Title: Heat treatment apparatus and controller for heat treatment apparatus and control method for heat treatment apparatus
Abstract: Temperature control is made without the risk of contaminating object-to-be-processed and with high accuracy. Temperatures are metered out of contact with the objects-to-be-processed, and based on a metered result, estimated temperatures of the objects-to-be-processed are computed. Furthermore, estimation errors of the estimated temperatures are computed to correct the estimated temperatures. Based on a temperature recipe stating relationships between set temperatures and times and the corrected estimated temperatures, a heater is controlled.
Patent Number: 6,847,015 Issued on 01/25/2005 to Wang, et al.
| Inventors:
|
Wang; Wenling (Shiroyama-Machi, JP);
Sakamoto; Koichi (Shiroyama-Machi, JP);
Park; Youngchul (Shiroyama-Machi, JP);
Suzuki; Fujio (Shiroyama-Machi, JP)
|
| Assignee:
|
Tokyo Electron Limited (Tokyo-To, JP)
|
| Appl. No.:
|
963381 |
| Filed:
|
September 27, 2001 |
Foreign Application Priority Data
| Sep 27, 2000[JP] | 2000-295262 |
| Current U.S. Class: |
219/486; 219/494; 219/506; 257/E21.53 |
| Intern'l Class: |
H05B 003/02 |
| Field of Search: |
219/496,483,486,497,492,494,425,505,501,506
392/416
|
References Cited [Referenced By]
U.S. Patent Documents
| 5517594 | May., 1996 | Shah et al. | 392/416.
|
| 5895596 | Apr., 1999 | Stoddard et al. | 219/497.
|
| 6060697 | May., 2000 | Morita et al. | 219/483.
|
| 6175103 | Jan., 2001 | Lam et al. | 219/506.
|
| Foreign Patent Documents |
| 09/007963 | Jan., 1997 | JP.
| |
| 10/335340 | Dec., 1998 | JP.
| |
| 2000/29526 | Jan., 2000 | JP.
| |
| 2000/077345 | Mar., 2000 | JP.
| |
Primary Examiner: Hoang; Tu
Attorney, Agent or Firm: Smith, Gambrell & Russell, LLP
Claims
What is claimed is:
1. A heat treatment apparatus comprising:
a heater for heating an object-to-be-processed;
a temperature meter disposed in the heater;
a temperature estimator for computing an estimated temperature of the
object-to-be-processed, based on a temperature metered result of the
temperature meter;
an error estimator for computing an estimation error of the estimated
temperature computed by the temperature estimator;
a temperature corrector for computing a corrected estimated temperature
given by correcting the estimated temperature computed by the temperature
estimator, based on the estimation error computed by the error estimator;
and
a heating controller for controlling the heater, based on the corrected
estimated temperature computed by the temperature corrector, and a
temperature recipe stating a relationship between a set temperature and a
time.
2. A heat treatment apparatus comprising:
a heater for heating an object-to-be-processed;
a temperature meter disposed in the heater;
a temperature estimator for computing an estimated temperature of the
object-to-be-processed, based on a temperature metered result of the
temperature meter;
an error estimator for computing an estimation error of the estimated
temperature computed by the temperature estimator;
a temperature corrector for computing a corrected estimated temperature
given by correcting the estimated temperature computed by the temperature
estimator, based on the estimation error computed by the error estimator;
a heating controller for controlling the heater, based on the corrected
estimated temperature computed by the temperature corrector, and a
temperature recipe stating a relationship between a set temperature and a
time; and
a computation period determining unit for determining a computation period
for periodically computing the estimated temperature by the temperature
estimator and the estimation error by the error estimator.
3. The heat treatment apparatus according to claim 2, wherein
the computation period determining unit determines the computation period
corresponding to an absolute value of a change rate of the set
temperature.
4. The heat treatment apparatus according to claim 2, wherein
the computation period determined by the computation period determining
unit is an integer time a shortest computation period.
5. The heat treatment apparatus according to claim 4, wherein
the temperature estimator includes a data interpolator for interpolating
data for computing the estimated temperature when the computation period
determined by the computation period determining unit is different from
the shortest computation period.
6. The heat treatment apparatus according to claim 4, wherein
the error estimator includes a data interpolator for interpolating data for
computing the estimation error when the computation period determined by
the computation period determining unit is different from the shortest
computation period.
7. The heat treatment apparatus according to claim 1, wherein
the temperature meter includes a heater vicinity temperature meter for
metering a temperature of a heater vicinity, and an object-to-be-processed
vicinity temperature meter for metering a temperature of an
object-to-be-processed vicinity, and
the temperature estimator computes the estimated temperature of the
object-to-be-processed, based on a control signal for electric power to be
fed to the heater, the heater vicinity temperature metered by the heater
vicinity temperature meter, and the object-to-be-processed vicinity
temperature metered by the object-to-be-processed vicinity temperature
meter.
