Semiconductor structure and fabrication method thereof

1 . A semiconductor structure, comprising:

a substrate;

a first dielectric layer on the substrate;

an etch stop layer on the first dielectric layer;

a second dielectric layer on the etch stop layer;

a first conductor and a second conductor in the second dielectric layer;

an air gap in the second dielectric layer and between the first conductor and the second conductor;

a first low-polarity dielectric layer on a sidewall surface of the second dielectric layer within the air gap;

a second low-polarity dielectric layer disposed around the first conductor; and

a third low-polarity dielectric layer disposed around the second conductor.

2 . The semiconductor structure according to claim 1 , wherein the first dielectric layer is a silicon oxide layer and the second dielectric layer is a low-dielectric constant (low-k) material layer.

3 . The semiconductor structure according to claim 2 , wherein the low-k material layer comprises organo-silicate glass (OSG) based low-k dielectric layer.

4 . The semiconductor structure according to claim 1 , wherein the first low-polarity dielectric layer is a silylated surface layer.

5 . The semiconductor structure according to claim 1 , wherein the second and third low-polarity dielectric layers are silylated surface layers.

6 . The semiconductor structure according to claim 1 , wherein the second low-polarity dielectric layer is in direct contact with the first conductor, and the third low-polarity dielectric layer is in direct contact with the second conductor.

7 . The semiconductor structure according to claim 1 , wherein the first conductor and the second conductor comprise copper.

8 . The semiconductor structure according to claim 1 , wherein the air gap extends into the etch stop layer and the first dielectric layer.

9 . The semiconductor structure according to claim 8 further comprising:

a silylated oxide surface layer on a sidewall surface of the first dielectric layer.