4. Characterization of electrical properties and residual crystalline damage in ion-implanted and post-implantation-annealed 4H-SiC epilayers using IR reflectance spectroscopy

#### 4.1. Method of obtaining the electrical properties and crystalline damage in ionimplanted SiC epilayers [15]

Ion implantation is an indispensable process for selective area doping into crystalline silicon carbide (SiC), because the doping of impurities by thermal diffusion is hard to apply for SiC !2%!z,.+!//z 1!z 0+z2!.5z /)((z %""1/%+\*z+\*/0\*0z+"z%),1.%0%!/z%\*z %^z"0!.z 0\$!z%+\*z%)¥ ,(\*00%+\*\_z\*\*!(%\*#z0z\$%#\$z0!),!.01.!/z%/z\*!!//.5z"+.z0%20%\*#z0\$!z +,\*0/z!(!0.%(¥ ly as well as recovering the crystallinity of SiC damaged by ion implantation. Hall effect )!/1.!)!\*0/\_z /!+\* .5z%+\*z)//z /,!0.+/+,5z c 
dz \* z 0.\*/)%//%+\*z !(!0.+\*z)%.+¥ scopy (TEM) have been widely used to characterize the electrical properties, depth profile of the impurities and crystalline damage of implanted layers, respectively. These techniques are, however, inappropriate to use as device process monitoring tools because Hall effect measurement requires the formation of electric contacts, and SIMS and TEM observations .!/1(0z%\*z0\$!z !/0.10%+\*z+"z0\$!z/),(!/^z!!\*0(5\_z0\$!z/\$+.0z,!.%+ z\* z\$%#\$z0!),!.01.!z\*¥ nealing is used in SiC device process [35f^z+z)'!z(!.z0\$!z!""!0z+"z/\$+.0z,!.%+ z\$%#\$w0!)¥ perature annealing, we investigated the annealing period dependence at the annealing temperature of 1700°C.

!!\*0(5\_z%0z\$/z!!\*z .!,+.0! z 0\$0z 0\$!z.5/0((%\*!z )#!z%\* 1! z5z%+\*z%),(\*00%+\*z "¥ fects the infrared (IR) reflectance spectra around the reststrahlen region (~800–1000 cm–1) [33,34f\_z\* z0\$!z %""!.!\*!z+"z..%!.z+\*!\*0.0%+\*z!03!!\*z!,%04%(z(5!.z\* z/1/0.0!z%\*¥ duces the interference oscillation in the near IR region (1000–4500 cm–1). In this study, we performed the IR reflectance measurements in the spectral range between 600 and 8000 cm–1 for high-dose phosphorus ion implanted and post-implantation-annealed 4H-SiC wafers to characterize both the electrical properties and crystalline damage of the implanted layers without destruction and contactless.

Nondestructive and Contactless Characterization Method for Spatial Mapping of the Thickness and Electrical Properties in Homo-Epitaxially Grown SiC Epilayers Using Infrared Reflectance Spectroscopy http://dx.doi.org/10.5772/50749 19

reflectance spectra are in fairly good agreement with solid line, suggesting that the values of the carrier concentrations estimated from IR reflectance spectra have a sufficient validity. However, a careful look confirms that the values of carrier concentration derived from the .!"(!0\*!z)!/1.!)!\*0/z.!z/(%#\$0(5z(+3!.z 0\$\*z 0\$+/!z!/0%)0! z ".+)z 0\$!z!(!0.%(z)!/¥ urements as in the case of carrier concentrations higher than 1017cm–3. The same tendency was observed in the comparisons with the Hall effect measurements for the samples of *n*type epilayers on *p*-type substrates as shown in Figure 8. This tendency is considered to be partly because of the adoption of inappropriate effective mass values for the calculation of reflectance spectra. It is also considered as a cause that the part of free carriers trapped in the !"!0/z+.z+1\* ! z5z +,\*0/z\*\*+0z "+((+3z%\*z 0\$!z6z ".!-1!\*5z .\*#!z1/! z "+.z 0\$!z .!¥

