Filling of contacts and interconnects with Cu by XeCl laser reflow

The process window for XeCl laser (λ=308 nm) induced reflow of sputter-deposited Cu film to planarize and fill 1-μm-diameter contacts and 1-μm-wide interconnect trenches in a 1- or 2-μm-thick BPSG layer was investigated at room temperature, 365°C, and 440°C. Complete filling of 1-μm 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°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°C, and 440°C