Coating method

1. 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.

2. The process of claim 1 , wherein the step of communicating the first and second precursors to the first and second plenums comprises communicating the first and second precursors through first and second lines, respectively, and heating the first and second lines to maintain the temperatures of the first and second precursors at least equal to the first and second sublimation temperatures, respectively.

3. The process of claim 1 , wherein the gas inlet unit comprises nozzles passing through the second plenum for communicating the first precursors from the first plenum to the reaction area without mixing with the second precursors in the second plenum.

4. The process of claim 3 , wherein the second plenum is heated to produce a positive temperature gradient with respect to the temperature of the first plenum.

5. The process of claim 1 , further comprising selecting a velocity at which the precursor are communicated into the reaction space that avoids local Bernoulli effects.

6. The process of claim 1 , further comprising regulating the pressures in each source container by controlling a valve and purging inert gas.

7. The process of claim 1 , wherein the source containers, reactor walls, and plenums are heated with electrically active components.

8. The process of claim 1 , wherein the susceptor is cooled using a liquid.

9. The process of claim 1 , wherein the precursors are communicated to the plenums via a carrier gas.

10. The process of claim 9 , wherein the carrier gas comprises Ar, H 2 , N 2 , or He.

11. The process of claim 1 , further comprising providing sensors and corresponding passages in the reactor walls for measuring properties of the substrate or layers thereon.

12. The process of claim 1 , wherein the susceptor is adapted to hold substrates that are round, polygonal, flat, or curved.

13. The process of claim 1 , further comprising the step of masking the substrate.

14. 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 having a first plenum and a second plenum adjacent the susceptor;

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 chamber, and separately communicating the second precursors from the second plenum into the reaction chamber.

15. The process of claim 14 , wherein the step of communicating the first and second precursors to the first and second plenums comprises communicating the first and second precursors through first and second lines, respectively, and heating the first and second lines to maintain the temperatures of the first and second precursors at least equal to the first and second sublimation temperatures, respectively.

16. The process of claim 14 , wherein the gas inlet unit comprises nozzles passing through the second plenum for communicating the first precursors from the first plenum to the reaction area without mixing with the second precursors in the second plenum.

17. The process of claim 16 , wherein the second plenum is heated to produce a positive temperature gradient with respect to the temperature of the first plenum.

18. The process of claim 14 , further comprising selecting a velocity at which the precursor are communicated into the reaction space that avoids local Bernoulli effects.

19. The process of claim 14 , further comprising regulating the pressures in each source container by controlling a valve and purging inert gas.

20. The process of claim 14 , wherein the source containers, reactor walls, and plenums are heated with electrically active components.

21. The process of claim 14 , wherein the susceptor is cooled using a liquid.

22. The process of claim 14 , wherein the precursors are communicated to the plenums via a carrier gas.

23. The process of claim 22 , wherein the carrier gas comprises Ar, H 2 , N 2 , or He.

24. The process of claim 14 , further comprising providing sensors and corresponding passages in the reactor walls for measuring properties of the substrate or layers thereon.

25. The process of claim 14 , wherein the susceptor is adapted to hold substrates that are round, polygonal, flat, or curved.

26. The process of claim 14 , further comprising the step of masking the substrate.

27. A process for coating substrates, comprising:

providing a reactor having reactor walls at least partly defining a reaction chamber;

providing a plurality of source containers located outside the reaction chamber for supplying precursors;

providing a susceptor having a surface for holding a substrate inside the reaction chamber;

providing a gas inlet unit inside the reaction chamber and in communication with the source containers, the gas inlet unit having a baseplate located opposite the susceptor surface, the baseplate 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 source containers;

communicating the precursors from the source containers to the gas inlet unit;

heating the reactor walls to a temperature greater than the temperature of the susceptor;

maintaining the temperature of the susceptor lower than the temperatures of the gas inlet unit and the reactor walls; and

communicating the precursors from the gas inlet unit into the reaction space.