8. The heat treatment apparatus according to claim 7, wherein
the temperature estimator computes an estimated temperature of the
object-to-be-processed vicinity, based on the control signal for electric
power to be fed to the heater, and the temperature of the heater vicinity
metered by the heater vicinity temperature meter, and
the error estimator computes the estimation error, based on the temperature
of the object-to-be-processed vicinity given by the object-to-be-processed
vicinity temperature meter, the estimated temperature of the
object-to-be-processed vicinity computed by the temperature estimator, and
the temperature change rate of the set temperature.
9. A controller for controlling a heat treatment apparatus comprising a
heater for heating an object-to-be-processed, and temperature meter
disposed in the heater, the controller comprising:
a temperature estimator for computing an estimated temperature of the
object-to-be-processed, based on a temperature metering result of the
temperature meter;
an error estimator for computing an estimation error of the estimated
temperature computed by the temperature estimator;
a temperature corrector for computing a corrected estimated temperature
given by correcting the estimated temperature computed by the temperature
estimator, based on the estimation error computed by the error estimator;
and
a heating controller for controlling the heater, based on the corrected
estimated temperature computed by the temperature corrector.
10. A controller for controlling a heat treatment apparatus comprising a
heater for heating an object-to-be-processed, and a temperature meter
disposed in the heater, the controller comprising:
a temperature estimator for computing an estimated temperature of the
object-to-be-processed, based on a temperature metering result of the
temperature meter;
an error estimator for computing an estimation error of the estimated
temperature computed by the temperature estimator;
a temperature corrector for computing a corrected estimated temperature
given by correcting the estimated temperature computed by the temperature
estimator, based on the estimation error computed by the error estimator;
a heating controller for controlling the heater, based on the corrected
estimated temperature computed by the temperature corrector; and
a computation period determining unit for determining a computation period
for periodically computing the estimated temperature by the temperature
estimator and the estimation error by the error estimator.
11. The controller for controlling a heat treatment apparatus according to
claim 10, wherein
the computation period determining unit determines the computation period
corresponding to an absolute value of a change rate of a set temperature.
12. The controller for controlling a heat treatment apparatus according to
claim 10, wherein
the computation period determined by the computation period determining
unit is an integer time shortest computation period.
13. The controller for controlling a heat treatment apparatus according to
claim 12, wherein
the temperature estimator includes a data interpolator for interpolating
data for computing the estimated temperature when the computation period
determined by the computation period determining unit is different from
the shortest computation period.
14. The controller for controlling a heat treatment apparatus according to
claim 12, wherein
the error estimator includes a data interpolator for interpolating data for
computing the estimation error when the computation period determined by
the computation period determining unit is different from the shortest
computation period.
15. A controller for controlling a heat treatment apparatus comprising a
heater for heating an object-to-be-processed, the controller comprising:
a heating controller for controlling the heater in accordance with a
temperature recipe stating a relationship between a set temperature and a
time; and
a control period determining unit for determining a control period for
periodically controlling the heater by the heating controller, based on a
change rate of the set temperature.
16. A method for controlling a heat treatment apparatus comprising a heater
for heating an object-to-be-processed, the method comprising:
a temperature metering step of metering a temperature in the heater;
a temperature estimating step of computing an estimated temperature of the
object-to-be-processed, based on a temperature metering result of the
temperature metering step;
an error estimating step of computing an estimation error of the estimated
temperature computed in the temperature estimating step;
a temperature correcting step of computing a corrected estimated
temperature given by correcting the estimated temperature computed in the
temperature estimating step, based on the estimation error computed in the
error estimation step; and
a heating control step for controlling the heater, based on the corrected
estimated temperature computed in the temperature correcting step, and a
temperature recipe stating a relation ship between a set temperature and a
time.
17. A method for controlling a heat treatment apparatus comprising a heater
for heating an object-to-be-processed, the method comprising:
a temperature metering step of metering a temperature in the heater;
a temperature estimating step of computing an estimated temperature of the
object-to-be-processed, based on a temperature metering result of the
temperature metering step;
an error estimating step of computing an estimation error of the estimated
temperature computed in the temperature estimating step;
a temperature correcting step of computing a corrected estimated
temperature given by correcting the estimated temperature computed in the
temperature estimating step, based on the estimation error computed in the
error estimation step;
a heating control step for controlling the heater, based on the corrected
estimated temperature computed in the temperature correcting step, and a
temperature recipe stating a relationship between a set temperature and a
time; and
a computation period determining step of determining a computation period
for periodically computing the estimated temperature in the temperature
estimating step and the estimation error computed in the error estimating
step.
18. The method for controlling a heat treatment apparatus according to
claim 17, wherein
the computation period determining step is for determining the computation
period corresponding to an absolute value of a change rate of the set
temperature.
19. The method for controlling a heat treatment apparatus according to
claim 17, wherein
the computation period determined in the computation period determining
step is an integer time shortest computation period.
20. The method for controlling a heat treatment apparatus according to
claim 19, wherein
the temperature estimating step includes a data interpolating step of
interpolating data for computing the estimated temperature when the
computation period determined in the computation period determining step
is different from the shortest computation period.
21. The method for controlling a heat treatment apparatus according to
claim 19, wherein
the error estimating step includes a data interpolating step of
interpolating data for computing the estimation error when the computation
period determined in the computation period determining step is different
from the shortest computation period.
