Data processing: structural design – modeling – simulation – and em – Simulating nonelectrical device or system
Reexamination Certificate
1999-08-09
2004-03-23
Jones, Hugh (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating nonelectrical device or system
C700S031000, C703S002000, C703S007000
Reexamination Certificate
active
06711531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus such as an electric furnace, a gas furnace, a steam furnace, etc., and more particularly to a temperature control simulation method and apparatus for developing a temperature control algorithm and learning a temperature control manipulation process in such a process apparatus without using an actual furnace.
2. Description of the Related Art
A temperature control simulation in a semiconductor manufacturing apparatus using an electric furnace is known.
FIG. 32
is a block diagram which shows an electric furnace of a vertical diffusion apparatus used as a semiconductor manufacturing apparatus. The electric furnace system, as illustrated in
FIG. 32
, includes a heater
1101
for heating a furnace, a heater thermo-couple
1102
for detecting the temperature of the heater
1101
, a cascade thermo-couple
1105
for detecting the temperatures of intermediate portions between a uniform heating tube
1103
and a reaction tube
1104
, a boat
1106
mounted thereon with a wafer to be heat-treated, and a temperature controller
1107
for calculating a quantity of manipulation (i.e., a value of electric power) Z applied to the heater
1101
based on the detected temperatures of the heater thermo-couple
1102
and the cascade thermo-couple
1105
and a preset temperature Y.
Heater
1101
is divided into a plurality of zones to control the furnace temperature with higher accuracy, and for instance, in the case of a four-zone division, the divided zones are sequentially called a U, CU, CL and L zone, etc., in order from top to bottom.
The heater thermo-couple
1102
and the cascade thermo-couple
1105
are disposed in each divided zone, and the quantity of manipulation Z given to the heater
1101
is calculated by an algorithm (e.g., PID arithmetic operations, etc.) in the temperature controller
1107
to adjust the value of electric power supplied to the heater
1101
while detecting the temperature of the heater thermo-couple
1102
. This adjusts the detected temperature of the cascade thermo-couple
1105
to the set temperature Y.
Also, the boat
1106
having a wafer to be heat-treated, is inserted into the furnace, and is withdrawn after the wafer has been heat-treated. Subsequently, a new wafer to be heat treated is mounted on the boat
1106
, which is again inserted into the furnace for heat treatment.
In the case of the vertical diffusion apparatus having an electric furnace as shown in
FIG. 32
, a process shown in FIGS.
33
(
a
) and
33
(
b
) is performed.
FIG.
33
(
a
) shows a flow chart for one example of a treatment process performed by the vertical diffusion apparatus, and FIG.
33
(
b
) schematically shows a temperature change in the furnace during the process treatment.
Step S
1
is a process in which the furnace temperature is settled or stabilized at a comparatively low temperature T
0
. In step S
1
, the boat
1106
has not yet been inserted into the furnace.
Step S
2
is a process (boat loading) in which the boat
1106
is inserted or loaded into the furnace.
As the temperature of the wafer is usually lower than the target temperature T
0
, the temperature in the furnace temporarily falls below the target temperature T
0
as a result of the boat loading.
A quantity of manipulation to the heater is adjusted by the temperature controller
1107
to allow the furnace temperature to quickly recover from this temperature fall, and to stabilize it at the target temperature T
0
within a slight temperature-variation range.
Step S
3
is a process (e.g., ramp up) in which the temperature in the furnace is gradually raised or ramped up from the first target temperature T
0
to a second target temperature T
1
where the wafer is subjected to a process treatment such as layer-forming or deposition processing, etc.
When ramped up, the temperature in the furnace will rise in a delayed manner with respect to a target temperature, so a time period is required until the furnace temperature has been stabilized at the target temperature T
1
within a slight temperature range.
Step S
4
is a process in which the temperature in the furnace is stabilized at the target temperature T
1
so as to subject the wafer to a treatment process.
Step S
5
is a process in which the temperature in the furnace is gradually lowered from the second target temperature T
1
to the comparatively low first target temperature T
0
.
Step S
6
is a process in which the boat with the mounted wafer which has been subjected to the treatment process and is pulled out of the furnace.
Since steps S
1
to S
6
are repeated, performing each step in a shortened time leads to an improvement in productivity. In particular, regarding temperature control performance, it is necessary to shorten the time (settling time) required to settle or stabilize the furnace temperature at the target temperature, within a slight temperature range after loading of the boat with the wafer and ramping up the furnace temperature.
Therefore, for shortening the settling time during the boat loading and the furnace temperature ramp-up operation, as well as for conducting maintenance, design engineers for the semiconductor manufacturing apparatus and workers at the semiconductor manufacturing sites frequently must operate or manipulate the temperature controller while monitoring the temperature in the furnace.
The development of the temperature control algorithm and learning the temperature control operation have been accomplished by performing the process treatment as shown in FIG.
33
(
a
) so as to control the temperature while using the apparatus shown in FIG.
32
.
However, the apparatus of
FIG. 32
is very expensive, requires a large installation space, and is dangerous because of the very high target temperatures at T
0
and T
1
ranging from about 300 degrees C. to about 500 degrees C. for T
0
and from about 800 degrees C. to 1200 degrees C. for T
1
. In addition, some apparatuses use poisonous gases, so it is essential to carefully manage temperature control. Moreover, it requires more than about 3 to 6 hours to perform steps S
1
through S
6
. Therefore, a method of reducing the costs and shortening the operating time is required.
SUMMARY OF THE INVENTION
In view of the foregoing and other problems, disadvantages, and drawbacks of the conventional process apparatus, the present invention has been devised, and it is an object of the invention to provide a temperature control simulation method and apparatus which can form, on a computer, a temperature simulation model for a process apparatus, such as an electric furnace, a gas furnace, a steam furnace, etc., which shows substantially the same temperature change as in an actual furnace. Thus, one may develop a temperature control algorithm and/or learn a temperature control manipulation method without using the actual furnace.
To achieve the above object, according to one aspect of the present invention, there is provided a temperature control simulation method in which transfer function means, representative of a relationship between an input to a heater and a temperature output thereof, is determined so that temperature control on a heating furnace can be performed by using the thus determined transfer function mechanism as that of a temperature system simulation device.
In a preferred form of the temperature control simulation method of the invention, the transfer function means comprises a heater system transfer function and a furnace system transfer function. By approximating each of these transfer functions as K·exp(−Ls)/(1+Ts), a total transfer function for the entire system is given by the following formula:
K
1
·exp(−
L
1
s
)/(1
+T
1
s
)×
K
2
·exp(−
L
2
s
)/(1
+T
2
s
) (1)
where K is a gain, T is a time constant, L is a delay, suffix
1
indicates the heater system, and suffix
2
indicates a parameter of the furnace system.
Thus, the temperature control simulation for the heating furnace is obtained by using the total transfer funct
Tanaka Kazuo
Urabe Kenzo
Yamaguchi Hideto
Ferris Fred
Jones Hugh
Kokusai Electric Co. Ltd.
McGinn & Gibb PLLC
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