Spacer lithography

1. A method of fabricating a semiconductor device, the method comprising:

forming a first mask pattern over a target layer;

forming a cross-linkable layer over the first mask pattern;

forming a cross-linked spacer between the first mask pattern and the cross-linkable layer; and

removing sufficient portions of the cross-linkable layer and cross-linked spacer to expose the first mask pattern, leaving remaining portions of the cross-linkable layer; followed by

removing the remaining portions of the cross-linkable layer and the first mask layer to form a second mask pattern comprising remaining portions of the cross-linked spacer.

2. The method according to claim 1 , further comprising etching a pattern in the target layer through the second mask pattern.

3. The method according to claim 1 , comprising forming the cross-linked spacer at a thickness of less than 20 nm.

4. The method according to claim 1 , wherein the cross-linkable layer comprises a material capable of undergoing a cross-linking reaction in the presence of an acid.

5. The method according to claim 1 , comprising chemically removing sufficient portions of the cross-linkable layer and cross-linked spacer to expose the first mask pattern.

6. The method according to claim 2 , where the target layer comprises a conductive or semiconductive layer.

7. The method according to claim 6 , comprising etching to form gate electrodes.

8. The method according to claim 4 , wherein:

the first mask pattern comprises a material capable of generating an acid.

9. The method according to claim 8 , comprising generating an acid in the first mask pattern after forming the cross-linkable layer.

10. The method according to claim 9 , comprising generating the acid by irradiation or heating.

11. The method according to claim 9 , comprising heating to diffuse the acid toward the cross-linkable material to form the cross-linked spacer.

12. The method according to claim 5 , comprising removing sufficient portions of the cross-linkable layer and cross-linked spacer to expose the first mask pattern by a timed etching technique.

13. A method of fabricating a semiconductor device, the method comprising:

forming a first photoresist mask pattern over a target layer, the first photoresist mask pattern having upper and side surfaces and comprising a material capable of generating an acid;

forming a cross-linkable layer, comprising a material capable of undergoing a cross-linking reaction in the presence of an acid, on the first photoresist mask pattern;

generating an acid in the first photoresist mask pattern by heating or irradiation;

heating to diffuse the acid to the cross-linkable layer to form a cross-linked spacer on the upper and side surfaces of the first photoresist mask pattern;

removing sufficient portions of the cross-linkable layer to expose the cross-linked spacer on the upper surfaces of the first photoresist mask pattern, leaving remaining portions of the cross-linkable layer; followed by

removing the exposed cross-linked spacer from the upper surfaces of the first photoresist mask pattern, leaving the cross-linked spacer on the side surfaces of the first photoresist mask pattern; followed by

removing the remaining portions of the cross-linkable layer and removing the first photoresist mask pattern to form a second mask comprising the cross-linked spacer previously on the side surfaces of the first photoresist mask layer; and

etching the underlying target layer using the second mask pattern.

14. The method according to claim 13 , comprising:

etching to remove the cross-linkable layer, cross-linked spacer layer from the upper surfaces of the first photoresist mask layer, and the first photoresist mask layer.

15. A method of fabricating a semiconductor device, the method comprising:

forming a first mask pattern over a target layer, the first mask pattern comprising a first organic material;

forming a layer comprising a second organic material capable of undergoing a cross-linking reaction in the presence of an acid;

forming and diffusing an acid to the second organic material to cross-link a portion thereof to form a cross-linked spacer on the first mask pattern;

etching to remove a sufficient portion of the second organic material and cross-linked spacer sufficient to expose the first mask pattern, leaving remaining portions of the second organic material; and

etching to remove the remaining portions of the second organic material and the first mask pattern to form a second mask pattern comprising remaining portions of the cross-linked spacer.

16. The method according to claim 15 , wherein the first organic material is capable of generating an acid, the method comprising:

forming the acid by irradiating the first organic material; and

heating to diffuse the acid.

17. The method according to claim 16 , wherein:

the first organic material comprises a novolac resin, a napthoquinonediazde-based photo sensitive agent and a cholo-methyl-triazine acid generator, or a polyhydroxy-styrene derivative and an onium salt.

18. The method according to claim 17 , wherein the second organic material is a water-soluble resin.

19. The method according to claim 17 , comprising forming the acid by treating the first mask pattern with an acid solution.