Electrostatic chuck

• US 9,543,187 B2
• Filed: 05/15/2009
• Issued: 01/10/2017
• Est. Priority Date: 05/19/2008
• Status: Active Grant

• Current Assignee: Entegris Incorporated
• Original Assignee: Entegris Incorporated
• Inventors: Cooke, Richard A.
• Primary Examiner(s): HOANG, ANN THI
• Application Number:
  US12/454,336
• Publication Number:
  US 20090284894A1
• Time in Patent Office: 2,797 Days
• Field of Search: 361/234
• US Class Current: 1/1
• CPC Class Codes: H01L 21/6831 using electrostatic chucks
• CPC Class Codes: H01L 21/6833 Details of electrostatic chucks
• CPC Class Codes: H01L 21/6875 characterised by a plurality of individual support members, e.g. support posts or protrusions
• CPC Class Codes: H02N 13/00 Clutches or holding devices using electrostatic attraction, e.g. using Johnson-Rahbek effect

Abstract

In accordance with an embodiment of the invention, there is provided an electrostatic chuck comprising an electrode, and a surface layer activated by a voltage in the electrode to form an electric charge to electrostatically clamp a substrate to the electrostatic chuck. The surface layer includes a plurality of protrusions extending to a height above portions of the surface layer surrounding the protrusions to support the substrate upon the protrusions during electrostatic clamping of the substrate. The protrusions are substantially equally spaced across the surface layer as measured by a center to center distance between pairs of neighboring protrusions.

Claims

1. An electrostatic chuck comprising:

an electrode; and

a surface layer activated by a voltage in the electrode to form an electric charge to electrostatically clamp a substrate to the electrostatic chuck, the surface layer including;

(i) a dielectric comprising a resistivity greater than about 10¹² ohm-cm such that the electrostatic chuck is a Coulombic chuck; and

(ii) a charge control surface layer coating overlying the dielectric and comprising a thickness in the range of from about 0.1 microns to about 10 microns and a surface resistivity in the range of from about 1×

10⁸ ohms/square to about 1×

10¹¹ ohms/square, the charge control surface layer coating further comprising a plurality of protrusions extending to a height above portions of the surface layer surrounding the protrusions to support the substrate upon the protrusions during electrostatic clamping of the substrate, the protrusions being substantially equally spaced across the surface layer as measured by a center to center distance between pairs of neighboring protrusions, the protrusions comprising a low stress material having an internal compressive film stress less than about 450 MPa and comprising an overcoating of diamond like carbon;

the charge control surface layer comprising a surface coating layer comprising portions of the surface layer surrounding the protrusions, above which the protrusions extend; and

wherein the protrusions include modified edge geometry such that a ratio of a characteristic rounding height of a protrusion to a characteristic rounding length is equal to a given ratio, wherein the given ratio is between about 0.00611 and about 0.002444.

2. An electrostatic chuck according to claim 1, wherein the protrusions are arranged in a trigonal pattern.

3. An electrostatic chuck according to claim 2, wherein the protrusions have a diameter of from about 0.75 millimeters to about 1 millimeter, and wherein the center to center distance between pairs of neighboring protrusions is less than about 8 millimeters.

4. An electrostatic chuck according to claim 1, wherein at least one of the height and a contact area and roughness of the protrusions are such that at least one of the temperature and the temperature distribution of the substrate, when the substrate is heated during the electrostatic clamping, is substantially controlled by gas heat conduction of a gas in a space between the substrate, the protrusions, and the portions of the surface layer surrounding the protrusions.

5. An electrostatic chuck according to claim 1, wherein greater than a proportion of a top area of each of the protrusions contacts the substrate during the electrostatic clamping, the proportion of the top area being selected from the group consisting of about 25%, about 50%, and about 75%.

6. An electrostatic chuck according to claim 1, wherein less than a number of particle adders are deposited on a back side of the substrate as a result of a use of the electrostatic chuck that includes at least one of:

the electrostatic clamping of the substrate, de-clamping the substrate from the electrostatic clamping, and performing the electrostatic clamping during a manufacturing process performed on the substrate;

the number of particle adders being selected from the group consisting of;

about 5000 particle adders;

about 3000 particle adders;

about 2500 particle adders; and

about 1500 particle adders.

7. An electrostatic chuck according to claim 1, wherein the low stress material comprises at least one of an amorphous dielectric material and a polycrystalline dielectric material.

8. An electrostatic chuck according to claim 1, wherein the protrusions comprise a dielectric material having a resistivity greater than about 10¹² ohm-cm.

9. An electrostatic chuck according to claim 1, wherein the protrusions comprise a dielectric material including at least one of:

silicon, an alloy of silicon with at least one other element, silicon carbide and non-stoichiometric silicon carbide.

10. An electrostatic chuck according to claim 1, wherein the protrusions comprise a dielectric material including at least one of alumina and aluminum nitride.

