Solvent prewet and method to dispense the solvent prewet

Abstract

A method and apparatus is provided for more efficient application of photoresist to a wafer surface. One aspect of the method comprises applying solvent to the wafer and spinning it to coat the entire wafer surface prior to the application of photoresist. This reduces surface tension on the wafer and reduces the amount of resist required to achieve a high quality film. The apparatus comprises adding a third solenoid and nozzle to the coating unit to accommodate the application of solvent to the center of the wafer surface. The method also describes incorporating a new solvent comprising diacetone alcohol, which is a low-pressure solvent, providing extended process latitudes and reduced material expenditures.

1 . A semiconductor wafer, comprising: 
 a semiconductive substrate having a diameter including a plurality of conductive, insulative and semiconductive layers;    a layer of a first solvent disposed upon substantially the entirety of a top surface of the semiconductive substrate, wherein the first solvent includes diacetone alcohol at a volume percentage of between 70% and 90% and aliphatic ester; and    a liquid photosensitive material including a second solvent, having a preselected volume disposed in a central portion of the semiconductive substrate.    
   
   
       2 . The semiconductor wafer of  claim 1 , wherein the preselected volume of the liquid photosensitive material is between 0.5 cc to 1.4 cc on a semiconductive substrate having a diameter of approximately 8 inches.  
   
   
       3 . The semiconductor wafer of  claim 2 , wherein the preselected volume of the liquid photosensitive material is approximately 1.0 cc on a semiconductive substrate having a diameter of approximately 8 inches.  
   
   
       4 . The semiconductor wafer of  claim 1 , wherein the first solvent has a volume of less than 0.3 cc on a semiconductive substrate having a diameter of approximately 8 inches.  
   
   
       5 . The semiconductor wafer of  claim 1;  wherein the second solvent is a different material from the first solvent.  
   
   
       6 . The semiconductor wafer of  claim 1 , wherein the first solvent is a wetting agent for the liquid photosensitive material and has a rate of evaporation that is from 5 to 10 times slower than an evaporation rate for at least one of ethyl lactate and propyleneglycol monomethylether acetate.  
   
   
       7 . The semiconductor wafer of  claim 1 , wherein the aliphatic ester has a volume percentage of between 10% and 30%.  
   
   
       8 . The semiconductor wafer of  claim 1 , wherein the diacetone alcohol has a volume percentage of approximately 70%, and aliphatic ester has a volume percentage of approximately 30%.  
   
   
       9 . The semiconductor wafer of  claim 1 , wherein the diacetone alcohol has a volume percentage of approximately 90%, and aliphatic ester has a volume percentage of approximately 10%.  
   
   
       10 . The semiconductor wafer of  claim 1 , wherein the liquid photosensitive material comprises a photo resist.  
   
   
       11 . A semiconductor wafer, comprising: 
 a semiconductive substrate having a diameter including a plurality of conductive, insulative and semiconductive layers;    a layer of a first solvent disposed upon substantially the entirety of a top surface of the semiconductive substrate, wherein the first solvent includes aliphatic ester at a volume percentage of between 10% and 30% and diacetone alcohol; and    a liquid photosensitive material including a second solvent, having a preselected volume disposed in a central portion of the semiconductive substrate.    
   
   
       12 . The semiconductor wafer of  claim 11 , wherein the diacetone alcohol has a volume percentage of between 70% and 90%.  
   
   
       13 . The semiconductor wafer of  claim 11 , wherein the diacetone alcohol has a volume percentage of approximately 70%, and aliphatic ester has a volume percentage of approximately 30%.  
   
   
       14 . The semiconductor wafer of  claim 11 , wherein the diacetone alcohol has a volume percentage of approximately 90%, and aliphatic ester has a volume percentage of approximately 10%.  
   
   
       15 . The semiconductor wafer of  claim 11 , wherein the second solvent is a different material from the first solvent.  
   
