Method for producing amorphous oxide thin film and thin film transistor

A method for producing an amorphous oxide thin film, the method comprising:

• a pre-treatment process of selectively changing a binding state of an organic component, at a temperature lower than a pyrolysis temperature of the organic component, in a first oxide precursor film containing the organic component and In, to obtain a second oxide precursor film in which, when an infrared wave number range of from 1380 cm−1 to 1520 cm−1 in an infrared absorption spectrum obtained by performing a measurement by Fourier transform infrared spectroscopy is divided into an infrared wave number range of from 1380 cm−1 to 1450 cm−1 and an infrared wave number range of from more than 1450 cm−1 to 1520 cm−1, a peak positioned within the infrared wave number range of from 1380 cm−1 to 1450 cm−1 exhibits the maximum value in the infrared absorption spectrum within an infrared wave number range of from 1350 cm−1 to 1750 cm1;
• and
• a post-treatment process of removing the organic component remaining in the second oxide precursor film, to transform the second oxide precursor film into an amorphous oxide thin film containing In,
• wherein the pre-treatment process is a photo treatment process, wherein the first oxide precursor film comprises an inorganic component including In and at least one selected from the group consisting of Ga, Zn, and Sn, and wherein a composition of the inorganic component is In:Ga:Zn =2-x:x:1 (in which, x represents a number of from 0.8 to 1.05), and
• further comprising, before the pre-treatment process, a formation process of forming the first oxide precursor film by a liquid phase method using a solution containing a metal alkoxide or an organic acid salt.