Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Having pulling during growth
Reexamination Certificate
1998-12-23
2001-02-13
Hiteshew, Felisa (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Having pulling during growth
C117S015000, C117S020000, C117S202000
Reexamination Certificate
active
06187090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and a device for measuring the temperature of the melt surface within an apparatus for pulling a single crystal and, more particularly, to methods for measuring the temperature of the melt surface within an apparatus for pulling a single crystal wherein non-contact temperature measurement is performed and a device is used for the methods.
2. Description of the Relevant Art
Keeping the temperature of the melt surface in optimum condition during single crystal growth is needed in order to ensure the quality of the single crystal. As a precondition, it is required that the temperature of the melt surface be accurately measured. A dip-type thermocouple, a non-contact radiation thermometer, and the like have been used for measuring the temperature of the melt surface. However, in a temperature measuring method wherein the thermocouple is used, the thermocouple easily wears and has a short life span, or constituents of the thermocouple contaminate the melt, resulting in a bad influence upon the quality of a single crystal to be pulled. Therefore, it is difficult to continuously measure the temperature of the melt surface for a long period of time.
In order to cope with the problem, recently a method wherein non-contact temperature measurement of the melt surface is performed using the radiation thermometer has been frequently used. The temperature measuring method wherein the radiation thermometer is used is based on the luminance of a thermal radiation light radiated from an object of measurement being determined from the temperature and the emissivity of the object of measurement. The temperature is obtained based on the luminance of the thermal radiation light measured by non-contact measurement and the emissivity obtained on a different occasion. Therefore, in the temperature measuring method wherein the radiation thermometer is used, there is no probability that impurities will contaminate a melt. The temperature of the melt surface can be continuously measured during the pulling of a single crystal.
FIG. 1
is a diagrammatic sectional view showing an apparatus
40
for pulling a single crystal incorporating a conventional temperature measuring device
42
wherein a radiation thermometer is used, and reference numeral
11
in the figure represents a crucible. The crucible
11
is cylindrical, and is supported with an ascent/descent means (not shown) by which the crucible
11
is moved up and down while being rotated. The vertical position of the crucible
11
can be adjusted by driving the ascent/descent means. An almost cylindrical heater
12
is arranged around the crucible
11
and an electric power supply regulator
12
a
is connected thereto. An almost cylindrical heat insulating mold
13
is arranged around the heater
12
, and a lower chamber's wall
14
is arranged around the heat insulating mold
13
so as to surround the heat insulating mold
13
. An upper chamber's wall
15
stands on a lower chamber's upper wall
14
a
having the shape of a ring.
Inside the upper chamber's wall
15
, a pulling shaft
16
a
is suspended. A seed crystal
16
b
is held by a holder
16
c
at the lower end of the pulling shaft
16
a
, which is wound while being rotated by a driving means
16
. A window
41
is formed in a vertical position on a lower chamber's side wall
14
b
where the melt surface
17
a
is located, and is sealed with a quartz glass member
41
a
or the like.
The crucible
11
is charged with a melt
17
of melted polycrystal silicon (Si) or the like. By bringing the seed crystal
16
b
into contact with the melt surface
17
a
and pulling the pulling axis
16
a
while rotating it, a single crystal
18
can be grown from the melt surface
17
a.
On the other hand, a radiation thermometer
43
is placed outside the window
41
in the almost horizontal direction, and is connected to a computing means
44
which is further connected to the electric power supply regulator
12
a
. The non-contact temperature measuring device
42
includes the radiation thermometer
43
and the computing means
44
. The luminance of a thermal radiation light radiated from the heat insulating mold
13
in the vicinity of the melt surface
17
a
is measured using the radiation thermometer
43
. The temperature is computed and detected based on the measured luminance of the thermal radiation light in the computing means
44
. In the electric power supply regulator
12
a
, the quantity of electric power supplied to the heater
12
is regulated based on the computed and detected temperature so as to keep the melt surface
17
a
at a prescribed temperature. As a result, the melt surface
17
a
is kept at a prescribed temperature.
However, in the temperature measurement using the above temperature measuring device
42
, the temperature of the heat insulating mold
13
and that of the melt surface
17
a
have not been the same, as the diameter of the seed crystal
18
and the apparatus for pulling a single crystal
40
have been larger in order to manufacture an LSI more efficiently. As a result, it has been difficult to accurately measure the temperature of the melt surface
17
a
. Since the heat capacity of the melt
17
is relatively large, there is a difference in temperature between the melt
17
in the vicinity of the crucible
11
close to the heater
12
and the melt
17
in the vicinity of the single crystal
18
away from the heater
12
. As a result, it is difficult to accurately measure the required temperature of the melt surface
17
a
in the vicinity of the single crystal
18
. Since convection is caused in the melt
17
by the difference in temperature, the temperature of the melt surface
17
a
easily varies with time. As a result, it is difficult to accurately measure the temperature of the melt surface
17
a
following the variations.
In order to cope with the above problems, it is desirable that the temperature of the melt surface
17
a
in the vicinity of the single crystal
18
be directly measured using the radiation thermometer. Radiation lights having radiants such as the upper portion of the side wall of the crucible
11
, the heater
12
, the heat insulating mold
13
, and the lower chamber's upper wall
14
a
, which surround the melt surface
17
a
and are hot, provide a specular reflection on the melt surface
17
a
. Therefore, even when the temperature of the melt surface
17
a
in the vicinity of the single crystal
18
is directly measured using the radiation thermometer, the radiation lights caused by specular reflection (hereinafter, referred to as the stray lights) are incident on the radiation thermometer, in addition to the thermal radiation light from the melt surface
17
a
itself, so that an error in the measured temperature is easily caused.
In order to reduce the influence of the stray light and improve the measurement precision, various kinds of temperature measuring devices were proposed.
FIG. 2
is a diagrammatic sectional view showing an apparatus
50
for pulling a single crystal incorporating a conventional temperature measuring device
55
(Japanese Kokai No. 58-168927), and reference numeral
14
a
represents a lower chamber's upper wall. A window
19
facing the melt surface
17
a
in the vicinity of a single crystal
18
is formed at a prescribed place on the lower chamber's upper wall
14
a
, and is sealed with a quartz glass member
19
a
or the like.
On the other hand, a polarizing filter
51
and an optical detecting means (silicon electromotive force device)
52
are arranged above the window
19
in a slanting direction on the axis
54
of a radiation light. The optical detecting means
52
is connected through an amplifier
53
to an electric power supply regulator
12
a
. The temperature measuring device
55
includes the polarizing filter
51
, the optical detecting means
52
, and the amplifier
53
.
In the temperature measuring device
55
having the above construction, a stray light component is reject
Maeda Tokuji
Takanashi Keiichi
Hiteshew Felisa
Sumitomo Metal Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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