Multiple epitaxial Si film deposition by APCVD for power semiconductors

Epitaxial films are essential for power MOSFETs. Stacking of epitaxial layers is one major concept to realize superjunction power devices. The growth of epi layers on top of each other creates significant challenges particularly when processing 300 mm substrates. Single and multiple depositions are carried out in different tools and were investigated with the emphasis on epitaxial film properties such as thickness uniformity as well as structural and crystallographic features. A significant improvement of thickness uniformity in 300 mm compared to 200 mm is achieved due to more tuning possibilities which are offered at the 300 mm epi tools. Experiments at different epi growth temperatures show an increase in surface haze at higher growth temperatures as well as with an increasing number of epi runs. A higher thermal budget and a large number of epi depositions result in slip line formation at the wafer edge. Different temperature gradient profiles during epi growth are tested. It is shown that a warm edge region compared to the wafer center yields almost no slip even after a large number of consecutive epi runs.