5. Conclusion

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

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

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

Annealing at 1700!

Wavenumber (cm-1) 2000 4000 6000

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

8000

as for activating the impurities.

22 Physics and Technology of Silicon Carbide Devices

plotted in (b) for comparison [15].

the crystallinity of the implanted layers within 1 min.

Reflectance (

!)100 !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 the carrier concentration and mobility in SiC wafers.

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

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 damages of ion-implanted SiC epilayers simultaneously.

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 z)+\*%0+.%\*#z0++(z+"z%z !2%!w,.+!//\_z%^!^\_z0\$!z)+\*%0+.%\*#z+"z0\$!z +,%\*#z+\*!\*0.0%+\*\_z.¥ rier mobility and thickness, and their uniformity over the wafers in homo-epitaxial growth ,.+!//\_z \* z 0\$!z .!+2!.5z+"z.5/0((%\*%05z \* z!(!0.%(z 0%20%+\*z+"z%),1.%0%!/z%\*z,+/0w%)¥ plantation-annealing process.

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

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[12] .%0\_z^\_z%&%'0\_z^\_z#1\$%\_z^\_z+/\$% \_z^\_z\z'/\$%)\_z^zcECCGd^z\$.0!.%¥ 60%+\*z+"z..%!.z+\*!\*0.0%+\*z\* z
+%(%05z%\*z\*w05,!z%z"!./z/%\*#z \*"..! z!¥

[13] Oishi, S., Hijikata, Y., Yaguchi, H., & Yoshida, S. (2006). Simultaneous Determination of Carrier Concentration, Mobility, and Thickness of SiC homoepilayers by Infrared

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