High density plasma deposition and etching apparatus

• US 5,122,251 A
• Filed: 02/04/1991
• Issued: 06/16/1992
• Est. Priority Date: 06/13/1989
• Status: Expired due to Term

• Current Assignee: SPTS Technologies Limited (KLA Corporation)
• Original Assignee: Plasma & Materials Technologies, Inc.
• Inventors: deChambrier, Alexis P., Pearson, David C., Shoji, Tatsuo, Conn, Robert W., Campbell, Gregor A.
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US07/650,788
• Time in Patent Office: 498 Days
• Field of Search: 204/298.06, 204/298.07, 204/298.16, 204/298.31, 204/298.33, 204/298.34, 204/298.37, 156/345, 118/723, 315/111.41, 422/186.05
• US Class Current: 204/298.06
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/3211 Antennas, e.g. particular shapes of coils
• CPC Class Codes: H01J 37/3222 Antennas
• CPC Class Codes: H01J 37/3266 Magnetic control means
• CPC Class Codes: H01J 37/32688 Multi-cusp fields
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

A high density ionized plasma is generated in a source chamber using a single loop disposed in a plane that intercepts the central axis of the source chamber perpendicularly or at a lesser angle and spaced from the closed end of the chamber. With a longitudinal magnetic field and an inert or reactive gas injected into the source chamber, excitation of the antenna with RF energy in the 5 to 30 MHz establishes the M=0 excitation mode or components of both the M=0 and M=1 modes. Low frequency whistler waves are created which generate a uniform and high density plasma and high plasma current. The plasma source thus defined is used in combination with process chamber configurations in which static shaped or time modulated magnetic fields enhance the distribution and uniformity of the plasma at a substrate to be etched, deposited or sputtered.

Claims

1. A system for generating a high density plasma comprising:

a plasma confinement chamber of cylindrical form;

means for injecting a gas to be ionized into the chamber;

antenna means comprising a single loop element encompassing the cylindrical chamber, the loop element being disposed in a plane at an angle of in excess of 45°

to the central axis of the chamber, and positioned in an intermediate region along the length of the chamber;

means disposed adjacent the chamber and the antenna means for generating a longitudinal magnetic field in the chamber; and

means coupled to the antenna means for exciting the loop element with radio frequency energy.

2. A system as set forth in claim 1 above, wherein the magnetic field is less than 1000 gauss, the plasma density is in excess of 10¹³ /cm³, and the loop element is at an angle of about 90°

relative to the magnetic field.

3. A system as set forth in claim 2 above, wherein the system has a first plasma current and density peak in the range of about 50 gauss and a second plasma and density peak in the range of about 400 gauss.

4. A system as set forth in claim 3 above, wherein the radio frequency energy is in the range of 13.56 MHz and the means for exciting further includes impedance matching means.

5. A system as set forth in claim 1 above, wherein the mode structure of the wave electric field imparted by the loop element is the m-0 node and has a pitch of 2π

/k_z, where k_z is determined by the dispersion relation, [ω

/ω

_c -ω

_p² /C² k_z² ]² =1+(3.83 k_z a)² and a phase velocity of ω

/k_z, where ω

is the frequency of excitation, ω

_c is the electron cyclotron angular frequency, ω

_p is the plasma frequency, k_z is the axial wave number in the plasma and a is the plasma radius.

6. A system as set forth in claim 5 above, wherein the plasma is excited with low frequency whistler waves having the relation Ω

_c <

ω

<

ω

_c, wherein Ω

_c is the ion cyclotron frequency.

7. A system as set forth in claim 6 above, wherein the plasma density is in excess of 10¹³ /cm³, and the chamber is a non-magnetic insulating chamber.

8. A system as set forth in claim 1 above, wherein the cylindrical chamber includes an exit aperture along the longitudinal axis, and the system further includes a process chamber adjacent the cylindrical chamber and in communication with the cylindrical chamber via the exit aperture and means for supporting an element to be processed therein, and wherein the process chamber has a greater cross-sectional area than cylindrical chamber.

9. A system as set forth in claim 8 above, wherein the process chamber includes means for maintaining a plasma therein.

10. A system as set forth in claim 9 above, wherein the means for maintaining a plasma comprises magnetic means about the process chamber for defining a magnetic bucket chamber.

11. A system as set forth in claim 10 above, wherein the magnetic bucket chamber is rectangular in plan and wherein the system comprises at least two plasma confinement chambers having associated single loop antenna elements thereabout, and disposed along the magnetic bucket chamber.

12. A system as set forth in claim 8 above, wherein the system comprises at least two plasma confinement chambers, each having an associated single loop antenna thereabout, and circuit means coupling the antennas in series for exciting the antennas with radio frequency energy.

13. A system as set forth in claim 8 above, wherein the system further comprises means for maintaining a substrate to be processed in the path of the plasma in the process chamber.

14. A system as set forth in claim 13 above, wherein the system further includes means for maintaining a magnetic cusp field in the region of the substrate, the magnetic cusp field opposing the longitudinal magnetic field in the chamber.

15. A system as set forth in claim 14 above, wherein the means for maintaining a magnetic cusp field comprises means for varying the intensity of the magnetic cusp field to time average the plasma flux density at the substrate.

