Etch mechanisms of hybrid low-k material (SiOCH with porogen) in fluorocarbon based plasma

Abstract

This study is dedicated to the etching of a low-k material using the late porogen removal approach. In this approach, the porogen is removed by thermal annealing or UV curing after patterning or copper filling. Starting from a CF4 based plasma, the etch rate decreases with an Ar dilution or by adding a polymerizing gas such as CH2F2. On the other hand, the etch rate increases with O2 or N2 addition in the fluorocarbon gas mixture. X-ray photoelectron spectroscopy analyses show that the etching is controlled by the thickness of the fluorocarbon layer formed at the top surface of the hybrid material during the steady state etch regime. An etch stop phenomenon is even observed with highly polymerizing etch chemistries due to the formation of a thick fluorocarbon layer. Infrared spectroscopy analysis shows that the hybrid film is not damaged by the different etching chemistries investigated in contrast to the porous material.