11. An electrostatic chuck according to claim 1, wherein the protrusions comprise a compliant dielectric material.

12. An electrostatic chuck according to claim 1, wherein a contact area of the protrusions with the substrate comprises from about 1% to about 10% of a total area of the electrostatic chuck.

13. An electrostatic chuck according to claim 1, wherein the protrusions have a diameter of from about 0.75 millimeters to about 1 millimeter.

14. An electrostatic chuck according to claim 1, wherein the center to center distance between pairs of neighboring protrusions is less than about 8 millimeters.

15. An electrostatic chuck according to claim 1, wherein the center to center distance between pairs of neighboring protrusions is less than a distance, wherein the distance is selected from the group consisting of:

about 6 millimeters, about 4 millimeters, and about 2 millimeters.

16. An electrostatic chuck according to claim 1, wherein the protrusions comprise at least one partial protrusion, the partial protrusion comprising at least part of a surface structure of the electrostatic chuck.

17. An electrostatic chuck according to claim 16, wherein the surface structure is selected from at least one of a gas channel, a lift pin and a ground pin.

18. An electrostatic chuck according to claim 1, wherein the height of the protrusions is substantially equal to the mean free path of a gas located during the electrostatic clamping in a space between the substrate, the protrusions, and the portions of the surface layer surrounding the protrusions.

19. An electrostatic chuck according to claim 1, wherein the protrusions include a top surface having a surface roughness metric reduced, by virtue of at least some machine polishing, by between about 25% and about 75% by comparison with similar protrusions polished only by hand.

20. An electrostatic chuck according to claim 19, wherein the surface roughness metric is reduced by about 50%.

21. An electrostatic chuck according to claim 20, wherein less than about 2000 particle adders of particle size range of 0.16 μ

m or greater are deposited on the back side of the substrate as a result of the use of the electrostatic chuck.

22. An electrostatic chuck according to claim 19, wherein less than about 5000 particle adders of particle size range of 0.16 μ

m or greater are deposited on the back side of the substrate as a result of the use of the electrostatic chuck.

23. An electrostatic chuck according to claim 19, wherein less than about 2000 particle adders of particle size range of 0.16 μ

m or greater are deposited on the back side of the substrate as a result of the use of the electrostatic chuck.

24. An electrostatic chuck according to claim 1, wherein the protrusions include modified edge geometry produced by at least some machine polishing, such that a characteristic rounding height of a protrusion is shorter by comparison with a corresponding height of a similar protrusion polished only by hand and such that a characteristic rounding length is longer by comparison with a corresponding length of a similar protrusion polished only by hand.

25. An electrostatic chuck according to claim 24, wherein the ratio of the characteristic rounding height to the characteristic rounding length is reduced by a factor by comparison with the similar protrusion polished only by hand, wherein the factor is selected from the group consisting of:

between about 2 and about 5; and

between about 3 and about 4.

26. An electrostatic chuck according to claim 1, wherein the charge control surface layer comprises a silicon carbide composition.

27. An electrostatic chuck according to claim 26, wherein the surface resistivity of the charge control surface layer is controlled by varying the amount of silicon precursor gas and carbon precursor gas used to make the silicon carbide composition.

28. An electrostatic chuck according to claim 26, wherein the silicon carbide composition comprises silicon carbide.

29. An electrostatic chuck according to claim 26, wherein the silicon carbide composition comprises non-stoichiometric silicon carbide.

30. An electrostatic chuck according to claim 1, wherein the charge control surface layer is formed by:

blanket depositing a silicon carbide composition layer on a dielectric;

patterning the silicon carbide composition layer using photolithography; and

removing portions of the silicon carbide composition layer using reactive ion etching to leave at least one silicon carbide composition protrusion.

31. An electrostatic chuck according to claim 1, wherein the charge control surface layer is formed by:

patterning a dielectric layer using bead blasting or etching; and

conformally coating the dielectric layer with the charge control surface layer.

32. An electrostatic chuck according to claim 1, wherein the charge control surface layer comprises at least one material selected from the group consisting of diamond-like carbon, amorphous silicon, metal-doped oxide and combinations of these.

33. An electrostatic chuck according to claim 1, wherein the charge control surface layer comprises a thickness in the range of from about 1 microns to about 3 microns.

34. An electrostatic chuck according to claim 1, wherein the dielectric comprises a thickness in the range of from about 25 microns to about 250 microns.

35. An electrostatic chuck according to claim 1, wherein the charge control surface layer comprises a silicon carbide composition, and wherein the charge control surface layer comprises a thickness in the range of from about 1 microns to about 3 microns.

36. An electrostatic chuck according to claim 1, wherein the given ratio is between about 0.00407 and about 0.00306.

37. An electrostatic chuck according to claim 1, wherein the protrusions include a top surface having a peak to valley surface roughness of 2 microns R_a or less.