Method for improved alignment of magnetic tunnel junction elements

• US 6,933,204 B2
• Filed: 10/13/2003
• Issued: 08/23/2005
• Est. Priority Date: 10/13/2003
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation, Samsung Electronics Co. Ltd.
• Original Assignee: International Business Machines Corporation
• Inventors: Costrini, Greg, Sarma, Chandrasekhar, Kanakasabapathy, Sivananda K., Gaidis, Michael C., Hummel, John P., Kasko, Ihar
• Primary Examiner(s): Dang, Phuc T.
• Application Number:
  US10/605,604
• Publication Number:
  US 20050079683A1
• Time in Patent Office: 680 Days
• Field of Search: 438/401, 438/443, 438/453, 438/523, 438/533, 438/551, 438/622, 438/942
• US Class Current: 438/401
• CPC Class Codes: G03F 9/7076 Mark details, e.g. phase grating mark, temporary mark
• CPC Class Codes: G03F 9/708 Mark formation
• CPC Class Codes: G03F 9/7084 Position of mark on substrate, i.e. position in (x, y, z) of mark, e.g. buried or resist covered mark, mark on rearside, at the substrate edge, in the circuit area, latent image mark, marks in plural levels
• CPC Class Codes: H01L 2223/54453 for use prior to dicing
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices

Abstract

A method for aligning an opaque, active device in a semiconductor structure includes forming an opaque layer over an optically transparent layer formed on a lower metallization level, the lower metallization level including one or more alignment marks formed therein. A portion of the opaque layer is patterned and opened corresponding to the location of the one or more alignment marks in the lower metallization level so as to render the one or more alignment marks optically visible. The opaque layer is then patterned with respect to the lower metallization level, using the optically visible one or more alignment marks.

Claims

1. A method for aligning an opaque, active device in a semiconductor structure, the method comprising:

forming an opaque layer over an optically transparent layer formed on a lower metallization level, said lower metallization level including one or more alignment marks formed therein; and

patterning and opening, through topographic alignment, a portion of said opaque layer corresponding to the location of said one or more alignment marks in said lower metallization level so as to render said one or more alignment marks optically visible; and

patterning said opaque layer with respect to said lower metallization level, using said optically visible one or more alignment marks.

2. The method of claim 1, wherein said optically transparent layer comprises a tantalum nitride (TaN) layer.

3. The method of claim 1, further comprising forming a hardmask over said opaque layer.

4. The method of claim 3, wherein said hardmask further comprises a titanium nitride (TiN) layer.

5. The method of claim 1, wherein a photoresist material used to pattern said opaque layer with respect to said lower metallization level is also used to protect said opened portion of said opaque layer corresponding to the location of said one or more alignment marks.

6. The method of claim 1, further comprising forming an oxide hardmask over an exposed portion of said optically transparent layer as a result of said patterning and opening a portion of said opaque layer.

7. The method of claim 1 wherein said one or more alignment marks comprise copper.

8. A method for aligning a magnetic tunnel junction (MTJ) element in a semiconductor memory array, the method comprising:

forming an MTJ stack layer over an optically transparent layer formed on a lower metallization level, said lower metallization level including one or more alignment marks formed therein; and

patterning and opening a portion of said MTJ stack layer corresponding to the location of said one or more alignment marks in said lower metallization level so as to render said one or more alignment marks optically visible; and

patterning said MTJ stack layer with respect to said lower metallization level, using said optically visible one or more alignment marks.

9. The method of claim 8, wherein said optically transparent layer comprises a tantalum nitride (TaN) layer.

10. The method of claim 8, further comprising forming a hardmask over said MTJ stack layer.

11. The method of claim 10, wherein said hardmask further comprises a titanium nitride (TiN) layer.

12. The method of claim 8, wherein a photoresist material used to pattern said MTJ stack layer with respect to said lower metallization level is also used to protect said opened portion of said MTJ stack layer corresponding to the location of said one or more alignment marks.

13. The method of claim 8, further comprising forming an oxide hardmask over an exposed portion of said optically transparent layer as a result of said patterning and opening a portion of said MTJ stack layer.

14. The method of claim 8, wherein said one or more alignment marks comprise copper.

15. The method of claim 8, wherein said patterning and opening a portion of said MTJ stack layer is implemented through topographic alignment.