| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系所 === 103 === This thesis work examined the properties of silicon carbonitride (SiCxNy) films for application as the low-k etch-stop layer (ESL) in copper interconnects. Due to the downscaling of feature size, the lowering of effective dielectric constant (keff) is needed to reduce RC delay. However, the ESL has a significant impact on the keff because of higher dielectric constant. As a result, development of novel ESL with low dielectric constant and good properties is very important. To investigate the effect of different chemical structures in the single precursors on the properties of low-k SiCxNy thin films, two different single-precursors with high carbon content: 1,3-divinyl-1,1,3,3-tetramethyldisilazane (DVTMDS) and bis(dimethylamino)diethyl- silane (BDMADES) were chosen to prepare SiCxNy films by using radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at 25-400 ℃. In this study, emphasize had been laid on the chemical structures, atomic compositions, mechanical properties, etch selectivity, dielectric constant and leakage current of the SiCxNy films.
Upon plasma polymerization, vinyl groups of DVTMDS could gain the formation of thermally stable Si-(CH2)n-Si methylene bridge crosslinking, leading to higher content of hydrocarbon (CHx) could be preserved than BDMADES during plasma process and even at high substrate temperature. This resulted in a lower dielectric constant and higher thermal stability. On the other hand, the N-CH3 and Si-CH2CH3 in BDMADES exhibited the unstable fragments in the plasma polymerization process, causing large loss of carbon. Furthermore, we found that with higher deposition pressures the N-H bonds that exhibited high polarity decreased, leading to a lower dielectric constant and leakage current density.
Among these SiCxNy films, low-k SiCxNy films with k value of 3.44, leakage current density of 1.2×10-9 A/cm2 at 1 MV/cm (breakdown strength >3 MV/cm), mechanical strength of around 32 GPa and good etch selectivity (deposited at 400℃, etch selectivity=4.0) were prepared at TS of 350 ℃, 1 Torr and power density of 0.15 W/cm3 using DVTMDS as single-precursor, and it could be the candidate materials of low-k ESL meeting the requirements of device integration in the next generation .
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