A porous ultra low-κ dielectric (pULK) and a dense SiCOH dielectric were investigated before and after a plasma treatment with argon in terms of the change in the bonding types, the relative permittivity and the water uptake. Fourier transform infrared (FTIR) spectroscopy revealed a change in the bonding types of the dielectrics in general and a significant increase in the hydroxyl band especially. The high hydroxyl amount leads to an increase in the relative permittivity of these dielectrics by up to 6.25% for SiCOH and up to 12.5% for the pULK material. Furthermore, if water diffuses into the dielectric films from the environment, the moisture uptake is up to 2.7 times higher in saturation at 80% relative humidity in comparison to the untreated samples. Due to the plasma damaged upper layer of the materials, the diffusion process of water into the bulk dielectrics is significant reduced. Overall, it has been found that the pULK material is more vulnerable to the used plasma treatment in comparison to the dense SiCOH film.

Low-k materials developed for ULSI interconnects should have sufficient resistance to processing plasma. CO 2 plasma is being considered as a promising candidate for low damage photoresist ash and as a surface activation chemistry for self-assembled monolayers and atomic layer deposition on low-k materials. This article explores the interaction of two organosilicate (OSG) based low-k materials with different k-values (OSG2.4 and OSG2.2) with CO 2 plasma in both CCP and ICP-remote plasma chambers. Time dependent exposure of the materials to CO 2 plasma revealed quick and effective sealing of OSG2.4 surface whereas it takes longer time for OSG2.2. The sealing reduces further plasma damage and leads to accumulation of CO 2 in the pores of both materials. The same behavior occurs in ICP-remote plasma but without a complete sealing of the surface. This suggests the important role of ion bombardment. Damage to low-k by conventional O 2 plasma was studied alongside and it was found that for t < 60 s, O 2 plasma exerts more damage on OSG2.2 than CO 2 . This trend is reversed at t > 60 s. Furthermore, lesser time exposure to CO 2 plasma was investigated with respect to source power at constant pressure and it was discovered that damage although small, increases with varying source power. The performance enhancement of electronic circuits was majorly centered on reducing the transistor sizes, increasing transistor speed and density. However, in advanced technology nodes the performance of the resulting integrated circuits (IC) is greatly hindered by the resistance -capacitance (RC) delay experienced during the signal propagation within the interconnects.1 In order to solve this problem, the traditional Al was replaced by Cu, which has lower resistivity and SiO 2 with k = 4.0 was replaced by low dielectric constants (low-k) materials. Organosilicate glasses (OSG) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and/or by Spin-on Glass technology (SOG) are presently the most popular low-k materials.Photoresist strip using O 2 based plasma is a conventionally used processing technique but this has been found to be severely damaging to porous low-k materials. The modifications to the porous low-k materials lead to increased k-values from densification and hydrophilization.2-5 The CO 2 -based plasma has been reported to be less damaging with respect to the O 2 counterpart. Fuller et al. proposed the use of CO 2 based RIE plasma for photoresist stripping. Ming-Shu Kuo et al. and Hualiang Shi extensively studied the surface modification of ultralow-k materials by CO 2 plasma and the results are published in their PhD dissertations 7,8 and in several papers. 9-13 They reported that i) CO 2 and O 2 plasma damage to ultralow-k films are comparable ii) there is lower atomic oxygen density in CO 2 discharge than O 2 discharge because of higher activation energy (11.5 eV) required to liberate atomic oxygen from CO 2 than from O 2 molecules (6 eV) -this is why there is supposedly a reduction in damage by CO 2 discharge wi...

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