Fluorocarbon plasma etching and profile evolution of porous low-dielectric-constant silica

Sankaran, Arvind; Kushner, Mark J.
March 2003
Applied Physics Letters;3/24/2003, Vol. 82 Issue 12, p1824
Academic Journal
To achieve shorter RC-delay times in integrated circuits low-dielectric-constant (low-k) materials are being investigated for interconnect wiring. Porous silicon dioxide (PS) is one such material. To address scaling issues during fluorocarbon plasma etching of PS, a feature profile model has been integrated with a plasma equipment model. To focus on issues related to the morphology of porous materials, the PS was treated as stoichiometric SiO[sub 2]. The model was validated by comparison to experiments for PS etching in CHF[sub 3] plasmas sustained in an inductively coupled reactor. We found that etch rates (ER) for PS are generally higher than for SiO[sub 2] due to the inherent smaller mass density, although ER do not necessarily scale linearly with pore size or porosity. Mass-corrected ER can be either larger or smaller than that of solid SiO[sub 2]. For example, in polymerizing environments, at high porosities and large pore radii, there is a reduction in ER due to pore filling with polymer. Profile scaling parameters, such as for tapering, observed for solid SiO[sub 2], are generally applicable to PS.


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