Applications of Raman spectroscopy in copper chemical mechanical planarization: In situ detection of tantalum layer to dielectric layer transition

In metal chemical mechanical planarization, in situ detection of barrier to dielectric layer transition is typically done using reflectivity measurements. Introduction of carbon containing low-dielectric constant (k) materials, commonly known as carbon doped oxides (CDOs), as dielectric layers has opened up the possibility of using spectroscopic techniques for detecting such transition. The vibrational frequencies of the bonds between C, H, O, and Si in these low-fc materials may be readily detected by spectroscopic techniques such as Raman and infrared spectroscopies. In this work, the use of Raman spectroscopy in detecting the transition from Ta layer to a CDO layer has been explored. An abrasion cell integrated with a Raman spectrometer was used to make the measurements. The sensitivity of the Raman technique is compared with that of the conventional reflectivity technique.