Low energy etch process for nitrogen-containing dielectric layer
A stack that includes, from bottom to top, a nitrogen-containing dielectric layer, an interconnect level dielectric material layer, and a hard mask layer is formed on a substrate. The hard mask layer and the interconnect level dielectric material layer are patterned by an etch. Employing the patterned hard mask layer as an etch mask, the nitrogen-containing dielectric layer is patterned by a break-through anisotropic etch, which employs a fluorohydrocarbon-containing plasma to break through the nitrogen-containing dielectric layer. Fluorohydrocarbon gases used to generate the fluorohydrocarbon-containing plasma generate a carbon-rich polymer residue, which interact with the nitrogen-containing dielectric layer to form volatile compounds. Plasma energy can be decreased below 100 eV to reduce damage to physically exposed surfaces of the interconnect level dielectric material layer.
1. A structure comprising:
a stack comprising, from bottom to top, a substrate, a nitrogen-containing dielectric layer, an interconnect level dielectric material layer, and a hard mask layer;
an opening present within said hard mask layer and said interconnect level dielectric material layer and extending downward into at least an upper portion of said nitrogen-containing dielectric layer; and
a carbon-rich polymer layer comprising a carbon-rich polymer including carbon and fluorine and having a ratio of carbon to fluorine that is greater than 1, wherein a first portion of said carbon-rich polymer layer is located on a surface of said nitrogen-containing dielectric layer exposed by said opening and has a first thickness, a second portion of said carbon-rich polymer layer is located on a top surface of said hard mask layer and has a second thickness greater than said first thickness, and wherein said carbon-rich polymer has a composition that includes carbon at an atomic concentration between 30% and 40%, hydrogen at an atomic concentration between 40% and 50%, fluorine at an atomic concentration between 5.0% and 10.0%, and oxygen at an atomic concentration less than 5%.
2. The structure of claim 1 , wherein said carbon-rich polymer has a refractive index in a range from 1.8 to 2.2.
3. The structure of claim 1 , wherein said carbon-rich polymer has a density in a range from 1.5 g/cm 3 to 1.7 g/cm 3 .
4. The structure of claim 1 , wherein said carbon-rich polymer includes hydrogen at an atomic concentration that is at least one half of said atomic concentration of carbon in said carbon-rich polymer.
5. The structure of claim 1 , wherein an atomic ratio of hydrogen to carbon in said carbon-rich polymer is between 0.5 and 3.0.
6. The structure of claim 1 , wherein said nitrogen-containing dielectric layer comprises silicon nitride.
7. The structure of claim 1 , wherein said nitrogen-containing dielectric layer comprises a dielectric material having a dielectric constant less than 3.9 and including nitrogen.
8. The structure of claim 1 , further comprising a volatile compound formed on said surface of said nitrogen-containing dielectric layer within said opening, wherein said volatile compound is represented by a formula of C i H j F k N l , wherein i is an integer ranging from 1 to 6, j is an integer ranging from 0 to 8, k is an integer ranging from 0 to 6, and l is an integer ranging from 0 to 4.
9. The structure of claim 8 , wherein said volatile compound is derived from a reaction of nitrogen in said nitrogen-containing dielectric layer and said first portion of said carbon-rich polymer layer present on said surface of nitrogen-containing dielectric layer.
10. The structure of claim 1 , wherein said second portion of said carbon-rich polymer layer does not include nitrogen.
11. The structure of claim 1 , wherein said first thickness ranges from 0.2 nm to 1 nm, and said second thickness ranges from 1 nm to 3 nm.
12. The structure of claim 1 , wherein said nitrogen-containing dielectric layer comprises a dielectric metal oxynitride selected from the group consisting of HfO x N y , ZrO x N y , La 2 O x N y , TiO x N y , SrTiO x N y , LaAlO x N 3 , Y 2 O x N y , and an alloy thereof.
13. The structure claim 1 , wherein said hard mask layer comprises a metallic material.
14. The structure of claim 13 , wherein said metallic material comprises WC, TiC, a stack thereof, or an alloy thereof.
15. The structure of claim 1 , further comprising a dielectric cap layer located between said hard mask layer and said interconnect level dielectric material layer.
16. The structure of claim 15 , wherein said dielectric cap layer comprises silicon oxide, silicon nitride, silicon oxynitride, a dielectric metal oxide, or a combination thereof.
17. The structure of claim 1 , wherein said interconnect level dielectric material layer comprises a spin-on-oxide, an undoped organosilicate glass, a fluorosilicate glass (FSG), a phosphosilicate glass (PSG), a borosilicate glass (BSG), or a borophosphosilicate glass (BPSG).
18. The structure of claim 1 , further comprising an underlying metal interconnect level structure located between said substrate and said nitrogen-containing dielectric layer.
19. The structure of claim 18 , wherein said underlying metal interconnect level structure comprises at least one conductive structure and at least one underlying dielectric layer.