A Study of Water Absorption Induced-Dielectric Constant Increase and Its Suppression on Copper Damascene Interconnect Structure with Porous Low-k (k=2.3) Dielectrics

A key technology for realizing an effective k-value (keff) required for 45nm node is proposed. We studied the behavior of effective dielectric constant derived from capacitance of double-level copper interconnect wires with porous low-k material in detail. The porous low-k materials easily absorb moisture due to process damage and the dielectric constant drastically increases. We have confirmed that if moisture-controlled robust process integration is performed, a reasonably effective dielectric constant (2.8) is obtained corresponding to the ideal bulk k-value (2.4). However, when the sealing of passivation films is broken, the effective dielectric constant increases to the level derived from that of the damaged blanket film. In order to ensure a target capacitance of copper interconnect wire with porous low-k material, it is indispensable to perfectly seal a whole device area from moisture uptake