Enhancement of adhesion strength of Cu layer with low dielectric constant SiC:H liners in Cu interconnects

One of the primary candidates for the liner/etch stop layer in damascene process is silicon nitride (Si₃N₄). However, silicon nitride has a high dielectric constant of 7.0. To reduce the effective dielectric constant in Copper (Cu) damascene structure, dielectric SiC:H (prepared by plasma enhanced chemical vapor deposition (PECVD) using trimethylsilane source) as the Cu diffusion barrier was studied. The dielectric constant of SiC:H used is 4.2. A systematic study was made on the properties of liner material and electro-chemically plated (ECP) Cu to enhance the adhesion strength in Cu/low-dielectric constant (k) multilevel interconnects. Though the effects of as Si₃N₄ the liner have been much studied in the past, less is known about the relation between adhesion strength of ECP Cu layer and physical vapor deposited (PVD) Cu seeds, with seed thickness below 1000 Å. The annealing of Cu seed layer was carried out at 200 °C in N₂ ambient for 30 min was carried out to study the impact on adhesion strength and the microstructure evolution on the adhesion between ECP Cu and its barrier layer. In the study, our claim that SiC:H barrier/etch stop layer is essential for replacing conventional Si₃N₄ layer in enhancing adhesion strength and interfacial bonding between Cu/dielectric interconnects.     

Properties of low-k SiCOH films prepared by plasma-enhanced chemical vapor deposition using trimethylsilane

The properties of low-k SiCOH film deposited by plasma-enhanced chemical vapor deposition using trimethylsilane are reported here. The deposition process was performed at different temperatures from 200 to 400 °C. The influence of deposition temperature on the films were characterized using Fourier transform infrared spectroscopy (FTIR) to understand its impact on the studied properties. The films were annealed at ∼450 °C in an inert ambient after deposition in all the cases. The deposition rate decreases with increase in deposition temperature. The refractive index of the films increases as a function of deposition temperature. From FTIR spectra, OH-related bonds were not detected in films even when deposited at 200 °C. The Si-CH₃ bonds were detected in all the films and decreased monotonically from 200 to 400 °C. All deposition conditions studied resulted in films with dielectric constant less than 3, the lowest being ∼2.7 when deposited at 200 °C. All films exhibited good thermal stability.     

Plasma interface engineered coating systems for magnesium alloys

In this study, a dc low-temperature plasma technique, including plasma treatment and plasma polymerization, was used to create interface engineered coating systems with a structure of Mg/plasma interlayer/cathodic electrocoating (E-coat) for machined AZ31B magnesium (Mg) alloy panels. The plasma interlayer deposited from trimethylsilane (TMS) precursor had a nano-scale thickness of ∼65 nm and well-controlled surface properties through subsequent plasma treatments in order to achieve different level of interfacial adhesion between the E-coat and the Mg substrates. The surface wettability of the plasma interlayer was monitored by water surface contact angle measurement. The interface adhesion of the coating system was evaluated using N-methylpyrrolidinone (NMP) paint removal test and ASTM tape test conducted under dry and wet conditions. Electrochemical impedance spectroscopy (EIS) was employed to investigate the effects of plasma interlayer properties including surface wettability and adhesion enhancement on corrosion protection properties of the coating systems. It was found that a more wettable interface enhanced the electrolyte penetration through the coating and thus reduced the corrosion resistance of the coating system. On the other hands, the improved interface adhesion had little effects on EIS results mainly due to the high chemical reactivity of the Mg alloy substrates.     

Open-air laser-induced chemical vapor deposition of silicon carbide coatings

This study demonstrates the open-air deposition of amorphous hydrogenated silicon carbide (a-SiC:H) by laser-induced chemical vapor deposition (LCVD) using an enclosureless (open-air) reactor system. Films are deposited on fused quartz substrates using the precursor gas trimethylsilane (TrMS). Based on Auger electron spectroscopy (AES), Fourier transform infrared absorption spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), the film's chemical composition and microstructure is determined to be composed of a form of silicon carbide (SiC:H) with organic moiety. To understand the temperature-dependence of film growth during deposition, varying deposition conditions were employed to correlate the SiC film deposition rate and deposition temperature.