Patent ID: 7201942

Claim:
A process for coating substrates, comprising: providing a reactor having reactor walls at least partly defining a reaction chamber; providing first and second source containers outside the reaction chamber containing first and second precursors, respectively; providing a susceptor having a surface for holding a substrate inside the reaction chamber; providing a gas inlet unit inside the reaction chamber, the gas inlet unit including a first plenum and a second plenum having a baseplate, the baseplate being located opposite the susceptor surface and having an area substantially equal to the area of the susceptor surface such that the baseplate and the susceptor surface define a reaction space therebetween; heating the first and second source containers separately from each other to first and second sublimation temperatures, respectively; communicating the first and second precursors to the first and second plenums, respectively; heating the first plenum to produce a positive temperature gradient with respect to the first sublimation temperature, and heating the second plenum separately from the first plenum to produce a positive temperature gradient with respect to the second sublimation temperature; heating the reactor walls to a temperature greater than the temperature of the susceptor; maintaining the temperature of the susceptor lower than the temperature of the second plenum to produce a negative temperature gradient with respect to the temperature of the second plenum; and communicating the first precursors from the first plenum into the reaction space, and separately communicating the second precursors from the second plenum into the reaction space.