Apparatus and Method for Providing Resist Alignment Marks in a Double Patterning Lithographic Process

Abstract

A method is described for alignment of a substrate during a double patterning process. A first resist layer containing at least one alignment mark is formed on the substrate. After the first resist layer is developed, a second resist layer is deposited over the first resist layer, leaving a planar top surface (i.e., without topography). By baking the second resist layer appropriately, a symmetric alignment mark is formed in the second resist layer with little or no offset error from the alignment mark in the first resist layer. The symmetry of the alignment mark formed in the second resist can be enhanced by appropriate adjustments of the respective thicknesses of the first and second resist layers, the coating process parameters, and the baking process parameters.

1 . An article of manufacture, comprising:
 a substrate;   a first resist layer coating the substrate;   a first lithography pattern formed in the first resist layer, wherein the first lithography pattern includes one or more first alignment marks;   a second resist layer on the first resist layer; and   one or more second alignment marks formed in the second resist layer by baking the second resist layer, wherein the one or more second alignment marks are based on the one or more first alignment marks and are used to support alignment of lithographic patterning of the second resist layer to the first lithography pattern.   
     
     
         2 . The article of manufacture of  claim 1 , wherein the one or more second alignment marks are symmetric. 
     
     
         3 . The article of manufacture of  claim 1 , wherein the first resist layer is characterized by a first thickness and the second resist layer is characterized by a second thickness, and wherein a feature size within the second alignment marks is based on a relationship between the first thickness and the second thickness. 
     
     
         4 . The article of manufacture of  claim 1 , wherein the first resist layer is characterized by a first thickness and the second resist layer is characterized by a second thickness, and wherein based on the first thickness and the second thickness, a sub-segmentation of the first alignment marks is used in part to form the one or more second alignment marks. 
     
     
         5 . The article of manufacture of  claim 1 , wherein the first resist layer is characterized by a first thickness and the second resist layer is characterized by a second thickness, and wherein symmetric one or more second alignment markers are based on the relationship between the first thickness and the second thickness. 
     
     
         6 . A lithographic system, comprising:
 an illumination source configured to provide a radiation beam; and   a processed substrate located to receive the radiation beam, and comprising:
 a substrate; 
 a first resist layer coating the substrate; 
 a first lithography pattern formed in the first resist layer, wherein the first lithography pattern includes one or more first alignment marks; 
 a second resist layer coating the first resist layer; and 
 one or more second alignment marks formed in the second resist layer by baking the second resist layer, wherein the one or more second alignment marks are based on the one or more first alignment marks and are used to support alignment of lithographic patterning of the second resist layer to the first lithography pattern. 
   
     
     
         7 . The lithographic system of  claim 6 , wherein the one or more second alignment marks are symmetric. 
     
     
         8 . The lithographic system of  claim 6 , wherein the first resist layer is characterized by a first thickness and the second resist layer is characterized by a second thickness, and wherein a feature size within the second alignment marks is based on a relationship between the first thickness and the second thickness. 
     
     
         9 . The lithographic system of  claim 6 , wherein the first resist layer is characterized by a first thickness and the second resist layer is characterized by a second thickness, and wherein based on the first thickness and the second thickness, a sub-segmentation of the first alignment marks is used in part to form the one or more second alignment marks. 
     
     
         10 . The lithographic system of  claim 6 , wherein the first resist layer is characterized by a first thickness and the second resist layer is characterized by a second thickness, and wherein symmetric one or more second alignment markers are based on the relationship between the first thickness and the second thickness. 
     
     
         11 . The lithographic system of  claim 6 , further comprising:
 a detector configured to receive an alignment radiation and output an alignment signal, wherein the alignment radiation results from an interaction between the radiation beam and the one or more second alignment marks.   
     
     
         12 . A method of forming a desired resist alignment mark with a desired mark topography in a double patterning process that includes processing a first resist layer, the method comprising:
 planarizing a mark profile of an initial resist alignment mark located in the first resist layer during coating of a second resist layer; and   creating the desired mark topography of the desired resist alignment mark by curing the second resist layer.