DEEWONG-2000: 4 sources electron beam evaporator

Ebeam Evaporator Standard Operating Procedure – Revision 04

Author:
Rev. 00: David Webster, TRIUMF, October 22, 1993.Evaporator_e-beam
Rev. 01: A. Schmalz and W. Chao, April 26, 1999.
Rev. 02: Doug Wong, 2000
Rev. 03: Mario Beaudoin, April 2006
Rev. 04: Mario Beaudoin, April 2013

Purpose: To describe how to use the evaporator for Physical Vapor Deposition (PVD) by Electron Beam and Resistance Heating. This is an Airco Temescal evaporator modified and automated by Doug Wong in 2000 and is commonly known in the AMPEL facility as the Evaporator 2000 system or the DeeWong Evaporator. This SOP is meant to be used by properly trained operators only.

Introduction
The Evaporator 2000 system is an automated vacuum process control system for Physical Vapour Deposition (PVD) of metals, and non-metals, consisting of a control cabinet, chamber cart, E-Beam power supply cart, Cryo pump compressor cart and mechanical vacuum pump.
The control cabinet houses a microprocessor, operation control panel, Ion and thermocouples gauges controller, Inficon Film thickness monitor, CTI Cryo pump temperature monitor, Airco CV8 Electron Beam control module and various other minor control electronics. The automation allows users to operate the Evaporator 2000 with minimal training and is interlocked for system failsafe.
The chamber cart, situated next to the control cabinet, consists of a chamber backed by a CTI Cryo-Torr 8 pump and vacuum valve system. The chamber hoist, contactor panel, Glow-Discharge transformer, Thermal Resistance Heating transformer and Electron Beam Gun transformer are also located on the cart. Located on the right side of the
chamber is the Thermal Resistance Heating power control Variac and this is interlocked to operate only when the chamber is under evaporation mode. To the left of the chamber, is the knob for E-beam Gun turret, permitting selection of up to four sources and to the rear, the manual shutter control.
The access panels on the sides of the cart are interlocked to cut power to E-Beam Gun and Thermal Resistance if any are removed.
The E-Beam supply cart along with the cryo pump compressor and mechanical pump are controlled by the micro processor in the control cabinet via remote contactor panel which are all located outside the cleanroom.

Operation
To begin, check to make sure:

  • the Water supply valve is open,
  • the Nitrogen supply line is connected,
  • the Compressed Air line is connected,
  • the Power cord to controls and E-Beam power supply are plugged in.

Turn “System” power switch “ON”, Ion Gauge Controller “ ON “ (NB: do not turn on the ion gauge unless the thermocouple gauge for the main chamber indicates that the chamber is under vacuum),

A. INITIAL START-UP OPERATION:
This procedure is normally not necessary and should only be done by the Cleanroom Engineer, unless instructed otherwise.

  1. Press “Main On” switch.
  2. Mechanical pump turns on and automatically performs the following steps
    1. Foreline Valve opens (after a 2 second delay)
    2. After 10 – 15 minutes the vacuum should drop below 100mT
    3. Mechanical pump & Foreline valve will close
    4. Cryogenic (Cryo.) Compressor turns on (after a 2 second delay)
  3. There is then a time delay of 2.5 hours before System Ready to use, that is, when Cryo. Pump is cold (Cryo. pump temperature gauge is below 50 Kelvin)

B. HOIST OPERATION
Select up or down to raise or lower chamber only when vented (Interlocked to operate only when chamber is not under vacuum).

  • TO RAISE: Turn and hold knob clockwise to desired height.
  • TO LOWER: Turn and hold knob counterclockwise.

Before lowering the bell jar, make sure that the sealing O-ring is clean and free of obstruction; clean the O-ring with a clean wipe and iso-propanol as required.

C. PUMP DOWN CHAMBER OPERATION

  1. Set up substrate and evaporation material and lower bell jar
  2. Press “Pump Down” switch which automatically starts the following sequence:
    1. Mech. pump starts up
    2. Rough valve opens (after 4 second delay)
    3. OPTIONAL: Press “Glow Discharge” switch; To stop “Glow Discharge”- press & hold switch for 2 sec.
    4. When vacuum drops below 1.0×10-1, shown on the Chamber TC Meter, the Rough Valve & Mechanical Pump turns off
    5. Glow Discharge” turns off automatically
    6. Gate valve opens (Loud Noise!!) NEVER LEAVE THE ROOM UNTIL THE GATE VALVE HAS OPENED
    7. Water valve turns on; make sure the manual valve is turned on at the wall
  3. At this point, the ion gauge filament may be turned “ON” by pushing the switch on the controller (the controller will read the pressure if there are no errors)
  4. At this point, if the pumpdown is to precede a deposition, it is a good idea to look at the INFICON thickness monitor to make sure it is functioning (ie. Does not read “Xtal Fail”). The INFICON monitor works best when the power is kept ON continuously, please do NOT turn it OFF
  5. It should take about an hour for the pressure to reach 5×10-6 Torr required for evaporation.

Glow discharge creates a ionized gas plasma, which can aid in cleaning chamber surfaces prior to processing. Not recommended for substrates with electronic device features.

