Additive to phosphoric acid etchant

Patent metadata

Field	Value
Publication number	US-10913893-B2
Application number	US-201816210569-A
Country	US
Kind code	B2
Filing date	Dec 5, 2018
Priority date	Nov 13, 2018
Publication date	Feb 9, 2021
Grant date	Feb 9, 2021

Abstract

Embodiments of compositions of a wet etchant and additive thereto for selectively etching silicon nitride to silicon oxide are disclosed. In an example, a composition of an additive to a phosphoric acid etchant includes an inhibitor and a dispersant. The inhibitor is absorbable on a surface of silicon oxide and capable of inhibiting etching of the surface of silicon oxide by the phosphoric acid etchant. The dispersant is capable of reacting with a by-product of a reaction between the phosphoric acid etchant and at least one of silicon oxide and silicon nitride and reducing a viscosity of the phosphoric acid etchant.

First claim

What is claimed is:

1. A composition of an additive to a phosphoric acid etchant, comprising:
an inhibitor, comprising a general formula SiR 3 —Cl and a weight concentration greater than 4%, that is absorbable on a surface of silicon oxide and capable of inhibiting etching of the surface of silicon oxide by the phosphoric acid etchant; and
a dispersant comprising a general formula SiR 3 —N and capable of (i) reacting with a by-product of a reaction between the phosphoric acid etchant and at least one of silicon oxide or silicon nitride, and (ii) reducing a viscosity of the phosphoric acid etchant.

2. The composition of claim 1 , wherein the dispersant further comprises a surfactant.

3. The composition of claim 2 , wherein R is a methyl group, a vinyl group, an alkyl group, a phenyl group, an ethyl group, or a propyl group.

4. The composition of claim 2 , The composition of claim 2 , wherein the dispersant comprises an organosilane having the general formula SiR 3 —N and a weight concentration greater than 0.2%.

5. The composition of claim 4 , wherein the weight concentration of the organosilane is greater than 0.3%.

6. The composition of claim 2 , wherein a weight concentration of the surfactant is greater than 0.02%.

7. The composition of claim 6 , wherein the weight concentration of the surfactant is 0.03%.

8. The composition of claim 1 , wherein the viscosity of the phosphoric acid etchant is not greater than a viscosity of phosphoric acid at a same temperature.

9. The composition of claim 8 , wherein the viscosity of the phosphoric acid etchant is not greater than 45 mPa·s at 20° C.

10. The composition of claim 1 , wherein the inhibitor comprises another organosilane having the general formula SiR 3 —Cl.

11. The composition of claim 10 , wherein the other organosilane comprises an organochlorosilane having the general formula SiR 3 —Cl.

12. The composition of claim 11 , wherein R is a methyl group, a vinyl group, an alkyl group, a phenyl group, an ethyl group, or a propyl group.

13. The composition of claim 10 , wherein a weight concentration of the other organosilane is greater than 3%.

14. The composition of claim 1 , wherein an etch rate of the phosphoric acid etchant on the silicon oxide is below 5 Å/h when the weight concentration of the inhibitor is above 5%.

15. A composition of a wet etchant for selectively etching silicon nitride to silicon oxide, comprising:
phosphoric acid;
a first organosilane having the general formula SiR 3 —N and capable of reducing a viscosity of the wet etchant to be no greater than about 45 mPa·s at 20 degrees Celsius;
a surfactant; and
a second organosilane having the general formula SiR 3 —Cl.

16. The composition of claim 15 , wherein the weight concentration of the first organosilane is greater than 0.3%.

17. The composition of claim 15 , wherein the weight concentration of the surfactant is 0.03%.

18. The composition of claim 15 , wherein the weight concentration of the second organosilane is greater than 4%.

19. The composition of claim 15 , wherein the weight concentration of the second organosilane is between 4% and 10%.

20. A method for selectively etching silicon nitride to silicon oxide, comprising:
alternatingly depositing a plurality layers of silicon nitride and a plurality layers of silicon oxide;
etching an opening through the plurality layers of silicon nitride and the plurality layers of silicon oxide;
adding an additive to a wet etchant comprising phosphoric acid, wherein the additive comprises a first organosilane having the general formula SiR 3 —N and a weight concentration greater than 0.3%, a surfactant having a weight concentration of 0.03%, and a second organosilane having the general formula SiR 3 —Cl and a weight concentration greater than 4%; and
applying the etchant with the additive to the plurality layers of silicon nitride and the plurality layers of silicon oxide through the opening.

Assignees

• Yangtze Memory Tech Co Ltd

Inventors

• Xu Rong
• Sun Wenbin
• Su Jie

Classifications

• H10P50/283

  by chemical means · CPC title

• C09K13/06 Primary

  with organic material · CPC title

• C09K15/04

  containing organic compounds · CPC title

• H01L27/11582

  Electricity · mapped topic

• H01L21/31111

  Electricity · mapped topic