1. Field of Invention
The invention relates to a method for patterning a thin film on a substrate, and more particularly to a method for reducing roughness of the pattern.
2. Description of Related Art
In material processing methodologies, pattern etching comprises the application of a layer of radiation-sensitive material, such as photo-resist, to an upper surface of a substrate, the formation of a pattern in the layer of radiation-sensitive material using photo-lithography, and the transfer of the pattern formed in the layer of radiation-sensitive material to an underlying thin film on the substrate using an etching process. The patterning of the radiation-sensitive material generally involves exposure of the radiation-sensitive material to a pattern of electromagnetic (EM) radiation using, for example, a photo-lithography system, followed by the removal of the irradiated regions of the radiation-sensitive material (as in the case of positive tone resist), or non-irradiated regions (as in the case of negative tone resist) using a developing solution.
As the critical dimension (CD) decreases and the aspect ratio of the patterns formed in a layer of radiation-sensitive material increases, the potential for pattern defects including, but not limited to, pattern collapse, line edge roughness (LER), and line width roughness (LWR), becomes increasingly enhanced. In most situations, excessive pattern defects are unacceptable and, in some instances, catastrophic.