Preface

As is well known, silicon carbide (SiC) is an attractive material for power device applications owing to its physical properties. Also these properties enable us to realize electronic devices or MEMS that operate in extremely severe circumstances such as high temperature or high radiation field, so-called 'hard electronics' devices. Furthermore, SiC has an advantageous chemical nature for device applications that a SiO2 film can be grown on the surface by thermally oxidation like Si, which cannot be obtained with other wide bandgap semiconducting materials.

Recently, some SiC power devices such as Schottky-barrier diodes (SBDs), metal-oxidesemiconductor field-effect-transistors (MOSFETs), junction FETs (JFETs) have come onto the market. However, technological improvements for material characterizations and fundamental device processing are still needed for the stable supply (i.e. mass products) of these devices or their cost-down. This book abundantly describes the essences of SiC devices, by SiC devices, and for SiC devices. I hope that this book would be placed in an obscure corner of an improving site of some SiC device.

I would like to thank all the authors who contributed to this article. Especially, I deeply acknowledge some of the authors who accepted my offer despite being very busy. Ms. Viktorija Zgela, Ms. Maja Bozicevic, and Ms. Danijela Duric, the publishing process managers, made much effort for this work. They contacted with all the authors, kept them confortable in the publishing process and sometimes encouraged them to compose their chapter. I would like to also acknowledge Dr. Sadafumi Yoshida, Ex-Professor of Saitama University, who gave me a lot of valuable advices. Finally, I thank my wife, Megumi Hijikata, who always supports me through my life.

Yasuto Hijikata

Division of Mathematics, Electronics and Informatics, Graduate School of Science and Engineering, Saitama University, Japan

Section 1

Characterization for Device Application

Characterization for Device Application

Chapter 1

Nondestructive and Contactless Characterization

Method for Spatial Mapping of the Thickness and

Electrical Properties in Homo-Epitaxially Grown SiC

Epilayers Using Infrared Reflectance Spectroscopy

%(%+\*z.% !zc%dz%/z+\*!z+"z0\$!z)+/0z,.+)%/%\*#z/!)%+\* 10%\*#z)0!.%(/z"+.z0\$!z".%¥ tion of high power electronic devices with extremely low loss, owing to its excellent physical properties, such as high breakdown electric field, high saturation electron drift velocity, and high thermal conductivity. Nowadays, some kinds of devices, such as SBDs, JFETs and MOSFETs have been on the market. For the fabrication of SiC devices with high yield rates, *i.e*., for reducing the scattering of device specification, the production of high-quality, large- %)!0!.z!,%w3"!./z3%0\$z1\*%"+.)z0\$%'\*!//z\* z!(!0.%(z,.+,!.0%!/z%/z%\* %/,!\*/(!^z \*z+.¥ der to characterize the electrical and thickness uniformity of the epi-wafers during the device process, *i.e*^\_z 0+z'\*+3z\$+3z 0\$!z 0\$%'\*!//\_z +,%\*#z+\*!\*0.0%+\*z\* z)+%(%05z.!z %/¥ tributed over the SiC epi-layers, it is necessary to develop the characterization method that can perform the determinations of thickness and electrical properties simultaneously in a

To characterize the distribution of the electrical properties over SiC wafers and homo-epiwafers, conductivity mapping is often performed [1]. However, the distribution of carrier +\*!\*0.0%+\*z\* z)+%(%05z\*\*+0z,.+2% !z".+)z0\$!z+\* 10%2%05z),,%\*#\_z!1/!z0\$!z+\*¥ ductivity depends both on the distribution of dopant concentration and the crystallinity \* u+.z %/0.%10%+\*z+"z.5/0(z !"!0/^z \*z+. !.z0+z\$.0!.%6!z0\$!z %/0.%10%+\*z+"z..%!.z+\*¥ !\*0.0%+\*z\* z)+%(%05z+2!.z!,%w(5!./\_z!(!0.%(z)!/1.!)!\*0z 0!\$\*%-1!/z/1\$z/z((z!"¥

> © 2013 Yoshida 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 Yoshida 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.

Sadafumi Yoshida, Yasuto Hijikata and

Additional information is available at the end of the chapter

Hiroyuki Yaguchi

1. Introduction

http://dx.doi.org/10.5772/50749

nondestructive and noncontact way.

