System and method for performing sputter deposition with multiple targets using independent ion and electron sources and independent target biasing with DC pulse signals

• US 20020189938A1
• Filed: 05/02/2002
• Published: 12/19/2002
• Est. Priority Date: 03/16/2001
• Status: Active Grant

• Current Assignee: 4Wave, Inc.
• Original Assignee: 4Wave, Inc.
• Inventors: Hylton, Todd Lanier, Baldwin, David Alan
• Granted Patent: US 6,679,976 B2
• Time in Patent Office: Days
• US Class Current: 204/298.03
• CPC Class Codes: C23C 14/46 by ion beam produced by an external ion source
• CPC Class Codes: C23C 14/54 Controlling or regulating the coating process
• CPC Class Codes: H01J 37/3178 for applying thin layers on objects
• CPC Class Codes: H01J 37/3233 using charged particles
• CPC Class Codes: H01J 37/34 operating with cathodic sputtering H01J37/36 takes precedence ; methods of cathodic sputtering C23C14/34

Abstract

A system and method for performing sputter deposition includes at least one ion source that generates at least one ion current directed at first and second targets, at least one electron source that generates at least one electron current directed at the first and second targets, and circuitry that biases the first and second targets with independent first and second DC voltage pulse signals. A first current sensor, coupled to the biasing circuitry, monitors a positive current and a negative current from the first target during one or more cycles of the first DC voltage pulse signal, and a second current sensor, coupled to the biasing circuitry, monitors a positive current and a negative current from the second target during one or more cycles of the second DC voltage pulse signal. A controller, coupled to the first and second current sensors, varies the at least one ion current independently from the at least one electron current. The at least one ion source and the at least one electron source create a continuous plasma proximate the first and second targets. The ions attracted from the plasma sputter the first and second targets and material from the first and second targets is deposited on a substrate.

Claims

1. A multi-target system for performing sputter deposition, comprising:

(a) at least one ion source that generates at least one ion current directed at at least first and second targets;

(b) at least one electron source that generates at least one electron current directed at the at least first and second targets;

(c) biasing circuitry that biases the first target with a first DC voltage pulse signal and that biases the second target with a second DC voltage pulse signal that is independent of the first DC voltage pulse signal, the biasing circuitry being formed from at least one voltage source with respect to ground, a first high frequency switch used to form the first DC voltage pulse signal, and a second high frequency switch used to form the second DC voltage pulse signal;

(d) a first current sensor, coupled to the biasing circuitry, that monitors a positive current and a negative current from the first target during one or more cycles of the first DC voltage pulse signal;

(e) a second current sensor, coupled to the biasing circuitry, that monitors a positive current and a negative current from the second target during one or more cycles of the second DC voltage pulse signal;

(f) a controller, coupled to the first and second current sensors, that varies the at least one ion current independently from the at least one electron current;

(g) wherein the at least one ion source and the at least one electron source create a continuous plasma proximate the first and second targets, and the biasing circuitry causes the first and second targets to alternately attract ions and electrons from the plasma;

(h) wherein the ions attracted from the plasma sputter the first and second targets and material from the first and second targets is deposited on a substrate; and

(i) wherein the electrons attracted from the plasma neutralize accumulated charge on the first and second targets.

2. The system of claim 1, wherein material from the first target deposited on the substrate corresponds to a first component of an alloy, and material from the second target deposited on the substrate corresponds to a second component of the alloy.

3. The system of claim 2, wherein the controller varies a composition ratio of the first and second components of the alloy deposited on the substrate by independently varying a number of negative pulses per unit time in each of the first and second DC voltage pulse signals.

4. The system of claim 2, wherein the controller varies a composition ratio of the first and second components of the alloy deposited on the substrate by independently varying a length of negative pulses per unit time in each of the first and second DC voltage pulse signals.

5. The system of claim 2, wherein the controller varies a composition ratio of the first and second components of the alloy deposited on the substrate by independently varying an amplitude of negative pulses in each of the first and second DC voltage pulse signals.

6. The system of claim 2, wherein the controller varies a composition ratio of the first and second components of the alloy deposited on the substrate by varying an amplitude of the at least one ion current during pulses in each of the first and second DC voltage pulse signals.

7. The system of claim 2, wherein the controller varies the composition ratio over time such that the composition ratio of the alloy deposited on the substrate varies throughout a thickness of a film deposited on the substrate.

8. The system of claim 7, wherein the composition ratio of the alloy deposited on the substrate varies linearly throughout the thickness of the film deposited on the substrate.

9. The system of claim 7, wherein the composition ratio of the alloy deposited on the substrate varies in a sinusoidal fashion throughout the thickness of the film deposited on the substrate.

10. The system of claim 7, wherein the composition ratio of the alloy deposited on the substrate varies in a parabolic fashion throughout the thickness of the film deposited on the substrate.

11. The system of claim 7, wherein the composition ratio of the alloy deposited on the substrate varies as a step function within the thickness of the film deposited on the substrate.

