Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Reexamination Certificate
2000-03-17
2002-12-03
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
C374S130000, C702S130000, C392S416000, C118S724000
Reexamination Certificate
active
06488407
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation temperature measuring method and a radiation temperature measuring system to be applied to, for example, the temperature of a semiconductor wafer.
2. Description of the Related Art
A single-wafer heating apparatus is one of heating apparatus for heat-treating semiconductor wafers. Such a heating apparatus heats a wafer for an annealing process by heat generated by heating lamps. To anneal a wafer in a high intrasurface uniformity, it is necessary to measure the temperature of the wafer, and to regulate the temperatures of the heating lamps on the basis of measured temperature in a feedforward or feedback control mode. Some methods of measuring the temperature of the wafer use a radiation thermometer.
These methods measure the emissivity of the wafer and determine the temperature of the wafer on the basis of the emissivity and measured intensity of radiation emitted by the wafer. Methods of measuring the emissivity are classified roughly into two methods. In one type of methods, light having a known wavelength and a known intensity is emitted, then reflected light from the surface of the wafer is detected to determine the emissivity. In the other type of methods, radiation emitted by the wafer is subjected to multiple reflection, then reflected radiation is detected in a plurality of environments respectively having different geometric factors, then the emissivity is calculated on the basis of a plurality of data.
A temperature measured by any one of those methods includes a measuring error caused by a loss due to the scattering of the reflected light outside a probe principally owing to scattering on the measuring surface of the wafer, and noise caused by the unnecessary detection of light emitted by the heating lamps. Therefore, the probe must be set very close to the measuring surface of the wafer, i.e., the probe must be set at a position at 0.5 to 5 mm from the measuring surface of the wafer, to suppress the effect of those causes of measuring error. Such a requirement with the probe places significant restrictions on the design of the radiation thermometer and there is the possibility that the probe affects adversely to the uniform heating of the wafer.
U.S. Pat. No. 5,660,472 discloses a correcting technique for measurement employing a virtual blackbody included in a multiple reflection system. Basically, this correcting technique is practiced as follows. As shown in
FIG. 13
, the measuring system includes, as basic components, a wafer W, a reflecting plate (bottom wall of a vessel)
101
, and first and second probes (two sapphire rods)
102
. The temperature of the wafer W is measured by the following procedure.
(i) The first probe
102
of a diameter d
p
is inserted in a first aperture of a diameter d
1
(d
1
>d
p
) formed in the reflecting plate
101
.
(ii) Since the aperture of the finite size exists when virtual blackbody cavity is formed, reflected light is reduced by an amount. Therefore, an effective reflectivity R
1
is determined taking into consideration a decrement in reflected light.
(iii) The second probe
102
of a diameter d
p
is inserted in a second aperture of a diameter d
2
(d
2
>d
p
) formed beside the first hole.
(iv) An effective reflectivity R
2
is determined taking into consideration a decrement in reflectivity.
(v) The reflectivities R
1
and R
2
, measured temperatures T
1
and T
2
measured respectively by the probes
102
are substituted into a specific equation to calculate the temperature of the wafer.
The foregoing correcting technique has the following problems:
{circle around (1)} Basically, the virtual blackbody is composed of a flat plate of an infinite dimensions, however, the characteristics of the virtual blackbody is spoiled by the two apertures formed therein for the probes.
{circle around (2)} Normally, the reflectivity of the virtual blackbody is not affected by the emissivity of the wafer. As obvious from the fact that the virtual black body takes the effective reflectivities into consideration, the reflectivity of the reflecting plate
101
is not “1”; that is, the reflectivity of the reflecting plate
101
is affected to the emissivity of the wafer, so that accurate measurement of thermal emissive cannot be achieved.
{circle around (3)} The radiation thermometer cannot measure low temperatures.
SUMMARY OF THE INVENTION
The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a radiation temperature measuring method capable of measuring the temperature of a measuring object in a high accuracy by using a multiple reflection system.
Another object of the present invention is to provide a radiation temperature measuring system suitable for carrying out the radiation temperature measuring method.
According to a first aspect of the present invention, a radiation temperature measuring method is provided, which determines the temperature of a flat measuring surface of a measuring object on the basis of a measured radiation intensity obtained by using an optical reflector having a flat reflecting surface narrower than the measuring surface and disposed with the reflecting surface thereof facing the measuring surface, and optical path extending through the optical reflector and respectively having an exposed light-receiving plane surrounded by the reflecting surface, and by receiving radiation undergone multiple reflection between the measuring surface and the reflecting surface through the light-receiving plane of the optical path. The method including the following steps:
(a) setting four combinations of measuring conditions (S
1
, d
1
), (S
1
, d
2
) (S
2
, d
1
) and (S
2
, d
2
), where S
1
and S
2
are the areas S of the reflecting surfaces, and d
1
and d
2
are distances d between the reflecting surfaces and the measuring surface, and measuring radiation intensities E
sid1
, E
s1d2
, E
s2d1
and E
s2d2
for the four combinations;
(b) substituting the areas S, and an area of a side surface of a cylindrical space between the reflecting surface and the measuring surface (a product of perimeter D of the reflecting surface and the distance d) and the measured radiation intensity E into an expression:
E
=
ϵ
E
0
1
-
R
(
1
-
ϵ
)
·
S
+
D
·
d
(
E
N1
-
E
L1
)
+
(
E
N2
-
E
L2
)
where &egr; is an emissivity of the measuring surface, E
0
is a blackbody radiation intensity at a temperature T, R is a reflectivity of the reflecting surface, E
N1
−E
L1
is a correction for correcting an error due to noise entering and leaking from the cylindrical space between the reflecting surface and the measuring surface, and E
N2
−E
L2
is a correction for correcting an error due to noise entering and leaking from the space between the reflector and the optical path, to calculate E
N2
−E
L2
for each of the four combinations;
(c) substituting calculated E
N2
−E
L2
into the expression, setting two combinations of measuring conditions of the area S and the distance d, the two combinations being different from each other, measuring radiation intensities for the two combinations, and substituting the measured radiation intensities into the expression to determine E
N1
−E
L1
;
(d) correcting the measured radiation intensity on the basis of the expression into which E
N1
−E
L1
and E
N2
−E
L2
are substituted;
(e) calculating the emissivity of the measuring surface on the basis of a measured radiation intensity measured with the reflector removed and the corrected measured radiation intensity corrected in step (d); and
(f) determining temperature of the measuring surface on the basis of the emissivity of the measuring surface and the measured radiation intensity measured with the reflector removed.
The two combinations used in step (c) may be selected from the combinations in step (a).
According to a second aspect of the present invention, a rad
Kitamura Masayuki
Morisaki Eisuke
Shigeoka Takashi
Takahashi Nobuaki
De Jesús Lydia M.
Gutierrez Diego
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
LandOfFree
Radiation temperature measuring method and radiation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiation temperature measuring method and radiation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation temperature measuring method and radiation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2933287