Sealing ultralow κ porous dielectrics with thin boron carbonitride films

Abstract

Porous ultralow κ dielectric film pores were sealed by 1–5nm films of boron carbonitride, itself a dielectric. The BC0.9N0.07 films were deposited by chemical vapor deposition at 335°C on etched and ashed blanket films and patterned films of porous methyl silsesquioxane (PMSQ). The penetration of Ta through the boron carbonitride film and into the porous low κ substrate following exposure to TaF5 at 230°C, or TaSix growth from TaF5 and Si2H6 at 230°C, was used to test pore sealing. Tantalum profiles were evaluated using x-ray photoelectron spectroscopy depth profiling, back side secondary ion mass spectroscopy, and energy dispersive x-ray spectroscopy. A 3.9nm boron carbonitride film sealed PMSQ, which has an average pore diameter of 1.9nm before etching. The diffuse nature of the BC0.9N0.07-PMSQ interface in electron energy loss profile maps suggests that some of the BC0.9N0.07 penetrates into the PMSQ until the pore openings are pinched off as the sealing film deposits.