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

Abstract

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.

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

“…Psys FC was obtained from the CDG2 reading with a correction for the pressure drop that exists between CDG2 and FC when gas was flowing. The pressure drop was estimated using the Hagen–Poiseuille equation 34,36 where Q is the throughput, η is the gas viscosity, l is the distance between the flow cell and CDG2, d is the tube diameter, and (Psys CDG2) is the system pressure measured at the CDG2 location. Integration of the respective time-dependent actual flow rate for the duration of an injection yields the mass of PDMAT or DMA delivered in that injection.…”

“…The characteristics of the flow system shown in Fig. 2 have been previously reported 34 and will only be described briefly here. The PDMAT ampoule shown was configured with a five-valve cluster that includes three pneumatic two-port valves (PV1, PV2, and PV3) and two manual three-port valves (MV1 and MV2).…”

“…5). 34 Hence, the decrease in PDMAT partial pressure from the ampoule head space to the measurement location is relatively small. In contrast, the CDG1/ CDG2 pressure ratio increases into the range of 8 to 10 for CDG2 pressures in the range of 190 Pa to 610 Pa.…”

“…P FC sys was obtained from the CDG2 reading with a correction for the pressure drop that exists between CDG2 and FC when gas was flowing. The pressure drop was estimated using the Hagen-Poiseuille equation 34,36…”

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

“…In our efforts to quantify precursor delivery, we have developed inline, optics-based measurements. [15][16][17][18][19] These have an advantage over ultrasonic monitors commonly used for monitoring precursor delivery since low concentrations in low-pressure gas lines can be measured optically whereas ultrasonic sensors are limited to operating pressures > 4 kPa. 20 Our measurements have allowed us to study the delivery of industrially relevant organometallic precursors like μ 2 -η 2 -( t Bu-acetylene)dicobalthexacarbonyl (CCTBA) 17,19 and pentakis(dimethylamido)tantalum (PDMAT).…”