16. A system as set forth in claim 8 above, wherein the system comprises a sputter target and a sputter target holder in the process chamber in the path of the plasma, means for biasing the sputter target holder, and substrate means about the plasma path between the cylindrical chamber and the sputter target, in the path of material sputtered therefrom.

17. A plasma processing apparatus for processing a substrate, comprising:

(a) an antenna radiating electromagnetic waves in the RF range of frequencies, consisting of single current loop located outside but surrounding closely a plasma generating chamber;

(b) a cylindrical plasma generation chamber, the plasma generation chamber being proximate to and in electromagnetic communication with the antenna, such that the longitudinal axis of the cylindrical plasma generation chamber and the plane of the current loop are either perpendicular or at an angle less than 90°

;

(c) a first fluid injector, the first fluid injector introducing a fluid into the plasma generation chamber, thereby permitting the creation of a plasma within the plasma generation chamber;

(d) a magnetic field generator, the magnetic field generator generating a magnetic field substantially parallel to the longitudinal axis of the plasma generation chamber;

(e) a process chamber, the plasma being transported to the process chamber by the magnetic field;

(f) a second fluid injector, the second fluid injector introducing a fluid into the process chamber;

(g) a current controller, the current controller controlling the current within the magnetic field generator, thereby controlling plasma shape;

(h) a substrate holder, the substrate holder residing within the process chamber; and

(i) a substrate, the substrate being mounted on the substrate holder, the substrate thereby being subjected to the plasma.

18. An apparatus as set forth in claim 17 above, further including:

(j) an auxiliary radio frequency generator for applying radio frequency power to a substrate residing on the substrate holder;

(k) a radio frequency exciter, the radio frequency exciter generating a radio frequency voltage and current; and

(l) a matching network, the matching network interconnecting the radio frequency exciter and the antenna, thereby promoting the efficient transfer of radio frequency energy from the radio frequency exciter to the antenna.

19. The plasma processing apparatus of claim 17, wherein the substrate holder is supported within the process chamber in a state of substantial electrical insulation.

24. The plasma processing apparatus of claim 17, further comprising a plurality of magnets, the magnets being arranged in a circumferential manner proximate to the process chamber, succeeding magnets having opposite orientations of north and south poles.

25. The plasma processing apparatus of claim 24, wherein the process chamber has a cross sectional area that is larger than a cross section of the plasma generation chamber.

26. The plasma processing apparatus of claim 25, wherein the process chamber is formed substantially of stainless steel.

27. The plasma process apparatus of claim 26, wherein the cross section of the process chamber is a regular geometric shape.

28. The plasma processing apparatus of claim 24, further comprising an additional magnetic field generator, said generator being located behind the substrate holder on the side of the substrate that is opposite to that of the plasma generating chamber and being located in a plane substantially parallel to that of the other magnetic field generator, and which generates a magnetic field opposed to that of the other magnetic field generator.

29. The plasma processing apparatus of claim 28 in which the magnetic field generator located behind the substrate holder generates a time-varying magnetic field.

30. The plasma processing apparatus of claim 17, further comprising an additional magnetic field generator, said generator being located behind the substrate holder on the side of the substrate that is opposite to that of the plasma generating chamber and being located in a plane substantially parallel to that of the other magnetic field generator, and which generates a magnetic field opposed to that of the other magnetic field generator.

31. The plasma processing apparatus of claim 30 in which the magnetic field generator located behind the substrate holder generates a time-varying magnetic field.

32. A plasma processing apparatus according to claim 17 for sputter deposition, comprising:

(a) at least one target;

(b) biasing means, the biasing means applying a voltage to the target, thereby causing ions of the plasma to bombard the target and causing material from the target to be deposited on the substrate.

33. The plasma processing apparatus of claim 17, further comprising:

(a) a plurality of plasma generation chambers, each plasma generation chamber being cooperatively connected to the processing chamber;

(b) a plurality of antennas, each antenna being electromagnetically coupled to each plasma generation chamber; and

(c) a plurality of magnetic field generators, each magnetic field generator being magnetically coupled to each plasma generation chamber.

34. The plasma processing apparatus of claim 17, further comprising:

(a) a plurality of plasma generation chambers, each plasma generation chamber being cooperatively connected to the process chamber, each plasma generation chamber being coaxial to the longitudinal axis of the plasma generator chamber;

(b) a plurality of antennas, each antenna being electromagnetically coupled to a respective plasma generation chamber;

(c) a plurality of magnetic field coils, the magnetic field coil being proximate to the process chamber;

(d) a plurality of magnetic field generators, each magnetic field generator being magnetically coupled to each plasma generator; and

(e) a plurality of substrate holders mounted within the process chamber.

20. The plasma processing apparatus of claim 20, wherein the substrate holder comprises:

(a) a copper block and

(b) thermal control means, permitting temperature regulation of the copper block.

21. The plasma processing apparatus of claim 20, wherein the second fluid injector is formed as a porous element, thereby permitting a gas to be introduced within the element, the gas escaping from the element into the process chamber.

22. The plasma processing apparatus of claim 21, wherein the porous element is formed as a ring, the ring being constructed of tubing, the tubing being perforated so as to permit the gas to escape from the ring into the process chamber.

23. The plasma processing apparatus of claim 22, wherein the plasma generation chamber is a quartz cylinder.