22. The method for controlling a heat treatment apparatus according to
claim 16, wherein
the temperature estimating step includes a heater vicinity temperature
estimating step of metering a temperature of the heater vicinity, and an
object-to-be-processed vicinity temperature metering step of metering a
temperature of the object-to-be-processed vicinity,
the temperature estimating step is for computing the estimated temperature
of the object-to-be-processed, based on a control signal for electric
power to be fed to the heater, the temperature of the heater vicinity
metered in the heater vicinity temperature metering step, and the
temperature of the object-to-be-processed vicinity metered in the
object-to-be-processed vicinity temperature metering step.
23. The method for controlling a heat treatment apparatus according to
claim 22, wherein
the temperature estimating step is for computing the estimated temperature
of the object-to-be-processed vicinity, based on a control signal for
electric power to be fed to the heater, and the temperature of the heater
vicinity metered in the heater vicinity temperature metering step, and
the error estimating step is for computing the estimation error, based on
the temperature of the object-to-be-processed vicinity metered in the
object-to-be-processed vicinity temperature metering step, and the
estimated temperature of the object-to-be-processed vicinity computed in
the temperature estimating step, and a temperature change rate of the set
temperature.
24. A method for controlling a heat treatment apparatus comprising:
a heating control step of controlling the heater in accordance with a
temperature recipe stating a relationship between a set temperature and a
time; and
a control period determining step of determining a control period for
periodically controlling the heater by the heating control step, based on
a change rate of the set temperature.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The subject application is related to subject matter disclosed in Japanese
Patent Application No. 2000-29526 filed on Sep. 27, 2000 in Japan to which
the subject application claims priority under Paris Convention and which
is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat treatment apparatus, a controller
for the heat treatment apparatus and a method for controlling the heat
treatment apparatus, more specifically to a heat treatment apparatus in
which temperatures of objects-to-be-processed can be incontiguously
estimated, and a controller for the heat treatment apparatus and a method
for controlling the heat treatment apparatus.
2. Related Background Art
One apparatus for making heat treatments on objects-to-be-processed, such
as semiconductor wafers (hereinafter called wafers) or others, which is
used in semiconductor device fabrication methods is a vertical heat
treatment apparatus for batch treatment. In this vertical heat treatment
apparatus, a number of wafers are held horizontally in a shelves-like
manner on a holder, such as wafer boat or others, and the holder is loaded
in the vertical heat treatment apparatus for a heat treatment, e.g., CVD
(Chemical Vapor Deposition), oxidation, etc.
To make a heat treatment on the wafers it is necessary to precisely control
temperatures of the wafers. For example, in forming a thin film on the
wafers by, e.g., CVD, a film thickness of the thin film depends on
temperatures of the wafers. Accordingly, the temperature control of the
heat treatment apparatus must be performed with high accuracy.
The heat control has been conventionally made by loading the wafers with
thermocouples into the heat treatment apparatus to meter temperatures of
the wafers.
However, when the wafers with thermocouples are loaded in the heat
treatment apparatus, there is a risk that the metal forming the
thermocouples disperses in the heat treatment apparatus and stays on the
inside of the heat treatment apparatus, with a result that the staying
metal adheres to the wafers, causing metal contamination.
SUMMARY OF THE INVENTION
The present invention was made in view of the above circumstances, and an
object of the present invention is to provide a heat treatment apparatus,
a controller for the heat treatment apparatus and a method for controlling
the heat treatment apparatus which are free from the risk of contamination
of objects-to-be-processed and can control temperatures with high
accuracy.
(1) To attain the above-described object, the heat treatment apparatus
according to the present invention comprises: a heater for heating an
object-to-be-processed; a temperature meter disposed in the heater; a
temperature estimator for computing an estimated temperature of the
object-to-be-processed, based on a temperature metered result of the
temperature meter; an error estimator for computing an estimation error of
the estimated temperature computed by the temperature estimator; a
temperature corrector for computing a corrected estimated temperature
given by correcting the estimated temperature computed by the temperature
estimator, based on the estimation error computed by the error estimator;
and a heating controller for controlling the heater, based on the
corrected estimated temperature computed by the temperature corrector, and
a temperature recipe stating a relationship between a set temperature and
a time.
The temperature meter disposed in the heater meters temperatures, and,
based on a temperature metered result, a temperature of the
object-to-be-processed are estimated. The estimated temperatures are
corrected, based on estimation errors. Consequently, a temperature of the
object-to-be-processed can be accurately estimated.
(2) The controller for controlling a heat treatment apparatus according to
the present invention comprising a heater for heating an
object-to-be-processed, and temperature meter disposed in the heater
comprises a temperature estimator for computing an estimated temperature
of the object-to-be-processed, based on a temperature metering result of
the temperature meter; an error estimator for computing an estimation
error of the estimated temperature computed by the temperature estimator;
a temperature corrector for computing a corrected estimated temperature
given by correcting the estimated temperature computed by the temperature
estimator, based on the estimation error computed by the error estimator;
and a heating controller for controlling the heater, based on the
corrected estimated temperature computed by the temperature corrector.
