Method and apparatus for depositing thin films on a surface

Abstract

A method and apparatus for depositing thin films onto a substrate is provided. The apparatus includes a gas injection structure that is positioned within a reaction chamber that has a platform. The gas injection structure may be positioned above or below the platform and comprises a first gas injector and a second gas injector. The first gas injector is in fluid communication with a first reactant source and a purge gas source. Similarly, the second gas injector is in fluid communication with a second reactant source and a purge gas source. The first and second injectors include hollow tubes with apertures opening to the reaction chamber. In one configuration, the tubes are in the form of interleaved branching tubes forming showerhead rakes. Methods are provided for deposition, in which multiple pulses of purge and reactant gases are provided for each purge and reactant step.

We claim: 
     
       1. An apparatus for depositing a thin film on a substrate, comprising:
 a reaction chamber having a reaction space; 
 a substrate holder for holding the substrate horizontally within the reaction space; 
 a gas outlet in fluid communication with the reaction space; and  
 a gas injector structure positioned with the reaction chamber fixed relative to the substrate during deposition, the gas injector structure comprising:
 a first gas injector being in fluid communication with a first reactant gas source and a purge gas source, the first gas injector positioned outside a circumference of the substrate at a first angular position relative to the substrate, the first angular position defined by a first aperture of the first gas injector located closest to the substrate, the first aperture configured to supply a first reactant vapor from the first reactant gas source to the substrate in a first direction; and 
 a second gas injector being in fluid communication with a second reactant gas source and a purge gas source;, the second gas injector positioned outside a circumference of the substrate at a second angular position relative to the substrate, the second angular position defined by a second aperture of the second gas injector located closest to the substrate, the second aperture configured to supply a second reactant vapor from the second reactant gas source to the substrate in a second direction,  
 
 wherein the first and second gas injectors include hollow tubes extending in the reaction space, the hollow tubes including a plurality of gas flow apertures spaced along respective tube axes of elongation, the apertures opening to the reaction space, the plurality of gas flow apertures including at least the first aperture and the second aperture, 
 wherein the gas outlet is positioned outside the circumference of the substrate at a third angular position relative to the substrate, the third angular position defined by a point on the gas outlet located closest to the substrate, the gas outlet configured to exhaust each of the first reactant vapor and the second reactant vapor in a third direction from the substrate to the gas outlet, wherein each of the first, second and third angular positions are different and angularly spaced from each other outside the circumference of the substrate, 
 wherein the first injector, the second injector and the gas outlet are positioned such that the first reactant vapor turns over the substrate from the first direction to the third direction, including turning in a horizontal plane, and 
 wherein the apparatus further comprises controls configured to alternately pulse the first and the second reactant vapors into the reaction space. 
 
     
     
       2. The apparatus of  claim 1 , wherein the gas injector structure is between about 10-60 mm above the substrate holder. 
     
     
       3. The apparatus of  claim 1 , wherein the substrate holder is an end effector of a wafer handler. 
     
     
       4. The apparatus of  claim 1 , wherein the substrate holder is a platform comprising a heated susceptor plate. 
     
     
       5. The apparatus of  claim 1 , wherein the substrate holder holds the substrate in place by operation of the Bernoulli principle. 
     
     
       6. The apparatus of  claim 1 , wherein the gas injector structure is below the substrate holder. 
     
     
       7. The apparatus of  claim 6 , wherein the substrate holder is a vacuum chuck. 
     
     
       8. The apparatus of  claim 1 , wherein the first and the second gas injectors each include a spiral-shaped portion, and the spiral-shaped portion the first injector is interlaced with the spiral-shaped portion of the second gas injector. 
     
     
       9. The apparatus of  claim 1 , wherein the apertures have a circular shape. 
     
     
       10. The apparatus of  claim 1 , wherein the apertures have an ovular shape. 
     
     
       11. The apparatus of  claim 1 , wherein the first and second gas injectors include distributor tube sections on opposite sides of the substrate holder. 
     
     
       12. The apparatus of  claim 11 , wherein the apertures are formed on the distributor tube sections and the apertures of the first and second gas injectors substantially face each other in a plane adjacent the substrate. 
     
     
       13. The apparatus of  claim 11 , wherein the apertures are formed on the distributor tube sections and the apertures of the first and second gas injectors substantially face away from each other in a plane adjacent the substrate. 
     
