Semiconductor structures and fabrication methods for improving undercut between porous film and hardmask film
A method is provided for fabricating a semiconductor structure. The method includes providing a substrate; and forming a to-be-etched layer made of porous low dielectric constant material on one surface of the semiconductor substrate. The method also includes forming a first hard mask layer made of nitrogen-doped silicon oxycarbide (SiOC(N)) on the to-be-etched layer; and etching the first hard mask layer to have patterns corresponding to positions of subsequently formed openings. Further, the method includes forming the plurality of openings without substantial undercut between the to-be-etched layer and the first hard mask layer in the to-be-etched layer using the first hard mask layer as an etching mask; and forming a conductive structure in each of the openings.
1. A method for fabricating a semiconductor structure, comprising:
providing a substrate;
forming a to-be-etched layer made of a porous low-K dielectric material including boron nitride on one surface of the substrate;
forming a first hard mask layer made of nitrogen-doped silicon oxycarbide (SiOC(N)) directly on the to-be-etched layer;
etching the first hard mask layer to have same patterns corresponding to positions of subsequently formed a plurality of openings;
forming the plurality of openings through an entire thickness of the to-be-etched layer using the first hard mask layer as an etching;
etching and cleaning a bottom surface of the openings along with side surfaces of both the to-be-etched layer and the first hard mask layer in the openings by a wet chemical cleaning process, to level the side surfaces of both the to-be-etched layer and the first hard mask layer with each other in the openings, wherein an etching rate of a solution of the wet chemical cleaning process to the first hard mask layer and an etching rate of the solution of the wet chemical cleaning process to the to-be-etched layer is identical; and
after the wet chemical cleaning process, forming a conductive structure in each of the openings.
2. The method according to claim 1 , further including:
forming a second hard mask layer over the first hard mask layer, wherein:
the second hard mask layer on the first hard mask layer is made of titanium nitride.
3. The method according to claim 2 , after forming the second hard mask layer, further including:
forming a capping layer on the second hard mask layer.
4. The method according to claim 1 , wherein etching the first hard mask layer further includes;
forming a photoresist layer on the first hard mask layer;
patterning the photoresist layer to have patterns corresponding to positions of the openings; and
etching the first hard mask layer using the photoresist layer as an etching mask.
5. The method according to claim 1 , before forming the to-be-etched layer, further including:
forming an etching barrier layer on the surface of the substrate.
6. The method according to claim 1 , wherein:
a plurality of the semiconductor devices and electrical interconnection structures are formed inside, or in the surface of the substrate.
7. The method according to claim 1 , wherein:
the first hard mask layer is formed by a chemical vapor deposition process;
a gas source of the chemical vapor deposition process includes SiH 4 , CO 2 and N 2 O;
a flow of SiH 4 is in a range of 10 sccm to 10000 sccm;
a flow of CO 2 is in a range of 10 sccm to 10000 sccm;
a flow of N 2 O is in a range of 10 sccm to 10000 sccm;
a pressure of the chemical vapor deposition process is in a range of 0.1 Torr to 10 Torr; and
a power of a plasma source is in a range of 100 W to 5000 W if a plasma source is used in the chemical vapor deposition process.
8. The method according to claim 4 , before forming the photoresist layer, further including:
forming an anti-reflection layer on the first hard mask layer.
9. The method according to claim 1 , wherein forming the conductive structures further includes:
forming a barrier layer on side surfaces and bottom surfaces of the openings;
forming a conductive film on the barrier layer; and
polishing the conductive film and the barrier layer until the surface of the first hard mask layer is exposed.
10. The method according to claim 9 , wherein:
the barrier layer is made of TiN, TaN, Ta, or Ti;
the barrier layer is formed by a physical vapor deposition process;
the conductive film is made of Cu, W, or Al; and
the conductive film is formed by a physical vapor deposition process or an electrochemical plating process.
11. The method according to claim 1 , wherein:
the openings are formed by an anisotropic dry etching process.
12. The method according to claim 1 , wherein:
a solution of the wet chemical cleaning process is a diluted hydrogen fluoride solution; and
a water to hydrogen fluoride ratio of the diluted hydrogen fluoride solution is in a range of 300:1 to 1000:1.
13. The method according to claim 5 , wherein:
the etching barrier layer is made of silicon oxynitride.
14. A semiconductor structure, comprising:
a substrate;
a to-be-etched layer made of a porous low-K dielectric material including boron nitride formed on one surface of the substrate;
a first hard mask layer made of nitrogen-doped silicon oxycarbide (SiCO(N)) formed directly on the to-be-etched layer; and
a plurality of conductive structures formed in the to-be-etched layer and the first hard mask layer,
wherein the conductive structures are formed by:
etching the first hard mask layer to have same patterns corresponding to positions of subsequently formed a plurality of openings;
forming the plurality of openings through an entire thickness of the to-be-etched layer using the first hard mask layer as an etching mask;
etching and cleaning a bottom surface of the openings along with side surfaces of both the to-be-etched layer and the first hard mask layer in the openings by a wet chemical cleaning process, to level the side surfaces of both the to-be-etched layer and the first hard mask layer with each other in the openings, wherein an etching rate of a solution of the wet chemical cleaning process to the first hard mask layer and an etching rate of the solution of the wet chemical cleaning process to the to-be-etched layer is substantially same;
after the etching and cleaning step, forming a barrier layer to cover side surfaces and bottom surfaces of the openings;
forming a conductive film on the barrier layer to fill up the trenches; and
polishing the barrier layer and the conductive film until the surface of the first hard mask layer is exposed.
15. The semiconductor structure according to claim 14 , wherein:
the to-be-etched layer is made of porous low dielectric constant material; and
the dielectric constant of the low dielectric constant material is lower than 2.6.
16. The semiconductor structure according to claim 14 , wherein:
the conductive structures are made of Cu, W, or Al; and
the barrier layer is made of TiN, TaN, Ta, or Ti.
17. The semiconductor structure according to claim 14 , wherein:
a plurality of semiconductor structures and electrical interconnection structures are formed inside or in the surface of the substrate.
18. The semiconductor device according to claim 14 , wherein:
the first hard mask layer is formed by a chemical vapor deposition process; and
the conductive film is formed by a physical vapor deposition process or an electrical chemical plating process.
19. The semiconductor device according to claim 14 , wherein:
the first hard mask layer is etched by an anisotropic dry etching process to form the openings.