Development of a three-layer metal backend process for application to a submicron CMOS logic process

A three-layer metal process for application to a submicron logic process has been developed. The development was carried out in two phases. In phase 1, the metal-one and metal-two thicknesses were identical, and silicate sandwich planarization was used for both. This allowed the three-layer metal process to be run using existing technology in order to target device parameters and build up a reference for the phase 2 development. In phase 2, the metal-two thickness was adjusted to meet the resistivity used. The planarization allows for good critical dimension control of 1850-nm-thick metal three. Via string yields and resistivities have been shown to be sensitive to the siloxane type and processing conditions. With process modifications such as close-coupled bakes before metal deposition, the results with the siloxane have been comparable to those achieved with the reference silicate