The structure and hybridization of N(SiH3)3 is
N atom in trisilylamine N(SiH3)3 is sp2 hybridised. It has a lone pair in 2p orbital which is transferred to the empty d-orbital of Si atom resulting dπ-pπ bonding. It has planar structure.
If its lone pair was not involved with Si atom then it results in pyramidal geometry as seen in trimethylamine N(CH3)3.
Structure of trisilylamine N(SiH3)3 (Planar structure)
Trimethylamine N(CH3)3 (pyramidal structure)