US-12622192-B2 - Methods of selectively etching silicon nitride

Abstract

Embodiments of the present disclosure are directed to selective etching processes. The processes include flowing a precursor comprising one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and an amine or a phosphine, or a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species with a sulfur-containing species, into a semiconductor processing chamber containing a substrate, and forming an activated species of the precursor to etch a substrate. The substrate has a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers. The silicon nitride layers are selectively etched relative to the silicon oxide layers at an etch selectivity of greater than or equal to 500:1.

Inventors

• Doreen Wei Ying Yong
• Tuck Foong Koh
• Mikhail Korolik
• John Sudijono
• Paul E. Gee

Assignees

• APPLIED MATERIALS, INC.

Dates

Publication Date

20260505

Application Date

20230718

Claims (19)

1. 1 . A method of selectively etching silicon nitride relative to silicon oxide, the method comprising: flowing a precursor comprising a mixture of one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, and an amine or a phosphine, into a semiconductor processing chamber containing a substrate, the substrate having a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers; forming an activated species of the precursor; and etching the substrate, wherein the silicon nitride layers are selectively etched relative to the silicon oxide layers and an etching selectivity of silicon nitride to silicon oxide is greater than or equal to 500:1.
2. 2 . The method of claim 1 , wherein the interhalogen comprises one or more of chlorine trifluoride (ClF 3 ), bromine trifluoride (BrF 3 ), bromine pentafluoride (BrF 5 ), iodine trifluoride (IF 3 ), iodine pentafluoride (IF 5 ), iodine monobromide (IBr), or iodine monochloride (ICl).
3. 3 . The method of claim 1 , wherein the halogen-containing species comprises one or more of fluorine (F 2 ), bromine (Br 2 ), chlorine (Cl 2 ), iodine (I 2 ), boron trifluoride (BF 3 ), or boron trichloride (BCl 3 ).
4. 4 . The method of claim 1 , wherein the amine is diethylamine or triethylamine.
5. 5 . The method of claim 1 , wherein the phosphine is an alkylphosphine.
6. 6 . The method of claim 1 , wherein the pseudohalogen species comprises one or more of an isocyano group, a sulfanyl group, a cyanate group, an isocyanate group, a thiocyanate group, or an isothiocyanate group.
7. 7 . The method of claim 1 , wherein flowing the precursor of the mixture of the interhalogen and the amine or the phosphine, the mixture of the halogen-containing species and the amine or the phosphine, or the mixture of the pseudohalogen species and the amine or the phosphine comprises sequentially exposing the substrate to the interhalogen, the halogen-containing species, or the pseudohalogen species, respectively, and the amine or the phosphine.
8. 8 . The method of claim 1 , wherein the semiconductor processing chamber is maintained at a pressure in a range of from 5 millitorr to 100 Torr.
9. 9 . The method of claim 1 , wherein the semiconductor processing chamber is maintained at a temperature of less than or equal to 500° C.
10. 10 . The method of claim 1 , further comprising purging the semiconductor processing chamber with a purge gas.
11. 11 . The method of claim 10 , wherein the purge gas comprises one or more of argon (Ar), helium (He), krypton (Kr), neon (Ne), xenon (Xe), hydrogen (H 2 ), oxygen (O 2 ), or nitrogen (N 2 ).
12. 12 . The method of claim 1 , wherein forming the activated species comprises one or more of a thermal process, generating a plasma of the precursor, or heating the substrate to a temperature of less than or equal to 500° C. using an optical radiation source.
13. 13 . The method of claim 12 , wherein the plasma is generated by one or more of a microwave plasma source, a remote plasma source, an inductively coupled plasma (ICP) source, or a capacitively coupled plasma (CCP) source.
14. 14 . The method of claim 12 , wherein the activated species is generated by UV radiation.
15. 15 . A method of selectively etching silicon nitride relative to silicon oxide, the method comprising: flowing a precursor comprising a mixture of one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, and a sulfur-containing species comprising a disulfide bonded molecule including one or more of Me-S—S-Me (dimethyl disulfide) or (disulfur tetrachloride), into a semiconductor processing chamber containing a substrate, the substrate having a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers; forming an activated species of the precursor; and etching the substrate, wherein the silicon nitride layers are selectively etched relative to the silicon oxide layers.
16. 16 . The method of claim 15 , wherein forming the activated species comprises one or more of a thermal process, forming a plasma of the precursor, or heating the substrate to a temperature of less than or equal to 500° C. using an optical radiation source.
17. 17 . The method of claim 16 , wherein the plasma is generated by one or more of a microwave plasma source, a remote plasma source, an inductively coupled plasma (ICP) source, or a capacitively coupled plasma (CCP) source.
18. 18 . The method of claim 16 , wherein the activated species is generated by UV radiation.
19. 19 . A method of selectively etching silicon nitride relative to silicon oxide, the method comprising: flowing a precursor into a semiconductor processing chamber containing a substrate, the precursor comprising a pseudohalogen species, a mixture of the pseudohalogen species and an amine or a phosphine, or a mixture of the pseudohalogen species and a sulfur-containing species, the pseudohalogen species comprising one or more of an isocyano group, a cyanate group, an isocyanate group, a thiocyanate group, or an isothiocyanate group, the substrate having a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers; forming an activated species of the precursor; and etching the substrate, wherein the silicon nitride layers are selectively etched relative to the silicon oxide layers and an etching selectivity of silicon nitride to silicon oxide is greater than or equal to 500:1.

