An Experimental and Theoretical Study of the Impact of the Precursor Pulse Time on the Growth Per Cycle and Crystallinity Quality of TiO2 Thin Films Grown by ALD and PEALD Technique

Author(s)

Chiappim, William ^[1] ; Fraga, Mariana Amorim ^[2] ; Maciel, Homero Santiago ^{[3, 4]} ; Pessoa, Rodrigo Savio ^{[3, 4]}

Affiliation

^[1] Univ Aveiro, Dept Fis, i3N, Campus Univ Santiago, Aveiro - Portugal

^[2] Univ Fed Sao Paulo, Inst Ciencia Tecnol, Sao Jose Dos Campos - Brazil

^[3] Univ Brasil, Inst Cient & Tecnol, Sao Paulo - Brazil

^[4] Inst Tecnol Aeronaut ITA, Lab Plasmas Proc LPP, Sao Jose Dos Campos - Brazil

• Document type: Journal article
• Source: FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND; v. 6, OCT 28 2020.
• Web of Science Citations: 0

Abstract

In this paper, theoretical and experimental approaches were used to evaluate the impact of the precursor's pulse time on the growth per cycle and the crystallinity quality of atomic layer deposited TiO2 thin films on Si(100) and FTO substrates. We employ a general model that can be applied to both metal and oxidant precursors, based on the Maxwell-Boltzmann velocity distribution from which the molecular flux of gases that collide with the substrate is deduced to adjust the experimental characteristics of growth per cycle vs. pulse time. This model allowed us to adjust the growth per cycle of TiO2 films produced by thermal atomic layer deposition and by plasma-enhanced atomic layer deposition under different deposition parameters and substrates. The influence of growth per cycle on the chemical and structural properties of TiO2 thin films was evaluated by Rutherford backscattering spectroscopy, grazing incidence x-ray diffraction, and ellipsometry techniques. In thermal mode, using H2O as an oxidant precursor, the stoichiometry of TiOx films has an x value of 1.98 from the growth per cycle saturated regardless of the metal precursor or substrate used. Using O-2 plasma, a super-stoichiometric film with x values from 2.02 to 2.30 was obtained. In thermal mode, the growth per cycle saturated and film thickness are, on average, 40% higher for TiCl4 compared to TTIP precursor. Using O-2 plasma, the growth per cycle saturated is approximately twice as high as the thermal mode using the TTIP precursor. For both atomic layer deposition modes, the degree of crystallinity showed values of 50-80% for TiCl4 in the temperature range of 250-350 degrees C. For TTIP, it was below 40% in thermal mode and between 80 and 95% in plasma mode (250 degrees C). It was observed that the reaction rate, the diffusion coefficient, and the molecular flux are inversely proportional to the temperature. These results provide evidence that the crystallinity and epitaxial quality of the TiO2 film are higher for TTIP using O-2 plasma. However, we verified that there was better stability of the parameters analyzed for TiCl4 in the two atomic layer deposition modes. (AU)

• FAPESP's process: 16/17826-7 - Fabrication of MOS solar cells using structures Al/TiO2/SiO2/Si
• Grantee: William Chiappim Junior
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/01265-1 - Synthesis and microbiological analysis of polymer substrates coated with TiO2 and / or Al2O3 ultra-thin films by atomic layer deposition technology
• Grantee: Rodrigo Savio Pessoa
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/50773-0 - Center of excellence in physics and applications of plasmas
• Grantee: Ricardo Magnus Osório Galvão
• Support Opportunities: Research Projects - Thematic Grants