Wafer centrifugal drying apparatus

Abstract

A centrifugal wafer drying apparatus comprises a rotor rotatably disposed in a container, a cradle mounted on the rotor, and a carrier mounted in the cradle and having grooves for receiving wafers. The carrier holds the wafers at an oblique angle with respect to a plane normal to the axis of rotation of the rotor, at least during rotation of the rotor.

What is claimed is:  
     
       1. A centrifugal wafer drying apparatus comprising 
       a container having an opening through which air is supplied,  
       a rotor rotatably disposed in the container, being rotatable about an axis of rotation,  
       a cradle mounted on the rotor, and  
       a carrier mounted in the cradle and having grooves for receiving wafers, the carrier holding the wafers at an oblique angle with respect to a plane normal to the axis of rotation of the rotor, at least during rotation of the rotor.  
     
     
       2. An apparatus according to  claim 1 , wherein the oblique angle is within the range of about 2.5° to about 30°. 
     
     
       3. An apparatus according to  claim 1 , wherein the cradle is pivotable about a pivot axis at right angles with the axis of rotation of the rotor, the cradle being pivotable between a first position at which the carrier can be loaded in and unloaded out of the cradle and a second position at which the cradle is held during rotation of the rotor. 
     
     
       4. An apparatus according to  claim 3 , wherein the carrier has an opening for loading an unloading the wafers in and out of the grooves, the opening facing the axis of rotation when the cradle is in the second position. 
     
     
       5. An apparatus according to the  claim 3 , wherein each of the grooves extend to cover half of the periphery of a wafer that is positioned on the radially outer side with respect to the axis of rotation of the rotor when the cradle is in the second position. 
     
     
       6. An apparatus according to  claim 3 , wherein the carrier receives wafers in a stack, the surfaces of the wafers are substantially normal to the direction of the stack, and the direction of the stack is inclined with respect to the axis of rotation of the rotor when the cradle is in the second position. 
     
     
       7. An apparatus according to  claim 1 , wherein the grooves have a clearance with respect to the thickness of the wafer. 
     
     
       8. An apparatus according to  claim 1 , wherein the carrier has an opening for loading and unloading the wafers in and out of the grooves, the opening facing the axis of rotation when the rotor is rotating. 
     
     
       9. An apparatus according to  claim 1 , wherein each of the grooves extend to cover half of the periphery of a wafer that is positioned on the radially outer side with respect of the axis of rotation of the rotor when the rotor is rotating. 
     
     
       10. An apparatus according to  claim 1 , wherein the carrier receives wafers in a stack, the surfaces of the wafers are substantially normal to the direction of the stack, and the direction of the stack is inclined with respect to the axis of rotation of the rotor when the rotor is rotating. 
     
     
       11. A wafer centrifugal drying apparatus comprising: 
       a container having an opening through which air is supplied, 
       a rotor rotatable about a substantially vertical axis, and  
       a carrier mounted on the rotor and having grooves for receiving wafers, the carrier holding the wafers at an oblique angle with respect to a plane normal to the axis of rotation of the rotor, at least during rotation of the rotor.  
     
     
       12. A method of drying a semiconductor wafer, having a surface that was previously wetted with a liquid, by rotation to exert a centrifugal force, and by an air stream, on the wafer, said method comprising 
       rotating the wafer about an axis of rotation, and  
       holding the wafer in a manner such that the surface of the wafer is inclined at a fixed angle with respect to a plane normal to the axis of the rotation, and  
       
         supplying air to the inclined wafer so as to create the air stream around the surface of the wafer.  
       
     
     
       13. A method according to  claim 12 , wherein the angle of inclination is within the range of about  2 . 5 ° to about  30 °. 
     
     
       14. An apparatus according to  claim 11 , wherein the oblique angle is within the range of about  2 . 5 ° to about  30 °. 
     
     
       15. An apparatus according to  claim 1 , further comprising means for holding the cradle at a fixed position relative to the rotor to maintain the wafers at the oblique angle relative to the plane normal to the axis of rotation of the rotor during rotation of the rotor. 
     
     
       16. An apparatus according to  claim 1 , wherein the wafers are pressed against and maintained against an upper portion of the grooves during rotation of the rotor. 
     
     
       17. An apparatus according to  claim 11 , further comprising means for holding the cradle at a fixed position relative to the rotor to maintain the wafers at the oblique angle to the plane normal to the axis of rotation of the rotor during rotation of the rotor. 
     
