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Epoxy resins for deep UV lithography
Author(s) -
Stewart K. J.,
Hatzakis M.,
Shaw J. M.
Publication year - 1989
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.760291405
Subject(s) - resist , epoxy , materials science , cationic polymerization , photoresist , onium , swelling , lithography , photopolymer , electron beam lithography , polymerization , polymer , photolithography , polymer chemistry , chemical engineering , composite material , nanotechnology , organic chemistry , optoelectronics , chemistry , ion , layer (electronics) , engineering
A negative resist based upon photo‐acid initiated cationic polymerization of an epoxy resin (1, 2) was reported in the early eighties with the advent of onium salts (3–5). An efficient acid generating onium salt, triphenylsulfonium hexafluoroantimonate (6), absorbs light in the deep UV producing acid upon direct photolysis in this region of the spectrum. The resin component of such a negative resist system must be optically transparent over the exposure wavelengths to obtain vertical image profiles. Another difficulty often encountered with crosslinking negative resists is swelling of the crosslinked matrix during development with organic solvents. This swelling manifests itself in distorted images and/or complete adhesion loss, especially when submicron features are involved. Our goal has been to address these problems and develop an organic developable deep UV resist capable of providing submicron images. Optically transparent commercial resins, styrene‐allyl alcohol copolymers, have been converted to glycidyl ethers, thereby providing cationically polymerizable functionalities. Careful choice of the resin was made to obtain reactive ion etch resistance, thermal stability, good adhesion, and coating properties. The synthetic procedure and characterization of the epoxy resin will be presented. The effect of the molecular weight distribution upon swelling during development and general solubility properties also will be discussed. Resist formulations exhibited sensitivities of 19 to 30 mJ/cm 2 on a Perkin Elmer 500 in the deep UV (UV2) mode. The electron beam sensitivity is 3 to 5 μC/cm 2 at 20 KeV. Submicron images have been generated in both optical and electron beam lithography.