(A) study on the growth kinetic modeling for atomic layer deposition of multi-component thin films

Abstract

Atomic layer deposition (ALD) has become an essential technique for fabricating nano-scale thin films in the microelectronics industry, and its applications have been extended to multi-component thin films, as well as to single metal oxide and nitride films. A mathematical film growth model for ALD is proposed to predict the deposition characteristics of multi-component thin films grown mainly in the transient regime, where the film thickness varies non-linearly with the number of cycles. The non-linear behavior of the growth rate and the composition of multi-component thin films deposited by ALD depend on the precursor used and adsorbing surface. Hence, the equations to describe the change of surface coverage with precursor adsorption and the surface reaction are derived. The area reduction ratio is introduced as a parameter related to the number of adsorbed precursor molecules per unit-area. The growth rate and composition of multi-component thin film in ALD will be derived by describing the surface which is varied with ALD cycles and formulating the followed changes of the adsorbed amount of precursor. In order to describe the time-dependent surface coverage of precursor during the precursor pulse, a differential equation is used and explains the adsorption kinetics. Also, the surface change between ALD cycles before precursor adsorption and after reaction of the adsorbed precursor is described using recursive equations. From the solution of two equations, the growth rate which, in ALD, means the deposited film thickness per cycle can be obtained. Especially, the composition of metal atoms in multi-component thin film can be predicted. Theoretical examples and applications of this proposed model to practical investigations illustrate ALD characteristics. In order to apply the model to real system, Ti-AI-O, Sr-Ti-O, and Hf-Al-O of which candidate dielectrics can be used as DRAM capacitors were deposited and the experimental data of growth rate and composition...