ETCH RESISTANT HEATER AND ASSEMBLY THEREOF

Abstract

An etch resistant heater for use in a wafer processing assembly with an excellent ramp rate of at least 20° C. per minute. The heater is coated with a protective overcoating layer allowing the heater to have a radiation efficiency above 70% at elevated heater temperatures of >1500° C., and an etch rate in NF3 at 600° C. of less than 100 A/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are cross-sectional views showing one embodiment of a heater, as it is being formed in various process steps, with a pyrolytic graphite overcoat layer on one surface of the heater.

FIG. 1D-1E are cross sectional views of various embodiments of a susceptor.

FIG. 1F-1H are cross section views of various embodiments of a heater having a coil shape (as formed from a coil-shaped substrate).

FIGS. 2A-2B are cross-sectional views showing a second embodiment of a ceramic heater, as it is being formed in various process steps, with a pyrolytic graphite overcoating layer protecting the entire heater structure.

FIG. 3A is a top view of one embodiment of a ceramic heater, wherein all the top coating layers are removed showing the geometrical pattern of the pyrolytic graphite heating element. FIG. 3B is a cross-section view of another embodiment of a heater assembly, wherein with a substrate holder having upper and lower relatively flat surfaces and a shaft extending substantially transverse to the substrate holder.

FIG. 4 is a cross-sectional view showing a thermal module employing a heater of the prior art, for use in a computational fluid dynamics (CFD) calculation to examine the heater surface temperature as the wafer is heated up to a temperature of 1500° C.

FIG. 5 is a cross-sectional view showing a thermal module employing a heater of FIGS. 1A-1C, for use in a computational fluid dynamics (CFD) calculation to examine the surface temperature of the heater of the invention as the wafer is heated up to a temperature of 1500° C.

FIG. 6 is a graph illustrating the etch rate of various materials in a NF₃ environment at room temperature.

FIG. 7 is a graph comparing the etch rate of one embodiment of the overlayer of the heater with other materials in the prior, including pyrolytic boron nitride and sintered aluminum nitride at 400° C.

FIG. 8 is a photograph (¼ magnification) of a prior art heater with a pyrolytic boron nitride coating after being etched.

FIG. 9A is a diagram of an experimental set-up for the heater ramping tests comparing a heater in the prior art and one embodiment of a heater in the present invention, a PG over-coated PBN heater. FIG. 9B is a close up sectional view of the heater.

FIGS. 10A and 10B are graphs comparing heater temperatures and achieved susceptor temperatures obtained from a heater in the prior art and one embodiment of a heater in the present invention, a PG over-coated PBN heater.

FIG. 11 is a graph comparing the etch rates of the overcoating layer of the heater invention after etching at 400° C., after 1 hour and 5 hours.

FIG. 12 is a graph comparing the etch rates of the overcoating layer of the heater invention after etching at 600° C., after continuous and pulsed etching for 1 hour.

Claims

1. An apparatus for use in a wafer processing chamber, the apparatus comprising: a base substrate comprising one of graphite; refractory metals, transition metals, rare earth metals and alloys thereof; a sintered material including at least one of oxide, nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals; oxide, oxynitride of aluminum; and combinations thereof;wherein the base substrate is coated with an over-coating layer having a thermal conductivity greater than 100 W/m° K.

2. The apparatus of claim 1, wherein the apparatus is a heater, which further comprises: a heating element comprising pyrolytic graphite superimposed on the base substrate;a first layer coating the heating element and the base substrate, the layer comprises at least one of a nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals, and combinations thereof;wherein the first layer coating is coated with the over-coating layer having a thermal conductivity greater than 100 W/m° K.

3. The apparatus of claim 2, wherein the over-coating layer has a planar thermal conductivity of at least 3 times the planar thermal conductivity of the first coating layer.

4. The heater of claim 1, wherein the overcoat layer comprises a material having planar thermal conductivity of at least 4 times the planar thermal conductivity of the first outer coating layer.

5. The heater of claim 2, wherein the first outer coating layer comprises at least one of pyrolytic boron nitride, aluminium nitride (AlN), aluminium oxide, aluminium oxynitride, silicon nitride, or complexes thereof.

6. The apparatus of claim 1, wherein the apparatus is a susceptor, the base substrate comprises graphite, and the over coating layer comprises pyrolytic graphite.

7. The apparatus of claim 1, wherein the overcoat layer comprises a material having a thermal conductivity greater than 200 W/m° K.

8. The heater of claim 2, wherein the overcoat layer comprises a material having a radiation efficiency above 70% at a temperature greater than 1500° C.

9. The heater of claim 2, wherein the overcoat layer comprises a material having a radiation efficiency above 80% at a temperature greater than 1500° C.

10. The apparatus of claim 1, wherein the overcoat layer comprises pyrolytic graphite (“PG”).

11. The apparatus of claim 1, wherein the overcoat layer is deposited by any of ETP, ion plating, ion plasma plating, CVD, PECVD, MOCVD, OMCVD, MOVPE, e-beam deposition, plasma spray, and combinations thereof.

12. The apparatus of claim 1, characterized by having an etch rate in NF3 at 600° C. of less than 100 A/min.

13. The apparatus of claim 10, characterized by an etch rate in NF3 at 600° C. of less than 50 A/min.

14. The apparatus of claim 1, wherein the apparatus is a heater capable of heating up at a ramp rate of at least 20° C. per min.

15. The apparatus of claim 1, wherein the apparatus is a heater capable of heating up at a ramp rate of at least 30° C. per min.

16. The heater apparatus of claim 2, wherein: the base substrate comprises graphite;the heating element superimposed on the base substrate comprises pyrolytic graphite,the first outer coating layer comprises at least one of boron nitride and aluminum nitride;the over coating layer comprises pyrolytic graphite.

17. The apparatus of claim 1, wherein the over coating layer has a thickness between 1 μm-500 μm.

18. The apparatus of claim 15, wherein the over coating layer has a thickness between 5 to 300 μm.

19. The apparatus of claim 16, wherein the over coating layer has a thickness less than 100 μm.

20. A plasma processing chamber for processing at least a semiconductor wafer, the plasma processing chamber comprising: at least a ceramic heater for heating the wafer;gas distribution plate defined over the electrostatic chuck;a pedestal for holding the electrostatic chuck;a source of cleaning gas communicating selectively with the chamber;wherein at least one of the heater, the gas distribution plate, and the pedestal has a surface coated with a over coating layer comprising pyrolytic graphite, and whereinthe source of cleaning gas comprises NF3 and Cl2.

21. The plasma processing chamber of claim 18, wherein the heater is coated with the over coating layer comprising pyrolytic graphite, and wherein the heater comprises: a base substrate comprising one of graphite; refractory metals, transition metals, rare earth metals and alloys thereof; a sintered material including at least one of oxide, nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals; oxide, oxynitride of aluminum; and combinations thereof;a heating element comprising pyrolytic graphite superimposed on the base substrate,a first outer coating comprising comprises at least one of a nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals, and combinations thereof;wherein the pyrolytic graphite over coating layer protects the underlying first coating layer, heating element, and base substrate from the cleaning gas, for the heater to have an etch rate in NF3 at 600° C. of less than 100 A/min.

22. The plasma processing chamber of claim 19, wherein the heater has an etch rate in NF3 at 600° C. of less than 50 A/min.