Real-time observation and optimization of tungsten atomic layer deposition process cycle

In the search for a chemical sensing strategy to monitor atomic layer deposition (ALD) processes suitable for real-time application in wafer manufacturing, we have applied downstream mass spectrometry sampling to study process dynamics during ALD cycles for tungsten deposition from WF6 and SiH4. The ALD reactor has UHV cleanliness conditions and incorporated a minireactor chamber to simulate the small reaction volume anticipated for manufacturing tools to achieve adequate throughput. Mass spectrometry revealed essential surface reaction dynamics through real-time signals associated with by-product generation as well as reactant introduction and depletion for each ALD half-cycle. These were then used to optimize process cycle time and to study the effect of process recipe changes on film growth. The reaction by-products were clearly observed as H2 from SiH4 exposure and SiF4 from WF6 exposure. For each of the two half-cycles, rapid increase of by-product leds to steady-state adsorption/reaction conditions,...