Effect of a vacuum ion gauge on the contamination of a hydrogen-passivated silicon surface

Abstract

The effect of operating a vacuum ion gauge on carbonaceous (C) contamination of a hydrogen (H)-passivated Si surface before epitaxial growth was investigated. The dependence of C contamination on the residence time in the loading chamber, tlc, was determined with or without operating a vacuum ion gauge. The results showed that C contamination of a H-passivated surface was greatly increased by use of the ion gauge. With ion gauge operation in a vacuum of 1×10−6–1×10−7 Torr in the loading chamber, the configuration of the ion gauge and upside down-stacked wafers is shown to be a dominant factor of C contamination of the Si surface. The presence of C contaminants could be determined by observing SiC diffraction patterns using in situ reflection high energy electron diffraction (RHEED), since the C contaminants reacted with Si to produce single crystalline SiC at a temperature as high as 850 °C. The RHEED patterns demonstrated that the single crystalline SiC had a zinc-blende structure. Single crystalline SiC islands with an ellipsoidal cross section were observed by high resolution transmission electron microscopy. In the subsequent epitaxial growth of Si, a well oriented single crystalline Si layer could be grown over the SiC islands although the effect of C contamination on the electrical characteristics of the interface was not clarified. Longer tlc with the ion gauge also required a higher temperature to achieve a 2×1 reconstructed surface structure from the H-passivated Si surface.

Linewidths in bound state resonances for helium scattering from Si(111)–(1 × 1)H

“…The scattering chamber is equipped with an ion gauge and mass spectrometer for measuring the chamber pressure and sample reflectivity respectively. These were not used during the experiment, to avoid the possibility of surface degradation from the ionizing filaments [15]. After measurements had been completed, the scattering chamber pressure and the helium reflectivity were measured.…”