Modification of low κ materials for ULSI multilevel interconnects by ion implantation

Thin films of low dielectric constant (κ) materials such as Xerogel (κ=1.76) and SiLK^TM(κ=2.65) were implanted with argon, neon, nitrogen, carbon and helium with 2 × 10¹⁵ cm^-2 and 1 × 10¹⁶ cm^-2 dose at energies varying from 50 to 150 keV at room temperature. In this work we discuss the improvement of hardness as well as elasticity of low κ dielectric materials by ion implantation. Ultrasonic Force Microscopy (UFM) [6] and Nano indentation technique [5] have been used for qualitative and quantitative measurements respectively. The hardness increased with increasing ion energy and dose of implantation. For a given energy and dose, the hardness improvement varied with ion species. Dramatic improvement of hardness is seen for multi-dose implantation. Among all the implanted ion species (Helium, Carbon, Nitrogen, Neon and Argon), Argon implantation resulted in 5× hardness increase in Xerogel films, sacrificing only a slight increase (∼ 15%) in dielectric constant.