D. VENT CHAMBER OPERATION
Thin films and their sources should be allowed to cool at least 15-30 minutes to avoid oxidation or nitriding upon venting.

  1. Turn off ion gauge Filament, by pushing the switch on the controller; (the IG reading will be replaced by hyphens —-)
  2. Press “Vent “ switch & hold for 2 seconds which starts the following automated sequence:
    1. Gate valve, water valve, E-beam & filament turn off
    2. LOUD NOISE!!
    3. Vent valve opens (after a 2 second delay), chamber slowly filled with Nitrogen.
  3. After chamber reaches atmosphere,
    1. Vent valve closes
    2. Ventn switch light turns off
    3. Chamber can now be lifted
  4. Clean inner viewport with acetone and a clean wipe (to do so, remove the outside viewport).
  5. Vacuum the inside of the evaporator

Replace viewports, lower the bell jar and Pump down the system

E. RESISTANCE AND E-BEAM EVAPORATION OPERATION:

  1. Turn on Ion gauge Filament if required
  2. Turn on “INFICON” system if you have not already done so. With “PG” and “E” buttons, enter the following parameters:
    1. Density,
    2. Z ratio,
    3. Tooling Factor (if desired and if proper calibration has been performed beforehand).
    4. The Density and Z-ratio of various evaporation materials are found in the INFICON binder and reproduced on the Table taped in front of the evaporator.
    5. NB: hit “PG” button to access the parameters menu; the “E” button is both the “Enter” key and the scroll down button; the “C” button is the scroll up button
    6. Hit “PG” again to get back to the monitoring/process window
  3. Press “ E-Beam/Evap” switch to start operation:
    1. E-Beam CV-8 Control Panel will power on if water flow is present & Vacuum is below 100 microns
    2. Thermal heater will power on

For Resistance Evaporation

  1. Turn up Variac Power Supply Control to 10-20 % to warm up (the filament will glow red)
  2. Adjust Power Supply control until evaporation begins on the thickness monitor, move shutter, allow deposition until film thickness attained or all source material evaporated. Return shutter over thermal source.
  3. Turn Variac Power Supply to 0.
  4. Wait at least 15 minutes (½ hour if materials with a high thermal mass were used) before venting chamber to allow cooling of charge and thin film

For Electron Beam Evaporation:

  1. Make sure both “HV” and “FILAMENT CURRENT” control knobs are fully zeroed.
  2. Turn CV-8 key to “On” position. Push “HV” button On. Push filament “On”
  3. Slowly increase the emission current. Beware: the evaporation has a diode-like turn on characteristic. Typically for materials in a graphite crucible this will be at Emission Control between 0.4 DC amps, and 0.6 DC amps. for materials charged directly into the water cooled copper hearth.
  4. Wait for material to begin evaporation. A melt pool can be seen with some metal but not all; not so for dielectrics
  5. Start crystal measurement. Set emission power
  6. Open shutter …… close shutter to get the correct thickness.
  7. Turn filament current to zero (very slowly for metals that wet the crucible to avoid breaking the crucible). Turn off filament and HV. Turn key off
  8. If more materials is to be done:
    1. Wait 10 minutes for the crucible and hearth to cool off
    2. move to new charge/source and repeat steps 1-7 above
  9. Wait at least 10 minutes (20 minutes if materials with a high thermal mass were used) before venting chamber to allow cooling of charge and thin film

To STOP Either Evaporation operation:

  1. Press & hold “E-Beam/Evap” Button for 2 seconds
  2. This will deactivate power to EB Gun and Thermal Power Supply

Follow steps in section D to remove sample.

F. STAND-BY AND SHUT DOWN OPERATION:
The stand-by and shut-down operations should only be performed by a cleanroom engineer as the system should normally be left under pump down (section C).
Press “Main Off “ switch

  • All valves and pump turns off except for Hoist and Cryo. Pump
  • Turn off “System Power” if complete shut down is required

TROUBLESHOOTING PROCEDURE:
If you are experiencing any difficulties with the vacuum process system, first check the following…

  1. Water supply is on
  2. Air line supply is on
  3. Power to chamber cart
  4. Power to control cabinet
  5. Power to remote contactor panel
  6. Vacuum to cryo pump is below 100 microns

If all the above conditions are met and there still is a problem, the best course of action is to report the problem to Nanofabrication Facility personnel.

MAINTENANCE PROCEDURE

  • Cryo pump and compressor per CTI- Cryogenics Cryo-Torr 8 service manual, section 7
  • Mechanical pump; oil level check periodically, monthly inspection of oil condition for colouration or smell. Change as required.
  • Micro processor: back-up battery ( Omron # 3G2A9-BAT08 ) replacement every five years per Omron CQM1 Operations Manual Cat.W226-E3-2 section 2-1-7
  • Yearly electrical system checks for loose wiring and overall performance of system.

SYSTEM DRAWINGS AND SCHEMATICS

Evaporator-DeeWong Ebeam Drawings-Schematics

Table of density and z-ratio for common materials

Density and z-ratio table