Compositions and methods for etching silicon nitride-containing substrates
Described are compositions and methods useful for wet-etching a microelectronic device substrate that includes silicon nitride; the compositions including phosphoric acid, hexafluorosilicic acid, and an amino alkoxy silane, and optionally one or more additional optional ingredients; a wet etching method of a substrate that includes silicon nitride and silicon oxide, that uses a composition as described, can achieve useful or improved silicon nitride etch rate, useful or improved silicon nitride selectivity, a combination of these, and optionally a reduction in particles present at a substrate surface after etching.
1. A composition for use in etching a substrate having a surface comprising silicon nitride (SiN) and silicon oxide, with selectivity for etching the SiN relative to the silicon oxide, the etching composition comprising:
concentrated phosphoric acid in an amount of at least 60 wt % based on the total weight of the etching composition,
hexafluorosilicic acid (HFSA), and
an amino alkoxy silane.
2. The composition of claim 1 comprising:
from 5 to 50,000 parts per million (ppm) hexafluorosilicic acid (HFSA), and
from 20 to 10,000 ppm amino alkoxy silane.
3. The composition of claim 1 , wherein the amino alkoxy silane has the formula:
Si(R1)(R2)(R3)(R4)
wherein each of R1, R2, R3, and R4 is an alkyl group, an alkylamine group, an alkoxy, or a hydroxyl group, at least one of R1, R2, R3, and R4 is an alkoxy or hydroxyl group, and at least one of R1, R2, R3, and R4 is an alkylamine group.
4. The composition of claim 3 wherein each of R1, R2, R3, and R4 is:
an alkylamine group having a formula:
—CH 2 ) x NW 2 wherein x is in a range from 1 to 12, or
—(CH 2 ) x1 —NW—(CH 2 ) x2 —NW— . . . (CH 2 ) xn —NW 2 wherein W equals H or a CH 3 group; x1, x2, . . . xn are in the range of 1-12, and n≤100,
an alkoxy group having a formula —O(CH 2 ) y CH 3 wherein y is in a range from 1 to 6,
a hydroxyl group, or
an alkyl group having a formula —(CH 2 ) z CH 3 where z is in the range from 1 to 18.
5. The composition of claim 1 , wherein the amino alkoxy silane is (3-aminopropyl)triethoxysilane (APTES), (3-aminopropyl)trimethoxysilane (APTMSAS), (3-aminopropyl)silane triol, [N-(6-aminohexyl)aminopropyltrimethoxysilane, (AHAPTES), or a combination thereof.
6. The composition of claim 1 further comprising a carboxylic acid compound.
7. The composition of claim 6 , wherein the carboxylic acid is acetic acid, glutaric acid, or a combination thereof.
8. The composition of claim 6 comprising from 0.01 to 10 weight percent carboxylic acid compound based on total weight composition.
9. The composition of claim 1 , further comprising an alkylamine compound.
10. The composition of claim 9 , wherein the alkylamine compound is a primary alkylamine.
11. The composition of claim 9 , wherein the alkylamine compound is octylamine, decylamine, or a combination thereof.
12. The composition of claim 9 comprising from 5 to 10,000 ppm alkylamine compound.
13. The composition of claim 1 further comprising dissolved silica or a soluble silicon-containing compound.
14. The composition of claim 13 comprising from about 5 to 10,000 parts per million dissolved silica or soluble silicon-containing compound based on total weight of the composition.
15. The composition of claim 1 further comprising not more than 50 percent water by weight, including water from all sources.
16. The composition of claim 1 further comprising an organic solvent.
17. The composition of claim 16 , wherein the organic solvent is tetraethylene glycol dimethyl ether, sulfolane, or a combination thereof.
18. The composition of claim 16 comprising from 1 to 20 weight percent organic solvent based on total weight of the composition.
19. The composition of claim 1 further comprising a surfactant.
20. A method of etching a substrate having a surface comprising silicon nitride (SiN) and silicon oxide, with selectivity for etching the SiN relative to the silicon oxide, the method comprising:
providing an etching composition comprising:
concentrated phosphoric acid in an amount of at least 60 wt % based on the total weight of the etching composition,
hexafluorosilicic acid (HSFA), and
an amino alkoxy silane,
providing a substrate having a surface that includes silicon nitride and silicon oxide, and
contacting the substrate with the composition at conditions to remove SiN from the surface.