Stable high mobility motft and fabrication at low temperature

Abstract

A method of fabricating a stable high mobility amorphous MOTFT includes a step of providing a substrate with a gate formed thereon and a gate dielectric layer positioned over the gate. A carrier transport structure is deposited by sputtering on the gate dielectric layer. The carrier transport structure includes a layer of amorphous high mobility metal oxide adjacent the gate dielectric and a relatively inert protective layer of material deposited on the layer of amorphous high mobility metal oxide both deposited without oxygen and in situ. The layer of amorphous metal oxide has a mobility above 40 cm 2 /Vs and a carrier concentration in a range of approximately 10 18 cm −3 to approximately 5×10 19 cm −3 . Source/drain contacts are positioned on the protective layer and in electrical contact therewith.

1 - 27 . (canceled) 
     
     
         28 . A stable high mobility amorphous MOTFT comprising:
 a substrate with a gate formed thereon and a gate dielectric layer positioned over the gate;   a carrier transport structure on the gate dielectric layer, the carrier transport structure including a layer of amorphous high mobility metal oxide adjacent the gate dielectric and a protective layer of relatively inert material compared to the layer of metal oxide,   source/drain contacts on the protective layer; and   wherein the layer of amorphous high mobility metal oxide and the protective layer are deposited without oxygen and in situ, the protective layer being relatively inert compared to the layer of amorphous high mobility metal oxide, the carrier transport layer and the protective layer are further treated by forming an oxygen-rich zone at the upper surface of the protective layer at a temperature below 160° C., and driving oxygen into the protective layer from the oxygen-rich zone at an elevated temperature.   
     
     
         29 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the layer of amorphous high mobility metal oxide includes a carrier concentration in a range of approximately 10 18  cm −3  to approximately 5×10 19  cm −3 . 
     
     
         30 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the layer of amorphous high mobility metal oxide includes one of indium-tin-oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium oxide (CdO), zinc oxide (ZnO), indium-zinc-oxide (IZO), or a composite film comprising combinations thereof. 
     
     
         31 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the layer of amorphous high mobility metal oxide has a thickness in a range of equal to or less than approximately 5 nm and preferably approximately 2 nm. 
     
     
         32 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the protective layer includes a metal oxide that is more inert than the amorphous high mobility metal oxide layer. 
     
     
         33 . The stable high mobility amorphous MOTFT as claimed in  claim 32  wherein the more inert metal oxide includes one of M-Zn—O, M-In—O, or combinations thereof, where M includes at least one of Al, Ga, Ta, Ti, Si, Ge, Sn, Mo, W, Cu, Mg, V, or Zr. 
     
     
         34 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the protective layer includes a layer with a thickness in a range of 20 nm-50 nm. 
     
     
         35 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the MOTFT is included in a thin film electric circuit. 
     
     
         36 . The stable high mobility amorphous MOTFT as claimed in  claim 35  wherein the thin film electric circuit is included in an electronic device including one of a display array device, an imager sensor array device, a pressure sensor array device, a touch sensor array device, a chemical sensor array device, or a biosensor array device. 
     
     
         37 . The stable high mobility amorphous MOTFT as claimed in  claim 36  wherein the thin film electric circuit is included in a pixel driver or a readout circuit inside the array or a column/row driver circuit in a peripheral area of the array. 
     
     
         38 . A stable high mobility amorphous MOTFT comprising:
 a substrate with a gate formed thereon and a gate dielectric layer positioned over the gate;   a carrier transport structure sputtered on the gate dielectric layer, the carrier transport structure including a layer of amorphous high mobility metal oxide adjacent the gate dielectric with a thickness in a range of equal to or less than approximately 5 nm and preferably approximately 2 nm, a protective layer of relatively inert material deposited on the layer of amorphous high mobility metal oxide with a thickness in a range of 20 nm-50 nm, and the layer of amorphous metal oxide having a mobility above 40 cm 2 /Vs and a carrier concentration in a range of approximately 10 18  cm −3  to approximately 5×10 19  cm −3 ; and   source/drain contacts positioned on and in electrical contact with the protective layer.   
     
     
         39 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the carrier mobility is 15 cm 2 /Vsec or above. 
     
     
         40 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the carrier mobility is 40 cm 2 /Vsec or above. 
     
     
         41 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the substrate includes one of glass, plastic film, and stainless steel film each in one of rigid, conformable, or flexible form. 
     
     
         42 . The stable high mobility amorphous MOTFT as claimed in  claim 28  wherein the gate dielectric layer includes a layer of SiO 2 , SiN, Al 2 O 3 , AlN, Ta 2 O 5 , TiO 2 , ZrO, HfO, SrO, or their combinations in blend or multiple layer form. 
     
     
         43 . The stable high mobility amorphous MOTFT as claimed in  claim 28  further comprises a passivation/etch-stop layer over the protection layer and between the source and drain electrodes. 
     
     
         44 . The stable high mobility amorphous MOTFT as claimed in  claim 43  wherein the passivation/etch-stop layer includes a layer of Al 2 O 3 , Ta 2 O 5 , TiO 2 , SiN, SiO 2 , photo-patternable organic dielectric or their combinations in blend or multiple layer form. 
     
