Very low pressure high power impulse triggered magnetron sputtering
View Patent ↗A method and apparatus are described for very low pressure high powered magnetron sputtering of a coating onto a substrate. By the method of this invention, both substrate and coating target material are placed into an evacuable chamber, and the chamber pumped to vacuum. Thereafter a series of high impulse voltage pulses are applied to the target. Nearly simultaneously with each pulse, in one embodiment, a small cathodic arc source of the same material as the target is pulsed, triggering a plasma plume proximate to the surface of the target to thereby initiate the magnetron sputtering process. In another embodiment the plasma plume is generated using a pulsed laser aimed to strike an ablation target material positioned near the magnetron target surface.
1. A method comprising:
(a) placing a substrate in a chamber housing a target and a cathodic arc plasma source positioned proximate the target;
(b) evacuating the chamber to a vacuum pressure and maintaining the vacuum pressure without admitting an inert gas to the chamber during operations (c), (d), and (e);
(c) applying a target pulse of a negative voltage to the target for a first time period while maintaining a member proximate the target at positive potential relative to the target, the member serving as an anode of a discharge, the target pulse being of sufficient amplitude so as to create a condition supportive of self-sputtering of the target after sputtering has been initiated;
(d) applying a triggering pulse for a second time period to the cathodic arc plasma source to generate a triggering plasma comprising material from the cathodic arc plasma source which blankets the target to initiate sputtering of the target, the first time period and the second time period overlapping for at least a portion of the time periods; and
(e) repeating operations (c) and (d) to deposit material from the target onto the substrate.
2. The method of claim 1 wherein the vacuum pressure is between 10 −6 Torr and 10 −8 Torr.
3. The method of claim 1 wherein the target is selected from the group consisting of silver, copper, nickel, and bismuth.
4. The method of claim 1 wherein the target pulse is in the range of 500V to 1500V.
5. The method of claim 4 wherein the target pulse is of sufficient amplitude so as to result in a power density to the target of at least 100 W cm −2 .
6. The method of claim 4 wherein the target pulse is of sufficient amplitude so as to result in a power density to the target of between 100 W cm −2 to 5,000 W cm −2 .
7. The method of claim 1 wherein the vacuum pressure is at or below 8×10 −4 Torr.
8. The method of claim 1 wherein the target is selected from the group consisting of niobium, aluminum, titanium, tungsten and chromium.
9. The method of claim 1 wherein the first time period is longer than the second time period.
10. The method of claim 9 wherein the target pulse is applied before applying the triggering pulse.
11. The method of claim 9 wherein the target pulse is applied after applying the triggering pulse.
12. The method of claim 1 wherein the substrate is negatively biased with respect to a plasma potential.