Embedding of copper into submicrometer trenches in a silicon substrate using the molecular precursor solutions with copper nano-powder

Metallic copper was completely embedded in the trenches (0.2-1.0 µm wide and 5.0 µm deep) by heat-treating a mixed precursor at 350 °C for 30 min under an Ar flow of 1.5 L min-1 in a tubular furnace. An ethanol solution containing a dibutylammonium salt of a Cu(II) complex of EDTA ligand, a Cu(II) complex of propylamine, and the Cu nano-powder (20-40 nm) was used to fill the trenches before the heat treatment. Si substrates with the trenches were immersed in this precursor solution under ultrasonic irradiation, and then slowly withdrawn from the solution. The dip coating and heat treatment steps were repeated. The cross-section FE-SEM images of the treated substrate indicate that the embedded copper after two heat treatments of the precursor solution filled the trenches without voids. The XRD pattern of the resulting film on the Si substrate without trenches deposited under identical conditions suggests that the embedded components mainly consisted of copper with Cu2O as a minor product. Using the four probe method, the electrical resistivity of this resulting film (300 nm thick) was found to be 3.8(5)×10−5 Ω cm.