Monocrystalline ceramic coating having integral bonding interconnects for electrostatic chucks

• US 5,737,178 A
• Filed: 03/06/1997
• Issued: 04/07/1998
• Est. Priority Date: 03/06/1997
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Herchen, Harald
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US08/812,194
• Time in Patent Office: 397 Days
• Field of Search: 361/233, 361/234, 279/128, 117/23, 117/54, 117/950, 427/420, 118/667, 118/401, 118/429, 118/500, 501/86
• US Class Current: 361/234
• CPC Class Codes: H01L 21/6831 using electrostatic chucks
• CPC Class Codes: H01L 21/6833 Details of electrostatic chucks
• CPC Class Codes: H02N 13/00 Clutches or holding devices using electrostatic attraction, e.g. using Johnson-Rahbek effect

Abstract

An electrostatic chuck (20) comprises at least one mesh electrode (30) on an underlying dielectric layer (25), the mesh electrode having apertures therethrough. A monocrystalline ceramic (28) covers the mesh electrode (30). The monocrystalline ceramic (28) comprises a layer of large crystals substantially oriented to one another, the layer of crystals having a resistivity sufficiently high to electrically insulate the mesh electrode (30). The monocrystalline ceramic (28) further comprises integral bonding interconnects (40) that form a unitary structure with the layer of large crystals, the bonding interconnects extending through the apertures in the mesh electrode (30) to bond directly to the underlying dielectric layer (25), substantially without adhesive.

Claims

1. An erosion resistant electrostatic chuck for holding substrates in a process chamber, the chuck comprising:

(a) at least one mesh electrode on an underlying dielectric layer, the mesh electrode having apertures therethrough; and

(b) a monocrystalline ceramic covering the mesh electrode, the monocrystalline ceramic comprising;

(i) a layer of large crystals substantially oriented to one another, the layer of crystals having a resistivity sufficiently high to electrically insulate the mesh electrode; and

(ii) integral bonding interconnects that form a unitary structure with the layer of large crystals, the bonding interconnects extending through the apertures in the mesh electrode to bond directly to the underlying dielectric layer.

2. The electrostatic chuck of claim 1, wherein the monocrystalline ceramic is bonded directly to the underlying dielectric layer substantially without adhesive.

3. The electrostatic chuck of claim 1, wherein the apertures in the mesh electrode are sized (i) sufficiently small to allow the mesh electrode to generate a uniform electrostatic field for holding the substrate upon application of a voltage to the electrode, and (ii) sufficiently large to allow the bonding interconnects formed therein to securely bond the monocrystalline layer to the underlying dielectric layer.

4. The electrostatic chuck of claim 1, wherein the monocrystalline ceramic coating comprises Al₂ O₃, BeO, SiO₂, Ta₂ O₅, ZrO₂, CaO, MgO, TiO₂, BaTiO₃, AlN, TiN, BN, Si₃ N₄, ZrB₂, TiB₂, VB₂, W₂ B₃, LaB₆, MoSi₂, WSi_x, or TiSi_x.

5. The electrostatic chuck of claim 4, wherein the monocrystalline ceramic coating comprises sapphire.

6. The electrostatic chuck of claim 5, wherein underlying dielectric layer comprises sapphire.

7. The electrostatic chuck of claim 4, wherein the electrode comprises a refractory metal having a melting point of at least about 2200°

C.

8. The electrostatic chuck of claim 1, wherein the monocrystalline ceramic coating comprises at least one of the following characteristics:

(1) a dielectric breakdown strength of at least about 1000 volts/mil;

(2) a resistivity of from about 10¹³ Ω

cm to about 10²⁰ Ω

cm;

or

(3) a dielectric constant of at least about 2.

9. A process chamber comprising the electrostatic chuck of claim 1.

10. A method of forming a monocrystalline ceramic layer on a workpiece surface, the method comprising the steps of:

(a) melting a ceramic in a melt reservoir to form a molten ceramic;

(b) positioning a capillary tube in the molten ceramic of the melt reservoir, the capillary tube comprising;

(i) an inlet in the reservoir; and

(ii) an outlet adjacent to the workpiece surface, the outlet comprising (1) a leading edge having a first height and a seeding surface, and (2) a trailing edge having a second height smaller than the first height;

(c) moving the outlet of the capillary tube across the workpiece surface in a direction such that leading edge of the capillary tube moves ahead of the trailing edge, to deposit on the workpiece surface, a molten ceramic layer (i) drawn through the capillary tube, (ii) seeded by the seeding surface of the leading edge, and (iii) having a thickness t substantially controlled by the difference in first and second heights; and

(d) cooling the seeded molten ceramic layer to form a monocrystalline ceramic layer comprising large crystals substantially oriented to one another.

