Comparison Between E-beam and Ultraviolet Curing to Perform Porous a-SiOC : H

Porous ultralow-k films are required by the microelectronics industry as interlayer dielectrics for 65 nm technologies and below. These porous insulating films can be deposited by plasma-enhanced chemical vapor deposition using a porogen approach. It consists of the codeposition of a matrix precursor and a sacrificial organic porogen, and then on a post-treatment to remove the organic porogen phase and create porosity in the film. In this work, an e-beam assisted thermal curing was compared to an ultraviolet-assisted thermal curing. Basic film properties such as k, film shrinkage, porosity, pore size, and pore size distribution were evaluated. NMR and Fourier transform infrared analyses were used to study the chemical modifications induced by the post-treatment. These analyses show that the post-treatment impact depends on the radiation used. Both treatments lead to a removal of terminal nonbridging bonds such as Si-OH, Si-H, and Si-CH 3 and can contribute to a subsequent formation of Si-O-Si crosslinks. Both treatments remove methyls from Si-CH 3, but the e-beam induces a Si-H bond increase while the UV bulb used decreases the Si-H contribution. The cross-linking improvement induces an increase of Young's modulus, the elastic properties being mainly correlated to the Si-O-Si volumic bond concentration in the film.