Adsorption based material removal process

• US 8,043,972 B1
• Filed: 07/16/2008
• Issued: 10/25/2011
• Est. Priority Date: 06/30/2006
• Status: Expired due to Fees

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Ashtiani, Kaihan A., Liu, Xinye, Collins, Joshua
• Primary Examiner(s): Vinh; Lan
• Application Number:
  US12/174,402
• Time in Patent Office: 1,196 Days
• Field of Search: 438/706, 438/714, 438/723, 438/724, 438/745, 438/743, 438/756, 438/710, 216/58, 216/80
• US Class Current: 438/723
• CPC Class Codes: H01L 21/02063 the processing being the formation of vias or contact holes
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/6708 using mainly spraying means, e.g. nozzles

Abstract

Methods for accurate and conformal removal of atomic layers of materials make use of the self-limiting nature of adsorption of at least one reactant on the substrate surface. In certain embodiments, a first reactant is introduced to the substrate in step (a) and is adsorbed on the substrate surface until the surface is partially or fully saturated. A second reactant is then added in step (b), reacting with the adsorbed layer of the first reactant to form an etchant. The amount of an etchant, and, consequently, the amount of etched material is limited by the amount of adsorbed first reactant. By repeating steps (a) and (b), controlled atomic-scale etching of material is achieved. These methods may be used in interconnect pre-clean applications, gate dielectric processing, manufacturing of memory devices, or any other applications where removal of one or multiple atomic layers of material is desired.

Claims

1. A method of removing a layer of oxide from a substrate surface, the method comprising:

(a) exposing a surface of the layer of oxide to ammonia and allowing ammonia to deposit on the layer of oxide until the surface of the layer is partially or fully saturated with ammonia, wherein ammonia does not etch the material onto which it is deposited;

(b) exposing the substrate to dry hydrogen fluoride, whereby dry hydrogen fluoride and ammonia combine to produce a fluoride etchant in an amount limited by the amount of adsorbed ammonia in (a), wherein the dry hydrogen fluoride is not capable of etching the layer of oxide and the formed fluoride etchant is capable of etching the layer of oxide;

(c) repeating (a) and (b) until a layer of the fluoride etchant is formed in an amount sufficient to etch the underlying oxide by a specified thickness; and

(d) applying energy to the substrate to drive off one or more etching by-products of an etching reaction between the fluoride etchant and the oxide.

2. The method of claim 1, wherein the fluoride etchant deposited during a single cycle of operation (a) and operation (b) removes a layer of silicon oxide having a thickness of about 1 Å

to 7 Å

.

3. The method of claim 1, wherein the layer of fluoride etchant etches the oxide to a depth of up to about 160 Angstroms.

4. The method of claim 1, wherein the layer of fluoride etches the oxide to a depth of at most about 50 angstroms.

5. The method of claim 1, wherein the layer of fluoride etches the oxide to a depth of at most about 20 angstroms.

6. The method of claim 1, wherein the oxide etched by the layer of fluoride exists on one or more of a silicon contact, an active silicon contact, a silicide contact, a polysilicon contact, an active germanium contact, an active silicon-germanium contact, a germanium contact, and a silicon-germanium contact.

7. The method of claim 1, wherein the substrate is maintained at the temperature of not greater than about 70°

C. during operations (a) through (c).

8. The method of claim 1, wherein at least operations (a) through (c) are performed under a pressure of between about 5 milliTorr and 10 Torr.

9. The method of claim 1, wherein at least one of the dry hydrogen fluoride and ammonia is generated from an indirect source.

10. The method of claim 1, further comprising generating the dry HF from hydrogen and NF₃ or a perfluorocarbon.

11. The method of claim 1, further comprising generating the NH₃ from H₂ and N₂ gases.

12. The method of claim 1, wherein the dry HF and the NH₃ are generated with the assistance of a plasma source, an optical source, or a catalyst.

13. The method of claim 1, wherein the substrate is a partially manufactured integrated circuit.

14. The method of claim 13, wherein the layer of oxide comprises oxide on a contact or metal line within a contact hole or via of the partially manufactured integrated circuit.

15. The method of claim 1, wherein (a) comprises exposing a surface of the layer of oxide to ammonia and allowing the dry hydrogen fluoride to deposit on the surface of the layer to a thickness of no more than about 100 Angstroms.

16. The method of claim 1, further comprising:

after applying energy to the substrate to drive off one or more byproducts produced during an etch operation, repeating operations (a), (b), (c), and (d) at least once to remove a desired amount of material.

17. The method of claim 1, wherein the method comprises forming a solid reaction by-product, said by-product being removed in (d) by sublimation.

18. The method of claim 17, wherein the solid reaction by-product comprises ammonium hexafluoro silicate.

19. The method of claim 1, wherein the fluoride etchant is selected from the group consisting of ammonium fluoride, ammonium bifluoride and mixtures thereof.

20. The method of claim 1, wherein the method comprises removing less than about 160 Å

of oxide in the presence of a bulk amount of the oxide.

21. The method of claim 1, wherein exposing the substrate to dry hydrogen fluoride comprises flowing dry gaseous hydrogen fluoride into a process chamber.

22. The method of claim 1, wherein operations (a) through (d) are performed in one chamber having one station.

23. The method of claim 1, wherein operations (a) through (c) are performed in one chamber and operation (d) is performed in a second chamber.

24. The method of claim 1, wherein at least operations (a) through (c) are performed in a batch process chamber.

25. The method of claim 1, wherein operations (a) through (d) are performed in one chamber having multiple stations.

26. The method of claim 1, wherein operations (a) and (b) are performed in one or more stations at a wafer temperature of not greater than about 70°

C., and wherein operation (d) is performed at one or more different stations from the stations used to perform operations (a) and (b), and wherein the one or more stations used to perform operation (d) heat the wafer to a temperature of at least about 50°

C.

27. The method of claim 1 further comprising purging or evacuating a chamber housing the substrate after exposing the substrate to ammonia and before exposing the substrate to dry hydrogen fluoride.

28. The method of claim 1, wherein the layer of oxide comprises a material selected from the group consisting of silicon oxide, carbon-doped silicon oxide, and fluorine-doped silicon oxide.

29. A method of removing a layer of oxide from a substrate surface, the method comprising:

(a) exposing a surface of the layer of oxide to ammonia and allowing ammonia to deposit on the layer of oxide until the surface of the layer is partially or fully saturated with ammonia, wherein ammonia does not etch the material onto which it is deposited;

(b) exposing the substrate to dry hydrogen fluoride, whereby dry hydrogen fluoride and ammonia combine to produce a fluoride etchant in an amount limited by the amount of adsorbed ammonia in (a), wherein the dry hydrogen fluoride is not capable of etching the layer of oxide and the formed fluoride etchant is capable of etching the layer of oxide;

(c) allowing the fluoride etchant formed in (b) etch the layer of oxide and form a solid ammonium hexafluorosilicate by-product; and

(d) removing the solid ammonium hexafluorosilicate by sublimation.