This paper describes the investigation on the feasibility of current coater/developer processes to the 157-nm lithography from the viewpoint of critical dimension (CD) control. The effect of coating, bake, and development process on the CD of a 157-nm resist, where fluorine is introduced in the side chain, is studied. A KrF and ArF resist is also used for comparison. Firstly, as for the coating process, the coverage performance and the film thickness uniformity of the 157-nm resist shows that the current coating methods are feasible to 157-nm resist, even though the 157-nm resist is highly hydrophobic. Secondly, as for the bake process, the post exposure bake (PEB) temperature dependence of CD for the 157-nm resist is found to be lower than that for 248 and 193-nm resist. This means that our current PEB temperature control system, which is suitable for 248 or 193-nm resist, is also effective for the 157-nm resist. Thirdly, as for the development process, it is found that a static puddle formation process shows a smaller line edge roughness (LER) than a dynamic puddle formation process. Therefore, the static puddle formation process, with the use of linear drive (LD) developer nozzle for instance, is attractive for the 157-nm resist process. Lastly, from the viewpoint of contamination control, it is found that the amine level should be controlled to be less than 0.1ppb in order to prevent the CD change during post exposure delay (PED) for the 157-nm resist.
Reducing defects in the semiconductor photolithography process has become increasingly critical. Many kinds of defects can occur during photolithography, such as missing contact holes or pattern collapses that occur during developing. As the pattern size becomes finer, the exposure wavelength has been shortened from 248-nm to 193-nm, and then to 157-nm. In addition, the resin structure and the chemical characteristics of the resist material have changed greatly. Changing the resist material from I-line to 248-nm created the problem of satellite defects peculiar to chemically amplified resist. Previous studies have suggested that a satellite defect is a complex salt of PAG, quencher, and TMAH, and is soluble in water.1) Because the resist material for 157-nm lithography is highly hydrophobic and is used for making ultra-thin films, defect evaluations of it are necessary. This paper evaluates the defects arising with various kinds of 157-nm lithography resist. Just as with 248-nm resist, a deposition defect peculiar to CAR occurs with 157-nm resist, but it occurs more frequently than with 248-nm resist. Unique defects appear with 157-nm resist, but their appearance and frequency seem to depend on the resist structure. The number of missing contact holes increases when the contact angle to ultra-pure water on the 157-nm resist film raise. It is necessary to elucidate on the mechanism that the unique defect occur in 157-nm resist.
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