The Effect of Plasma Damage on the Material Composition and Electrical Performance of Different Generations of SiOC(H) L
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0914-F04-03
The Effect of Plasma Damage on the Material Composition and Electrical Performance of Different Generations of SiOC(H) Low k Films Aurelie Humbert, Didem Ernur Badaroglu, and Romano J.O.M Hoofman Philips Research Europe, Kapeldreef 75, LEUVEN, B-3001, Belgium ABSTRACT The degradation of SiOC(H) low-k films upon plasma treatments has been investigated. Different generations of SiOC(H) low-k dielectrics (k=3.0 and k=2.6) were used. The low-k materials have been exposed to N2O, NH3, O2, H2, He, Ar and N2 based plasmas, representing the most commonly-used plasmas during interconnect integration. Some of the experiment points were also carried out on a highly porous SiOC material (k=2.3), for additional comparison. For all plasma-treated samples, an increase in k-value and decrease in breakdown voltage was observed. These observations could be attributed to chemical degradation, in particular to carbon depletion and OH-bond formation. The latter leads to moisture adsorption, which was confirmed by contact angle measurements and FTIR spectra. The N2O plasma treatment was found to be the most aggressive for all low-k dielectrics studied. It drastically increases the k-value and the leakage current and results in complete carbon removal on the top-surface. This effect is most pronounced on the most porous material. On the other hand, an in-situ helium plasma shortly after low-k deposition enhances the resistance to chemical degradation upon exposure to other plasmas, even for the most aggressive ones. For the argon and reactive pre-clean plasmas, only small compositional changes were observed. In conclusion, it can be said that not only the plasma treatments have to be tuned in accordance with the low k integration requirements, but also attention has to be paid to limit moisture absorption during integration. INTRODUCTION As device dimensions shrink according to the ITRS specifications [1], the use of low-k dielectrics in the Back End Of Line (BEOL) is necessary to compensate for the increments in interline capacitances. However, such materials are difficult to integrate into a copper back-end process. In addition to their mechanical fragility, they are extremely susceptible to chemical and physical degradation occurring during integration. Etch and strip plasmas [2,3], pre-clean processes [4] and CVD plasma depositions [5] are all potential threats for low-k integrity. In this paper, the effects of several plasma treatments on the low-k film properties and electrical characteristics are studied using different generations of low-k dielectric films. EXPERIMENTAL DETAILS Two different sets with 150nm PECVD SiOC blanket films (with either a k=3.0 or k=2.6) were deposited. On the first set, the wafers were treated with an in-situ helium post-treatment in the deposition chamber before exposure to any other plasma, while the other set did not receive this ‘sealing’ He-plasma treatment. In addition, some experiments were also carried out on a highly porous SiOC material (spin-on film with k=2.3 and 33% of porosity),
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