Multiple Patterning Processes

A method of forming a device, the method comprising:

• forming a mandrel over a layer to be patterned;
• depositing a first etch mask layer over the mandrel;
• using a first anisotropic etching process, etching the first etch mask layer to form a spacer on the mandrel;
• depositing a second etch mask layer over the first etch mask layer and the mandrel;
• using a second anisotropic etching process, etching the second etch mask layer to form a liner over the spacer;
• removing the mandrel to expose an underlying surface of the layer to be patterned;
• using a third anisotropic etching process, etching the spacer and the liner to form an etch mask comprising the first etch mask layer and the second etch mask layer;
• and
• using the etch mask, forming a feature by performing a fourth anisotropic etching process to pattern the layer to be patterned, wherein during the third anisotropic etching process, the first etch mask layer etches at a first rate and the second etch mask layer etches at a second rate, and wherein the first rate is different from the second rate.

A method of forming a device, the method comprising:

• forming a mandrel over a layer to be patterned;
• forming a spacer along sidewalls of the mandrel, wherein the spacer comprises a first sidewall comprising a first material and a second sidewall comprising a second material different from the first material, wherein the first sidewall and the second sidewall are vertical and parallel to each other;
• removing the mandrel after forming the spacer;
• and
• using the spacer as an etch mask, forming a feature in the layer to be patterned using an anisotropic etching process.