Electrode Patterning

Abstract

A method is provided to isolated conductive pads on top of a multi-layer polymer device structure. The method utilizes laser radiation to ablate conductive material and create a non-conductive path, electrically isolating the conductive pads. The process is self-limiting and incorporates at least one layer within the stack that absorbs the radiation at the required wavelength. The prevention of radiation degradation of the underlying layers is achieved, as absorption of radiation occurs primarily on the surface of the structure, but not in any of the radiation sensitive underlying layers of the electronic device. The method preferably uses low energy infrared radiation which has been shown to produce little debris and no device degradation.

1 . A method of forming a conductive element on an organic electronic structure on a substrate, the method comprising:
 depositing a layer of dielectric material on said organic electronic structure; and   depositing a layer of conducting material over said layer of dielectric material; and wherein the method further includes:   providing a light absorbing material over said organic electronic structure and under an upper surface of said layer of conducting material; and   irradiating portions of the substrate with light absorbed by said light absorbing material such that said conducting material is selectively removed from said irradiated substrate portions.   
     
     
         2 . A method as claimed in  claim 1  wherein said light absorbing material comprises a dye. 
     
     
         3 . A method as claimed in  claim 1  wherein said conducting material provides said light absorbing material. 
     
     
         4 . A method as claimed in  claim 1  wherein said conducting material comprises a conducting polymer. 
     
     
         5 . A method as claimed in  claim 1  wherein said light comprises ultraviolet light. 
     
     
         6 . A method as claimed in  claim 1  wherein said dielectric material comprises a polymer dielectric. 
     
     
         7 . A method as claimed in  claim 1  wherein the thickness of said dielectric material is greater than 1 micron. 
     
     
         8 . A method as claimed in  claim 7  wherein the thickness of said dielectric material is greater than 3 microns. 
     
     
         9 . A method as claimed in  claim 1  wherein said dielectric material provides said light absorbing material. 
     
     
         10 . A method as claimed in  claim 1  further comprising depositing a layer of said light absorbing material under said layer of conducting material. 
     
     
         11 . A method as claimed in  claim 1  wherein said light absorbing material has an optical density of at least 0.3, preferably at least 0.5 at a wavelength of said irradiating. 
     
     
         12 . A method as claimed in  claim 1  wherein said layer of dielectric material has a thickness of greater than one micron. 
     
     
         13 . A method as claimed in  claim 1  wherein a wavelength of said irradiation is selected such that said during said irradiating more light is absorbed by said light absorbing material than by said underlying organic electronic structure. 
     
     
         14 . A method as claimed in  claim 1  wherein said dielectric layer has a thermal conductivity of less than 10 −2  W/cm·K. 
     
     
         15 . A method as claimed in  claim 1 , the method further comprising providing a wetting interface or layer beneath said layer of conducting material. 
     
     
         16 . A method as claimed in  claim 1 , the method further comprising providing a de-wetting interface or layer beneath said layer of conducting material. 
     
     
         17 . A method as claimed in  claim 1  wherein said organic electronic structure comprises an active electronic device, and wherein said conductive element comprises an electrode for said device. 
     
     
         18 . A method as claimed in  claim 1  wherein said selective removal is self-limiting. 
     
     
         19 . A method of fabricating an active matrix display or image sensor, the method comprising:
 forming an electrode on a substrate for the active matrix display or image sensor using the method of  claim 1 , wherein said organic electronic structure comprises a thin film transistor, and wherein said layer of conducting material comprises a pixel electrode layer; and   fabricating said active matrix display or image sensor using said substrate with said electrode.   
     
     
         20 . A substrate configured for conductive layer patterning using light, the substrate comprising:
 an organic electronic structure;   a layer of dielectric material over said electronic device; and   a layer of conducting material over said layer of dielectric material; and wherein   the substrate further includes a light absorbing material over said organic electronic structure and under an upper surface of said layer of conducting material.   
     
     
         21 . A substrate as claimed in  claim 20  wherein said light absorbing material comprises a dye. 
     
     
         22 . A substrate as claimed in  claim 20  wherein said light absorbing material is provided in a light absorbing layer between said layer of conducting material and said organic electronic structure. 
     
     
         23 . A substrate as claimed in  claim 20  wherein said light absorbing material is provided in at least one of said layer of conducting material and said layer of dielectric material. 
     
     
         24 . A substrate as claimed in  claim 20  wherein said light absorbing material has an absorption of at least 0.3 at a wavelength in the range 150 nm to 11000 nm, preferably in the range 600 nm to 2000 nm. 
     
     
         25 . A substrate as claimed in  claim 24  wherein when irradiated from a side closest to said layer of conducting material by light at a said wavelength said irradiating light is more strongly absorbed by said light absorbing material than by said organic electronic structure. 
     
     
         26 . A substrate as claimed in  claim 20  after irradiation of portions of the substrate, wherein said conducting material is substantially absent from said irradiated substrate portions, and wherein a quantity of said light absorbing material in said irradiated substrate portions is reduced compared to un-irradiated substrate portions. 
     
     
         27 . An active matrix display including the substrate of  claim 26 .