Feasibility of BCB as an interlevel dielectric in integrated circuits

Abstract

This paper investigates the feasibility of using an organic polymer based on benzocyclobutene as an interlevel dielectric material in very large scale integrated (VLSI) circuits. The material is a thermoset resin with attractive electrical and mechanical properties for application as an interlevel dielectric in VLSI circuits. It has a low relative dielectric constant of 2.7. The single coating planarization achieved by spin coating the material is superior to currently used materials and makes it a very attractive material for the fabrication of multilevel metal systems. The planarization properties of this material are presented and compared with those of polyimide. The patterning and dry etching of BCB to define 1 µm vias is described. As the material has limited thermal stability at temperatures greater than 350°C, compatible materials for low via resistivity have been investigated using a double level metal structure. The effect of post metal anneals on via resistivity of various via structures is presented. It is found that a low via resistivity of 3 × 10-9 gW-cm2 without any post metal anneal is obtained by using an AlCu/Pd-AlCu metallurgy.