4. Characterization of electrical properties and residual crystalline damage in ion-implanted and post-implantation-annealed 4H-SiC

4.1. Method of obtaining the electrical properties and crystalline damage in ion-

Ion implantation is an indispensable process for selective area doping into crystalline silicon carbide (SiC), because the doping of impurities by thermal diffusion is hard to apply for SiC !2%!z,.+!//z 1!z 0+z2!.5z /)((z %""1/%+\*z+\*/0\*0z+"z%),1.%0%!/z%\*z %^z"0!.z 0\$!z%+\*z%)¥ ,(\*00%+\*\_z\*\*!(%\*#z0z\$%#\$z0!),!.01.!/z%/z\*!!//.5z"+.z0%20%\*#z0\$!z +,\*0/z!(!0.%(¥ ly as well as recovering the crystallinity of SiC damaged by ion implantation. Hall effect )!/1.!)!\*0/\_z /!+\* .5z%+\*z)//z /,!0.+/+,5z c 
dz \* z 0.\*/)%//%+\*z !(!0.+\*z)%.+¥ scopy (TEM) have been widely used to characterize the electrical properties, depth profile of the impurities and crystalline damage of implanted layers, respectively. These techniques are, however, inappropriate to use as device process monitoring tools because Hall effect measurement requires the formation of electric contacts, and SIMS and TEM observations .!/1(0z%\*z0\$!z !/0.10%+\*z+"z0\$!z/),(!/^z!!\*0(5\_z0\$!z/\$+.0z,!.%+ z\* z\$%#\$z0!),!.01.!z\*¥ nealing is used in SiC device process [35f^z+z)'!z(!.z0\$!z!""!0z+"z/\$+.0z,!.%+ z\$%#\$w0!)¥ perature annealing, we investigated the annealing period dependence at the annealing

!!\*0(5\_z%0z\$/z!!\*z .!,+.0! z 0\$0z 0\$!z.5/0((%\*!z )#!z%\* 1! z5z%+\*z%),(\*00%+\*z "¥ fects the infrared (IR) reflectance spectra around the reststrahlen region (~800–1000 cm–1) [33,34f\_z\* z0\$!z %""!.!\*!z+"z..%!.z+\*!\*0.0%+\*z!03!!\*z!,%04%(z(5!.z\* z/1/0.0!z%\*¥ duces the interference oscillation in the near IR region (1000–4500 cm–1). In this study, we performed the IR reflectance measurements in the spectral range between 600 and 8000 cm–1 for high-dose phosphorus ion implanted and post-implantation-annealed 4H-SiC wafers to characterize both the electrical properties and crystalline damage of the implanted layers

flectance measurements, as mentioned above.

18 Physics and Technology of Silicon Carbide Devices

implanted SiC epilayers [15]

temperature of 1700°C.

without destruction and contactless.

epilayers using IR reflectance spectroscopy

Figure 13. The carrier concentration estimated from the reflectance spectra for an *n*-type epilayer on an *n*LQH=KM:s strate as a function of doping concentration obtained from *C–V*E=9KMJ=E=FLK>GJ=9;@K9EHD=0@=KGDA<DAF=J=HJ=s sents the theoretical carrier concentration for *T*=300K assuming zero doping concentration (*N*A=0) using eq. (6). The dotted line represents *N*FTIR=*N*D–*N*A as a guide to the eye [14].

