Patterning Of Copper Thin Films On Silicon Substrates

Copper has lower resistivity and higher resistance to electromigration and stress migration compared with aluminum alloys. To fabricate the high performance interconnects with low RC delay, the integration of low resistivity metal wiring and lowκinter-metal dielectric is crucial for next generation ultra large-scale integrated circuit technology. To implement copper into a metal line via interconnects, the dual damascene process is required because copper is difficult to etch. In considering methods to deposit copper, Metal-Organic Chemical Vapor Deposition (MOCVD) processes have several advantages such as the ability to achieve good conformality and the possibility of selective deposition.This research was based on a MOCVD system, which was designed, built previously. Cu(II)(hfac)2 was used as precursor, and hydrogen as carrier gas and reactant. Chemical vapor 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. It is mainly composed of the following two parts:Part 1: Selective chemical vapor deposition of copper films on MPTMS-SAMs modified SiO₂ substrates was studied. It shows: compared with the exposed areas, copper preferred to be deposited in the covered areas and formed a negative pattern. The Si-C bonds were broken during UV-irradiation in the exposed areas. Therefore, the -SH groups were stripped from the substrates and Si-OH bonds formed. However, in the covered areas, the -SH groups remained. The better hydrogen donating ability of -SH groups and the strong interaction between Cu and S atoms made copper be deposited selectively on the covered surfaces. The selectivity was found in certain temperatures and time. Moreover, negative pattern of copper thin films was also obtained when using UV-light which emits primarily at 300-400 run for irradiation.Part 2: Selective chemical vapor deposition of copper films on PTMS-SAMs modified SiO₂ substrates was studied. It shows: copper preferred to be deposited in the exposed areas and formed a positive pattern. This is due to the oxidation of PTMS-SAM with the activated oxygen species in irradiated areas, resulting in the decomposition of PTMS and formation of -COOH groups in the surface. Thus the better proton donating ability of -COOH groups and the strong interaction between Cu and -COOH made copper be deposited selectively on the exposed surfaces. The selectivity was also found in certain temperatures and time.