Composite oxide semiconductor and method for manufacturing the same

Abstract

The field-effect mobility and reliability of a transistor including an oxide semiconductor film are improved. A semiconductor layer of a transistor is formed using a composite oxide semiconductor in which a first region and a second region are mixed. The first region includes a plurality of first clusters containing one or more of indium, zinc, and oxygen as a main component. The second region includes a plurality of second clusters containing one or more of indium, an element M (M represents Al, Ga, Y, or Sn), zinc, and oxygen. The first region includes a portion in which the plurality of first clusters are connected to each other. The second region includes a portion in which the plurality of second clusters are connected to each other.

What is claimed is: 
     
         1 . A method for manufacturing a composite oxide semiconductor, comprising:
 a first step of placing a substrate in a deposition chamber;   a second step of introducing one or both of an argon gas and an oxygen gas into the deposition chamber;   a third step of applying voltage to a target comprising indium, an element M, zinc, and oxygen; and   a fourth step of depositing the composite oxide semiconductor from the target onto the substrate,   wherein the fourth step comprises:
 a first step in which the element M and the zinc are preferentially sputtered from the target; and 
 a second step in which the indium has a cluster-like shape and then the indium with the cluster-like shape is sputtered from the target, and 
   wherein the M represents Al, Ga, Y, or Sn.   
     
     
         2 . The method for manufacturing the composite oxide semiconductor, according to  claim 1 ,
 wherein the substrate is not heated intentionally.   
     
     
         3 . A method for manufacturing a composite oxide semiconductor, comprising:
 a first step of placing a substrate in a deposition chamber;   a second step of introducing, into the deposition chamber, a deposition gas comprising an argon gas and not comprising an oxygen gas;   a third step of applying voltage to a target comprising indium, an element M, zinc, and oxygen; and   a fourth step of depositing the composite oxide semiconductor from the target onto the substrate,   wherein the fourth step comprises:
 a first step in which the element M and the zinc are preferentially sputtered from the target; and 
 a second step in which the indium has a cluster-like shape and then the indium with the cluster-like shape is sputtered from the target, and 
   wherein the M represents Al, Ga, Y, or Sn.   
     
     
         4 . The method for manufacturing the composite oxide semiconductor, according to  claim 3 ,
 wherein the substrate is not heated intentionally.