Thin film vapor deposition processes, e.g., chemical vapor deposition, are
widely used in high-volume manufacturing of electronic and optoelectronic devices.
Ensuring desired film properties and maximizing process yields require control of
the chemical precursor flux to the deposition surface. However, achieving the
desired control can be difficult due to numerous factors, including delivery system
design, ampoule configuration, and precursor properties. This report describes an
apparatus designed to investigate such factors. The apparatus simulates a single
precursor delivery line, e.g., in a chemical vapor deposition tool, with flow
control, pressure monitoring, and a precursor-containing ampoule. It also
incorporates an optical flow cell downstream of the ampoule to permit optical
measurements of precursor density in the gas stream. From such measurements, the
precursor flow rate can be determined, and, for selected conditions, the precursor
partial pressure in the headspace can be estimated. These capabilities permit this
apparatus to be used for investigating a variety of factors that affect delivery
processes. The methods of determining the pressure to (1) calculate the precursor
flow rate and (2) estimate the headspace pressure are discussed, as are some of the
errors associated with these methods. While this apparatus can be used under a
variety of conditions and configurations relevant to deposition processes, the
emphasis here is on low-volatility precursors that are delivered at total pressures
less than about 13 kPa downstream of the ampoule. An important goal of this work is
to provide data that could facilitate both deposition process optimization and
ampoule design refinement.
Apparatus for Characterizing Gas-Phase Chemical Precursor Delivery for Thin Film
Deposition Processes
