Thin film formation method, thin film, and glass plate having thin film attached thereto
The present invention relates to a method for forming a TiO 2 thin film on a substrate by using an atmospheric pressure CVD method, in which a raw material gas contains titanium tetraisopropoxide (TTIP) and a chloride of a metal M vaporizable in a temperature range of 100 to 400° C. and the amount of the chloride of the metal M is from 0.01 to 0.18 as a concentration ratio to the titanium tetraisopropoxide (TTIP) (chloride of metal M (mol %)/TTIP (mol %)).
1. A TiO 2 thin film obtained by an atmospheric pressure CVD method comprising:
supplying a raw material gas to a substrate; and
reacting a Ti raw material contained in the raw material gas with oxygen to form the TiO 2 thin film on the substrate,
wherein:
the raw material gas comprises, as the Ti raw material, titanium tetraisopropoxide (TTIP) and a chloride of a metal M vaporizable in a temperature range of 100 to 400° C.;
an amount of the chloride of the metal M is from 0.01 to 0.18 as a concentration ratio to the titanium tetraisopropoxide (TTIP) (chloride of metal M (mol %)/TTIP (mol %));
the TiO 2 thin film has a Cl content of 0.5×10 18 (atoms/cm 3 ) or more and 10×10 18 (atoms/cm 3 ) or less;
when a film thickness of the TiO 2 thin film is taken as L (nm), a content ratio of an oxide of a metal M in terms of film thickness is 0.002 L or more and 0.035 L or less, which is represented by a ratio of a content of the oxide of the metal M in terms of film thickness (virtual film thickness when replacement is performed with a thin film having a content of the oxide of the metal M of 100%) to the film thickness L of the TiO 2 thin film; and
the TiO 2 thin film has a film thickness distribution in a width direction defined by the following expression of 4% or less per 1 m of the width:
Film thickness distribution (%)={((Maximum film thickness among measuring points)/(Average film thickness among measuring points)×100)−((Minimum film thickness among measuring points)/(Average film thickness among measuring points)×100)}/Measured width (m).
2. The TiO 2 thin film according to claim 1 , wherein, when a film thickness of the TiO 2 thin film is taken as L (nm), a content ratio of an oxide of a metal M in terms of film thickness is 0.009 L or more and 0.035 L or less, which is represented by a ratio of a content of the oxide of the metal M in terms of film thickness (virtual film thickness when replacement is performed with a thin film having a content of the oxide of the metal M of 100%) to the film thickness L of the TiO 2 thin film.
3. The TiO 2 thin film according to claim 1 , which has a film thickness distribution in a width direction defined by the following expression of 2% or less per 1 m of the width:
Film thickness distribution (%)={((Maximum film thickness among measuring points)/(Average film thickness among measuring points)×100)−((Minimum film thickness among measuring points)/(Average film thickness among measuring points)×100)}/Measured width (m).
4. The TiO 2 thin film according to claim 1 , which has a ratio of a surface roughness Ra (nm) to a film thickness t (nm) (Ra/t) of 0.01 or more and 0.05 or less.