High mobility stabile metal oxide tft

Abstract

A method of fabricating a stable, high mobility metal oxide thin film transistor includes the steps of providing a substrate, positioning a gate on the substrate, and depositing a gate dielectric layer on the gate and portions of the substrate not covered by the gate. A multiple film active layer including a metal oxide semiconductor film and a metal oxide passivation film is deposited on the gate dielectric with the passivation film positioned in overlying relationship to the semiconductor film. An etch-stop layer is positioned on a surface of the passivation film and defines a channel area in the active layer. A portion of the multiple film active layer on opposite sides of the etch-stop layer is modified to form an ohmic contact and metal source/drain contacts are positioned on the modified portion of the multiple film active layer.

1 . A metal oxide thin film transistor comprising:
 a substrate;   a gate positioned on an upper surface of the substrate;   a gate dielectric layer positioned on the gate and portions of the substrate not covered by the gate;   a multiple film active layer positioned on the gate dielectric layer;   an etch-stop layer covering a portion of the multiple film active layer and defining a channel area in the active layer;   metal source/drain contacts positioned on the active layer on opposite sides of the etch-stop layer; and   the multiple films of the active layer including a metal oxide semiconductor film and a metal oxide passivation film, the metal oxide passivation film being positioned between the metal oxide semiconductor film and the etch-stop layer and having a major upper surface contacting the etch-stop layer in the channel area and the metal source/drain contact areas on each side of the channel area, and the metal oxide passivation film includes aluminum.   
     
     
         2 . A metal oxide thin film transistor as claimed in  claim 1  wherein the metal oxide semiconductor film of the active layer has a mobility >20 cm 2 /Vs. 
     
     
         3 . A metal oxide thin film transistor as claimed in  claim 2  wherein the metal oxide semiconductor film of the active layer includes indium. 
     
     
         4 . A metal oxide thin film transistor as claimed in  claim 1  wherein the metal oxide passivation film of the active layer includes a metal that can be selectively modified by exposure to a strong base material. 
     
     
         5 . (canceled) 
     
     
         6 . A metal oxide thin film transistor as claimed in  claim 1  wherein the metal oxide semiconductor film of the active layer includes one of In 2 O 3  and InZnO and the passivation film of the active layer includes one of InAlZnO and AlZnO. 
     
     
         7 . A metal oxide thin film transistor as claimed in  claim 1  wherein the etch-stop layer includes an organic passivation material. 
     
     
         8 . A metal oxide thin film transistor as claimed in  claim 1  wherein the multiple film active layer includes a contact layer between the metal oxide passivation film and the etch-stop layer and the metal source/drain contacts. 
     
     
         9 . A metal oxide thin film transistor as claimed in  claim 8  wherein the etch-stop layer includes an oxygen donating material. 
     
     
         10 . A metal oxide thin film transistor as claimed in  claim 1  wherein the multiple films of the active layer further include a thin film of oxygen bonded metal adjacent the gate dielectric layer. 
     
     
         11 . A metal oxide thin film transistor as claimed in  claim 10  wherein the thin film of oxygen bonded metal is less than 5 molecular layers thick. 
     
     
         12 . A metal oxide thin film transistor comprising:
 a substrate;   a gate positioned on an upper surface of the substrate;   a gate dielectric layer positioned on the gate and portions of the substrate not covered by the gate;   a multiple film active layer positioned on the gate dielectric layer;   an etch-stop layer covering a portion of the multiple film active layer and defining a channel area in the active layer, the etch stop layer including an oxygen donating material;   metal source/drain contacts positioned on the active layer on opposite sides of the etch-stop layer; and   the multiple films of the active layer including a metal oxide semiconductor film, a metal oxide passivation film, and a contact film, the metal oxide passivation film being positioned between the metal oxide semiconductor film and the contact film and the contact film being positioned between the metal oxide passivation film and the etch-stop layer.   
     
     
         13 . A metal oxide thin film transistor comprising:
 a substrate;   a gate positioned on an upper surface of the substrate;   a gate dielectric layer positioned on the gate and portions of the substrate not covered by the gate;   a multiple film active layer positioned on the gate dielectric layer;   an etch-stop layer covering a portion of the multiple film active layer and defining a channel area in the active layer, the etch stop layer including an oxygen donating material;   metal source/drain contacts positioned on the active layer on opposite sides of the etch-stop layer; and   the multiple films of the active layer including a thin film of oxygen bonded metal adjacent the gate dielectric layer, the oxygen bonded metal having a thickness less than approximately 5 molecular layers.   
     
