Resolution (R), line-width roughness (L), and sensitivity (S) are three key indices describing the performance of a resist. When optimizing a resist to compromise the RLS trade-off in extreme-ultraviolet lithography, outgassing of the resist also needs to be considered, because it will cause deposition of cleanable and non-cleanable contaminants on the surface of the projection optics and reduce the throughput of the exposure tool. In this paper, the dependence of outgassing of a resist on its compositions, such as types of photo-acid generator, quencher, and acid liable group as well as their loadings are investigated systematically through a set of specially prepared resist samples. The outgassing of these samples is tested on EUVOM-9000 from Litho Tech Japan. The lithographic performances of these samples are also characterized on the ASML NXE3100. Directions for optimizing resist lithographic performance under the constraint of resist outgassing are proposed.
For semiconductor manufacturing of k<sub>1</sub><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-k<sub>1</sub>
application, the optimizing conditions for DOF, MEEF, LWR, 2D features, top-view profile, and
defect become more challenging than ever for manufacturing. The low-k<sub>1</sub> 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.
In a conventional lithography process, the resist pattern is removed by dry strip or wet
chemical etch. The wet chemical etch includes sulfuric peroxide etch and solvent etch. The
wet chemical etch process is always combined with the dry strip process to meet the residue
process spec. However, in some applications, only the wet-etch process can be used to
avoid substrate damage during the plasma step. However, organic residue can be found
from particle surface scan and TGA/DSC after normal solvent strip.
In this paper, we investigate polymer residue stripping using only solvent as well as solvent
in combination with UV treatment. For solvents only, some solvents different from the
conventional PGMEA/PGME mixture in polarity, also exhibited stripping ability but the
efficiency is not as good as PGME/PGMEA mixture. When supplemented with UV
treatment, the organic residue can be further decomposed and removed completely. The UV
we used contains 185nm and 254nm wavelengths. Ozone is generated during UV
exposure and acts as oxidant. The organic residue is thus decomposed and removed. It has been proven as an effective method to cleave the C-C bond without damaging the wafer substrate. The organic residue on the wafer surface can be easily stripped away under UV-ozone exposure. Its defect performance is also discussed in this paper.