Reducing Defects in Patterning Processes

A method comprising:

• forming a mask layer over a target layer;
• performing a first etching step to pattern the mask layer, wherein remaining portions of the mask layer form a first patterned mask layer;
• forming a conformal layer on a top surface and sidewalls of the first patterned mask layer;
• performing a patterning step to pattern the conformal layer and the first patterned mask layer using a same etching mask, wherein remaining portions of the first patterned mask layer form a second patterned mask layer;
• removing remaining portions of the conformal layer;
• etching the target layer using the second patterned mask layer as an etching mask;
• and
• removing the second patterned mask layer.

A method comprising:

• forming a mask layer over a target layer;
• forming a first stacked layer over the mask layer, wherein the first stacked layer comprises:
• a first under layer over the mask layer;
• and
• a first middle layer over the first under layer, wherein the first middle layer comprises an inorganic material;
• patterning the first stacked layer to form a first patterned stack;
• performing a first etching on the mask layer using the first patterned stack as an etching mask;
• removing remaining portions of the first patterned stack;
• forming a conformal layer on a top surface and sidewalls of the mask layer and on exposed surfaces of the target layer;
• forming a second stacked layer over the mask layer, wherein the second stacked layer comprises:
• a second under layer over the mask layer;
• and
• a second middle layer over the second under layer;
• patterning the second stacked layer to form a second patterned stack;
• etching the conformal layer and the mask layer using the second patterned stack as an etching mask;
• and
• etching the target layer using the mask layer as an etching mask.