Method for achieving ultra-high selectivity while etching silicon nitride
Methods of selectively etching silicon nitride on a semiconductor substrate by providing silicon to the plasma to achieve high etch selectivity of silicon nitride to silicon-containing materials are provided. Methods involve providing silicon from a solid or fluidic silicon source or both. A solid silicon source may be upstream of a substrate, such as at or near a showerhead of a process chamber, or in a remote plasma generator. A silicon gas source may be flowed to the plasma during etch.
1. A method of etching silicon nitride on a substrate, the method comprising:
(a) introducing a fluorinating gas to a plasma generator and igniting a plasma to form fluorine-containing etching species; and
(b) providing silicon to the plasma from a solid silicon source, the solid silicon source having only the function of providing silicon to the plasma; and
(c) exposing the silicon nitride to the fluorine-containing etching species to selectively etch the silicon nitride relative to other silicon-containing materials on the substrate.
2. The method of claim 1 , wherein the solid silicon source is provided to the plasma upstream of the substrate.
3. The method of claim 1 , wherein the solid silicon source is provided to the plasma in a remote plasma generator.
4. The method of claim 1 , wherein the solid silicon source is provided to the plasma between the substrate and a showerhead of a chamber housing the substrate.
5. The method of claim 1 , wherein the solid silicon source is provided to the plasma at or near a showerhead of a chamber housing the substrate.
6. The method of claim 1 , wherein the solid silicon source comprises two or more silicon sources.
7. The method of claim 1 , wherein the solid silicon source is attached to a wall of the plasma generator.
8. The method of claim 1 , wherein the fluorinating gas is selected from the group consisting of F 2 , SF 6 , CF 4 , CHF 3 , CH 2 F 2 , NF 3 , and combinations thereof.
9. The method of claim 1 , wherein the solid silicon source is a silicon-containing compound selected from the group consisting of quartz, silicon, silicon germanium, silicon carbide, and silicon oxide.
10. The method of claim 1 , wherein the solid silicon source is a ring.
11. The method of claim 1 , wherein the solid silicon source is a rod.
12. The method of claim 1 , wherein (b) further comprises providing additional silicon to the plasma from a fluidic silicon source.
13. The method of claim 12 , wherein the fluidic silicon source is a non-fluorinating fluidic silicon source.
14. The method of claim 13 , wherein the non-fluorinating fluidic silicon source is selected from the group consisting of silane, disilane, tetraethyl orthosilicate, and tetramethyl silane.
15. The method of claim 13 , wherein the non-fluorinating fluidic silicon source is a silicon-containing gas and the flow rate of the silicon-containing gas to a process chamber housing the substrate is less than about 10% of the total flow rate of gases flowed into the process chamber.
16. The method of claim 12 , wherein at least about 0.5% of a total flow of gases by volume introduced to the plasma is the fluidic silicon source.
17. The method of claim 13 , wherein the fluidic silicon source is a gaseous silicon source.
18. The method of claim 13 , wherein the fluidic silicon source is a liquid silicon source.
19. The method of claim 13 , wherein the fluorine-containing etching species reacts with the fluidic silicon source to deplete an amount of atomic fluorine present in the plasma.
20. The method of claim 1 , further comprising introducing one or more oxidant gases during (b).