(Invited) Unit Steps of an ALD Half-Cycle

Abstract

ALD is based on exposing the substrate sequentially to selflimiting surface reactions with two or more reactants. The elemental step of the ALD deposition method is called the halfcycle, i.e. the pulse and purge step of one precursor. While in the open literature, the ALD deposition has vigorously been studied from the surface chemistry point of view, the fundamental unit steps from an engineering point of view are much less studied subjects. In this paper, the unit steps that an ALD reactor has to perform in order to approach the ideal ALD half-cycle, namely a square wave partial pressure pulse followed by perfect purging of the reactor are discussed.

Conformality of atomic layer deposition in microchannels: impact of process parameters on the simulated thickness profile

“…39,47 The adsorption density of the surface was set to 4 nm -2 , which is in the range observed for the TMA-water process 31,48,49 and in the range typical for ALD. 41 The molar mass of Reactant A was set to an arbitrary value of 100 g mol -1 , while that of the purge gas was typical for nitrogen (28 g mol -1 ). The diameters of Reactant A and the inert gas were 600 and 374 pm, respectively, as in the TMA-water simulation.…”

“…18 It is expected that the partial pressure of Reactant A behaves like a step function: during the reactant pulse, the pressure at the microchannel entrance is pA0, and otherwise it is zero. 3,41 An inert carrier gas, denoted here with "I" (instead of the notation "B" used in the Ylilammi et al 18 article, to avoid confusion with Reactant B 3 ), is used to aid the transport of Reactant A from the source to the surface. The inert gas has the same partial pressure pI (Pa) inside and outside of the microchannel.…”

Conformality of atomic layer deposition in microchannels: impact of process parameters on the simulated thickness profile

“…18 It is expected that the partial pressure of Reactant A behaves like a step function: during the reactant pulse, the pressure at the microchannel entrance is pA0, and otherwise it is zero. 3,38 An inert carrier gas, denoted here with "I" (instead of the notation "B" used in the Ylilammi et al 18 article, to avoid confusion with Reactant B 3 ), is used to aid the transport of Reactant A from the source to the surface. The inert gas has the same partial pressure pI (Pa) inside and outside of the microchannel.…”

“…36,44 The adsorption density of the surface was set to 4 nm -2 , which is in the range observed for the TMA-water process 31,45,46 and in the range typical for ALD. 38 The molar mass of Reactant A was set to an arbitrary value of 100 g mol -1 , while that of the purge gas was typical for nitrogen (28 g mol -1 ). The diameters of Reactant A and the inert gas were 600 and 374 pm, respectively, as in the TMA-water simulation.…”

Apparatus for Characterizing Gas-Phase Chemical Precursor Delivery for Thin Film Deposition Processes

“…(This differs from the previous case, in which only the precursor partial pressure is measured). Furthermore, Fpr can be used to calculate a source efficiency term, which can help to quantify system nonideality [28] (although not necessarily aid in the identification of sources of any nonideality).…”