Sputtering target, oxide semiconductor thin film, and method for producing oxide semiconductor thin film

Abstract

A sputtering target including an oxide that, includes an indium element (In), a tin element (Sn), a zinc element (Zn) and an aluminum element (Al), and including a homologous structure compound represented by InAlO 3 ZnO) m (m is 0.1 to 10), wherein the atomic ratio of the indium element, the tin element, the zinc element and the aluminum element satisfies specific requirements.

1 . A sputtering target comprising an oxide that comprises an indium element (In), a tin element (Sn), a zinc element (Zn) and an aluminum element (Al), and comprising a homologous structure compound represented by InAlO 3 (ZnO) m  (m is 0.1 to 10), wherein the atomic ratio of the indium element, the tin element, the zinc element and the aluminum element satisfies the following formulas (1) to (4):
   0.10≦In/(In+Sn+An+Al)≦0.60   (1)
     0.01≦Sn/(In+Sn+Zn+Al)≦0.30   (2)
     0.10≦Zn/(In+Sn+Zn+Al)≦0.65   (3)
     0.01≦Al/(In+Sn+Zn+Al)≦0.30   (4)
   
       wherein in the formulas, In, Sn, Zn and Al are respectively the substance amount of the indium element, the tin element, the zinc element and the aluminum element in the sputtering target. 
     
     
         2 . The sputtering target according to  claim 1 , wherein the homologous structure compound represented by InAlO 3 (ZnO) m  (m is 0.1 to 10) is one or more selected from a homologous structure compound represented by InAlZn 2 O 5  and a homologous structure compound represented by InAlZnO 4 . 
     
     
         3 . The sputtering target according to  claim 1  that comprises a spinel structure compound represented by Zn 2 SnO 4 . 
     
     
         4 . The sputtering target according to  claim 1  that does not comprise a bixbyite structure compound represented by In 2 O 3 . 
     
     
         5 . The sputtering target according to  claim 1  that has a relative density of 98% or more. 
     
     
         6 . The sputtering target according to  claim 1  that has a bulk specific resistance of 5 mΩcm or less. 
     
     
         7 . A method for producing a sputtering target, comprising:
 a step of elevating a temperature of a formed body of an oxide that comprises an indium element, a tin element, a zinc element and an aluminum element from 800° C. to a sintering temperature at a temperature-elevating rate of 0.1 to 2° C./m, and   retaining the formed body at the sintering temperature for 10 to 50 hours,   wherein the sintering temperature is 1200° C. to 1650° C.   
     
     
         8 . An oxide semiconductor thin film obtained by a sputtering method using the sputtering target according to  claim 1 . 
     
     
         9 . A method for producing an oxide semiconductor thin film by a sputtering method using the sputtering target according to  claim 1  in an atmosphere of a mixed gas that comprises: one or more selected from water molecules oxygen molecules and nitrous oxide molecules; and rare gas atoms. 
     
     
         10 . The method for producing an oxide semiconductor thin film according to  claim 9 , wherein the mixed gas is a mixed gas that at least comprises rare gas atoms and water molecules. 
     
     
         11 . The method for producing an oxide semiconductor thin film according to  claim 10 , wherein the ratio of the water molecules contained in the mixed gas is 0.1% to 25% in terms of a partial pressure ratio. 
     
     
         12 . The method for producing the oxide semiconductor thin film according to  claim 9  comprising:
 transporting substrates in sequence to positions opposing to 3 or more sputtering targets arranged in parallel with a prescribed interval in a vacuum chamber; 
 applying a negative potential and a positive potential alternately from an AC power source to each of the targets; and 
 causing plasma to be generated on the target by applying an output from at least one AC power source between two or more targets divergently connected to this AC power source while switching the target to which a potential is applied, thereby forming a film on a substrate surface. 
 
     
     
         13 . The method for producing the oxide semiconductor thin film according to  claim 12 , wherein the AC power density of the AC power source is 3 W/cm 2  or more and 20 W/cm 2  or less. 
     
     
         14 . The method for producing the oxide semiconductor thin film according to  claim 12 , wherein the frequency of the AC power source is 10 kHz to 1 MHz. 
     
     
         15 . A thin film transistor comprising, as a channel layer, the oxide semiconductor thin film formed by the method for producing an oxide semiconductor thin film according to  claim 9 . 
     
     
         16 . The thin film transistor according to  claim 15  that has a field effect mobility of 15 cm 2 /Vs or more. 
     
     
         17 . A display comprising the thin film transistor according to  claim 15 .