Thermal processing apparatus

Details Thermal processing apparatus Thermal processing apparatus

2001-06-15

2003-11-18

Paik, Sang Y. (Department: 3742)

Electric heating

Heating devices

With power supply and voltage or current regulation or...

C392S418000, C118S724000

Reexamination Certificate

active

06649885

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal processing apparatus and, more particularly, to a thermal processing apparatus, for example, used for conducting epitaxial growth processing, etching, and the like on wafers.
2. Description of the Relevant Art
Hitherto, a radiation thermometer has been frequently used in a thermal processing apparatus for non-contact measurement of the surface temperature of a wafer or the like without scratching the wafer surface and contaminating the atmosphere within a chamber.
FIG. 7
is a diagrammatic sectional view of a conventional thermal processing apparatus of this type wherein a radiation thermometer is arranged, and in the figure, reference numeral
31
a
represents a vessel body which forms a chamber. The vessel body
31
a
is made of a material, such as quartz glass which transmits infrared rays, in the shape of an oval in a sectional view. At both ends of the vessel body
31
a
, an inlet
31
b
and an outlet
31
c
for a gas are formed, respectively. A prescribed gas
32
supplied from the inlet
31
b
passes through the vessel body
31
a
to reach a wafer
33
and is discharged from the outlet
31
c
. In a prescribed position inside the vessel body
31
a
, a susceptor
31
d
is arranged, which is rotated by a driving means (not shown). The wafer
33
in the shape of a disk as a workpiece is mounted on the susceptor
31
d
. An apparatus body
31
comprises the vessel body
31
a
, inlet
31
b
, outlet
31
c
, susceptor
31
d
, and associated parts.
Above and below outside the vessel body
31
a
, infrared lamps
34
a
and
34
b
as a heating means
34
are placed, respectively. These infrared lamps
34
a
and
34
b
are connected through wires
35
a
and
35
b
to a power supply means
35
, respectively. The power supply means
35
is connected through a signal line
36
b
to a controlling means
36
which comprises a power supply controlling means
36
a
. On the other hand, in a prescribed position above the wafer
33
outside the vessel body
31
a
, a radiation thermometer
37
as a temperature measuring means is arranged, which is connected through a signal line
37
a
to the controlling means
36
.
When a radiation light
33
a
emitted from the top of the wafer
33
penetrates the vessel body
31
a
(a transmission part
31
e
) to enter the radiation thermometer
37
, a measured temperature T
m
of the top of the wafer
33
is obtained through the radiation thermometer
37
based on the brightness signal of the radiation light
33
a
, the emissivity of the wafer
33
, and the like, and this signal s
1
is transmitted through the signal line
37
a
to the controlling means
36
. A required electric energy P is computed based on the deviation of the measured temperature T
m
from a preset desired temperature T
M
by the power supply controlling means
36
a
in the controlling means
36
, and this signal P is transmitted through the signal line
36
b
to the power supply means
35
. Then, on the basis of the signal P, prescribed electric energies P
1
and P
2
(here, P
1
+P
2
=P) are distributed and supplied by the power supply means
35
through the wires
35
a
and
35
b
to the infrared lamps
34
a
and
34
b
, respectively. A thermal processing apparatus
30
comprises the apparatus body
31
, heating means
34
, power supply means
35
, controlling means
36
, radiation thermometer
37
, and associated parts.
FIG. 8
is a graph indicating changes in the measured temperatures during the time when, after epitaxial growth processing is conducted on a total of seven wafers
33
one by one with the same heating pattern, using a conventional thermal processing apparatus
30
wherein a susceptor
31
d
(all in
FIG. 7
) is adjusted to be in a horizontal position, cleaning is conducted on a vessel body
31
a
(hereinafter, one process wherein, after thermal processing is successively conducted on a prescribed number of wafers
33
with the same operating conditions, vessel body cleaning is conducted, is referred to as one chance), and these steps are successively repeated. In the figure, X shows a measured temperature T
m
of the top of the wafer
33
, while ◯ shows a measured temperature T
p
of the bottom of the susceptor
31
d
measured using a thermocouple thermometer (not shown) separately arranged.
As is obvious from
FIG. 8
, the measured temperature T
m
of the top of the wafer
33
measured using a radiation thermometer
37
(
FIG. 7
) is kept about a prescribed value (about 1125° C.) at all times. On the other hand, the measured temperature T
p
of the bottom of the susceptor
31
d
measured using the thermocouple thermometer rises by degrees from about 1125° C. to about 1129° C. as the number of processed wafers
33
increases from 1 to 7. Then, the vessel body cleaning makes it back to the original temperature of about 1125° C. This means that the transmissivity of a radiation light
33
a
in the vicinity of a transmission part
31
e
(both in
FIG. 7
) gradually decreases every time one wafer
33
is processed, so that the temperature of the top of the wafer
33
becomes apparently lower. Therefore, extra power is supplied to a heating means
34
(
FIG. 7
) to keep the desired temperature (about 1125° C.), leading to a substantial rise in the temperature T
p
of the bottom of the susceptor
31
d.
FIG. 9
is a graph indicating changes in the measured temperatures during the time when, after epitaxial growth processing is conducted on a total of seven wafers
33
one by one in a state where a prescribed electric energy P is regularly supplied to a heating means
34
as a test pattern, using a conventional thermal processing apparatus
30
wherein a susceptor
31
d
(all in
FIG. 7
) is adjusted to be in a horizontal position, cleaning is conducted on a vessel body
31
a
, and these steps are successively repeated. In the figure, X shows a measured temperature T
m
of the top of the wafer
33
, while ◯ shows a measured temperature T
p
of the bottom of the susceptor
31
d
measured using a thermocouple thermometer (not shown) separately arranged.
As is obvious from
FIG. 9
, the measured temperature T
p
of the bottom of the susceptor
31
d
measured using the thermocouple thermometer is kept about 1125° C. at all times. On the other hand, the measured temperature T
m
of the top of the wafer
33
measured using a radiation thermometer
37
(
FIG. 7
) falls by degrees from about 1125° C. to about 1118°° C. as the number of processed wafers
33
increases from 1 to 7. Then, the cleaning of the vessel body
31
a
makes it back to the original temperature of about 1125° C. This supports that the transmissivity of a radiation light
33
a
in a transmission part
31
e
(both in
FIG. 7
) gradually decreases every time one wafer
33
is processed, so that the measured temperature T
m
of the top of the wafer
33
becomes apparently lower.
FIG. 10
is a graph indicating changes in temperature when epitaxial growth processing is conducted on one wafer
33
with a prescribed heating pattern, using a conventional thermal processing apparatus
30
wherein the wafer
33
is mounted in a slightly tilted condition on a susceptor
31
d
(all in FIG.
7
), being rotated. In the figure, (A) shows the desired temperature T
M
, (B) shows the measured temperature T
m
of the top of the wafer
33
, and (C) shows the measured temperature T
p
of the bottom of the susceptor
31
d
measured using a thermocouple thermometer (not shown) separately arranged.
As is obvious from
FIG. 10
, the measured temperature T
m
of the top of the wafer
33
, the desired temperature T
M
, and the measured temperature T
p
of the bottom of the susceptor
31
d
are not in agreement with one another, and the measured temperature T
m
of the top of the wafer
33
periodically repeats small fluctuations. The periodic fluctuations are in tune with the rotation period of the susceptor
31
d
. This means that the measured temperature T
m
measured using a radiation thermometer
37
is liable to peri

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