PURPOSE: To obtain an electric circuit substrate, which has an excellent capacity and has a sufficient life,at a high yield by processing the surface of a substrate with a fluoric acid etching liquid having a specific composition.
CONSTITUTION: The surface of a substrate 1 is processed with the etching liquid consisting of 1 nitric acid, ≤4 fluoric acid, and 50W200 diluent by capacity, and an electric circuit, for example, a thin film transistor (TFT) array is formed on the substrate 1. This etching liquid has high workability and reproducibility, and the surface of the glass substrate 1 is not too roughened, and the uniformity is not damaged, and fine rugged parts of 20W80 are formed on all of the surface. Electrodes or other elements are formed on this substrate 1 or 12. An exposed part of the surface of the substrate 1 can be exposed to this etching after picture element electrods or the like are formed on the substrate 1, and the TFT is formed. Thus, the electric circuit has a strong coupling force to the surface of the substrate 1, and the yield in device production is improved, and the life of the device is made longer sufficiently.
KANEKO TETSUYA
KITAHARA NOBUKO
SUGATA MASAO
