Method for the rapid processing of polymer layers in support of imidization processes and fan out wafer level packaging including efficient drying of precursor layers

Abstract

A process for the drying, and subsequent imidization, of polyimide precursors which minimizes or eliminates voids and which minimizes or eliminates discoloration. The process uses a sequential set of descending pressure operations that allow for time efficient processing of wafers. The set of descending pressure operations are interspersed with evacuation processes using heated gasses, which combine heating and byproduct evacuation. The process results in layers with reduced or eliminated voiding, discoloration, and solvent retention.

I claim: 
     
       1. A process for drying of substrates in support of temperature imidization of polymer layers, said process comprising the steps of:
 inserting one or more substrates into a process chamber, said one or more substrates coated with a layer of a polyimide precursor, said polyimide precursor comprising N-Methyl-2-pyrrolidone; 
 reducing the pressure in said process chamber to a first drying pressure; 
 first, flushing said process chamber with inert gas to a first flushing pressure; 
 reducing the pressure in said process chamber to a second drying pressure after said first flushing, wherein said second drying pressure is lower than said first drying pressure; 
 second, flushing said process chamber with inert gas to a second flushing pressure after the step of reducing the pressure in said process chamber to a second drying pressure; 
 reducing the pressure in said process chamber to a third drying pressure after the step of second flushing said process chamber, wherein said third drying pressure is lower than said second drying pressure; and 
 third, flushing said process chamber with inert gas to a third flushing pressure after the step of reducing the pressure in said process chamber to a third drying pressure. 
 
     
     
       2. The process of  claim 1  wherein said process chamber is heated to a first chamber temperature. 
     
     
       3. The process of  claim 2  wherein said first flushing said process chamber with inert gas comprises flushing with inert gas heated to a first gas temperature. 
     
     
       4. The process of  claim 3  wherein said second flushing said process chamber with inert gas comprises flushing with inert gas heated to a second gas temperature. 
     
     
       5. The process of  claim 4  wherein said third flushing said process chamber with inert gas comprises flushing with inert gas heated to a third gas temperature. 
     
     
       6. The process of  claim 5  wherein said first chamber temperature is in the range of 135 C to 180 C. 
     
     
       7. The process of  claim 6  wherein said first drying pressure is in the range of 30-60 Torr. 
     
     
       8. The process of  claim 6  wherein said first drying pressure is in the range of 30-50 Torr. 
     
     
       9. The process of  claim 8  wherein said second drying pressure is in the range of 15-30 Torr. 
     
     
       10. The process of  claim 9  wherein said third drying pressure is in the range of 1-15 Torr. 
     
     
       11. The process of claim  1  6 wherein said first gas temperature is in the range of 135 C-180 C. 
     
     
       12. The process of  claim 11  wherein said first gas temperature is and said first chamber temperature have a temperature value in the range of 135 C-180 C. 
     
     
       13. The process of  claim 11  wherein said second gas temperature is in the range of 135 C-180 C. 
     
     
       14. The process of claim  12  13 wherein said first chamber temperature, said first gas temperature, and said second gas temperature is have a temperature value in the range of 135 C-180 C. 
     
     
       15. The process of  claim 13  wherein said second third gas temperature is in the range of 135 C-180 C. 
     
     
       16. The process of claim  14  15 wherein said first chamber temperature, said first gas temperature, said second gas temperature is, and said third gas temperature have a temperature value in the range of 135 C-180 C. 
     
     
       17. The process of claim  16  1 further comprising the step of temperature imidizing a polymer layer on said one or more substrates the layer of polyimide precursor after the step of third flushing said process chamberwhile having maintained the low oxygen level of the drying steps. 
     
     
       18. The process of claim 17, wherein the step of temperature imidizing occurs at a temperature between 350-375 C.  
     
     
       19. The process of claim 1, wherein said first flushing pressure, said second flushing pressure, and said third flushing pressure have a same pressure value.  
     
     
       20. The process of claim 19, wherein the same pressure value is between 550 to 760 Torr.  
     
     
       21. A method for curing polymer coated substrates, comprising:
 (a) placing one or more substrates including a polymer layer in a process chamber of a process oven;   (b) reducing the pressure in the process chamber to a first drying pressure;   (c) after step (b), flushing the process chamber with heated inert gas;   (d) after step (c), reducing the pressure in the process chamber to a second drying pressure lower than the first drying pressure;   (e) after step (d), flushing the process chamber with heated inert gas; and   (f) after step (e), temperature imidizing the polymer layer of the one or more substrates.    
     
     
       22. The method of claim 21, further including, after step (e) and before step (f), reducing the pressure in the process chamber to a third drying pressure lower than the second drying pressure.  
     
     
       23. The method of claim 22, further including, after reducing the pressure in the process chamber to the third drying pressure and before step (f), flushing the process chamber with heated inert gas.  
     
     
       24. The method of claim 22, wherein the first drying pressure is between 30-60 Torr, the second drying pressure is between 15-30 Torr, and the third drying pressure is between 1-15 Torr.  
     
     
       25. The method of claim 21, wherein the first drying pressure is between 30-60 Torr and the second drying pressure is between 15-30 Torr.  
     
     
       26. The method of claim 21, wherein, before step (b), heating the process chamber to a temperature between 135-180 C.  
     
     
       27. The method of claim 26, wherein flushing the process chamber in steps (c) and (e) includes flushing the process chamber with heated inert gas to a pressure in the range of 550-760 Torr.  
     
     
       28. The method of claim 27, wherein flushing the process chamber in steps (c) and (e) includes flushing the process chamber with inert gas heated to a same temperature as the process chamber.  
     
     
       29. The method of claim 21, wherein the inert gas is nitrogen.  
     
     
       30. The method of claim 21, wherein temperature imidizing the polymer layer includes heating the process chamber to an imidization temperature between 350-375 C, and maintaining the process chamber at the imidization temperature for an hour.  
     
     
       31. A method for curing polymer coated substrates, comprising:
 (a) heating the process chamber of a process oven to a first temperature;   (b) after step (a), placing one or more substrates including a polymer layer in the heated process chamber;   (c) after step (b), reducing the pressure in the process chamber to a pressure between 30-60 Torr;   (d) after step (c), flushing the process chamber with heated inert gas at the first temperature to increase the pressure in the process chamber to a value between 550-760 Torr;   (e) after step (d), reducing the pressure in the process chamber to a pressure between 15-30 Torr;   (f) after step (e), flushing the process chamber with heated inert gas at the first temperature to increase the pressure in the process chamber to a value between 550-760 Torr;   (g) after step (f), temperature imidizing the polymer layer of the one or more substrates.    
     
     
       32. The method of claim 31, wherein the first temperature is between 135-180 C.