(Invited) Bottom-up Gold Filling for Manufacture of X-Ray Gratings: Mechanism and Implications

Abstract

Over the past four years a process for extreme superconformal deposition of gold has been demonstrated and explored for void-free filling of recessed features on patterned substrates for application in X-ray imaging. Uniform and complete void-free filling was detailed on 100 mm silicon wafers patterned with micrometer pitch vias of aspect ratio (height/diameter) 23 and trenches of aspect ratio (height/width) exceeding 60 as well as trenches more than 300 μm deep and fractal patterns of spatially varying depth. This talk discusses a proposed mechanism and model for the observed behavior. Simulations capture key features of the experimental processes, including not only the bottom-up filling itself but also an extended incubation period of conformal deposition that precedes its start as well as self-passivation of the active deposition that accompanies the completion of filling. Feature filling results with relevant electrochemistry are discussed in the context of predicted behavior for different deposition conditions. Cross-sectioned 60 μm deep trenches Au filled at fixed potentials, the associated current transients, a Au filled grating and a simulation of filling in 50 μm deep trenches are all shown in the figure. Figure 1