(3) The controller for controlling a heat treatment apparatus comprising a
heater for heating an object-to-be-processed comprises a heating
controller for controlling the heater in accordance with a temperature
recipe stating a relationship between a set temperature and a time; and a
control period determining unit for determining a control period for
periodically controlling the heater by the heating controller, based on a
change rate of the set temperature.
Periods of the control are changed, based on change rates of a set
temperature, whereby both accuracy and efficiency of the control can be
considered.
(4) The method for controlling a heat treatment apparatus comprising a
heater for heating an object-to-be-processed comprises a temperature
metering step of metering a temperature in the heater; a temperature
estimating step of computing an estimated temperature of the
object-to-be-processed, based on a temperature metering result of the
temperature metering step; an error estimating step of computing an
estimation error of the estimated temperature computed in the temperature
estimating step; a temperature correcting step of computing a corrected
estimated temperature given by correcting the estimated temperature
computed in the temperature estimating step, based on the estimation error
computed in the error estimation step; and a heating control step for
controlling the heater, based on the corrected estimated temperature
computed in the temperature correcting step, and a temperature recipe
stating a relation ship between a set temperature and a time.
The temperature meter disposed in the heater meters temperatures, and,
based on temperature metered results, temperatures of the
object-to-be-processed are estimated, and the estimated temperatures are
corrected based on estimation errors. The heater is controlled, based on
the corrected estimated temperatures. Consequently, the heater can be
controlled based on the estimated temperatures of the
object-to-be-processed computed with good accuracy.
(5) The method for controlling a heat treatment apparatus comprises a
heating control step of controlling the heater in accordance with a
temperature recipe stating a relationship between a set temperature and a
time; and a control period determining step of determining a control
period for periodically controlling the heater by the heating control
step, based on a change rate of the set temperature.
Periods of the control are changed, based on change rates of a set
temperature, whereby both accuracy and efficiency of the control can be
considered.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial sectional view of the heat treatment apparatus
according to the present invention, which shows a structure thereof.
FIG. 2 is perspective views of the heat treatment apparatus according to
the present invention, which show the structure thereof.
FIG. 3 is a block diagram of the controller of the heat treatment apparatus
according to the present invention.
FIG. 4 is a flow chart of a control procedure of the controller.
FIG. 5 is a table which is one example of the temperature recipe.
FIG. 6 is a graph which is another example of the temperature recipe.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(A First Embodiment)
The vertical heat treatment apparatus according to a first embodiment of
the present invention will be explained.
FIGS. 1 and 2 are respectively a partial sectional view and perspective
views of the vertical heat treatment apparatus according to the present
embodiment.
The vertical heat treatment apparatus according to the present embodiment
comprises a reaction tube 2 of the double-tube structure of an inner tube
2a and an outer tube 2b which are formed of, e.g., quartz, and a
cylindrical manifold 21 of metal disposed on the bottom of the reaction
tube 2.
The inner tube 2a has the top uninterrupted and is supported on the inside
of the manifold 21. The outer tube 2b has the top interrupted and has the
lower end connected air-tightly to the upper end of the manifold 21 below
a base plate 22.
As shown in FIG. 2, in the reaction tube 2, a number of
objects-to-be-processed, semiconductor wafers W are held on a holder, a
wafer boat 23 horizontally and vertically spaced from each other in a
shelves-like manner. The wafer boat 23 is retained on a lid 24 through a
heat insulation cylinder (heat insulator) 25.
A heater 3 for heating the wafers W, objects-to-be-processed is disposed
around the reaction tube 2, and the heater 3 is in the form of, e.g.,
resistance heaters. The heater 3 is divided in zone 1 to zone 5. The
respective heaters 31-35 can have calories controlled independent of each
other. Electric power controllers 41-45 have respective electric power
sensors S1p-S5p for metering thermal powers of the respective heaters
31-35.
Inside temperature sensors S1in-S5in in the form of thermocouples or others
as an objects-to-be-processed vicinity temperature meters are disposed on
the inside wall of the inner tube 2a corresponding to the zones 1-5 of the
respective heaters 1-5. Outside temperature sensors S1out-S5out in the
form of thermocouples or others as a heater vicinity temperature meters
are disposed on the outside wall of the outer tube 2b corresponding to the
zones 1-5 of the respective heaters 31-35.
Monitor wafers W1-W5 are mounted at positions corresponding to the zones
1-5 of the respective heaters 31-35. As will be described later,
temperatures of the monitor wafers W1-W5 are estimated, based on metered
signals of the temperature sensors Sin (S1in-S5in), Sout (S1out-S5out) and
the electric power sensors Sp(S1p-S5p).
The manifold 21 has a plurality of gas feed pipes for feeding gases into
the inner tube 2a. In FIG. 1, two gas feed pipes 51, 52 are shown for the
convenience of the description. Flow rate controllers 61, 62, such as mass
flow controllers or others, for controlling respective gas flow rates, and
valves (not shown) are inserted in the gas feed pipes 51, 52.
