Modern integrated chips (ICs) use multilayered arrangement of copper interconnects, which plays important role in electric signal and power distribution to various active components on ICs. Each copper wire is isolated from other by insulating material. Carbon doped silicon oxide (CDO) is a promising low dielectric constant (k) hybrid insulating material used in modern ultra-large scale integration (ULSI) devices [1]. CDO is a nano porous and hybrid material composed of extensive cross linking of Si, C, and O elements. In IC fabrication oxygen plasma treatments are inevitable and causes irreversible modification of functional groups attached to silicon to hydrophilic Si-OH groups [2]. Surface exposed hydrophilic Si-OH groups becomes active moisture absorbing sites and cause undesired increase in k value (water k = ~80) and leakage currents thereby compromising the quality of dielectric material. Several approaches have been investigated to minimize the CDO damage, such as H2, He, NH3 plasma pretreatments, dissolving the damaged CDO layer by hydrofluoric acid (HF) and functionalizing the hydrophilic Si-OH functional groups to short alkyl chain siloxy functional groups. However, many of the discussed methods have their own limitations like causing undesired film thickness loss, damaging the chemical structure of CDO and not effective in preventing further moisture attack. Here we present a strategy for selective functionalization of surface exposed hydrophilic Si-OH functional groups to hydrogen terminated silicon (Si-H) without affecting the rest of chemical structure of CDO. Hydrogen terminated silicon readily reverst to Si-OH termination in air; , so it is further derivatized to highly hydrophobic Si-R (R= Octadecyl) groups. Long alkyl chain derivativatized surface becomes highly hydrophobic and effectively prevents moisture attack thereby helps in maintaining the low-k value. FTIR, X-ray Photoelectron Spectroscopy (XPS) and water contact angle measurement techniques are employed for studying the reaction progress on CDO wafer. References: 1. Grill, A.; Neumayer, D. A., Structure of low dielectric constant to extreme low dielectric constant SiCOH films: FTIR characterization. Journal of Applied Physics 2003, 94 (10), 6697-6707. 2. Wang, Y. H.; Kumar, R.; Zhou, X.; Pan, J. S.; Chai, J. W., Effect of oxygen plasma treatment on low dielectric constant carbon-doped silicon oxide thin films. Thin Solid Films 2005, 473 (1), 132-136.

Conversion of surface silanol to silicon hydride on solid silicon oxide surfaces

251st National Meeting (2016)

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