Joey’s Sputtering SOP. Based on 11 August 2004 Update of
William R. Evans
Sputtering is one of the most reliable, safe and, in principle, “green” methods of producing thin films of a great variety of materials for research and production. Learning how to use it to deposit thin films congruent with 21st century sensibilities can contribute to the purposes of a BYU education in physics as it is a portion of a capstone, thesis or other research project as prepares the student for service, further education and a career.
This SOP is designed to do ALL of the following:
1. describe general principles in preparation
2. Safety/ hygiene concerns and procedures
3. Scientific/research procedures
4. Clean up (including Waste management and air quality abatement concerns and) procedures
The student must receive training specific and general training.
And witness that they:
1. Completed general training for the lab.
2. Have read and understood this SOP. There is an electronic copy WITH PICTURES of the Sputtering portion only at http://xuv.byu.edu/docs/sops/sopsMain.htm (choose Joey)
3. Reviewed and understood BYU Risk Management recommendations for this system. (Attached.)
4. Have found and understood the pertinent parts of the MSDS manual for information concerning the elements you will sputter.
5. Have read the information sheet specific to the material you will sputter, which THIS lab has prepared, read the on line portions and taken & passed the test for it.
Hazards, Discussions and Mitigations of,
1. Engineering. –
a. From the point of view of sputtering, for most materials sputtered, their most dangerous form would be that which could be ingested, such as a chemical compound which is water soluble, or a fine smoke (fog, fume etc.) that could enter the lungs.
b. Sputtering doesn’t produce such material in such forms in the normal course of operation. It transfers metal from one bulk material (a target) to another bulk form (a thin film on a substrate) through a vacuum
c. And thus the film’s adhesion to the rigid substrate makes the material unavailable for incorporation.
d. However, during some activities such as chamber cleaning the sputtered film material that has reached the wall of the deposition system rather than the can be converted to flakes. As such the flakes typically fairly large, surface area> several mm2. As such they can be fairly easy to capture and immobilized. For example, with the use of a HEPA vacuum.
a. General Principle: All written & ORAL safety & health precautions/procedures have been developed to be in accordance with the current BYU Chemical Hygiene Plan (CHP). If they found to not be in accordance with current CHP. The Current BYU CHP will supersede the procedures here if it more prudent than these procedures.
b. Cleaning inside the system Level 1. You are allowed to do vacuuming of inside with HEPA vacuum if you are trained, following procedure, and using the appropriate PPE.
c. Cleaning inside the system Level 2. YOU are not clean the inside of the sputter system with abrasive methods which could produce dust without training, equipment and permission. It is anticipated that this kind of cleaning only be done every 1-3 years in the course of normal operation, though spot cleaning could be done after we investigate how it might produce dust.
d. A portion of the lab including one table will be designated areas for the use of toxic materials (such as, uranium).
i. It will be treated as such and appropriate chemical hygiene procedures will be followed.
ii. It is to be noted that it is expected that designated area will be cleaned and straightened up (see below) after samples are place in system or removed.
iii. A Part that is removed from the sputter system for storage will be placed in designated, specific container for it.
iv. Particular attention will be paid to activities which could generate airborne particulates.
3. PPE- Personal Protection equipment
a. Principles of hygiene will be followed. Remember & review them.
b. OSHO recommends that “Protective clothing should be worn to prevent any possibility of skin contact.” (http://www.osha.gov/SLTC/healthguidelines/uraniuminsolublecompounds/index.html ) thus,
c. Latex or nitrile gloves should be used in placing samples in the chamber and in touching part of the chamber.
SEE ALSO http://xuv.byu.edu/docs/sops/sopsMain.htm for version with pictures.
1. Engineering controls
Once you have reached as low a pressure as you can with just the turbo and roughing pumps:
1. Check to see that all plugs and connections are secure and safe (including RF connection to the chamber).
2. Turn on coolant water in back (2 valves).
3. Turn on the power switch in the back of panel APCS-3.
4. Turn on all the power switches on the front except the HV Power Switch, the Auxiliary Control Switch, the RF On Switch, and the Incident Control Switch.
These switches include:
a. “Power” Switch
On the Loading/Tuning Box:
On Source A:
c. “Power On” Button (White Button)
d. “Control” Switch
When you turn the “Control” Switch on, the buttons on Source A will light up.
The “Line” Switch is behind the metal cover.
Make sure the switches are set to their normal configurations:
a. Manual Power Control
b. Local Control
On the Loading/Tuning Box:
c. Manual Loading
d. Manual Tuning
On Black Box below Source A:
e. Multimeter set to “PA Plate Current 1 A”
f. PA Tuning set to about 65
5. Wait 2-3 minutes for the power source to warm up.
6. Open the cryopump to ¼ open. (You can do this while the source is warming up.)
To open cryopump:
a. Make sure air valve is open.
on pneumatic switch (light switch-looking thing).
(Cryopump gate will open.)
c. Close air valve.
off pneumatic switch.
(Cryopump gate handle will go slack.)
e. Use cryopump gate handle to close gate until it is ¼ open.
If you want you can wedge the gear in place with a wrench.
