Photoresist collapse method for forming a physical unclonable function

Abstract

An organic material layer is lithographically patterned to include a linear array portion of lines and spaces. In one embodiment, the organic material layer can be an organic planarization layer that is patterned employing a photoresist layer, which is consumed during patterning of the organic planarization layer. Volume expansion of the organic planarization layer upon exposure to a halogen-including gas causes portions of the linear array to collapse at random locations. In another embodiment, the height of the photoresist layer is selected such that the linear array portion of the photoresist layer is mechanically unstable and produces random photoresist collapses. The pattern including random modifications due to the collapse of the organic material layer is transferred into an underlying layer to generate an array of conductive material lines with random electrical disruption of shorts or opens. The structure with random shorts can be employed as a physical unclonable function.

1 . A method of forming an electronic structure comprising:
 forming a vertical stack including an organic planarization layer and a photoresist layer over a substrate;   lithographically patterning said photoresist layer with a lithographic pattern that includes a linear periodic array of lines having a uniform width;   patterning said organic planarization layer by transferring a pattern in said photoresist layer into said organic planarization layer;   causing said patterned organic planarization layer to randomly collapse in at least one location; and   transferring a pattern of said randomly collapsed organic planarization layer into a material layer within said substrate.   
     
     
         2 . The method of  claim 1 , wherein random collapse of said patterned organic planarization layer is effected by exposing said patterned organic planarization layer to a halogen-including gas. 
     
     
         3 . The method of  claim 2 , wherein said hydrogen atoms in said patterned organic planarization layer are randomly replaced with halogen atoms within said halogen-including gas. 
     
     
         4 . The method of  claim 2 , wherein said halogen-including gas is selected from a hydrofluorocarbon gas, fluorine gas, hydrofluoric acid vapor, a halogen fluoride gas, chlorine gas, and hydrochloric acid vapor. 
     
     
         5 . The method of  claim 1 , wherein said material layer includes a conductive material, and said method further comprises depositing a dielectric material layer over patterned portions of said material layer. 
     
     
         6 . The method of  claim 1 , wherein said material layer includes a dielectric material, and said method further comprises filling cavities within said dielectric material with a conductive material, said cavities formed by said transfer of said pattern of said randomly collapsed organic planarization layer. 
     
     
         7 . A method of forming an electronic structure comprising:
 forming a photoresist layer over a substrate;   lithographically exposing said photoresist layer with a lithographic pattern that includes a linear periodic array of lines having a uniform width;   developing said photoresist layer while remaining portions of said photoresist layer randomly collapse in at least one location during development; and   transferring a pattern of said developed and randomly collapsed photoresist layer into a layer within said substrate.   
     
     
         8 . The method of  claim 7 , wherein said lithographic pattern further includes:
 first non-periodic lines attached to one end of each of said linear periodic array of lines and including portions wider than said linear periodic array of lines; and   second non-periodic lines attached to another end of each of said linear periodic array of lines and including portions wider than said linear periodic array of lines.   
     
     
         9 . The method of  claim 7 , wherein a height of said photoresist layer is selected such that a portion of said photoresist layer having said uniform width has a random probability of collapse in a range from 10% to 80%. 
     
     
         10 . The method of  claim 7 , wherein said material layer includes a conductive material, and said method further comprises depositing a dielectric material layer over patterned portions of said material layer. 
     
     
         11 . The method of  claim 7 , wherein said material layer includes a dielectric material, and said method further comprises filling cavities within said dielectric material with a conductive material, said cavities formed by said transfer of said pattern of said randomly collapsed organic planarization layer. 
     
     
         12 .- 20 . (canceled)