A new large volume microwave plasma source has been used for the production of a hydrogen plasma. The source consists of an annular waveguide cavity with axial slots on the inner side which acts as a field applicator to sustain a plasma at 2.45 GHz. The plasma is contained in a fused silica bell jar of 16 cm in diameter and 20 cm in height. The distance between the slots corresponds to a waveguide wavelength. The source is able to generate a highly dissociated (up to 90%) hydrogen plasma for cleaning purposes. Stable operation of the plasma source is shown for a pressure range of 0.1–1.3 mbar and a power range of 600–2000 W. The plasma can be ignited over the entire examined pressure range, and the power needed for discharge ignition is below 1.7 kW. The minimum ignition power is 1050 W for a pressure of 0.7 mbar. A double Langmuir probe and optical emission spectroscopy were used to characterize the hydrogen plasma as a function of microwave power, pressure, and position. The results indicated a typical ion density of 1.5×1011 cm−3 which is an order of magnitude less than that obtained for argon under similar conditions. The typical electron temperature is 2.5 eV for microwave power of 2 kW and pressure of 0.7 mbar.

This study addresses the formation of roughness and near surface defects on Si(100) surfaces that are exposed to a remotely excited H plasma. The remote H plasma processing can be employed for in situ wafer cleaning. Atomic force microscopy, transmission electron microscopy, and residual gas analysis are used to measure the surface roughness, the near surface defects, and the etching, respectively. For remote H plasma exposures at substrate temperatures ≤300 °C, etching is observed along with a significant increase in the surface roughness and the formation of platelet defects in the near surface region. As the substrate temperature is increased to above 450 °C, etching is significantly reduced and no subsurface defects or increases in surface roughness are observed.

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This study details low pressure and low temperature cleaning of Si(100) surfaces. The properties of Si surfaces exposed to variations in plasma generated H are described. The diagnostic techniques used to study the processing conditions are residual gas analysis (RGA) and emission spectroscopy. The surface is characterized by low energy electron diffraction (LEED) and angle resolved uv-photoemission spectroscopy (ARUPS). During the cleaning, Si complexes are formed which indicates the removal of species from the Si(100) surface. Plasma cleaning at 300°C results in a Si(100) surface with 2×1 surface diffraction patterns as detected by LEED. Measurements by ARUPS with He I radiation show the absence of Si surface states on the Hpassivated surface. The ARUPS measurements also indicate that the H begins to desorb from the Si(100) H-passivated surface at ∼500°C.