Ring cathode for use in a magnetron sputtering device
The present invention relates to a magnetron sputtering device including a large ring cathode having a defined inner radius. The position of the ring cathode is offset in relation to a center point of a planetary drive system. An anode or reactive gas source may be located within the inner radius of the ring cathode. Lower defect rates are obtained through the lower power density at the cathode which suppresses arcing, while runoff is minimized by the cathode to planet geometry without the use of a mask.
1. A magnetron sputtering device including:
a planetary drive system having a central rotation axis C for primary rotation, and supporting a plurality of planets, each planet having a secondary axis of rotation at a planet center point C s , and each planet representing a coating area described by r w the planet radius, the planetary drive system having a carrier radius r C from the central rotation axis C to a planet center point C s ;
a ring shaped cathode including a ring shaped target comprising material for forming a coating, the cathode having a center point Cc, an outer radius r 2 greater than the planet radius (r 2 >r W ), an inner radius r 1 greater than one quarter of the outer radius (r 2 >r 1 >¼*r 2 );
wherein the cathode center point Cc is disposed an offset distance r T between ⅔ and 4/3 of the carrier radius r C from the central rotation axis C (⅔*r C <r T < 4/3*r C ), and the offset distance r T is greater than one half the outer radius of the cathode (r T >½*r 2 );
and wherein a throw distance h vertically from a target surface to a planet surface is between one third of the outer radius r 2 of the cathode and one times the outer radius of the cathode (⅓*r 2 <h<r 2 );
a chamber for housing the cathode and the planetary drive system adapted to be evacuated in operation; and
a gas delivery system for providing a flow of sputter gas into the chamber.
2. The magnetron sputtering device as defined in claim 1 for providing a sputter coating to a substrate without the use of a mask.
3. The magnetron sputtering device as defined in claim 2 , further including an anode for providing a voltage difference to the cathode, such that the anode is a return path for electrons, the anode comprising an interior conductive surface of a vessel having an insulated outer surface electrically isolated from the chamber walls, the vessel having an opening in communication with a chamber interior, the opening being smaller than a circumference of the vessel to shield the interior conductive surface from most sputtered material.
4. The magnetron sputtering device as defined in claim 3 , wherein a source for sputtering gas is coupled into the vessel for providing sputtering gas through the opening into the chamber, and the opening is dimensioned to permit a flow of gas to increase the pressure locally within the anode vessel above the pressure of the evacuated chamber.
5. The magnetron sputtering device as defined in claim 2 , further including an activated source for a reactive gas.
6. The magnetron sputtering device as defined in claim 4 , further including an activated source for a reactive gas.
7. The magnetron sputtering device as defined in claim 4 , wherein the anode is located such that the opening of the vessel in communication with the chamber interior is at the center of the ring shaped cathode.
8. The magnetron sputtering device as defined in claim 5 , wherein the activated source for a reactive gas is located at the center of the ring shaped cathode.
9. The magnetron sputtering device as defined in claim 6 , wherein the anode is located such that the opening of the vessel in communication with the chamber interior is at the center of the ring shaped cathode.
10. The magnetron sputtering device as defined in claim 6 , wherein the activated source for a reactive gas is located at the center of the ring shaped cathode.
11. The magnetron sputtering device as defined in claim 4 , wherein the anode further includes a source for a reactive gas coupled into the vessel for providing an activated reactive gas together with the sputtering gas through the opening into the chamber.
12. The magnetron sputtering device as defined in claim 11 , wherein the opening into the chamber of the vessel comprising the anode is located at the center of the ring shaped cathode.
13. The magnetron sputtering device as defined in claim 12 , further including an auxiliary activated reactive source located a distance from the cathode.
14. The magnetron sputtering device as defined in claim 1 wherein the inner radius r 1 is greater than ½ the outer radius r 2 , such that r 2 >r 1 >½*r 2 .
15. The magnetron sputtering device as defined in claim 1 wherein the inner radius r 1 is greater than 0.70 of the outer radius r 2 , such that r 2 >r 1 >0.70*r 2 .
16. The magnetron sputtering device as defined in claim 1 wherein 0.95*r 2 >r 1 >0.6*r 2 .
17. The magnetron sputtering device as defined in claim 1 , wherein the cathode diameter r 2 is equal to or larger than 1.11 times the planet radius (r 2 >1.11*r W ).
18. The magnetron sputtering device as defined in claim 1 wherein the cathode includes inner and outer concentric rings of permanent magnetic material on a side opposite to the target material of the cathode, the inner and outer concentric rings having opposite polarity with their axes perpendicular to a surface of the target for providing a magnetic field close to a surface of the target.
19. A magnetron sputtering device as defined in claim 1 further including within the chamber one or more alternate ring shaped cathode including a ring shaped target comprising material for forming a coating, wherein the offset distance r T is greater than one times the outer radius r 2 (r T >1*r 2 ).
20. A magnetron sputtering device as defined in claim 1 further including means for adjusting the throw distance between a target surface plane and the object plane.
21. A magnetron sputtering device as defined in claim 1 wherein the carrier radius r C is equal to the offset distance r T (r T =r C ).