PRE-Ru METALLIZATION CLEANING USING ECR PLASMA

초록

A diffusion barrier TiN is commonly used in between Ru and SiO2 to inhibit diffusion of Ru into Si substrates through other layers including the SiO2 layer. Unless the TiN substrate surface is cleaned prior to Ru deposition by MOCVD in Ru Metallization[1-3], Ru nucleation density will be very low, so that a continuous Ru film will be difficult to form. Therefore, precleaning of the TiN surface is essential prior to Ru deposition. In the present work, effects of hydrogen, oxygen or argon plasma pretreatment on the Ru nucleation in MOCVD are investigated. TiN films 200 nm thick were deposited on N-type (100)Si wafers by reactive DC magnetron sputtering using a Ti target in N2. The TiN surfaces were precleaned using the ECR plasma treatment with hydrogen, oxygen, and argon. The standard process parameters for the plasma cleaning were the microwave power of 300 W, the H2 flow rate of 15 sccm and the deposition temperature of 298 K. The exposure time was varied in the ranges of 1-15 min. After plasma cleaning, Ru films were deposited on the TiN films by MOCVD using Bis(ethyl-p-cyclopentadienyl) ruthenium [Ru(EtCp)2] as a precursor. A four-point probe was used to measure the resistivity of Ru/TiN film. Scanning electron microscopy (SEM) was used to observe the Ru nucleation density. Auger electron spectrometry (AES) depth profiling was performed to investigate change of the composition of the TiN surface region. To see the dependence of Ru nucleation enhancement upon the source gas material used in the ECR plasma treatment, three different plasma source gases were compared. Ru nuclei are found in the samples using three different plasma source gases. While Ru nucleation on the TiN film is declined by giving the oxygen ECR plasma treatment, it is substantially enhanced by giving hydrogen and argon ECR plasma treatment to the TiN film surface prior to the deposition of Ru film on the TiN film film using an MOCVD technique.