Method of etching magnetic materials

• US 20040026369A1
• Filed: 08/12/2002
• Published: 02/12/2004
• Est. Priority Date: 08/12/2002
• Status: Abandoned Application

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Kumar, Ajay, Chen, Xiaoyi, Nallan, Padmapani C., Ying, Chentsau
• Application Number:
  US10/218,244
• Publication Number:
  US 20040026369A1
• Time in Patent Office: Days
• US Class Current: 216/63
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C23F 4/00 Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
• CPC Class Codes: H01F 41/308 lift-off processes, e.g. ion milling, for trimming or patterning
• CPC Class Codes: H10N 50/01 Manufacture or treatment

Abstract

A method of etching a layer of magnetic material using a hard mask and an etchant comprising BCl₃. The method finds use in etching magnetic materials during fabrication of magneto-resistive random access memory (MRAM) devices.

Claims

1. A method of etching a film stack comprising a layer of magnetic material, said method comprising:

(a) forming a hard mask upon the film stack; and

(b) etching the layer of magnetic material using a plasma comprising BCl₃.

2. The method of claim 1 wherein:

the magnetic material comprises at least one of NiFe, Ru, CoFe, PtMn, NiFe, or NiFeCr.

3. The method of claim 1 wherein the layer of magnetic material is a free magnetic layer of an magneto-resistive random access memory (MRAM) film stack.

4. The method of claim 1 wherein step (b) comprises:

supplying 5 to 25 sccm of BCl₃ and 20 to 100 sccm of Ar, maintaining a gas pressure between 5 and 40 mTorr, applying a bias power to a cathode electrode of between 0 and 300 Watt, applying power to an inductively coupled antenna of between 200 and 3000 Watt, and maintaining the substrate at a temperature of between 15 and 80 degrees Celsius.

5. The method of claim 1 wherein step (b) comprises:

supplying 20 sccm of BCl₃ and 80 sccm of Ar, maintaining a gas pressure at 5 mTorr, applying a bias power to a cathode electrode about 150 Watt, applying power to an inductively coupled antenna about 700 Watt, and maintaining the substrate at a temperature about 80 degrees Celsius.

6. A method of fabricating a magneto-resistive random access memory device from a film stack comprising a top electrode, a free magnetic layer, a tunnel layer, a magnetic film stack, and a bottom electrode, that are formed on a semiconductor substrate, comprising:

(a) forming a first sacrificial hard mask;

(b) etching the top electrode wherein said etching of the top electrode produces a first residue;

(c) etching the free magnetic layer;

(d) removing a first residue and a first sacrificial hard mask;

(e) forming a second sacrificial hard mask on the top electrode;

(f) etching the tunnel layer and the magnetic film stack;

(g) etching the bottom electrode layer; and

(h) removing a second residue.

7. The method of claim 6 wherein:

the first and the second sacrificial hard masks comprise SiO₂;

the top electrode comprises at least one of Ta or TaN;

the free magnetic layer comprises at least one of NiFe or CoFe;

the tunnel layer comprises Al₂O₃;

the magnetic film stack comprises at least one of NiFe, Ru, CoFe, PtMn, NiFe, NiFeCr; and

the bottom electrode comprises at least one of Ta or TaN.

8. The method of claim 6 wherein step (a) further comprises:

(a1) depositing a layer of material that is used to form the first sacrificial hard mask on the top electrode;

(a2) forming a photoresist etch mask defining the first sacrificial hard mask; and

(a3) forming the first sacrificial hard mask.

9. The method of claim 8 wherein the photoresist etch mask comprises a layer of anti-reflective coating.

10. The method of claim 8 wherein step (a3) and step (b) are performed sequentially in the same reactor.

11. The method of claim 8 wherein step (a3) is performed using the same etching chemistry as step (b).

12. The method of claim 6 wherein step (b) uses a plasma comprising CF₄, CHF₃, and Ar.

13. The method of claim 6 wherein step (b) comprises:

supplying about 40 to 80 sccm of CF₄, 10 to 30 sccm of CHF₃, and 40 to 80 sccm of Ar, maintaining in a reaction chamber a gas pressure at about 5 to 40 mTorr, applying a bias power to a cathode electrode of about 0 to 300 Watt, applying power to an inductively coupled antenna of about 200 to 3000 Watt, and maintaining the substrate at a temperature of about 15 to 80 degrees Celsius.

14. The method of claim 6 wherein step (b) further comprises a step of:

stripping an etch mask.

15. The method of claim 14 wherein the stripping step is performed after forming the first sacrificial hard mask and etching the top electrode.

16. The method of claim 14 wherein the stripping step uses a plasma comprising O₂.

17. The method of claim 6 wherein step (c) further comprises:

(c1) etching the free magnetic layer in a plasma comprising an oxygen and chlorine.

