JP2001075605A - Feedback controller and semiconductor manufacturing device and method for controlling temperature therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the over (under) shoot of feedback control. SOLUTION: A feedback controller for controlling a heater 21 of a heat treatment furnace 20 is provided with a temperature sensor 22, a subtracting part 23, a controlling part 24, a heater driving device 25, and a target value setting part 26, and the controlling part 24 is provided with a PD arithmetic part 31, an integration arithmetic part 32, an adding part 33, a first output limiting part 34, a second output limiting part 35, and an integration suppressing part 36. When a control signal from the adding part 33 is 0-3% of an allowable output range, that is, 'capability to decrease the temperature of the heater is small', the surplus integration of the integration arithmetic part 32 is prevented by the integration suppressing part 36. Therefore, the surplus integration can be prevented so that the controlled variable (temperature) can be quickly and exactly changed to a target value, and that the oversheet or undershoot of the temperature of the heat treatment furnace can be reduced. Thus, the quality of the heat treatment, the reliability, and manufacture yield of the devices can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback control technique, and more particularly to a feedback control technique for generating a control signal by integrating a deviation between a control amount of a control target and a target value. The present invention relates to technology that is effective for use in manufacturing equipment.

[0002]

2. Description of the Related Art Generally, in a semiconductor manufacturing apparatus provided with a heat treatment furnace such as a diffusion device or a thermal CVD device (hereinafter, referred to as a heat treatment device), a heater for heating the heat treatment furnace is feedback-controlled by a feedback control device. The temperature of the heat treatment furnace is made to precisely follow a specified temperature sequence.

As shown in FIG. 1, a feedback control device generally used in a heat treatment apparatus corresponds to a temperature (a control amount) of a heater 1 of a heat treatment furnace to be controlled.
Hereinafter, the same applies in parentheses. ) Is provided with a temperature sensor (measurement unit) 2 such as a thermocouple for measuring the actual temperature of the heat treatment furnace, and the temperature sensor 2 transmits the measured temperature (measured amount) to the control unit 4 via the subtraction unit 3. Connected to get. The control unit 4 is connected with a heater driving device (operation unit) 5 for applying electric power (operation amount) to the heater 1.
Is connected to a setting unit 6 for setting a target temperature (target value).

The subtractor 3 and the controller 4 output, for example, by PID calculation, a control output signal that makes the deviation between the measured temperature measured by the temperature sensor 2 and the target temperature from the setting unit 6 zero, and the heater It is given to the driving device 5. The heater driving device 5 supplies electric power proportional to the control output signal to the heater 1.
Output to In this way, the closed loop control (feedback control) for matching the temperature in the heat treatment furnace heated by the heater 1 to the target temperature is performed.

[0005] When actually performing feedback control of the heater of the heat treatment apparatus, it is necessary to set an upper limit and a lower limit to the electric power of the heater driving device 5 due to restrictions such as cost and safety. Therefore, in a conventional feedback control device of a heat treatment apparatus, an output limiting unit (limiter) is provided in the control unit.

On the other hand, since the configuration is simple, the control rules are easily understood intuitively, and a desired control performance is provided, PID calculation is employed as a control signal calculation method. Then, as represented by the PID calculation, in the feedback control device, the integral (I) calculation is widely used in order to eliminate the deviation between the target value and the control amount.

In the case where the integral operation is used as described above, for example, if the target value is changed or a large disturbance is applied to the control amount, the operation result of the control output signal becomes P
In the case of the ID operation, the value becomes extremely large or small due to the influence of the P (proportional) operation and the D (differential) operation. When the control section of the feedback control device is provided with an output limiting section, a mismatch between the calculated control signal and the actually output control output signal occurs, causing over-integration. The so-called reset windup phenomenon in which the (overshoot) amount or the undershoot amount becomes large easily occurs.

Therefore, conventionally, in a feedback control device using an integration operation, a countermeasure against the reset windup phenomenon is taken by employing the control unit 10 shown in FIG. That is, the control unit 10 shown in FIG.
2, adder 13, output limiter 14, and integration suppressor 15
And is configured to prevent excessive integration by the following operation.