   
       16 . A semiconductor wafer, comprising: 
 a semiconductive substrate having a diameter including a plurality of conductive, insulative and semiconductive layers;    a layer of a first solvent disposed upon substantially the entirety of a top surface of the semiconductive substrate, wherein the first solvent includes diacetone alcohol at a volume percentage of between  70 % and  90 % and aliphatic ester; and    a photosensitive material including a second solvent, disposed upon substantially the entirety of a top surface of the semiconductive substrate.    
   
   
       17 . The semiconductor wafer of  claim 16 , wherein a thickness of the photosensitive material has a variation from an average thickness of less than 50 ? across a semiconductive substrate having a diameter of approximately 8 inches.  
   
   
       18 . The semiconductor wafer of  claim 16 , wherein the first solvent is a wetting agent for the photosensitive material.  
   
   
       19 . The semiconductor wafer of  claim 18 , wherein the first solvent includes aliphatic ester at a volume percentage of between 10% and 30%.  
   
   
       20 . The semiconductor wafer of  claim 19 , wherein the first solvent includes diacetone alcohol at a volume percentage of approximately 70%, and aliphatic ester at a volume percentage of approximately 30%.  
   
   
       21 . The semiconductor wafer of  claim 19 , wherein the diacetone alcohol has a volume percentage of approximately 90%, and aliphatic ester has a volume percentage of approximately 10%.  
   
   
       22 . The semiconductor wafer of  claim 16 , wherein the liquid photosensitive material comprises a photo resist.  
   
   
       23 . The semiconductor wafer of  claim 22 , wherein the second solvent is a different material from the first solvent and the photo resist does not absorb the entirety of the first solvent, leaving at least a monolayer of the first solvent in contact with the semiconductive substrate.  
   
   
       24 . The semiconductor wafer of  claim 22 , wherein a portion of the photo resist located within a predetermined distance from an edge of the semiconductive substrate is substantially removed and replaced by the first solvent.  
   
   
       25 . The semiconductor wafer of  claim 24 , wherein the predetermined distance from the edge is an edge bead where the photo resist layer is more than 100? thicker than an average thickness of the photo resist.  
   
   
       26 . A semiconductor wafer, comprising: 
 a semiconductive substrate having a diameter;    a partially dried layer of a solvent comprising a diacetone alcohol having a volume percentage of between 70% and 90%, and an aliphatic ester having a volume percentage of between 10% and 30% disposed upon substantially the entirety of a top surface of the semiconductive substrate; and    a photo resist material having a thickness disposed upon substantially the entirety of the top surface of the semiconductive substrate, wherein the photo resist has a thickness uniformity of plus and minus 50? across at least 90% of the diameter of semiconductive substrate.    
   
   
       27 . The semiconductor wafer of  claim 26 , wherein the diameter is approximately 8 inches.  
   
   
       28 . The semiconductor wafer of  claim 26 , wherein the diacetone alcohol has a volume percentage of approximately 70%, and aliphatic ester has a volume percentage of approximately 30%.  
   
   
       29 . The semiconductor wafer of  claim 26 , wherein the photo resist material has a solvent different from diacetone alcohol and aliphatic ester, and the solvent layer is not entirely absorbed by the photo resist.  
   
   
       30 . The semiconductor wafer of  claim 26 , wherein the photo resist layer stops at a predetermined distance of an edge of the semiconductive substrate.  
   
   
       31 . The semiconductor wafer of  claim 30 , wherein the predetermined distance is approximately 0.5 cm.  
   
   
       32 . A semiconductor wafer, comprising: 
 a substrate;    a layer of a solvent comprising a diacetone alcohol having a volume percentage of approximately 90%, and an aliphatic ester having a volume percentage of approximately 10%; and    a photo resist material having a thickness uniformity of plus and minus 50? across at least 90% of the diameter of the substrate.    
   
   
       33 . The semiconductor wafer of  claim 32 , wherein the substrate has a diameter of approximately 8 inches.  
   
   
       34 . The semiconductor wafer of  claim 33 , wherein the photo resist layer stops at a predetermined distance of an edge of the semiconductive substrate.  
   
   
       35 . The semiconductor wafer of  claim 34 , wherein the predetermined distance is approximately 0.5 cm.