Method of etching a porous dielectric material

Patent metadata

Field	Value
Publication number	US-10062602-B2
Application number	US-201314142124-A
Country	US
Kind code	B2
Filing date	Dec 27, 2013
Priority date	Dec 28, 2012
Publication date	Aug 28, 2018
Grant date	Aug 28, 2018

Abstract

The invention relates to a method of etching a layer of porous dielectric material, characterized in that the etching is performed in a plasma formed from at least one silicon-based gas mixed with oxygen (O2) and/or nitrogen (N2) so as to grow a passivation layer all along said etching, at least on flanks of the layer of porous dielectric material and wherein the silicon-based gas is taken from all the compounds of the type SixHy for which the ratio x/y is equal or greater than 0.3 or is taken from all the compounds of the following types: SixFy and SixCly, where x is the proportion of silicon (Si) in the gas and y is the proportion of fluorine (F) or chlorine (Cl) or hydrogen (H) in the gas.

First claim

The invention claimed is:

1. A method of etching a layer of porous dielectric material formed on an underlying layer, comprising:
etching the layer of porous dielectric material to expose the underlying layer by uninterrupted etching in a plasma formed from at least one silicon-based gas mixed with oxygen (O 2 ) and/or nitrogen (N 2 ); and
growing, during said etching, a passivation layer at least on flanks of etched portions of the layer of porous dielectric material,
wherein the at least one silicon-based gas is taken from
a compound of a type consisting of Si x F y , or
a compound of a type consisting of Si x Cl y ,
where x is the proportion of silicon (Si) in the gas and y is the proportion of fluorine (F) or chlorine (Cl) in the gas, and

wherein during said etching, the layer of porous dielectric material is maintained at a temperature between 40° C. and 100° C.

2. The method according to claim 1 , wherein the plasma also comprises argon (Ar) or helium (He).

3. The method according to claim 1 , further comprising modifying at least one parameter of the following parameters to adjust an inclination of the flanks:
concentration of nitrogen and/or oxygen in said plasma formed from the at least one silicon-based gas mixed with oxygen (O 2 ) and/or nitrogen (N 2 ), and
temperature of the layer of porous dielectric material.

4. The method according to claim 1 , further comprising modifying at least one parameter of the following parameters to adjust a thickness of the passivation layer:
concentration of nitrogen and/or oxygen in said plasma formed from the at least one silicon-based gas mixed with oxygen (O 2 ) and/or nitrogen (N 2 ), and
temperature of the layer of porous dielectric material.

5. The method according to claim 1 , further comprising removing the passivation layer after the etching and the growing, the removing comprising wet etching to fully dissolve the passivation layer.

6. The method according to claim 5 , wherein the wet etching comprises applying a solution based on hydrofluoric acid (HF).

7. The method according to claim 1 , wherein the layer of porous dielectric material is silsesquioxane from a formula (R—SiO 3/2 )n, where R is a methyl group (—CH3) or a hydrogen atom (—H) and n is an even integer.

8. The method according to claim 1 , wherein the layer of porous dielectric material is a porous silicon oxide doped with carbon and hydrogen (SiOCH).

9. The method according to claim 1 , further comprising, before the etching, providing a mask surmounting the layer of the porous dielectric material, the mask having at least one pattern, and then performing the etching through the mask to transfer the pattern into the etched layer of the porous dielectric material.

10. The method according to claim 9 , wherein the mask is made from silicon oxide (SiO 2 ), silicon nitride (SiN), or dense SiOCH.

11. The method according to claim 9 ,
wherein the porous dielectric material is porous SiOCH, and
wherein the mask is made from silicon oxide (SiO 2 ), silicon nitride (SiN), or dense SiOCH, and has a thickness greater than one fifth of a thickness of the layer of the porous dielectric material.

12. The method according to claim 9 ,
wherein the mask has a bottom face in contact with the layer of the porous dielectric material and a top face opposite to the bottom face, and
wherein said top face is in contact with an etching solution during the etching through the mask.

13. The method according to claim 9 , wherein the mask has a thickness such that the mask is not entirely consumed during the etching.

