Organic Bottom Anti-reflective Coatings Research Articles

Trilayer Development for 193nm Immersion Lithography

Immersion technology is enabling the extension of 193 nm lithography by increasing the numerical aperture (NA) of the exposure system. The result is smaller depth of focus, subsequently requiring the use of thinner photoresists. Consequently, bottom antireflective coatings (BARCs) are required to have increased etch selectivity to thinner photoresists, as well as improved reflectivity control to minimize reflectivity from higher incident angles of hyper NA lens systems. A spin on trilayer patterning scheme has recently become a favorable approach to simultaneously address these issues.IBM and Shin Etsu have jointly developed a silicon containing BARC for the purpose of trilayer imaging. In this work, hyper NA imaging performance of the trilayer film stack is reported, at NA > 1.0. Full field, polarized 1.2 NA dipole imaging of line/space lithographic patterns is compared with both the trilayer imaging stack as well as a single layer, organic BARC stack. The process window of 1-D line/space structures was found to be significantly improved on the trilayer imaging stack. Improved profiles were observed on the trilayer film stack, with other lithography metrics showing comparable performance on both film stacks. Characterization of a solvent based rework scheme is presented for the trilayer imaging stack. Also, the chemical interaction between the silicon BARC and the photoresist was studied with an acid diffusion experiment. Within the detection limits of the experiment, it was found that acid diffusion from the silicon BARC is not a likely contributor to imaging performance.

Recent Progress in Organic Bottom Anti-reflective Coatings.

Recent Progress in Organic Bottom Anti-reflective Coatings.

Concept of two-dimensional swing curves for critical dimension prediction and optimization of resist/antireflective coating bilayers in topographic situations

In microlithography, the necessity of using bottom antireflective coatings (BARCs) to reduce linewidth variations resulting from reflective notching and thin film interference effects has been largely demonstrated. We report a new methodology, based on a 2-D swing curve concept, to predict the lithographic performance of resist/BARC bilayers in a topographic situation to optimize the critical dimension (CD) range. Due to inherent planarization effects when coating on topography, both the resist and organic BARC thicknesses vary, as do the final reflectivity and CDs. As a consequence, it is not easy to determine the optimal BARC thicknesses and to predict the lithographic performance, taking into account topography effects over the whole chip. Usually, lithographic performance (CD swing curves) is measured or calculated using modeling over plane wafers. Over the topography of a real chip, however, the resist thickness can cover up to four periods of the swing curve, which means that lithographic performance over a real chip cannot be predicted using swing curves calculated or measured on plane wafers. We therefore propose a new method of representing the reflectivity and CD swing curves in two dimensions to evaluate the lithographic performance of the BARC/resist bilayer. A simulation algorithm is performed that enables the determination of both the optimal BARC thicknesses and the lithographic performance window over the whole chip. Practical examples are given demonstrating the role of such a simulation.