Novel Silicon deposition processes by ALD (SiALD)

The SiALD project focuses on efficient deposition of silicon containing materials by atomic layer deposition. A success in these attempts will enable efficient production of electronic devices and will most probably enable new types of technologies. The project consists of several parts covering from synthesis of precursors via deposition, in situ analysis to characterization and theoretical calculations. During the project we have continued on development of Si(II) and Si(IV) compounds with several new types of ligands with the aim of achieving new types of precursors for deposition. An extensive survey of all Si-related materials deposited by ALD or closely related techniques have been done. Initial tests for deposition of Si-containing materials have been performed using (Me3Si)4Si in combination with O3, NH3, and H2O. We have discovered that an interplay of several anion sources are necessary in order to obtain deposited material. SiO2 films were deposited using (Me3Si)4Si and a combination of NH3 and O3 in the temperature range 350 - 450 °C. Additional alternative precursors like bis(dimethylamino)dimethylsilane (BDMADMS), 2,2-disilyltrisilane, 1,2-diisopropyldisilane and hexaethyldisilane have also been investigated during the course of the project. As in the previous case, the precursors were tested in combination with O3, NH3, H2O, and a selection of carboxylic aids for formation of hybrid materials. The BDMADMS precursor worked well in combination with ozone, and resulted in a low-temperature, high-growth rate SiO2-process. The successful processes have resulted in high-purity SiO2-materials. Several feasibility studies have been undertaken with respect to characterization of growth by spectroscopic means and an in situ FTIR ALD characterization tool was attempted constructed. Numerous different types of Si based precursors have been modelled with respect to reactivity and suitability as precursor for ALD growth. The interaction between these precursors and different types of Si, Si-H and Si-OH terminated surfaces have been calculated. Among the studied 85 Si content precursors only two [C7H12OSi -Methoxy-trivinyl-silane and C7H9NSi -Benzyliminosilane] of them shows positive indications for ALD reactivity for Si deposition. On the other hand more than 10 precursors (ex: C10H22N2Si, SiCl2H2) show positive indications for SiO2 ALD reactivity. As a summary, the current project has shed light into numerous new types of Si based precursors and has currently developed new precursors which will form basis for further projects investigating these compounds. Several potential systems have been tested and some found successful, precursor delivery systems have been built and tested - including prototypes, new reactor tools have been built. Competence has been built with respect to Si-reactivity, in situ characterizations, precursor delivery systems, and more.

The development of low cost, high energy efficiency thin-film solar cells is a key to future scale up implementation of photovoltaics. The proposed fundamental study addresses novel processes for deposition of ultrathin films of silicon materials by atomi c layer deposition (ALD). The aim of the project is to develop cheap, scalable processes for silicon containing materials applicable in PV processes of next generation solar cells. Although the ALD technique is relatively mature, no scalable processes for deposition of silicon type materials such as Si, SiOx, SiC, and SiNx are at hand. The project is expected to lead to novel processes for such types of materials with a potential for rapid industrial implementation. The project will develop novel types of compounds containing silicon suitable as precursors for thin film deposition by ALD. The compounds are distinctly beyond state of art and will cover a new range of ALD chemistry with respect to silicon materials. The project is constructed from four sub -projects with emphasis on: WP1: Development of novel precursors WP2: Development of ALD processes based on novel precursors WP3: Reaction modeling of novel precursors WP4: in situ/ex situ characterization of processes and deposited materials The differe nt sub-projects are mutually benefit from each other and aid in design of novel materials and processes.