Forming dielectric film with high resistance to tilting
A method includes depositing a dielectric layer over a substrate, and etching the dielectric layer to form an opening and to expose a first conductive feature underlying the dielectric layer. The dielectric layer is formed using a precursor including nitrogen therein. The method further includes depositing a sacrificial spacer layer extending into the opening, and patterning the sacrificial spacer layer to remove a bottom portion of the sacrificial spacer layer. A vertical portion of the sacrificial spacer layer in the opening and on sidewalls of the dielectric layer is left to form a ring. A second conductive feature is formed in the opening. The second conductive feature is encircled by the ring, and is over and electrically coupled to the first conductive feature. At least a portion of the ring is removed to form an air spacer.
1 . A method comprising:
depositing a dielectric layer over a substrate, wherein the depositing the dielectric layer comprises adjusting a flow rate of a nitrogen-containing precursor, so that the dielectric layer comprises:
a bottom portion comprising nitrogen and having a constant nitrogen atomic percentage;
a middle portion having a higher nitrogen atomic percentage than the bottom portion of the dielectric layer; and
an upper portion having a lower nitrogen atomic percentage than the middle portion of the dielectric layer;
etching the dielectric layer to form an opening, wherein a first conductive feature underlying the dielectric layer is exposed to the opening;
depositing a sacrificial spacer layer extending into the opening;
patterning the sacrificial spacer layer, wherein a bottom portion of the sacrificial spacer layer at a bottom of the opening is removed to reveal the first conductive feature, and a first vertical portion of the sacrificial spacer layer in the opening and on sidewalls of the dielectric layer is left to form a first ring;
forming a second conductive feature in the opening, wherein the second conductive feature is encircled by the first ring, and is over and electrically coupled to the first conductive feature, and wherein the second conductive feature comprises a substantially straight edge extending from a bottom surface level of the bottom portion to a top surface level of the upper portion; and
removing at least a portion of the first ring to form an air spacer.
2 . The method of claim 1 , wherein the depositing the dielectric layer comprises depositing a high-k dielectric material.
3 . The method of claim 1 further comprising forming a metal capping layer over the second conductive feature, wherein an interface between the metal capping layer and the second conductive feature is coplanar with a top surface of the dielectric layer, wherein the metal capping layer comprises an extension portion extending into the air spacer.
4 . The method of claim 1 further forming a metal capping layer over the second conductive feature, wherein the first ring is removed after the metal capping layer is formed.
5 . The method of claim 1 , wherein the depositing the dielectric layer is performed using a first precursor comprising silicon, carbon, and hydrogen, and a second precursor comprising nitrogen.
6 . The method of claim 1 , wherein the depositing the dielectric layer is performed without using porogen.
7 . The method of claim 1 further comprising forming an additional dielectric layer over the sacrificial spacer layer and sealing the air spacer, wherein at a time after the air spacer is formed, a residue portion of the first ring is left underlying the additional dielectric layer.
8 . A method comprising:
forming a first conductive feature over a substrate;
depositing a first etch stop layer over the first conductive feature;
depositing a dielectric layer over the first etch stop layer, wherein the dielectric layer comprises nitrogen therein, wherein the depositing the dielectric layer comprises:
depositing a bottom portion having a first nitrogen atomic percentage;
depositing a middle portion over the bottom portion, wherein the middle portion has a second nitrogen atomic percentage higher than the first nitrogen atomic percentage; and
depositing an upper portion over the middle portion, wherein the upper portion has a third nitrogen atomic percentage lower than the second nitrogen atomic percentage;
forming a second conductive feature in the dielectric layer and the first etch stop layer, wherein the second conductive feature is over and contacting the first conductive feature, wherein the second conductive feature is encircled by an air spacer, wherein sidewalls of the second conductive feature are exposed to the air spacer, and wherein the air spacer extends from substantially a bottom surface of the bottom portion to a top surface of the upper portion; and
depositing a second etch stop layer over and contacting the dielectric layer, wherein the second etch stop layer is further over the second conductive feature.
9 . The method of claim 8 , wherein the depositing the dielectric layer comprises depositing a high-k dielectric material.
10 . The method of claim 8 , wherein the forming the air spacer comprises:
forming a sacrificial spacer layer, wherein the second conductive feature is formed in a region encircled by the sacrificial spacer layer; and
etching to remove first part of the sacrificial spacer layer and to form the air spacer, wherein a top surface of a second part of the sacrificial spacer layer is underlying, and is exposed to, the air spacer.
11 . The method of claim 8 further comprising performing a selective deposition process to form a metal cap over the second conductive feature, wherein a portion of the metal cap is at a location lower than a top surface of the second conductive feature.
12 . A method comprising:
forming a first conductive feature;
forming a dielectric layer over the first conductive feature, wherein the forming the dielectric layer comprises adjusting a flow rate of a nitrogen-containing precursor, so that a middle portion of the dielectric layer has a higher nitrogen atomic percentage than a respective lower portion of the dielectric layer, and an upper portion of the of the dielectric layer has a lower nitrogen atomic percentage than the middle portion;
forming a second conductive feature over and electrically coupling to the first conductive feature, wherein the second conductive feature comprises:
a diffusion barrier; and
a metallic material in a basin formed by the diffusion barrier, wherein the second conductive feature comprises a substantially straight edge extending from a bottom surface level of the lower portion to a top surface level of the upper portion; and
forming an air spacer encircling a top portion of the second conductive feature, wherein the air spacer is encircled by the dielectric layer, and wherein the dielectric layer comprises a high-k dielectric material that comprises nitrogen.
13 . The method of claim 12 , wherein no dielectric material is between the second conductive feature and the air spacer.
14 . The method of claim 12 , wherein the forming the air spacer comprises removing a sacrificial spacer layer between the dielectric layer and the second conductive feature, and wherein after the removing the sacrificial spacer layer, a residue portion of the sacrificial spacer layer is left.
15 . The method of claim 10 , wherein before the air spacer is formed, the first part of the sacrificial spacer layer overlaps the second part of the sacrificial spacer layer, with first edges of the first part of the sacrificial spacer layer being vertically aligned to respective second edges of the second part of the sacrificial spacer layer.
16 . The method of claim 12 , wherein the forming the dielectric layer comprises implanting nitrogen, so that the upper portion has the lower nitrogen atomic percentage than the respective lower portion.
17 . The method of claim 8 , wherein the depositing the dielectric layer comprises adjusting a flow rate of a nitrogen-containing precursor continuously.
18 . The method of claim 1 , wherein the the middle portion and the upper portion of the dielectric layer are formed using a same method by adjusting flow rates of same precursors.
19 . The method of claim 1 , wherein the air spacer extends from the bottom surface level of the bottom portion to the top surface level of the upper portion.
20 . The method of claim 8 , wherein the second conductive feature comprises a substantially straight edge extending from the bottom surface of the bottom portion to the top surface of the upper portion.