18. The method of claim 17 wherein step (c1) uses the plasma comprising Cl₂, O₂, and Ar.

19. The method of claim 17 wherein step (c1) comprises:

supplying 30 to 50 sccm of Cl₂, 10 to 30 sccm of O₂, and 10 to 30 sccm of Ar, maintaining a gas pressure of about 5 to 40 mTorr, applying a bias power to a cathode electrode of about 0 to 300 Watt, applying power to an inductively coupled antenna of about 200 to 3000 Watt, and maintaining the substrate at a temperature of about 15 to 85 degrees Celsius.

20. The method of claim 6 wherein step (d) further comprises:

applying a solution comprising HF, NH₄F, and deionized water until the residue that is present on the substrate after step (c) is removed; and

rinsing the substrate in distilled water.

21. The method of claim 20 wherein the solution comprises between 1 and 49% of HF by volume and applied at a temperature of about 10 to 30 degrees Celsius for a duration of about 10 to 120 seconds.

22. The method of claim 6 wherein step (e) further comprises:

(e1) depositing a layer of material that is used to form the second sacrificial hard mask on the top electrode;

(e2) forming a photoresist etch mask defining the second sacrificial hard mask; and

(e3) etching the second sacrificial hard mask in a plasma comprising chlorine or fluorine.

23. The method of claim 22 wherein the photoresist etch mask comprises a layer of anti-reflective coating.

24. The method of claim 22 wherein step (e3) uses the plasma comprising CF₄, CHF₃, and Ar.

25. The method of claim 22 wherein step (e3) comprises:

supplying about 40 to 80 sccm of CF₄, 10 to 30 sccm of CHF₃, and 40 to 80 sccm of Ar, maintaining in a reaction chamber a gas pressure at about 5 to 40 mTorr, applying a bias power to a cathode electrode of about 0 to 300 Watt, applying power to an inductively coupled antenna of about 200 to 3000 Watt, and maintaining the substrate at a temperature of about 15 to 80 degrees Celsius.

26. The method of claim 6 wherein step (f) further comprises:

(f1) etching of the magnetic film stack in a plasma comprising BCl₃.

27. The method of claim 26 wherein step (f1) uses the plasma comprising BCl₃ and Ar.

28. The method of claim 26 wherein step (f1) comprises:

supplying 5 to 25 sccm of BCl₃ and 20 to 100 sccm of Ar, maintaining a gas pressure of about 5 to 40 mTorr, applying a bias power to a cathode electrode of about 0 to 300 Watt, applying power to an inductively coupled antenna of about 200 to 3000 Watt, and maintaining the substrate at a temperature of about 15 to 80 degrees Celsius.

29. The method of claim 6 wherein step (g) is performed using the same etching chemistry as step (f).

30. The method of claim 6 wherein step (f) and step (g) are performed in the same reactor.

31. The method of claim 6 wherein step (f), step (g), and step (h) are performed in the same reactor.

32. The method of claim 6 wherein a step (g) further comprises:

(g1) etching the bottom electrode layer in a plasma comprising Cl₂.

33. The method of claim 32 wherein step (g1) uses the plasma comprising Cl₂ and Ar.

34. The method of claim 32 wherein step (g1) comprises:

supplying 10 to 100 sccm of Cl₂ and 10 to 100 sccm of Ar, maintaining a gas pressure of about 5 to 40 mTorr, applying a bias power to a cathode electrode of about 0 to 300 Watt, applying power to an inductively coupled antenna of about 200 to 3000 Watt, and maintaining the substrate at a temperature of about 15 to 80 degrees Celsius.

35. The method of claim 6 wherein step (h) further comprises:

applying a solvent comprising NH₄OH, H₂O₂, and H₂O to the substrate until a residue that is present on the substrate after step (b) is removed; and

rinsing the substrate in distilled water.

36. The method of claim 35 wherein the solvent comprises, by weight, about (0.1-10) parts of NH₄OH, (0.1-10) parts of H₂O₂, and (1-100) parts of H₂O, and is applied at a temperature of about 45 to 65 degrees Celsius for a duration of about 30 to 120 seconds.

37. The method of claim 35 wherein the solvent comprises, by weight, 1 part of NH₄OH, 10 part of H₂O₂, and 10 parts of H₂O, and is applied at a temperature of about 45 to 65 degrees Celsius for a duration of about 30 to 120 seconds.

38. The method of claim 6 wherein step (h) further comprises:

(h1) removing the second sacrificial hard mask;

(h2) removing the barrier layer outside a perimeter of the bottom electrode; and

(h3) rinsing the substrate in distilled water.

39. The method of claim 38 wherein step (h1) and step (h2) are performed simultaneously in the same reactor.

40. The method of claim 38 wherein step (h2) is performed using the same chemistry as step (h1).

41. The method of claim 38 wherein step (h1) further comprises:

applying a solution comprising HF, NH₄F, and deionized water.

42. The method of claim 41 wherein the solution comprises between 1 and 49% of HF by volume and applied at a temperature of about 10 to 30 degrees Celsius for a duration of about 10 to 120 seconds.