AVS 47th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL+MS-ThM

Paper DI+EL+MS-ThM3
Nondestructive Investigation of the Si/SiO2 Interface by Spectroscopic Ellipsometry, Reflectance Difference Spectroscopy, Second Harmonic Generation, and X-ray Photoelectron Spectroscopy

Thursday, October 5, 2000, 9:00 am, Room 312

Session: Ultrathin Dielectrics and Interfaces
Presenter: J.F.T. Wang, North Carolina State University
Authors: J.F.T. Wang, North Carolina State University
J.W. Keister, North Carolina State University
Y.M. Lee, North Carolina State University
G. Lucovsky, North Carolina State University
J.E. Rowe, North Carolina State University
D.E. Aspnes, North Carolina State University
Correspondent: Click to Email
We report results of a systematic study with various nondestructive techniques of buried interfaces between Si and thin gate oxides thermally grown at 700C and rapid-thermal-annealed at temperatures to 900C. The objectives are to understand the optical properties, the step structure, and the nature of the chemical bonding of the interface and to determine the limits to which the various nondestructive probes, alone and in combination, can provide this information. We examine in particular data obtained as a function of heat treatment and surface orientation (miscuts 2, 4, 8, 10 degrees off (001) toward the nearest (111); (113); (111); and (110)), with emphasis on the vicinal (001) orientations. The RD spectra of all as-oxidized vicinal (001) samples decrease by nearly a factor of 5 for the 900C RTA, indicating step-density reduction and a net smoothing of the interface. Except for the 2 deg sample, which shows basically no signal, these spectra become essentially identical to the spectra of chemically etched, H-terminated vicinal (001) surfaces. All such spectra have the appearance of RD lineshapes obtained on (113) surfaces, which are nominally dominated by double-height steps. The ellipsometric data differ mainly in overlayer thickness, but interface information can be extracted through least-squares analysis assuming interface spectra of Si in amorphous and +1 and +2 charge states. To assist in this analysis we orthogonalize the fitting parameters to determine which combinations are best determined by the data. The results indicate that the best reference data are those obtained on H-terminated (111) surfaces. The interface XPS spectra become much more consistent after rapid thermal annealing, with the (001) and (111) spectra being dominated by Si in +2 and +1 charge states, respectively, as expected. This provides further evidence of a reduction in roughness with annealing.