High temperature ion implantation and activation annealing technologies for mass production of SiC power devices
Kazuo Tezuka1,a, Tatsuro Tsuyuki1,b,Saburo Shimizu1,c, Shinichi Nakamata2,d, Takashi Tsuji2,e, Noriyuki Iwamuro2,f, Shinsuke Harada2,g, Kenji Fukuda2,h
and Hiroshi Kimura3,i
1ULVAC, Inc., 2500 Hagisono, Chigasaki, Kanagawa 253-8543, Japan
socks2National Institute of Advanced Industrial Science and Technology, 16-1 Onogawa,
Tsukuba, Ibaraki 305-8569, Japan
3Fuji Electric Co., Ltd., 11-2 Osaki, Shinagawa, Tokyo 141-0032, Japan
a kazuo_,
b tatsurou_,
c saburou_,
d s.jp,
e jp,
f jp,
g jp, h jp, i jp Keywords: silicon carbide, SBD, power device, ion implantation, activation annealing
Abstract. In this paper, we demonstrate the fabrication of SBD utilizing SiC process line specially designed for mass production of SiC power device. In SiC power device process, ion implantation and activation annealing are key technologies. Details of ion implantation system and activation annealing system designed for SiC power device production are shown. Further, device characteristics of SBD fabricated using this production line is also shown briefly.
Introduction
SiC is a promising miconductor material for power electronics becau of its superior breakdown voltage, thermal conductivity, radiation resistance and chemical attack. In this power device process, ion implantation and activation annealing are key technologies, becau impurity implantation is nec
essary for its low diffusivity in SiC and post implantation annealing as high as 1600-2000°C is required for activation of implanted impurities and for annealing of implantation induced damage. In this paper, details of ion implantation system and activation annealing system designed for SiC power device production are shown. Further, we demonstrate the fabrication of SBD[1]utilizing this SiC process line specially designed for the mass production of SiC power devices.
Mass production line for SiC power device
In the constructed mass production line, ion implantation system (ULVAC, IH-860DSIC) and activation annealing system (ULVAC, PFS-4000-5) designed for the production of SiC power devices were ud. Production type ion implantation system has following advantages over conventional machine in the mass production of SiC power devices:
a) high throughput, high temperature implantation (up to 500℃) using ESC (electro-static-chuck) hot plate for eliminating the accumulation of implantation induced damage,
b) high throughput two beam line machine. Each line can accommodate both room temperature (RT) and high temperature implantation,
c) multi-energy implantation for box-profile doping (maximum 860keV; double charged ion).
Production type annealing system is provided with induction heating and capable of heating of 5 pieces of 4 inch SiC wafer rapidly up to 2000°C. Figure 1 shows the sheet resistance (Rs) distributio
n among 5 pieces of Al implanted (3E19cm -3) SiC wafer after annealing at 1600°C obtained by this annealing system. Uniform Rs distribution of < 2% (|Rs-Rm|/Rm x 100%, Rm: mean value of Rs),
which is sufficiently uniform for the mass production, was obtained among 5 pieces of 3 inch wafer.我心永恒英文
High temperature ion implantation and activation annealing technologies in this process line High temperature implantation is important for eliminating the accumulation of implantation induced damage [2-6]. Ion implantation temperature dependences of physical and electrical properties of annealed SiC samples were investigated using ion implantation system and activation annealing system of this constructed SiC process line.
Figure 2 shows the RHEED patterns of
RT implanted and high temperature (500°C)tokio hotel
Al implanted SiC samples (30-300keV,
5E18cm -3) before and after annealing at
1700°C. As shown in the patterns,
diffraction spots and Kikuchi patterns are
clearly obrved in each sample. This means
the density of implantation induced damage
is not so high even at RT implantation at this
implantation condition. This obrvation is
consistent with the results of Hall
measurements after annealing. Mobilities
and sheet carrier concentrations of two
samples are almost the same, that is,
µ=37(cm 2/Vs), n=2.1E12(cm -2) for RT implanted sample and µ=33(cm 2/Vs), n=2.5E12(cm -2) for 500°C implanted sample. Figure 3 also shows the RHEED patterns of RT implanted and 500°C implanted SiC
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samples at higher dosage (30-300keV,
2E20cm -3) before and after annealing at
1700°C. RHEED patterns of RT implanted
samples show quite different from tho at
the dosage of 5E18cm -3. Inten halo pattern
is obrved after implantation and 3C-SiC
growth on 4H-SiC is obrved after
annealing at 1700°C. This means amorphous
layer is formed after RT implantation and
3C-SiC is grown during annealing at 1700°C.
