Nondispersive Ultraviolet Visible Gas Analyzer for Monitoring Molybdenum Chloride and Oxychloride Precursors During Vapor Deposition Processes.

Nondispersive ultraviolet visible gas analyzer designs were evaluated for monitoring molybdenum-containing chloride and oxychloride precursor delivery during microelectronics vapor deposition processes. The performances of three analyzer designs, which differed only in the bandpass filter employed for wavelength selection, were compared for measuring the partial pressure of molybdenum pentachloride, molybdenum oxytetrachloride (MoOCl), and molybdenum dioxydichloride (MoOCl). The analyzer's optical response with a 369 nm center wavelength filter for molybdenum pentachloride was determined by measuring the molybdenum pentachloride absorbance as a function of vapor molar density.

Ultraviolet-Visible Absorption Spectroscopy of MoCl, MoOCl, and MoOCl Vapors.

This article reports quantitative absorption spectra for MoCl, MoOCl, and MoOCl in the vapor phase from 45,500 to 15,500 cm (645 to 220 nm). Spectra are obtained in an ultrahigh purity stainless steel vacuum system by rapidly sampling a range of analyte partial pressures. The short measurement times and the differential absorbance method employed here minimize effects from uncontrolled transients such as window deposits.

GaSb band-structure models for electron density determinations from Raman measurements.

We investigate the use of Raman spectroscopy to measure carrier concentrations in GaSb epilayers to aid in the development of this technique for the nondestructive characterization of transport properties in doped semiconductors. The carrier concentration is quantified by modeling the measured coupled optical phonon-free carrier plasmon mode spectra. We employ the Lindhard-Mermin optical susceptibility model with contributions from carriers in the two lowest GaSb conduction-band minima, the and minima.

Extracting electron densities in -type GaAs from Raman spectra: Comparisons with Hall measurements.

We demonstrate quantitatively how values of electron densities in GaAs extracted from Raman spectra of two samples depend on models used to describe electric susceptibility and band structure. We, therefore, developed a theory that is valid for any temperature, doping level, and energy ratio proportional to =( + ) (where is the magnitude of wave vector, is Raman frequency, and is plasmon damping). We use a full Mermin-Lindhard description of Raman line shape and compare -type GaAs spectra obtained from epilayers with our simulated spectra.

Nondispersive Infrared Gas Analyzer for Partial Pressure Measurements of a Tantalum Alkylamide During Vapor Deposition Processes.

A nondispersive infrared gas analyzer was demonstrated for investigating metal alkylamide precursor delivery for microelectronics vapor deposition processes. The nondispersive infrared analyzer was designed to simultaneously measure the partial pressure of pentakis(dimethylamido) tantalum, a metal precursor employed in high volume manufacturing vapor deposition processes to deposit tantalum nitride, and dimethylamine, the primary decomposition product of pentakis(dimethylamido) tantalum at typical delivery conditions for these applications. This sensor was based on direct absorption of pentakis(dimethylamido) tantalum and dimethylamine in the fingerprint spectral region.

Apparatus for Characterizing Gas-Phase Chemical Precursor Delivery for Thin Film Deposition Processes.

Thin film vapor deposition processes, e.g., chemical vapor deposition, are widely used in high-volume manufacturing of electronic and optoelectronic devices.

Characterization of bubbler performance for low-volatility liquid precursor delivery.

The performance of a bubbler to deliver the low-volatility, liquid cobalt precurso - -(Bu-acetylene) dicobalthexacarbonyl (CCTBA) for reduced-pressure chemical vapor deposition and atomic layer deposition processes was characterized. A relatively large process window was investigated by varying carrier gas flow rate, system pressure, and bubbler temperature. For this range of conditions, the CCTBA partial pressure was measured using a custom-designed non-dispersive infrared gas analyzer, and the CCTBA flow rates were derived from these partial pressure measurements.

Experiment-based modelling of a vapor draw ampoule used for low-volatility precursors.

Delivery of low-volatility precursors is a continuing challenge for chemical vapor deposition and atomic layer deposition processes used for microelectronics manufacturing. To aid in addressing this problem, we have recently developed an inline measurement capable of monitoring precursor delivery. Motivated by a desire to better understand the origins of what is now observable, this study uses computational fluid dynamics and a relatively simple model to simulate the delivery of pentakis(dimethylamido)tantalum (PDMAT) from a commercial vapor draw ampoule.

Rapid Wafer-Scale Growth of Polycrystalline 2H-MoS by Pulsed Metalorganic Chemical Vapor Deposition.

High volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultra-thin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metalorganic chemical vapor deposition (MOCVD) route for MoS film growth in a research-grade single-wafer reactor.

MoS thin films from a (N Bu)(NMe)Mo and 1-propanethiol atomic layer deposition process.

Potential commercial applications for transition metal dichalcogenide (TMD) semiconductors such as MoS rely on unique material properties that are only accessible at monolayer to few-layer thickness regimes. Therefore, production methods that lend themselves to scalable and controllable formation of TMD films on surfaces are desirable for high volume manufacturing of devices based on these materials. We have developed a new thermal atomic layer deposition (ALD) process using bis(-butylimido)-bis(dimethylamido)molybdenum and 1-propanethiol to produce MoS-containing amorphous films.

infrared spectroscopy during LaO ALD using La( PrCp) and HO.

