RESUMO
A description is given of the design and performance of a diagnostic-accessible, perpendicular-flow, single-wafer deposition reactor for use with 50 mm wafers. The reactor chamber design is based on a simple flow tube, with diagnostic access achieved by replacing sections of the reactor chamber wall with recessed diagnostic ports. Reactor chamber performance is evaluated for the purpose of performing optical measurements during atomic layer deposition (ALD). Computational fluid dynamics simulations predict that the when used with windows the diagnostic port design produces minimal perturbations to the gas flow under typical deposition conditions, as compared to a design without diagnostic ports. Temperature measurements of the inside surface of a window installed in a diagnostic port suggest that for reactor chamber operation at 110 °C, under typical deposition conditions, the inside surface window temperature is approximately equal to or greater than the surrounding reactor chamber temperature, thereby minimizing possible species condensation on the window surface. As a consequence of using recessed diagnostic ports, an increase in the amplitude of optical intensity fluctuations was generally observed when performing measurements at elevated chamber temperatures. These intensity fluctuations could be readily reduced by enclosing the optical path to the exterior side of the windows. The performance of two straight-forward methods to reduce these intensity fluctuations is presented. The results outlined above demonstrate that this reactor design can be operated with short gas residence times and with all reactor surfaces at elevated temperatures, making it useful for simulating a wide range of gas flow conditions with relevance to microelectronics-related ALD processes.
RESUMO
Metal alkylamide compounds, such as tetrakis(ethylmethylamido) hafnium (TEMAH), represent a technologically important class of metalorganic precursors for the deposition of metal oxides and metal nitrides via atomic layer deposition (ALD) or chemical vapor deposition. The development of in situ diagnostics for processes involving these compounds could be beneficial in, e.g., developing deposition recipes and validating equipment-scale simulations. This report describes the performance of the combination of two techniques for the simultaneous, rapid measurement of the three major gas phase species during hafnium oxide thermal ALD using TEMAH and water: TEMAH, water, and methylethyl amine (MEA), the only major reaction by-product. For measurement of TEMAH and MEA, direct absorption methods based on a broadband infrared source with different mid-IR bandpass filters and utilizing amplitude modulation and synchronous detection were developed. For the measurement of water, wavelength modulation spectroscopy utilizing a near-IR distributed feedback diode laser was used. Despite the relatively simple reactor geometry employed here (a flow tube), differences were easily observed in the time-dependent species distributions in 300 mL/min of a helium carrier gas and in 1000 mL/min of a nitrogen carrier gas. The degree of TEMAH entrainment was lower in 300 mL/min of helium compared to that in 1000 mL/min of nitrogen. The capability to obtain detailed time-dependent species concentrations during ALD could potentially allow for the selection of carrier gas composition and flow rates that would minimize parasitic wall reactions. However, when nitrogen was employed at the higher flow rates, various flow effects were observed that, if detrimental to a deposition process, would effectively limit the upper range of useful flow rates.
