μ-Raman investigations of plasma hydrogenated silicon

Standard [ 001]- oriented p- ( 12 - 20 Omega cm) and n- type (1.8 - 2.6. Omega cm) Czochralski (Cz) silicon wafers were treated by a RF (13.56 MHz) hydrogen plasma at a substrate temperature of 250degreesC. After the plasma hydrogenation subsequent annealing was applied up to 600degreesC in air. The formation of H-2 molecules in voids/ platelets was investigated by Raman spectroscopy. The Raman intensities of the H-2 vibration modes at similar to4150 cm(-1) exhibited significant intensity modulations in dependence on the annealing temperature. The intensities of the H2 Raman lines indirectly monitor the evolution of the voids/ platelets upon annealing. This assumption was verified by cross-sectional transmission electron microscopy (XTEM), which was applied for comparison. The intensity modulations of the H2 Raman signal can be explained by the evolution of {111} and {001} platelets. At lower annealing temperatures (< 500 degrees C) platelets laying in {111} planes are dominant, while at elevated temperatures (>= 500 degrees C) [001]- oriented platelets become more and more important. {110} platelets were also observed using XTEM measurements in p- type material. In case of p-type substrates the Raman intensities were significant higher than for n-type material. The higher H-2 Raman intensities in p- type Cz Si can be explained by the amphoteric character of hydrogen in silicon.