The difference between the control value and the target value obtained by the subtractor 3 is calculated by the PD calculator 11 and the integral calculator 1.
2 and the adder 13 perform PDI calculation, and the calculation result is output as a control output signal through the output limiter 14. The integration suppressing unit 15 compares the input value and the output value of the output limiting unit 14, and when the input value and the output value are different, that is, the result of the PID operation exceeds the allowable value range set in the integration suppressing unit 15. At times, the integral operation of the integral operation unit 12 is stopped. Excessive integration is prevented by the integration calculation stopping process of the integration suppressing unit 15.

Japanese Patent Application Laid-Open No. HEI 6-168004 discloses a feedback control device that includes an integral suppression unit to prevent excessive integration.

[0011]

For example, in a heat treatment apparatus, it is necessary to raise the temperature of the heat treatment furnace as quickly as possible by a high temperature of about 300 ° C. to 1000 ° C.
It is necessary to suppress heat energy consumption as small as possible. Therefore, the heat treatment apparatus is configured such that the heater is driven by large electric power, and the heater is covered with a heat insulating material to suppress the leakage of heat energy.

In such a heat treatment apparatus, the control temperature (control amount) depends on the set target temperature (target value).
However, the electric power (operating amount) when the temperature is set to the predetermined target temperature becomes smaller than the maximum output value. For example, if the allowable value range of the output limiting unit is set at 300 ° C. when the allowable value range is 0% to 100%, the final steady-state value of the control output signal is several%.
It will be about.

That is, as shown in FIG. 3 (b), although the integral operation value at the time of temperature rise rapidly increases, the control output signal is finally generated due to the integral suppressing section for reset windup countermeasures. Since it takes a long time to reach the steady value, the overshoot amount increases as shown in FIG.

The present invention has been made in view of such circumstances, and an object of the present invention is to quickly and accurately change a control amount output from a control target to a target value, and An object of the present invention is to provide a feedback control technique capable of suppressing overshoot and undershoot to a small extent, a semiconductor manufacturing technique using the same, and a temperature control technique therefor.

[0015]

According to a first aspect of the present invention, a control signal is generated by integrating at least a deviation between a control amount of a control target and a target value, and the control signal is set in advance. A feedback control device that outputs the control signal as a control output signal to the control target by limiting the control signal within the first limit range, and It is characterized by including an integration suppressing unit that suppresses the integration when exceeding a small second limit range.

A second means for solving the problems is an integral operation section for integrating the deviation between a target temperature value for the heat treatment furnace and a measured temperature value from the heat treatment furnace, and an operation including the integral operation section. An output limiting unit that limits the control signal from the unit by a first limit range and outputs the control signal as a control output signal to the heat treatment furnace, and the control signal exceeds a second limit range different from the first limit range. In the above case, the integration operation section is provided with an integration suppression section that outputs an integration suppression signal.

A third means for solving the problem is to generate at least a control signal by integrating at least a deviation between a target temperature value for the heat treatment furnace and a temperature measurement value from the heat treatment furnace. In a temperature control method for a semiconductor manufacturing apparatus, wherein the control signal is limited by one limited range and is output as a control signal to a heat treatment furnace, the integration is performed when the control signal exceeds a second limited range different from the first limited range. Is set to be suppressed.

According to the above-described first means, when the control signal exceeds the second limit range smaller than the first limit range, excessive integration is suppressed by the integration suppression unit. Overshoot and undershoot can be suppressed to a small value while quickly and accurately changing the control amount output from the controller to the target value.

According to the above-mentioned second means, when the control signal of the integral operation section exceeds the second limit range smaller than the first limit range, the integral suppression section causes excessive integration of the integral operation section. Is controlled, the temperature of the heat treatment furnace can be quickly and accurately changed to the target temperature, and the overshoot and undershoot at the temperature of the heat treatment furnace can be suppressed to a small value. Can be improved.

