Use of ultra-high magnetic fields in resputter and plasma etching

• US 7,897,516 B1
• Filed: 05/24/2007
• Issued: 03/01/2011
• Est. Priority Date: 05/24/2007
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Inventors: Kinder, Ronald L., Pradhan, Anshu A.
• Primary Examiner(s): Alanko; Anita K
• Assistant Examiner(s): REMAVEGE, CHRISTOPHER
• Application Number:
  US11/807,183
• Time in Patent Office: 1,377 Days
• Field of Search: 438/710
• US Class Current: 438/695
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/3402 using supplementary magnetic fields
• CPC Class Codes: H01L 21/2855 by physical means, e.g. sputtering, evaporation H01L21/28518 - H01L21/28537 and H01L21/28568 take precedence
• CPC Class Codes: H01L 21/32131 by physical means only
• CPC Class Codes: H01L 21/76805 the opening being a via or contact hole penetrating the underlying conductor
• CPC Class Codes: H01L 21/76844 Bottomless liners
• CPC Class Codes: H01L 21/76865 Selective removal of parts of the layer H01L21/76844 takes precedence
• CPC Class Codes: H01L 21/76873 for electroplating

Abstract

Methods for resputtering and plasma etching include an operation of generating an ultra-high density plasma using an ultra-high magnetic field. For example, a plasma density of at least about 10¹³ electrons/cm³ is achieved by confining a plasma using a magnetic field of at least about 1 Tesla. The ultra-high density plasma is used to create a high flux of low energy ions at the wafer surface. The formed high density low energy plasma can be used to sputter etch a diffusion barrier or a seed layer material in the presence of an exposed low-k dielectric layer. For example, a diffusion barrier material can be etched with a high etch rate to deposition rate (E/D) ratio (e.g., with E/D>2) without substantially damaging an exposed dielectric layer. Resputtering and plasma etching can be performed, for example, in iPVD and in plasma pre-clean tools, equipped with magnets configured for confining a plasma.

Claims

1. A method of removing material on a semiconductor wafer having a recessed feature, the method comprising:

(a) receiving the semiconductor wafer, wherein the semiconductor wafer has a layer of material coating at least a bottom portion of the recessed feature;

(b) generating an ultra-high density plasma comprising inert gas ions, the plasma having a plasma density of at least about 10¹³ electrons/cm³, the ions having a mean ion energy of less than about 250 eV at a wafer surface; and

(c) removing at least a portion of the material by impinging on the layer of material with ions generated in (b) by etching the material while simultaneously depositing the material with an etch rate to deposition rate ratio (E/D) of at least about 2 at least at one location on the wafer.

2. The method of claim 1, wherein the ultra-high density plasma further comprises metal ions.

3. The method of claim 1, wherein the ultra-high density plasma does not comprise metal ions.

4. The method of claim 1, wherein operations (a), (b), and (c) are performed in a pre-clean chamber.

5. The method of claim 1, wherein (c) comprises resputtering the layer of material.

6. The method of claim 1, wherein the layer of material comprises a barrier layer material.

7. The method of claim 6, wherein the barrier layer material is selected from the group consisting of Ta, TaN_x, Ti, TiN_x, W, WN_x, Ru, and Co.

8. The method of claim 1, wherein the layer of material comprises a metal seed layer material.

9. The method of claim 8, wherein the seed layer material comprises copper or a copper alloy.

10. The method of claim 1, wherein the wafer comprises portions of dielectric coated with a diffusion barrier layer and/or a seed layer during (a), wherein the dielectric is exposed to inert gas ions during (c), and wherein (c) comprises removing at least a portion of the barrier layer and/or the seed layer material, without substantially damaging the exposed dielectric.

11. The method of claim 10, wherein the exposed dielectric has a dielectric constant of less than about 3.5.

12. The method of claim 10, wherein the dielectric is selected from the group consisting of a carbon-doped silicon dioxide, a fluorine-doped silicon dioxide, and an organic-containing low-k dielectric material.

13. The method of claim 10, wherein the dielectric is a porous dielectric.

14. The method of claim 1, further comprising, prior to (a), depositing the layer of material by a method selected from the group consisting of PVD, CVD, ALD, electroplating, and electroless deposition.

15. The method of claim 14, wherein depositing the layer of material and removing the portion of material are performed in one process chamber.

16. The method of claim 15, wherein the process chamber comprises an HCM.

17. The method of claim 15, wherein the process chamber comprises a planar magnetron.

18. The method of claim 1, wherein (c) is performed without making use of an inductively coupled plasma.

19. The method of claim 1, wherein during (c), the inert gas at the wafer surface is ionized to at least about 5%.

20. The method of claim 1, wherein the inert gas at the wafer surface is ionized to at least about 20%.

21. The method of claim 1, wherein generating the ultra-high density plasma comprises generating a magnetic field of at least about 1 Tesla in a volume of less than about 0.5 m³, wherein the volume comprises an inert gas.

22. The method of claim 1, wherein the ultra-high density plasma does not contact the wafer.

23. A method of depositing material on a semiconductor wafer having a recessed feature, the method comprising:

(a) depositing a layer of the material on the wafer to coat at least the bottom portion of the recessed feature;

(b) generating an ultra-high density plasma comprising inert gas ions, the plasma having a plasma density of at least about 10¹³ electrons/cm³,

(c) removing at least a portion of the material by impinging on the layer of material with ions, wherein the ion flux at a wafer surface is greater than about 5·

10¹⁵ ions/cm² s¹ of the exposed surface area of the wafer, wherein a mean ion energy is less than about 250 eV at the exposed surface area of the wafer, and wherein removing at least a portion of the material comprises etching the material while simultaneously depositing the material with an etch rate to deposition rate ratio (E/D) of at least about 2 at least at one location on the wafer.

24. A method of resputtering a metal-containing material on a semiconductor wafer having a layer of low-k dielectric, the method comprising:

simultaneously etching and depositing the metal-containing material on the wafer by contacting a wafer surface with inert gas ions and neutral metal atoms and/or ionized metal atoms generated from an ultra-high density plasma having a plasma density of at least about 10¹³ electrons/cm³, such that an etch rate to deposition rate (E/D) ratio at least at one location on the wafer is at least about 2, and wherein simultaneously etching and depositing comprises contacting the low-k dielectric with the inert gas ions and neutral metal atoms and/or ionized metal atoms without causing substantial damage to the low-k dielectric.

25. A method of resputtering a material on an electrically biased semiconductor wafer, the method comprising:

simultaneously etching and depositing the material on the wafer by contacting a wafer surface with inert gas ions and neutral metal atoms and/or ionized metal atoms generated from an ultra-high density plasma having a plasma density of at least about 10¹³ electrons/cm³, such that an etch rate to deposition rate (E/D) ratio at least at one location on the wafer is at least about 2, wherein a bias power at the wafer does not exceed 1000 W, and wherein a mean ion energy is less than about 250 eV at the wafer surface.