Investigation of Structure Modification of Underlying SiCOH Low-kDielectrics with Subsequent Hardmask Deposition Process Conditions

Abstract

Device miniaturization requires the use of hardmasks in the IC manufacturing process, and employing an amorphous carbon layer (ACL) hardmask over a low-kdielectric is a well-known technology. An elevated temperature causes a dielectric constant shift owing to structural changes and methyl group desorption in the deposited SiCOH films. In this study, the structural change of the SiCOH film, which varies depending on the ACL deposition condition, was analyzed. Structural changes in SiCOH after ACL deposition were analyzed using Fourier transform infrared spectroscopy (FTIR). From 900 to 1300 cm−1wavenumber, changes of methyl group and structure of the SiCOH film were identified. As a result, we found that the structure and methyl content of the low-kfilm changes during the hardmask deposition due to the heat and plasma. In particular, the SiCOH film is richer in methyl group at higher temperatures. A high-density hardmask was deposited at higher temperatures. It was deduced that a high-density ACL hardmask was deposited on SiCOH because of the higher temperature, and the ACL hardmask on low-kacts as a capping layer.