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A negative resist, LMR (low molecular weight resist), for deep UV lithography
Author(s) -
Itoh Toshio,
Yamashita Yoshio,
Kawazu Ryuji,
Kawamura Kazutami,
Ohno Seigo,
Asano Takateru,
Kobayashi Kenji,
Nagamatsu Gentaro
Publication year - 1986
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760261606
Subject(s) - resist , materials science , photoresist , lithography , irradiation , fabrication , absorbance , dissolution , photolithography , photochemistry , optoelectronics , chemical engineering , composite material , optics , chemistry , medicine , physics , alternative medicine , layer (electronics) , pathology , nuclear physics , engineering
A negative deep UV resist, LMR, has been developed. LMR is a diazonaphthoquinonesulfonate of cresol novolac resin and possesses a high sensitivity of 15 mJ/cm 2 and a high resolution up to 0.2 μm by contact printing. An important feature of LMR is the production of negative images with overhung profiles. Such profiles are attributed to LMR possessing a large absorbance in the deep UV region (12 μm −1 at 250 nm), which is of great advantage to the lift‐off process in the fabrication of GaAs‐FET, surface acoustic wave (SAW) devices, and so on. Furthermore, because of the good thermal stability of LMR, it can liftoff hard metals such as Ni and Mo. In order to elucidate the phenomenon that deep UV irradiation retards the dissolution rate of LMR, a mechanistic study has been carried out. In both LMR and its analog lacking diazoquinone moiety, their molecular weights Increase upon deep UV irradiation, which suggests that crosslinking occurs in the base resin. This is supported by 13C NMR analyses of photochemical reaction products and by detection of radical species produced from the base resin. The photochemical reaction of the base resin is important to understand the overall lithographic performance of LMR.