Temperature dependency of the kinetics of PureB CVD deposition over patterned Si/SiO₂ surfaces

Temperature dependency of the kinetics of PureB CVD deposition over patterned Si/SiO₂ surfaces has been investigated. It has been shown that there is a large difference between layers deposited at either 400 °C or 700 °C. The latter are very smooth with a roughness less than 2 angstrom (Å) for 2-nm-thick layers. They deposit selectively on the Si surfaces regardless of the Si window size while at lower temperatures like 400 °C the deposition rate drops considerably, and for micron-sized small windows surrounded by large oxide areas the oxide at the perimeter will readily be covered with an irregular, very rough and loosely-bonded deposition of boron. This can degrade the adhesion of subsequent layers which is shown here for plasma-enhanced chemical-vapor-deposited (PECVD) oxide or physical-vapor- deposited (PVD) Al. Some precautions are given for reducing the parasitic B-deposition on oxide surfaces. Besides process and chamber parameters, the local oxide to Si area ratio (LOR) is the one of the parameters that can be adjusted. For example, the oxide surrounding millimeter-large windows may be free of boron deposition due to a reduction of the boron available for deposition outside the window.