Sumulation of porous low-k dielectric sealing by combined He and NH3 plasma treatment

Summary form only given. In order to reduce the RC time delay in integrated circuits, porous dielectric materials are used to lower the capacitance. Typical pore sizes are many nm with porosity of up to 50%. The porous low-k materials are typically SiOCH - silicon dioxide with carbon groups, principally CH₃, lining the pores. These materials have pores open to the surface which are internally connected and so can offer pathways for reactive species to enter into the porous network. Reaction with the CH_X groups can increase the k value of the material. To maintain the low k value of the porous dielectric, sealing of the surface pores is essential. Treatment of the porous material with successive He and NH₃ plasmas has been successful in sealing the pores. Ultimately, this sealing process is a tradeoff between densification of the porous material and removing CH_X groups, increasing the k-value and sealing the pores. A reaction mechanism has been developed for the sealing of a porous carbon doped silica films (SiOCH) in sequentially applied He and NH₃/Ar plasmas. The HPEM (Hybrid Plasma Equipment Module) was employed to obtain the ion energy and angle distributions of reactive fluxes from inductively coupled plasmas. These are used as input to the MCFPM (Monte Carlo Feature Profile Module) with which profiles of the low-k materials after the plasma exposures are predicted. Results will be discussed, including validation with data from the literature, for the densification and sealing of pores as a function of bias voltage and plasma power.