Method of etching a high aspect ratio contact
Methods and an etch gas composition for etching a contact opening in a dielectric layer are provided. Embodiments of the method use a plasma generated from an etch gas composed of C 4 F 8 and/or C 4 F 6 , an oxygen source, and a carrier gas in combination with tetrafluoroethane (C 2 F 4 ) or a halofluorocarbon analogue of C 2 F 4 .
1. A method of etching an opening in a dielectric layer, comprising:
forming a plasma etching gas from C 4 F 6 , C 4 F 8 or a mixture of C 4 F 6 and C 4 F 8 , an oxygen source gas, an inert gas, and C 2 F 4 ; and
etching the opening through the dielectric layer to an underlying substrate with the plasma etching gas while depositing polymer material to form and maintain a conformal polymer layer at a thickness effective to continually passivate sidewalls of the opening during the etching;
wherein after the etching, the conformal polymer layer remains over the sidewalls.
2. The method of claim 1 , wherein the plasma etching gas comprises C 4 F 6 :C 2 F 4 , C 4 F 8 :C 2 F 4 , or C 4 F 8 and C 4 F 6 :C 2 F 4 at a ratio of about 0.25-1.5:1.
3. The method of claim 1 , wherein the dielectric layer comprises an oxide.
4. The method of claim 1 , wherein the dielectric layer comprises silicon nitride and the plasma etching gas further comprises a hydrofluorocarbon having the general formula C x H y F z where x=1-6, y=1-6 and z=1-6, or a combination thereof.
5. The method of claim 1 , wherein the opening is a contact hole or a trench having an aspect ratio of about 20-30:1.
6. The method of claim 1 , wherein the conformal polymer layer on the sidewalls of the opening has a thickness of about 5-20 Å for the depth profile of the opening.
7. The method of claim 1 , wherein the dielectric is etched at rate of about 3000-6000 Å/minute.
8. The method of claim 1 , wherein the plasma etching gas consists essentially of the gases.
9. The method of claim 1 , wherein forming the plasma etching gas comprises flowing the gases at a flow rate of about 10-100 sccm for C 4 F 6 or C 4 F 8 and at about 50-150 sccm for C 2 F 4 .
10. The method of claim 1 , wherein forming the plasma etch gas comprises flowing C 4 F 6 and C 4 F 8 at a combined flow rate of about 30-100 sccm, and C 2 F 4 at a flow rate of about 50-150 sccm.
11. A method of etching an opening in a dielectric layer, comprising:
forming plasma etching gas from C 4 F 6 , C 4 F 8 or a mixture thereof at a flow rate of about 50-70 sccm, an oxygen source gas at a flow rate of about 20-40 sccm, an inert diluent gas at a flow rate of about 900-1300 sccm, and C 2 F 4 at a flow rate of about 80-100 sccm; and
etching the opening through the dielectric layer to an underlying substrate with the plasma etching gas while depositing polymer material during the etching to form and maintain a conformal polymer layer at a thickness effective to continually passivate sidewalls of the opening during the etching;
wherein after the etching, the conformal polymer layer remains over the sidewalls.
12. A method of etching an opening in a dielectric layer comprising:
applying a plasma etching gas to etch the dielectric layer to an underlying substrate, the plasma etching gas formed from C 4 F 6 , C 4 F 8 or mixture thereof, an oxygen source gas, an inert diluent gas, and a halofluorocarbon selected from the group consisting of C 2 F 4 Br 2 , C 2 F 4 I 2 and CF 2 I 2 ;
wherein a polymer material is deposited during the etching to form and maintain a conformal polymer layer at a thickness effective to continually passivate sidewalls of the opening during etching, and after the etching, the conformal polymer layer remains over the sidewalls.
13. The method of claim 12 , wherein the plasma etching gas is formed by flowing in C 4 F 6 , C 4 F 8 or a mixture thereof at a flow rate of about 10-100 sccm and the halofluorocarbon at a rate of about 50-300 sccm.
