Vertically adjustable plasma source
The disclosure describes a plasma source assemblies comprising a differential screw assembly, an RF hot electrode, a top cover, an upper housing and a lower housing. The differential screw assembly is configured to provide force to align the plasma source assembly vertically matching planarity of a susceptor. More particularly, the differential screw assembly increases a distance between the top cover and the upper housing to align the gap with the susceptor. The disclosure also provides a better thermal management by cooling fins. A temperature capacity of the plasma source assemblies is extended by using titanium electrode. The disclosure provides a cladding material covering a portion of a first surface of RF hot electrode, a second surface of RF hot electrode, a bottom surface of RF hot electrode, a portion of a surface of the showerhead and a portion of lower housing surface.
1. A plasma source comprising:
an upper housing having an inner peripheral edge and an outer peripheral edge, a top surface, and a bottom surface;
a lower housing having an inner peripheral edge and an outer peripheral edge, a top surface and a bottom surface, the lower housing acting as a return electrode;
a top cover having an inner peripheral edge, an outer peripheral edge, a top surface, and a bottom surface, the top cover connected to and spaced a distance from the top surface of the upper housing by one or more differential screw assembly, wherein the distance between the top surface of the upper housing and the bottom surface of the top cover is vertically adjustable; and
an RF hot electrode bounded by and spaced from the lower housing defining a gap therebetween, the RF hot electrode having an inner end adjacent to and spaced from the inner peripheral edge of the lower housing, an outer end adjacent to and spaced from the outer peripheral edge of the lower housing, an upper edge spaced from the bottom surface of the upper housing, and a bottom edge.
2. The plasma source of claim 1 , wherein the gap between the lower housing and the RF hot electrode is in a range of about 3 mm to about 15 mm.
3. The plasma source of claim 2 , wherein the RF hot electrode has a thickness in a range of from about 3 mm to about 11 mm.
4. The plasma source of claim 2 , wherein the RF hot electrode has a height in a range of from about 8 mm to about 40 mm.
5. The plasma source of claim 1 , wherein the RF hot electrode has a bottom surface with a non-conductive cladding.
6. The plasma source of claim 5 , wherein the non-conductive cladding comprises quartz.
7. The plasma source of claim 1 , wherein a cladding layer covers a portion of a first side of the RF hot electrode and a portion of a second side of the RF hot electrode that forms the gap.
8. The plasma source of claim 7 , wherein the cladding layer has a length in a range of about 10 mm to about 25 mm.
9. The plasma source of claim 7 , wherein the cladding layer has a thickness in a range of about 0.25 mm to about 2.5 mm.
10. The plasma source of claim 7 , wherein the cladding layer covers a portion of a surface of non-conductive showerhead and a portion of a surface of the lower housing that forms the gap to create inverted u-shaped channels.
11. The plasma source of claim 7 , wherein a plasma is ignited in inverted u-shaped channels on either side of the RF hot electrode.
12. The plasma source of claim 1 , further comprising one or more of: a gas inlet connected to the top surface of the upper housing; a plurality of apertures in the top surface of the lower housing to allow a flow of gas to pass from a plenum gap through a non-conductive showerhead to the gap between the RF hot electrode and the lower housing; or a cladding layer covering a bottom portion of an inside surface of the lower housing, a portion of a bottom surface of the non-conductive showerhead and the lower housing forming an inverted u-shaped channel on either side of the RF hot electrode.
13. The plasma source of claim 12 , comprising the plurality of apertures in the top surface of the lower housing, wherein the non-conductive showerhead separates the RF hot electrode and the top surface of the lower housing comprising a conductive material, and the non-conductive showerhead has a plurality of apertures extending from a top surface of the showerhead through a bottom surface of the showerhead to allow the flow of gas to pass through the non-conductive showerhead.
14. The plasma source of claim 12 , wherein the gas inlet is in fluid communication through the upper housing with a plenum gap between the bottom surface of the upper housing and the top surface of the lower housing.
15. The plasma source of claim 1 , wherein the differential screw assembly comprises an adjustment screw extending through the top cover into the upper housing.
16. The plasma source of claim 1 , wherein the upper housing has an adjustment recess in the top surface with a compression element, the compression element configured to provide force to the bottom surface of the top cover to separate the top cover from the upper housing and the top cover is actively cooled.
17. The plasma source of claim 1 , wherein the RF hot electrode extends from an RF feed connector through the upper housing, the RF feed connector having a power connector end with a hard stop to prevent force applied by a power line connected to the power connector end from transferring to the RF hot electrode and the RF feed connector passes through the top cover into a recess formed in the top surface of the upper housing.
18. The plasma source of claim 17 , wherein the RF hot electrode passes through an insulating sleeve positioned within the upper housing, the insulating sleeve preventing direct electrical communication between the RF hot electrode and the upper housing.
19. The plasma source of claim 1 , wherein the plasma source further comprises
a compression element in the top surface of the upper housing, the compression element configured to provide force to the bottom surface of the top cover to separate the top cover from the upper housing;
one or more cooling wings in the top cover;
one or more chamber cooling plates extending from the top surface of the upper housing into a complementary recess formed in the bottom surface of the top cover; and
one or more cooling fins between the upper housing and top cover and cooling wings that create contact between the top cover and chamber cooling plates.
20. The plasma source of claim 12 , comprising the plurality of apertures in the top surface of the lower housing and the cladding layer, wherein the cladding layer includes a plurality of apertures to allow a flow of gas from the non-conductive showerhead to pass into the inverted u-shaped channel on either side of the RF hot electrode.