12. The system of claim 1, wherein material from the first target deposited on the substrate corresponds to a first component of a compound, and material from the second target deposited on the substrate corresponds to a second component of the compound.

13. The system of claim 12, wherein the controller varies a composition ratio of the first and second components of the compound deposited on the substrate by independently varying a number of negative pulses per unit time in each of the first and second DC voltage pulse signals.

14. The system of claim 12, wherein the controller varies a composition ratio of the first and second components of the compound deposited on the substrate by independently varying a length of negative pulses per unit time in each of the first and second DC voltage pulse signals.

15. The system of claim 12, wherein the controller varies a composition ratio of the first and second components of the compound deposited on the substrate by independently varying an amplitude of negative pulses in each of the first and second DC voltage pulse signals.

16. The system of claim 12, wherein the controller varies a composition ratio of the first and second components of the compound deposited on the substrate by varying an amplitude of the at least one ion current during pulses in each of the first and second DC voltage pulse signals.

17. The system of claim 12, wherein the controller varies the composition ratio over time such that the composition ratio of the compound deposited on the substrate varies throughout a thickness of a film deposited on the substrate.

18. The system of claim 17, wherein the composition ratio of the compound deposited on the substrate varies linearly throughout the thickness of the film deposited on the substrate.

19. The system of claim 17, wherein the composition ratio of the compound deposited on the substrate varies in a sinusoidal fashion throughout the thickness of the film deposited on the substrate.

20. The system of claim 17, wherein the composition ratio of the compound deposited on the substrate varies in a parabolic fashion throughout the thickness of the film deposited on the substrate.

21. The system of claim 17, wherein the composition ratio of the compound deposited on the substrate varies as a step function within the thickness of the film deposited on the substrate.

22. The system of claim 1, wherein the controller applies the first and second DC voltage pulse signals to the first and second targets, respectively, in a manner that avoids a simultaneous positive biasing of the first and second targets.

23. The system of claim 1, wherein the first and second DC voltage pulse signals correspond to first and second bi-polar DC voltage pulse signals, respectively.

24. The system of claim 23, wherein the biasing circuitry is formed from at least one positive voltage source with respect to ground, at least one negative voltage source with respect to ground, a first high frequency switch used to form the first bi-polar DC voltage pulse signal, and a second high frequency switch used to form the second bi-polar DC voltage pulse signal.

25. The system of claim 1, wherein the at least one ion source, the at least one electron source and the first and second targets are disposed in a chamber having a pressure between 10⁻

2 to 10<sup>−

5</sup> torr during operation of the system.

26. The system of claim 1, wherein the controller varies the first DC voltage pulse signal used to bias the first target independently from the ion and electron currents.

27. The system of claim 26, wherein the controller varies the second DC voltage pulse signal used to bias the second target independently from the ion and electron currents.

28. The system of claim 1, wherein the first DC voltage pulse signal is an a-symmetric bipolar DC voltage pulse signal.

29. The system of claim 28, wherein the second DC voltage pulse signal is an a-symmetric bi-polar DC voltage pulse signal.

30. The system of claim 1, wherein a face of the first target is outside of a line-of-sight of a face of the second target, and the face of the second target is outside of a line-of-sight of the face of the first target.

31. The system of claim 30, where the first and second targets have faces that lie in a common plane.

32. The system of claim 30, where the first and second targets have faces that lie in different planes.

33. The system of claim 30, further comprising a shield positioned between the first and second targets, wherein the shield prevents cross-contamination between the first and second targets.

34. The system of claim 1, wherein the at least one ion source comprises a first ion source that generates a first ion current directed at the first target and a second ion source that generates a second ion current directed at the second target;

wherein the at least one electron source comprises a first electron source that generates a first electron current directed at the first target and a second electron source that generates a second electron current directed at the second target;

wherein the controller varies the first ion current independently from the first electron current, and the controller varies the second ion current independently from the second electron current.

35. A method for performing sputter deposition, comprising the steps of:

(a) generating an ion current directed at at least first and second targets with at least one ion source;

(b) generating an electron current directed at the at least first and second targets with at least one electron source;

(c) biasing the first target with a first DC voltage pulse signal and biasing the second target with a second DC voltage pulse signal that is independent of the first DC voltage pulse signal;

(d) monitoring, with a first current sensor, a positive current and a negative current from the first target during one or more cycles of the first DC voltage pulse signal;

(e) monitoring, with a second current sensor, a positive current and a negative current from the second target during one or more cycles of the second DC voltage pulse signal;

(f) varying, in response at least in part on outputs of the first and second current sensors, the ion current independently from the electron current;

wherein the at least one ion source and the at least one electron source create a continuous plasma proximate the first and second targets, and the biasing causes the first and second targets to alternately attract ions and electrons from the plasma;

wherein the ions attracted from the plasma sputter the first and second targets and material from the first and second targets is deposited on a substrate; and

wherein the electrons attracted from the plasma neutralize accumulated charge on the first and second targets.