According to the third means, when the control signal exceeds the second limit range smaller than the first limit range, excessive integration of the integration calculation unit is suppressed. While quickly and accurately changing the temperature of the
Overshoot and undershoot at the temperature of the heat treatment furnace can be suppressed small, and the quality, reliability, and performance of the temperature control method of the semiconductor manufacturing apparatus can be improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

In the present embodiment, the feedback control apparatus according to the present invention is mounted on a heat treatment apparatus for performing heat treatment on a semiconductor wafer, which is one embodiment of the semiconductor manufacturing apparatus according to the present invention, and the semiconductor wafer is loaded. By performing feedback control of a heater for heating the heat treatment furnace, the temperature control method of the heat treatment apparatus according to one embodiment of the present invention is implemented.

That is, as shown in FIG. 4, a heat treatment furnace (hereinafter, referred to as a process tube) 20 of a heat treatment apparatus for performing heat treatment on a semiconductor wafer is heated by a heater 21 which is a control target of a feedback control device. A temperature sensor 22 composed of a thermocouple is installed in the processing chamber of the process tube 20 so that the temperature (control amount) in the process tube 20 can be measured. The temperature sensor 22 is connected to the control unit 2 via the subtraction unit 23.
4 and is configured to transmit the measured temperature (measured amount). A heater driving device (operation unit) 25 that applies electric power (operation amount) to the heater 21 is connected to the control unit 24, and a setting unit 26 that sets a target temperature (target value) is connected to the subtraction unit 23. I have.

The control section 24 includes a PD calculation section 31, an integration calculation section 32, an addition section 33, a first output restriction section 34, a second output restriction section 35, and an integration suppression section 36, and performs the operations described later. Configured to run.

The first output limiting unit 34 and the second output limiting unit 35 have an upper limit and a lower limit set in advance, and output the upper limit when the input value is larger than the upper limit. It is configured to output a lower limit value when the value is smaller than. Here, the first output limiting unit 34 sets the upper limit to 100% and the lower limit to 0% according to the output allowable range of the control output signal.

The upper limit value and the lower limit value of the second output limiting unit 35 are the output range of the first output limiting unit 34, and the steady-state value of the control output signal with respect to the current target temperature (target value) is It is set to be an intermediate value between the upper and lower limits. Here, assuming that the range between the lower limit and the upper limit of the first output limiter 34 is 0% to 100% and the steady value of the control output signal is 3%, the lower limit and the upper limit of the second output limiter 35 are set. Is set to 0% to 6%. That is, the second limit range defined by the second output limiting unit 35 is the heater (control target) 21 when the temperature of the heater 21 (control amount of the control target) is set at the target temperature (target value). The control output signal is set to be the same value on both the positive and negative sides from this reference value.

Next, the operation of the feedback control device mounted on the heat treatment apparatus according to the above configuration will be described to explain the temperature control method of the heat treatment apparatus according to one embodiment of the present invention, and FIGS. The effect of preventing excessive integration will be described.

When the target temperature is raised by the setting unit 26, the subtracting unit 23 outputs a deviation consisting of the difference between the target temperature from the setting unit 26 and the measured temperature from the temperature sensor 22.
This is transmitted to the D operation unit 31 and the integration operation unit 32, respectively. The PD operation unit 31 transmits the result of the PD operation regarding the deviation to the addition unit 33, and the integration operation unit 32 transmits the result of the integration operation regarding the deviation to the addition unit 33. The adder 33 outputs the control signal, which is the result of the addition, to the first output restrictor 3.
4. The signal is transmitted to the second output limiting unit 35 and the integration suppressing unit 36, respectively. When the control signal is within the allowable output range of the control output signal, the first output limiting unit 34 transmits the control output signal to the heater driving device 25 as a control output signal.

The heater driving device 25 supplies electric power to the heater 21 in proportion to the control output signal. Since the heater 21 heats the process tube 20 by this electric power,
The temperature of the processing chamber of the process tube 20 increases. The raised temperature is measured by the temperature sensor 22 and transmitted to the subtraction unit 23 as the measured temperature. Thereafter, by repeating the above-described closed loop, the temperature of the processing chamber of the process tube 20 is set to the target temperature.