     
       14. The apparatus of  claim 11 , wherein each of the first and second gas injectors includes a plurality of hollow fingers branching from their respective distributor tube sections, the apertures being formed on the hollow fingers. 
     
     
       15. The apparatus of  claim 14 , wherein the hollow fingers of each injector extend parallel to one another. 
     
     
       16. The apparatus of  claim 15 , wherein the hollow fingers of the first gas injector alternate with the hollow fingers of the second gas injector across an injection plane. 
     
     
       17. The apparatus in  claim 1 , wherein the apertures are each spaced between about 10-30 mm apart along their respective tube axes of elongation. 
     
     
       18. The apparatus in  claim 1 , wherein the gas outlet is fluidly connected to a vacuum. 
     
     
       19. The apparatus in  claim 1 , wherein the gas outlet communicates with a venturi. 
     
     
       20. The apparatus in  claim 1 , wherein the hollow tubes are positioned such that exhaust flows, in sequence, from the substrate, between the hollow tubes of the first and second gas injectors, and into the gas outlet. 
     
     
       21. The apparatus in  claim 20 , wherein the gas outlet is positioned in a plane above the gas injection structure and the substrate holder is positioned below the gas injection structure. 
     
     
       22. The apparatus of  claim 1 , wherein the hollow tubes comprise a plurality of first hollow fingers for the first gas injector and a plurality of second hollow fingers for the second gas injector. 
     
     
       23. The apparatus of  claim 22 , wherein the hollow tubes further comprise:
 a first distributor tube communicating gas to each of the first fingers; and   a second distributor tube communicating gas to each of the second fingers.   
     
     
       24. The apparatus of  claim 1 , wherein the first injector is positioned between the second injector and the substrate holder. 
     
     
       25. The apparatus of  claim 1 , wherein the gas injector structure further comprises a third gas injector in fluid communication with a third reactant gas source and the purge gas source, wherein the third gas injector includes a hollow tube extending in the reaction space, the hollow tube including a plurality of gas flow apertures spaced along an axis of tube elongation, the apertures opening to the reaction space, wherein the third injector is positioned outside the circumference of the substrate at a fourth angular position relative to the substrate, the fourth angular position defined by a third aperture of the third gas injector located closest to the substrate, the third aperture configured to supply a third reactant vapor, different from the first and second reactant vapors, to the substrate in a fourth direction; wherein each of the first, second, third and fourth angular positions are different and angularly spaced from each other outside the circumference of the substrate. 
     
     
       26. The apparatus of  claim 1 , further comprising a gas flow restrictor positioned between the reaction space and the gas outlet. 
     
     
       27. The apparatus of  claim 1 , further comprising controls for wherein the controls are further configured to alternately providing provide first reactant flow to the first gas injector while stopping second reactant flow to the second gas injector and providing to provide second reactant flow to the second gas injector while stopping first reactant flow to the first gas injector. 
     
     
       28. The apparatus of claim  27  1, further comprising:
 a first purge channel communicating purge gas to the first injector; 
 a first reactant channel communicating the first reactant vapor to the first gas injector; 
 a second purge channel communicating purge gas to the second gas injector; and 
 a first second reactant channel communicating the second reactant vapor to the second gas injector, 
 wherein the first and second purge gas channels are more restrictive than the first and second reactant channels, respectively. 
 
     
     
       29. The apparatus of  claim 28 , further comprising at least one booster valve selectively communicating purge gas to the first and second reactant channels, the controls providing a booster purge gas pulse to the first and second reactant channels during an initial pulse of a purge gas step while providing only purge gas through the first and second purge channels during a second pulse of the purge gas step. 
     
     
       30. An apparatus for depositing thin films on a substrate, comprising:
 a reaction chamber; 
 a substrate support configured to receive a substrate disposed within the reaction chamber; and 
 a showerhead rake structure positioned adjacent the substrate support comprising:
 a first gas injector having a first rake in fluid communication with a first reactant source, the first rake including a plurality of first fingers extending from and in fluid communication with a first gas distribution structure, each of the first fingers having first apertures along a length thereof; and 
 a second gas injector positioned opposite from the first gas injector having a second rake in fluid communication with a second reactant source, the second rake including a plurality of second fingers extending from and in fluid communication with a second distribution structure, each of the second fingers having second apertures along a length thereof; 
 wherein the first reactant source comprises a first precursor and the second reactant source comprises a second precursor, the second precursor being reactive with chemisorbed first precursor on the substrate. 
 
