your holder on the transfer arm 8. Return the door parallel to the load lock 9. Release 2 and slide the door by holding it with the black part and lift it at the same time to avoid vibration on the sample till the number 2 is locked again 10. Lock it with number 1 (the door must be closed tightly to avoid leaks during pumping) 4
11. Click on the Specimen Change via Airloock button (cf. Figure 3) 12. Wait for the green light (= vacuum is good enough to open the door between the airlock and the main chamber) 13. Open the valve between the chamber and the airlock with number 5 and 6 14. Insert your sample(s) onto the stage rail. The loading arm must stop at the beginning of the white tape. If you can go further it s because the holder has not loaded properly onto the stage (so retry to load it). 15. Unscrew the loading arm and pull it out from the chamber. Make sure the loading arm is properly unscrewed from the holder. 16. Close the airlock/chamber door (5) valve with and lock (6) 5
17. Click on the Resume Exchange button Unloading 1. Start by clicking on the Specimen Change via Airlock button (check before if the front door is properly closed, cf. Figure 3) 2. When the green light is lit open the valve between the airlock and the chamber 3. Insert the transfer arm 4. Screw on the holder 5. Extract the arm to the maximum 6. Close the valve between the airlock and the chamber 7. Click on the Resume Exchange button (cf. previous part step 17) 8. Unlock the door with the number 1 9. Wait untill the airlock reach the atmospheric pressure 10. Slide out the door by holding the black part and lift it at the same time to avoid vibration of the sample till the number 2 is locked again 11. Open the door with the number 3 12. Enscrew your holder from the transfer arm 13. Close the airlock as you will pump it again before leaving 14. Close the door 15. Slide the door by holding the black part till the number 2 is blocked again 16. Lock it with number 1 Sample observation 1. Start the Extra High Tension (EHT) on the software bottom right corner (cf. Figures 4) 2. Figure 4: EHT On 6
Tip: Insulating Samples - When you click you first switch the EHT on the accelerating voltage will be set to 3 kev. If your sample is an insulator to avoid charging effects it may be better to reduce the acceleration voltage to around 1 kev. In the worst case if you need to observe a polymer this voltage can be reduce to 0.5 kev to avoid your structures collapsing too fast (basically to still have time to do the settings and pictures). It is often also helpful to reduce the current of the electron beam. Reducing the current reduces the number of electrons hitting your sample in a given time. To reduce the current you need to choose a smaller aperture. The default aperture is 30 µm try reducing this to 10 µm. When you reduce the acceleration voltage the SEM resolution drops and adjusting the alignment could be harder. When you reduce the aperture size the brightness and contrast will reduce and your image will become noisier. 2. Switch on the InLens by clicking on the appropriate button an the tools bar (cf. Figure 3) 3. Click on the Magnification and WD tools and reduce the Magnification to the minimum 4. Set the WD at 5 mm (double click on the WD value on the white data bar on the bottom of the screen) 5. Reduce the distance between the sample and the column by moving the stage on the Z axis untill the picture is sharp (cf. Stage movements) Tip: Sometimes it s a bit difficult to find structures on the sample surface to adjust the alignments. You can usually find some on the edge of the sample. We usually don t do the adjustments on important structures because by scanning the surface we affect it (especially with insulators and polymers). 7. Set the Brightness and the contrast (cf. Figure 3) 8. Press shift + F2 to recalibrat the deflection system hysteresis 9. Set the WD more accuracy with the mouse (now it should be between 3 and 7 mm). 10. To obtain sharp pictures you have to do a 3 steps sequence 2 or 3 times (depending on the final resolution needed): o Increase and decrease the WD and try to see the stigmation default. If you cannot see it zoom in and try again till you see it (depends on the final resolution need, cf. below). Figures 5 and 6: Effect of the stigmation default o o When you have highlighted it set the WD in such a way that you have set it just in the middle of the 2 privileged directions. Set the stigmatism thanks to the encoders or with the mouse in coarse mode (left mouse button on the appropriate icon, cf. cf. Figure 3) in order to have the better picture as possible Then open the Apertures dialog (SEM Control -> Apertures or medium mouse button on the appropriate icon, cf. Figure 3). Start the focus wobble and try to stop the picture movement with the Aperture Alignement setting. Again you can use the encoders or the mouse in coarse mode to perform it. 7
Figure 7: Apertures dialog Tip: As long as you don t change any fundamental parameters on the system like EHT, aperture or observation plane you don t have to do these settings again (except the WD). 11. Now you can zoom out and move where you want on your sample. 12. To reduce the noise we can use 2 different averagings: o Continuous averaging: Do an averaging with several frames with a short electron beam exposition time. It s particularlly useful with insulator or polymer to reduce the charging effects and the surface affectation (cf. Figure 3). o Pixel averaging: Do an averaging pixel per pixel by increasing its electron beam exposition time. It gives good results with conductor and semiconductor (cf. Figure 3). 13. When you are happy with the picture quality you can start the distance estimations with the annotation tools (Below the Data Zone). 14. To save picture go in File -> save image. The file name is composed of a prefix and a suffix. The prefix is write in the File name and the suffix is a number. When you have specify once the file name and the directory you can just press on the appropriate button on the tools bar (cf. Figure 3) to save a new picture by increasing the suffix number. Figure 8: Save image dialog 8
Stage movements With the remote control 2 joysticks: right to move X, Y, Rotation and left to move Z and Tilt. Figure 9: Remote control With the mouse Press Ctrl + tab on the keybord them you centred your sample where you click on the picture Press Ctrl + shift + tab on the keybord them you can drag a rectangle on the picture and the system will automatically zoom in and centred your sample into it. Keybord shortcut Ctrl + d : data zone display it/ hide it + (numerical keybord) : increase the scaning rate - (numerical keybord) : decrease the scaning rate tab : fine/coarse mode F3 : dialogs display them/hide them Ctrl + tab : you centred your sample where you click on the picture Ctrl + shift + tab : drag a rectangle on the picture and the system will automatically zoom in and centred your sample into it Shift + F2 : recalibrat the deflection system hysteresis Ctrl + A : annotation tools 9
IV. Photos galery Figure 10: Be careful with cleaved samples. Don t break it when you load it into the airlock Figure 11: Exchange position Figure 12: Initial sample position inside the chamber Figure 13: Deep silicon etching Figure 14: Dry etch of AlSi(1%) Figure 15: Deep fused silica etching (40 µm) Figure 16: Silicon submicrometric pillars 10