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Surface Smoothing of Polycrystalline Si Waveguides With Gas-Cluster Ion Beams

Published online by Cambridge University Press:  10 February 2011

N. Toyoda ,
K. K. Lee ,
H-C. Luan ,
D. R. Lim ,
A. M. Agarwal ,
K. Wada ,
L. C. Kimerling ,
L. P. Allen ,
D. B. Fenner  and
A. R. Kirkpatrick
N. Toyoda
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected] Epion Corporation, 37 Manning Road, Billerica, MA 01821
K. K. Lee
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected]
H-C. Luan
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected]
D. R. Lim
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected]
A. M. Agarwal
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected]
K. Wada
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected]
L. C. Kimerling
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, [email protected]
L. P. Allen
Affiliation:
Epion Corporation, 37 Manning Road, Billerica, MA 01821
D. B. Fenner
Affiliation:
Epion Corporation, 37 Manning Road, Billerica, MA 01821
A. R. Kirkpatrick
Affiliation:
Epion Corporation, 37 Manning Road, Billerica, MA 01821
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Abstract

Polycrystalline Si (poly-Si) waveguides offer design flexibility and multilayered structures in Si-integrated photonic devices. However, as-deposited poly-Si surfaces are rough compared with single-crystalline Si, and a rough surface causes significant waveguide scattering loss at the surface. In this study, surface smoothing of poly-Si waveguides with a gas-cluster ion beam (GCIB) was demonstrated as a new smoothing technique. As the GCIB process is a directional ion-beam process, in principle it can be applied not only to plane surfaces but also to three-dimensional or non-flat structures, such as waveguide ridges.

The initial average roughness of as-deposited poly-Si films (625°C, 1 μm thick) ranged from 15 nm to 22 nm, and the grain sizes were distributed from 0.2 to 0.4μm. This rough surface was dramatically smoothed to a roughness of 1.5 nm by Ar cluster ion irradiation. From the relation between the sputtered depth and the surface roughness, the sputtered depth must be greater than the height difference of the roughness (peak-to-valley) to obtain smooth surfaces. Optical transmission losses at λ =1.54 μm were measured using cutback measurement from samples before and after the smoothing by GCIB. After surface smoothing with GCIB, the optical loss decreased from 85 dB/cm to 54 dB/cm.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 597: Symposium PP – Thin Films for Optical Waveguide Devices & Materials … , 1999 , 51
Copyright
Copyright © Materials Research Society 2000

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