Inductive plasma reactor

• US 5,811,022 A
• Filed: 11/15/1994
• Issued: 09/22/1998
• Est. Priority Date: 11/15/1994
• Status: Expired due to Term

• Current Assignee: Mattson Technology, Inc. (Beijing Economic & Technology Development Area)
• Original Assignee: Mattson Technology, Inc. (Beijing Economic & Technology Development Area)
• Inventors: Savas, Stephen E., Mattson, Brad S.
• Primary Examiner(s): DANG, THI D
• Application Number:
  US08/340,696
• Time in Patent Office: 1,407 Days
• Field of Search: 156/345, 118/723 I, 118/723 IR, 118/723 ER, 204/298.31, 204/298.36, 204/298.34, 204/298.08, 216/68, 438/725, 438/729, 438/730, 438/731
• US Class Current: 216/68
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/32706 Polarising the substrate
• CPC Class Codes: H01J 37/32871 Means for trapping or directing unwanted particles
• CPC Class Codes: Y10S 156/912 Differential etching apparatus having a vertical tube reactor

Abstract

A plasma reactor and methods for processing semiconductor wafers are described. Gases are introduced into a reactor chamber. An induction coil surrounds the reactor chamber. RF power is applied to the induction coil and is inductively coupled into the reactor chamber causing a plasma to form. A split Faraday shield is interposed between the induction coil and the reactor chamber to substantially block the capacitive coupling of energy into the reactor chamber which may modulate the plasma potential. The configuration of the split Faraday shield may be selected to control the level of modulation of the plasma potential. For etch processes, a separate powered electrode may be used to accelerate ions toward a wafer surface. For isotropic etching processes, charged particles may be filtered from the gas flow, while a neutral activated species passes unimpeded to a wafer surface.

Claims

1. A method for removing photoresist from a surface of a substrate, the method comprising the steps of:

forming a plasma in a chamber, the plasma containing an activated neutral species and charged particles;

positioning the substrate a distance from the plasma;

inducing a flow of the activated neutral species from the plasma substantially perpendicularly toward the surface of the substrate;

deflecting the charged particles from the flow to a conductive collecting vane positioned between the plasma and the substrate; and

exposing the surface of the substrate to the activated neutral species to remove the photoresist;

wherein the charged particles are deflected using a magnetic field.

2. A method for removing photoresist from a surface of a substrate, the method comprising the steps of:

forming a plasma in a chamber, the plasma containing an activated neutral species and charged particles;

positioning the substrate a distance from the plasma;

maintaining the average energy of the charged particles in a direction substantially perpendicular to the substrate at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate;

inducing a flow of the activated neutral species from the plasma substantially perpendicularly toward the surface of the substrate;

deflecting the charged particles from the flow to a conductive collecting vane positioned between the plasma and the substrate; and

exposing the surface of the substrate to the activated neutral species to remove the photoresist;

wherein the conductive collecting vane forms a first plurality of closely spaced openings and the step of inducing a flow further comprises the step of causing the activated neutral species to flow through the first plurality of closely spaced openings.

3. The method of claim 2, wherein the conductive collecting vane forms a second plurality of closely spaced openings offset from the first plurality of closely spaced openings and the step of inducing a flow further comprises the step of causing the activated neutral species to flow through the second plurality of closely spaced openings.

4. A method for removing photoresist from a surface of a substrate, the method comprising the steps of:

forming a plasma in a chamber, the plasma containing an activated neutral species and charged particles;

positioning the substrate a distance from the plasma;

maintaining the average energy of the charged particles in a direction substantially perpendicular to the substrate at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate;

inducing a flow of the activated neutral species from the plasma substantially perpendicularly toward the surface of the substrate;

deflecting the charged particles from the flow to a conductive collecting vane positioned between the plasma and the substrate; and

exposing the surface of the substrate to the activated neutral species to remove the photoresist;

wherein the step of forming a plasma further comprises the step of inducing an electric field in the chamber substantially parallel to the substrate; and

wherein the conductive collecting vane is substantially planar and is substantially parallel to the substrate.

