JPH0769745B2 - Heater controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heater control device, and more particularly to a device for preventing overcurrent from flowing through the heater when controlling the heater used in a thin film forming apparatus or the like. Regarding

[Conventional technology]

A heater for heating a substrate is provided in a film forming chamber such as a thin film forming apparatus. This heater is provided, for example, on a substrate holder that holds the substrate, and is controlled so that the substrate held by the substrate holder maintains a constant temperature during film formation.

The temperature control of the heater is performed using a temperature controller and a power controller. That is, first, the worker sets the temperature gradient of the power controller to a predetermined characteristic and turns on the power controller. Then, the electric power is supplied to the heater from the electric power controller to heat the substrate holder containing the heater. The temperature near the heater is detected by a thermocouple,
The detection output of this thermocouple is input to a temperature controller provided outside the film forming chamber. The temperature controller performs PID control and outputs a control signal to the power controller. The power controller controls the output based on this control signal with a preset slope characteristic. At this time, the maximum output of the power controller is determined by the set slope characteristic.

[Problems to be Solved by the Invention]

When controlling the temperature of the heater using the temperature controller and power controller as described above, for example, if the target temperature is set to 200 ° C, the temperature controller detects the target temperature and the heater in the proportional band near 200 ° C. A deviation signal is generated from the temperature, and proportional control is performed based on this deviation signal.

However, if you change the target temperature to 300 ℃, for example, 200 ℃
Since the temperature maintained within the range of the proportional band in the vicinity is far from the proportional band for the changed target temperature (300 ° C), the deviation signal of the temperature controller is turned off and the maximum power is supplied to the heater. To the power controller. Then, the maximum voltage in the gradient characteristic set in the power controller is temporarily applied to the heater, and the overcurrent is supplied. As a result, overshoot occurs, it takes time to control to the target temperature, and the power controller is adversely affected.

An object of the present invention is to provide a heater control device capable of preventing an overshoot of a supply current and shortening a control time until reaching a target temperature when a set temperature of a heater is changed to a high temperature.

[Means for Solving the Problems]

A heater control device according to the present invention includes a temperature controller, an electric power controller, a proportional band outside detection means, and a control means.

The temperature controller generates a deviation signal according to the target temperature and the temperature detected by the heater, and outputs a control signal based on the deviation signal. The electric power controller controls electric power supplied to the heater according to a control signal from the temperature controller. The out-of-proportional band detecting means detects that the heater detection temperature is out of the proportional band for the target temperature by the deviation signal of the temperature controller. The control means is for making the maximum output of the power controller smaller than a preset output value for a predetermined period when it is detected that the heater detected temperature is out of the proportional band for the target temperature.

[Action]

In the present invention, when the target temperature of the temperature controller is changed to a high temperature, the deviation signal of the temperature controller is turned off, so this is detected by the overcurrent detecting means. When the overcurrent detecting means detects that an overcurrent flows through the heater, the maximum output of the power controller is set to be smaller than a preset output value for a certain period. Then, after the elapse of this fixed period, the maximum output of the power controller is returned to the original state, and the normal heater temperature control is performed.

As a result, even when the heater temperature is set high, an output smaller than the maximum output of the power controller is supplied to the heater for a certain period from that point. Therefore, it is possible to prevent an overshoot from occurring or an adverse effect of the overcurrent on the power controller.

Moreover, since the occurrence of overshoot can be prevented, the control time until the target temperature is reached can be shortened.

〔Example〕

FIG. 1 is a block circuit diagram of a heater controller according to an embodiment of the present invention.

For example, a heater 2 for heating a substrate is provided in the film forming chamber 1 of the film forming apparatus. A thermocouple 3 for indirectly detecting the substrate temperature is provided near the heater 2. The thermocouple 3 is connected to the temperature controller 4. The temperature controller 4 can set a target temperature from the outside, generates a deviation signal by comparing the detected temperature from the thermocouple 3 with the target temperature, and outputs the control signal b based on this deviation signal. It is what is output. The deviation signal of the temperature controller is generated when the internal relay contact 5 is turned on, and the on / off of the relay contact 5 is input to the sequencer 6 as a contact signal a. A relay coil 7 controlled by the state of the setting signal a is connected to the sequencer 6.

