AVS 47th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS2-ThA

Paper PS2-ThA5
Etching Mechanism of Silicon Nitride Film in Self-aligned Contact Etching Process

Thursday, October 5, 2000, 3:20 pm, Room 311

Session: Dielectrics I
Presenter: M. Ito, Nagoya University, Japan
Authors: M. Ito, Nagoya University, Japan
S. Senda, Nagoya University, Japan
K. Kamiya, Nagoya University, Japan
M. Hori, Nagoya University, Japan
T. Goto, Nagoya University, Japan
Correspondent: Click to Email
For a contact hole etching process, the high etching selectivity of SiO@sub 2@ over Si@sub 3@N@sub 4@ as well as Si is required. In order to clarify the etching mechanism of Si@sub 3@N@sub 4@ film in H@sub 2@ diluted C@sub 4@F@sub 8@/Ar electron cyclotron resonance plasmas, we have investigated the mixing-layer in Si@sub 3@N@sub 4@ films using in-situ X-ray photoemission spectroscopy and in-situ Fourier transform-infrared reflection absorption spectroscopy. From etching results and C-N bonding compositions in the mixing layer as a function of H@sub 2@ dilution ratio, the intensities of C-N sp@super 2@ bonds are considered to have a relation with the etching rate of Si@sub 3@N@sub 4@. On the other hand, C-N sp@super 1@ bonds were not observed at all in the films. Moreover, to clarify the H@sub 2@ dilution effect, we have observed the surface reaction during H@sub 2@ plasma annealing after etching Si@sub 3@N@sub 4@ films under C@sub 4@F@sub 8@/Ar plasma condition. It was found that intensities of C-N sp@super 2@ bonds as well as sp@super 3@ bonds decreased while Si-N bonds increased with the annealing time. Therefore, C-N sp@super 2@ bonds as well as C-N sp@super 3@ bonds are suggested to be etched through the formation of byproduct such as HCN and to be broken to form Si-N bonds through the recombination of the dangling bonds such as -N and -Si. This fact suggests that the restriction of reaction of C-N sp@super 2@ bonds and C-N sp@super 3@ bonds with H or F atoms is a key factor for achieving higher selective etching of SiO@sub 2@ over Si@sub 3@N@sub 4@.