11. The method of claim 10, wherein the seeding surface on the leading edge comprises a seed crystal of the monocrystalline ceramic.

12. The method of claim 10, wherein the workpiece surface is continuously heated during deposition of the monocrystalline ceramic layer.

13. The method of claim 10, wherein the capillary tube comprises a diameter of from about 0.2 to 2 mm.

14. The method of claim 10, wherein the workpiece surface comprises:

(i) a dielectric layer formed by sintering a ceramic material to form a polycrystalline ceramic wafer; and

(ii) an electrode on the surface of the polycrystalline ceramic wafer.

15. The method of claim 10, wherein the workpiece surface is formed by the steps of:

(i) forming a substantially monocrystalline ceramic;

(ii) cutting a wafer of the substantially monocrystalline ceramic to form a dielectric layer; and

(iii) attaching an electrode on the surface of the monocrystalline ceramic wafer.

16. The method of claim 10, wherein the workpiece surface comprises a mesh electrode having apertures, the mesh electrode formed on an underlying dielectric layer by at least one of the following steps:

(i) etching a metal foil to form a mesh electrode and attaching the mesh electrode to the dielectric layer;

(ii) depositing a metal layer on the dielectric layer and etching the deposited metal layer to form the mesh electrode;

or

(iii) forming a pattern of resist features on the dielectric layer and depositing metal between the resist features to form the mesh electrode.

17. The method of claim 16, wherein the thickness of the monocrystalline ceramic is at least about three times the diameter of the apertures in the mesh electrode to substantially preclude spreading of an electric field around the electrode upon application of a voltage to the electrode.

18. An electrostatic chuck formed by the method of claim 16.

19. A method for fabricating an erosion resistant electrostatic chuck for holding a substrate thereon, the method comprising the steps of:

(a) forming a mesh electrode on a dielectric layer, the mesh electrode having an exposed surface and apertures therethrough;

(b) melting a ceramic in a melt reservoir to form a molten ceramic;

(c) positioning a capillary tube in the melt reservoir, the capillary tube comprising;

(i) an inlet immersed in the molten ceramic of the melt reservoir, and

(ii) an outlet adjacent to the exposed surface of the electrode, the outlet comprising (1) a leading edge having a first height and a seeding surface, and (2) a trailing edge having a second height smaller than the first height;

(d) moving the outlet of the capillary tube across the exposed surface of the electrode in a direction such that leading edge of the capillary tube moves ahead of the trailing edge, to deposit on the exposed surface, a molten ceramic layer (i) drawn through the capillary tube, (ii) seeded by the seeding surface of the leading edge, and (iii) having a thickness t substantially controlled by the difference in first and second heights; and

(e) cooling the seeded molten ceramic layer to form a monocrystalline ceramic layer comprising large crystals substantially oriented to one another.

20. The method of claim 19, wherein the workpiece surface is continuously heated during deposition of the monocrystalline ceramic layer.

21. The method of claim 19, wherein the seeding surface on the leading edge of the capillary tube outlet comprises a seed crystal of monocrystalline ceramic.

22. The method of claim 19, wherein the capillary tube comprises a diameter of from about 0.2 to 2 mm.

23. The method of claim 19, wherein step (a) comprises attaching a mesh electrode to the dielectric layer using electrostatic forces by (i) holding a conductive plate on one side of the dielectric layer, and (ii) positioning the mesh electrode on the other side, and (iii) applying a voltage to the conductive plate to generate a capacitively coupled electric field that electrostatically holds the electrode to the other side of the dielectric layer.

24. The method of claim 19, wherein step (a) comprises the steps of:

(i) forming the first dielectric layer by sintering a ceramic material to form a polycrystalline ceramic wafer; and

(ii) forming an electrode on the polycrystalline ceramic wafer.