 
     
     
       31. The apparatus of  claim 30 , wherein the first gas injector comprises a first distributor tube extending within the reaction chamber and the second distribution structure comprises a second distributor tube extending within the reaction chamber. 
     
     
       32. The apparatus of  claim 30 , wherein the first fingers are parallel to one another and the second fingers are parallel to one another. 
     
     
       33. The apparatus of  claim 32 , wherein the first fingers are staggered with the second fingers across a gas injection plane adjacent the substrate support. 
     
     
       34. The apparatus in  claim 33 , wherein a distance between one of the first fingers and an adjacent one of the second finger is between about 1-50 mm. 
     
     
       35. The apparatus in  claim 30 , wherein the showerhead rake structure is positioned adjacent the substrate support to face and distribute gas across a major surface of the substrate supported thereon. 
     
     
       36. The apparatus in  claim 35 , wherein the showerhead rake structure is positioned between about 5-50 mm above the substrate support. 
     
     
       37. The apparatus in  claim 36 , wherein the substrate support is a platform comprising a heated susceptor plate. 
     
     
       38. The apparatus in  claim 35 , wherein the showerhead rake structure is positioned below the platform. 
     
     
       39. The apparatus in  claim 38 , wherein the substrate support is a vacuum chuck. 
     
     
       40. The apparatus in  claim 30 , wherein the apertures of each finger are spaced between about 10-30 mm apart along a surface of the finger parallel to a finger axis. 
     
     
       41. The apparatus in  claim 30 , further comprising a gas outlet in fluid communication with the reaction chamber, wherein the gas outlet comprises:
 a channel for restricting gas flow; and
 an exhaust duct in fluid communication with the channel. 
 
 
     
     
       42. The apparatus of  claim 30 , further comprising a gas outlet in fluid communication with the reaction chamber, the showerhead rake structure being positioned between the outlet and the substrate. 
     
     
       43. The apparatus of  claim 30 , wherein the substrate support is held fixed relative to the showerhead structure during deposition. 
     
     
       44. The apparatus of claim 1, wherein the gas outlet serves as the sole gas outlet in fluid communication with the reaction space.  
     
     
       45. The apparatus of claim 1, wherein the controls are configured to provide intervening purges steps between alternating pulses of the first and second reactant vapors to the reaction space.  
     
     
       46. The apparatus of claim 1, wherein the controls are further configured to alternately provide the first reactant vapor to the reaction space while flow of the second reactant vapor into the reaction space is prevented and to provide the second reactant vapor to the reaction space while flow of the first reactant vapor into the reaction space is prevented.  
     
     
       47. The apparatus of claim 46, wherein the controls are further configured to alternately provide a purge gas to the reaction space while flow of the second reactant vapor to the reaction space is prevented and to provide a purge gas to the reaction space while flow of the first reactant vapor to the reaction space is prevented.  
     
     
       48. The apparatus of claim 28, wherein the controls are further configured to prevent the second reactant vapor from flowing to the substrate while the first reactant vapor is being provided to the first gas injector and to prevent the first reactant vapor from flowing to the substrate while the second reactant vapor is being provided to the second gas injector.  
     
     
       49. The apparatus of claim 1, wherein the controls are further configured to alternately provide in sequence:
 the first reactant vapor to the first gas injector while preventing flow of the second reactant vapor to the second gas injector and providing a purge gas to the second gas injector;   purge gas to the first and second gas injectors while preventing flow of the first and second reactant vapors to the first and second gas injectors;   the second reactant vapor to the second gas injector while preventing flow of the first reactant vapor to the first gas injector and providing purge gas to the first gas injector; and   purge gas to the first and second gas injectors while preventing flow of the first and second reactant vapors to the first and second gas injectors.    
     
     
       50. The apparatus of claim 1, wherein the first and second gas injectors and the gas outlet are configured to provide nonlaminar flow of the first and second reactant vapors over the substrate.  
     
     
       51. The apparatus of claim 1 wherein a flow pattern modifier is positioned within the gas outlet.  
     
     
       52. The apparatus of claim 51 wherein the flow pattern modifier is positioned in the middle of the gas outlet.  
     
     
       53. The apparatus of claim 1, wherein the first injector, the second injector and the gas outlet are positioned such that the second reactant vapor turns over the substrate from the second direction to the third direction, including turning in a horizontal plane.