Electron Beam Evaporator Protocol

Electron Beam Evaporator Protocol (V_1.0)

– Lingyun

Here is the first version protocol of the electron beam evaporator at RIT clean room. There is not too much to put down here – the best way to learn this is to attend the training facing the real machine tool. I will try to provide some photos later when I get the chance to take photos in the clean room.

1. Sample substrate(s) and metal source(s):

– If you are coating a full wafer, it is fine. For separated membranes, however, find a dummy 4” wafer and attach the membranes on it using double sided tape.

– Bring our own metal(s) to RIT – do not use their metal(s) unless committed. This includes the crucible(s) as well as metal(s). Remember to take them back after finishing the evaporation process.

2. Peripheral check:

– Before starting the machine, make a peripheral check. This includes the water supply, N2 gas supply, current vacuum level, and crystal life time check. (photos will be provided accordingly)

3. Start venting the machine:

– First swipe in the clean room computer system – this ensures all the supply is ON. Then switch the operation button to “vent” position.

4. Load substrate(s) and metal(s):

– Wait for fifteen (15) minutes before the vacuum chamber jar is automatically lifted up. Carefully take the 4” wafer sample holder out of the chamber. Assemble your substrate(s) into the sample holder (facing down) and put it back in the machine chamber.

– Load in your crucible(s) with metal(s) sitting inside. There are positions for crucibles at the bottom of the evaporator chamber. If you are using more than one metal source, make sure the sequence is correct – the crucible positions are normally rotated counterclockwise.

5. Start pumping the machine:

– First clean the edge of the chamber jar – this will give you a good vacuum during evaporation. Then switch the operation button to “pump” position.

– Make sure the mechanical pump switch is at the “ON” position – otherwise switch it ON. This is the roughing pump and it must work before the high vacuum ion pump works.

– Observe the vacuum level reaching beyond 1 e -2 Torr. Then the ion pump should work and the “high vacuum” indicator should be lighted. Now you can switch OFF the mechanical pump.

6. Indicate the machine status:

– Usually it takes more than two (2) hours to reach a good chamber vacuum level for deposition. You may leave the clean room after starting pumping and wait for two hours before your return. However, make sure you put a “Yellow notice” beside the machine chamber. A “Yellow notice” indicates that the machine is currently in use. Please provide your name, contact, and the process information in the notice.

7. Start deposition:

– Check the vacuum level is in the range of [1 e -7, 1 e -6] Torr. This is good enough for evaporation.

– Program the embedded processor in the dashboard. You need to input the material density, z-number, and machine tooling factor. All these information can be found in a brochure on the machine stage. Press the “program” button in the dashboard to enter the programming mode. Use arrow keys to switch parameters. Enter correct numbers for each parameter and press the “enter” button to update it. Finally make sure the parameters are properly triggered by pressing the “program” button again to exit the programming mode.

– Switch ON the sample holder rotation motor – it provides better film uniformity when the holder is rotating during deposition.

– Turn ON the “XY position” and “amplification” functions – these are parameters of the electro-magnetic system, which is used to control the electron beam to heat your metal source. Normally, you do not need to adjust the values – just turn ON them.

– Turn ON the “thermionic” switch. This is the power supply of the thermionic filament, which generates hot electron beam when heated up.

– Turn ON the current control function. Increase the thermionic filament current from zero (0) to about 0.1 mA. Make sure you press the “open” button in the program processor dashboard just before you do this. There should be deposition rate and total deposited film thickness information on the dashboard display panel. Adjust the current accordingly to target a good deposition rate of about 0.5 ~ 1.0 angstrom per second.

– Keep monitoring both deposition rate and total film thickness. Before it will reach your target thickness, properly reduce the thermionic filament current such that the target thickness is reached when the current is off.

– If you need to coat more than one metal, rotate the crucible holder and switch to another metal source. Then repeat the above procedures until all the metals are coated on your substrate(s).

8. Unload substrate(s) and metal(s):

– When all the deposition is finished, switch OFF the sample holder rotation motor, “XY position” and “amplification” functions, and the “thermionic” switch.

– Switch the operation button to “vent” position. Wait for fifteen (15) minutes before the vacuum chamber jar is automatically lifted up.

– Carefully take the 4” wafer sample holder out of the chamber. Take out your substrate(s) from the sample holder, and then return it back in the machine chamber.

– Remember to get back you crucible(s) with metal(s) sitting inside.

9. Pump the chamber and leave:

– You must pump the machine chamber to vacuum status before you leave. Repeat the procedure “5. Start pumping the machine”. When the high vacuum fine pump works you can return to UoR with your samples and metals.

– The last important thing – make sure you SWIPE OUT the clean room computer system – OTHERWISE WE KEEP PAYING TO RIT WITHOUT DOING ANYTHING!

Good luck and have fun with the e-beam evaporator machine.