Patent ID: 11929254
Assignee: TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD.
Field: Semiconductors (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 9:
10. A method comprising:
depositing a first oxide hard mask layer over a target layer;
depositing a second oxide hard mask layer over and having a different density than the first oxide hard mask layer, wherein a density of the second oxide hard mask layer is at least 1.8 g/cm3;
forming a plurality of mandrels over the second oxide hard mask layer;
forming spacers on sidewalls of the plurality of mandrels;
removing the plurality of mandrels to define openings between the spacers, wherein removing the plurality of mandrels partially etches the second oxide hard mask layer without etching the first oxide hard mask layer;
using the spacers as a mask to pattern the first oxide hard mask layer; and
using the first oxide hard mask layer as a mask to pattern the target layer.