     
         14 . A metal oxide thin film transistor comprising:
 a substrate;   a gate positioned on an upper surface of the substrate;   a gate dielectric layer positioned on the gate and portions of the substrate not covered by the gate;   a multiple film active layer positioned on the gate dielectric layer;   an etch-stop layer covering a portion of the multiple film active layer and defining a channel area in the active layer;   metal source/drain contacts positioned on the active layer on opposite sides of the etch-stop layer; and   the multiple films of the active layer including a metal oxide semiconductor film and a metal oxide passivation film, the metal oxide passivation film being positioned between the metal oxide semiconductor film and the etch-stop layer, and the metal source/drain contacts being positioned on the metal oxide semiconductor film.   
     
     
         15 - 34 . (canceled) 
     
     
         35 . In a metal oxide thin film transistor including a substrate, a gate positioned on the substrate, a gate dielectric layer positioned on the gate and portions of the substrate not covered by the gate, an active layer positioned on the gate dielectric layer, and an etch-stop layer positioned on the active layer so as to define a channel area in the active layer, a method of fabricating a stable, high mobility active layer comprising the steps of:
 forming the active layer with a plurality of films including a metal oxide semiconductor film and a metal oxide passivation film, the metal oxide passivation film having a major upper surface and including aluminum, and the metal oxide passivation film being positioned between the metal oxide semiconductor film and the etch-stop layer;   modifying a portion of the upper major surface of the metal oxide passivation film including treating the aluminum with a base material to remove the aluminum from the portion of the upper major surface of the metal oxide passivation film to increase the conductivity, the base material being other than gas-phase ammonia; and   removing a portion of the metal oxide passivation film on opposite sides of the etch-stop layer to expose a surface of the metal oxide semiconductor film and positioning the metal source/drain contacts on the exposed surface of the metal oxide semiconductor film.   
     
     
         36 . A method as claimed in  claim 35  wherein the step of forming the active layer with a plurality of films further includes a step of forming a contact layer of metal between the metal oxide passivation film and the etch-stop layer and the metal source/drain contacts, and a step of forming the etch-stop layer of oxygen donating material. 
     
     
         37 . A method as claimed in  claim 35  wherein the step of forming the active layer with a plurality of films further includes a step of forming a thin film of oxygen bonding metal adjacent the gate dielectric layer. 
     
     
         38 . A method as claimed in  claim 37  wherein the step of forming the thin film of oxygen bonding metal includes forming the film of oxygen bonding metal less than approximately 5 molecular layers thick. 
     
     
         39 . A method as claimed in  claim 35  wherein the step of forming the thin film of oxygen bonding metal includes forming the film of oxygen bonding metal by sputter deposition. 
     
     
         40 . A method as claimed in  claim 35  wherein the step of forming the thin film of oxygen bonding metal includes a coating process with a solution comprising organo-metallic molecules comprising the corresponding metal, and followed with a reduction process in a chamber with inert gas or in a vacuum. 
     
     
         41 . The method as claimed in  claim 35  wherein the thin film of oxygen bonding metal comprise Al, Si, B, Ta, Mg, Ti or their combination. 
     
     
         42 . The method as claimed in  claim 35  wherein the thin film of the oxygen bonding metal has a metal-oxygen bonding strength large than 100 cal/mol. 
     
     
         43 . The method as claimed in  claim 35  wherein the step of forming the metal oxide semiconductor film and the metal oxide passivation film in the active layer is by sputter deposition. 
     
     
         44 . A metal oxide thin film transistor as claimed in  claim 1  wherein the substrate is glass, plastic, or stainless steel sheet. 
     
     
         45 . A metal oxide thin film transistor as claimed in  claim 1  wherein the gate dielectric layer comprises SiO2, SiN, Al2O3, HfO, or their combination in multiple layer stack. 
     
     
         46 . A metal oxide thin film transistor as claimed in  claim 1  wherein the etch-stop layer includes oxygen. 
     
     
         47 . A metal oxide thin film transistor as claimed in  claim 1  wherein the etch-stop layer comprises organic material. 
     
     
         48 . A metal oxide thin film transistor as claimed in claim  5 D wherein the organic material in the etch-stop layer is photo-patternable. 
     
     
         49 . The metal oxide thin film transistor as claimed in  claim 10  wherein the thin film of oxygen bonded metal comprise Al, Si, B, Ta, Mg, Ti or their combination. 
     
     
         50 . The metal oxide thin film transistor as claimed in  claim 10  wherein the thin film of oxygen bonded metal has metal-oxygen bonding strength large than 100 cal/mol.