Optical lithography

Determination of the Dill parameters of thick positive resist for use in modeling applications

“…For thicknesses in the range of 1 μm, a variety of resist types were studied in the past to determine relevant input parameters for simulation tools. However, simulation tools for thin film lithography have to be further developed to be able to consider the nonlinear properties of thick photoresists by improving the simulation models such as the Dill exposure model [2,3] and the Mack development model [4,5]. For model improvement, accurate measurement of the simulation parameters for thick photoresist is an important issue.…”

Using advanced simulation to aid microlithography development

“…An exciting period of early investigations led to a series of seminal papers [9]- [13] that were published by F. Dill's research group at IBM. These papers covered much of the basic physics and chemistry issues that enable a reasonable description of the key microlithographic processes, both from the standpoint of modeling and simulating the key phenomena, as well as measuring and characterizing the more critical physical parameters.…”

“…The chemical change in the photoresist material alters the optical properties of the material as well, most notably by changing its absorption property. The model for the absorption coefficient that was proposed in 1975 [9], [10], [12] was the following simple phenomenological linear model: (1) where is the fraction of photosensitive material, per unit volume, present at position and time . The parameter equals the absorption coefficient when all photosensitive material has been chemically altered, while is the coefficient that dictates the linear dependence of on .…”

“…However, a second important component is also necessary in order to model the exposure, namely, the time rate of change of as the photoresist material is exposed. The model used in 1975 was [9], [10], [12] (2) so that the time-rate of change of is assumed to be linearly proportional to both the electromagnetic energy density at position and time in the photoresist, as well as the amount of PAC present.…”

“…As described in [9], [10], and [12], by independently measuring the rate of dissolution as a function of , where an entire bulk film was prepared and exposed to have the same PAC concentration throughout, then a local rate could be inferred and treated as the actual dissolution rate at each point on the surface of a film with varying PAC concentration. The work in [12] describes the mathematical treatment of the surface evolution as determined by dividing the film into small cells, and removing cells at a rate proportional to .…”