CeeVeeTech's compensators and thermal environments for CVD and ALD precursors feature precision temperature sensors that are inserted via a thermal well directly into a liquid or solid deposition source. The temperature measurement is used to compensate for the temperature excursions that are caused by various factors encountered during CVD and ALD.
All liquid and solid CVD, MOCVD and ALD source compounds cool when they are evaporated to deliver precursor to the deposition process. Depending on the conditions the temperature drop can amount to more than 2 degrees C. The vapor pressure of common deposition sources changes between 2% and 10% per degree C. At room temperature, the vapor pressure of water changes by 5.5% per degree C, trimethygallium by 4%, and trimethylindium by 9%.
The process design uses a nominal temperature and assumes that the precursor is at that temperature. The difference between actual precursor temperature and nominal temperature can result in yield loss. The CeeVeeTech compensators modify the signal to the mass flow controller or pressure controller to compensate for the lower temperature. This way the CeeVeeTech compensators insure that the intended amount of precursor is delivered to the CVD process at all times.