Description

TECHNICAL FIELD Embodiments of the present disclosure relate to the field of semiconductor manufacturing. More particularly, embodiments of the disclosure relate to selectively etching silicon nitride relative to silicon oxide. BACKGROUND Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes, including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Chemical etching processes typically include chemistries that etch one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials. The fabrication of three-dimensional (3D)-NAND devices includes the formation of alternating silicon oxide (e.g., SiO2) layers and silicon nitride (e.g. Si3N4) layers. After the formation of the stack of alternating layers, the silicon nitride layers are selectively etched to form recesses that are ultimately filled with a conductor (e.g., tungsten). Etch processes may be termed “wet” or “dry” based on the materials used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge. There is a need for improved systems and methods that can be used to produce high quality devices and structures. Currently, a wet etching process is used to selectively remove the silicon nitride layers. However, in the drying process after the wet etching process, the suspended silicon oxide layers may collapse due to surface tension of the liquid. This leads to yield losses. Another issue with wet etching processes is that with future scaling of the 3D-NAND devices, the number of layers of silicon oxide and silicon nitride increases. This is problematic because the liquid etchant will have difficulty filling into a deeper trench. This results in non-uniform etching, such that the etching of the top of the 3D-NAND structure is different than the etching of the bottom of the 3D-NAND structure. Current dry etching techniques also etch silicon and silicon oxide, in addition to silicon nitride, thereby reducing selectivity of such processes. Accordingly, there is a need for improved etch processes that achieve improved etching selectivity. SUMMARY One or more embodiments of the present disclosure are directed to a selective etch method. The selective etch method comprises flowing a precursor comprising one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and an amine or a phosphine, or a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and a sulfur-containing species, into a semiconductor processing chamber containing a substrate. The substrate has a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers. The selective etch method further comprises forming an activated species of the precursor and etching the substrate. The silicon nitride layers are selectively etched relative to the silicon oxide layers. Additional embodiments of the present disclosure are directed to a method of selectively etching silicon nitride relative to silicon oxide. The method comprises flowing a precursor comprising one or more of an interhalogen, a halogen-containing species, a pseudohalogen species, a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and an amine or a phosphine, or a mixture of one or more of the interhalogen, the halogen-containing species, or the pseudohalogen species and a sulfur-containing species, into a semiconductor processing chamber containing a substrate. The substrate has a plurality of alternating layers of silicon oxide and silicon nitride thereon and a trench formed through the plurality of alternating layers. The method further comprises forming an activated species of the precursor and etching the substrate. The silicon nitride layers are selectively etched relative to the silicon ox