Sunday, June 1, 2014

In situ characterization of ALD processes and study of reaction mechanisms for high-k metal oxide formation

"In situ characterization of ALD processes and study of reaction mechanisms for high-k metal oxide formation" is a fresh doctoral thesis to be defended 6th of June 2014 in Helsinki Finland by Mr Yoann Tomczak at University of Helsinki, Faculty of Science, Department of Chemistry, Laboratory of Inorganic Chemistry. To learn more on in-situ studies by QCM and QMS I recommend to read the doctoral thesis by Antti Rahtu that can be downloaded here.
 
Precursors, processes and materials studied in this thesis.
 
Yoann Tomczak
University of Helsinki, Faculty of Science, Department of Chemistry, Laboratory of Inorganic Chemistry
Doctoral dissertation (article-based), http://urn.fi/URN:ISBN:978-952-10-9926-7
 
Atomic Layer Deposition (ALD) is a thin film deposition method allowing the growth of highly conformal films with atomic level thickness and composition precision. For most of the ALD processes developed, the reaction mechanisms occurring at each step of the deposition remain unclear. Learning more about these reactions would help to control and optimize the existing growth processes and develop new ones more quickly. For that purpose, in situ methods such as quartz crystal microbalance (QCM) and quadrupole mass spectrometer (QMS) are used. These techniques present numerous advantages because they allow monitoring the thin film growth mechanisms directly during the process. Additionally, they do not require separate experiments or large amounts of precursors to test the efficiency of new processes and could be very effective means to monitor industrial processes in real time.

This thesis explores the most common in situ analytical methods used to study ALD processes. A review on the ALD metal precursors possessing ligands with nitrogen bonded to the metal center and their reactivity is provided. The results section reports the reaction mechanisms of ALD processes for the deposition of Nb2O5, Ta2O5, Li2SiO3, TiO2 and ZrO2. All the processes studied are using metal precursors with nitrogen bonded ligands and ozone or water for the deposition of high-k and other oxide films.
 
This is a Finnish article-based doctoral dissertation, the scientiffic work is mainly reported in the form of published or soon to be published journal articles:
 
I. “In situ reaction mechanism studies on the new tBuN=M(NEt2)3 -Water and tBuN=M(NEt2)3 - Ozone (M=Nb,Ta) Atomic Layer Deposition processes.” 
Y. Tomczak, K. Knapas, M. Sundberg, M. Ritala, M. Leskelä 
Chem. Mater.(2012), 24(9), 1555-1561 

II. “In situ reaction mechanism studies on atomic layer deposition of AlxSiyOz from Y. Tomczak, K. Knapas, S. Haukka, M. Kemell, M. Heikkilä, M. Ceccato, M. Leskelä, M. Ritalatrimethylaluminium, hexakis ethylaminodisilane and water.”
Chem. Mater.(2012), 24(20), 3859-3867
III. “In situ reaction mechanism studies on lithium hexadimethyldisilazide and ozone atomic layer deposition process for lithium silicate.”
Y. Tomczak, K. Knapas, M. Sundberg, M. Leskelä, M. Ritala
Journal of Physical Chemistry C (2013), 117(27), 14241-14246
 
IV. “In situ reaction mechanism studies on the Ti(NMe2)2(OiPr)2-D2O and Ti(OiPr)3(NiPr-Me-amd)-D2O Atomic Layer Deposition processes”
Y. Tomczak, K. Knapas, M. Ritala, M. Leskelä
Journal of Vacuum Science and Technology A: Vacuum, Surfaces, and Films (2014), 32(1), 01A121-01A121-7
V. “[Zr(NEtMe)2(guan-NEtMe)2] as a novel ALD precursor: ZrO2 film growth and mechanistic studies”
T. Blanquart, J. Niinistö, N. Aslam, M. Banerjee, Y. Tomczak, M. Gavagnin, V. Longo, E. Puukilainen, H.D. Wanzenböck, W.M.M. Kessels, A. Devi, S. Hoffmann-Eifert, M. Ritala, and M. Leskelä
Chem. Mater.(2013), 25(15), 3088-3095
 
VI. “Atomic layer deposition, characterization and growth mechanism of high quality TiO2 thin films”
VI. M. Kaipio, T. Blanquart, Y. Tomczak, J. Niinistö, M. Gavagnin, V. Longo, V. Pallem, C. Dussarrat, M. Ritala, M. Leskelä
submitted