AVS 46th International Symposium
    Thin Films Division Monday Sessions
       Session TF-MoM

Paper TF-MoM8
Impact of Helium Dilution on Low-Temperature Silicon Depositions Using Electron Cyclotron Resonance and RF Plasma Sources

Monday, October 25, 1999, 10:40 am, Room 615

Session: Fundamentals of PECVD
Presenter: S.H. Bae, Pennsylvania State University
Authors: S.H. Bae, Pennsylvania State University
Y.C. Lee, Pennsylvania State University
R.T. McGrath, Pennsylvania State University
Correspondent: Click to Email
Low temperature silicon films have been prepared at 110° C using electron cyclotron resonance (ECR) plasma, ECR plasma plus RF substrate bias, and RF plasma only. As dilution media, both pure hydrogen and hydrogen mixed helium gases have been employed for these low-temperature depositions. In order to relate the plasmas to the properties of these low temperature Si films, in-situ optical emission spectrum (250 ~ 800 nm) for each plasma condition has been examined. Regardless of the presence of RF substrate bias during ECR plasma depositions, intensity of optical emission of ECR plasma much higher than that conventional RF plasma. In the ECR plasmas, the emission intensities of H radicals much stronger than those in RF plasma mode by two order of magnitude. In both H @sub 2@ and H@sub 2@ +He diluted RF plasmas, H @gamma@ (434 nm) and H @beta@ (486 nm) emissions are not noticeable for 0.6 second integration of optical spectrum while H @alpha@ (656 nm) line is observable in the RF plasma. Addition of He gas in ECR plasma results in strong He radical emission lines (389 nm and 502 nm); i.e., this indicates highly excited hydrogen plasma can be produced by the metastably excited He radicals. X-ray diffraction (XRD) analysis shows that low-temperature pure RF mode Si films do not have any crystallinity regardless of addition of He gas while the Si films prepared with ECR plasmas have high crystallinity. However, these high-crystallnity low-temperature ECR films are very porous and columnar. In terms of micro-etching effect due to hydrogen radicals in high-density plasmas, H @sub 2@+He dilution is more efficient than the case of H@sub 2@ dilution.