Studies on Dielectric Properties of Annealed Reactively Co-Sputtered Bcn Thin Films

The main concern in the Ultra Large Scale Integrated (ULSI) semiconductor devices is the reduction of signal propagation delay. This delay ( ) is the product of electrical resistance of wiring metal and the parasitic capacitance of the Inter dielectric layer (IDL).  The motivation behind the boron carbon nitride (BCN) ternary compounds is their similarities in the structure and difference in properties between graphite and hexagonal boron nitride (h-BN). Both theoretical calculations and experimental studies show that BCN compounds exhibit excellent mechanical, optical and electrical properties [1], [2]. It has been reported that the addition of carbon atoms to BN films is effective in reducing the dielectric constant. Also the structure of BCN film has a strong impact on dielectric constant [3]. The BCN deposition by chemical vapor deposition (CVD) has been reported [4], but in this work reactive co-sputtering is performed to deposit BCN thin films. The co-sputtering helps in the creation of films which gives more freedom to vary the composition when compared to single target sputtering. Thickness uniformity and the film quality are better when using co-sputtering.

In this work, we are depositing BCN thin films on oxidized silicon wafer substrates using two targets namely B₄C and BN using RF power and DC power respectively at different N₂/Ar gas flow ratios. A thin film of titanium (Ti) was deposited on it and another layer of Aluminum was deposited on top of the titanium layer to form a metal/insulator/semiconductor (MIS) device. This titanium layer acts as the barrier layer against the aluminum migration into BCN at higher temperatures during annealing. The dielectric constant value was found from capacitance-voltage (C-V) characteristics.

REFERENCES

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[2] A. Perrone, A.P. Caricato, A. Luches, M. Dinescu, C. Ghica, V. Sandu, A.Andrei , Appl. Surf. Sci., 133 (1998), p. 239

 [3] T.Sugino, Y. Etou, T. Tai, Jpn. and H. Mori, Appl. Phys. Lett. 80, 649 (2002)

 [4] J. Yu and E. G. Wang, Appl. Phys. Lett. 74, 2848 (1999)