Characterization of hydrogen etched 6H-SiC(0001) substrates and subsequently grown AIN films

Contributors:   J.D. Hartman, A.M. Roskowski, Z. J. Reitmeier, K.M. Tracy, R.F. Davis, and Robert J. Nemanich

ABSTRACT

Wafers of n-type, 6H–SiC(0001) with (N𝐷–N𝐴)=(5.1–7.5)×1017 and 2.5×1018 were etched in a flowing 25%H2/75%He mixture within the range of 1500–1640 °C at 1 atm. Equilibrium thermodynamic calculations indicated that the presence of atomic hydrogen is necessary to achieve etching of SiC. Atomic force microscopy, optical microscopy, and low energy electron diffraction of the etched surface revealed a faceted surface morphology with unit cell and half unit cell high steps and a 1×1 reconstruction. The latter sample also exhibited a much larger number of hexagonal pits on the surface. Annealing the etched samples under ultrahigh vacuum (UHV) at 1030 °C for 15 min resulted in (1) a reduction of the surface oxygen and adventitious hydrocarbons below the detection limit of Auger electron spectroscopy, (2) a (√3×√3)R30° reconstructed surface and (3) a Si-to-C peak-to-peak height ratio of 1.2. By contrast, using a chemical vapor cleaning (CVC) process consisting of an exposure to 3000 Langmuir (L) of silane at 1030 °C for 10 min under UHV conditions resulted in a (3×3) surface reconstruction, a Si-to-C ratio of 3.9, and islands of excess silicon. Continued annealing of the latter material for an additional 10 min at 1030 °C resulted in a (1×1) LEED pattern with a diffuse ring. Films of AlN grown via MOCVD at a sample platter temperature of 1274 °C for 15 min on hydrogen etched wafers having a doping concentration of 8.7×1017 cm−3 and cleaned via annealing had a rms roughness value of ≈0.4 nm.

Publisher: Journal of Vacuum Science and Technology A,   Volume: 21,   Published: 2003-02 ||   PDF (1.29 MB) ||   Read more...