AVS 51st International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA6
NH@sub x@ Radical Densities and Plasma Chemistry in a Remote Ar-NH@sub 3@-SiH@sub 4@ Plasma for Silicon Nitride Deposition

Thursday, November 18, 2004, 3:40 pm, Room 213A

Session: Plasma-Surface Interaction
Presenter: P.J. van den Oever, Eindhoven University of Technology, The Netherlands
Authors: P.J. van den Oever, Eindhoven University of Technology, The Netherlands
J.H. van Helden, Eindhoven University of Technology, The Netherlands
R. Engeln, Eindhoven University of Technology, The Netherlands
D.C. Schram, Eindhoven University of Technology, The Netherlands
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
Although plasma deposited amorphous silicon nitride (a-SiN@sub x@:H) has widespread applications in industry, the exact growth mechanism of these films from NH@sub 3@-SiH@sub 4@ plasmas remains unclear. For example, the role of silane radicals, ammonia radicals, and possibly aminosilane radicals in the growth process is still not resolved. To obtain insight into the role of the various radicals in the plasma we have carried out absolute density measurements of NH and NH@sub 2@ radicals in a remote Ar-NH@sub 3@ and Ar-NH@sub 3@-SiH@sub 4@ plasma. The radicals have been detected by means of the cavity ringdown spectroscopy (CRDS) technique probing NH and NH@sub 2@ electronic transitions at ~597 and ~335 nm, respectively. The absolute densities obtained range from 10@super 10@ to 10@super 12@ cm@super -3@ depending on the NH@sub 3@ flow, downstream axial position, and the presence and flow of SiH@sub 4@. The kinetic gas temperature determined from Doppler broadening of the absorption lines is ~1500 K, in agreement with previous measurements. For the Ar-NH@sub 3@ plasma an increase of the NH and NH@sub 2@ density with the NH@sub 3@ flow has been observed. Analysis of the data on the basis of the reaction rates proposed in literature, suggests a considerable regeneration of NH@sub 3@ from its dissociation products. This possibly explains the high NH@sub 3@/SiH@sub 4@ ratio that is necessary to obtain a sufficiently high N/Si ratio in films deposited from Ar-NH@sub 3@-SiH@sub 4@ plasmas. The addition of SiH@sub 4@ decreases the NH@sub 2@ density in the Ar-NH@sub 3@-SiH@sub 4@ plasma and at low NH@sub 3@ flows even no NH@sub 2@ is observed. To understand these trends, which can originate both from plasma and surface processes, the NH density is currently investigated under the same plasma conditions. From a comparison of the results with those obtained from a simple plug-down model, insight into the key reactions in the Ar-NH@sub 3@-SiH@sub 4@ plasma is obtained.