#### 4.2. High-dose phosphorus ion implantation, post-implantation annealing and IR reflectance measurements [15]

The samples used in this study were 4H-SiC (0001) substrates with *p*-type ~5 µ)z0\$%'z+)¥ mercially produced epitaxial layers. The multi-energy implantations of phosphorus ions at 500°C were carried out through the 10 nm thick oxide film in six steps (40–250 keV) in order to form a box-shaped profile with a thickness of 0.3 µm. The total implanted dose was 7×1015 cm–2. After removing the oxide film by HF, the post implantation annealing was conducted %\*z .z 0)+/,\$!.!^z +z%\*2!/0%#0!z 0\$!z \*\*!(%\*#z 0!),!.01.!z !,!\* !\*!z +"z .5/0((%\*!z .!¥ covery and electrical properties in the implanted layers, the samples were annealed for 30 )%\*z0z %""!.!\*0z0!),!.01.!/z+"zDECC[\_zDFCC[\_z\* zDGCC[^z \*z %0%+\*\_z0+z,,(5z0\$!z z.!¥ flectance analysis to the short-period high-temperature annealing process, we also carried out the post implantation annealing at 1700°C for various periods between 0.5 and 10 min. z .!"(!0\*!z)!/1.!)!\*0/z3!.!z..%! z+10z 0z .++)z 0!),!.01.!z+\*z\*!.(5z\*+.)(z%\*%¥ !\*!z1/%\*#zz)%.+zw z/,!0.+)!0!.zc(%#\$0z!)z %)!0!.z3/zC^Dz))d^z\$!z/,!0.(z.!/¥ olution and range were 4 cm–1 and 600–8000 cm–1, respectively.

#### 4.3. Analysis of carrier concentration, mobility and crystalline damage from IR reflectance spectra [15]

Figure 14 shows the annealing temperature dependence of IR reflectance spectrum. For as- %),(\*0! z /),(!/\_z 0\$!z .!"(!0%2%05z )4%)1)z \* z 0\$!z /\$,!z %\*z 0\$!z .!/0/0.\$(!\*z \* z !¥ creases and becomes blunt, respectively, as compared to those of unimplanted samples. "0!.z0\$!z\$%#\$z0!),!.01.!z\*\*!(%\*#\_z0\$!z.!"(!0%2%05z)4%)1)z%\*z0\$!z.!/0/0.\$(!\*z\* z.!¥ +2!./z0+z0\$0z+"z1\*%),(\*0! z/),(!/^z\$%/z%/z.!/1(0! z".+)z0\$!z.5/0((%\*!z.!+2!.5z%\*z%)¥ planted layer. In the spectral range above ~2000 cm–1, the evident interference oscillation is observed. It indicates that the implanted dopants are activated and the refractive index of an implanted layer is changed by the change of carrier concentration. We can see the tendencies that the reflectance around 1000 cm–1 !+)!/z(.#!.z3%0\$z%\*.!/%\*#z0\$!z\*\*!(%\*#z0!),!.¥ 01.!^z!z\*(56! z0\$!z+/!.2! z/,!0.z0+z!2(10!z0\$!z )#!z+"z0\$!z%+\*z%),(\*00%+\*z(5¥ ers assuming that the implanted layers are composed of two phases, recrystallized SiC phase and defective SiC phase. We have derived the effective dielectric constants c*eff*z+"z%)¥ planted layers using an effective medium approximation (EMA) [33],

$$0 = (1 - f)\frac{\varepsilon\_c - \varepsilon\_{eff}}{\varepsilon\_c + \mathfrak{L}\varepsilon\_{eff}} + f\frac{\varepsilon\_d - \varepsilon\_{eff}}{\varepsilon\_d + \mathfrak{L}\varepsilon\_{eff}} \tag{8}$$

2000 4000 6000 8000

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

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

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

21

Wavenumber (cm-1)