25. The method of claim 19, wherein step (a) comprises the steps of:

(i) growing a substantially monocrystalline ceramic;

(ii) cutting a wafer of the substantially monocrystalline ceramic to form the dielectric layer; and

(iii) forming an electrode on the surface of the dielectric layer.

26. The method of claim 19, wherein in step (a) the electrode mesh is formed by at least one of the following steps:

(i) etching a metal foil to form the mesh electrode and attaching the mesh electrode on the dielectric layer;

(ii) depositing a metal layer on the dielectric layer and etching the deposited metal layer to form the mesh electrode;

or

(iii) forming a pattern of resist features on the dielectric layer and depositing metal between the resist features to form the electrode.

27. The method of claim 19, wherein the thickness t of the monocrystalline ceramic is at least about three times the diameter of apertures in the mesh electrode to substantially preclude spreading of electric field around the electrode upon application of a voltage to the electrode.

28. An electrostatic chuck comprising a monocrystalline ceramic layer formed by the method of claim 19.

29. An electrostatic chuck for holding substrates in a process chamber, the chuck comprising:

(a) a first monocrystalline ceramic layer comprising at least one mesh electrode thereon, the mesh electrode having apertures therethrough; and

(b) a second monocrystalline ceramic layer covering the mesh electrode, the second monocrystalline ceramic layer comprising integral bonding interconnects that extend through the apertures in the mesh electrode to bond directly to the first monocrystalline ceramic layer,

wherein the first and second monocrystalline ceramic layers comprise large crystals substantially oriented to one another, the crystals having a resistivity sufficiently high to electrically insulate the mesh electrode.

30. The electrostatic chuck of claim 29, wherein the monocrystalline ceramic layer is bonded directly to the underlying dielectric layer substantially without adhesive.

31. The electrostatic chuck of claim 29, wherein the electrode comprises a pattern of lattice defects induced in the first monocrystalline ceramic layer.

32. The electrostatic chuck of claim 29, wherein the mesh electrode comprise a pattern of dopant in the first monocrystalline ceramic layer.

33. The electrostatic chuck of claim 29, wherein the apertures in the mesh electrode are sized (i) sufficiently small to allow the mesh electrode to generate a uniform electrostatic field for holding the substrate upon application of a voltage to the electrode, and (ii) sufficiently large to allow the bonding interconnects formed therein to securely bond the second monocrystalline layer to the first monocrystalline ceramic layer.

34. The electrostatic chuck of claim 29, wherein the first and second monocrystalline ceramic layers comprise Al₂ O₃, BeO, SiO₂, Ta₂ O₅, ZrO₂, CaO, MgO, TiO₂, BaTiO₃, AlN, TiN, BN, Si₃ N₄, ZrB₂, TiB₂, VB₂, W₂ B₃, LaB₆, MoSi₂, WSi_x, or TiSi_x.

35. The electrostatic chuck of claim 29, wherein the first and second monocrystalline ceramic layers comprises sapphire.

36. A process chamber comprising the electrostatic chuck of claim 29.

37. A method for fabricating an electrostatic chuck for holding a substrate thereon, the method comprising the steps of:

(a) forming a first monocrystalline ceramic layer;

(b) forming a mesh electrode on a first monocrystalline ceramic layer, the mesh electrode having an exposed surface and apertures therethrough;

(c) melting a ceramic in a melt reservoir to form a molten ceramic;

(d) positioning a capillary tube in the melt reservoir, the capillary tube comprising;

(i) an inlet immersed in the molten ceramic of the melt reservoir, and

(ii) an outlet adjacent to the exposed surface of the mesh electrode, the outlet comprising (1) a leading edge having a first height and a seeding surface, and (2) a trailing edge having a second height smaller than the first height;

(e) moving the outlet of the capillary tube across the exposed surface of the electrode in a direction such that leading edge of the capillary tube moves ahead of the trailing edge, to deposit on the exposed surface, a molten ceramic layer (i) drawn through the capillary tube, (ii) seeded by the seeding surface of the leading edge, and (iii) having a thickness t substantially controlled by the difference in first and second heights; and

(f) cooling the seeded molten ceramic layer to form a monocrystalline ceramic layer comprising large crystals substantially oriented to one another.

