System and method for etching a mask

Abstract

A system and method for transferring a pattern from an overlying layer into an underlying layer, while laterally trimming a feature present within the pattern is described. The pattern transfer is performed using an etch process according to a process recipe, wherein at least one variable parameter within the process recipe is adjusted given a target trim amount. The adjustment of the variable parameter is achieved using a process model established for relating trim amount data with the variable parameter.

1 . A method of preparing a process model comprising: 
 defining a nominal process recipe for transferring a pattern having a first feature size from an overlying layer to an underlying layer on a substrate, wherein said nominal process recipe comprises at least one variable parameter and at least one constant parameter;    accumulating trim amount data as a function of said at least one variable parameter by measuring the trim amount for one or more values of said at least one variable parameter; and    curve-fitting said trim amount data as a function of said at least one variable parameter.    
   
   
       2 . The method of  claim 1 , wherein said curve-fitting includes fitting said trim amount data as a function of said variable parameter with an expression of the form y=(x+a)/(bx+c), where a, b, and c are constants, and where x is the at least one variable parameter and y is the trim amount.  
   
   
       3 . An etching system comprising: 
 a process chamber;    a substrate holder coupled to said process chamber, and configured to support a substrate;    a plasma source coupled to said process chamber, and configured to form plasma in said process chamber;    a gas injection system coupled to said process chamber, and configured to introduce a process gas to said process chamber; and    a controller coupled to said process chamber, said substrate holder, said plasma source, or said gas injection system, or any combination of two or more thereof, and configured to execute a process recipe in order to transfer a pattern having a feature with a first critical dimension in an overlying layer to an underlying layer on said substrate, while reducing said first critical dimension to a second critical dimension by a target trim amount set by a process model.    
   
   
       4 . The etching system of  claim 3 , wherein said target trim amount is set by determining a difference between said first critical dimension and said second critical dimension.  
   
   
       5 . The etching system of  claim 3 , wherein said process model relates said target trim amount to a variable parameter in a process recipe.  
   
   
       6 . The etching system of  claim 5 , wherein said variable parameter includes a flow rate of CF 4 , a flow rate of O 2 , a chamber pressure, a RF power to an upper electrode, or a RF power to a lower electrode, or any combination of two or more thereof.  
   
   
       7 . The etching system of  claim 5 , wherein said process gas comprises a first process gas and a second process gas, and said variable parameter includes an amount of said first process gas, an amount of said second process gas, a total amount of said first process gas and said second process gas, a chamber pressure, or at least one RF power, or any combination of two or more thereof.  
   
   
       8 . The etching system of  claim 7 , wherein determining said variable parameter includes determining said amount of said first process gas from said process model, and determining said amount of said second process gas from said amount of said first process gas and said total amount of said first process gas and said second process gas.  
   
   
       9 . The etching system of  claim 3 , wherein said process model relates said target trim amount (y) to a variable parameter (x) in a process recipe according to a relationship of the form y=(x+a)/(bx+c), where a, b, and c are constants.  
   
   
       10 . The etching system of  claim 3 , wherein said underlying layer includes a film formed by spin-on deposition and/or vapor deposition.  
   
   
       11 . The etching system of  claim 3 , wherein said underlying layer includes an organic layer.  
   
   
       12 . The etching system of  claim 3 , wherein said overlying layer includes a film formed by spin-on deposition and/or vapor deposition.  
   
   
       13 . The etching system of  claim 3 , wherein said overlying layer includes a layer of light-sensitive material.  
   
   
       14 . The etching system of  claim 3 , wherein said pattern in said overlying layer is formed by micro-lithography.  
   
   
       15 . The etching system of  claim 3 , wherein said substrate holder comprises an electrostatic clamping system.  
   
   
       16 . The etching system of  claim 3 , wherein said plasma source comprises an electrode configured to capacitively couple power to said process gas.  
   
   
       17 . The etching system of  claim 3 , wherein said plasma source comprises a coil configured to inductively couple power to said process gas.  
   
   
       18 . The etching system of  claim 3 , wherein said substrate holder is configured to control a temperature of said substrate.  
   
   
       19 . The etching system of  claim 3 , wherein said process gas comprises a C x F y  containing gas (wherein x, y are integers greater than or equal to unity), and an oxygen containing gas.  
   
   
       20 . The etching system of  claim 19 , wherein said C x F y  containing gas includes CF 4 , C 2 F 6 , C 3 F 6 , C 4 F 6 , C 4 F 8 , or C 5 F 8  or any combination of two or more thereof, and said oxygen containing gas includes O 2 , CO, CO 2 , NO, NO 2 , or N 2 O, or any combination of two or more thereof.