Figure 16. +:K=JN=<<GLL=<DAF=9F<>ALL=<%.J=>D=;L9F;=KH=;LJ9KGDA<DAF=>GJL@=K9EHD=K9FF=9D=<9Lt>GJ

where cc and cdz.!z 0\$!z %!(!0.%z+\*/0\*0/z+"z.!w.5/0((%6! z\* z )#! z,\$/!/\_z.!/,!¥ tively, and *f*z%/z 0\$!z2+(1)!z ".0%+\*z+"z )#! z,\$/!^z!z//1)! z 0\$0z 0\$!z ".!-1!\*5z !¥ pendence of both the dielectric constants of re-crystallized phase and defective phase follows the MDF model given by eq.(1)^z!"!..%\*#z0+z0\$!z.!/1(0z+"z
z+/!.20%+\*/\_z3!z!)¥ ,(+5! z0\$!z/0.101.(z)+ !(z0\$0z0\$!z%+\*z%),(\*0! z(5!.z%/z+),+/! z+"zFz(5!./`z\*z1\* )¥ aged surface layer, a carrier-concentration- plateau layer, and a graded-carrier-concentration layer as shown in Figure 15. Furthermore, we assumed that the volume fraction of defective ,\$/!z%\*zz#. ! w..%!.w+\*!\*0.0%+\*z(5!.z%/z/)!z/z 0\$0z%\*zz..%!.w+\*!\*0.0%+\*w,(¥ 0!1z(5!.^z+.zz#. ! w..%!.wz+\*!\*0.0%+\*z(5!.\_z3!z1/! z 0\$!z)1(0%w(5!.z/0.101.!z,¥ proximation assuming that the free carrier concentration decreases exponentially with depth

4.4. Annealing temperature dependences of electrical activity and re-crystallization [15]

As an example of curve fitting analysis, the spectrum of the sample annealed at 1400°C for 30 min and the fitted curve are show in Figure 16^z!z+0%\*! zz#++ z"%0z%\*z0\$!z3\$+(!z/,!¥ tral region measured. The best-fit parameters derived are also described in the figure. Figure 17 (a) shows the annealing temperature dependence of the volume fraction of the defective

.!/!/z".+)zLEzMzc/z%),(\*0! dz0+zE^LzMzcDECC[z\*\*!(! d\_z\* z !.!/!/zz(%00(!z3%0\$z%\*¥ creasing of annealing temperature up to 1400°C. Figure 17 (b) shows the annealing 0!),!.01.!z !,!\* !\*!z+"z0\$!z..%!.z+\*!\*0.0%+\*zc+,!\*z%.(!dz\* z0\$!z)+%(%05zc+,!\*z0.%¥ angle) in the re-crystallized phase. For comparison, the electrical properties derived from Hall effect measurements [35] are also plotted in the figure (filled symbols). We can see a good agreement in the electrical characteristics between IR reflectance spectroscopy and ((z!""!0z)!/1.!)!\*0/^z\$!z".!!z..%!.z+\*!\*0.0%+\*/z.!z()+/0z+\*/0\*0z%\*z0\$!z0!),!.¥ ature range studied, as in the case of the volume fraction of defective phase. In contrast, the carrier mobility becomes large with increasing the annealing temperature. These results show that the post implantation annealing at a temperature as low as 1200°C reduces the volume fraction of defective SiC drastically and put the impurities in substitutional lattice

5z,+/0z%),(\*00%+\*z\*\*!(%\*#\_z 0\$!z2+(1)!z ".0%+\*z+"z !"!0%2!z%z ./0%((5z !¥

and the mobility changes in inverse proportion to carrier concentration.

Reflectance (

30 min. The best fit parameters are described in the figure [15].

,\$/!^z-

!)

100

Figure 14. The IR reflectance spectra obtained from the 4H-SiC wafers high-dose implanted and post implantation annealed for 30 minutes [15].

Figure 15. The structural model of the ion implanted SiC wafers used in the calculation of reflectance spectra [15].

