Abstract
Abstract This research investigated the relationship between the plasma state and the properties of Cu thin films deposited on 6000 Å SiO2/ n-type Si and 400 Å TaN/ 5000 Å SiO2/ n-type Si by ionized metal plasma system (IMP). The Langmuir probe is used to determine the plasma density, plasma potential, electron temperature for characterizing the plasma state. Field emission gun scanning electron microscopy (FEG-SEM) was used to observe the cross-sectional microstructure and determine the film thickness. The roughness and surface morphology of copper thin film was measured from the image of atomic force microscopy (AFM). The crystal structure of copper thin film was identified by X-ray diffraction (XRD). The texture and grain size were determined from the XRD results. Glancing incident X-ray diffraction (GIXRD) was used to determine the lattice parameter of copper thin films. The packing factor of the Cu films was determined by RBS. The composition depth profiles were measured by secondary ion mass spectroscopy (SIMS) and the inter-diffusion distance between Cu and Si was also estimated. The resistivity was measured by a four-point probe. The total delivered energy density was estimated to explain grain size, inter-diffusion distance, and the performance of TaN diffusion barrier. It is found that the sputtered energy of the neutrals or ions dominates the total delivered energy from the estimation. The preferred orientation changed from Cu (111) to Cu (200) with the increase of the total delivered energy density and the thickness of Cu thin films for both substrates. As the total delivered energy density increases, grain size and inter-diffusion distance between Si and Cu of Cu thin films deposited on 6000 Å SiO2/ n-type Si increases. The increase of the total energy density facilitated copper atoms to penetrate TaN diffusion barrier into Si base at Ar pressure lower than 7 mTorr even though the substrate temperature is only 25 ℃.