Methods for fabricating integrated circuits using improved masks

A method for fabricating an integrated circuit, the method comprising:

• forming a mask overlying a material to be etched comprising:
• forming first sacrificial mandrels having a first width and overlying the material to be etched and defining a pitch distance from a first side of a selected first sacrificial mandrel to a first side of a respective adjacent first sacrificial mandrel;
• forming first hard mask segments overlying the material to be etched and adjacent each first sacrificial mandrel;
• forming second sacrificial mandrels having a second width overlying the material to be etched and adjacent each first hard mask segment and defining a reduced pitch distance from the first side of the selected first sacrificial mandrel to a first side of a respective adjacent second sacrificial mandrel;
• forming second hard mask segments overlying the material to be etched and each second sacrificial mandrel;
• and
• removing the first sacrificial mandrels and the second sacrificial mandrels to form gaps adjacent the first hard mask segments and second hard mask segments, wherein the mask is formed by the first hard mask segments and the second hard mask segments;
• wherein the reduced pitch distance is equal to about one-third of the pitch distance, wherein the first width is equal to about one-sixth of the pitch distance, and/or wherein the second width is substantially equal to the first width;
• and
• etching the material to be etched through the mask.

A method for fabricating an integrated circuit, the method comprising:

• forming first hard mask segments overlying an intermediate layer and a underlying layer;
• forming sacrificial mandrels overlying the intermediate layer and the underlying layer and adjacent each hard mask segment;
• forming second hard mask segments overlying the intermediate layer and the underlying layer and adjacent each sacrificial mandrel;
• removing the sacrificial mandrels;
• forming sidewall spacers surrounding each first hard mask segment and each second hard mask segment;
• removing the first hard mask segments and second hard mask segments;
• etching the intermediate layer using the sidewall spacers as an intermediate mask to form intermediate mandrels;
• forming final spacers surrounding each intermediate mandrel;
• removing the intermediate mandrels;
• and
• etching the underlying layer using the final spacers as a final mask to form final mandrels.