US Patent 7294207 Gas-admission element for CVD processes, and device

The invention relates to a method for depositing especially, crystalline layers onto especially, crystalline substrates. At least two process gases are led into a process chamber of a reactor separately from each other, through a gas inlet mechanism above a heated susceptor. The first process gas flows through a central line with a central outlet opening and the second process gas flows through a line which is peripheral thereto and which has a peripheral outlet opening that is formed by a gas-permeable gas outlet ring. Said gas outlet ring surrounds a ring-shaped pre-chamber. The invention provides that in order to avoid a parasitic deposition in the area of the peripheral outlet opening, the end section of the gas outlet ring that faces towards the susceptor or the radially outer section of the surface of the gas outlet mechanism surrounding the central outlet opening is cooled by the second process gas according to a truncated cone or revolution hyperboloid shape of a gas guiding surface formed by the pre-chamber back wall.