Frequently, desirable precursors for CVD/ALD are liquids at room temperature. Liquids with high vapor pressure, high decomposition temperature and low viscosity can be vaporized relatively easily for gas-phase processing; however care must be taken to ensure there are no particulate byproducts formed during vaporization, that the vapor concentration output is steady, and that response times are fast enough for short pulse processing (ALD).
Advances in high ĸ, low ĸ and metal barrier/interconnect thin films has required use of more difficult to vaporizer precursors. Liquids that have a narrow thermal window between vaporization temperature and thermal decomposition (TEMAZr, CCTBA) and/or have low vapor pressure can be very problematic to vaporize. Additionally, for many CVD processes, increased vapor concentration can lead to increased deposition rates and higher film densities. Important factors to consider for optimum vaporization will be presented. Theoretical limits and practical challenges will be discussed. A novel technique using a direct liquid injection, droplet atomization method, will be presented as an alternative to conventional techniques like bubblers and DLI valves. Response time curves, vapor pressure curves, and maximum vapor concentrations achievable using a Performance Enhanced Turbo-Vaporizer™ will be presented for a variety of different chemistries commonly used for CVD/ALD.