Patent ID: 9741614
Date: 2017-08-22
CPC Classifications: H01L

Claim:
1. A method of forming trenches and a via by self-aligned double patterning, comprising: providing a dielectric layer covered by a first mask and a second mask, wherein the first mask has a first stress, and the second mask has a second stress, wherein the first stress and the second stress are opposite in sign; forming at least two mandrels on the second mask; forming two spacers respectively at two sidewalls of each of the mandrels; removing the mandrels; patterning the second mask by taking the spacers as a first hard mask to form a plurality of recesses; removing the spacers; forming a third mask covering the second mask, wherein the third mask comprises a via pattern; forming a via in the dielectric layer by taking the third mask as a second hard mask; removing the third mask; and forming a plurality of trenches in the dielectric layer by taking the second mask as a third hard mask.