Atomic Layer Deposition Chemistry: Recent Developments and Future Challenges

Abstract

New materials, namely high-k (high-permittivity) dielectrics to replace SiO(2), Cu to replace Al, and barrier materials for Cu, are revolutionizing modern integrated circuits. These materials must be deposited as very thin films on structured surfaces. The self-limiting growth mechanism characteristic to atomic layer deposition (ALD) facilitates the control of film thickness at the atomic level and allows deposition on large and complex surfaces. These features make ALD a very promising technique for future integrated circuits. Recent ALD research has mainly focused on materials required in microelectronics. Chemistry, in particular the selection of suitable precursor combinations, is the key issue in ALD; many interesting results have been obtained by smart chemistry. ALD is also likely to find applications in other areas, such as magnetic recording heads, optics, demanding protective coatings, and micro-electromechanical systems, provided that cost-effective processes can be found for the materials required.

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

“…CH 4 (methane) adsorbs very weakly on Ru(0001) with an adsorption energy of about 20 meV. Of the four possible adsorption sites on the Ru(0001) surface (bridge, fcc, hcp, and ontop), CH x (x = 1 or 2) fragments and C adsorb preferentially on a hcp site.…”

“…E ads,near : adsorption energy with respect to 1 H atom co-adsorbed in the same supercell and (n−1) H atoms each adsorbed in a separate supercell (eq 3). E ads,far : adsorption energy with respect to n H atoms each adsorbed in a separate supercell (eq 2) (n = 4 and 6 for CH 4 (methane) and CH 3 CH 3 (ethane) respectively). The Journal of Physical Chemistry C and the organic fragment.…”

“…Thus, both traditional catalytic processes, like the Fischer− Tropsch process and precursor decomposition on noble metal surfaces, can benefit from the study of C−H bond scission and formation reactions. (Note: Names of all the hydrocarbon fragments used in this paper are derived from the names of the gas phase molecules: CH 4 (methane), CH 3 CH 3 (ethane), CH 2 CH 2 (ethene), and CHCH (ethyne). For a fragment derived from one of the gas phase molecules and short of 1 H, -ane (-ene, -yne) is modified to -yl (-eneyl, -ynyl).…”

“…Since CH 3 (methyl) and CH 3 CH 2 (ethyl) groups are just one H atom short of CH 4 (methane) and CH 3 CH 3 (ethane), we include the latter also in the present study. Since the elementary reactions in CH 4 (methane) are obvious, the decomposition pathway for CH 3 CH 3 (ethane) on the Ru(0001) surface, including all the intermediates, is shown in Figure 1.…”

Surface Chemistry of Copper(I) Acetamidinates in Connection with Atomic Layer Deposition (ALD) Processes

“…[4][5][6][7][8] They have proven particularly useful in atomic layer deposition (ALD) processes, where the surface chemistry of film growth is split into two self-limiting and complementary half-reactions in order to control the deposition at a monolayer level. [9][10][11] Ideally, the metal-based precursor in metal ALD processes should adsorb on the substrate until saturation of a monolayer, preferably retaining the structure of most if not all of its ligands intact, after which a second reactant is introduced to remove those ligands and to activate the surface for the next ALD cycle.…”