5. A method for removing photoresist from a surface of a substrate, the method comprising the steps of:

forming a plasma in a chamber the plasma containing an activated neutral species and charged particles;

positioning the substrate a distance from the plasma;

maintaining the average energy of the charged particles in a direction substantially perpendicular to the substrate at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate;

inducing a flow of the activated neutral species from the plasma substantially perpendicularly toward the surface of the substrate;

deflecting the charged particles from the flow to a conductive collecting vane positioned between the plasma and the substrate; and

exposing the surface of the substrate to the activated neutral species to remove the photoresist;

wherein the step of forming a plasma further comprises the steps of;

inductively coupling power from an induction coil into the plasma; and

shielding the chamber to substantially reduce capacitive coupling of power from the induction coil into the plasma.

6. A method for removing photoresist from a surface of a substrate, the method comprising the steps of:

forming a plasma in a chamber, the plasma containing an activated neutral species and charged particles;

positioning the substrate a distance from the plasma;

positioning a conductive charged particle filter between the plasma and the substrate, the charged particle filter forming a first plurality of holes for receiving the activated neutral species from the plasma and a second plurality of holes offset from the first plurality of holes for providing the activated neutral species to the substrate;

inducing a flow of the activated neutral species from the plasma to the substrate through the charged particle filter; and

exposing the surface of the substrate to the activated neutral species to remove the photoresist.

7. The method of claim 6, wherein the step of exposing the substrate to the activated neutral species further comprises the step of dispensing the activated neutral species through the second plurality of openings substantially uniformly across the surface of the substrate.

8. A method for removing photoresist from a surface of a substrate, the method comprising the steps of:

forming a plasma in a chamber, the plasma containing an activated neutral species and charged particles;

positioning the substrate a distance from the plasma;

positioning a conductive charged particle filter between the plasma and the substrate, the charged particle filter forming a first plurality of holes for receiving the activated neutral species from the plasma and a second plurality of holes offset from the first plurality of holes for providing the activated neutral species to the substrate;

inducing a flow of the activated neutral species from the plasma to the substrate through the charged particle filter;

exposing the surface of the substrate to the activated neutral species to remove the photoresist; and

maintaining at least two portions of the filter at different potentials.

9. A plasma reactor for processing a substrate comprising:

a plasma chamber for producing a plasma having charged particles and an activated neutral species;

a processing chamber containing the substrate; and

a charged particle filter disposed between the plasma chamber and the processing chamber, the filter having a first filter member forming a plurality of openings for receiving the activated neutral species from the plasma chamber and a second filter member forming a plurality of openings for providing the activated neutral species to the processing chamber offset from the plurality of openings in the first filter member;

wherein the filter forms a flow path from the plasma chamber to the processing chamber such that the activated neutral species flows from the plasma chamber to the substrate for processing, and each respective opening over the substrate in at least one of the filter members is spaced from adjacent openings by a distance less than the distance across the respective opening.

10. The plasma reactor of claim 9, wherein the second filter member is closely spaced to the first filter member forming a small gap between the first and second filter members for trapping and filtering the charged particles.

11. The plasma reactor of claim 9, wherein the second filter member forms a surface substantially parallel to the substrate.

12. The plasma reactor of claim 9, wherein the openings in the second filter member are offset from the openings in the first filter member such that ultraviolet radiation is substantially prevented from radiating from the plasma chamber to the processing chamber through the filter.

13. The plasma reactor of claim 9, wherein the flow path is nonlinear.

14. The plasma reactor of claim 9, wherein a potential of the plasma relative to the filter is maintained at a level such that a plasma discharge within the filter is substantially prevented.

15. The plasma reactor of claim 9, wherein said first and second filter members are spaced apart by an insulating material.

16. The plasma reactor of claim 9, wherein the openings in the second filter member are offset from the openings in the first filter member;

and

the distance between the first and second filter members and the size of the openings in the first and second filter members are selected such that substantially all paths through the filter are non-linear.

17. The plasma reactor of claim 9, wherein each of the openings in the first filter member has a diameter and is spaced from adjacent openings in the first filter member by a distance less than the diameter.

18. The plasma reactor of claim 9, wherein each of the openings in the second filter member has a diameter and is spaced from adjacent openings in the second filter member by a distance less than the diameter.

