Interaction of Radiation with Resists

The interaction of exposure radiation with amorphous solid films of resists and their constituents leads to distinct photophysical and photochemical processes that in turn underlie the basis of the contrast between the exposed and the unexposed sections of the resist film. A short section of this chapter is therefore devoted to the rudiments of photochemistry and photophysics of amorphous solid resist films. We can only provide here the most basic information required for understanding the subject.  

It is necessary to introduce some terminology here. When the radiation-sensitive components of resists— the resins and components—are irradiated, they can absorb the energy and in turn get excited. It is the excited-state form of the radiation-sensitive components of the resist that plays the central role in these processes. These excited states of the molecules are identified by their multiplicity (the overall spin of the electrons in that state), by their molecular orbital character (indicating the involvement of tt, n, cr, or other orbitals in the excitation process), and by their energy in relation to the energy of the ground state. The relevant excited states of a molecule include the singlet 5i and triplet Tj, and are typically 

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