Method for positioning spacers in 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 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 mandrels on a first level over a substrate;
forming a first plurality of mask lines along sidewalls of the first plurality of mandrels;
forming a second plurality of mandrels on a second level over the first level;
forming a second plurality of mask lines along sidewalls of the second plurality of mandrels, the second plurality of mask lines elongated generally parallel to the first plurality of the first and second pluralities of mask lines;
selectively removing, relative to the mask lines, portions of exposed material on the first and second levels to form a pattern defined by mask lines of the first and the second pluralities of mask lines;
transferring the pattern to an underlying material, wherein transferring the pattern to the underlying material comprises transferring the pattern to an amorphous carbon layer; and
subsequently transferring the pattern to the substrate.
2. The method of claim 1 , wherein forming the first plurality of mask lines comprises:
blanket depositing spacer material on the first plurality of mandrels; and
directionally etching the deposited spacer material to form the first plurality of mask lines, the mask lines comprising the etched spacer material.
3. The method of claim 2 , wherein forming the second plurality of mask lines comprises:
blanket depositing spacer material on the second plurality of mandrels; and
directionally etching the deposited spacer material on the second level to form the second plurality of mask lines, the mask lines comprising the etched spacer material on the second level.
4. The method of claim 1 , wherein selectively removing portions of exposed material on the first and second levels comprises:
selectively removing the second plurality of mandrels, thereby exposing portions of the first plurality of mandrels; and
directionally etching the exposed portions of the first plurality of mandrels.
5. A method for forming an integrated circuit, comprising:
forming a first plurality of mandrels on a first level over a substrate;
forming a first plurality of mask lines along sidewalls of the first plurality of mandrels, wherein forming the first plurality of mask lines comprises:
blanket depositing spacer material on the first plurality of mandrels; and
directionally etching the deposited spacer material to form the first plurality of mask lines, the mask lines comprising the etched spacer material;
selectively removing the first plurality of mandrels after directionally etching the deposited spacer material to form the first plurality of mask lines; and
subsequently depositing a sacrificial material between the mask lines of the first plurality of mask lines before forming the second plurality of mask lines;
forming a second plurality of mandrels on a second level over the first level;
forming a second plurality of mask lines along sidewalls of the second plurality of mandrels, the second plurality of mask lines elongated generally parallel to the first plurality of mask lines;
selectively removing, relative to the mask lines, portions of exposed material on the first and second levels to form a pattern defined by mask lines of the first and the second pluralities of mask lines;
transferring the pattern to an underlying material; and
subsequently transferring the pattern to the substrate.
6. A method for forming an integrated circuit, comprising:
forming a first plurality of mandrels on a first level over a substrate;
forming a first plurality of mask lines along sidewalls of the first plurality of mandrels;
forming a second plurality of mandrels on a second level over the first level;
forming a second plurality of mask lines along sidewalls of the second plurality of mandrels, the second plurality of mask lines elongated generally parallel to the first plurality of mask lines;
forming a third plurality of mandrels on a third level over the second level;
forming a third plurality of mask lines along sidewalls of the third plurality of mandrels, the third plurality of mask lines elongated generally parallel to the first plurality of mask lines;
selectively removing exposed portions of the third plurality of mandrels;
selectively removing, relative to the mask lines, portions of exposed material on the first and second levels to form a pattern defined by mask lines of the first, second, and third pluralities of mask lines;
transferring the pattern to an underlying material; and
subsequently transferring the pattern to the substrate.
7. A method for forming an integrated circuit, comprising:
forming mask lines on a first level over a substrate, the mask lines on the first level separated by sacrificial material;
forming mask lines on a second level over the first level, the mask lines on the second level elongated generally parallel to the mask lines on the first level and separated by openings exposing portions of the sacrificial material;
selectively removing the exposed portions of the sacrificial material to form a pattern defined by the mask lines on the first and second levels; and
transferring the pattern to the substrate.
8. The method of claim 7 , wherein forming mask lines on the second level comprises:
defining the mask lines on the second level along sidewalls of a plurality of mandrels on the second level; and
removing material forming the mandrels to form the openings.
9. The method of claim 7 , wherein forming mask lines on the second level comprises isotropically etching the mask lines before selectively removing the exposed portions of the sacrificial material.
10. The method of claim 7 , wherein the sacrificial material extends between and over the mask lines on the first level.
11. The method of claim 10 , wherein the sacrificial material comprises amorphous carbon.
12. The method of claim 7 , wherein features in the pattern have a critical dimension of about 50 nm or less.
13. The method of claim 7 , wherein transferring the pattern to the substrate defines interconnects in an array region of the integrated circuit.
14. A method for forming an integrated circuit, comprising:
forming a mask comprising a pattern over a substrate, the mask comprising:
mask lines on an upper level;
mask lines on a lower level, the mask lines on the lower and upper levels elongated in a same direction;
transferring the pattern to an underlying layer of material to form a patterned underlying layer, wherein the underlying layer of material comprises amorphous carbon; and
subsequently etching the substrate through the patterned underlying layer.
15. The method of claim 14 , wherein forming the mask comprises depositing a planarization material around the mask lines on the lower level, wherein the mask lines on the upper level are disposed over the planarization material.
16. A method for forming an integrated circuit, comprising:
forming a mask comprising a pattern over a substrate, the mask comprising:
mask lines on an upper level; and
mask lines on a lower level, the mask lines on the lower and upper levels elongated in a same direction, wherein forming a mask comprises:
forming lower level mandrels by:
forming a carbon-containing layer on the lower level; and
patterning the carbon-containing layer to define the lower level mandrels in the carbon-containing layer; and
forming the mask lines on the lower level by:
blanket depositing a spacer material on the lower level mandrels; and
directionally etching the spacer material to define spacers along the sidewalls of the lower level mandrels, wherein the spacers are the mask lines on the lower level;
transferring the pattern to an underlying layer of material to form a patterned underlying layer; and
subsequently etching the substrate through the patterned underlying layer.
17. A method for forming an integrated circuit, comprising:
forming a mask comprising a pattern over a substrate, the mask comprising:
mask lines on an upper level; and
mask lines on a lower level, the mask lines on the lower and upper levels elongated in a same direction,
wherein forming the mask comprises depositing a planarization material around the mask lines on the lower level, wherein the mask lines on the upper level are disposed over the planarization material;
forming a hard mask over the planarization material;
transferring the pattern to an underlying layer of material to form a patterned underlying layer; and
subsequently etching the substrate through the patterned underlying layer.
18. A method for forming an integrated circuit, comprising:
forming a mask comprising a pattern over a substrate, the mask comprising:
mask lines on an upper level; and
mask lines on a lower level, the mask lines on the lower and upper levels elongated in a same direction,
wherein forming the mask comprises:
depositing a planarization material around the mask lines on the lower level, wherein the mask lines on the upper level are disposed over the planarization material;
forming upper level mandrels by:
forming an upper level carbon-containing layer on the upper level; and
patterning the upper level carbon-containing layer to define the upper level mandrels in the carbon-containing layer; and
forming the mask lines on the upper level by:
blanket depositing a spacer material on the upper level mandrels; and
directionally etching the spacer material to define spacers along the sidewalls of the upper level mandrels, wherein the spacers are the mask lines on the upper level;
transferring the pattern to an underlying layer of material to form a patterned underlying layer; and
subsequently etching the substrate through the patterned underlying layer.