     
         45 . A method of fabricating a stable high mobility amorphous MOTFT comprising the steps of:
 providing a substrate with a gate formed thereon and a gate dielectric layer positioned over the gate;   depositing by sputtering a carrier transport structure on the gate dielectric layer without intentional substrate heating or with intentional cooling, the carrier transport structure including a layer of amorphous high mobility metal oxide adjacent the gate dielectric and a protective layer of material deposited on the layer of amorphous high mobility metal oxide both deposited without oxygen and in situ, the protective layer being relatively inert compared to the layer of amorphous high mobility metal oxide;   forming an oxygen-rich zone at the upper surface of the protective layer at a temperature below 160° C.; and   driving oxygen into the protective layer from the oxygen-rich zone at an elevated temperature.   
     
     
         46 . The method as claimed in  claim 45  further including the steps of:
 defining a channel area overlying the gate in the layer of amorphous high mobility metal oxide; 
 forming an etch-stop layer overlying the channel area subsequent to the driving oxygen step; 
 defining source/drain contact areas on opposed sides of the channel area; 
 performing a cleaning and/or treatment and/or etching step on the surface of the source/drain contact areas; and 
 depositing and patterning source/drain contacts on the protective layer in the source/drain contact areas. 
 
     
     
         47 . The method as claimed in  claim 45  further including, prior to the step of forming an oxygen-rich zone, the steps of:
 defining a channel area overlying the gate in the layer of amorphous high mobility metal oxide; 
 defining source/drain contact areas on opposed sides of the channel area; 
 depositing a blanket metal layer on the protective layer; and 
 patterning the blanket metal layer to form source/drain electrodes in the source/drain areas and to open an area between the source/drain electrodes overlying the channel area. 
 
     
     
         48 . The method as claimed in  claim 45  wherein the step of depositing a layer of amorphous high mobility metal oxide includes depositing a layer of amorphous metal oxide with a mobility above 15 cm 2 /Vs. 
     
     
         49 . The method as claimed in  claim 45  wherein the step of depositing a layer of amorphous high mobility metal oxide includes depositing a layer of amorphous metal oxide with a mobility above 40 cm 2 /Vs. 
     
     
         50 . The method as claimed in  claim 45  wherein the step of depositing a layer of amorphous high mobility metal oxide includes depositing a layer of amorphous metal oxide with a carrier concentration in a range of approximately 10 18  cm −3  to approximately 5×10 19  cm −3 . 
     
     
         51 . The method as claimed in  claim 45  wherein the step of depositing the layer of amorphous high mobility metal oxide includes depositing one of indium-tin-oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium oxide (CdO), zinc oxide (ZnO) indium-zinc-oxide (IZO), or zinc oxide (ZnO), or a composite film including more than one of the above metal-oxides. 
     
     
         52 . The method as claimed in  claim 45  wherein the step of depositing the layer of amorphous high mobility metal oxide includes depositing a layer with a thickness in a range of equal to or less than approximately 5 nm. 
     
     
         53 . The method as claimed in  claim 45  wherein the step of depositing the protective layer includes depositing a layer with a thickness in a range of 20 nm-50 nm. 
     
     
         54 . The method as claimed in  claim 45  wherein the step of depositing the protective layer includes depositing a layer including metal oxides that are more inert than the amorphous high mobility metal oxide layer. 
     
     
         55 . The method as claimed in  claim 54  wherein the step of depositing the more inert metal oxide includes depositing a layer of one of M-Zn—O, M-In—O, or their combination, where M includes at least one of Al, Ga, Ta, Ti, Si, Ge, Sn, Mo, W, Cu, V, or Zr. 
     
     
         56 . The method as claimed in  claim 45  wherein the step of forming the oxygen-rich zone includes using oxygen plasma, N2O plasma, a UV-ozone process, surface treatment with hydrogen-peroxide or a dichromate solution, or a combination process thereof. 
     
     
         57 . The method as claimed in  claim 56  wherein the step of forming the oxygen-rich zone is performed at a pressure below 100 mtorr. 
     
     
         58 . The method as claimed in  claim 45  wherein the step of forming the oxygen-rich zone is by coating a thin surfactant layer. 
     
     
         59 . The method as claimed in  claim 45  wherein the step of driving oxygen from the oxygen source into the protective layer includes using an elevated temperature equal to or greater than 160° C. 
     
     
         60 . The method as claimed in  claim 45  wherein the step of providing the substrate includes providing a substrate including one of glass, plastic film, and stainless steel film each in one of rigid, conformable, or flexible form. 
     
     
         61 . The method as claimed in  claim 45  wherein the step of providing the gate dielectric layer includes providing a layer including SiO2, SiN, Al2O3, AlN, Ta 2 O 5 , TiO 2 , ZrO, HfO, SrO, or their combinations in blend or multiple layer form. 
     
     
         62 . The method as claimed in  claim 61  wherein the step of providing the gate dielectric layer includes forming the gate dielectric layer by anodization, by heating under oxygen-rich ambient, or combinations thereof in sequence from the corresponding metal. 
     
     
         63 . The method as claimed in  claim 46  wherein the step of forming an etch-stop layer Al 2 O 3 , Ta 2 O 5 , TiO 2 , SiN, SiO 2 , photo-patternable organic dielectric or their combinations in blend or multiple layer form.