The manifold 21 is connected to an exhaust pipe 27 for exhausting the gases
through a gap between the inner tube 2a and the outer tube 2b. The exhaust
pipe 27 is connected to a vacuum pump. A pressure adjuster 28 including a
butterfly valve and a valve operator, for adjusting pressures in the
reaction tube 2 is inserted in the exhaust pipe 27.
The vertical heat treatment apparatus comprises a controller 100 for
controlling treatment parameters, such as temperatures of a treatment
atmosphere in the reaction tube 2, pressures in the reaction tube 2 and
gas flow rates. The controller 100 receives metered signals of the
electric power sensors Sp (S1p-S5p) and the temperature sensors Sin
(S1in-S5in), Sout (S1out-S5out) and outputs control signals to the
electric power controllers 41-45 of the heater 3, a pressure adjuster 28
and flow rate adjusters 61, 62.
Then, the controller 100 will be described in good detail.
FIG. 3 is a block diagram of a part of an internal structure of the
controller 100, which is involved in the control of the heater 3.
As shown in FIG. 3, the controller 100 comprises an A/D (Analog/Digital)
converter 110 which converts analog metered signals of the electric power
sensors Sp and the temperature sensors Sout, Sin to digital metered
signal; a temperature estimator 120 which computes estimated temperatures
of wafers; an error estimator 130 which computes estimation errors
.DELTA.T of the wafer estimated temperatures T' computed by the
temperature estimator 120; an adder 140 as a temperature corrector which
adds the computed estimated temperatures T' and the estimation errors
.DELTA.T to each other to compute corrected estimated temperatures T" of
the wafers; a temperature recipe storage 150 which stores a temperature
recipe stating relationships between set temperatures and times for a heat
treatment of the wafers; a heating controller 160 which outputs electric
power control signals P' to the electric power controllers 41-45, based on
the corrected estimated temperatures T" and the set temperatures Tsp set
on the temperature recipe stored in the temperature recipe storage 150;
and a computation period determining unit which determines a computation
period ts for the computation of the temperature estimator 120 and the
error estimator 130.
The temperature estimator 120 includes a first data interpolator 122 for
interpolating data necessary to compute estimated temperatures T' of the
wafers W corresponding to a computation period ts, and a temperature
estimation model module 124 which computes estimated temperatures T' of
the wafers. The error estimator 130 includes a second data interpolator
132 which interpolates data necessary to compute estimation errors
.DELTA.T of the estimated temperatures of the wafers W, and an error
estimation model module 134 which computes estimation errors .DELTA.T of
the estimated temperatures of the wafers.
FIG. 4 is a flow chart of a control procedure of controlling the heater 3.
The procedure of the temperature control will be explained with reference
to FIG. 4.
(A) The computation period determining unit 170 determines a computation
period ts, based on a change ratio RR of a set temperature Tsp stated in a
temperature recipe stored in the temperature recipe storage 150 (S11).
A computation period ts is set corresponding to a change ratio RR of a set
temperature, i.e., a change ratio of a wafer temperature, whereby the
computing and the control devices can be effectively used. That is, when a
change ratio RR of a set temperature Tsp is small, a computation interval
can be large, which allows the computing or control elements, such as CPU
(Central Processing Unit) not shown to be used for other processing. On
the other hand, when a change ratio RR of a set temperature is large,
estimated temperatures, etc. of the wafers are computed by a short
computation period, and temperatures of the wafers can be accordingly
precisely controlled.
The temperature recipe stored in the temperature recipe storage 150 shows
relationships between set temperatures Tsp, i.e., target temperatures of a
heat treatment for the wafers W, and time. FIGS. 5 and 6 show examples of
the temperature recipe.
FIG. 5 shows a table expressing set temperatures Tsp (Set Point) and change
rate RR of the set temperatures Tsp corresponding to sections of a time.
FIG. 6 is a graph expressing the set temperatures Tsp and the sections of
a time.
FIGS. 5 and 6 are different from each other in the forms and express the
same temperature recipe. From a time t0 to a time t1, a set temperature is
kept constant at 300.degree. C., and from a time t1 to a time t2, the set
temperature Tsp changes from 300.degree. C. to 310.degree. C. at a
10.degree. C./min change rate. From a time t2 to a time t3, the set
temperature Tsp changes respectively from 310.degree. C. to 350.degree.
C., from 350.degree. C. to 400.degree. C. and from 400.degree. to
500.degree. C. respectively at a 20.degree. C./min change rate RR, a
50.degree. C./min change rate RR and a 100.degree. C./min change rate RR.
From a time t5 to a time t6, the set temperature is kept constant at
500.degree. C. From a time t6 to a time t7, from a time t7 to a time t8
and from a time t8 to a time t9, the set temperatures lower respectively
from 500.degree. C. to 400.degree. C., from 400.degree. C. to 350.degree.
C. and from 350.degree. C. to 300.degree. C. respectively at a
-100.degree. C./min change rate, a -50.degree. C./min change rate and a
-10.degree. C./min change rate. From a time t9 later, the set temperature
is kept constant at 300.degree. C.
FIGS. 5 and 6 are substantially the same, and either of the forms may be
used in practicing the present invention. In other words, the temperature
recipe may be expressed in any form which can give set temperatures Tsp
and change rates RR of the set temperatures corresponding to times.
