Microstructure device including a metallization structure with self-aligned air gaps between closely spaced metal lines
In sophisticated metallization systems, air gaps may be formed on the basis of a self-aligned patterning regime during which the conductive cap material of metal lines may be protected by providing one or more materials, which may subsequently be removed. Consequently, the etch behavior and the electrical characteristics of metal lines during the self-aligned patterning regime may be individually adjusted.
1. A method, comprising:
performing a first selective deposition process to form a conductive cap layer selectively on each of a plurality of metal lines formed in a first dielectric material of a metallization layer of a microstructure device;
performing a second selective deposition process so as to form a first etch protection material in a spatially selective manner on each conductive cap layer so as to cover an entirety of each conductive cap layer and protect the conductive cap layer in a subsequent recess etching process, said first etch protection material exposing at least a portion of said first dielectric material between two neighboring ones of said metal lines;
performing a third selective deposition process so as to form a second etch protection material in a spatially selective manner on each of said first etch protection materials;
with the first and second etch protection materials covering the conductive cap layers, performing the recess etching process to form a recess in said at least a portion of said first dielectric material; and
depositing a second dielectric material so as to close said recess and form an air gap on the basis of said recess.
2. The method of claim 1 , wherein the first and second etch protection material formed on each of the two neighboring ones of said metal lines is positioned above a portion of the dielectric material, thereby determining a width of said recess.
3. The method of claim 1 , wherein, prior to performing the second selective deposition process to form the first etch protection material, the method comprises performing a surface treatment so as to reduce a deposition rate for said first dielectric material as compared to said conductive cap layer for a subsequent deposition process.
4. The method of claim 1 , further comprising removing said first etch protection material and said second etch protection material at least from said conductive cap layer after forming said recess.
5. The method of claim 4 , wherein said first etch protection material and said second etch protection material are removed at least from said conductive cap layer prior to depositing said second dielectric material.
6. The method of claim 4 , wherein said first etch protection material and said second etch protection material are removed at least from said conductive cap layer after depositing said second dielectric material.
7. The method of claim 6 , wherein said first etch protection material, said second etch protection material, and excess material of said second dielectric material are removed together by performing a planarization process.
8. The method of claim 1 , wherein a material composition of said conductive cap layer is selected so as to form an interface of increased electromigration strength with said metal lines.
9. The method of claim 1 , wherein a material composition and a thickness of said first etch protection material and said second etch protection materials are selected so as to avoid exposure of said conductive cap layer when forming said recess.
10. The method of claim 1 , wherein said first and second etch protection materials comprise two or more material layers of different material composition.
11. The method of claim 1 , wherein each conductive cap layer is aligned with the metal line and at least one barrier layer in which the metal line is nested.