Process for improving photoresist pillar adhesion during MRAM fabrication

• US 10,424,726 B2
• Filed: 12/28/2017
• Issued: 09/24/2019
• Est. Priority Date: 12/28/2017
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Spin Memory, Inc.
• Inventors: Dobisz, Elizabeth, Manandhar, Pradeep
• Primary Examiner(s): Blum, David S
• Application Number:
  US15/857,318
• Publication Number:
  US 20190207100A1
• Time in Patent Office: 635 Days
• Field of Search: 438 3
• CPC Class Codes: G03F 7/0035 Multiple processes, e.g. applying a further resist layer on an already in a previously step, processed pattern or textured surface
• CPC Class Codes: G03F 7/0751 used as adhesion-promoting additives or as means to improve adhesion
• CPC Class Codes: G03F 7/0757 Macromolecular compounds containing Si-O, Si-C or Si-N bonds G03F7/0752 takes precedence
• CPC Class Codes: G03F 7/094 Multilayer resist systems, e.g. planarising layers
• CPC Class Codes: G03F 7/16 Coating processes; Apparatus therefor applying coatings to base materials in general B05; applying photosensitive compositions to base for photographic purposes G03C1/74
• CPC Class Codes: H01L 21/0274 Photolithographic processes
• CPC Class Codes: H01L 21/0332 characterised by their composition, e.g. multilayer masks, materials
• 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 method for improving photo resist adhesion to an underlying hard mask layer. The method includes a cleaning step that includes applying tetramethylammonium hydroxide (TMAH) to coat a hard mask layer of a wafer. The method further includes puddle developing the wafer for a first desired amount of time, and rinsing the wafer in running water for a second desired amount of time. The method further includes spin drying the wafer, and baking the wafer for a third desired amount of time. The method concludes with the proceeding of subsequent photolithographic processes on the wafer.

Claims

1. A method for improving photo resist adhesion to an underlying hard layer, comprising:

cleaning the surface of the hard layer by applying tetramethylammonium hydroxide (TMAH) to coat a hard mask layer of the wafer;

puddle developing the wafer for a first desired amount of time;

rinsing the wafer for a second desired amount of time;

spin drying the wafer;

baking the wafer for a third desired amount of time; and

proceeding with subsequent photolithographic processes on the wafer, which fabricates pillars therein.

2. The method of claim 1, wherein the first desired amount of time is approximately 2 minutes.

3. The method of claim 1, wherein the second desired amount of time is approximately 1 minute.

4. The method of claim 1, wherein the third desired amount of time is approximately 5 minutes.

5. The method of claim 1, wherein the rinsing uses running water and the water is deionized water.

6. The method of claim 1, further comprising cooling on a chilled plate for approximately one minute subsequent to the baking.

7. The method of claim 1, further comprising treating the wafer with hexamethyldisilazane (HMDS) subsequent to the baking.

8. The method of claim 1, wherein the underlying hard mask layer is tantalum nitride (TaN).

9. A method for improving photo resist pillar adhesion to a wafer, the method comprising:

cleaning a surface of tantalum nitride hard layer by applying tetramethylammonium hydroxide (TMAH) to coat the tantalum nitride hard layer of the wafer;

puddle developing the wafer for a first desired amount of time;

rinsing the wafer in running water for a second desired amount of time;

spin drying the wafer;

baking the wafer for a third desired amount of time; and

proceeding with subsequent photolithographic processes on the wafer.

10. The method of claim 9, wherein the first desired amount of time is approximately 2 minutes.

11. The method of claim 9, wherein the second desired amount of time is approximately 1 minute.

12. The method of claim 9, wherein the third desired amount of time is approximately 5 minutes.

13. The method of claim 9, wherein the water is deionized water.

14. The method of claim 9, further comprising treating the wafer with hexamethyldisilazane (HMDS) subsequent to the baking.

15. The method of claim 9, wherein the wafer is treated with hexamethyldisilazane (HMDS) subsequent to the baking.

16. A method for manufacturing an MRAM device, the method comprising:

applying tetramethylammonium hydroxide (TMAH) to coat a tantalum nitride hard layer of a wafer;

submerging the wafer in a dish of TMAH for a first desired amount of time;

rinsing the wafer in running water for a second desired amount of time;

spin drying the wafer;

baking the wafer for a third desired amount of time; and

proceeding with subsequent photolithographic processes on the wafer.

17. The method of claim 16 wherein the applying is a cleaning process and wherein the first desired amount of time is approximately 2 minutes.

18. The method of claim 17, wherein the second desired amount of time is approximately 1 minute.

19. The method of claim 18, wherein the third desired amount of time is approximately 5 minutes.

20. The method of claim 16, wherein the water is deionized water.