Based on change rates RR of set temperatures, computation periods ts are
determined. One example of the method for determining set temperatures is
expressed by the following formulae (1) to (4).
ts=0.5[sec](.vertline.RR.vertline..gtoreq.50[.degree. C./min]) (1)
ts=1.0[sec](25.ltoreq..vertline.RR.vertline.<50[.degree. C./min]) (2)
ts=2.0[sec](20.ltoreq..vertline.RR.vertline.<25[.degree. C./min]) (3)
ts=4.0[sec](0.ltoreq..vertline.RR.vertline.<10[.degree. C./min]) (4)
Formula (1) gives a shortest computation period .DELTA.t=0.5 sec when a
change rate RR of a set temperature is above 50.degree. C./min including
50.degree. C./min. The computation period ts changes from 0.5 sec to 4.0
sec, becoming smaller as a change rate of an absolute value of a set
temperature becomes larger.
In the example shown by Formulae (1) to (4), computation periods ts have
values given by multiplying a shortest computation period by powers of 2.
However, a computation period ts may be integer times a shortest
computation period .DELTA.t.
(B) The data interpolator 122 judges whether or not a computation period ts
is equal to a shortest computation period .DELTA.t (S12).
When the judgement is YES, the temperature estimation model module 124
computes an estimated temperatures T' of the wafers (S13). When the
judgement is NO in S12, the data interpolator 122 interpolates data
necessary for the computation of the temperature estimation (S14). The
temperature estimation model module 124 computes an estimated temperature
T' (S13).
To compute an estimated temperatures T of the wafers, digital signal
outputs of the A/D converter 110, which include wafer vicinity
temperatures Tin (Tl1n-T5in), heater vicinity temperatures Tout
(T1out-T5out) and heat powers of the haters (P1-P5) (control signals of
the controller 100 for the electric power controllers 41-45), are used.
The A/D converter 110 periodically converts analog signal inputs to
digital signal outputs to output the digital signals. To effectively use
the computing and control devices including the A/D converter 110 it is
preferable that a sampling interval agrees with a shortest computation
period .DELTA.t.
1) Here, the temperature estimation in S13 will be detailed.
Here, estimated wafer temperatures T' (estimated central temperatures Tc'
(Tc1'-Tc5') in a vicinity of the centers of the wafers), estimated edge
temperatures Te' in a vicinity of the edges of the wafers (Te1'-Te5') and
estimated wafer vicinity temperatures Tin' (Tin1'-Tin5') are calculated,
based on wafer vicinity temperatures Tin, heater vicinity temperatures
Tout and heat powers of the haters (P1-P5) (control signals of the
controller 100 for the electric power controllers 41-45). The subscripts 1
to 5 correspond respectively to zones 1 to 5.
y(k)=-a1.multidot.y
(k-1)-a2.multidot.y
(k-2)-a3.multidot.y
(k-3)- . . . -ai.multidot.y
(k-i)- . . . -a16.multidot.y
(k-16)+b1.multidot.u
(k-1)+b2.multidot.u
(k-2)+b3.multidot.u
(k-3)+ . . . +bi.multidot.u
(k-i)+ . . . +b16.multidot.u
(k-16)+w(k) (5)
wherein y(k) is an output vector after one period (.DELTA.t[sec] later);
y(k-1) is a current output vector; y(k-i) is an output vector before (i-1)
period (before (i-1).multidot..DELTA.t[sec]); u(k-1) is a current input
vector; u(k-i) is an input vector before (i-1) period (before
(i-1).multidot..DELTA.t[sec]), and w(k) is a noise vector (white noise).
Vectors u(k-i), y(k-i) and w(k) are specifically expressed by the following
formulae (6) to (8).
##EQU1##
w(k)=(w1(k), w2(k), . . . , w15(k)) (8)
Formula (5) is a 16 dimension-parametric model, and computes an output
vector y(k) after one period, based on a current and a past input vectors
u(k-i) and a current and a past output vectors y(k-i).
An output vector y(k) after one period is used as a current value y(k-1) of
an output vector upon the next computation (at which 1 is added to k).
When an input vector u(k-1) is known, an output vector y(k) after one
period can be sequentially computed.
That is, estimated wafer central temperatures Tc' (T1c'-T5c'), estimated
wafer edge temperatures Te' (T1e'-T5e') and estimated wafer vicinity
temperatures Tin' (T1in'-T5in') can be computed based on heat powers P
(P1-P5) of the haters, heater vicinity temperatures Tout (T1out-T5out) and
wafer vicinity temperatures Tin (T1in-T5in).
The estimated wafer vicinity temperatures Tin' are computed for the error
estimation in the later step S16. When the error estimation is
unnecessary, the output vector y(k-i) may not include an estimated wafer
vicinity temperatures Tin' as in the following Formula (9).
##EQU2##
In this case, both estimated wafer temperatures T' and estimated wafer
vicinity temperatures Tin' are computed by one model but may be computed
respectively by respective models. For example, estimated wafer
temperatures T' are computed by a model using the following formulae (10)
to (13), and estimated wafer vicinity temperatures Tin' are computed by a
model using the following formulae (14) to (17).
