Polysilazane, siliceous film-forming composition comprising the same, and method for producing siliceous film using the same

A method for producing a siliceous film, comprising applying a siliceous film-forming composition comprising a polysilazane comprising N—Si bonds, wherein the ratio (NA3/NA2) of the number of N atoms having 3 N—Si bonds (NA3) to the number of N atoms having 2 N—Si bonds (NA2) is 1.8 to 6.0,

• where
• the peak existing in 3500 to 3250 cm−1 corresponding to N—H bonds and the peak existing in 1065 to 695 cm−1 corresponding to Si—N bonds of the infrared absorption spectrum of the polysilazane are defined as absorbance corresponding to N—H bonds and Si—N bonds, respectively,
• the amount of N—H bonds and Si—N bonds/cm3 (N) existing in a thin film having film thickness of d (cm) is determined by the following formula:
• N=A∫a(ω))/ω·dω
• (wherein
• A is a proportionality constant, AN—H:
• 2.6×1020 (cm−2) as N—H bonds and ASi—N:
• 7.7×1018(cm−2) as Si—N bonds are used,
• a(ω) is an absorption coefficient, w is a wave number, a(ω)=1/d×absorbance×ln10, and
• NA2 is defined as amount of N—H bonds, and NA3 is defined as [(amount of Si—N bonds)−(amount of N—H bonds)×2)]/3), and
• a solvent above a substrate, and
• heating it under an ozone atmosphere.