In the above closed loop control, when the control output from the adder 33 is out of the range of 0% to 6% of the allowable output range, the second output limiter 35 sets the control signal to the upper limit or the lower limit. The value is limited and input to one terminal of the integration suppressing unit 36. The integration suppressing unit 36 compares the control output from the second output limiting unit 35 with the control signal from the adding unit 33, and when the difference value exceeds the allowable value range set in the integrating suppressing unit 36, The integration operation of No. 32 is stopped. Excessive integration is prevented by the integration calculation stopping process of the integration suppressing unit 36.

By the way, in the conventional example shown in FIG. 2 in which the second output limiting section is not provided, when the steady value of the control output signal is much smaller than the maximum value of the control output signal, for example, When the range of the control output is 0% to 100% and the steady value is 3%, the control output is 3% to 10%.
The integration is performed "positively" when it is in the large range of 0%, the integration is performed "negative" when the control output is in the small range of 0% to 3%, otherwise the integration suppression for reset windup is performed. Since the integration is not performed by the unit, an unbalanced integration in which the integration value increases quickly and decreases slowly is performed.

However, in the present embodiment, since the second output limiting section 35 is provided, "3% to 6%" and "0% to 3%" in which the integration of "positive and negative" is in the same range. "
And converge quickly to a steady-state value without excessively integrating positively. Next, the operation and effect of the second output control unit 35 will be described with reference to FIGS.

FIG. 5A is a diagram showing a comparison between the step response of the present embodiment and the conventional step response shown in FIG. 2, and FIG. 5B is a diagram showing the present embodiment at that time. FIG. 3 is a diagram showing an integrated value at. Here, the target value “10
The steady value of the control output signal of "0" is 3%.

As is clear from a comparison between FIG. 3B showing the integrated value of the conventional example and FIG. 5B showing the integrated value of the present embodiment, in the present embodiment, the temperature (control amount) The integration is suppressed at the time of ascending and quickly converges to a steady value. As a result, as shown in FIG. 6A, the settling time in the present embodiment is significantly reduced as compared with the setting time in the conventional example. That is, FIG. 6A shows that the control performance is improved according to the present embodiment.

FIG. 6 is a diagram for explaining the effect of preventing excessive integration, in which% is plotted on the vertical axis and time is plotted on the horizontal axis. Curve K ₃₁ in FIG. 6 (a) (hereinafter, K ₃₁
That. ) Is an output waveform of the PD operation unit 31 in the present embodiment, and a curve K ₁₁ (hereinafter, referred to as K ₁₁ ) is an output waveform of the PD operation unit 11 in the conventional example shown in FIG. A curve K ₃₂ (hereinafter, referred to as K ₃₂ ) in FIG. 6B is an output waveform of the integration calculator 32 in the present embodiment, and a curve K ₁₂ (hereinafter, referred to as K ₁₂ ) is shown in FIG. 6 is an output waveform of an integration operation unit 12 in a conventional example. FIG. 6 (c)
A curve K ₃₄ (hereinafter, referred to as K ₃₄ ) is an output waveform of the first output limiting section 34 in this embodiment, that is, a waveform of the control output signal, and a curve K ₁₄ (hereinafter, referred to as K ₁₄ ) is shown in FIG. 5 shows the output waveform of the first output limiting unit 14 in the conventional example shown in FIG.

In FIG. 6C, a range L indicates a range of the lower limit value and the upper limit value of the second output limiting unit 35 (hereinafter, referred to as a value range). In this case, the range is "0% to 6%". Has become. The output waveform of the second output limiting section 35 becomes what is limited in the range K ₃₄ is "0% to 6%." Incidentally, the value range of the first output limiting unit 34 in the present embodiment and the first output limiting unit 14 in the conventional example is “0% to
100% ".

[0037] First, an explanation for changes in the K ₁₂ and K _14. At the first time point (hereinafter referred to as t ₁ , the same applies to each time point), since K ₁₄ exceeds 100%,
₁₂ holds that value. In t _2, K ₁₂ resumes operation. In t _5, since K ₁₄ is less than 0%, K
₁₂ stops integration. t ₇ or later or K ₁₄ becomes 0%, to repeat or become number%, K ₁₂ is reduced gradually.

