Wafer contact surface protrusion profile with improved particle performance
An electrostatic chuck with a generally non-arcuate top surface shaped protrusions that has edge surfaces similar to a portion of a ellipse. The structure of the protrusions leads to the reduction of particulate material generated by interaction between the supported substrate and chuck. Reduced levels of scratching, abrasion, wear and particulate generation are achieved by improved smoothing and flattening of the protrusion surface.
1. An electrostatic chuck comprising:
an electrode in a ceramic base; and
a surface layer of the electrostatic chuck activated by a voltage in the electrode to form an electric charge that electrostatically clamps a substrate to the electrostatic chuck; wherein
the surface layer of the electrostatic chuck comprises a plurality of protrusions, the protrusions comprising a composition whose morphology is columnar or granular, and whose microstructure is crystalline or amorphous, the protrusions extending to an average height H above the surface layer surrounding the protrusions, the protrusions supporting the substrate upon the protrusions during electrostatic clamping of the substrate;
a cross section of the protrusions has a structure characterized by a non-arcuate plateau shaped top surface, an edge surface, and a side surface; wherein the non-arcuate plateau shaped top surface of the protrusions has a length L in microns that is characterized by a flatness parameter Δ in microns, the top surface having a surface roughness R a of 1 micron or less and a value of (Δ*100)/L that is less than ±0.01;
the edge surface of the protrusion is between the top surface and the side surface of the protrusion and has an edge surface profile that lies on or within a quadrant or portion thereof of an ellipse, the minor axis Y of the ellipse intersecting a portion of the top surface of the protrusion wherein the value of (Δ*100)/L is equal to or greater than ±0.01, and the minor axis apex of the ellipse lying along the top surface of the protrusion, the value of Y/2 is 0.5 microns or less;
the major axis X of the ellipse is substantially parallel to the top surface or surface layer of the protrusion and the value of X/2 is between 25 microns and 250 microns; and
the side surface of the protrusions connects the edge surface and the surface layer of the electrostatic chuck.
2. The electrostatic chuck of claim 1 , wherein the protrusions comprise a material that is softer than silicon.
3. The electrostatic chuck of claim 1 , where the protrusion side surface makes an angle with the surface layer, wherein the angle is between 80 degrees and 175 degrees.
4. The electrostatic chuck of claim 1 further comprising a gas seal ring or lift pin seal that extends to an average height H above the surface layer; wherein
a cross section of the gas seal ring or lift pin seal has a structure characterized by a non-arcuate plateau shaped top surface, an edge surface, and a side surface; wherein the non-arcuate plateau shaped top surface of the gas seal ring or lift pin seal has a length L in microns that is characterized by a flatness parameter Δ in microns, the top surface having a surface roughness R a of 1 micron or less and a value of (Δ*100)/L that is less than ±0.01;
the edge surface of the gas seal ring or lift pin seal is between the top surface and the side surface of the gas seal ring or lift pin seal and has an edge surface profile that lies on or within a quadrant or portion thereof of an ellipse, the minor axis Y of the ellipse intersecting a portion of the top surface of the gas seal ring or lift pin seal wherein the value of (Δ*100)/L is equal to or greater than ±0.01, and the minor axis apex of the ellipse lying along the top surface of the gas seal ring or lift pin seal, the value of Y/2 is 0.5 microns or less;
the major axis X of the ellipse is substantially parallel to the top surface of the gas seal ring or lift pin seal and the value of X/2 is between 25 microns and 250 microns; and
the side surface of the gas seal ring or lift pin seal connects the edge surface and the surface layer.
5. The electrostatic chuck of claim 4 , wherein Δ value of 0.25 microns or less.
6. The electrostatic chuck of claim 1 , wherein Δ has a value of 0.25 microns or less.
7. The electrostatic chuck of claim 1 , wherein the protrusions comprise yttrium.
8. The electrostatic chuck of claim 1 , wherein the protrusions comprise aluminum.
9. The electrostatic chuck of claim 1 , wherein the protrusions comprise aluminum and oxygen.
10. The electrostatic chuck of claim 9 , wherein the protrusions comprise aluminum oxynitride.
11. The electrostatic chuck of claim 1 , wherein the protrusions comprise yttria.
12. The electrostatic chuck of claim 1 , wherein the protrusions comprise alumina.
13. The electrostatic chuck of claim 1 , wherein the protrusions comprise yttrium aluminum garnet.
14. The electrostatic chuck of claim 1 , wherein the protrusions a height in the range of 5 microns to 20 microns.
15. The electrostatic chuck of claim 1 , wherein Δ has a value of between 0.25 microns and 0.05 microns.
16. The electrostatic chuck of claim 1 , wherein the protrusions have a center to center distance of between 1 micron and 20 microns.
17. The electrostatic chuck of claim 1 , wherein the protrusions comprise a coating overlying a ceramic.
18. The electrostatic chuck of claim 1 , wherein the protrusions comprise a composition having a columnar morphology as determined by scanning electron microscopy.
19. The electrostatic chuck of claim 1 , wherein the protrusions comprise a composition having a crystalline morphology as measured by x-ray diffraction.
20. A wafer contact surface comprising: a plurality of protrusions, the protrusions comprising a composition whose morphology is columnar or granular, and whose microstructure is crystalline or amorphous, the protrusions extending to an average height H above the surface layer surrounding the protrusions, the protrusions supporting a wafer upon the protrusions during clamping of the wafer;
a cross section of the protrusions having a structure characterized by a non-arcuate plateau shaped top surface, an edge surface, and a side surface; wherein the non-arcuate plateau shaped top surface of the protrusions has a length L in microns that is characterized by a flatness parameter Δ in microns, the top surface having a surface roughness R a of 1 micron or less and a value of (Δ*100)/L that is less than ±0.01; wherein
the edge surface of the protrusion is between the top surface and the side surface of the protrusion has an edge surface profile that lies on or within a quadrant or portion thereof of an ellipse, the minor axis Y of the ellipse intersecting an edge of the flat surface of the protrusion wherein the value of (Δ*100)/L is equal to or greater than ±0.01, and the minor axis apex of the ellipse lying along the top surface of the protrusion, the value of Y/2 is 0.5 microns or less;
the major axis X of the ellipse is substantially parallel to the top surface of the protrusion and the value of X/2 is between 25 microns and 250 microns; and
the side surface of the protrusions connects the edge surface and a surface layer of the wafer contact surface.