##EQU3##
##EQU4##
##EQU5##
w1(k)=(w11(k), . . . , w116(k)) (13)
##EQU6##
##EQU7##
y2(k-i)=T1in', . . . , T5in') (16)
w2(k)=(w21(k), . . . , w216(k)) (17)
Parameters a1-a16, b1-b16 of Formula (5) and etc. and a noise vector w(k)
are determined in advance before an output vector y(k) is computed.
To determine parameters a1-a16, b1-b16, a noise vector w(k), subspace
method or Auto-Regressive Exogeneous Model (hereinafter called ARX model)
can be used.
Specifically, data, such as metered signals of the temperature sensors
S1in-S5in, s1out-S5out and real metered temperatures of the monitor wafers
W1-W5 (temperature sensors, such as thermocouples are mounted on the
monitor wafers) are inputted to, e.g. software Matlab (produced by The
Math Works, Inc., marketed by Cybernet System Kabushiki Kaisha) to
inversely compute the parameters a1-a16, b1-b16, and the noise vector
w(k).
A plurality of combinations of the given parameters a1-a16, b1-b16 and the
noise vector w(k) are usually available. Out of the plural combinations,
one in which the estimated temperatures T1'-T5' given by Formula (5) well
agree with the actually metered temperatures of the monitor wafers is
selected (Model appreciation).
Dimensions of the model are usually large, and dimensions are suitably
reduced to make the model of 16 dimensions.
2) Next, the data interpolating step (S14) will be explained.
When a computation period ts is equal to a shortest computation period
.DELTA.t, a value of the output vector y(k-1) computed before can be
substituted as it is into Formula (5). However, when a computation period
ts is different from (larger than) the shortest computation period
.DELTA.t, the data is insufficient to be substituted as it is into Formula
(5) or others. Then, the data must be interpolated.
Here, it is assumed that a computation period ts is n-times a shortest
computation period: t (ts=n.multidot..DELTA.t). In this case, the
computation of an output vector y(k) by Formula (5) is performed every
n-shortest computation periods. That is, only when k=n.multidot.m in
Formula (5), the computation is performed (m: an integer).
When n=4, for example, k is given by Formula (18). The data of the output
vector with, e.g., k=1 to 3 and 5 to 7 must be interpolated.
k=0, 4, 8, 12, 16, . . . (18)
In Formula (5), when k=n.multidot.m, an output vector y(k) computed
immediately before is k=n.multidot.(m-1), and an output vector y(k)
computed next immediately before is k=n.multidot.(m-2). In such case, the
following interpolation is performed.
(1) Data interpolation between k=n.multidot.m and k=n.multidot.(m-1)
First, an interpolation for an output vector between k=n.multidot.m and
k=n.multidot.(m-1) will be explained. Output vectors y(k) for
k=(n.multidot.m-1), (n.multidot.m-2), . . . , (n.multidot.(m-1)+1) must be
given. All the output vectors can have a value of the immediately before
computed output vector (n.multidot.(m-1)) as expressed by the following
Formula (19).
##EQU8##
(2) Data interpolation between k=n.multidot.(m-1) and k=n.multidot.(m-2)
output vectors
An output vector between k=n.multidot.(m-1) and k=n.multidot.(m-2) can be
an interpolated value between an output vector y(n.multidot.(m-1))
computed immediately before and an output vector y(n.multidot.(m-2)
computed next immediately before. As exemplified by the following Formula
(20), the interpolation can use linear approximation between the
immediately before output vector y(n.multidot.(m-1)) and the next
immediately before output vector y(n.multidot.(m-2)).
##EQU9##
As the interpolation, various interpolations, such as parabolic
approximation beside the linear approximation expressed by Formula (20)
can be used.
The data interpolation between k=n.multidot.m and k=n.multidot.(m-1) can be
made by interpolations besides the interpolation expressed by Formula (19)
(a computed value of an output vector y(k) computed immediately before).
For example, extrapolation maybe used, based on a value of an output
vector computed immediately before and a value of an output vector next
immediately before.
The following Formula (21) exemplifies linear extrapolation using values of
output vectors computed immediately before and next immediately before.
##EQU10##
(3) Data interpolation before k=n.multidot.(m-2)
A value of an output vector y(k-i) before k=n.multidot.(m-2) may be value
of the value of the output vector y(k-i) used in computing the output
vector y(k) immediately before.
Data are thus interpolated by using Formulae (20) and (21) for the
temperature estimation.
In the above-described interpolation, when a computation period is switched
from a shorter computation period to a longer computation period, an
output vector y(k-i) computed in the shorter computation period can be
used in the computation of Formula (5) early after the switch of the
computation period. In short, when a suitable value of the output vector
y(k-i) is available, the value is used, and when a suitable value is
unavailable, the interpolation is performed by an interpolation or an
extrapolation to give a current or a past output vector.
(C) It is judged whether or not a computed period is equal to a shortest
computation period (S15), and when the judgement is YES, estimation errors
.DELTA.T of wafer temperatures are computed (S16). When the judgement in
S15 is NO, data necessary for the computation of the temperature
estimation are interpolated (S17), and then estimation errors .DELTA.T are
computed (16).
