Method for CuO reduction by using two step nitrogen oxygen and reducing plasma treatment

1. A method of fabrication of a copper interconnect comprising the steps of:

providing a semiconductor structure comprised of a copper interconnect and a dielectric layer over the semiconductor substrate, the copper interconnect having a surface;

treating the surface of said copper interconnect with a nitrogen and oxygen containing plasma treatment under a vacuum, wherein the nitrogen and oxygen containing plasma treatment comprises

a N 2 O flow between about 1000 and 5000 sccm,

a HF RF power between 200 and 400 W,

a LF RF power between 50 and 150 W,

a pressure between 1.5 and 4.5 torr,

a treatment time between 10 and 20 seconds; and

a temperature between 350 and 450 degrees C; then

treating the copper interconnect with a reducing plasma treatment without breaking the vacuum; and

forming a capping layer over the copper interconnect without breaking the vacuum.

2. The method of claim 1 which includes cleaning the surface of said semiconductor structure before the step of treating the surface of said copper interconnect with a nitrogen and oxygen containing plasma treatment.

3. The method according to claim 1 wherein the nitrogen and oxygen containing plasma treatment consists essentially of N 2 O.

4. The method according to claim 1 wherein the reducing plasma treatment is a NH 3 plasma treatment comprising about:

a N 2 flow between 1000 and 5000 sccm;

a NH 3 flow between 2000 and 5600 sccm;

a HF RF power between 200 and 400 W;

a LP RF power between 50 and 150 W;

a pressure between 1.5 and 4.5 torr;

a treatment time between 10 and 20 seconds; and

a temperature between 350 and 450 degrees C.

5. The method according to claim 1 wherein the reducing plasma treatment is a NH 3 plasma treatment comprising N 2 and NH 3 .

6. The method according to claim 1 wherein the reducing plasma treatment is a H 2 plasma treatment comprising:

a H 2 flow between 3000 and 7000 sccm;

a HF RF power between 200 and 500 W;

a LF RF power between 50 and 200 W;

a pressure between 2 and 6 torr;

a treatment time between 5 and 20 seconds; and

a temperature between 350 and 450 degrees C.

7. The method according to claim 1 wherein the reducing plasma treatment is a H 2 plasma treatment comprising:

a H 2 flow between 1400 to 1800 sccm;

a HP RF power between 290 and 310 W;

a LF RF power between 90 and 110 W;

a pressure between 3 and 5 torr;

a treatment time between 8 arid 12 seconds;

a temperature between 390 and 410 degrees C; and

a wafer size of about 200 nm;

using an ICP plasma type reactor.

8. The method of claim 1 , wherein the reducing plasma treatment is a NH 3 plasma treatment or a H 2 plasma treatment.

9. The method of claim 1 which further comprises, before the nitrogen and oxygen containing plasma treatment step, the step of chemical-mechanical polishing said copper interconnect to planarize said copper interconnect.

10. The method of claim 1 wherein the nitrogen and oxygen containing plasma treatment is comprised of N 2 O.

11. A method of fabrication of a copper interconnect comprising the steps of:

a) providing a semiconductor structure comprised of a copper interconnect and a dielectric layer over a semiconductor substrate;

b) chemical-mechanical polishing said copper interconnect to planarize said copper interconnect;

c) treating the surface of said copper interconnect with a nitrogen and oxygen containing plasma treatment under a vacuum to form a CuO layer on the copper interconnect;

(1) the nitrogen and oxygen containing plasma treatment comprises:

a N 2 O flow between about 1000 and 5000 sccm;

a HF RE power between 200 and 400 W;

a LF RE power between 50 and 150 W;

a pressure between 1.5 and 4.5 torr;

a treatment time between 10 and 20 seconds; and

a temperature between 350 and 450 degrees C; then

d) without breaking the vacuum, treating the copper interconnect with a reducing plasma treatment to remove the CuO layer from the copper interconnect;

(1) the reducing plasma treatment is a NH3 plasma treatment comprising about:

a N 2 flow between 1000 and 5000 sccm;

a NH 3 flow between 2000 and 5600 sccm;

a H RF power between 200 and 400 W;

a LF RF power between 50 and 150 W;

a pressure between 1.5 and 4.5 torr;

a treatment time between 10 and 20 seconds; and

a temperature between 350 and 450 degrees C; and

e) without breaking the vacuum, forming a capping layer over the copper interconnect.

12. The method of claim 11 wherein treating the copper interconnect with a reducing plasma treatment is performed before forming a capping layer over the copper interconnect.