A patterning stack is provided. The patterning stack includes a bottom anti-reflective coating (BARC) layer over a substrate, a photoresist layer having a first etching resistance over the BARC layer, and a top coating layer having a second etching resistance greater than the first etching resistance over the photoresist layer. The top coating layer includes a polymer having a polymer backbone including at least one functional unit of high etching resistance and one or more acid labile groups attached to the polymer backbone or a silicon cage compound.