Properties of N-rich Silicon Nitride Film Deposited by Plasma-Enhanced Atomic Layer Deposition

ACS Appl. Mater. Interfaces

Lucero

et al. 2018

In this work, a novel chlorodisilane precursor, pentachlorodisilane (PCDS, HSiCl), was investigated for the growth of silicon nitride (SiN ) via hollow cathode plasma-enhanced atomic layer deposition (PEALD). A well-defined self-limiting growth behavior was successfully demonstrated over the growth temperature range of 270-360 °C. At identical process conditions, PCDS not only demonstrated approximately>20% higher growth per cycle than that of a commercially available chlorodisilane precursor, hexachlorodisilane (SiCl), but also delivered a better or at least comparable film quality determined by characterizing the refractive index, wet etch rate, and density of the films. The composition of the SiN films grown at 360 °C using PCDS, as determined by X-ray photoelectron spectroscopy, showed low O content (∼2 at. %) and Cl content (<1 at. %; below the detection limit). Fourier transform infrared spectroscopy spectra suggested that N-H bonds were the dominant hydrogen-containing bonds in the SiN films without a significant amount of Si-H bonds originating from the precursor molecules. The possible surface reaction pathways of the PEALD SiN using PCDS on the surface terminated with amine groups (-NH and -NH-) are proposed. The PEALD SiN films grown using PCDS also exhibited a leakage current density as low as 1-2 nA/cm at 2 MV/cm and a breakdown electric field as high as ∼12 MV/cm.

Section: ■ Results and Discussionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Hollow Cathode Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using Pentachlorodisilane

Meng

ACS Appl. Mater. Interfaces

Lucero

et al. 2018

“…However, WER investigations thus far have been mainly limited to PECVD SiN x . − In such studies of the WER of PECVD SiN x , WER is understood to be primarily affected by the hydrogen bonding concentration in the SiN x film. ,,− Additionally, the bulk film density affects the wet chemical resistance property of PECVD SiN x films , as the Si–N bond density will increase proportionally to the bulk film density of SiN x . Recently, Provine et al stressed the significance of the bulk film density effect on WER in the PEALD system, while Jhang et al and Ovanesyan et al , underlined the hydrogen concentration effect on WER. However, further studies on WER of PEALD SiN x are necessary to understand the role of either the gas phase reaction or surface reaction that defines the fundamental difference in growth mechanism between PECVD and PEALD techniques, respectively.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Physical Properties of Plasma Enhanced Atomic Layer Deposited Silicon Nitride as Etch Stopper

Meng

ACS Appl. Mater. Interfaces

et al. 2018

Correlations between physical properties linking film quality with wet etch rate (WER), one of the leading figures of merit, in plasma-enhanced atomic layer deposition (PEALD) grown silicon nitride (SiN x ) films remain largely unresearched. Achieving a low WER of a SiN x film is especially significant in its use as an etch stopper for technology beyond 7 nm node semiconductor processing. Herein, we explore the correlation between the hydrogen concentration, hydrogen bonding states, bulk film density, residual impurity concentration, and the WERs of PEALD SiN x using Fourier transform infrared spectrometry, X-ray reflectivity, and spectroscopic ellipsometry, etc. PEALD SiN x films for this study were deposited using hexachlorodisilane and hollow cathode plasma source under a range of process temperatures (270–360 °C) and plasma gas compositions (N2/NH3 or Ar/NH3) to understand the influence of hydrogen concentration, hydrogen bonding states, bulk film density, and residual impurity concentration on the WER. Varying hydrogen concentration and differences in the hydrogen bonding states resulted in different bulk film densities and, accordingly, a variation in WER. We observe a linear relationship between hydrogen bonding concentration and WER as well as a reciprocal relationship between bulk film density and WER. Analogous to the PECVD SiN x processes, a reduction in hydrogen bonding concentration arises from either (1) thermal activation or (2) plasma excited species. However, unlike the case with silane (SiH4)-based PECVD SiN x , PEALD SiN x WERs are affected by residual impurities of Si precursors (i.e., chlorine impurity). Thus, possible wet etching mechanisms in HF in which the WER is affected by hydrogen bonding states or residual impurities are proposed. The shifts of amine basicity in SiN x due to different hydrogen bonding states and the changes in Si electrophilicity due to Cl impurity content are suggested as the main mechanisms that influence WER in the PEALD processes.

