Many e-beam negative resists show postirradiation polymerization, i.e., even after e-beam irradiation termination, crosslinking reaction continues. This phenomenon shows an unfavorable effect in precise pattern fabrication; the first delineated portion of the resist undergoes a dimensional change with respect to the last-delineated portion. A method to inhibit postirradiation polymerization is presented based on a theoretical analysis of the postpolymerization mechanism. In the model used for analysis, active radicals are not extinguished in the vacuum and polymerization proceeds at a rate proportional to the radical concentration (first order reaction). A radical loses its activity due to collision with another radical (second-order reaction ). This model successfully explained experimental results. Postirradiation polymerization inhibition is achieved by adding a radical scavenger to resists. Active radical collision with a scavenger also extinguishes radical activity. Thus resist pattern width and thickness are freed from time dependence after irradiation. Resolution is also improved by postpolymerization inhibition as chain reactions in resists are suppressed. Although sensitivity is decreased, a highly sensitive negative resist can meet today’s requirement (around 1 μC/cm2), even after the addition of a scavenger. To demonstrate the benefit of postirradiation polymerization inhibition, a Cr mask was made with submicron features. It has 7-μm period Y-Y propagation patterns for a bubble memory, in which all gaps are designed as 0.5 μm. Adding a radical scavenger, 1,1-diphenyl-2-picrylhydrazyl (DPPH), and SEL-N resist, precise pattern fabrication was achieved, irrespective of the time after exposure.
A simple alternative was studied for the tri‐layer resist system. One single thick layer of resist polymer was surface silylated to obtain a bilevel structure that functioned similarly to the bilayer resist composed of the Si‐containing top imaging and the bottom planalizing layers. A resist or matrix polymer layer containing phenolic – OH groups was silylated by exposing it to hexamethyldisilazane vapor, and Si atoms were effectively incorporated in the surface sublayer by limited gas permeation and reaction with the – OH groups. Oxygen RIE durability of the silylated poly(vinyl phenol) or the positive‐working commercial EB resist, RE‐5000P, was > 10 times as high as that of PVP or RE‐5000P before silylation. The surface silylated single‐layer (SSS) resist derived from RE‐5000P was flood‐exposed through a mesh mask to 11.7°C/cm2 of 4 KeV electrons, developed with tetramethylammonium hydroxide in aqueous methanol, and plasma‐developed in an O2 RIE chamber to form a positive‐tone relief image.
One single thick layer of resist polymer was surface-silylated to get a bilevel structure which functioned similarly to the bilayer resist composed of the Si-containing top imaging and the bottom planarizing layers. A resist or matrix polymer layer containing phenolic --OH groups was silylated by exposing to hexamethyl disilazane vapor, and Si atoms were effectively incorporated in the surface sublayer by limited gas permeation and reaction with the --OH groups. 02 RIE durability of the silylated poly(vinyl phenol) (PVP) or a commercial positive-working EB resist, RE-5000P, was more than 10 times as high as that of PVP or RE-5000P before silylation. The surface silylated single-layer resist derived from RE-5000P of 1.3 ~m thick was flood-exposed through a mesh mask to 11.7 ~C/cm 2 of 4 keV electrons, developed with alkaline in aqueous methanol, and plasma-developed in an 02 RIE chamber to form a positive-tone relief image on a bare Si substrate. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 147.188.128.74 Downloaded on 2015-06-02 to IP
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