Plasma-enhanced atomic layer deposition of SiO2 film using capacitively coupled Ar/O2 plasmas: A computational investigation

Abstract

Plasma-enhanced atomic layer deposition (PE-ALD) is widely used for dielectric deposition in semiconductor fabrication due to its ability to operate at low temperatures while having high precision control. The PE-ALD process consists of two subcycles: precursor dosing and plasma exposure with gas purging and filling in between. In the PE-ALD of SiO2, a Si-containing precursor is first deposited on the surface, usually in a plasma-free environment. The surface is then exposed to an oxygen-containing plasma during which the residual components of the precursor are removed and the Si oxidized. Various factors affect the outcome of SiO2 PE-ALD, such as exposure times during each step, steric hindrance of the Si precursor, and plasma properties, such as the energy of ions incident onto the film. The results from computational investigations of the first layers of SiO2 PE-ALD at both reactor (cm) and feature (nm) scales are discussed in this paper. The example system uses bis(tertiary-butylamino)silane, SiH2[NH(C4H9)]2 as the silicon precursor during dosing and plasmas operating in Ar/O2 gas mixtures during the oxidation step. Parametric studies were performed for blanket deposition, as well as deposition in trenches and vias while varying power, pressure, plasma exposure time, aspect ratio, and ligand retention in the film. The general trends show that conditions that reduce the fluence of reactive oxygen species typically decrease the O/Si ratio, increase the vacancies in the films, and decrease the order of the film. Conditions that result in higher ion fluxes having higher energies produce the same result due to sputtering. The retention of ligand groups from the precursor significantly decreased growth rates while increasing vacancies and reducing the O/Si ratio.

Review and future perspective of feature scale profile modeling for high-performance semiconductor devices

“…For recent 5 years, useful simulation techniques have been adopted to the ALD process. Miyano et al 96 Qu et al 98 developed a detailed SiO 2 -PEALD model with the cycle of SiH 2 ½NHðC 4 H 9 Þ 2 precursor [called bis(tertiary-butylamino)silane (BTBAS)] step and Ar∕O 2 plasma step using a cell removable method. A CCP reactor with a 300 mm diameter and gap length of 1.5 cm was assumed.…”

“…Consequently, defects such as vacancies were generated in the film, which was reasoned as an effect of not considering the surface diffusion of reactive oxygen species in the model. 98 Furthermore, as shown in Fig. 46, the deposited SiO 2 feature scale profiles in the hole patterns with the different ARs of 2, 4, 6, and 8 (30 nm diameter) were calculated by the model.…”

“…Qu et al 98 . developed a detailed SiO2-PEALD model with the cycle of SiH2[NH(C4H9)]2 precursor [called bis(tertiary-butylamino)silane (BTBAS)] step and Ar/normalO2 plasma step using a cell removable method.…”

“…(a) Flow chart of the SiO2-PEALD process with precursor and Ar/normalO2 step and (b) simulated film demonstrating the impact of ligand remnant 98 …”

“…Predicted SiO2 deposition profiles on the hole pattern (a) with the AR of 4 and (b) with different ARs for the PEALD process 98 …”