As semiconductor devices shrink, the minimum interconnect dimensions become comparable to the mean free path (mfp) of electrons in the interconnect metal. The resistivity of thin films rises above the bulk value around the mfp, due to the dominating effects of surface scattering of electrons. We explored the resistivity vs. thickness behavior for thin films of copper, the new interconnect metal. We have established that a resistivity of 2-2.2 mu Omega cm can be achieved for copper films as thin as 30-40 nm by sputter deposition and anneal (at similar to 300 degrees C) in argon containing 3 vol % H-2. We speculate that the presence of hydrogen leads to surface and grain boundary passivation, leading to reduced diffuse scattering of electrons. This in turn leads to a smaller increase in resistivity of thin films over the bulk resistivity value. The use of copper interconnects at dimensions less than 50 nm would be possible with such passivation schemes.