Person:

Lin, Youbo

Barriers to prevent diffusion of copper, oxygen and water vapor were formed by CVD using a manganese precursor vapor that reacts with silica surfaces. The manganese metal penetrates only a few nanometers into the silica to make conformal amorphous manganese silicate layers. This MnSixOy was found to be an excellent barrier to the diffusion of Cu, O2 and H2O vapor. The adhesion strength of Cu to the MnSixOy was found to be sufficiently strong to satisfy the semiconductor industry requirements for interconnections in future microelectronic devices. CVD Mn dissolves into copper surfaces and then diffuses to increase adhesion to SiCNO capping layers.

Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. The porosity and pore structure of these low-k dielectric materials, however, also affect other important material properties in addition to the dielectric constant. In this paper, we investigate the impact of porogen loading on the stiffness and cohesive fracture energy of a series of porous organosilicate glass (OSG) thin films using nanoindentation and the doublecantilever beam (DCB) technique. The OSG films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and had a porosity in the range of 7~45%. We show that the degree of porogen loading during the deposition process changes both the network structure and the porosity of the dielectric, and we resolve the contributions of both effects to the stiffness and fracture energy of the films. The experimental results for stiffness are compared with micromechanical models and finite element calculations. It is demonstrated that the stiffness of the OSG films depends sensitively on their porosity and that considerable improvements in stiffness may be obtained through further optimization of the pore microstructure. The cohesive fracture energy of the films decreases linearly with increasing porosity, consistent with a simple planar through-pore fracture mechanism.