Inductive plasma reactor

• US 6,143,129 A
• Filed: 07/17/1998
• Issued: 11/07/2000
• Est. Priority Date: 11/15/1994
• Status: Expired due to Fees

• Current Assignee: Mattson Technology, Inc. (Beijing Economic & Technology Development Area)
• Original Assignee: Mattson Technology, Inc. (Beijing Economic & Technology Development Area)
• Inventors: Savas, Stephen E., Selbrede, Steven C., Hammond, Martin L., Mattson, Brad S.
• Primary Examiner(s): DANG, THI D
• Application Number:
  US09/118,281
• Time in Patent Office: 844 Days
• Field of Search: 156/345, 118/723 ER, 118/723 IR, 438/725, 204/298.36, 216/68, 216/67
• US Class Current: 156/345.48
• 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 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;

a substrate processing region for processing a substrate at a distance from the plasma producing region;

wherein the pressure in the plasma processing region is substantially the same as the pressure in the substrate processing region;

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 a flow path between the plasma producing region and the substrate producing region, the conductive material comprising a first conductive ring substantially surrounding the flow path and a second conductive ring substantially surrounding the flow path, the second conductive ring spaced apart from the first conductive ring;

wherein the first conductive ring is grounded and an electrical potential is applied to the second conductive ring; 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.

2. The plasma reactor of claim 1, wherein the first conductive ring is separated from the second conductive ring by a block of insulating material.

3. 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 adjacent to the flow path between the plasma producing region and the substrate, the charged particle filter comprising a first conductive ring substantially surrounding the flow path and a second conductive ring substantially surrounding the flow path, the second conductive ring spaced apart from the first conductive ring;

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; and

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.

4. The plasma reactor of claim 3, wherein the first conductive ring is grounded and an electrical potential is applied to the second conductive ring.

5. The plasma reactor of claim 4, wherein the first conductive ring is separated from the second conductive ring by a block of insulating material.

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;

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 substantially surrounding the flow, wherein the charged particles are deflected using an electric field transverse to the flow path; and

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

7. The method of claim 6, wherein the charged particles are deflected using a magnetic filter.

8. The method of claim 6, wherein the step of forming a plasma further comprises the step of inducing an electric field in the chamber substantially parallel to the substrate.

9. A plasma reactor for processing a substrate comprising:

a reactor chamber within which a plasma is generated to produce at least one plasma product for processing a semiconductor substrate;

a gas source coupled to the reactor chamber to provide gas into the reactor chamber;

an exhaust system coupled to the reactor chamber to exhaust gas from the reactor chamber;

a first source of radio frequency power;

an induction coil adjacent to the reactor chamber and 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 first capacitive shield between the induction coil and the plasma;

a second capacitive shield between the induction coil and the plasma, the second capacitive shield spaced apart from the first capacitive shield;

wherein the second capacitive shield substantially reduces the capacitive coupling from the induction coil to the plasma relative to the level of capacitive coupling that would be present in the absence of the second capacitive shield; and

a support for the semiconductor substrate positioned such that the semiconductor substrate is exposed to the at least one plasma product during processing.

10. The plasma reactor of claim 9 wherein the first and second capacitive shields are electrically isolated from one another.

11. The plasma reactor of claim 9 wherein the first capacitive shield is an inner shield and the second capacitive shield is an outer shield.

12. The plasma reactor of claim 9 wherein an inductance along a current path from the induction coil to ground causes a voltage to appear on the outer shield ranging from about 5 to 10 volts, and a voltage to appear on the inner shield of about 1 volt.

13. The plasma reactor of claim 9 wherein the modulation of the plasma potential is about 0.1 volts.

14. The plasma reactor of claim 11 wherein the outer shield is connected to ground through an impedance that is minimized for a given RF frequency.

15. The plasma reactor of claim 14 wherein the impedance is provided by a series LC circuit.

16. A method of processing a semiconductor substrate in a plasma reactor comprising the steps of:

supplying a gas to a reaction chamber;

shielding the gas in the reaction chamber with a first capacitive shield, the first capacitive shield forming at least one substantially nonconductive gap to allow the passage of inductively coupled power to the gas in the reaction chamber;

shielding the gas in the reaction chamber with a second capacitive shield, the second capacitive shield forming at least one substantially nonconductive gap to allow the passage of inductively coupled power to the gas in the reaction chamber, wherein the second capacitive shield is spaced apart from the first capacitive shield;

inductively coupling power into the reaction chamber through the first capacitive shield and the second capacitive shield;

forming at least one plasma product for processing the semiconductor substrate; and

exposing the semiconductor to the at least one plasma product for processing.

17. The method of claim 16 wherein the first and second capacitive shields are electrically isolated from one another.

18. The method of claim 16 wherein the first capacitive shield is an inner shield and the second capacitive shield is an outer shield.

19. The method of claim 18 wherein an inductance along a current path from the induction coil to ground causes a voltage to appear on the outer shield ranging from about 5 to 10 volts, and a voltage to appear on the inner shield of about 1 volt.

20. The method of claim 16 wherein the modulation of the plasma potential is about 0.1 volts.

21. The method of claim 18 wherein the outer shield is grounded through an impedance that is minimized for a given RF frequency.

22. The method of claim 21 wherein the impedance is provided by a series LC circuit.

23. A plasma reactor for processing a substrate comprising:

a reactor chamber within which a plasma is generated to produce at least one plasma product for processing a semiconductor substrate;

a first source of radio frequency power;

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

a capacitive shield between the induction coil and the plasma;

a circuit between the capacitive shield and a reference potential configured to provide at least a first mode of operation for the shield and a second mode of operation for the shield;

wherein the level of capacitive shielding is substantially different between the first and second modes; and

a support for the semiconductor substrate positioned such that the semiconductor substrate is exposed to the plasma product during processing.

24. The plasma reactor of claim 23 wherein the circuit is adjustable to vary the coupling of the shield to ground for different modes of operation.

25. The plasma reactor of claim 24 wherein the shield is substantially connected to ground in the first mode, and substantially ungrounded in the second mode.

26. The plasma reactor of claim 24 wherein the circuit is a series LC circuit.

27. The plasma reactor of claim 24 wherein the impedance of current flowing from the shield to ground is varied with a series LC circuit.

28. The plasma reactor of claim 23 wherein the capacitive coupling to the plasma is varied by adjusting the spacing between the shield and the induction coil.

29. The plasma reactor of claim 23 wherein the capacitive coupling to the plasma is varied by adjusting the spacing between the shield and the plasma.

30. A method of processing a semiconductor substrate in a plasma reactor, the method comprising the steps of:

supplying a gas to a reaction chamber;

forming at least one plasma product from the gas for processing the semiconductor substrate;

shielding at least a portion of the reaction chamber with a capacitive shield;

inductively coupling power through the capacitive shield;

varying the coupling of the shield to a reference potential to vary the level of shielding; and

exposing the semiconductor substrate to the at least one plasma product.

31. The method of claim 30 wherein the capacitive coupling to the plasma is varied by adjusting the coupling of the shield to ground.

32. The method of claim 31 wherein the shield is connected to ground through an LC circuit.

33. The method of claim 31 wherein the impedance of current flowing from the shield to ground is varied with a series LC circuit.

34. The method of claim 30 wherein the capacitive coupling to the plasma is varied by adjusting the spacing between the shield and the induction coil.

35. The method of claim 30 wherein the capacitive coupling to the plasma is varied by adjusting the spacing between the shield and the plasma.