[0038] Next, a description will be given change in the K ₃₂ and K _34. In t _1, since K ₃₄ is greater than 6%, K
₃₂ stops integration. In t _3, K ₃₂ resumes integration. In t _4, since K ₃₄ is less than 0%, K ₃₂
Stops integration. In t _6, K ₃₂ resumes integration.

Immediately after the start of the step (approximately 0.5 to 2 on the horizontal axis)
The difference between K ₁₄ and K ₃₄ in is based on the difference between K ₁₂ and K _32. Therefore, integration stop of K ₁₂ is slower than the integral stop of K _32, it only overshoot of K ₁₄ is further increased. Why can not K ₁₂ is rapidly decreased after t _7, since K ₁₁ is a large negative value or overshoot, the K ₁₂ is reduced, anti-reset wine K ₁₄ is less than 0%, thus stopping integration This is because the function of the do-up is exhibited. That is, since overshoot occurs due to excessive integration immediately after the start of the step, the feedback control device according to the present embodiment devises to stop the integration at that time by providing the second output limiting unit 35. is there.

This will be described for easy understanding. Considering now that the control output signal at the time of stability immediately after the step is close to “0”, for example, 3%, the ability to increase the temperature (control amount) of the heater is 3 to 100%. "97"
Although there is a point, the ability to lower the temperature of the heater is 0 to
There is only 3% "3" points. That is, the ability to increase the temperature of the heater is large, but the ability to decrease the temperature is considerably small. For this reason, once overshoot of the control output signal occurs, it is difficult to settle. However, the conventional feedback control device 1
Since the PD calculation unit 11 and the integration calculation unit 12 executing the PID calculation at 0 do not recognize this situation, they treat the temperature rising ability and the temperature decreasing ability of the heater as the same, and thus cause overshoot. become.

Therefore, in the present embodiment, the integral operation section 3 which is particularly likely to cause an overshoot in the PID operation.
In the second aspect, a device for teaching the fact that "the ability to lower the temperature of the heater is small" by the second output limiting unit 35 has been devised.

Although the case of overshoot has been described, when the control output signal at the time of stability is, for example, 97%, it can be described as a method of solving undershoot.
When the control output signal at the time of stability is 50%, a normal closed loop is repeated.

As described above, according to the present embodiment, it is possible to quickly and accurately change the temperature of the heat treatment furnace of the heat treatment apparatus to the target temperature while suppressing the overshoot and the undershoot at the temperature of the heat treatment furnace. Therefore, the quality, reliability, and manufacturing yield of the heat treatment of the heat treatment apparatus can be improved, and thus, the quality, reliability, and performance of the semiconductor product can be improved.

FIG. 7 is a block diagram showing a heat treatment apparatus equipped with a feedback control device according to another embodiment of the present invention.

This embodiment is different from the above embodiment in that
The point is that the steady value table 37 is connected to the second output limiting unit 35. The steady-state value table 37 is configured to receive a target temperature (target value), output a steady-state value of a control output signal corresponding to the target temperature, and transmit the control output signal to the second output limiting unit 35. The steady-state value table 37 may be configured by previously obtaining and storing some steady-state values of the control output signal when the control temperature (control amount) is settled at the target value, or may be converted by an appropriate approximate expression. May be used.

According to the present embodiment, the stationary value table 37
Can change the steady-state value appropriately,
The function of preventing excessive integration according to each situation can be exhibited, and the performance of the above embodiment can be further enhanced.

The present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the scope of the present invention.

For example, the feedback control apparatus according to the present invention is not limited to being mounted on a heat treatment apparatus, but may be a semiconductor manufacturing apparatus having a gas processing furnace for forming a film on a semiconductor wafer, a semiconductor manufacturing apparatus having a vacuum exhaust furnace, or the like. Can be mounted on the entire semiconductor manufacturing apparatus of the present invention, and is not limited to the heater temperature control method of the heat treatment apparatus, but also the heater temperature control method of another semiconductor manufacturing apparatus, the gas flow rate control method and the pressure control method of the semiconductor manufacturing apparatus, etc. The present invention can be applied to a general control method of a semiconductor manufacturing apparatus.

