Fin patterns with varying spacing without fin cut
Methods of forming semiconductor fins include forming first spacers on a first sidewall of each of multiple mandrels using an angled deposition process. A second sidewall of one or more of the mandrels is masked in a finless region. Second spacers are formed on a second sidewall of all unmasked mandrels. Semiconductor fins are formed from a substrate using the first and second spacers as a pattern mask.
1. A method of forming semiconductor fins, comprising:
forming first spacers on a first sidewall of each of a plurality of mandrels using an angled deposition process;
masking a second sidewall of one or more of the plurality of mandrels in a finless region;
forming second spacers on a second sidewall of all unmasked mandrels;
forming said semiconductor fins from a substrate using the first and second spacers as a pattern mask.
2. The method of claim 1 , wherein forming the first spacers on the first sidewalls comprises oxidizing the first sidewalls using a gas cluster ion beam.
3. The method of claim 2 , wherein the mandrels comprise amorphous silicon and the gas cluster ion beam comprises oxygen.
4. The method of claim 2 , wherein the gas cluster ion beam has an angle relative to the substrate under the mandrels between about 10° and about 80°.
5. The method of claim 1 , wherein forming the second spacers on the second sidewalls comprising oxidizing the second sidewalls using a gas cluster ion beam.
6. The method of claim 1 , wherein forming the second spacers on the second sidewalls comprises an isotropic process.
7. The method of claim 1 , further comprising anisotropically etching spacer material from horizontal surfaces of the mandrels after unmasking the second sidewall of the one or more of the plurality of mandrels.
8. The method of claim 1 , wherein forming the semiconductor fins comprises forming no semiconductor fins in a region that was masked.
9. The method of claim 1 , wherein no semiconductor fin is removed after formation of the semiconductor fins.
10. The method of claim 1 , wherein masking the second sidewall of the one or more of the plurality of mandrels comprises forming a mask that directly contacts the second sidewall of the one or more of the plurality mandrels as well as a first spacer on an adjacent mandrel.
11. The method of claim 1 , wherein the substrate comprises a nitride pad layer that is directly on a semiconductor layer.