19. The plasma reactor of claim 17, wherein each respective opening in the second filter member has a diameter and is spaced from adjacent openings in the second filter member by a distance less than the diameter of the respective opening in the second filter member.

20. The plasma reactor of claim 9, wherein the first and second filter members are spaced apart by a distance, and the first filter member has a thickness greater than the distance between the first and second filter members.

21. The plasma reactor of claim 20, wherein the second filter member has a thickness greater than the distance between the first and second filter members.

22. The plasma reactor of claim 17, wherein the first and second filter members are spaced apart by a short distance, and the diameter of each of the openings in the second filter member is greater than the short distance.

23. The plasma reactor of claim 9, further comprising a power source coupled to the filter such that an electric field is induced between the first and second filter members to enhance the filtration of the charged particles from the flow path.

24. The plasma reactor of claim 10, further comprising a power source for inducing an electric field across the small gap such that the charged particles are deflected from the flow path.

25. The plasma reactor of claim 19, further comprising a power source coupled to the filter such that an electric field is induced between the first and second filter members to enhance the filtration of the charged particles from the flow path.

26. The plasma reactor of claim 20, further comprising a power source coupled to the filter such that an electric field is induced between the first and second filter members to enhance the filtration of the charged particles from the flow path.

27. The plasma reactor of claim 9, further comprising a third filter member disposed between the first filter member and the second filter member, the third filter member forming a plurality of openings such that the activated neutral species may pass through the third filter member.

28. The plasma reactor of claim 27, wherein the third filter member comprises a conductive material for filtering charged particles from the flow path.

29. The plasma reactor of claim 27, further comprising a power source coupled to the filter such that an electric field is induced between the first and third filter members to enhance the filtration of the charged particles from the flow path.

30. The plasma reactor of claim 27, further comprising a power source coupled to the filter such that an electric field is induced between the second and third filter members to enhance the filtration of the charged particles from the flow path.

31. The plasma reactor of claim 29, wherein a second electric field is induced between the third and second filter members to enhance the filtration of the charged particles from the flow path.

32. A plasma reactor for processing a substrate comprising:

a plasma chamber for producing a plasma having charged particles and an activated neutral species;

a processing chamber containing the substrate; and

a filter disposed between the plasma chamber and the processing chamber, the filter comprising a plurality of adjacent grids including a first grid forming an array of closely spaced openings and a second grid forming an array of closely spaced openings offset from the array of closely spaced openings in the first grid;

wherein a flow path is defined between the plasma chamber and the processing chamber and the first and second grids comprise a conductive material for filtering charged particles from the flow path.

33. The plasma reactor of claim 32, wherein each grid is closely spaced to an adjacent grid such that a small gap is formed for trapping and filtering the charged particles.

34. The plasma reactor of claim 32 wherein the first and second grids are spaced apart by a short distance, and at least one of the grids of the filter has a thickness greater than the short distance.

35. The plasma reactor of claim 32, wherein the grids are substantially parallel to the substrate.

36. The plasma reactor of claim 35, further comprising a first source of radio frequency power;

and

an induction coil adjacent to the plasma chamber, the induction coil coupled to the first source of radio frequency power to inductively couple power into the plasma from the first source of radio frequency power;

wherein the induction coil produces an induction electric field in the plasma chamber substantially parallel to the grids and the substrate.

37. The plasma reactor of claim 36, further comprising a split Faraday shield disposed between the induction coil and the plasma chamber.

39. The plasma reactor of claim 33, further comprising a power source wherein the power source induces an electric field within the filter such that charged particles are attracted to at least one of the grids of the filter.

38. A plasma reactor for processing a substrate comprising:

a plasma chamber for producing a plasma having charged particles and an activated neutral species;

a processing chamber containing the substrate; and

a filter disposed between the plasma chamber and the processing chamber, the filter comprising a plurality of adjacent grids including a first grid forming an array of closely spaced openings and a second grid forming an array of closely spaced openings offset from the array of closely spaced openings in the first grid;

wherein a flow path is defined between the plasma chamber and the processing chamber and the first and second grids comprise a conductive material for filtering charged particles from the flow path;

wherein each grid is closely spaced to an adjacent grid such that a small gap is formed for trapping and filtering the charged particles; and

further comprising a third grid forming an array of closely spaced openings offset from the array of closely spaced openings in the second grid.

