4-2Carbon Heating Tube Used for Rapid Heating System for Semiconductor Annealing
Tomoyoshi Miyazaki1,3, Go Kobayashi2, Takashi Sugawara3, Toshitaka Kikuchi3, Masahiko Hasumi3,and Toshiyuki Sameshima3
1Techno Research., Ltd., 5-9-10 Shimozato, Higashikurume, Tokyo, 203-0043, Japan2

Orc manufacturing Co., Ltd. 4896 Tamagawa, Chino, 391-0011 Japan

3

Tokyo University of Agriculture and Technology, Graduate School of Engineering, 2-24-16, Naka-cho, Koganei, Tokyo, 184-8588, Japan
Email: tsamesim@cc.tuat.ac.jp

We report a new heating system with a carbon heating tube (CHT) which was made by a quartz tube filled with carbon particles and Ar gas. A
60-mm long and 4-mm diameter CHT was set in a cavity in which 2.45-GHz microwave was introduced. Via complete absorption of theinput microwave power by carbon in the CHT during multi-reflection of microwave in the cavity, the CHT was effectively heated to 1279oC
at a microwave power of 200 W for 33 s. Crystallization of a 50-nm-thick amorphous silicon thin film formed on glass substrate wasdemonstrated by mechanically moving the silicon sample just below the heated CHT. A high crystalline volume ratio of 0.9 was achieved.
Introduction
Thermal annealing is important to fabricate semiconductor

the quartz tubes: the packing density was controlled as 0.08, which

1-4)

devices such as thin film transistors (TFTs) and solar cells.

heating.12) After carefully evacuating air gas inside the quartz tubes

Activation and crystallization are achieved by heat treatment toby a vacuum pump under keeping carbon powders stay in the1.

5)

form the pn junction and crystalline state.

was determined by the previous work as the best value for

Many heatingquartz tubes, Ar inert gas was filled in the quartz tube at 10.5 Torr.

technologies have been developed such as rapid thermal annealing,The edges of the quartz tubes were closed by thermal welding.

6-9)

10)

laser annealing , plasma jet annealing , and rapid thermal
11)

Two quartz rods were jointed at the edges of the CHT by thermal

We have recently proposed a combination of thewelding to hold the CHT. The CHTs is consequently heated bycarbon powder absorber with 2.45 GHz microwave irradiation as a

microwave irradiation with no loss of carbon powers via oxidation.

simple rapid thermal annealing method.12,13) Conductive carbon is

Moreover, CHTs have no electrode wires, which gives a capability

heated via free carrier absorption of the electromagnetic energy ofof highly thermal proof structure because the junction between

microwave generated from vibration of electrons in the cavity

lamp materials and the electrode metals has always a serious

resonator of the magnetron. Carbon powders with a packing

problem of thermally stress-induced damage. A CHT was placed

annealing.

density of 0.08 achieved heating at the temperature of 1163oC by1000 W microwave irradiation for 28 s. The activation andrecrystallization of silicon implanted with boron and phosphorus
atoms were also demonstrated.
In this paper, we propose a new heating systems with a lamp ofcarbon heating tube (CHT) for rapid thermal annealing forsemiconductor device fabrication. We first present the heating
system in detail. We then demonstrate 1279oC heating properties of
the CHT by 2.45 GHz microwave irradiation. We also demonstrate
crystallization of amorphous silicon films by the present heatingsystem.
Experimental
Figure 1 shows (a) a schematic image of CHT and (b) a heatingsystem with the CHT. Quartz tubes with 60-mm long and 4-mm
inter diameter and 6-mm outer diameter were made.
2-μm-diameter-carbon powders with a 0.1-g weight were put inFig. 1 (a) Schematic image of CHT and (b) a heating systemwith the CHT.

AM-FPD'18

in the heating system as shown in Fig. 1(b), which consists of a

microwave irradiation, as shown in Fig. 2(a). Locally spontaneous

magnetron for generating 2.45-GHz microwave with an electricalheating in the CHT probably occurred in the initial stage.

circuit for controlling a microwave power ranging from 100 to

Subsequently, uniformly strong blight light emission was observed

1500 W, an isolator for blocking the reflectance of microwave

at 33 s in about 40-mm long region. This indicate that heat

backward the magnetron, a power monitor, a wave-guide tube, anddiffusion simultaneously occurred inside the CHT to make thea microwave cavity made by Al metals. The switching circuit

temperature uniform in the CHT during microwave irradiation.

