Sealing of low-k dielectric (k=2.0) with self-assembled monolayers (SAMs) for the atomic layer deposition (ALD) of TiN
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Sealing of low-k dielectric (k=2.0) with self-assembled monolayers (SAMs) for the atomic layer deposition (ALD) of TiN Yiting Sun1,2, Elisabeth Levrau4, Michiel Blauw3, Johan Meersschaut1, Patrick Verdonck1, Herbert Struyf1, Christophe Detavernier4, Mikhail Baklanov1, Steven De Feyter2, Silvia Armini1 1
imec, Kapeldreef 75, B-3001, Leuven, Belgium KU Leuven, Department of Chemistry, Celestijnenlaan 200f, 3001 Heverlee 3 imec-NL, Holst center, Eindhoven, The Netherlands 4 Department of Solid State Sciences, CoCooN, Ghent University, Krijgslaan 281 (S1), Ghent 9000, Belgium 2
ABSTRACT In this work, a novel low dielectric constant (low-k) pore sealing approach was engineered by depositing firstly a sub-2 nm SAMs and then a 3 nm TiN barrier film. The low-k film was pretreated by plasma to introduce hydroxyl groups onto the surface, followed by SAMs deposition. Then a TiN film was deposited from tetrakis(dimethylamino)titanium (TDMAT) via ALD as a dielectric barrier. Penetration of Ti atoms into low-k was measured and used to evaluate the sealing ability of SAMs. For the samples covered with SAMs, around 90% reduction of Ti atoms penetration was achieved. The pore radius was reduced to below 0.5 nm after the barrier deposition. The ∆k after pretreatment and after SAMs are 0.1 and 0.16, respectively. INTRODUCTION Low-k materials are developed to meet the ever increasing RC delay challenges in the IC industry [1]. In this respect, SiCOH low-k materials with k values as low as 2.0 show a huge application potential. Approximately 50% porosity and pore diameters larger than 3 nm are introduced to decrease the k value. However, porous low-k materials have issues of intrinsically low mechanical strength and low chemical resistance. Those issues are amplified during the integration steps by the large pore size. For porous low-k material to be integrated into the nextgeneration microelectronic devices, the pores have to be sealed so as to prevent diffusion of metal ions, water and precursors from barrier and copper seed deposition [2]. Many attempts have been made in order to seal the mesoporous low-k materials [3]. One strategy is to seal via plasma treatment [4] or UV-ozone [5]. However, most pore sealing plasma and UV-ozone treatments are detrimental for low-k films. Another strategy is to deposit silicon compounds as sealant film, however, the k value of these sealants are also high [6]. Polymer spin-coating has also been reported [7]. However, the application would be limited by sidewall geometry, and the sealing layer thickness is less easy to be controlled. Researchers have already seen SAMs as a potential low-k pore sealing approach against barrier penetration [8]. However, to the knowledge of the author, sealing with SAMs against penetration of dielectric barrier on low-k has not been reported.
The goal of this work is to deposit a SAMs sealing layer which would seal the mesopores and stop the barrier precursor from penetrating. The sealing layer should seal the pores with the minimal thickness and minimal dielectric
