Atomic Layer Deposition of SiC x N y Using Si2Cl6 and CH3NH2 Plasma

We developed a novel process for the atomic layer deposition (ALD) of SiC x N y films using a Si2Cl6 and a CH3NH2 plasma. Under self-limiting growth conditions, this ALD process led to SiC x N y films with up to 9 atomic percent carbon with a conformality >95% in 5:1 aspect ratio nanostructures. The surface reactions during ALD, and in particular the carbon incorporation mechanism, were studied using in situ attenuated total reflection Fourier transform infrared spectroscopy. Similar to the Si2Cl6 and NH3 plasma-based process, we show that on the SiC x N y growth surface, Si2Cl6 reacts primarily with surface −NH2 species that were created after the CH3NH2 plasma cycle. During the subsequent CH3NH2 half cycle, the surface chlorine was liberated, creating −NH x (x = 1 or 2) groups, while carbon was incorporated primarily as −NCN– species. In situ ellipsometry showed that the growth per cycle and the refractive index were ∼1 Å and ∼1.85, respectively. Elemental depth profiling with secondary ion mass spectrometry showed that, as the plasma power was increased from 50 to 100 W, the carbon atomic fraction increased from ∼4 to ∼9%. At higher plasma powers, the CH3NH2 plasma half cycle was not self-limiting and led to continuous carbon nitride growth.