     
       18. An apparatus according to  claim 11 , wherein the wafers are pressed against and maintained against an upper portion of the grooves during rotation of the rotor. 
     
     
       19. A method according to  claim 12 , wherein the step of holding the wafer further includes; holding the wafer in a groove within a carrier and pressing and maintaining the wafer against an upper portion of said grooves during rotation of the wafer. 
     
     
       20. A centrifugal wafer drying apparatus comprising 
       a container having an opening through which air is supplied;  
       a rotor rotatably disposed in said container, said rotor being rotatable about an axis of rotation;  
       a cradle mounted on said rotor;  
       a carrier mounted in said cradle, said carrier having grooves for receiving said wafers; and  
       a stop means for holding said cradle at a fixed position relative to said rotor to maintain said wafers at an oblique angle relative to a plane normal to said axis of rotation.  
     
     
       21. An apparatus according to  claim 1 , wherein the container opening is in fluid communication with the grooves. 
     
     
       22. An apparatus according to  claim 21 , wherein the cradle is tilted with respect to the rotor such that a radially outer bottom edge of the cradle is disposed on a bottom surface of the rotor and a radially inner bottom edge of the cradle is disposed above the bottom surface of the rotor. 
     
     
       23. An apparatus according to  claim 22 , further including a spacer attached to the cradle and abutting the container to fix the oblique angle. 
     
     
       24. An apparatus according to  claim 11 , wherein the container opening is in fluid communication with the grooves. 
     
     
       25. An apparatus according to  claim 24 , wherein the carrier is tilted with respect to the rotor such that a radially outer bottom edge of the carrier is disposed on a bottom surface of the rotor and a radially inner bottom edge of the carrier is disposed above the bottom surface of the rotor. 
     
     
       26. A method according to  claim 12 , wherein holding the wafer includes holding the wafer in a cradle, wherein the cradle is arranged such that a radially outer bottom edge of the cradle is disposed on a first plane normal to the axis of the rotation and a radially inner bottom edge of the cradle is disposed on a second plane normal to the axis of the rotation, wherein the second plane is disposed above the first plane. 
     
     
       27. A method according to  claim 26 , wherein the angle of inclination of the wafers is fixed by abutment of a spacer that is attached to the carrier. 
     
     
       28. A method according to  claim 12 , wherein rotating the wafer about the axis of the rotation includes drying the wafer until no drops of the liquid remain on the surface of the wafer. 
     
     
       29. An apparatus according to  claim 20 , wherein the container opening is in fluid communication with the grooves. 
     
     
       30. An apparatus according to  claim 29 , wherein the cradle is tilted with respect to the rotor such that a radially outer bottom edge of the cradle is disposed on a bottom surface of the rotor and a radially inner bottom edge of the cradle is disposed above the bottom surface of the rotor. 
     
     
       31. An apparatus according to  claim 30 , wherein the stop means includes a spacer attached to the cradle and abutting the container to fix the oblique angle. 
     
     
       32. A method of drying a semiconductor wafer having a surface that was previously wetted with a liquid, said method comprising: 
       
         holding the wafer in a carrier;  
       
       
         tilting the carrier in a manner such that a rear bottom edge of the carrier is disposed on a rotational base plane normal to an axis of the rotation and a front bottom edge of the carrier is disposed above the base plane, and further such that the surface of the wafer is inclined at a fixed angle with respect to the base plane;  
       
       
         rotating the wafer about the axis of the rotation, to exert a centrifugal force on drops of the liquid; and  
       
       
         providing an air stream to the surface of the wafer to reduce a vibration of the wafer;  
       
       
         wherein both rotating the wafer and providing the air stream disperse the drops of the liquid on the surface of the wafer. 
       
     
     
       33. A method according to  claim 32 , wherein the angle of inclination is within the range of about  2 . 5 ° to about 30°. 
     
     
       34. The method of  claim 32 , wherein the surface of the wafer remains inclined at the fixed angle an entire time of the rotating. 
     
     
       35. A method according to  claim 32 , wherein the front bottom edge of the carrier is closer to the axis of rotation than is the rear bottom edge of the carrier. 
     
     
       36. A method according to  claim 32 , wherein rotating the wafer about the axis of the rotation includes drying the wafer until no drops of the liquid remain on the surface of the wafer. 
     
     
       37. A method according to  claim 32 , wherein tilting the carrier includes tilting the carrier until an angle of inclination of the wafers is fixed by abutment of a spacer that is disposed parallel to the bottom surface of the cradle.