The dielectric characteristics of low-k interlayer dielectric materials was fabricated by plasma enhanced chemical vapor deposition (PECVD). BTMSM precursor was evaporated and introduced with the flow rates from 16 sccm to 25 sccm by 1sccm step in the constant flow rate of 60 sccm $O_2$ in process chamber. Manufactured samples are analyzed components by measuring FT/IR absorption lines. Decomposition each Microscopic structures through two-dimensional correlation analysis about mechanisms for the formation of SiOCH in $SiOCH_3$, Si-O-Si and Si-$CH_3$ bonding group and analyzed correlation between the micro-structure of each group. It is a tendency that seems to be growing of Si-O-Ci(C) bonding group and narrowing of Si-O-$CH_3$ bonding group relative to the increasing flow-rate BTMSM. The order of changing sensitivity about changes of flow-rate in Si-O-Si(C) bonding group is cross link mode$(1050cm^{-1})$ $ ightarrow$ open link mode$(1100cm^{-1}) ightarrow$ cage link mode $(1140cm^{-1})$.