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SEM LEO 1550 manual

SEM LEO 1550

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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.

Saved pictures are available on STI network (EPFL local or VPN):
\\sti1files\cmi-transfert\Z01-Zeiss-Leo

Table of content: CMI

  1. Introduction
  2. Access conditions
  3. Basic operation
  4. Photos galery

I. Introduction CMI

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
Different SEM holders
Figure 1: Different SEM holders

  • 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)
Scematic view of the GEMINI column
Figure 2: Schematic view of the GEMINI column

GEMINI column

The GEMINI columns electron source is a Schottky Field Emission type made of tungsten and Zirconium (ZrO2). Two secondary electrons detectors have been installed: 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:

II. Access conditions CMI

  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 CMI

  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)
Software tools bar

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
Continuous averaging
1, 2, 3 : bigger is the number longer is the averaging
4
  • Full frame scan
  • Reduced raster
  • Split scan
  • Scanning dialog
  • Appertures dialog
  • Detectors dialog
5
  • Stigmation setting
  • Brightness/Contrast
  • Switch camera/detector
  • Detector selection
  • Magnification/Working distance (= Focal Distance)
  • Aperture alignment setting
  • Auto-contrast and brightness
  • Detectors dialog
  • Detectors dialog
  • Auto focus and stigmatisme
6
  • Save picture (increase the picture number automatically)
  • Print picture
  • Save Image dialog
  • Printer dialog
Figure 3: Software tools bar

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 initial airlock state
2. Initial airlock state, everything is closed
unlock the front door unlock the black slider
3. Open the number 1 (unlock the front door) 4. Unlock the black slider by pulling out the number 2 button.
slide the door open the door
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
screw your holder return 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 	lock the door
10. Lock it with number 1 (the door must be closed tightly to avoid leaks during pumping)
11. Click on the Specimen Change via Airloock button (cf. Figure 3) vacuum is good enough
12. Wait for the green light (= vacuum is good enough to open the door between the airlock and the main chamber)
open the valve between the chamber and the airlock insert your sample(s)
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 its 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. close the airlock/chamber door
16. Close the airlock/chamber door (5) valve with and lock (6)
resume exchange button
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)
Extra High Tension (EHT)
Figure 4: EHT On

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.
  1. Switch on the InLens by clicking on the appropriate button an the tools bar (cf. Figure 3)
  2. Click on the Magnification and WD tools and reduce the Magnification to the minimum
  3. Set the WD at 5 mm (double click on the WD value on the white data bar on the bottom of the screen)
  4. 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 its 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 dont do the adjustments on important structures because by scanning the surface we affect it (especially with insulators and polymers).
  1. Set the Brightness and the contrast (cf. Figure 3)
  2. Press shift + F2 to recalibrat the deflection system hysteresis
  3. Set the WD more accuracy with the mouse (now it should be between 3 and 7 mm).
  4. To obtain sharp pictures you have to do a 3 steps sequence 2 or 3 times (depending on the final resolution needed):
    • 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).
    • Effect of the stigmation default Effect of the stigmation default
      Figures 5 and 6: Effect of the stigmation default

    • 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.
    Apertures dialog
    Figure 7: Apertures dialog
Tip: As long as you dont change any fundamental parameters on the system like EHT, aperture or observation plane you dont have to do these settings again (except the WD).
  1. Now you can zoom out and move where you want on your sample.
  2. To reduce the noise we can use 2 different averagings:
    • Continuous averaging: Do an averaging with several frames with a short electron beam exposition time. Its particularlly useful with insulator or polymer to reduce the charging effects and the surface affectation (cf. Figure 3).
    • 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).
  3. When you are happy with the picture quality you can start the distance estimations with the annotation tools (Below the Data Zone).
  4. 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 (go in Settings to change the next 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.
Save image dialog
Figure 8: Save image dialog

Stage movements

With the remote control

Remote control
Figure 9: Remote control

With the mouse

Keybord shortcut

IV. Photos galery CMI

Dont break it when you load it into the airlock Exchange position
Figure 10: Be careful with cleaved samples.
Dont break it when you load it into the airlock
Figure 11: Exchange position
Initial sample position inside the chamber Deep silicon etching
Figure 12: Initial sample position inside the chamber Figure 13: Deep silicon etching
Dry etch of AlSi(1%) Deep fused silica etching (40 µm)
Figure 14: Dry etch of AlSi(1%) Figure 15: Deep fused silica etching (40 µm)
Silicon submicrometric pillars
Figure 16: Silicon submicrometric pillars