The error estimation in S15 will be detailed.
The error estimation is for estimating differences between values of
estimated wafer temperatures T' (Tc', . . . , Te') and actually metered
temperatures T (Tc, . . . , Te). That is, idealistically, estimation
errors .DELTA.T (central estimation errors .DELTA.Tc in a vicinity of the
centers of the wafers and edge estimation errors .DELTA.Te) are expressed
by the following Formula (22).
.DELTA.T=T-T' (22)
Actual temperatures T of the wafers are not actually metered, and
estimation errors .DELTA.T of the wafers must be estimated, based on
relationships with other parameters. As such parameter, estimated wafer
vicinity temperatures Tin' and actually metered wafer vicinity
temperatures Tin can be used. Here, an estimated wafer vicinity estimation
error .DELTA.Tin can be given by the following Formula (23).
.DELTA.Tin=Tin-Tin' (23)
It is considered that temperatures of the wafers themselves and
temperatures in the vicinity of the wafers have close relationships with
each other. Empirically, estimation errors .DELTA.T have values related
with vicinity estimation errors .DELTA.Tin. Accordingly, a model is
prepared to thereby compute estimation errors .DELTA.T of the wafers,
based on vicinity estimation errors .DELTA.Tin. Change rates RR of set
temperatures have close relationship with estimation errors .DELTA.T of
the wafers, and are taken into consideration.
Finally, estimation errors .DELTA.T of the wafers are computed, based on
vicinity estimation errors .DELTA.Tin and change rates RR of set
temperatures.
To compute estimation errors in S16, a parameter model expressed by the
following Formula (24) which is substantially the same as Formula (5) can
be used.
##EQU11##
wherein y(k) is an output vector after one period (.DELTA.t[sec] later);
y(k-1) is a current output vector; y(k-i) is an output vector before (i-1)
period ((i-1).multidot..DELTA.t[sec] before); u(k-1) is a current input
vector; u(k-i) is an input vector before (i-1) period
((i-1).multidot..DELTA.t[sec]); and w(k) is a noise vector (white noise),
which are substantially the same as those in Formula (5).
However, vectors u(k-i), y(k-i) and w(k) are specifically expressed by the
following Formulae (25) to (27), which are different from those of Formula
(5).
u(k-i)=(.DELTA.T1in, .DELTA.T2in, . . . , .DELTA.T5in, RR) (25)
y(k-i)=(.DELTA.T1c, .DELTA.T2c, . . . , .DELTA.T5c, .DELTA.T1e, .DELTA.T2e,
. . . , .DELTA.T5e) (26)
.DELTA.w(k)=(.DELTA.w1(k), . . . , .DELTA.w15(k)) (27)
Formula (24) is a 16 dimension-parametric model, as is Formula (5). When an
input vector is known, an output vector y(k) after one period can be
sequentially computed. For this computation, parameters a0-a15, b0-b15,
and a noise vector .DELTA.w(k) can be determined by subspace method or ARX
model, as can be used in Formula (5).
The data interpolating step (S17) can be carried out by an interpolation
and an extrapolation substantially in the same way as in S14. The
interpolation and the extrapolation are not detailed not to repeat their
explanation.
D) Temperature correction is performed, based on a temperature estimation
result of S13 and a result of the error estimation in S16 (S18).
Corrected estimated temperatures T" can be given by adding estimation
errors .DELTA.T to estimated temperatures T' of the wafers by the adder
140 as the corrector as expressed by Formulae (28) and (29).
Tic"=Tic'+.DELTA.Tic(i=1-5) (28)
Tie"=Tie'+.DELTA.Tie(i=1-5) (29)
Resultantly, temperatures of the wafers can be more correctly estimated.
(E) The heater is controlled based on corrected estimated temperatures T"
(S19).
The heater controller 160 compares corrected estimated temperatures T" with
a set temperature Tsp to determined suitable heat powers P1'-P5' to the
heaters 31-35.
For example, powers of the heaters 31-35 can be determined corresponding to
differences between corrected estimated temperatures T" and a set
temperature Tsp. This control is made corresponding to a computation
period ts determined by the computation period determining unit 170.
(Other Embodiments)
The above-described embodiments of the present invention can be expanded
and modified in the scope of the technical idea of the present invention.
The heat treatment apparatus according to the present invention does not
essentially include both of the computation period determining unit and
the temperature estimator, and may include either of them. For example,
the computation period determining unit can be used to actually meter
wafer temperatures, and in this case, the temperature control is
effectively performed, based on computation periods determined by the
computation period determining unit.
The model is not essentially the parameter model expressed by Formula (5)
and may be other suitable models. Dimensions of the model are not
essentially 16 and may be 8, 20 or others.
The heater may not be divided and is not essentially divided in 5 sections.
The heat treatment apparatus according to the present invention is not
essentially a vertical heat treatment apparatus or of the batch-type, and
may be of sheet-type for making a heat treatment on wafers sheet by sheet.
As described above, according the present invention, temperatures of
objects-to-be-processed can be estimated with good accuracy.
*
