Use of CMP to contact a MTJ structure without forming a via

• US 8,105,948 B2
• Filed: 02/14/2008
• Issued: 01/31/2012
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: MagiQ Technologies, Incorporated
• Inventors: Zhong, Adam, Kan, Wai-Ming, Zhong, Tom, Torng, Chyu-Jiuh
• Primary Examiner(s): Vinh, Lan
• Application Number:
  US12/070,286
• Publication Number:
  US 20090209102A1
• Time in Patent Office: 1,447 Days
• Field of Search: 438/680, 438/691, 438/692, 438/693, 438/756, 216/89.9, 216/88, 216/89, 216/97
• US Class Current: 438/692
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step
• CPC Class Codes: H10N 50/01 Manufacture or treatment

Abstract

A process is described for making contact to the buried capping layers of GMR and MTJ devices without the need to form and fill via holes. CMP is applied to the structure in three steps: (1) conventional CMP (2) a Highly Selective Slurry (HSS) is substituted for the conventional slurry to just expose the capping layer, and (3) the HSS is diluted and used to clean the surface as well as to cause a slight protrusion of the capping layers above the surrounding dielectric surface, making it easier the contact them without damaging the devices below.

Claims

1. A method for connecting to an area that is to be fully covered by a dielectric layer, comprising:

forming a conductive pedestal, having a top surface and a height, that contacts, and extends upwards from, said area;

covering any exposed surfaces, including said pedestal, with a layer of dielectric material, said dielectric layer having a first top surface and a thickness that exceeds said pedestal height, whereby said pedestal is fully covered by said dielectric layer;

using only a highly selective slurry (HSS), that removes dielectric material at a faster rate than it removes conductive material, performing chemical mechanical polishing (CMP) of said first top surface until said dielectric layer has a second top surface whereby said pedestal top surface is fully exposed without removal of any additional layers; and

then contacting said exposed pedestal top surface, thereby connecting to said area.

2. The method of claim 1 wherein said HSS removes dielectric material at a rate that is between about 100 and 300 times faster than the rate at which it removes conductive material.

3. The method of claim 1 wherein said HSS removes dielectric material at a rate that is between about 20 and 500 times faster than the rate at which it removes conductive material.

4. The method of claim 1 wherein CMP is terminated when the intensity of light reflected from said area reaches a preset level.

5. The method of claim 1 wherein CMP is continued beyond said preset reflected light intensity value until a predetermined amount of said pedestal protrudes above said second dielectric top surface.

6. A process for connecting to a magneto-resistive, current perpendicular to plane, (MR CPP) device, comprising:

providing a substrate and forming thereon a MR CPP device having a capping layer;

fully covering said MR CPP device with a layer of dielectric material, said dielectric layer having a first top surface that is at least 500 Angstroms above said capping layer;

using conventional CMP, including a conventional slurry, etching said dielectric layer until it has a second top surface that is at most 50 Angstroms above said capping layer;

then replacing said conventional slurry with a highly selective slurry (HSS), that preferentially removes dielectric material relative to metal, and then continuing to use CMP whereby all dielectric material above said capping layer is removed, thereby fully exposing a top surface of said capping layer;

diluting said HSS with deionized water and then lightly buffing all top surfaces whereby said top surfaces are cleaned and said capping layer protrudes above said cleaned surface; and

then forming, on said cleaned surface, a connection to said protruding capping layer, thereby facilitating contacting said MR CPP devices with minimal risk of damaging said MR CPP devices.

7. The process recited in claim 6 wherein said dielectric material is selected from the group consisting of silicon oxide and silicon nitride.

8. The process recited in claim 6 wherein said capping layer is selected from the group consisting of nickel, iron, tantalum, ruthenium, platinum, and all rare earth metals.

9. The process recited in claim 6 wherein said dielectric material is silicon oxide and said capping layer is tantalum.

10. The process recited in claim 6 wherein said HSS removes dielectric material at rate that is between about 100 and 300 times faster than the rate at which it removes conductive material.

11. The process recited in claim 6 wherein said HSS removes dielectric material at a rate that is between about 50 and 500 times faster than the rate at which it removes conductive material.

12. The process recited in claim 6 wherein a determination of when conventional CMP, using said conventional slurry, is to be terminated is based on measurements of light reflected from said dielectric second top surface.

13. The process recited in claim 6 wherein a determination of when CMP, using said HSS, is to be terminated is based on measurements of light reflected from said dielectric surface after all dielectric material above said capping layer has been removed and said top surface of said capping layer has been fully exposed.

14. The process recited in claim 6 wherein the step of etching said dielectric layer until it has a second top surface that is at most 50 Angstroms above said capping layer enables a top metal layer to be in close proximity to said MR CPP device thereby increasing magnetic field detection efficiency of said MR CPP device.