The results of Hall measurements show
different characteristics from tho at the
dosage of 5E18cm -3, that is, µ=3.7(cm 2/Vs),
n=1.2E14(cm -2) for RT implanted sample and µ=8.4(cm 2/Vs), n=6.6E13(cm -2) for 500°C implanted sample. Mobility of RT implanted sample is lower than that of 500°C implanted sample. This is probably due to the residual implantation induced damage.
However, sheet carrier concentration of RT
implanted sample is higher than that of 500°C implanted sample. One explanation of this electrical characteristics is due to valence band tailing which induces the decrea of impurity binding energy at
Figure 2. RHEED patterns of Al implanted SiC samples (30-300keV, 5E18cm -3): (a) RT implanted and (b) annealed at 1700°C, (c) 500°C implanted and (d) annealed at 1700°C. Figure.3 RHEED patterns of Al implanted SiC samples (30-300keV, 2E20cm -3): (a) RT implanted and (b) annealed at 1700°C, (c) 500°C implanted and (d) annealed at 1700°C.
英语口语学习心得heavy doping [7, 8]. The low temperature implantation is very attractive for the improvement of throughput for the mass production of SiC power devices, though the detail of the mechanism is not understood. Further investigation should be required for the application of this low-temperature implantation. We employed 500°C implantation for the realization of high quality SBD as mentioned in the next ction.
Photo-resist coating and baking is often ud for
carbon capping to suppress surface roughening
due to Si evaporation during high temperature
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activation annealing [9, 10]. However, sputter
deposited carbon film was ud as capping
material in this mass production line. This capping
method is superior to conventional carbon capping
using photo-resist baking in simplicity and
reproducibility of the process. Further, sputtering
process is superior in eliminating impurity
incorporation into the capping material by using
high purity carbon target. Before activation
泡泡少儿英语官网annealing, carbon capping was carried out using
sputtering system (ULVAC CS-200). Figure 4 shows typical AFM images of carbon-cap removed sample after annealing. Carbon-cap was
removed by ashing using oxygen plasma.
Excellent surface smoothness of Ra<0.2nm was obtained as shown in Fig. 4. Good uniformity distribution of Ra of <0.20nm(10µm x 10µm) among 5 pieces of 3 inch wafer was obtained using this annealing system.
Excellent surface smoothness obtained by
the high temperature implantation, carbon
capping and activation annealing technologies
is also confirmed by gate oxide reliability test
of gate oxide layer formed on SiC substrate.
The MOS capacitors were prepared by the wet
oxidation and H 2 annealing with the doped gate
polysilicon gate electrode. TDDB tests of gate
oxide layers were carried out with and without
activation annealing (1600°C) at 250°C with
applied electric field of 9MV/cm. Figure 5
shows the Weibul plots of the lifetime of MOS
capacitors formed on the SiC wafers. No
difference was obrved between annealed and
without annealed samples, indicating ion implantation, carbon capping and annealing
process employed in this process line do not
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induce surface roughness or defects which degrade brake down characteristics. So, the three process, that is, high temperature implantation, carbon capping using sputtering and activation annealing are suitable for mass production of SiC power device.
