MULTILAYER RARE-EARTH OXIDE COATINGS AND METHODS OF MAKING

1 . A method of forming a multilayer coating on a substrate, the method comprising:

forming a plasma-spray coated layer on the substrate, wherein the plasma-sprayed coated layer comprises a rare-earth oxide, a rare-earth fluoride or a rare-earth silicate;

irradiating an exposed surface of the plasma-spray coated layer to form a treated portion of the layer, wherein the treated portion of the layer has a mean spacing of local peaks (S value) between about 100 and 300 microns; and

forming a second layer on the treated portion of the plasma-spray coated layer, wherein the second layer comprises a dielectric material.

2 . The method of claim 1 , wherein the irradiating of the exposed surface of the plasma-spray coat layer comprises exposing the surface to a beam of laser light.

3 . The method of claim 2 , wherein the laser light comprises infrared laser light having a power intensity of about 30 watts to about 80 watts.

4 . The method of claim 3 , wherein the laser light has a wavelength of 10.6 μm.

5 . The method of claim 2 , wherein the laser light irradiating the exposed surface has a raster rate of about 2 cm/second to about 20 cm/second.

6 . The method of claim 1 , wherein the initially deposited plasma-spray coated layer has an S value between about 45 microns and 75 microns.

7 . The method of claim 1 , wherein the dielectric material of the second layer comprises silicon oxide.

8 . The method of claim 1 , wherein the forming of the second layer comprises a chemical vapor deposition of the dielectric material on the treated portion of the plasma-spray coated layer.

9 . The method of claim 1 , wherein the rare-earth oxide comprises yttrium oxide (Y 2 O 3 ).

10 . The method of claim 1 , wherein the plasma-spray coated layer has a thickness of about 50 microns to about 200 microns, and the treated portion of the layer has a thickness of about 0.5 microns to about 20 microns.

11 . The method of claim 1 , wherein the method comprises roughening the substrate prior to the forming of the plasma-spray coated layer on the substrate.

12 . The method of claim 1 , further comprising:

performing a semiconductor-fabrication process, thereby exposing the second layer to a fabrication chemical;

removing the second layer; and

forming a new second layer on the treated portion of the plasma-spray coated layer.

13 . A coated surface comprising:

a plasma-spray coated layer on a substrate, wherein the plasma-spray coated layer comprises a rare-earth oxide, a rare-earth fluoride or a rare-earth silicate;

a treated portion of the plasma-spray coated layer facing opposite a contact surface between the plasma-spray coated layer and the substrate, wherein the treated portion of the layer is formed by irradiating the plasma-spray coated layer, and wherein the treated portion of the plasma-spray coated layer has a mean spacing of local peaks (S value) between about 100 and 200 microns; and

a second layer formed on the treated portion of the plasma-spray coated layer, wherein the second layer comprises a dielectric material.

14 . The coated surface of claim 13 , wherein an untreated portion of the plasma-spray coated layer has an S value between about 45 and 75 microns.

15 . The coated surface of claim 13 , wherein the substrate comprises a component of a semiconductor fabrication apparatus.

16 . The coated surface of claim 15 , wherein the component of the semiconductor fabrication apparatus comprises an interior wall of a plasma-using semiconductor fabrication chamber.

17 . The coated surface of claim 13 , wherein the rare-earth oxide comprises yttrium oxide (Y 2 O 3 ).

18 . The coated surface of claim 13 , wherein the plasma-spray coated layer that has not been treated has an average porosity that is statistically greater than the an average porosity of the treated portion of the plasma-spray coated layer.

19 . The coated surface of claim 13 , wherein the dielectric material of the second layer comprises silicon oxide.