Dependence of process parameters on stress generation in aluminum thin films

The dependence of residual stress on the process parameters for aluminum metallization has been studied using a rotating beam sensor. This shows increasing tensile stress with both the target power and ambient pressure used during the sputter deposition of the aluminum layer. The bulk resistivity of the deposited aluminum has been measured using a Van der Pauw technique on test structures fabricated alongside the sensors and this shows different trends with respect to the target power and ambient pressure. This indicates that the stress in an interconnect feature is dominated by extrinsic components, which result from the mismatch in thermal expansion coefficient between the constituent layers, rather than the defects formed during the sputter deposition of the metallization. This indicates the suitability of the stress sensor technique to the monitoring of interconnect features in a production line environment.