[0049]

As described above, according to the present invention,
If the control signal exceeds a second limit range smaller than the first limit range, excessive integration is prevented by the integration suppression unit, so that the control amount output from the control target is quickly and accurately set to the target value. While overshoot and undershoot can be suppressed small.

For example, when a feedback control device is mounted on a semiconductor manufacturing apparatus having a heat treatment furnace, the temperature of the heat treatment furnace can be quickly and accurately changed to a target temperature while the temperature of the heat treatment furnace is changed to a target temperature.
Overshoot and undershoot at the temperature of the heat treatment furnace can be suppressed to a small extent, and the quality and reliability of the heat treatment of the semiconductor manufacturing equipment and the production yield can be improved. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional feedback control device.

FIG. 2 is a block diagram showing another conventional feedback control device.

FIG. 3 is a diagram for explaining the operation of FIG. 2;

FIG. 4 is a block diagram showing a heat treatment apparatus equipped with a feedback control device according to an embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation.

FIG. 6 is a diagram for explaining an action of preventing excessive integration.

FIG. 7 is a block diagram showing a heat treatment apparatus equipped with a feedback control device according to another embodiment of the present invention.

[Explanation of symbols]

Reference numeral 20: process tube (heat treatment furnace), 21: heater (control target), 22: temperature sensor (measurement unit), 23: subtraction unit, 24: control unit, 25: heater drive unit (operation unit,
26: setting unit, 31: PD operation unit, 32: integration operation unit,
33 ... Addition unit, 34 ... First output limitation unit, 35 ... Second output limitation unit, 36 ... Integration suppression unit, 37 ... Stable value table.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Minoru Nakano 3-14-20 Higashinakano, Nakano-ku, Tokyo Inside Kokusai Electric Co., Ltd. (72) Inventor Masaaki Ueno 3-14-20 Higashinakano, Nakano-ku, Tokyo Kokusai Electric F term (for reference) 5H004 GA03 GA11 GB15 HA01 HB01 KA54 KB02 KB04 KB06 KB13 KB32 KC39 KC53 LB10

Claims (5)

[Claims] 1. A control signal is generated by at least integrating a deviation between a control amount of a control target and a target value, and the control signal is limited by a first limit range set in advance to control output to the control target. In a feedback control device that outputs a signal, the integration is suppressed when the control signal is within the first limit range and exceeds a second limit range smaller than the first limit range. A feedback control device comprising an integration suppressing unit. 2. The control apparatus according to claim 1, wherein the second limit range includes a control output signal to the control target when the control amount from the control target is settled at a target value as a reference value. The feedback control device according to claim 1, wherein the feedback control device is set to have the same value. 3. An integral operation unit for integrating a deviation between a target temperature value for the heat treatment furnace and a measured temperature value from the heat treatment furnace, and a control signal from the operation unit including the integral operation unit as a first restriction. An output restricting unit that restricts by a range and outputs the control output signal as a control output signal to the heat treatment furnace; and, when the control signal exceeds a second restriction range different from the first restriction range, the integration calculation unit suppresses integration. A semiconductor manufacturing apparatus comprising: an integration suppressing unit that outputs a signal. 4. A control signal is generated by at least integrating a deviation between a target temperature value for the heat treatment furnace and a measured temperature value from the heat treatment furnace, and the control signal is limited by a first limit range. In the temperature control method of the semiconductor manufacturing apparatus which outputs as a control output signal to the semiconductor device, the integration is suppressed when the control signal exceeds a second limit range different from the first limit range. A temperature control method for a semiconductor manufacturing apparatus, comprising: 5. The apparatus according to claim 4, wherein the second limit range is set within the first limit range and smaller than the first limit range. A temperature control method for a semiconductor manufacturing apparatus.