40. A plasma reactor for processing a substrate comprising:

a chamber including a plasma producing region for producing a plasma having charged particles and an activated neutral species,

the substrate positioned a distance from the plasma producing region,

a flow path being defined between the plasma producing region and the substrate, the flow path being substantially perpendicular to a surface of the substrate;

a first source of radio frequency power;

an induction coil adjacent to the plasma producing region of the chamber, the induction coil coupled to the first source of radio frequency power to inductively couple power into the plasma from the first source of radio frequency power;

a conductive material adjacent to the flow path between the plasma producing region and the substrate; and

a second power source for inducing an electric field within the chamber such that charged particles are deflected from the flow path to the conductive material for filtration;

wherein the average energy of the charged particles in a direction substantially perpendicular to the substrate is maintained at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate; and

the conductive material comprises a grid substantially transverse to the flow path.

41. A plasma reactor for processing a substrate comprising:

a chamber including a plasma producing region for producing a plasma having charged particles and an activated neutral species,

the substrate positioned a distance from the plasma producing region,

a flow path being defined between the plasma producing region and the substrate, the flow path being substantially perpendicular to a surface of the substrate;

a first source of radio frequency power;

an induction coil adjacent to the plasma producing region of the chamber, the induction coil coupled to the first source of radio frequency power to inductively couple power into the plasma from the first source of radio frequency power;

a conductive material adjacent to the flow path between the plasma producing region and the substrate; and

a second power source for inducing an electric field within the chamber such that charged particles are deflected from the flow path to the conductive material for filtration; and

a split Faraday shield disposed between the induction coil and the plasma producing region of the chamber wherein the average energy of the charged particles in a direction substantially perpendicular to the substrate is maintained at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate.

42. A plasma reactor for processing a substrate comprising:

a chamber including a plasma producing region for producing a plasma having charged particles and an activated neutral species;

the substrate being positioned a distance from the plasma producing region;

a flow path being defined between the plasma producing region and the substrate;

a first source of radio frequency power;

an induction coil adjacent to the plasma producing region of the chamber, the induction coil coupled to the first source of radio frequency power to inductively couple power into the plasma from the first source of radio frequency power;

a charged particle filter disposed between the plasma producing region and the substrate transverse to the flow path; and

a split Faraday shield between the induction coil and the plasma, the split Faraday shield forming at least one substantially nonconductive gap such that the induction coil inductively couples power into the plasma from the first radio frequency power source;

wherein the split Faraday shield substantially reduces capacitive coupling between the induction coil and the plasma thereby reducing modulation of the plasma potential relative to the potential of the charged particle filter;

wherein the average energy of the charged particles in a direction substantially perpendicular to the substrate is maintained at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate; and

wherein the filter is substantially planar and the induction coil produces an induction electric field in the chamber that is substantially parallel to the filter.

43. The plasma reactor of claim 42, wherein the filter comprises a conductive material.

44. A plasma reactor for processing a substrate comprising:

a chamber including a plasma producing region for producing a plasma having charged particles and an activated neutral species;

the substrate being positioned a distance from the plasma producing region;

a flow path being defined between the plasma producing region and the substrate;

a first source of radio frequency power;

an induction coil adjacent to the plasma producing region of the chamber, the induction coil coupled to the first source of radio frequency power to inductively couple power into the plasma from the first source of radio frequency power;

a charged particle filter disposed between the plasma producing region and the substrate transverse to the flow path; and

a split Faraday shield between the induction coil and the plasma, the split Faraday shield forming at least one substantially nonconductive gap such that the induction coil inductively couples power into the plasma from the first radio frequency power source;

wherein the split Faraday shield substantially reduces capacitive coupling between the induction coil and the plasma thereby reducing modulation of the plasma potential relative to the potential of the charged particle filter;

wherein the average energy of the charged particles in a direction substantially perpendicular to the substrate is maintained at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate;

wherein the charged particle filter comprises a conductive material; and

wherein the filter forms at least one hollow region and the split Faraday shield prevents hollow cathode discharge from occurring in the hollow region of the filter.

