AVS 49th International Symposium
    Plasma Science Thursday Sessions
       Session PS-ThA

Paper PS-ThA5
Etching of Porous Low-K Dielectric Films in Fluorocarbon Plasmas

Thursday, November 7, 2002, 3:20 pm, Room C-103

Session: Dielectric Etch II
Presenter: S.A. Rasgon, Massaschusetts Institute of Technology
Authors: S.A. Rasgon, Massaschusetts Institute of Technology
B.E. Goodlin, Massaschusetts Institute of Technology
H.H. Sawin, Massaschusetts Institute of Technology
Correspondent: Click to Email
To further reduce interconnect delay and enable higher device speeds (especially as the critical dimensions are lowered below 0.13 µm), it becomes advantageous to reduce the dielectric constant of the interlevel dielectric material between the metal lines. Porous low-k materials are potential candidates to meet this objective. While current research has focused on the material characterization of porous low-k films, little attention has been paid to the etching characteristics, of critical importance for process integration. Our research focuses on the etching characteristics and kinetics of leading candidate porous low-k dielectric films in fluorocarbon chemistries. Etching characteristics of these films are simultaneously compared with OSG, SiO@sub 2@, SiC(N), and photoresist films to reveal similarities and differences in etching behavior, and selectivity toward mask and stop layers. Ellipsometric results on porous low-k films indicate a possible competition between diffusion of etching precursors into the porous matrix, and ion-enhanced etching. Specifically, at low DC bias voltages, we note what appears to be a mixed fluorocarbon/porous-low k layer, possibly several hundred Å deep. As DC bias is increased, the mixed layer thins, and disappears around 300 V DC bias. This mixed layer is not present on OSG or SiO@sub 2@ samples etched at the same conditions. XPS studies will confirm these results. Understanding these etching behaviors may provide valuable insight into solving the problems of damage to the dielectric constant of porous low-k films, and reverse - selectivity during etching of the stop layer.