Nondestructive and Contactless Characterization Method for Spatial Mapping of the Thickness and Electrical Properties in Homo-Epitaxially Grown SiC Epilayers Using Infrared Reflectance Spectroscopy http://dx.doi.org/10.5772/50749 21

implanted layer is changed by the change of carrier concentration. We can see the tendencies that the reflectance around 1000 cm–1 !+)!/z(.#!.z3%0\$z%\*.!/%\*#z0\$!z\*\*!(%\*#z0!),!.¥ 01.!^z!z\*(56! z0\$!z+/!.2! z/,!0.z0+z!2(10!z0\$!z )#!z+"z0\$!z%+\*z%),(\*00%+\*z(5¥ ers assuming that the implanted layers are composed of two phases, recrystallized SiC phase and defective SiC phase. We have derived the effective dielectric constants c*eff*z+"z%)¥

+ *f*

c*<sup>d</sup>* c*eff* c*<sup>d</sup>* + 2c*eff*

Annealing for 30 minutes

1000 2000 3000 4000

undamaged surface layer

defective SiC phase

carrier-concentration-plateau layer

graded-carrier-concentration layer

Wavenumber (cm-1)

Figure 14. The IR reflectance spectra obtained from the 4H-SiC wafers high-dose implanted and post implantation

Figure 15. The structural model of the ion implanted SiC wafers used in the calculation of reflectance spectra [15].

(8)

planted layers using an effective medium approximation (EMA) [33],

c*<sup>c</sup>* c*eff* c*<sup>c</sup>* + 2c*eff*

0=(1 *f* )

80

100

60

40

Reflectance (

annealed for 30 minutes [15].

 *d*impla

!)

20 Physics and Technology of Silicon Carbide Devices

20

0

recrystalized SiC phase

Figure 16. +:K=JN=<<GLL=<DAF=9F<>ALL=<%.J=>D=;L9F;=KH=;LJ9KGDA<DAF=>GJL@=K9EHD=K9FF=9D=<9Lt>GJ 30 min. The best fit parameters are described in the figure [15].

where cc and cdz.!z 0\$!z %!(!0.%z+\*/0\*0/z+"z.!w.5/0((%6! z\* z )#! z,\$/!/\_z.!/,!¥ tively, and *f*z%/z 0\$!z2+(1)!z ".0%+\*z+"z )#! z,\$/!^z!z//1)! z 0\$0z 0\$!z ".!-1!\*5z !¥ pendence of both the dielectric constants of re-crystallized phase and defective phase follows the MDF model given by eq.(1)^z!"!..%\*#z0+z0\$!z.!/1(0z+"z
z+/!.20%+\*/\_z3!z!)¥ ,(+5! z0\$!z/0.101.(z)+ !(z0\$0z0\$!z%+\*z%),(\*0! z(5!.z%/z+),+/! z+"zFz(5!./`z\*z1\* )¥ aged surface layer, a carrier-concentration- plateau layer, and a graded-carrier-concentration layer as shown in Figure 15. Furthermore, we assumed that the volume fraction of defective ,\$/!z%\*zz#. ! w..%!.w+\*!\*0.0%+\*z(5!.z%/z/)!z/z 0\$0z%\*zz..%!.w+\*!\*0.0%+\*w,(¥ 0!1z(5!.^z+.zz#. ! w..%!.wz+\*!\*0.0%+\*z(5!.\_z3!z1/! z 0\$!z)1(0%w(5!.z/0.101.!z,¥ proximation assuming that the free carrier concentration decreases exponentially with depth and the mobility changes in inverse proportion to carrier concentration.