38. The method of claim 37, wherein the mesh electrode is fabricated by inducing a pattern of lattice damage in the first monocrystalline ceramic layer.

39. The method of claim 37, wherein the mesh electrode is formed by doping the monocrystalline ceramic layer with a pattern of dopants.

40. The method of claim 37, wherein the workpiece surface is continuously heated during deposition of the monocrystalline ceramic layer.

41. The method of claim 37, wherein the seeding surface on the leading edge of the capillary tube outlet comprises a seed crystal of monocrystalline ceramic.

42. The method of claim 37, wherein the thickness t of the second monocrystalline ceramic is at least about three times the diameter of apertures in the mesh electrode to substantially preclude spreading of electric field around the electrode upon application of a voltage to the electrode.

43. An electrostatic chuck formed by the method of claim 37.

44. An electrostatic chuck for holding a substrate in a process chamber, the chuck comprising:

(a) a monocrystalline ceramic comprising large crystals substantially oriented to one another;

(b) an electrode embedded in the monocrystalline ceramic for electrostatically holding the substrate upon application of a voltage to the electrode; and

(c) an electrical connector for supplying a voltage to the electrode, the electrical connector extending through the monocrystalline ceramic.

45. The electrostatic chuck of claim 44 wherein the monocrystalline ceramic comprises bonding interconnects that extend through apertures in the electrode.

46. The electrostatic chuck of claim 45 wherein the apertures are sized sufficiently small to allow the electrode to electrostatically hold the substrate upon application of a voltage to the electrode, and sufficiently large to allow the bonding interconnects to securely hold the electrode in the monocrystalline ceramic.

47. The electrostatic chuck of claim 44 wherein the monocrystalline ceramic comprises one or more of Al₂ O₃, BeO, SiO₂, Ta₂ O₅, ZrO₂, CaO, MgO, TiO₂, BaTiO₃, AlN, TiN, BN, Si₃ N₄, ZrB₂, TiB₂, VB₂, W₂ B₃, LaB₆, MoSi₂, WSi_x, and TiSi_x.

48. The electrostatic chuck of claim 44 wherein the monocrystalline ceramic consists essentially of sapphire.

49. The electrostatic chuck of claim 48 wherein the electrode comprises a refractory metal having a melting point of at least about 2200°

C.

50. The electrostatic chuck of claim 44 wherein the monocrystalline ceramic comprises a dielectric breakdown strength of at least about 1000 volts/mil.

51. A process chamber comprising the electrostatic chuck of claim 44.

52. An electrostatic chuck for holding a substrate in a process chamber, the chuck comprising:

(a) a mesh electrode having apertures therethrough;

(b) an unitary structure of monocrystalline ceramic surrounding the mesh electrode, the monocrystalline ceramic comprising large crystals substantially oriented to one another, and bonding interconnects integral to the crystals and extending through the apertures in the mesh electrode to hold the mesh electrode in the unitary structure; and

(c) an electrical connector extending through the unitary structure to provide a voltage to the electrode.

53. The electrostatic chuck of claim 52 wherein the apertures in the mesh electrode are sized (i) sufficiently small to provide an electrode area that can electrostatically hold the substrate upon application of a voltage to the electrode, and (ii) sufficiently large to allow the bonding interconnects to securely hold the electrode in the unitary structure.

54. The electrostatic chuck of claim 52 wherein the monocrystalline ceramic comprises one or more of Al₂ O₃, BeO, SiO₂, Ta₂ O₅, ZrO₂, CaO, MgO, TiO₂, BaTiO₃, AlN, TiN, BN, Si₃ N₄, ZrB₂, TiB₂, VB₂, W₂ B₃, LaB₆, MoSi₂, WSi_x, and TiSi_x.

55. The electrostatic chuck of claim 52 wherein the monocrystalline ceramic consists essentially of sapphire.

56. The electrostatic chuck of claim 52 wherein the electrode comprises a refractory metal having a melting point of at least about 2200°

C.

57. The electrostatic chuck of claim 52 wherein the monocrystalline ceramic comprises a dielectric breakdown strength of at least about 1000 volts/mil.

58. A process chamber comprising the electrostatic chuck of claim 52.