controlled the intensity of microwave gradually increasing to aThe CHT effectively absorbed the microwave power andsetting power by 3 s after the initiation. The Microwave generated

spatial-uniformly heated to a temperature high enough to emitin the magnetron was introduced to the cavity by the wave guideblight light. The intensity of light emission was decreased

tube via the isolator and power monitor. The cavity was fabricateduniformly after the termination of microwave as shown by thewith a sophisticated structure to promote multiple reflection in thephotograph at 38 s. This means that the CHT was cooled down

cavity, in which there were a wave-guide tube extended by 153

uniformly. The temperature increased with time in the initial stage

mm in the upper cylindrical part of the cavity and a reflection

for every power case as shown in Fig. 2(b). This means thatmetal plate slant placed at the bottom spherical part of the cavity.

increase in the temperature was governed by heat capacity of theThat designed cavity achieved to effectively close microwave

CHT. On the other hand, the increasing rate of temperature became

power in the cavity: the power monitor revealed a forward power

low especially in the high microwave power case in the final stageof 500 W with a reverse power less than 10 W (detection limit).

of microwave irradiation. A radiation power loss caused by

The CHT effectively absorbed the microwave power during theblack-body radiation became important when the CHT was heatedmultiple reflection of microwave in the cavity. The cavity had ato high temperature. A high temperature of 1279oC was observed

window port for observing light emission from CHT heated byat 33 s for 200 W. The maximum rate of temperature increase wasmicrowave. A thermometer detecting 900-nm wavelength

obtained as 56 K/s in the case of a microwave power of 200 W.

radiation light CHINO IR-FAS was used to monitor change in theWhen the microwave irradiation was terminated, the temperaturetemperature of the CHT in real time. The detection lower limit ofthe thermometer was about 550oC. An infrared digital camera wasalso used to observe CHT heating. The Microwave was irradiatedinto the cavity for 33 s, in which the microwave intensity increased
during initial 3 s and kept constant for 30 s. A mechanicallymoving stage was also installed in the cavity, as shown in Fig. 1(b)to move a sample just below the CHT for demonstration of heatingby the CHT. 50-nm-thick amorphous silicon films formed on glass
substrates were prepared by plasma enhanced chemical vapor
deposition at 300oC. The silicon film was annealed by CHT heatedwith continuous microwave irradiation at 200 W. The silicon film
sample was moved at 0.12 mm/s in the normal direction just below
the CHT. Uniform change in color of the silicon film was observedin 40 x40 mm2 region by CHT heating. Raman scattering andoptical reflectivity spectra measurements were used to estimate
crystallization properties with the crystalline volume ratio.
Results and discussion
Figure 2 shows (a) a photograph of light emission from the CHT
heated by 200-W microwave irradiation at 5, 33, and 38 s detectedby the infrared camera and (b) changes in the temperature of theCHT with different powers ranging from 100 to 200 W during andafter the microwave irradiation measured by the thermometer.
Several spots emitting light was observed at 5 s of 200-W

Fig. 2 (a) Photographs of light emission from the CHT heatedby 200-W microwave irradiation at 5, 33, and 38 s and (b)changes in the temperature of the CHT with different powers
ranging from 100 to 200 W for 33 s.

AM-FPD'18

of CHT is rapidly decreased because of the radiation loss.
Figure 3 shows the maximum temperature of the CHT as afunction of microwave power ranging from 100 to 200 W for 33 sirradiation. The CHT was heated to 932oC at 100 W. Themaximum temperature increased to 1279oC as the microwave
power increased to 200 W. The maximum temperature wasapproximately determined by balance between the input
microwave power and blackbody radiation loss as shown by solid
curve calculated by the blackbody radiation theory. The
temperature approximately increased to the microwave power tothe power of 0.25, (microwave power)0.25. Those results of Figs. 2
and 3 show rapid and clean heating system with a low power
consumption was realized.

Fig. 4 Optical reflectivity spectra of the silicon film sample
heated by the CHT at 200 W measured at (a) the top and (b)rear surfaces.
the as-deposited amorphous silicon film had a broad peakassociated with phonon of disordered bonding structure. The 19
shapes of the sharp peak were similar. The peak wavenumber
ranged from 514 to 516 cm-1, which was lower than that ofthermally relaxed crystalline silicon. This indicates the tensilestress existence between the silicon film and quartz substrate. TheFig. 3 Maximum temperature of the CHT as a function of
microwave power

full width at half maximum ranged from 7.0 to 9.5 cm-1. Broad tailassociated with the phonon mode of nano-crystalline andamorphous structures at around 500 and 440 cm-1 were very small.

