Underlayer composition and method of manufacturing a semiconductor device

A method of manufacturing a semiconductor device, comprising:

• forming a photoresist underlayer over a semiconductor substrate,
• wherein the underlayer includes a polymer;
• forming a photoresist layer over the underlayer;
• selectively exposing the photoresist layer and underlayer to actinic radiation;
• decreasing a glass transition temperature (Tg), decreasing a density, or increasing a porosity of a portion of the underlayer selectively exposed to the actinic radiation;
• and
• developing the selectively exposed photoresist layer to form a patterned photoresist layer.

A composition, comprising:

• a polymer, comprising:
• a first main polymer chain;
• a second main polymer chain;
• and
• a photocleavable functional group,
• wherein the first and second main polymer chains are linked by a cross linker,
• the first and second main polymer chains are one or more of a polyhydroxystyrene or an inorganic polymer, and
• the photocleavable functional group is embedded in the first or second main polymer chains, embedded in a side chain of the first and second main polymer chains, or embedded in the cross linker.