CHA Sputtering System Operation

Starting Point:

Assume that the chamber is pumped down with no gas flow and no power to either cathode. (This is the condition that the system should be left in each time after use).

The operator should verify that the mechanical pump and the cryo pump are operating properly by checking the manual gauge, the thermocouple gauge TC1 (Mech Pump), and ion gauge IG1 (Cryo press) before proceeding any further. Now is also a good time to verify that the sputtering gas(es) are on (at the supply bottle(s)) and to add liquid N2 if desired.

To Vent the System:

1. Ion Gauges IG1 and IG2 should be off.
2. Auto Control Switch should be in Standby.
3. Wait for the light to come on on the `Fore' Switch (10-15 second delay).
4. Change Auto Control Switch to Vent.
5. Release latch (red handle) on chamber door.
6. When you hear the venting gas escaping, change Auto Control Switch to Standby.

To Change Substrates:

May be done with rotating platen mounted to door or removed from door. Be cautious when working with the platen when it is mounted to the door to avoid damage to the rotating support rod.

To Remove Platen:

1. Carefully remove clip at the back of the platen.
2. Slide platen off the rod and place it on the holder on the workbench.

To Replace Platen:

1. Carefully slide platen onto support rod.
2. Carefully align the hole in the rod with the hole in the mounting flange and replace the clip. Rotating the rod using the Motor Control may help with alignment.

To Change Targets:

This should be done by one of the superusers unless otherwise authorized. The DC cathode in particular must be assembled correctly to avoid arcing.

With the chamber door open:

1. Remove the gas manifold.
2. Loosen the screws which retain the outer shield,
3. Open the shutter(s) to allow the outer shield to be removed.
4. Rotate and slide off the outer shield. Then slide off the inner (dark space) shield.
5. Remove the screws which hold the retaining ring.
6. Remove the retaining ring, target and the conductive (rubber) mat.
7. Place the conductive mat on the back of the new target.
8. Place the target on the cathode, making sure that the conductive mat is centered.
9. Replace and tighten the screws holding the retaining ring in an alternating pattern until all are snug.
10. Check around the edge of the target to make sure that the conductive mat is centered properly. Use the small (dental) mirror to see the mat all around the edge of the target. If the mat is not centered, remove the retaining ring and repeat steps 7-10. It is better to get it correct at this point than to have to do it over after waiting 15 - 20 minutes for the system to pump down.
11. Replace the inner (dark space) shield making sure to leave a gap of approximately 3/32" (2.4 mm) between the shield and the retaining ring. Make sure the gap is even all around. Use a small allen wrench between the shield and the retaining ring to help in getting an even spacing.
12. Replace the outer shield and tighten the screws. Finally, replace the gas manifold.

To Pump Down the System:

1. Close the door and engage the latch (red handle).
2. Change the Auto Control Switch from Standby to Start. There will be a 10 - 20 second delay before the system will start to pump down. The mechanical pump will rough the chamber first, then will switch to the cryo pump (Hi Vac).
3. Verify that the Variable Orifice Switch is in the Open position.
4. Wait until the chamber pressure is 5 x 10-6 or lower before attempting to sputter. You can check the chamber pressure by using ion gauge IG2. When the system is clean, it takes approximately 15 - 20 minutes to pump down.
5. You may add liquid N2 to reduce pumping time, however the LN must be added and the cold trap temperature should be A allowed to stabilize before pumping the system down. You must find your own source of LN (it won't be provided by the IC Lab). The cold trap capacity is 2.2 liters.

To Do RF Sputtering (Cathode 1)

First you must set the parameters (Setup) then do the actual sputtering run (Operation). The RF Power Supply is the unit at the lower left hand portion of the control panel. It has a blue LC menu display and a large knob to change the menu settings. There is a key on the left side of the panel which must be in the Auto mode to change the menu settings. At the upper left hand portion of the control panel there is the RF Controller (Tuner). It should not be necessary to adjust any of the settings on the tuner in normal operation. If the Reflected Power is too high, it may be necessary to adjust the tuner. If this is the case, turn the RF power off and contact one of the superusers for help.

For the Setup section, Menu Settings are the values that appear in the menu display and Switch are the buttons pushed to select a value or back up to a previous menu.

Setup:

1. Turn the knob until the Configure menu appears.
2. Press Select (located on the right side of the knob)
3. Should see Power Program Setup (turn knob if necessary until it appears).
4. Press Select.
5. Should see Setpoint Parameters (turn knob if necessary).
6. Press Select.
7. Should see Forward Pwr 1. To change the value, press Select.
8. When value is flashing, turn knob to change the power. Press Select to set the value.
9. Turn knob to see Forward Pwr 2 if you want to use two power settings. The value can be set in the same manner as steps 7 and 8. When done with the power settings, press Back to go back to the Setpoint Parameters menu.
10. Turn knob to see
11. Run Time Parameters, press Select.
12. Set Run 1 Time in the same manner as Forward Pwr 1 (steps 7 and 8). The run time is displayed in Hours:Minutes:Seconds.
13. When finished setting power, run time, limits, etc., return to the main menu by pressing Back three times. At the main menu you have various choices of whether you want to display Forward Power, Run Time, Reflected Power, etc. You can change the display by turning the knob.

