materials ALD films
Platinum ALD films
Atomic layer deposition (ALD) is gaining traction as a viable manufacturing method for future devices and qualification continues on an array of materials and potential applications.Dr. Qi Fang and Dr. Tom Sharp of Oxford Instruments Plasma Technology, discuss results of both remote-plasma and thermal-ALD processing for the deposition of ultra thin platinum films.
U
FlexAL,Oxford Instruments Plasma Technology
ltrathin metallic layers such as Platinum (Pt), Ruthenium (Ru), Palladium (Pd) and Copper (Cu) deposited onto oxide structural surfaces have wide applications in microelectronics, catalysis, photonics and chemical sensing [1-4]. Platinum films have a variety of potential applications in nanotechnology, microelectronics and energy technologies due to their chemical stability, catalytic activity, and excellent electronic properties [5-7]. During the past decade atomic layer deposition (ALD) has emerged as an outstanding technique to achieve accurate thickness and self-limiting control and is used to fabricate ultrathin and conformal thin film structures. This is useful for many potential applications in advanced high dielectric constant (high-k) gate oxides, electrode and connection materials, storage capacitor dielectrics and copper diffusion barriers in advanced electronic devices, as well as for solar energy and biological applications [8, 9].
A unique attribute of ALD is that it uses sequential self-limiting surface reactions to achieve control of film growth in the monolayer or sub-monolayer thickness regime. Therefore, ALD is receiving wide attention for the ultrathin layers grown onto micro- and nano-devices with three-dimension in a high aspect ratio. Furthermore, ALD can also be used for any advanced technologies that require control of film structure in the nanometer or sub- nanometer scale due to its capacity for self-terminating conformal layer formation.
Most Pt ALD processes reported used thermal ALD process using
methylcyclopentadienyl trimethylplatinum 14
www.siliconsemiconductor.net Issue III 2012
(MeCpPtMe3) and O2 gas [10-12]. This process is based on the dissociative chemisorption of O2 on the Pt surface for oxidative decomposition of the
precursor ligands [13]. However, this oxidative decomposition becomes extremely difficult in the initial stage of a thermal ALD process (before formation of Pt nano-particles), leading to a nucleation delay. Knoops and his co-authors
reported on the Pt and Pt O2 processes by using both remote plasma ALD and the thermal ALD of Pt. Their work shows that the remote plasma process leads to immediate growth without substantial nucleation delay, while the thermal ALD process leads to no growth at all unless a Pt starting surface
or a high O2 pressure is employed [1]. In the O2 plasma, O radicals are created, providing atomic O to the surface directly from the gas phase, enhancing oxygen chemisorption on the surface and oxidation of the precursor ligands. [14]
However, despite its successful Pt depositions, the ALD process lacks a detailed atomic-scale understanding of the formed interface structure and the effect of substrate used on the Pt growth, which is extremely important for microelectronic applications. In this work, platinum films were grown
on Si wafers, SiO2, Al2O3 and high-k dielectric HfO2 ALD films on Si substrates by both remote plasma and thermal atomic layer deposition (ALD), using methylcyclopentadienyltrimethyl platinum
(MeCpPtMe3) and O2 as precursors. The Pt ALD growth behaviours with precursor dose times, O2 or O2 plasma exposures and substrates are investigated. Furthermore, the Pt ALD process on
various oxide substrates, Pt nucleation process, electrical property and chemical impurities of the Pt thin film are also discussed.
Experimental
The Pt films were deposited in an ALD system with load-lock delivery (FlexAL, Oxford Instruments Plasma Technology). The deposition system was
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