For semiconductor manufacturing of k1<0.3 half pitch, immersion lithography is still
indispensable for process development and production. As the minimum feature size reaches the
resolution limit, many resolution enhancement techniques and processes are developed to meet
the stringent imaging requirements. Since the optical contrast is not sufficient for low-k1
application, the optimizing conditions for DOF, MEEF, LWR, 2D features, top-view profile, and
defect become more challenging than ever for manufacturing. The low-k1 induced poor ADI
(after development inspection) end-to-end profile is deleterious to pattern fidelity that may
further impact the AEI (after etching inspection).
From a previous study, the photo-decomposed base (PDB) has been proven effective in
enhancing the resist contrast and improving the DOF from conventional quenchers. In this paper,
we study its further improvement on litho performance by controlling the diffusion lengths of the
PAG and the PDB. We split the polarity and size of the PAG and PDB to control the diffusion
length. The top view profile is improved from rounding to vertical if a longer diffusion length of
the PDB is selected. The scattering bar printing window can also be improved in such a
condition. If the PAG and the PDB have better matching controls, the MEEF, LWR, CDU, and
end-to-end top view profile are improved as shown in Fig.1.