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Planar
Magnetron Sputtering Sources
Q. Why won't the plasma ignite?
A. Verify the following:
 | All power supply/system interlocks (water/pressure/flow)
are satisfied |
| Argon gas pressure at target surface is sufficient |
| Power supply is properly connected to the cathode and
chamber |
| Chamber pressure is not too high |
| Water leaks are not causing shorting (verify with an ohm
meter) |
| No shorts between cathode and the ground shield (anode)
caused by whisker growth, flaking or debris (verify with an ohm meter) |
| Insulator surfaces (not outside surfaces of screw
insulators) are not coated or conductive (verify with an ohm meter) |
| Magnet module has not been overheated or weakened (verify
with a gaussmeter against the magnetic field profile shipped with sputtering
source) |
| Excessively thick magnetic targets are not being used |
| Target material is electrically conductive when using a DC
power supply |
| When using RF power - verify that the forward and reflected
power is being displayed and that the reflected power is close to zero. |
Q. What are the symptoms of target
overheating?
A. Dramatic, immediate changes in voltage and/or current are
indications of target overheating. Check for:
| Inadequate water flow |
| Inlet water temperature not per specification |
| Poor target bonding or target clamping |
| Higher than permissible power density per duty cycle |
| Magnet module strength degradation |
Q. Weak Plasma Discharge - Low Deposition
Rates
A. Verify:
| Check for electrical leakage across insulators using
an ohm meter |
| Power is being transmitted through the cooling water lines
- check for proper resistivity using an ohm meter with the water flowing
through the water lines |
| Weak magnet module - verify against supplied profile.
Are the magnets being sufficiently cooled? |
| Poor or no ground connection |
| Insulating film build-up on target surface (DC or pulsed DC
power supply). Severely contaminated targets can take hours or even
days to clean. Severe arcing usually is symptomatic when attempting to
raise the target voltage. |
| Is the pressure at the target surface adequate for
efficient magnetron sputtering? |
Q. Plasma extinguishes or is intermitant
A. Check for:
| Insufficient pressure - check mass flow controllers,
throttle valve and gas supply |
| Whisker growth or debris causing shorting between the
cathode and ground shield (anode) |
| "Disappearing Anode." This occurs when all
available ground return paths have been coated with an insulating
film. All chamber surfaces at ground potential and the sputter
source anode surfaces must be removed and cleaned. The use of a
Spindrift anode layer ion source will eliminate this problem during
ion-assisted magnetron sputtering, allowing continuous, reliable, stable
long-term operation because the anode is contained within the ion source
housing assembly and shielded from significant insulating film growth. |
Q. Milky Films
A. Can be caused by:
| Air leak in system |
| Water leak in system |
| Leak in argon or reactive gas lines |
Q. Cannot run DC
power supply at rated power levels
A. This is a particular problem when newer model pulsed DC
power supplies with low upper voltage limits are
used at low pressures (less than 1
mTorr) in combination with sputtering sources having relatively low target
surface areas (higher impedance
compared to larger, lower impedance targets). Ensure that the power supply
purchased is a "high Z"
(widest voltage range with highest possible output voltage) version to prevent
power
limits at low pressures.
Increasing the chamber process pressure will lower the overall impedance,
allowing higher power levels. In
some instances, it may be useful to
double the effective surface area by driving two sputtering sources of the
same size with a single power supply
(decreases the impedance at the same operating pressure). Both
sputtering sources must be in the
same process chamber and exposed to the same process conditions.
Q. Galvanic corrosion of parts exposed to
cooling water
A. Check for:
| Low water resistivity |
| Additives in proprietary solutions used in closed-loop
water recirculation or house water are inappropriate |
| De-ionized water is being used - immediately eliminate it's
use |
| Materials other than copper, brass, stainless steel, PTFE
and appropriate plastics are contained in closed-loop or house water system
- immediately eliminate their use. |
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