Semiconductor surfaces are cleaned by exposure to hydrogen or argon plasma, because the plasma exposure eliminates contaminated carbon and native oxide from the surfaces. However, the exposure to these plasmas often induces roughness, amorphization , defects and other damage to the surface. Therefore, it is necessary for the plasma cleaning of semiconductor surfaces to observe both surface cleanliness and damage. We have applied the direct recoil (DR) surface analysis method to the in situ observation of the semiconductor surfaces exposed to electron cyclotron resonance plasmas. First, we have investigated the best condition for the hydrogen plasma cleaning of the Si (100) surface. Next, we examined how the surface roughness and damage were detected on the Si surfaces cleaned by hydrogen or argon plasmas. As a result, it has been clarified that the hydrogen-terminated Si clean surface without surface roughness and damage is obtained by exposure to the hydrogen plasma with an electron density of the order of 10⁹cm^-3 at 300°C for a few minutes. It is also shown that the surface roughness and amorphization induced by the plasma exposure can be detected by the profile changes of the scattered-Ar peak or the azimuthal dependence of the peak intensities.

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