Oxygen plasma treatment for a nitride surface to reduce photo footing

Abstract

The present invention includes a method for preventing distortion in semi-conductor fabrication. The method comprises providing a substrate comprising a film comprising silicon nitride. The substrate is treated in a vacuum of about 3.0-6.5 Torr in an atmosphere comprising oxygen plasma wherein the oxygen plasma flow rate is at least about 300 sccm oxygen. A resist is applied to the treated substrate and the resist is patterned over the treated substrate.

1 . A method for reducing profile distortion in semiconductor fabrication comprising: 
 providing a semiconductor substrate bearing a film comprising silicon-nitride;    exposing oxygen gas to microwave energy of about 150-900 watts to make oxygen plasma;    treating the film in a vacuum of about 3.0-6.5 Torr, for a time of about 10 seconds to about 5 minutes, and in an atmosphere free of argon and comprising oxygen plasma as the gas present in the greatest concentration, wherein the oxygen plasma flow rate is at least about 300 sccm oxygen;    applying a resist;    patterning the resist; and    treating the resist with UV light.    
   
   
       2 . The method of  claim 1  wherein the oxygen plasma is made by electromagnetic excitation of oxygen gas by electrodes that are about 400 to 600 mils apart.  
   
   
       3 . The method of  claim 1  wherein the reduced profile distortion is footing.  
   
   
       4 . The method of  claim 1  wherein the reduced profile distortion is undercutting.  
   
   
       5 . The method of  claim 1  further comprises removing the resist from the silicon nitride film with reduced profile distortion.  
   
   
       6 . The method of  claim 1  wherein the oxygen flow rate is not greater than about 2000 sccm.  
   
   
       7 . The method of  claim 1  and further comprising adding an inert gas to the oxygen gas.  
   
   
       8 . A method for making a microcircuit having a uniform symmetry comprising: 
 treating a silicon-nitride film in a vacuum of about 3.0-6.5 Torr, for a time of about 10 seconds to about 5 minutes, and in an atmosphere consisting essentially of oxygen plasma as the gas present in the greatest concentration, wherein the oxygen plasma is maintained at an oxygen flow rate of at least about 300 sccm oxygen to about 2000 sccm and a helium flow rate of about 400 to 1000 sccm and the atmosphere renders the substrate resistant to profile distortion and roughening to make a treated substrate wherein the oxygen plasma is generated exposing oxygen gas to microwave energy;    applying a resist to the treated substrate;    treating the resist with UV light; and    patterning the resist to form a microcircuit.    
   
   
       9 . The method of  claim 8  and further including exposing oxygen gas to a microwave energy source generating about 150-900 watts in order to make the oxygen plasma.  
   
   
       10 . The method of  claim 8  wherein the reduced profile distortion is footing.  
   
   
       11 . The method of  claim 8  wherein the reduced profile distortion is undercutting.  
   
   
       12 . The method of  claim 8  and further including removing the resist from the silicon nitride film with reduced profile distortion.  
   
   
       13 . A method for reducing losses in wafer manufacturing, the method comprising: 
 treating a film comprising silicon-nitride in a vacuum of about 3.0-6.5 Torr, for a time of about 10 seconds to about 5 minutes, and in an atmosphere consisting essentially of oxygen plasma as the gas present in the greatest concentration wherein the oxygen plasma comprises oxygen at a flow rate of at least about 300 sccm to about 2000 sccm wherein the oxygen plasma is made by an exposure to oxygen gas to microwave energy, and helium in a concentration of about 400 to 1000 sccm, to make a treated substrate; and    patterning a resist applied to the treated substrate.    
   
   
       14 . The method of  claim 13  wherein the reduced profile distortion is footing.  
   
   
       15 . The method of  claim 13  wherein the reduced profile distortion is undercutting.  
   
   
       16 . A method for reducing profile distortion in semiconductor fabrication comprising: 
 treating a layer of silicon-nitride with an oxygen plasma in a vacuum of about 3.0-6.5 Torr; and    patterning a photo resist applied after treating the silicon-nitride.    
   
   
       17 . The method of  claim 16  wherein treating the layer of silicon-nitride comprises treating the layer in the vacuum for a time of about 10 seconds to about 5 minutes, and in an atmosphere free of argon and comprising the oxygen plasma as the gas present in the greatest concentration, wherein the oxygen plasma flow rate is at least about 300 sccm oxygen.  
   
   
       18 . The method of  claim 16  wherein treating the layer comprises treating the layer in the vacuum for a time of about 10 seconds to about 5 minutes, and in an atmosphere consisting essentially of the oxygen plasma as the gas present in the greatest concentration, wherein the oxygen plasma is maintained at an oxygen flow rate of at least about 300 sccm oxygen to about 2000 sccm oxygen and a helium flow rate of about 400 to 1000 sccm helium.  
   
   
       19 . The method of  claim 16  wherein the oxygen plasma is made by an exposure to oxygen gas to microwave energy.  
   
   
       20 . The method of  claim 16  wherein the oxygen plasma is made by exposing oxygen gas to RF energy of about 150-900 watts.  
   
   
       21 . A method for reducing profile distortion in a photo resist comprising: 
 treating a layer of silicon-nitride with an oxygen plasma in a vacuum of about 3.0-6.5 Torr; and performing a UV lithography operation to the photo resist applied after treating the silicon-nitride.