Challenges in atomic layer deposition of carbon-containing silicon-based dielectrics

Abstract

The authors have designed experiments to test three different approaches for the incorporation of carbon atoms into amorphous SiNx or SiO2 films grown using atomic layer deposition (ALD). In each approach, the surface reactions of the precursors were monitored in situ using attenuated total reflection Fourier transform infrared spectroscopy. In the first approach, for depositing carbon-containing SiNx films using ALD, carbon was introduced into the process through a silicon precursor, SiCl2(CH3)2, followed by NH3 plasma exposure. While our infrared data show that SiCl2(CH3)2 reacts with an –NHx (x = 1, 2) terminated surface created after NH3 plasma exposure, –CH3 groups are eliminated in the precursor adsorption step leading to no significant carbon in the films. In the second approach, the authors hypothesized a three-step ALD process, which would involve Si-, C-, and N-containing precursors, and tested the reactivity of two carbon-containing precursors, CH3I and Al(CH3)3, with H- and Cl-terminated silicon surfaces, respectively. The authors show that both precursors readily react with the silicon surfaces, but neither one provides the appropriate surface termination. CH3I reacts with surface –SiHx (x = 1, 2, 3) to create surface –SiIx (x = 1, 2, 3) species with CH3 as the leaving groups. While Al(CH3)3 reacts with the Cl-terminated Si surface to form a surface –SiCH3 group, residual aluminum remains on the surface as –Al(CH3)x (x = 1, 2) groups that are not completely removed as volatile Al(CH3)xCl3−x (x = 1, 2). Finally, in the third approach for ALD of carbon-containing SiO2 films, the authors used Si2Cl6 with CO and CO/O2 plasmas. A pure CO plasma led to amorphous carbon growth, and a CO plasma diluted with of O2 led to no detectable carbon incorporation in the SiO2 film.

Gas Phase Organic Functionalization of SiO2 with Propanoyl Chloride

“…The in situ ATR–FTIR spectroscopy setup has been described in detail in previous publications. , Briefly, in this setup, SiO 2 was plasma deposited onto a trapezoidal 50 × 20 × 1 mm ZnSe internal reflection crystals (IRC) with the short face beveled at 45°. − The IRC was clamped onto a temperature-controlled resistive heater. An infrared beam from a commercial FTIR spectrometer (Nicolet 6700) was directed through a KBr window and focused onto the short face of the ZnSe IRC.…”

Selective Gas-Phase Functionalization of SiO2 and SiNx Surfaces with Hydrocarbons

“…Thus, there must be another reaction pathway where the −NH 2 species are converted to −NH species. We have shown previously that due to the higher absorption cross-section for the stretching vibrations of the surface −NH groups compared to surface −NH 2 groups, this conversion leads to an increase in the absorbance in the NH x stretching region, even though there is a decrease in the total number of N-H bonds. ,,,, …”

“…We have shown previously that due to the higher absorption cross-section for the stretching vibrations of the surface −NH groups compared to surface −NH 2 groups, this conversion leads to an increase in the absorbance in the NH x stretching region, even though there is a decrease in the total number of N-H bonds. 14,43,59,88,89 It is well known that in an acidic solution, aldehydes and ketones react with a primary amine to form an imine and H 2 O as a byproduct (see Figure 5). This complex reaction has been well studied, and the various intermediates are known.…”

Atomic Layer Deposition of SiCxNy Using Si2Cl6 and CH3NH2 Plasma

“…Numerous thermal and plasma-assisted ALD processes for SiN x have been reported in the literature that are primarily based on chlorosilanes, ,, aminosilanes, − silylamines, − and silanes , as the Si precursors. Recently, we proposed a framework for the development of ALD processes for C-containing Si-based dielectrics that was based on the modification of known ALD processes for SiN x and SiO 2 . In particular, we tested two approaches for C incorporation into SiN x films: (a) ALD with Si precursors that contain Si–C bonds such as SiCl 2 (CH 3 ) 2 with a NH 3 plasma, which is a modification of known SiN x ALD processes using SiCl 2 H 2 or Si 2 Cl 6 and NH 3 plasma, , and (b) three-step ALD processes where we inserted an intermediate cycle of a reactive C precursor such as CH 3 I or Al­(CH 3 ) 3 in between the Si precursor and the NH 3 or N 2 plasma cycles of known ALD processes for SiN x growth.…”

“…The former approach of using precursors with Si–C bonds was not successful, as the −CH 3 groups in the precursor were lost either during chemisorption or during the NH 3 plasma cycle. On the other hand, the latter three-step approach was not successful as −CH 3 was the leaving group upon chemisorption of CH 3 I onto surface SiH x ( x = 1, 2, or 3) groups, and Al­(CH 3 ) 3 led to residual Al . Although the presence of adventitious C has been reported using aminosilane precursors and N 2 plasma, , the ALD of SiC x N y with tunable C incorporation remains elusive.…”