AVS 49th International Symposium
    Thin Films Wednesday Sessions
       Session TF+VT-WeM

Paper TF+VT-WeM4
Importance of Hydrogen Recombination on Flow Tube Walls During Hydrogen Radical-Assisted Metal Atomic Layer Deposition

Wednesday, November 6, 2002, 9:20 am, Room C-101

Session: Atomic Layer Deposition - Barriers & Nitrides
Presenter: R.K. Grubbs, University of Colorado, Boulder
Authors: R.K. Grubbs, University of Colorado, Boulder
S.M. George, University of Colorado, Boulder
Correspondent: Click to Email
Many metals can be deposited with atomic layer control using hydrogen radical-assisted metal atomic layer deposition (ALD). Designing the hydrogen plasma source and hydrogen radical delivery for efficient hydrogen radical-assisted metal ALD in a viscous flow reactor offers many challenges. In particular, hydrogen recombination on the flow tube walls to form H@sub 2@ is a serious loss to the hydrogen radical flux. To quantify the hydrogen radical flux and its loss caused by hydrogen recombination on the flow tube walls, a dual thermocouple probe was constructed based on exposed and covered Pt/Rh thermocouple junctions. This probe measured hydrogen radical concentration by determining the heat evolved from hydrogen radical recombination on the exposed thermocouple surface. The thermocouple probe was then employed to measure hydrogen radical concentration versus distance from the hydrogen radical source for four flow tube materials. The hydrogen radical concentration decreased dramatically versus distance and was different for stainless steel, aluminum, pyrex and quartz flow tube materials. By modeling the decrease in hydrogen radical concentration versus distance, a hydrogen radical recombination coefficient could be determined from the data. The recombination coefficient ranged from @gamma@= 1.5x10@super -4@ for stainless steel to @gamma@= 5.7x10@super -5@ for pyrex. Given the magnitude of the hydrogen radical recombination coefficients, the reaction chamber for hydrogen radical-assisted metal ALD must be positioned very close to the hydrogen radical source.