Nondestructive and Contactless Characterization Method for Spatial Mapping of the Thickness and Electrical Properties in Homo-Epitaxially Grown SiC Epilayers Using Infrared Reflectance Spectroscopy

Sadafumi Yoshida, Yasuto Hijikata and Hiroyuki Yaguchi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/50749

1. Introduction

%(%+\*z.% !zc%dz%/z+\*!z+"z0\$!z)+/0z,.+)%/%\*#z/!)%+\* 10%\*#z)0!.%(/z"+.z0\$!z".%¥ tion of high power electronic devices with extremely low loss, owing to its excellent physical properties, such as high breakdown electric field, high saturation electron drift velocity, and high thermal conductivity. Nowadays, some kinds of devices, such as SBDs, JFETs and MOSFETs have been on the market. For the fabrication of SiC devices with high yield rates, *i.e*., for reducing the scattering of device specification, the production of high-quality, large- %)!0!.z!,%w3"!./z3%0\$z1\*%"+.)z0\$%'\*!//z\* z!(!0.%(z,.+,!.0%!/z%/z%\* %/,!\*/(!^z \*z+.¥ der to characterize the electrical and thickness uniformity of the epi-wafers during the device process, *i.e*^\_z 0+z'\*+3z\$+3z 0\$!z 0\$%'\*!//\_z +,%\*#z+\*!\*0.0%+\*z\* z)+%(%05z.!z %/¥ tributed over the SiC epi-layers, it is necessary to develop the characterization method that can perform the determinations of thickness and electrical properties simultaneously in a nondestructive and noncontact way.

To characterize the distribution of the electrical properties over SiC wafers and homo-epiwafers, conductivity mapping is often performed [1]. However, the distribution of carrier +\*!\*0.0%+\*z\* z)+%(%05z\*\*+0z,.+2% !z".+)z0\$!z+\* 10%2%05z),,%\*#\_z!1/!z0\$!z+\*¥ ductivity depends both on the distribution of dopant concentration and the crystallinity \* u+.z %/0.%10%+\*z+"z.5/0(z !"!0/^z \*z+. !.z0+z\$.0!.%6!z0\$!z %/0.%10%+\*z+"z..%!.z+\*¥ !\*0.0%+\*z\* z)+%(%05z+2!.z!,%w(5!./\_z!(!0.%(z)!/1.!)!\*0z 0!\$\*%-1!/z/1\$z/z((z!"¥

© 2013 Yoshida 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 Yoshida 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.

fect measurements and capacitance-voltage (*C–V*) measurements have been widely used. These techniques, however, are disadvantageous as a device fabrication process monitoring tool because they require the formation of electrodes on a sample. By using a mercury probe as an electrode, *C–V* measurements can be performed without the formation of electrodes on a sample. However, the problems caused by the contamination with mercury contact have been pointed out, recently.

cal dielectric function (MDF) model taking into account the contribution of the TO phonon damping constant and the LO phonon damping constant independently [17]. Considering

Nondestructive and Contactless Characterization Method for Spatial Mapping of the Thickness and Electrical

<sup>q</sup>*<sup>T</sup>* <sup>2</sup> <sup>q</sup> <sup>2</sup> *i*\*<sup>T</sup>* <sup>q</sup> <sup>q</sup>*<sup>p</sup>*

where cX is the high frequency dielectric constant, qT and qL are the TO- and LO-phonon

tively, a<sup>p</sup> is the free-carrier damping constant, and q<sup>p</sup> %/z0\$!z,(/)z".!-1!\*5z+"z0\$!z".!!z.¥

where *N*, *e*, and *m*tz.!z0\$!z".!!z..%!.z+\*!\*0.0%+\*\_z!(!0.+\*z\$.#!\_z\* z!""!0%2!z)//\_z.!¥ spectively. The free-carrier damping constant p is the inverse of the scattering time m and

//1)%\*#z 0\$0z 0\$!z3"!./z .!z 1\*%"+.)! z%\*z 0\$!z !,0\$z %.!0%+\*\_z3!z 1/! z 0\$!z \*+.)(w%\*%¥

\$!z..%!.z+\*!\*0.0%+\*z\* z)+%(%05z\*z!z !0!.)%\*! z5z"%00%\*#z0\$!z!4,!.%)!\*0(z%\*".¥ red reflectance spectrum with calculated ones. To fit the spectra, we used the least-squares method based on eqs. (1) and (4), where we adopted qp, ap, and \L as adjustable parameters.