#### 4.4. Annealing temperature dependences of electrical activity and re-crystallization [15]

As an example of curve fitting analysis, the spectrum of the sample annealed at 1400°C for 30 min and the fitted curve are show in Figure 16^z!z+0%\*! zz#++ z"%0z%\*z0\$!z3\$+(!z/,!¥ tral region measured. The best-fit parameters derived are also described in the figure. Figure 17 (a) shows the annealing temperature dependence of the volume fraction of the defective ,\$/!^z-5z,+/0z%),(\*00%+\*z\*\*!(%\*#\_z 0\$!z2+(1)!z ".0%+\*z+"z !"!0%2!z%z ./0%((5z !¥ .!/!/z".+)zLEzMzc/z%),(\*0! dz0+zE^LzMzcDECC[z\*\*!(! d\_z\* z !.!/!/zz(%00(!z3%0\$z%\*¥ creasing of annealing temperature up to 1400°C. Figure 17 (b) shows the annealing 0!),!.01.!z !,!\* !\*!z+"z0\$!z..%!.z+\*!\*0.0%+\*zc+,!\*z%.(!dz\* z0\$!z)+%(%05zc+,!\*z0.%¥ angle) in the re-crystallized phase. For comparison, the electrical properties derived from Hall effect measurements [35] are also plotted in the figure (filled symbols). We can see a good agreement in the electrical characteristics between IR reflectance spectroscopy and ((z!""!0z)!/1.!)!\*0/^z\$!z".!!z..%!.z+\*!\*0.0%+\*/z.!z()+/0z+\*/0\*0z%\*z0\$!z0!),!.¥ ature range studied, as in the case of the volume fraction of defective phase. In contrast, the carrier mobility becomes large with increasing the annealing temperature. These results show that the post implantation annealing at a temperature as low as 1200°C reduces the volume fraction of defective SiC drastically and put the impurities in substitutional lattice sites, but the crystalline recovery of re-crystallized phase is insufficient. In other words, the annealing temperature higher than 1400°C is necessary for improving the mobilities, as well as for activating the impurities.

5. Conclusion

the carrier concentration and mobility in SiC wafers.

damages of ion-implanted SiC epilayers simultaneously.

!z,.+,+/! z0\$!z)!0\$+ z"+.z!/0%)0%\*#z0\$!z!(!0.%(z,.+,!.0%!/\_z/1\$z/\_z..%!.z+\*!\*0.¥ tion and mobility of semiconductor wafers using IR reflectance spectroscopy. In the method, the observed spectra are fitted with the calculated ones, and the free carrier concentration and mobility are determined from the fitted parameters. In the calculation, we used the modified dielectric function (MDF) model for the dispersion relation of dielectric constants. We demonstrated the estimations of carrier concentrations and mobilities of commercially produced 6H-SiC wafers from observed IR reflectance spectra in the frequency range of 400– 2000cm–1^z!z/\$+3! z 0\$0z 0\$!z ".!!z..%!.z+\*!\*0.0%+\*z\* z)+%(%05z+0%\*! z ".+)z z.!¥ flectance measurements agree well with the values obtained from Hall-effect measurements in the carrier concentration range of 1017~1019 cm–3, which suggests that we can estimate the carrier concentration and mobility accurately in a nondestructive and noncontact way. We !)+\*/0.0! z/,0%(z),,%\*#/z+"z..%!.z+\*!\*0.0%+\*z\* z)+%(%05z%\*zEw%\*\$zIw%z3¥ fers using this method and showed its usefulness to characterize the spatial distribution of

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

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

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

23

!40\_z3!z,,(%! z0\$%/z)!0\$+ z0+z0\$!z/%)1(0\*!+1/z !0!.)%\*0%+\*z+"z0\$!z..%!.z+\*!\*0.¥ tion, mobility and thickness of homo-epilayers, and the carrier concentration and mobility of substrates. IR reflectance spectra with the frequency range of 80–2000 cm–1 were measured for *n*-type 4H-SiC epilayers on *p*-type and *n*w05,!zGw%z/1/0.0!/z3%0\$z %""!.!\*0z..%!.z+\*¥ centrations. The obtained values of electrical properties for *n*-type epilayers on *p*w05,!z/1¥ strates were compared with the values obtained from Hall-effect measurements, and those for *n*-type epilayers on *n*-type substrates were compared with the values from *C–V*z)!/1.!¥ )!\*0/^z\$.+1#\$z0\$!/!z+),.%/+\*/\_z3!z/\$+3! z0\$0z0\$!z\$.0!.%60%+\*z)!0\$+ z1/%\*#z z.!¥ flectance measurements can determine the electrical property and the thickness of SiC homoepilayers simultaneously and accurately. We also showed that the extension of the observation frequency range to Terahertz region (down to 20cm–1) enables us to characterize the wafers

