Method of forming target patterns
A method of forming target patterns is disclosed. A substrate with multiple fins is provided. A plurality of mask patterns is formed across the fins and in at least a part of non-target areas. Target patterns are formed respectively in trenches between the mask patterns. The mask patterns are removed. With the disclosed method, the target patterns can be formed with substantially equal thickness. In the case that the target patterns are dummy gates, the conventional defects such as dummy gate residues or gate trench widening caused by uneven thicknesses are not observed upon the dummy gate removal step.
1. A method of forming target patterns, comprising:
providing a substrate with multiple fins;
forming a plurality of mask patterns across the fins and in at least a part of non-target areas;
forming target patterns respectively in trenches between the mask patterns; and
removing the mask patterns,
wherein the target patterns are dummy gates.
2. The method of claim 1 , wherein a width of each mask pattern is substantially the same or less than a width of the corresponding non-target area.
3. The method of claim 1 , wherein the mask patterns are formed in all of the non-target areas.
4. The method of claim 1 , wherein the mask patterns are formed only in a part of the non-target areas.
5. The method of claim 4 , wherein the target patterns are partially removed during the step of removing the mask patterns, so that the remaining target patterns are provided in all of target areas.
6. The method of claim 1 , further comprising forming a hard mask layer on the target patterns and on the mask patterns before the step of removing the mask patterns.
7. The method of claim 6 , wherein a portion of the hard mask layer is removed during the step of removing the mask patterns.
8. The method of claim 6 , wherein the hard mask layer is a single layer or a multi-layer structure.
9. The method of claim 1 , wherein the step of forming the target patterns comprises:
forming a target material layer on the substrate filling in the trenches between the mask patterns; and
removing a portion of the target material layer until top surfaces of the mask patterns are exposed.
10. The method of claim 9 , wherein the step of removing the portion of the target material layer comprises performing a chemical mechanical polishing process.
11. The method of claim 10 , wherein a polishing selectivity ratio of the target material layer to the mask patterns is from about 10:1 to 100:1.
12. The method of claim 1 , further comprising forming an interfacial layer on the substrate covering the fins before the step of forming the mask patterns, wherein the mask patterns expose a portion of the interfacial layer.
13. The method of claim 12 , wherein the interfacial layer comprises silicon oxide, silicon nitride or silicon oxynitirde.
14. The method of claim 1 , wherein the trenches between the mask patterns have different widths.
15. The method of claim 1 , wherein the trenches between the mask patterns have substantially the same width.
16. The method of claim 1 , wherein the mask patterns and the target patterns have different polishing selectivities but similar etching selectivities.
17. The method of claim 1 , wherein the mask patterns comprises silicon oxide, silicon nitride, silicon oxynitride or a combination thereof.
18. The method of claim 1 , wherein the target patterns comprises polycrystalline silicon, amorphous silicon, microcrystal silicon or a combination thereof.
19. The method of claim 1 , wherein the fins extend in a first direction, and the mask patterns extend in a second direction different from the first direction.