On The Molecular Mechanism Of Positive Novolac Resists

Jian-Ping Huang; T. K. Kwei; Arnost Reiser

doi:10.1117/12.953020

30 January 1989 On The Molecular Mechanism Of Positive Novolac Resists

Jian-Ping Huang, T. K. Kwei, Arnost Reiser

Proceedings Volume 1086, Advances in Resist Technology and Processing VI; (1989) https://doi.org/10.1117/12.953020
Event: 1989 Santa Clara Symposium on Microlithography, 1989, San Jose, CA, United States

Abstract

A molecular mechanism for the dissolution of novolac is proposed, based on the idea of a critical degree of deprotonation as being the condition for the transfer of polymer into solution. The rate at which the critical deprotonation condition is achieved is controlled by the supply of developer into a thin penetration zone, and depends in particular on the rate of diffusion of the base cations which are the developer component with the lowest mobility. The penetration zone contains phenolate ions and ion-bound water, but it retains the structure of a rigid polymer membrane, as evidenced by the diffusion coefficient of cations in the pene;tration zone which is several orders of magnitude slower than in an open gel of the same material. When the critical degree of deprotonation is reached, the membrane structure unravels and all subsequent events, chain rearrangement and transfer into solution, occur rapidly. The supralinear dependence of dissolution rate on base concentration and the effect of the size of the base cation are plausibly interpreted by the model. The diffusion of developer components is assumed to occur preferentially via hydrophilic sites in the polymer matrix. These sites define a diffusion path which acts like a hydrophilic diffusion channel. Suitably designed hydrophobic molecules can block some of the channels and in this way alter the dissolution rate. They reduce in effect the diffusion crossect ion of the material. Hydrophilic additives, on the other hand, introduce additional channels into the system and promote dissolution. The concept of diffusion channels appears to provide a unified interpretation for a number of common observations.

Citation Download Citation

Jian-Ping Huang, T. K. Kwei, and Arnost Reiser "On The Molecular Mechanism Of Positive Novolac Resists", Proc. SPIE 1086, Advances in Resist Technology and Processing VI, (30 January 1989); https://doi.org/10.1117/12.953020

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