45. A plasma reactor for processing a substrate comprising:

a chamber including a plasma producing region for producing a plasma having charged particles and an activated neutral species;

the substrate being positioned a distance from the plasma producing region;

a flow path being defined between the plasma producing region and the substrate;

a first source of radio frequency power;

an induction coil adjacent to the plasma producing region of the chamber, the induction coil coupled to the first source of radio frequency power to inductively couple power into the plasma from the first source of radio frequency power;

a charged particle filter disposed between the plasma producing region and the substrate transverse to the flow path;

a split Faraday shield between the induction coil and the plasma, the split Faraday shield forming at least one substantially nonconductive gap such that the induction coil inductively couples power into the plasma from the first radio frequency power source;

wherein the split Faraday shield substantially reduces capacitive coupling between the induction coil and the plasma thereby reducing modulation of the plasma potential relative to the potential of the charged particle filter;

wherein the average energy of the charged particles in a direction substantially perpendicular to the substrate is maintained at a substantially lower level than the average energy of the charged particles in a direction substantially parallel to the substrate;

wherein the charged particle filter comprises a conductive material; and

wherein the charged particle filter comprises a plurality of adjacent grids including a first grid forming an array of closely spaced openings and a second grid forming an array of closely spaced openings offset from the array of closely spaced openings in the first grid.

46. The plasma reactor of claim 45, wherein the first and second grids are spaced apart by a short distance, and at least one of the grids of the filter has a thickness greater than the short distance.

47. The plasma reactor of claim 45, further comprising a second power source wherein the second power source induces an electric field within the filter such that charged particles are attracted to the grids of the filter.

48. A plasma reactor for processing a substrate comprising:

a plasma chamber for producing a plasma;

a first source of radio frequency power;

an induction coil adjacent the plasma and coupled to the first source of radio frequency power to inductively couple power into the plasma from the first radio frequency power source;

a split Faraday shield between the induction coil and the plasma, the split Faraday shield forming at least one substantially nonconductive gap such that the induction coil inductively couples power into the plasma from the first radio frequency power source; and

a support for the substrate positioned such that the substrate is exposed to products of the plasma for processing;

wherein a capacitance and an inductance are provided between the support and a ground potential and the capacitance and the inductance are selected to provide a high impedance for a given frequency of the first source of radio frequency power during processing.

49. The plasma reactor of claim 48, wherein the capacitance and the inductance are provided by a parallel LC circuit disposed between the support and the ground potential.

50. The plasma reactor of claim 48, further comprising a charged particle filter disposed between the plasma and the substrate.

51. A plasma reactor for processing a substrate comprising:

a plasma chamber for producing a plasma;

a first source of radio frequency power;

an induction coil adjacent the plasma and coupled to the first source of radio frequency power to inductively couple power into the plasma from the first radio frequency power source;

a split Faraday shield between the induction coil and the plasma, the split Faraday shield forming at least one substantially nonconductive gap such that the induction coil inductively couples power into the plasma from the first radio frequency power source; and

a support for the substrate positioned such that the substrate is exposed to products of the plasma for processing;

wherein a variable impedance is provided between the split Faraday shield and a ground potential and the variable impedance is selected such that the impedance is very low for a given frequency of the first source of radio frequency power during processing.

52. The plasma reactor of claim 51, wherein the variable impedance is selected such that the impedance is high for the given frequency during ignition of the plasma reactor.

53. The plasma reactor of claim 51, wherein the variable impedance is provided by a series LC circuit.

54. The plasma reactor of claim 53, wherein the series LC circuit includes a variable capacitor.

55. The plasma reactor of claim 51, further comprising a charged particle filter disposed between the plasma and the substrate.

56. The plasma reactor of claim 55, wherein the charged particle filter comprises a conductive material.

57. The plasma reactor of claim 56, wherein the charged particle filter comprises a plurality of adjacent grids including a first grid forming an array of closely spaced openings and a second grid forming an array of closely spaced openings offset from the array of closely spaced openings in the first grid.