Establishing thermal stability of CVD and ALD precursors
An in-depth understanding of thermal stability of Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) precursors is critical for their successful commercialization. As a supplier of highly reactive and energetic materials to the semiconductor industry, we have strong capabilities to fully characterize the thermal stability of our precursors at all stages of the commercialization process. Initial precursor selection starts from understanding the feasibility of precursor delivery by its evaporation from a liquid or solid phase.
We also developed a methodology to calculate the vapor pressure of organosilicon and organo-metallic precursors from Thermogravimetric Analysis (TGA) analysis. To further understand the thermal stability of precursors, we use Differential Scanning Calorimetry (DSC) and a Thermal Screening Unit (TSU). These instruments are used to characterize phase changes and decomposition events during the heating. To ensure the safe delivery of highly energetic precursors to the tool, we conduct TSU analysis to monitor the pressure and sample temperature as a function of the oven temperature. TSU analysis provides important information about precursor thermal decomposition or phase change events.
To characterize precursor stability on the customer tool, we conduct long-term thermal tests, heating the precursor for one to 16 weeks at temperatures used on the customer tool. For other applications, the company conducts accelerated-aging experiments by heating the precursor at an elevated temperature for one to four weeks to estimate the degradation rate at ambient temperature for preliminary shelf-life determination or long-term storage purposes*. The precursor is analyzed before and after heating by a variety of analytical methods to gauge the thermal stability under simulated process or ambient storage conditions. During the final precursor production scale-up, we conduct an accelerated rate calorimetry test, which is a technique to detect the onset of precursor thermal decomposition.
These methods are complimentary analytical components that allow us to characterize key thermal stability parameters of precursors to ensure optimal performance and safety. The knowledge and expertise of our scientists have helped many customers to safely and successfully bring new materials into production.
*ASTM method F1980-07, Standard Guide for Accelerated Aging
Steve Mayorga is a research associate and has been with the company for 26 years. He graduated from UC Berkeley with a Ph.D. in Inorganic Chemistry.