1. Introduction

\$!z#.!0z !2!(+,)!\*0z+"z0\$%\*z"%()z#.+30\$z0!\$\*%-1!/z\$/z/0%)1(0! z0\$!z%\* 1/0.%(z\* z¥ !)%z.!/!.\$!/z+10z !/%#\*\_z".%0%+\*z\* z0!/0z+"z0\$%\*z"%()z/! z !2%!/^z\$!z.!,(!¥ ment of the conventional bulk materials by thin films allows the fabrication of devices with smaller volume and weight, higher flexibility besides lower cost and good performance. It has been shown that the efficiency of thin film based devices is strongly dependent on their structural, electrical, mechanical and optical properties (Fraga, 2011a; Fraga 2012). At the /)!z0%)!z0\$0z0\$!.!z%/zz0.!\* z%\*z0\$!z)%\*%01.%60%+\*z+"z!(!0.+\*%z\* z!(!0.+)!\$\*%(z !¥ vices, there is also a considerable interest in the study of wide bandgap materials to replace the silicon as base material in these devices for harsh applications such as high temperatures and high levels of radiation (Fraga, 2012, Yeung, 2007).

%(%+\*z.% !zc%dz\$/z%\*0.%\*/%z,.+,!.0%!/z0\$0z)'!z%0zz)0!.%(z+"z#.!0z%\*0!.!/0z"+.z)%¥ croelectronic and MEMS (Micro-Electro-Mechanical Systems) applications. In the last years, 0\$!.!z \$/z !!\*z )1\$z !0!z %\*z 0\$!z (%0!.01.!z +10z \$+3z 0\$!z %\*+.,+.0%+\*z +"z +,\*0z !(!¥ ments (such as nitrogen, oxygen, aluminum, boron, phosphorus, etc.) during the growth of SiC thin films by chemical vapor deposition (CVD) or physical vapor deposition (PVD) processes affects their properties. It has been noticed that the dopant incorporation allows controlling thin film properties such as optical bandgap and electrical conductivity, which are quite attractive because make possible to obtain semiconductor or insulator SiC-based films (Alizadeh, 2002; Medeiros, 2011).

© 2013 Fraga et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Fraga et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

In general, the use of amorphous SiC films has been preferred due to relatively their low growth temperature, which guarantees a larger compatibility with silicon-based technology (Hatalis, 1987).

In situ doping of amorphous and crystalline SiC films is well-documented in the literature. Historically, the first papers on the electrical properties of a-SiC films were published during 0\$!zJCj/^z \*zDLJJ\_z\* !./+\*z\* z,!.z%\*2!/0%#0! z0\$!z!(!0.%(z,.+,!.0%!/z+"z,(/)z!\*¥ hanced chemical vapor deposition (PECVD) hydrogenated amorphous SiC (a-SiC:H) films. In the 80's, several papers on doping of a-SiC and a-SiC:H films and their potential applications were published (Tawada, 1982; Beyer 1985; Pereira 1985). Since then, numerous studies have demonstrated the great potential of the SiC-based thin films for electronic device applications.

