The stringent requirements facing modern chemically amplified photoresists and antireflective coatings make computer physical simulation methods a valuable tool for photoresist and ARC research and design. Hypothetical microlithographic processes involving toolsets that are unavailable to the experimenter may be evaluated. Complex photoresist physical reaction phenomena, often difficult to measure experimentally, may be evaluated within the limits of the mathematical models used. This work details the mechanics and application of a custom simulation tool written for the modeled study of reactive soluble ARCs (DBARCs), soluble ARCs, and photoresist-ARC interactionsphenomena not readily modeled by commercially available software at the time of this paper. Photoresist and ARC interactions are modeled by computing two-dimensional composite diffusion and reaction. Soluble ARCs, either reactive (DBARCs) or nonreactive, are modeled using composite diffusion, a full level-set front tracking development method and multiple development rate functions. Physical models, mathematical formulations and numerical methods of solution are shown. Scenarios hypothesizing the origin of photoresist profile foot formation are discussed and modeled. Models of reactive, soluble ARCs (DBARCs) are compared to models of constant development rate soluble ARCs. The effects of specific reactant diffusion and reaction upon DBARC dissolution rate contours are modeled.
A first generation DBARC applicable for 1 st minimum193nm lithography is described in this paper. The polymer used in this DBARC is insoluble in the casting solvent of the resist, which is propyleneglycolmonomethyletheracetate (PGMEA). Photo acid generator (PAG) and base extractions from the DBARC coating by the resist casting solvent were examined by the DBARC dissolution rates in the developer, before and after solvent treatments. Although the resist and the DBARC do not appear to intermix, strong interaction between the two is evident by their lithographic performance and dissolution rate study.
The dependence of the dissolution rates of phenolic resins on the base concentration of the developer can be described by a dimensionless equation based on a membrane model of novolak dissolution [J. P. Huang, T. K. Kwei, and A. Reiser, Macromolecules 22, 4106 (1989) and R. A. Arcus, Proc. SPIE 631, 124, (1986)]. The resin is characterized by a dissolution threshold c0, which is a limiting base concentration below which dissolution no longer occurs, by a scaling exponent n and by a membrane permeability Pr which refers to a developer of base concentration c = 2c0. Under these reference conditions all resins are in a corresponding state and dissolve with the same dimensionless rate of R/Pr = 0.5. The inhibition effect in an inhibitor/resin pair is represented by a plot of log(Ri/R0) against the inhibitor concentration in the resin matrix, where Ri is the rate of dissolution of the inhibited, R0 the rate of dissolution of the pure resin. The slope of this plot is independent of the inhibitor concentration over a reasonable concentration range and may be termed the inhibition factor and used as a measure of the inherent inhibition capability of the inhibitor in the resin. It is termed the inhibition factor. It is suggested that inhibition factors be compared in conditions where the pure resins dissolve at the same rate. In this study we have chosen a rate of 15 μm/min as the standard condition.
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