14. The method according to claim 9 , wherein the mask is made of a metal.

15. The method according to claim 9 , further comprising:
before the providing of the mask, providing a stop layer under the layer of the porous dielectric material, the stop layer being configured to stop the etching;
after the etching and the growing, etching the stop layer; and
after the etching of the stop layer, removing the passivation layer.

16. The method according to claim 9 , further comprising:
before the providing of the mask, providing a stop layer under the layer of the porous dielectric material that, when the stop layer is subjected to the plasma during the etching, has an etching rate that is less than an etching rate of the layer of the porous dielectric material, and wherein the stop layer is etched following the etching of the layer of the porous dielectric material using said plasma.

17. The method according to claim 9 , wherein the etching through the at least one pattern of the mask forms at least one trench in the layer of the porous dielectric material, the method further comprising, after the etching of the layer of the porous dielectric material, filling the at least one trench with an electrically conductive material.

18. The method according to claim 17 , wherein the growing includes growing the passivation layer along a length of sidewalls of the at least one trench.

19. The method according to claim 17 , wherein the at least one trench forms an electrical interconnection.

20. The method according to claim 1 ,
wherein, before the etching, the layer of the porous dielectric material covers a gate of a transistor, and
wherein the etching is effected anisotropically in a principal direction parallel to flanks of the gate, so as to remove the layer of the porous dielectric material only outside the flanks of the gate of the transistor in order to form spacers for the gate.

21. The method according to claim 1 , wherein the at least one silicon-based gas is silicon tetrachloride (SiCl 4 ) or silicon tetrafluoride (SiF 4 ).

22. The method according to claim 21 ,
wherein the at least one silicon-based gas includes silicon tetrafluoride (SiF 4 ) in the presence of oxygen (O 2 ), combined with argon (Ar), and
wherein the passivation layer is a silicon oxide (SiO x ).

23. The method according to claim 21 ,
wherein the least one silicon-based gas includes silicon tetrachloride (SiCl 4 ) in the presence of oxygen (O 2 ), combined with argon (Ar), and
wherein the passivation layer is a silicon oxide (SiO x ).

24. The method according to claim 21 ,
wherein the at least one silicon-based gas includes silicon tetrafluoride (SiF 4 ) in the presence of nitrogen (N 2 ), combined with argon (Ar), and
wherein the passivation layer is a silicon nitride (SiN x F y ).

25. The method according to claim 21 ,
wherein the at least one silicon-based gas includes silicon tetrachloride (SiCl 4 ) in the presence of nitrogen (N 2 ), combined with argon (Ar), and
wherein the passivation layer is a silicon nitride (SiN x Cl y ).

26. The method according to claim 21 ,
wherein the at least one silicon-based gas includes silicon tetrafluoride (SiF 4 ) in the presence of nitrogen (N 2 ) and oxygen (O 2 ), combined with argon (Ar), and
wherein the passivation layer is a silicon oxynitride (SiON x F y ).

27. The method according to claim 21 ,
wherein the at least one silicon-based gas includes silicon tetrachloride (SiCl 4 ) in the presence of nitrogen (N 2 ) and oxygen (O 2 ), combined with argon (Ar), and
wherein the passivation layer is a silicon oxynitride (SiON x Cl y ).

28. A method of etching a layer of porous dielectric material, comprising:
etching the layer of porous dielectric material in a plasma formed from at least one s

Assignees

• Commissariat A Lenergie Atomique Et Aux Ene Alt
• Centre Nat Rech Scient
• Applied Materials Inc
• Commissariat Energie Atomique
• Cnrs—Centre National De La Recherche Scient
• Applied Materials Inc

Inventors

• Posseme Nicolas
• Barnola Sebastien
• Joubert Olivier
• Nemani Srinivas
• Vallier Laurent

Classifications

• H10P70/234

  the processing being the formation of vias or contact holes · CPC title

• H10P50/283

  by chemical means · CPC title

• H10P50/73

  using masks for insulating materials · CPC title

• H10W20/0765

  the thin functional dielectric layers being temporary, e.g. sacrificial layers · CPC title

• H10W20/081 Primary

  by forming openings in the dielectric parts · CPC title