Infrared spectra of surface species have been obtained during atomic layer deposition using tris(isopropylcyclopentadienyl)lanthanum, La(PrCp), and water as precursors at 160 °C and 350 °C. Gas-phase spectra of La(PrCp)are obtained for comparison. At low temperature, ligand exchange is seen to occur, and carbonate formation is found.

Nondispersive Infrared Gas Analyzer for Vapor Density Measurements of a Carbonyl-Containing Organometallic Cobalt Precursor.

A nondispersive infrared (NDIR) gas analyzer was demonstrated for measuring the vapor-phase density of the carbonyl-containing organometallic cobalt precurso μ-η-(Bu-acetylene) dicobalthexacarbonyl (CCTBA). This sensor was based on direct absorption by CCTBA vapor in the C≡O stretching spectral region and utilized a stable, broadband IR filament source, an optical chopper to modulate the source, a bandpass filter for wavelength isolation, and an InSb detector. The optical system was calibrated by selecting a calibration factor to convert CCTBA absorbance to a partial pressure that, when used to calculate CCTBA flow rate and CCTBA mass removed from the ampoule, resulted in an optically determined mass that was nominally equal to a gravimetrically-determined mass.

Measurements of metal alkylamide density during atomic layer deposition using a mid-infrared light-emitting diode (LED) source.

A nondispersive infrared (NDIR) gas analyzer that utilizes a mid-infrared light emitting diode (LED) source was demonstrated for monitoring the metal alkylamide compound tetrakis(dimethylamido) titanium (TDMAT), Ti[N(CH3)2]4. This NDIR gas analyzer was based on direct absorption measurement of TDMAT vapor in the C-H stretching spectral region, a spectral region accessed using a LED with a nominal emission center wavelength of 3.65 μm.

Time-resolved surface infrared spectroscopy during atomic layer deposition.

This work presents a novel method for obtaining surface infrared spectra with sub-second time resolution during atomic layer deposition (ALD). Using a rapid-scan Fourier transform infrared (FT-IR) spectrometer, we obtain a series of synchronized interferograms (120 ms) during multiple ALD cycles to observe the dynamics of an average ALD cycle. We use a buried metal layer (BML) substrate to enhance absorption by the surface species.

Quantum cascade laser-based measurement of metal alkylamide density during atomic layer deposition.

An in situ gas-phase diagnostic for the metal alkylamide compound tetrakis(ethylmethylamido) hafnium (TEMAH), Hf[N(C(2)H(5))(CH(3))](4), was demonstrated. This diagnostic is based on direct absorption measurement of TEMAH vapor using an external cavity quantum cascade laser emitting at 979 cm(-1), coinciding with the most intense TEMAH absorption in the mid-infrared spectral region, and employing 50 kHz amplitude modulation with synchronous detection. Measurements were performed in a single-pass configuration in a research-grade atomic layer deposition (ALD) chamber.

A combinatorial characterization scheme for high-throughput investigations of hydrogen storage materials.

In order to increase measurement throughput, a characterization scheme has been developed that accurately measures the hydrogen storage properties of materials in quantities ranging from 10 ng to 1 g. Initial identification of promising materials is realized by rapidly screening thin-film composition spread and thickness wedge samples using normalized IR emissivity imaging. The hydrogen storage properties of promising samples are confirmed through measurements on single-composition films with high-sensitivity (resolution <0.

Optical cell for combinatorial in situ Raman spectroscopic measurements of hydrogen storage materials at high pressures and temperatures.

An optical cell is described for high-throughput backscattering Raman spectroscopic measurements of hydrogen storage materials at pressures up to 10 MPa and temperatures up to 823 K. High throughput is obtained by employing a 60 mm diameter × 9 mm thick sapphire window, with a corresponding 50 mm diameter unobstructed optical aperture. To reproducibly seal this relatively large window to the cell body at elevated temperatures and pressures, a gold o-ring is employed.

Characterization of metal oxide nanofilm morphologies and composition by terahertz transmission spectroscopy.

An all-optical terahertz absorption technique for nondestructive characterization of nanometer-scale metal oxide thin films grown on silicon substrates is described. Example measurements of laser-deposited TiO2 and atomic layer-deposited films of HfO2 are presented to demonstrate applicability to pure Y2O3, Al2O3, and VOx and mixed combinatorial films as a function of deposition conditions and thickness. This technique is also found to be sensitive to HfO2 phonon modes in films with a nominal thickness of 5 nm.

Raman spectroscopy of n-type and p-type GaSb with multiple excitation wavelengths.

The interpretation of Raman spectra of GaSb can be complicated by the presence of a so-called surface space-charge region (SSCR), resulting in an inhomogeneous near-surface Raman scattering environment. To fully interpret Raman spectra, it is important to have an understanding of the SSCR profile relative to the Raman probe depth. However, a priori determination of even the actual SSCR width is not always possible for GaSb under a wide range of doping levels.

Adsorption behavior of DNA-wrapped carbon nanotubes on self-assembled monolayer surfaces.

We have examined the adsorption of DNA-wrapped single-walled carbon nanotubes (DNA-SWNTs) on hydrophobic, hydrophilic, and charged surfaces of alkylthiol self-assembled monolayers (SAMs) on gold. Our goal is to understand how DNA-SWNTs interact with surfaces of varying chemical functionality. These samples were characterized using reflection absorption FTIR (RAIRS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy.