Biasable flux optimizer / collimator for PVD sputter chamber
In some implementations described herein, a collimator that is biasable is provided. The ability to bias the collimator allows control of the electric field through which the sputter species pass. In some implementations of the present disclosure a collimator that has a high effective aspect ratio while maintaining a low aspect ratio along the periphery of the collimator of the hexagonal array of the collimator is provided. In some implementations, a collimator with a steep entry edge in the hexagonal array is provided. It has been found that use of a steep entry edge in the collimator reduces deposition overhang and clogging of the cells of the hexagonal array. These various features lead to improve film uniformity and extend the life of the collimator and process kit.
1. A collimator assembly, comprising:
a collimator portion, comprising:
a honeycomb structure having walls defining and separating hexagonal apertures, wherein the hexagonal apertures include:
a first plurality of hexagonal apertures in a central region having a first aspect ratio;
a second plurality of hexagonal apertures in a peripheral region having a second aspect ratio less than the first aspect ratio; and
a third plurality of hexagonal apertures in a transitional region disposed between the central region and the peripheral region,
wherein walls defining the third plurality of apertures of the transitional region are cut along an angle to form a conical shape surrounding the central region,
wherein the conical shape is defined by a circular edge formed by the walls of the transitional region, and
wherein an upper portion of the walls include an entrance angle portion; and
a shield portion coupled with the collimator, the shield portion comprising:
a top ring;
a support ledge below the top ring, the support ledge extending radially outward; and
a cylindrical band extending downward from the support ledge to an elevation below the honeycomb structure.
2. The collimator assembly of claim 1 , wherein the cylindrical band comprises:
a first substantially vertical portion; and
a radially inward sloped portion extending downward from the first substantially vertical portion.
3. The collimator assembly of claim 2 , further comprising:
a second substantially vertical portion extending downward from the radially inward sloped portion.
4. The collimator assembly of claim 2 , wherein the radially inward sloped portion extends across a portion of the second plurality of apertures in the peripheral region.
5. The collimator assembly of claim 1 , wherein the first plurality of apertures, the second plurality of apertures, and the third plurality of apertures are textured.
6. The collimator assembly of claim 1 , wherein the entrance angle portion has a predetermined angle of from about 2 degrees to about 16 degrees.
7. The collimator assembly of claim 6 , wherein the entrance angle portion has a predetermined angle of about 2.5 degrees and has a length of about 2.54 centimeters.
8. The collimator assembly of claim 1 , wherein the first aspect ratio of the first plurality of apertures is from about 2.5:1 to about 3:1.
9. The collimator assembly of claim 8 , wherein the second aspect ratio is from about 1:1 to about 2:1.
10. The collimator assembly of claim 2 , wherein the radially inwardly sloped portion has an angle from about 40 to about 50 degrees relative to the first substantially vertical portion.
11. The collimator assembly of claim 3 , wherein the radially inwardly sloped portion and the second substantially vertical portion form a labyrinth gap with a lower shield.
12. The collimator assembly of claim 1 , wherein the collimator is coupled with a DC power source.
13. A substrate-processing chamber, comprising:
a chamber body defining an inner volume;
a sputtering target disposed in an upper portion of the inner volume;
a substrate support disposed below the sputtering target;
a collimator assembly for encircling the sputtering target, comprising:
a collimator, comprising:
a honeycomb structure having walls defining and separating hexagonal apertures, wherein the hexagonal apertures include:
a first plurality of hexagonal apertures in a central region having a first aspect ratio;
a second plurality of hexagonal apertures in a peripheral region having a second aspect ratio less than the first aspect ratio; and
a third plurality of hexagonal apertures in a transitional region disposed between the central region and the peripheral region,
wherein walls defining the third plurality of apertures of the transitional region are cut along an angle to form a conical shape surrounding the central region,
wherein the conical shape is defined by a circular edge formed by the walls of the transitional region, and
wherein an upper portion of the walls include an entrance angle portion; and
a shield portion coupled with the collimator, comprising:
a top ring;
a support ledge below the top ring, the support ledge extending radially outward; and
a cylindrical band extending downward from the support ledge to an elevation below the honeycomb structure.
14. The substrate-processing chamber of claim 13 , wherein the cylindrical band comprises:
a first substantially vertical portion; and
a radially inward sloped portion extending downward from the first substantially vertical portion.
15. The substrate-processing chamber of claim 14 , further comprising:
a second substantially vertical portion extending downward from the radially inward sloped portion.