14. The method of claim 13 , wherein the plasma etching gas is formed by flowing in C 2 F 4 Br 2 or C 2 F 4 I 2 at a rate of about 50-150 sccm, or CF 2 I 2 at a rate of about 100-300 sccm.
15. The method claim 12 , wherein the plasma etching gas comprises C 4 F 6 :halofluorocarbon, C 4 F 8 :halofluorocarbon or C 4 F 8 and C 4 F 6 :halocarbon at a ratio of about 0.25-1.5:1.
16. The method of claim 12 , wherein the plasma etching gas further comprises an additional fluorocarbon gas having the general formula C x F y where x=1-6 and y=2-8.
17. The method of claim 12 , wherein the dielectric layer comprises silicon nitride, and the plasma etching gas further comprises a hydrofluorocarbon gas having the general formula C x H y F z where x=1-6, y=1-6, and z=1-6, or a mixture thereof.
18. The method Claim of 12 , wherein the plasma etching gas further comprises a hydrofluorocarbon gas having the general formula C x H y F z where x=1-6, y=1-6 and z=1-6.
19. A method of etching an opening in a dielectric layer, comprising:
applying a plasma etching gas comprising at least one of C 4 F 6 and C 4 F 8 , an oxygen source gas, an inert diluent gas, and C 2 F 4 , in amounts effective to form a plasma etching gas to etch the opening through the dielectric layer while depositing a polymer material to form and maintain a conformal polymer layer on sidewalls of the opening at a thickness effective to continually passivate the sidewalls during the etching, wherein after the etching, the conformal polymer layer remains over the sidewalls.
20. The method of claim 19 , wherein the etching gas further comprises an additional fluorocarbon gas having the general formula C x F y where x=1-6 and y=2-8.
21. The method of claim 19 , wherein the etching gas further comprises a hydrofluorocarbon gas having the general formula C x H y F z where x=1-6, y=1-6 and z=1-6, or a mixture thereof.
22. The method of claim 19 , wherein the etching gas consists essentially of the gases.
23. A method of etching an opening in a dielectric layer, comprising:
applying a plasma etching gas consisting essentially of at least one of C 4 F 6 and C 4 F 8 , an oxygen source gas, an inert diluent gas, and a halofluorocarbon selected from the group consisting of C 2 F 4 Br 2 , C 2 F 4 I 2 and CF 2 I 2 , in amounts effective to etch the opening through the dielectric layer while depositing a polymer material to form and maintain a conformal polymer layer on sidewalls of the opening at a thickness effective to continually passivate the sidewalls during the etching, wherein after the etching, the conformal polymer layer remains over the sidewalls.
24. A method of etching an opening in a dielectric layer, comprising:
applying a plasma etching gas consisting essentially of at least one of C 4 F 6 and C 4 F 8 , an oxygen source gas, an inert diluent gas, a halofluorocarbon selected from the group consisting of C 2 F 4 Br 2 , C 2 F 4 I 2 and CF 2 I 2 , and at least one of an additional fluorocarbon gas having the general formula C x F y where x=1-6 and y=2-8 and a hydrofluorocarbon gas having the general formula C x H y F z where x=1-6, y=1-6 and z=1-6,
said gases in amounts effective to etch the opening through the dielectric layer while depositing a polymer material to form and maintain a conformal polymer layer on sidewalls of the opening at a thickness effective to continually passivate the sidewalls during the etching, wherein the conformal polymer layer remains over the sidewalls after the etching.
25. The method of claim 1 , further comprising, after the etching, removing the conformal polymer layer.
26. The method of claim 25 , wherein the removing is conducted by a dry etch process.
27. The method of claim 26 , wherein the dry etch process comprises an oxygen plasma ashing step.
28. The method of claim 25 , wherein the removing is conducted by a wet etch process.