Method for manufacturing semiconductor device

1. A method for manufacturing a semiconductor device, comprising:

forming a material layer over a semiconductor substrate;

forming a plurality of spacer masks over the material layer;

patterning the material layer into a plurality of masks below the spacer masks, wherein patterning the material layer comprises an atomic layer etching (ALE) process, wherein the ALE process comprises a plurality of cycles, and each of the cycles comprises:

depositing an etchant material layer over the material layer and the spacer masks by using a mixture of a fluoride-containing gas and an oxide-containing gas, such that a surface layer of the material layer adsorbs elements of the etchant material layer; and

bombarding the surface layer of the material layer after depositing the etchant material layer; and

etching the semiconductor substrate through the masks.

2. The method of claim 1 , wherein the fluoride-containing gas is C 4 F 6 , and the oxide-containing gas is O 2 .

3. The method of claim 1 , further comprises:

forming an etch stop layer over the semiconductor substrate prior to forming the material layer, wherein the etch stop layer has a higher etch resistance to the ALE process than that of the material layer.

4. The method of claim 1 , wherein the spacer masks have a higher etch resistance to the ALE process than that of the material layer.

5. The method of claim 1 , wherein forming the spacer masks comprises:

forming a plurality of mandrels over the semiconductor substrate;

depositing a first spacer layer over the mandrels and the semiconductor substrate; and

patterning the first spacer layer into a plurality of first spacers on opposite sidewalls of the mandrels.

6. The method of claim 5 , wherein forming the spacer masks further comprises:

removing the mandrels from the semiconductor substrate.

7. The method of claim 5 , wherein forming the spacer masks further comprises:

depositing a second spacer layer over the first spacers; and

patterning the second spacer layer into a plurality of second spacers on opposite sidewalls of the first spacers.

8. The method of claim 1 , wherein depositing the etchant material layer is performed such that the etchant material layer is in contact with opposite sidewalls of one of the spacer masks.

9. The method of claim 1 , wherein the material layer is a silicon oxide layer.

10. A method for manufacturing a semiconductor device, comprising:

forming a material layer over a semiconductor substrate;

forming a spacer mask over the material layer, wherein the material layer has a first portion covered the spacer mask and a second portion uncovered by the spacer mask, wherein forming the spacer mask comprises:

forming a mandrel over the material layer;

depositing a spacer layer over the mandrel and the material layer;

etching the spacer layer into the spacer mask on a sidewall of the mandrel; and

removing the mandrel from the material layer;

depositing a first fluorocarbon layer over the material layer and the spacer mask, wherein the second portion of the material layer has a first surface layer in contact with the first fluorocarbon layer;

removing the first surface layer of the second portion of the material layer from the material layer;

after removing the first surface layer of the second portion of the material layer, depositing a second fluorocarbon layer over the material layer and the spacer mask, wherein the second portion of the material layer has a second surface layer in contact with the second fluorocarbon layer;

removing the second surface layer of the second portion of the material layer from the material layer; and

after removing the second surface layer of the second portion of the material layer, etching the semiconductor substrate through the material layer.

11. The method of claim 10 , wherein a top surface of the second portion of the material layer is lower than a top surface of the first portion of the material layer after removing the first surface layer of the second portion of the material layer.

12. The method of claim 10 , wherein depositing the first fluorocarbon layer and depositing the second fluorocarbon layer are performed in a same chamber.

13. The method of claim 10 , wherein depositing the first fluorocarbon layer is performed such that a thickness of the first fluorocarbon layer is less than a height of the spacer mask.

14. The method of claim 10 , wherein forming the mandrel is performed such that the mandrel covers the second portion of the material layer.

15. A method for manufacturing a semiconductor device, comprising:

forming a material layer over a semiconductor substrate;

forming a spacer mask over the material layer, wherein the material layer has a first portion covered the spacer mask and a second portion uncovered by the spacer mask;

performing a plurality of ALE cycles, each of the ALE cycles comprising:

conformally depositing an etchant material layer over the material layer and the spacer mask; and

bombarding the material layer after conformally depositing the etchant material layer; and

after the ALE cycles, etching the semiconductor substrate through the material layer.

16. The method of claim 15 , wherein conformally depositing the etchant material layer and bombarding the material layer are performed in a same chamber.

17. The method of claim 16 , wherein each of the ALE cycles further comprises:

purging the chamber after conformally depositing the etchant material layer and prior to bombarding the material layer.

18. The method of claim 16 , wherein each of the ALE cycles further comprises:

purging the chamber after bombarding the material layer.

19. The method of claim 15 , wherein conformally depositing the etchant material layer is performed with a first time duration, and bombarding the material layer is performed with a second time duration longer than the first time duration.

20. The method of claim 15 , wherein conformally depositing the etchant material layer is performed with a first bias power, and bombarding the material layer is performed with a second bias power greater than the first bias power.