Atomic Layer Deposition of SiC_xN_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 Si 2 Cl 6 and a CH 3 NH 2 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 Si 2 Cl 6 and NH 3 plasma-based process, we show that on the SiC x N y growth surface, Si 2 Cl 6 reacts primarily with surface −NH 2 species that were created after the CH 3 NH 2 plasma cycle. During the subsequent CH 3 NH 2 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 CH 3 NH 2 plasma half cycle was not self-limiting and led to continuous carbon nitride growth.