SBD fabrication using constructed mass production line
The 1200V class SiC-SBDs were fabricated using this mass production process line on 4H-SiC 3 inch wafers with n-type epitaxial layers grown on (0001)Si face. We adopted a junction barrier Schottky structure and Schottky metal of titanium to realize low forward voltage drops and low rever leakage currents [11]. Al + and P + ion implantation were carried out at 500°C as mentioned in the previous ction. Figure 6 shows the typical forward characteristics of fabricated SiC-SBDs. The
Figure 4. Typical AFM images of carbon-cap
removed samples after annealing. Figure 5. Weibul plots of the lifetime of MOS capacitors formed with and without annealing atbig sur
1600°C.
forward characteristics showed threshold voltage decrea
from 0.9V to 0.75V with the temperature increa from 25°C to
175°C. The slope of the current-voltage curve decread with
temperature due to the increa of the substrate and the drift
layer resistance. From the features, a positive temperature
coefficient of the forward voltage drop was achieved, which
was favorable to the parallel operation of the chips for large
current ratings. The typical rever characteristics showed
breakdown voltages of 1316V at 25°C and 1332V at 175°C,
respectively. The leakage currents at 1200V were 15µA at 25°C
and 20µA at 175°C, respectively. The leakage current was nearly identical in this temperature range, which was due to the wide band gap of SiC. By substituting fabricated SiC-SBDs for Si-pin diodes, the estimated total power loss of the latest
modules comprid by Si-IGBTs and the diodes was reduced by 35%. The detail was described in Ref. [1].
Summary
High temperature ion implantation and activation annealing technologies for mass production of SiC power device were shown together with new carbon capping process using sputtering. Electrical, physical properties of SiC samples obtained by the technologies showed good uniformities. The 1200V class SBDs fabricated by the process also showed excellent I-V characteristics.
Acknowledgement
This work was supported by an AIST R&D Initiative Program on the Innovative Industrial Technology (FY 2009-2011), under a title of "Demonstration on Mass Production Technology for SiC Power Devices."
References
[1] T. Tsuji, A. Kinoshita, N. Iwamuro, K. Fukuda and H. Kimura, Proc. 1st International Electric Vehicle Technology Conference 2011, 20117254.
[2] T. Kimoto, N. Inoue and H. Matsunami, phys. stat. sol. (a) 162, 263 (1997).
[3] V. Khemka, R. Patel, N. Ramungul, T. P. Chow, M. Ghezzo and J. Kretchmer, J. Electron. Mater. 28, 167 (1999).
[4] Y. Negoro, N. Miyamoto, T. Kimoto and H. Matsunami, Appl. Phys. Lett. 80, 783 (2002).
[5] T. Kimoto, O. Takemura, H. Matsunami, T. Nakata and M. Inoue, J. Electron. Mater. 27, 358 (1998).
[6] T. Troffer, M. Shadt, T. Frank, H. Itoh, G. Pensl, J. Heindl, H. P. Strunk and M. Maier, phys. stat. sol. (a) 162, 277 (1997).
[7] T.Watanabe, A. Aya, R. Hattori, M.Imaizumi and T. Oomori, Mater. Sci. Forum Vols. 645-648, pp705-708 (2010).
[8] Y. Negoro, T. Kimoto, H. Matsunami, F. Schmid and G. Pensl, J. Appl. Phys. 96, 4916 (2004).
the saturdays[9] Y. Negoro, K. Katsumoto, T. Kimoto and H. Matsunami, Mater. Sci. Forum Vols. 457-460, pp933-936 (2004).
[10] K. A. Jones, M. A. Derenge, P. H. Shah, T. S. Zheleva, M. H. Ervin, K. W. Kirchner, M. C. Wood, C. Thomas, M. G. Spencer, O. W. Holland and R. D. Vispute, J. Electron. Mater. 31, 568 (2002).
[11] A. Kinoshita, T. Nishi, T. Ohyanagi, T. Yatsuo, K. Fukuda, H. Okumura and K. Arai, Mater. Sci. Forum Vols. 600-603, pp643-646 (2009).
Figure 6. Typical forward characteristics of fabricated SiC-SBDs .
Silicon Carbide and Related Materials 2011
10.4028/www.scientific/MSF.717-720
High Temperature Ion Implantation and Activation Annealing Technologies for Mass Production of SiC Power Devices
10.4028/www.scientific/MSF.717-720.821
