Integration of ferromagnetic films with ultrathin insulating film using atomic layer deposition

• US 6,617,173 B1
• Filed: 10/10/2001
• Issued: 09/09/2003
• Est. Priority Date: 10/11/2000
• Status: Expired due to Fees

• Current Assignee: Aixtron Inc. (Aixtron AG)
• Original Assignee: Genus PLC
• Inventors: Sneh, Ofer
• Primary Examiner(s): Thompson, Craig
• Application Number:
  US09/974,076
• Time in Patent Office: 699 Days
• Field of Search: 438/3, 438/197-200, 438/585-596, 438/759, 438/800, 257/295
• US Class Current: 438/3
• CPC Class Codes: H01L 21/02178 the material containing aluminium, e.g. Al2O3
• CPC Class Codes: H01L 21/0228 deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/3141 Deposition using atomic layer deposition techniques [ALD]
• CPC Class Codes: H01L 21/3143 composed of alternated layers or of mixtures of nitrides and oxides or of oxinitrides, e.g. formation of oxinitride by oxidation of nitride layers
• CPC Class Codes: H01L 21/31616 Deposition of Al2O3
• CPC Class Codes: H01L 21/318 composed of nitrides
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10N 50/01 Manufacture or treatment

Abstract

A technique to form an ultrathin dielectric layer over a ferromagnetic layer by atomic layer deposition.

Claims

1. A method comprising:

depositing a first ferromagnetic layer onto an underlying material;

depositing a protective sacrificial layer above the first ferromagnetic layer without exposing the first ferromagnetic layer to ambient environment, the protective sacrificial layer being removal selective over the first ferromagnetic layer;

exposing the protective sacrificial layer to an oxidizing ambient to undergo photolithographic and material removal processes that form a defined stacked structure by pattern delineating the first ferromagnetic layer;

placing the material into a vacuum environment prior to removing the protective sacrificial layer;

removing the protective sacrificial layer by a selective process to expose the first ferromagnetic layer under vacuum; and

depositing a dielectric layer over the first ferromagnetic layer by atomic layer deposition in the vacuum environment.

2. The method of claim 1 further comprising depositing a second ferromagnetic layer above the deposited dielectric layer.

3. The method of claim 1 further comprising depositing a second protective sacrificial layer above the dielectric layer by atomic layer deposition without exposing the dielectric layer to the ambient environment, patterning the dielectric layer in an oxidizing ambient, and placing the material into a non-ambient environment to remove the second protective sacrificial layer and to deposit a second ferromagnetic layer above the dielectric layer.

4. The method of claim 2 further comprising forming ferromagnetic-dielectric-ferromagnetic tunneling junctions on the material by forming the first ferromagnetic, dielectric and second ferromagnetic layers.

5. The method of claim 1 wherein said depositing of the dielectric layer deposits the dielectric layer to a thickness in an approximate range of 5-20 Angstroms.

6. The method of claim 1 wherein said removing the protective sacrificial layer includes removing by isotropic dry etch.

7. The method of claim 1 wherein said removing the protective sacrificial layer includes removing by isotropic dry etch using fluorine chemistry.

8. The method of claim 1 wherein said depositing the dielectric layer includes depositing Al₂O₃.

9. The method of claim 1 wherein said depositing the dielectric layer includes depositing AIN.

10. The method of claim 1 further comprising activating a surface of the first ferromagnetic layer to enhance surface activation to perform atomic layer deposition prior to depositing the dielectric layer.

11. A method of fabricating a ferromagnetic-dielectric-ferromagnetic tunneling device comprising:

depositing a first ferromagnetic layer onto a substrate;

depositing a protective sacrificial layer above the first ferromagnetic layer without exposing the first ferromagnetic layer to ambient environment, the protective sacrificial layer being etch selective over the first ferromagnetic layer;

patterning the first ferromagnetic layer and the overlying protective sacrificial layer to form a patterned stack in an oxidizing ambient;

placing the substrate into an atomic layer deposition chamber;

removing the protective sacrificial layer in the atomic layer deposition environment to expose the first ferromagnetic layer;

depositing a dielectric layer over the first ferromagnetic layer by atomic layer deposition; and

depositing a second ferromagnetic layer over the dielectric layer.

14. The method of claim 14 wherein said depositing the protective sacrificial layer includes depositing W or WNx.

12. The method of claim 14 wherein said removing the protective sacrificial layer includes removing by isotropic dry etch.

13. The method of claim 14 wherein said removing the protective sacrificial layer includes removing by isotropic dry etch using fluorine chemistry.

15. The method of claim 14 wherein said depositing the protective sacrificial layer includes depositing Si or SiNx.

16. The method of claim 14 wherein said depositing the dielectric layer includes depositing Al₂O₃.

17. The method of claim 14 wherein said depositing the dielectric layer includes depositing AlN.

18. The method of claim 14 wherein said depositing of the dielectric layer deposits the dielectric layer to a thickness in an approximate range of 5-20 Angstroms.

19. The method of claim 14 further comprising depositing a second protective sacrificial layer above the dielectric layer by atomic layer deposition without exposing the dielectric layer to the ambient environment, patterning the dielectric layer in an oxidizing environment, and removing the second protective sacrificial layer before deposition of the second ferromagnetic layer without exposing the underlying dielectric layer to the ambient environment to deposit the second ferromagnetic layer.

20. The method of claim 14 further comprising activating a surface of the first ferromagnetic layer to enhance surface activation to perform atomic layer deposition of the dielectric layer.

21. The method of claim 23 wherein said activating further includes activating by exposure to NH₃/H₂ plasma to remove surface fluorine and facilitate NH_x, species termination.