Boron Doping in Hot Filament MCD and NCD Diamond Films
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1203-J12-01
Boron Doping in Hot Filament MCD and NCD Diamond Films Jerry Zimmer1, Thomas Hantschel2, Gerry Chandler1, Wilfried Vandervorst2,3, Maria Peralta1 1 sp3 Diamond Technologies, 2220 Martin Ave., Santa Clara, CA 95050, U.S.A. 2 IMEC, Kapeldreef 75, B-3001, Leuven, Belgium 3 Instituut voor Kern- en Stralingsfysica, K. U. Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium ABSTRACT Conductive diamond films are essential for electronic applications of diamond but there is still a poor understanding of the effects that growth conditions, grain size and film thickness have on the ultimate conductivity of the film. One of the unique advantages of hot filament diamond is the ability to grow both MCD and NCD films to moderate thicknesses over large areas with little or no change in morphological characteristics such as grain size. In addition the grain size of the film can be altered without the necessity of adding additional gases to the process or unduly increasing the carbon to hydrogen ratio. This gives us an opportunity to investigate electrical conductivity as a function of grain size and thickness within a simple methane, hydrogen, and boron chemical environment over areas which are large enough to support significant production levels of MEMS and other diamond based electronics. In this study the boron source was selected to be trimethyl boron gas to avoid any source of oxygen which could alter the growth conditions and to guarantee that any byproducts of the dopant would be primarily methyl based. The films were grown to various thicknesses up to 5 µm and grain sizes from NCD to full MCD at all thicknesses. This paper explores the effects of both grain size and film thickness on the electrical conductivity of the film as well as the absolute doping levels within the film.
INTRODUCTION Boron doped diamond grown in microwave plasma deposition systems has been extensively investigated but little has been written about doped diamond grown in hot filament deposition systems. The increasing use of conductive diamond in electrode and microelectromechanical (MEMS) applications makes it imperative that the entire parameter space of doped diamond be understood to allow volume production of these films with acceptable manufacturing control. May et al. [1] have investigated Raman characteristics of both microcrystalline (MCD) and nanocrystalline (NCD) doped diamond films from hot filament reactors but no one has yet explored the characteristics of films which include the transition region between traditional MCD and NCD regions where average grain size is much smaller than MCD films for a given thickness but the grain size has not yet reached the 100 nm boundary which defines traditional NCD films. The other reason to examine these films is to determine if they are still columnar or are transitioning to a stacked grain structure. Also, minimal work has been done to characterize the full range of dopant levels in all grain size regions. This paper will quantify some of the characteristics in both the MCD region and t
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