7. After you have reached a base pressure, record this on the run sheet.
8. Turn RF Power Control Knob (On Source A) to a minimum.
9. Turn the RF Power Button (Red Button On Source A) on.
10. Turn the HV Power Switch (On CEX-2) on.
11. Set Loading and Tuning to about 108.5 and 150.5 respectively.
Record the Loading and Tuning values on the run sheet.
12. Open the argon valves, and stabilize the pressure at about 3 x 10-3 torr.
The main valve for the argon line is the Green “Nupro” valve behind the chamber. This line also has a Mass Flow Controller, which can be controlled from the box above the Crystal Monitor Readout.
g. If making a metal oxide or a metal nitride, add oxygen or nitrogen.
The main valve for the oxygen / nitrogen line is the “leak” valve on the chamber, above the cryopump.
If you are using the MPA, open the leak valve until you reach the desired gas partial pressure.
If you are not using the MPA, stabilize the pressure at about 7 or 8 x 10-3 torr.
Note: If you are depositing an oxide onto MOXTEC windows, we have found that the oxygen plasma can react with the windows, causing them to break. We have found better success with depositing a thin layer of the pure metal on the windows before depositing the oxide. This protects the windows from the reactive oxygen plasma.
14. Once you have stabilized the pressure, record the operating pressure on the run sheet.
(If you are depositing an oxide or a nitride, record the pressure after adding the argon and after adding the oxygen or nitrogen.)
15. Input the film material # into the Crystal Monitor Readout.
16. Turn the RF Power Control Knob (On Source A) to about 200 Watts (0.2 kW) of Incident Power (as read off of the Incident Power readout On Source A).
17. Adjust the RF Power Control Knob and the PA Tuning Knob (Slightly!) to maximize the Incident Power and minimize the Reflected Power.
The Incident and Reflective power represent the power going into the impedance source (the sputter gun) and the power coming out from this source back into the RF power supply, respectively. By maximizing Incident power and minimizing Reflective power, the output power from the RF power source is efficiently consumed.
Eventually, a plasma will be created inside the chamber. When a plasma is first created, the reflected power readout should drop sharply (although it might not be by very much). Also, when there is a plasma in the chamber, you should be able to see a faint purple glow in the chamber through the glass Ion Gauge.
Once a plasma is created, sputtering off of the target has begun. You can adjust the power until you get a good sputter rate (as read off of the Crystal Monitor Readout). A good sputter rate depends on the material. For pure metals, this is about 1 or 2 Å / sec. For oxides, this is about 0.2 Å / sec.
18. Record the sputter rate on the run sheet as read off of the Crystal Monitor Readout.
19. Once you have established a good rate, open the Shutter and press “Start” on the Crystal Monitor Readout.
The Crystal Monitor Readout will count the total film thickness deposited after you pressed “Start” as measured from the crystal monitor (this will not be perfect, but it is a good, rough value).
20. Once you reach the desired film thickness, close the Shutter and press “Stop” on the Crystal Monitor Readout.
21. Record the total film thickness on the run sheet as read off of the Crystal Monitor Readout.
22. Once you are done, turn the RF Power Control Knob to a minimum, and turn off all power switches.
23. Close the argon (and oxygen or nitrogen if applicable) tanks.
24. Wait a couple of minutes so that the gas in the argon and oxygen or nitrogen lines is vented into the chamber.
25. Tightly close the argon (and oxygen or nitrogen if applicable) valves. (Also, if applicable, shut off the Mass Flow Controller.)
26. Close the gate valve to the cryopump.
To close cryopump:
a. Remove wrench (if applicable).
b. With the air valve still closed, turn on the pneumatic switch (the light switch-looking thing).
c. Open the air valve.
The gate valve should open completely.
d. Turn off the pneumatic switch.
The gate valve should close completely.
Paperwork must be completed.
1. See below.
Clean up: (This is an essential part of deposition work. Deposition sheet has place to note that each step of clean up has been done. It must be signed and dated. Failure to do this is responsibly can lead to a diminishment of lab permissions. You may take time to take sample to analysis but system and staging areas must be cleaned up promptly.)
1) Lab: locate and clean up contaminated areas in the lab. Using the HEPA filter vacuum
a. Look for evidence of metal flakes etc.
b. For thorium and uranium, these surveys could be done using a thin window Geiger-Mueller counter.
c. Any evidence of contamination of accessible parts of the lab (floors, tables, outer surfaces of equipment) must be cleaned..
2) Follow disposal procedures for all potentially contaminated materials and write on deposition that has been followed.
3) personal hygiene This should include:
a. Washing hands after removing gloves or completing a process and at the end of each work day when leaving the laboratory. For particulate generating tasks, lab coats, sleeve covers, or coveralls are recommended to protect employees’ clothing from contamination. The type necessary is dependant upon the task and scope of potential contamination.
Check out/ straightening up Check list:
1. _______ Are tools put back in the tool box? ____
2. _______ Are parts back in system or designated storage areas?
3. _______ Has all contamination been cleaned up? Count rate______ CR (bkg.)____
4. _______ Geiger counter put away?
5. _______ Are gloves, chem. Wipes etc. disposed of appropriately?
6. _______ Lab straightened up?
7. _______ Hands washed?
8. _______ PPE re-stowed?