Low-Temperature Conformal Atomic Layer Deposition of SiN_x Films Using Si₂Cl₆ and NH₃ Plasma

Abstract

A plasma-enhanced atomic layer deposition (ALD) process was developed for the growth of SiNx thin films using Si2Cl6 and NH3 plasma. At substrate temperatures ≤400 °C, we show that this ALD process leads to films with >95% conformality over high aspect ratio nanostructures with a growth per cycle of ∼1.2 Å. The film growth mechanism was studied using in situ attenuated total reflection Fourier transform infrared spectroscopy. Our data show that on the SiNx growth surface, Si2Cl6 reacts with surface -NH2 groups to form surface -NH species, which are incorporated into the growing film. In the subsequent half cycle, radicals generated in the NH3 plasma abstract surface Cl atoms, and restore an NHx (x = 1,2)-terminated surface. Surface Si-N-Si bonds are also primarily formed during the NH3 plasma half-cycle. The infrared data and Rutherford backscattering combined with hydrogen forward scattering shows that the films contain ∼23% H atoms primarily incorporated as -NH groups.

Review—Silicon Nitride and Silicon Nitride-Rich Thin Film Technologies: Trends in Deposition Techniques and Related Applications

“…88 Other applications include host matrix for ruthenium nanocrystals as seed/barrier layer for copper metallization in IC structures; 97,98 and hydrofluoric acid etch stop layer and electrically insulating spacer in MEMS and medical devices. 80,81 One common attribute in all these applications is the inherent ability of ALD to provide stringent atomic level control and excellent conformality 55 for SiN x coatings in challenging geometries where CVD begins to show its deficiencies and shortcomings.…”

“…PA-ALD SiN x is the subject of relatively few reports, 86,88 and the work focused on the reaction of halosilanes and N-bearing reactants, primarily: (a) Si halides containing Br and/or I (See section Overview of silicon nitride source chemistries) and a N-containing reactant, such as NH 3 , in the temperature range of 350-600…”

“…• C. 88 The apparent lack of interest in PA-ALD SiN x could be attributed, at least in part, to concerns about the potential adverse effects of plasma generation directly above the substrate, including the potential inclusion of contaminants in the films. Furthermore, compositional analysis 88 showed that the PA-ALD films were N-rich (N/Si ratio ∼1.71) with significant H incorporation (e.g., as high as 23% at 400…”

“…Furthermore, compositional analysis 88 showed that the PA-ALD films were N-rich (N/Si ratio ∼1.71) with significant H incorporation (e.g., as high as 23% at 400…”

Atomic Layer Deposition of Silicon Nitride Thin Films: A Review of Recent Progress, Challenges, and Outlooks

“…Eventually, after one cycle reaction, the dominant components on the new surface will be nitrogen-containing reactive sites (e.g., under-coordinated N atoms, –NH x , dangling bonds). As recently elaborated in the paper authored by Ande et al, the relation between the two half-cycle reactions of SiN x ALD should be reciprocal: the surface after the former reaction can facilitate the following reaction, otherwise, the film growth will not be sustainable [49]. …”