Direct Measurements of Half-Cycle Reaction Heats during Atomic Layer Deposition by Calorimetry

High Resolution Image Download MS PowerPoint Slide We introduce a new high-temperature adsorption calorimeter that approaches the ideal limit of a heat detector whereby the signal at any time is proportional to the heat power being delivered to the sample and prove its sensitivity for measuring pulse-to-pulse heats of half-reactions during atomic layer deposition (ALD) at 400 K. The heat dynamics of amorphous Al 2 O 3 growth via sequential self-limiting surface reaction of trimethylaluminum (TMA) and H 2 O is clearly resolved. Calibration enables quantitation of the exothermic TMA and H 2 O half-reactions with high precision, −343 kJ/mol TMA and −251 kJ/mol H 2 O, respectively. A time resolution better than 1 ms is demonstrated, allowing for the deconvolution of at least two distinct surface reactions during TMA microdosing. It is further demonstrated that this method can provide the heat of reaction versus extent of reaction during each precursor’s half-reaction, thus providing even richer mechanistic information on the surface processes involved. The broad applicability of this novel calorimeter is demonstrated through excellent signal-to-noise ratios of less exothermic ALD half-reactions to produce TiO 2 and MnO.