Operation:

1. Verify that the chamber pressure is 5 x 10-6 or lower using IG2.
2. Turn off the Ion Gauge(s) IG1 and IG2.
3. Change the Variable Orifice Switch to Close. This partially restricts the Cryo pumping path so that the pump doesn't overpower the Mass Flow Controllers (MFCs).
4. If you wish to have the substrates rotate during sputtering, turn the Motor Control Switch On, set the desired speed (either Lo or Hi) and the Rotation Direction (Fwd or Rev). This step may be done at any time prior to the sputtering run.
5. Open the gas valve(s) (black toggle near chamber window). A Valve 1 is for argon and Valve 2 is the reactive sputtering gas (usually oxygen). The valve is open when the black handle is perpendicular to the panel. If you are not doing reactive sputtering, leave Valve 2 closed.
6. Start the argon flow by turning On MFC 1. MFC 1 should be set for Flow. The display will read the flow rate in SCCM. If you are doing reactive sputtering, see the separate section on reactive sputtering to set the second gas flow parameters.
7. Verify that the gas(es) are flowing by noting the display on the MKS 250 Pressure Controller (to the left of the MFCs). It is not adequate to use the MFC read out to determine if gas is flowing because the display reads out the Setpoint, not the actual flow. When the gas is actually flowing, the display on the Pressure Controller will closely follow (but not be the same as) the read out for Thermocouple Gauge 2 (TC2).
8. Verify that the sputtering pressure is correct by observing the reading at TC2. If you wish to change the sputtering pressure, this can be done by adjusting the flow at the MFC. You should have one of the superusers do this. Do not attempt to adjust the pressure at the Pressure Controller. Under normal operating conditions, it should not be necessary to change any of the settings on the 250 Pressure Controller.
9. Press RF On/Off on the RF Power Supply to turn on the cathode power.
10. Verify that the plasma is lit thru the chamber window. You should also verify that the Reflected Power is low (a small percentage of Forward Power). Reflected Power can be displayed on the RF Power Supply. It is also displayed on the RF Tuner.
11. At this point, the shutter is closed. You can presputter the target with the shutter closed. You should try to limit the time of presputtering to avoid wasting target material and to avoid buildup of material on the back of the shutter which will eventually need to be cleaned off.
12. Expose the substrate for sputtering by changing the shutter 1 Switch to Open.
13. RF Power will shut off when the Programmed Run Time is finished. Alternatively, the RF Power can be shut off at any time by pressing RF On/Off.

Shut Down after Sputtering

1. Turn off argon (and reactive gas) by changing MFC 1 (& 2) to Off.
2. Close the gas valve(s) next to the chamber window.
3. Change the Variable Orifice Switch to Open to allow the pressure to recover.
4. Close shutter 1 by changing the switch to Closed.
5. Turn Off the Motor Control to stop the Rotating Platen.
6. After allowing a few minutes for the substrate to cool, go to the venting procedure or to the next sputtering operation .

To Do DC Sputtering (Cathode 2):

The DC Power Supply is located at the left center of the control panel. The Power Supply has a black face with a red LED display for the various functions. As with the RF Cathode you must first set the sputtering parameters (Setup) and then do the sputtering run (Operation).

Setup:

1. With the power On, press SetPt under Right Display.
2. Should see Power light up under Right Display. If not continue to press SetPt until Power appears.
3. Use the Level knob to adjust the power. If the knob is difficult to turn, make sure the locking ring at the base of the knob is in the released position.
4. Press SetPt until Seconds appears.
5. Use the Ramp Adjust knob to set the Ramp Time. This time is the delay between the time when the power first comes on and the time when it reaches the Setpoint.
6. Should see Power lit up under Regulation. The power supply controls best when used in the Regulated Power mode, although it is possible to run in Regulated Current or Regulated Voltage as well. Use the two buttons under Regulation to choose the mode.

Operation:

The steps used for DC Sputtering are the same as for RF Sputtering except:

1. Press On under Output on the DC power supply to start Cathode 2.
2. For the DC cathode, you should check to make sure that the plasma is stable and that the arcing light is not coming on. It is okay for the arcing light to come on infrequently when starting with a new target, but if the light comes on frequently with a subsequent drop in power it probably means that the cathode is shorting. The two most likely reasons for this to occur are either: (a) the target/ dark space shield is not installed correctly, or (b) the shield needs to be cleaned. If this occurs, turn the power off and contact one of the superusers.
3. Open Shutter 2 to expose the substrate when using the DC cathode.
4. There is no timer for the DC power supply. You must time your sputtering runs and shut off the DC power supply by pressing Off under Output.

Reactive Sputtering

The CHA system has the capability for sputtering with a second (reactive) gas in addition to argon. The second gas can be controlled as a percentage of the first gas (ratio control) or can be controlled in the same manner as the sputtering gas (flow control). Consult the superuser(s) and/or lab manager for more information before attempting reactive sputtering.

Co-sputtering

The CHA system also has the capability of doing co-sputtering (both cathodes in operation). Again, contact one of the superusers and/or lab manager before attempting this.