Oxide for semiconductor layer of thin-film transistor, semiconductor layer of thin-film transistor having said oxide, and thin-film transistor

Abstract

The oxide of the present invention for thin-film transistors is an In—Zn—Sn-based oxide containing In, Zn, and Sn, wherein when the respective contents (atomic %) of metal elements contained in the In—Zn—Sn-based oxide are expressed by [Zn], [Sn], and [In], the In—Zn—Sn-based oxide fulfills the following expressions (2) and (4) when [In]/([In]+[Sn])≦0.5; or the following expressions (1), (3), and (4) when [In]/([In]+[Sn])≧0.5. [In]/([In]+[Zn]+[Sn])≦0.3 - - - (1), [In]/([In]+[Zn]+[Sn])≦1.4×{[Zn]/([Zn]+[Sn])}−0.5 - - - (2), [Zn]/([In]+[Zn]+[Sn])≦0.83 - - - (3), and 0.1≦[In]/([In]+[Zn]+[Sn]) - - - (4). According to the present invention, oxide thin films for thin-film transistors can be obtained, which provide TFTs with excellent switching characteristics, and which have high sputtering rate in the sputtering and properly controlled etching rate in the wet etching.

1 . An In—Zn—Sn-based oxide comprising In, Zn, and Sn, wherein when respective contents, in atomic %, of metal elements Zn, Sn, and In in the In—Zn—Sn-based oxide are expressed by [Zn], [Sn], and [In], the In—Zn—Sn-based oxide satisfies:
 (a) expressions (2) and (4) when [In]/([In]+[Sn])≦0.5:
   [In]/([In]+[Zn]+[Sn])≦1.4×{[Zn]/([Zn]+[Sn])}−0.5  (2)
 
   and 
   0.1≦[In]/([In]+[Zn]+[Sn])  (4)
 
 
 
       or
 (b) expressions (1), (3), and (4) when [In]/([In]+[Sn])>0.5:
   [In]/([In]+[Zn]+[Sn])≦0.3  (1)
 
   [Zn]/([In]+[Zn]+[Sn])≦0.83  (3)
 
   and 
   0.1≦[In]/([In]+[Zn]+[Sn])  (4).
 
 
 
     
     
         2 . The In—Zn—Sn-based oxide of  claim 1 , which is an oxide formed by a sputtering method wherein an oxygen partial pressure is 18% or lower. 
     
     
         3 . The In—Zn—Sn-based oxide of  claim 1 , wherein the In—Zn—Sn-based oxide has a thickness of 30 to 200 nm. 
     
     
         4 . A semiconductor layer of a thin-film transistor comprising the In—Zn—Sn-based oxide of  claim 1 , wherein the semiconductor layer has an electronic carrier concentration in a range of 10 15  to 10 18  cm −3 . 
     
     
         5 . The semiconductor layer of a thin-film transistor of  claim 4 , wherein the semiconductor layer is obtained by a heating treatment of the In—Zn—Sn-based oxide at 250° C. to 350° C. for 15 to 120 minutes. 
     
     
         6 . A thin-film transistor comprising the In—Zn—Sn-based oxide of  claim 1  as a semiconductor layer of the thin-film transistor. 
     
     
         7 . A display device comprising the thin-film transistor of  claim 6 . 
     
     
         8 . An In—Zn—Sn-based oxide sputtering target comprising In, Zn, and Sn, wherein when respective contents, in atomic %, of metal elements Zn, Sn, and In in the In—Zn—Sn-based oxide sputtering target are expressed by [Zn], [Sn], and [In], the In—Zn—Sn-based oxide sputtering target satisfies:
 (a) expressions (2) and (4) when [In]/([In]+[Sn])≦0.5:
   [In]/([In]+[Zn]+[Sn])≦1.4×{[Zn]/([Zn]+[Sn])}−0.5  (2)
 
   and 
   0.1≦[In]/([In]+[Zn]+[Sn])  (4)
 
 
 
       or
 (b) expressions (1), (3), and (4) when [In]/([In]+[Sn])>0.5:
   [In]/([In]+[Zn]+[Sn])≦0.3  (1)
 
   [Zn]/([In]+[Zn]+[Sn])≦0.83  (3)
 
   and 
   0.1≦[In]/([In]+[Zn]+[Sn])  (4).
 
 
 
     
     
         9 . The In—Zn—Sn-based oxide of  claim 1 , satisfying (a):
   [In]/([In]+[Sn])≦0.5,
 
   [In]/([In]+[Zn]+[Sn])≦1.4×{[Zn]/([Zn]+[Sn])}−0.5  (2)
 
   and 
   0.1≦[In]/([In]+[Zn]+[Sn])  (4).
 
 
     
     
         10 . The In—Zn—Sn-based oxide of  claim 1 , satisfying (b):
   [In]/([In]+[Sn])>0.5, 
   [In]/([In]+[Zn]+[Sn])≦0.3  (1)
 
   [Zn]/([In]+[Zn]+[Sn])≦0.83  (3)
 
   and 
   0.1≦[In]/([In]+[Zn]+[Sn])  (4).
 
 
     
     
         11 . The In—Zn—Sn-based oxide of  claim 9 , wherein the In—Zn—Sn-based oxide has a thickness of 30 to 200 nm. 
     
     
         12 . The In—Zn—Sn-based oxide of  claim 10 , wherein the In—Zn—Sn-based oxide has a thickness of 30 to 200 nm. 
     
     
         13 . A semiconductor layer of a thin-film transistor comprising the In—Zn—Sn-based oxide of  claim 9 , wherein the semiconductor layer has an electronic carrier concentration in a range of 10 15  to 10 18  cm −3 . 
     
     
         14 . A semiconductor layer of a thin-film transistor comprising the In—Zn—Sn-based oxide of  claim 10 , wherein the semiconductor layer has an electronic carrier concentration in a range of 10 15  to 10 18  cm −3 . 
     
     
         15 . The In—Zn—Sn-based oxide of  claim 1 , which is suitable for use as a semiconductor layer of a thin film transistor.