Applications of SiC-Based Thin Films in Electronic and MEMS Devices

http://dx.doi.org/10.5772/50998

315

)+\*#z 0\$!z %""!.!\*0z%w/! z "%()/\_z 0\$!z/%(%+\*z.+\*%0.% !z c%dz\$/z!!\*z 0\$!z)+/0z%\*¥ 2!/0%#0! z 1!z0+z%0/z!/5z/5\*0\$!/%/^z!\*!.((5\_z%z"%()/z.!z,.+ 1! z5z%\*0.+ 1%\*#z\*%¥ trogen gas (N2) during SiC film growth by CVD and PVD processes. The use of N2 as doping gas is advantageous due to non-toxicity, low cost and high efficiency (Fraga, 2008d^z\$!z+\*¥ trol of N2 gas flow during deposition process has been shown as a convenient and effective 35z0+z\$\*#!z0\$!z!(!0.%(z,.+,!.0%!/z+"z%z"%()/z%\*z+. !.z0+z+0%\*z"%()/z3%0\$z !/%.! z!(!¥ trical conductivities for each application type. According to Alizadeh and Sundaram, for N2/Ar ratios from 0.2 to 0.4, the N2 gas acts like a dopant in a-SiC films prepared onto glass substrate by radiofrequency (RF) magnetron sputtering of a SiC target in N2/Ar atmosphere, reducing their electrical resistivities from the range of 109 .cm to 104 .cm. However, for N2/Ar ratios between 0.6 and 0.8 the film resistivity reach values in the range of 1010 ^)\_ indicating the formation of insulator SiCN films. Other important correlations between N2/Ar ratio and the properties of a-SiCN films were shown in their previous work: the bandgap and the percentage of optical transmission of these films increase with the N2/Ar ratio increases. The electrical conductivity of sputtered a-SiCN films was also studied by Wu !0z (^z3\$!.!\_z%\*z 0\$%/z3+.'\_z 0\$!z w%z "%()/z3!.!z !,+/%0! z +\*0+z -1.06\_z #(//z \* z %z /1¥ strates at room temperature by RF reactive sputtering of a SiC target in Ar/N2/H2/CH4 0¥ mosphere. They observed that the dark conductivity decreases with increases in N2 flow rate. Besides sputtering, other processes are being used to grown a-SiCN films. Gomez et al. used the electron cyclotron resonance (ECR) PECVD to prepare a-SiCN films using nitrogen, )!0\$\*!\_z\* z.#+\*z %(10! z/%(\*!z/z,.!1./+.z#/!/^z))+0+z!0z(^z%\*2!/0%#0! z0\$!z+.¥ .!(0%+\*z!03!!\*z\*%0.+#!\*z%+\*z!\*!.#5z\* z0\$!z"+.)! z\$!)%(z+\* /z%\*zw%z"%()/z !,+/¥ ited on (100) Si substrates by nitrogen ion-assisted pulsed-laser ablation of a SiC target.

 \*z/%01z\*%0.+#!\*z +,%\*#z+"z.5/0((%\*!z%z"%()/z\$2!z(/+z!!\*z+))+\*(5z.!,+.0! ^z%&!/1\*¥ dara et al. investigated the nitrogen doping of polycrystalline 3C-SiC films grown on (100) Si substrates by LPCVD at various growth temperatures 650–850ºC using 1,3-disilabutane and NH3 as precursors. They concluded that the electrical resistivity of the polycrystalline lms

3C-SiC lms exhibit lower resistivities (around 0.02 .cm) than the undoped (around 10

properties of nitrogen-doped 3C-SiC thin lms, grown on Si3N4/p-Si (111) substrates by LPCVD at temperature 1100-1250ºC using organosilane-precursor trimethylsilane ((CH3)3%d\_z3!.!z %/1//! z5z\$!\*#z!0z(^z 0z3/z+/!.2! z0\$0z%\* !,!\* !\*0z+"z0\$!z0!),!.¥

ow rate in the reactor and that nitrogen-doped

ow rate and growth temperature on the electrical

is further controlled by adjusting the NH3 -

^)dz+0%\*! z0zKCCB^z\$!z!""!0/z+"z<sup>2</sup> -

*2.1.1. Nitrogen incorporation*

Nowadays, SiC-based thin films, such as SiCN, SiCO, SiCNO, SiCB, SiCBN and SiCP, have been extensively used in electronic and MEMS devices either as a semiconductor or as an insulator, depending on the film composition. These films have been shown promising for applications in diodes, thin-film transistors (TFTs) and MEMS devices (Yih, 1994; Patil, 2003; Hwang, 1995; Fraga, 2011c).

The goal of this chapter is to discuss the role of in situ incorporation of nitrogen, oxygen, aluminum, boron, phosphorus and argon on the properties of SiC films. Special attention is given to the low temperature SiC growth processes. An overview on the applications of SiC- /! z0\$%\*z"%()/z%\*z!(!0.+\*%z\* z

z !2%!/z%/z,.!/!\*0! z\* z %/1//! ^z1.z.!!\*0z.!¥ searches on heterojunction diodes and MEMS sensors are emphasized.
