Thin film vapor deposition processes, e.g., chemical vapor deposition, are widely utilized in high volume manufacturing of electronic and optoelectronic devices. Ensuring desired film properties and maximizing process yields requires 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 for investigating such factors when using in situ optical techniques. The apparatus simulates a single precursor delivery line, e.g., in a chemical vapor deposition tool, and incorporates an optical flow cell downstream of a precursor-containing ampoule. When utilized with an optical technique that can measure precursor density, the precursor flow rate can be determined using this apparatus and, for selected conditions, the precursor partial pressure in the ampoule head space 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 head space pressure is 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 of this report will be on low-volatility precursors that are delivered on a system with pressures less than about 13 kPa downstream of the ampoule and on commercial 1.5 L ampoules incorporating a five- valve cluster. An important goal of this work is to provide data that could facilitate both deposition process optimization and ampoule design refinement.
Journal of Research (NIST JRES) -
ALD, atomic layer deposition, CVD, chemical vapor deposition, precursor delivery, thin film deposition