Patent ID: 6899764

Claim:
A chemical vapor deposition reactor having a process chamber accommodating a substrate holder for wafers, a first inlet providing a first gas flow of reactive gases to process the wafers and a crown-shaped gas collector surrounding the substrate-holder, said gas collector forming a hollow annular space and comprises apertures to let the reactive gases exhaust from the process chamber, wherein said reactor further comprises: a base plate and a cover plate disposed respectively beneath and above the substrate-holder, an outer ring surrounding the gas-collector and touching both the base plate and the cover-plate, wherein the process chamber defines a first space, which first space is limited by the base and cover plates and the outer ring and an inlet for a second flow of non-reactive gases, characterized in that the first space is surrounded by second and third spaces limited by a substantially cylindrical peripheral wall, a lower horizontal wall and a cover, wherein one wall comprises the inlet for the second flow and that said second flow acting as a counter-flow for preventing the first reactive gas flow to exit from the process chamber but through the gas-collector.