Multiple spacer steps for pitch multiplication
Multiple pitch-multiplied spacers are used to form mask patterns having features with exceptionally small critical dimensions. One of each pair of spacers formed around a plurality of mandrels is removed and alternating layers, formed of two mutually selectively etchable materials, are deposited around the remaining spacers. Layers formed of one of the materials are then etched, leaving behind vertically-extending layers formed of the other of the materials, which form a mask pattern. Alternatively, instead of depositing alternating layers, amorphous carbon is deposited around the remaining spacers followed by a plurality of cycles of forming pairs of spacers on the amorphous carbon, removing one of the pairs of spacers and depositing an amorphous carbon layer. The cycles can be repeated to form the desired pattern. Because the critical dimensions of some features in the pattern can be set by controlling the width of the spaces between spacers, exceptionally small mask features can be formed.
1. A method for forming an integrated circuit, comprising:
forming a first plurality of spacers of a first material;
covering the spacers by depositing a blanket layer of a second material on the spacers, wherein a thickness of the blanket layer of the second material is less than a height of the spacers;
depositing a layer of a third material on the blanket layer of the second material, at least a portion of the layer of the third material disposed on a same horizontal plane as the spacers; performing a spacer etch on the layer of the third material to form a second plurality of spacers from the layer of the third material; and
removing parts of the layer of the second material immediately adjacent the first plurality of spacers.
2. The method claim 1 , further comprising depositing a layer of a fourth material on the layer of the third material.
3. The method claim 2 , further comprising depositing a layer of a fifth material on the layer of the fourth material.
4. The method claim 3 , wherein each of the second material, the third material, the fourth material and the fifth material are deposited by an atomic layer deposition.
5. The method claim 3 , further comprising performing a planarization process to expose surfaces of each of the blanket layer of the second material, and the layer of the fourth material.
6. The method claim 5 , wherein performing the planarization process further exposes each of the first plurality of spacers, the layer of the third material and the layer of the fifth material.
7. The method claim 5 , wherein exposing surfaces comprises performing a chemical mechanical polishing process.
8. The method claim 5 , further comprising selectively etching exposed surfaces of the blanket layer of the second material and the layer of the fourth material to form a mask pattern.
9. The method claim 8 , further comprising transferring the mask pattern to a layer of material underlying the first plurality of spacers.
10. The method claim 8 , further comprising transferring the mask pattern to a substrate underlying the first plurality of spacers.
11. The method claim 3 , wherein the first material, the third material and the fifth material are each selectively etchable relative to the second and the fourth materials.
12. The method claim 11 , wherein the first material, the third material and the fifth material are the same material.
13. The method claim 12 , wherein the second material is the same material as the fourth material.
14. The method claim 1 , wherein a critical dimension of each of the first and the second plurality of spacers is about 25 nm or less.
15. The method claim 14 , wherein a lateral separation between each of the spacers and features formed of the third material is about 25 nm or less, wherein the features are formed after removing parts of the blanket layer of the second material.
16. A method for forming an integrated circuit, comprising:
forming a plurality of spacers of a first material, wherein forming the plurality of the spacers comprises:
forming a plurality of mandrels;
forming an initial set of spacers on sidewalls of the mandrels; and
selectively removing some of the initial set of spacers to leave a remainder of the initial set of spacers on only one sidewall of each of the plurality of mandrels, the remainder of the initial set of spacers constituting the plurality of spacers of the first material;
covering the plurality of spacers by depositing a layer of a second material on the plurality of spacers, wherein a thickness of the layer of the second material is less than a height of the plurality of spacers;
depositing a layer of a third material on the layer of the second material; and
removing parts of the layer of the second material immediately adjacent the plurality of spacers.