Filling of contacts and interconnects with Cu by XeCl laser reflow

The process window for XeCl laser ( lambda =308 nm) induced reflow of sputter-deposited Cu film to planarize and fill 1- mu m-diameter contacts and 1- mu m-wide interconnect trenches in a 1- or 2- mu m-thick BPSG layer was investigated at room temperature, 365 degrees C, and 440 degrees C. Complete filling of 1- mu m contacts and trenches with an aspect ratio of 1 is possible with an appreciable process window, but filling of these same contacts and trenches with an aspect ratio of 2 is only possible at a substrate temperature of 440 degrees C. The properties of the Cu films, such as sheet resistance, reflectance, grain size, and stress, were also characterized as a function of laser fluence at room temperature, 365 degrees C, and 440 degrees C.<
>