Figure 4 shows the optical reflectivity spectra of the silicon film
sample heated by the CHT measured at the central 8x8 mm2
region at (a) the top and (b) rear surfaces. Large E1 and E2 peaks

Those results mean that the homogeneous crystalline state wasrealized.

owing to the optical transition in the tetrahedral crystalline band
appeared at 370 and 275 nm in the optical reflectivity spectra
measured at the top and rear surfaces of the silicon film sample.
Marked changes in the optical reflectivity caused by the opticalinterference effect between silicon top surface and bottom interface
were also observed for wavelength between 400 and 1000 nm.
These characteristics indicate that the silicon films werecrystallized in the whole thickness region. The experimental
optical spectra were analyzed by numerical calculation program.14)
The dashed curves shown in Fig. 4 (a) and (b) were calculated
spectra with a crystalline volume ratio of 0.9, which well fitted toexperimental spectra. The silicon film was well crystallized anddisordered region was almost eliminated.
Figure 5 shows the normalized Raman scattering spectra of theFig. 5 Normalized Raman scattering spectra of the silicon film
sample crystallized by the CHT measured at 19 points over thecrystallized region and the as-deposited amorphous silicon film
sample.

silicon film sample crystallized by the CHT measured at 19 points
over the crystallized region and the as-deposited amorphous silicon

The present heating system with the CHT will be applied forfilm sample. The crystallized silicon film had a sharp peakvarious heat treatment. High temperature heating of the CHT by

associated with the phonon mode of the crystalline lattice, while

low microwave power was demonstrated. Moreover, the CHT

AM-FPD'18

with no electrode has an advantage for its application to heat
treatment in severe environment for example high humidity
atmosphere. The CHT with no electrode will also make it possible
to realize simple heating system because no complicated wiring isnecessary.
4.

Conclusions
A new heating system with a carbon heating tube (CHT) wasproposed. The CHT was made with a quartz tube filled withcarbon particles and Ar gas. A 60-mm long and 4-mm innerdiameter CHT was set in a cavity in which 2.45-GHz microwave
was introduced. The sophisticated designed cavity completely
closed microwave with negligible small of microwave reflectanceloss. The CHT effectively absorbed microwave during(1986) 276.
8) K. Sera, F. Okumura, H. Uchida, S. Itoh, S. Kaneko and K. Hotta: IEEE
Trans. Electron Devices 36 (1989) 2868.
9) T. Serikawa, S. Shirai, A. Okamoto and S. Suyama: Jpn. J. Appl. Phys.
28 (1989) L1871.
10) S. HIGASHI, H. KAKU, H. MURAKAMI, S. MIYAZAKI, H.
WATAKABE, N.ANDO and T.SAMESHIMA: Jpn. J. Appl. Phys. 44(1989) 108.
11) G. Mannino: Appl. Phys. Lett. 78 (2001) 889.
12) T. Nakamura, S. Yoshidomi, M. Hasumi, T. Sameshima and T.
Mizuno: Mater. Res. Soc. Symp. 1666 (2014) A13-09.
13) S. Kimura, K. Ota, M. Hasumi, A. Suzuki, M. Ushijima and T.
Sameshima: Appl. Phys. A. 122 (2016) 695.
14) K. Ukawa, Y. Kanda, T. Sameshima, N. Sano, M. Naito and N.
Hamamoto: Jpn. J. Appl. Phys. 49 (2010) 076503.

multi-reflection of microwave in the cavity and heated to a hightemperature. The temperature and heating rate were obtained as
1279oC and 56 K/s for 33-s microwave irradiation at a power of200 W. Crystallization of a 50-nm-thick amorphous silicon thinfilm formed on glass substrate was demonstrated by mechanicallymoving the silicon sample just below the heated CHT with amicrowave power of 200 W. Optical reflectivity spectra
measurements revealed that crystallization in the whole film
thickness was achieved. A high crystalline volume ratio of 0.9
was obtained. Raman scattering spectra measurement resulted insharp peak of crystalline phonon mode. The peak shape wassimilar among 19 measurement points. Homogeneous crystalline
state was realized.
Acknowledgments
This work was partially supported by Japan Science and Technology
Agency ASTEP (No. AS2911903S).
References
1) S. Uchikoga amd N. Ibaraki: Thin Solid Films, 383, (2001) 19.
2) S. Inoue, K. Sadao, T. Ozawa, Y. Kobashi, H. Kwai, T. Kitagawa and T.
Shimoda: Tech. Dig. IEDM, 2000, p. 197.
3) K.Shibata and H. Takahashi: Workshop on Active Matrix Liquid Crystal
Displays'01, 2001, p. 219.
4) S. M. Sze: Semiconductor Devices, Wiley, New York, 1985.
5) Y. Taur and T, Ning: Fundamental of Modern VLSI Physics, Cambridge
University Press, Cambridge ,U. K., Chap. 2, 1998.
6) R. F. Wood and C. E. Giles: Rhys. Rev. B23 (1981) 2923.
7) T. Sameshima, S. Usui and M .Sekiya: IEEE Electron Device Lett. 7

AM-FPD'18