“…Silicon nitride (Si 3 N 4 ) thin films are important for applications in microelectronics such as dielectric layers in complementary metal oxide semiconductor devices, − gate spacers, ,− and diffusion barriers. − In particular, deposition of conformal thin films at low temperatures (<300 °C) is necessary for nanopatterned, three-dimensional substrates developed to satisfy scaling requirements. , Atomic layer deposition (ALD) has emerged as one of the best methods to achieve Si 3 N 4 deposition with adequate thickness control, conformality for highly patterned substrates, and chemical specificity. − A number of precursors have been developed for the growth of Si 3 N 4 for both thermal and plasma-enhanced processes. ,,− Among them, aminosilanes are particularly attractive because, unlike chlorosilanes, they generate noncorrosive halogenated products. ,, However, thermal processes with chlorosilanes or aminosilanes and either ammonia (NH 3 ) or hydrazine (N 2 H 4 ) require temperatures above 300 °C, which is not acceptable for several applications. ,,,,− Therefore, efforts have turned to plasma-enhanced processes that allow for low-temperature growth. ,,,,, For example, Knoops et al developed a plasma-enhanced atomic layer deposition (PEALD) process using bis( t -butylamino)silane (BTBAS) as a precursor and nitrogen plasma as a coreactant and demonstrated a large temperature window that allowed tunability of the film composition/properties by varying the growth conditions. , Although PEALD silicon nitride growth from aminosilane precursors shows great promise, the underlying reaction mechanisms and relationships between growth conditions and film composition must be understood to develop reliable industrial processes. , Some theoretical attempts have been made to underst...…”

Section: Introductionmentioning

confidence: 99%

In Situ Infrared Absorption Study of Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride

et al. 2018

Despite the success of plasma-enhanced atomic layer deposition (PEALD) in depositing quality silicon nitride films, a fundamental understanding of the growth mechanism has been difficult to obtain because of lack of in situ characterization to probe the surface reactions noninvasively and the complexity of reactions induced/enhanced by the plasma. These challenges have hindered the direct observation of intermediate species formed during the reactions. We address this challenge by examining the interaction of Ar plasma using atomically flat, monohydride-terminated Si(111) as a well-defined model surface and focusing on the initial PEALD with aminosilanes. In situ infrared and X-ray photoelectron spectroscopy reveals that an Ar plasma induces desorption of H atoms from H-Si(111) surfaces, leaving Si dangling bonds, and that the reaction of di-sec-butylaminosilane (DSBAS) with Ar plasma-treated surfaces requires the presence of both active sites (Si dangling bonds) and Si-H; there is no reaction on fully H-terminated or activated surfaces. By contrast, high-quality hydrofluoric acid-etched SiN surfaces readily react with DSBAS, resulting in the formation of O-SiH. However, the presence of back-bonded oxygen in O-SiH inhibits H desorption by Ar or N plasma, presumably because of stabilization of H against ion-induced desorption. Consequently, there is no reaction of adsorbed aminosilanes even after extensive Ar or N plasma treatments; a thermal process is necessary to partially remove H, thereby promoting the formation of active sites. These observations are consistent with a mechanism requiring the presence of both undercoordinated nitrogen and/or dangling bonds and unreacted surface hydrogen. Because active sites are involved, the PEALD process is found to be sensitive to the duration of the plasma exposure treatment and the purge time, during which passivation of these sites can occur.