Single crystal wafers of commercially produced *n*-type (nitrogen doped) 6H-SiC were used. z .!"(!0\*!z /,!0.z 3!.!z )!/1.! z 1/%\*#z 03+z +1.%!.w0.\*/"+.)z %\*"..! z c dz /,!¥ trometers, JASCO FT/IR–VM7 for the far-infrared region (30–600 cm–1) and JASCO FT/IR 670-PLUS for the middle-infrared region (400–2000 cm–1d\_z .!/,!0%2!(5^z +.z ".w%\*"..! z .!¥ flectance measurements, two light sources (a mercury arc-lamp and nichrome light source),

2.2. Measurements of IR reflectance spectra of SiC wafers and estimation of electrical

<sup>2</sup> + *k* <sup>2</sup>

<sup>q</sup>*<sup>p</sup>* <sup>=</sup> *<sup>N</sup> <sup>e</sup>* <sup>2</sup> *m* \* c

therefore the free-carrier mobility can be derived using the following relation,

dence reflectance of a semi-infinite medium *R*, which is expressed as

where *n* and *k* are the optical constants, derived from cSc0=(*n*–*ik*)

*<sup>µ</sup>* <sup>=</sup> *<sup>e</sup> m* \* a*<sup>p</sup>*

*<sup>R</sup>*(q)= (*<sup>n</sup>* 1)

(*n* + 1)

2

Properties in Homo-Epitaxially Grown SiC Epilayers Using Infrared Reflectance Spectroscopy

z.!z0\$!zwz\* zw,\$+\*+\*z ),%\*#z+\*/0\*0/\_z.!/,!¥

<sup>q</sup> <sup>2</sup> <sup>+</sup> *<sup>i</sup>*a*p*<sup>q</sup> ) (1)

http://dx.doi.org/10.5772/50749

<sup>2</sup> <sup>+</sup> *<sup>k</sup>* <sup>2</sup> (4)

2 . (2)

5

(3)

the contributions from phonons and plasmons, the dielectric constant is given as

<sup>c</sup>(q)=c( <sup>q</sup>*<sup>L</sup>* <sup>2</sup> <sup>q</sup> <sup>2</sup> *i*\*<sup>L</sup>* <sup>q</sup>

frequencies, respectively, \T and \<sup>l</sup>

riers, which is given by

properties [12]

Optical measurement techniques such as Raman scattering spectroscopy [2-5], infrared (IR) /,!0.+/+,%z!((%,/+)!0.5zeIf\_z+,0%(z/+.,0%+\*z)!/1.!)!\*0/zeJfz\$2!z!!\*z1/! z0+z!/0%¥ mate the carrier concentration in SiC wafers as a nondestructive and contactless method. IR reflectance measurements have been used to estimate the electrical properties of GaAs [8] and SiC [9]. Macmillan *et al*^zeDCfz.!,+.0! z0\$0z0\$!z0\$%'\*!//z+"z\$+)+w!,%04%((5z#.+3\*z%z3¥ fers can be estimated from the interference oscillations in IR reflectance spectra observed both below and upper frequency ranges of the reststrahlen band (800–1000cm–1z"+.z%d^z+3¥ days, the reflectance measurements in near IR spectral range (1000–4000cm–1) is widely used to estimate the thickness of homo-epitaxially grown SiC layers in the SiC device process. As the thickness of epilayers used for power devices are in the range from several to several tens µm, the observation of reflectance spectra in near IR spectral range is suitable to analyze the oscillation of reflectance caused by the interference effects of light in the epilayers.

!z\$2!z !2!(+,! z0\$!z)!0\$+ z+"z+0%\*%\*#z0\$!z0\$%'\*!//z\* z!(!0.%(z,.+,!.0%!/z+"z/!)%¥ conductor wafers and epi-wafers, simultaneously, by using IR reflectance spectroscopy [11-15]. In this paper, we will summarize the development of the method, and will discuss the validity of the electrical properties derived from the IR reflectance by comparing with those estimated from Hall effect and *C–V* measurements. Finally, we will show the results of applying this method to characterize the electrical activation of impurity and crystalline damages in the ion-implanted, and post-implantation-annealed SiC epilayers.