Finally, we performed the characterization of both the electrical properties and crystalline damage in high-dose phosphorous implanted and post implantation annealed 4H-SiC layers 1/%\*#z z.!"(!0\*!z/,!0.+/+,5^z\$!z\$.0!.%60%+\*z.!2!(! z0\$0z0\$!z%),1.%0%!/z.!z0%¥ 20! z5z\*\*!(%\*#z0zz 0!),!.01.!z/z(+3z/zDECC[z "+.zFCz)%\*\_z 0\$+1#\$z 0\$!z/1""%%!\*0z.!¥ covery of the crystallinity needs higher annealing temperatures than 1200°C. It is also found ".+)z0\$!z z.!"(!0\*!z\*(5/!/z0\$0z0\$!z\*\*!(%\*#z0zDJCC[z0%20!/z0\$!z%),1.%0%!/z\* z.!¥ +2!./z0\$!z.5/0((%\*%05z+"z%),(\*0! z(5!.z3%0\$%\*zDz)%\*^z\$!/!z.!/1(0/z/1##!/0z0\$0z0\$!z)!0\$¥ od can give the information of, not only the electrical properties, but also the crystalline

In conclusion, the electrical characteristics of SiC wafers and the electrical properties and 0\$%'\*!//z +"z %z !,%(5!./z \*z !z +0%\*! z /%)1(0\*!+1/(5z ".+)z 0\$!z \*(5/!/z +"z z .!"(!¥ 0\*!z/,!0.+/+,5z%\*z\*+\* !/0.10%2!z\* z+\*00(!//z)\*\*!.\_z3\$%\$z)'!/z,+//%(!z 0+z+¥ tain the spatial mapping of the electrical characteristics and thickness of SiC epilayers by scanning a probing light beam. Therefore, the method we proposed is a useful technique as

and epilayers with carrier concentrations ranged from 1016 to 1019cm–3 orders.

Figure 18 shows the IR reflectance spectra for the samples annealed for various annealing periods. The spectrum for the sample annealed for 0.5 min is almost the same as that for the sample annealed at 1400°C for 30 min. There is little change with annealing period up to 10 min in the reflectance spectra except for the oscillation periods. Since the oscillation periods are concerned with the thickness of the implanted layer, these changes suggest that the 0\$%'\*!//z+"z0\$!z%),(\*0! z(5!./z%/z\$\*#! z5z!2,+.0%+\*z+.z,.!%,%00%+\*z%\*z0\$!z%),(\*0¥ ed SiC layer. From the analysis, the thickness of the implanted layer *dimpla* decreases from 0.25 µm (0.5 min annealed) to 0.19 µ)zcDCz)%\*z\*\*!(! d\_z\* z0\$!z0\$%'\*!//z+"zz#. ! w.¥ rier-concentration layer increases from 0.05 µm to 0.08 µm. The volume fraction of defective SiC phase decreases drastically down to 2.9 % by 0.5 min annealing and is almost constant up to 10min. The derived annealing period dependence of free carrier concentration and mobility also shows that the recovering of the crystallinity and the electrical activation are sufficient by the annealing even for 0.5 min. These results indicate that the high temperature annealing as high as 1700°C puts the impurities onto substitutional lattice sites and recovers the crystallinity of the implanted layers within 1 min.

Figure 17. The annealing temperature dependences of (a) volume fraction of defective SiC phase, and (b) free carrier concentration and mobility in re-crystallized SiC phase. The values determined from Hall effect measurement also plotted in (b) for comparison [15].

Figure 18. The IR reflectance spectra obtained from the samples annealed at 1700°C for various annealing periods [15].
