Effect of Scanning Speed on Copper Line Deposition Using Nanoparticle Deposition System (NPDS) for Direct Printing Technology

Abstract

Cu nanoparticles (100 nm) were deposited on a silicon substrate using Nanoparticle Deposition System (NPDS) at 300 mu m of stand-off distance (SoD). It was found that the lines deposited at a scanning speed below 5 mu m/s showed ohmic contact; their resistivities were 1.68 x 10(-4) Omega.cm at 5 mu m/s, 3.91 x 10(-5) Omega.cm at 2 mu m/s, 1.70 x 10(-5) Omega.cm at 1 mu m/s, and 1.28 x 10(-5) Omega.cm at 0.5 mu m/s, respectively. However, samples fabricated at scanning speed of 8 and 10 mu m/s showed schottky contact behavior. To study relationship between resistances of the deposited copper lines at various scanning speeds and density of the line, porosity of the deposited copper lines and SEM images of Cu lines were studied. As a result, average porosity of the copper lines was found to be 16% at 5 mu m/s, 8% at 2 mu m/s, 2% at 1 mu m/s, and 6% at 0.5 mu m/s. The porosity values are closely related to the resistance of the deposited copper lines. Therefore, the deposited copper line at 1 mu m/s of scanning speed was shown to be the best one with the lowest porosity and resistance with its maximum thickness. This indicates that both the resistance and density of the deposited line improved at low scanning speed.