High density, low stress amorphous carbon film, and process and equipment for its deposition
A deposited amorphous carbon film includes at least 95% carbon. A percentage of sp3 carbon-carbon bonds present in the amorphous carbon film exceeds 30%, and a hydrogen content of the amorphous carbon film is less than 5%. A process of depositing amorphous carbon on a workpiece includes positioning the workpiece within a process chamber and positioning a magnetron assembly adjacent to the process chamber. The magnetron assembly projects a magnetic field into the process chamber. The method further includes providing a carbon target such that the magnetic field extends through the carbon target toward the workpiece. The method further includes providing a source gas to the process chamber, and providing pulses of DC power to a plasma formed from the source gas within the process chamber. The pulses of DC power are supplied in pulses of 40 microseconds or less, that repeat at a frequency of at least 4 kHz.
1. A high power impulse magnetron sputtering system, comprising:
a process chamber;
a pedestal configured to position a workpiece within the process chamber;
a magnetron assembly including:
a backing plate,
a plurality of first magnets, wherein north poles of each of the first magnets couple with the backing plate,
a south pole piece coupled with south poles of each of the first magnets,
a plurality of second magnets, wherein south poles of each of the second magnets couple with the backing plate, and
a north pole piece coupled with north poles of each of the second magnets, wherein the north pole piece and the south pole piece are spatially separated so as to project a magnetic field across one or more gaps between the north pole piece and the south pole piece;
a magnetron assembly surround that is configured to envelop, and to circulate a heat exchange fluid around, the magnetron assembly;
a carbon target disposed on a surface of the magnetron assembly surround such that the magnetic field projects through the carbon target;
a gas supply system for providing a source gas to the process chamber; and
a power supply that provides pulses of DC power to a plasma formed from the source gas within the process chamber, wherein:
the pulses of DC power are supplied in pulses of 40 microseconds or less,
the pulses are repeated at a frequency of at least 4 kHz, and
the power supply is configured to operate in cycles, each cycle comprising:
an on-period during which the pulses repeat at the frequency, the on-period being 30 seconds to 2 minutes in duration; and
an off-period during which the pulses cease, the off-period being of 5 seconds to one minute in duration.
2. The high power impulse magnetron sputtering system of claim 1 , wherein the source gas comprises krypton.
3. The high power impulse magnetron sputtering system of claim 1 , wherein the pedestal is configured to control a temperature of the workpiece within a range of −20 C to 200 C.
4. The high power impulse magnetron sputtering system of claim 3 , wherein the pedestal is configured to control the temperature of the workpiece within a range of −20 C to 50 C.
5. The high power impulse magnetron sputtering system of claim 1 , wherein the frequency is at least 30 kHz.
6. The high power impulse magnetron sputtering system of claim 1 , wherein the magnetic field is configured to project through the carbon target so as to urge the plasma into proximity with the carbon target, and the north and south pole pieces are configured to form the magnetic field into a spiral pattern.
7. The high power impulse magnetron sputtering system of claim 6 , wherein the magnetron assembly is mounted on a motor and is configured to rotate so that the spiral pattern rotates over the carbon target while the pulses of DC power are supplied.
8. The high power impulse magnetron sputtering system of claim 7 , further comprising a system controller, that is configured to control the motor so that the spiral pattern rotates over the carbon target at least three full revolutions during each of the on-period cycles.
9. The high power impulse magnetron sputtering system of claim 8 , wherein the system controller is configured to control the motor so that the spiral pattern rotates at a rate between 40 and 150 revolutions per minute.