Site-selective deposition of copper by controlling surface reactivity of SAMs with UV-irradiation

Using Cu(hfac)2 as the precursor, site-selective deposition of copper film was conducted on the 3-(mercaptopropyl) trimethoxy silane (MPTMS) and propyl trimethoxy silane (PTMS) self-assembled monolayers (SAMs) modified SiO2 substrates after UV-irradiated with a mask. Digital camera, charge coupled device (CCD) and scanning electron microscopy (SEM) analysis show that a negative pattern of copper was obtained on MPTMS-SAM modified substrates at 340 °C for 18 min of deposition and a positive pattern was obtained on PTMS-SAM modified substrates at 380 °C for 2 min. The surface structures of SAMs before and after UV-irradiation were characterized by water contact angle measurement and X-ray photoelectron spectroscopy. The results indicate that Si–C bonds broke and Si–OH bonds formed on irradiated MPTMS areas. Thus copper was site-selectively deposited on the covered areas where –SH groups remained and formed a negative pattern. However, formation of –COOH groups due to the oxidation of PTMS-SAM with activated oxygen species was the main reason for the formation of a positive pattern on PTMS. The strong interaction between Cu atoms and the terminated groups of SAMs (–SH or –COOH) was also the likely reason for the site-selective CVD of copper.