Vacuum science considerations for rapid reactor recovery with extremely low oxygen in low temperature low pressure chemical vapor deposition of Si1−xGex and Si1−x−yGexCy films

Abstract

The films for this study were grown in the AMAT Centura 5200 low pressure chemical vapor deposition (LPCVD) reactor. Silicon germanium (SixGe1−x) and silicon germanium carbon (Si1−x−yGexCy) have widely been accepted as the materials of choice for a variety of uses in semiconductor devices. Most manufacturers utilize LPCVD for the low temperature growth of these films. Due to the reaction kinetics, oxygen incorporation in SiGe films may become substantial, especially following a major preventive maintenance (PM). Depending on the technology, elevated oxygen may be unacceptable due to process and device performance considerations. These considerations range from oxygen reaction with dopant source gases, thus minimizing dopant incorporation and activation, to minority carrier lifetime reduction in the base of a SiGe heterojunction bipolar transistor due to oxygen related defects. To achieve low oxygen processes the engineer must have a clear picture of the mechanisms and the fundamental vacuum science as it relates to LPCVD processing. Outgassing and the all too familiar chamber leak rate are discussed as they relate to sorption and sorbtion effects and recommendations are made to facilitate very rapid PM recoveries with sustained in-film oxygen levels as good as attained with ultrahigh vacuum CVD. Secondary ion mass spectrometry profiles are presented, which demonstrate that a sustained sub-1017at.∕cc oxygen level in low temperature LPCVD SiGe processing is possible when these types of gas loads are addressed.