On the other hand, electric power is supplied from the electric power controller 8 to the heater 2. The control signal b from the temperature controller 4 is input to the electric power controller 8, and the electric power supplied to the heater 2 is controlled by phase control using a thyristor. Further, the voltage between the terminals T1 and T3 of the power controller 8 is always constant, and its maximum output is determined by the voltage between the terminals T1 and T2. The voltage between the terminals T1 and T2 can be externally set by an operator by the gradient setting device 9. Further, a parallel circuit of a resistor 10 and a relay contact 12 is inserted between the terminals T1 and T3 of the power controller 8. The relay contact 12 is controlled to be turned on and off by the relay coil 7. When the relay contact 12 is turned on, the maximum output of the electric power controller is V1 as shown in FIG. 2, and when the relay contact 12 is off, it is V2 lower than V1.

The excitation of the relay coil 7 is turned off only for a certain period (period t in FIG. 2) after the sequencer 6 receives the contact signal a.

Next, the operation will be described.

When controlling the heater temperature, first, the gradient characteristic is set by the gradient setter 9. Thereby, the maximum output and the temperature gradient of the power controller 8 are set. Further, the target temperature of the substrate is set by operating the temperature controller 4.

For example, if the target temperature is set to 200 ° C., the temperature controller 4 compares the target temperature of 200 ° C. with the temperature detected by the thermocouple 3, and based on the comparison result, sends the control signal b to the power controller 8. Output. When the detected temperature is sufficiently lower than the target temperature, the control signal b for supplying electric power to the heater 2 with the maximum output is output to the electric power controller 8. And the heater temperature is the target
When it enters into the proportional band around 200 ° C, the relay contact 5 inside the temperature controller 4 is turned on and a deviation signal is generated. Temperature controller 4
Performs proportional control based on this deviation signal, and the heater 2
Maintained at a temperature around 200 ° C. In this state, the relay coil 7 is excited and the relay contact 12 is on.

Next, from the above condition, set the target temperature of the heater to 300 ° C.
When the temperature is changed to, the detected temperature (about 200 ° C.) is out of the proportional range with respect to 300 ° C., so the relay contact 5 inside the temperature controller 4 is turned off and the deviation signal is turned off. At this time, the temperature controller 4 instructs the power controller 8 to supply power to the heater 2 with the maximum output.

At this time, it is detected by the contact signal a that the relay contact 5 inside the temperature controller 4 is turned off. Sequencer 6
With this contact signal a, the excitation of the relay coil 7 is turned off for the period t shown in FIG. This makes the relay contact 12
Turns off (open) as shown in FIG. Then the terminal
The voltage between T1 and the terminal T2 becomes smaller as compared with the case where the relay contact 12 is on (closed) by the amount of the resistor 10 inserted. Therefore, the heater voltage in this case is V2 as shown in Fig. 2.
And the heater 2 is heated by this voltage V2.

The sequencer 6 excites the relay coil 7 again after a period t has elapsed after receiving the contact signal a and turns on the relay contact 12. As a result, the voltage between the terminals T1 and T2 of the power controller 8 is first set by the slope setting device 9,
After that, the substrate temperature is maintained at 300 ° C. by normal heater control.

In this embodiment, even when the heater temperature is set high, as shown in FIG. 3, the current is supplied to the heater 2 with the characteristic of P2, which is compared with the case of the conventional characteristic P1. As can be seen, overcurrent can be prevented.

In addition, although the present invention is applied to the heater control of the film forming apparatus in the above-described embodiments, the present invention can be similarly applied to the heater temperature control of other apparatuses.

〔The invention's effect〕

As described above, in the present invention, when the set temperature is changed, it is detected by the deviation signal of the temperature controller that the heater detection temperature is out of the proportional band with respect to the target temperature, and from this detection result, the maximum output of the power controller is detected. Is reduced for a predetermined period, it is possible to prevent the overshoot of the current supplied to the heater when the set temperature is changed, and to shorten the control time until the target temperature is reached.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a heater control device according to an embodiment of the present invention, FIG. 2 is a diagram showing characteristics of a heater voltage when changing a set temperature in the device, and FIG. It is a figure which shows the current characteristic at the time of doing. 2 ... Heater, 3 ... Thermocouple, 4 ... Temperature controller, 5 ... Relay contact, 6 ... Sequencer, 7 ... Relay coil, 8
...... Power controller, 9 ... Slope setting device, 10 ... Resistance, 12 ... Relay contact.

Claims (1)

[Claims] 1. A heater controller for controlling a heater to a target temperature, the temperature controller generating a deviation signal according to the target temperature and the temperature detected by the heater, and outputting a control signal based on the deviation signal. And a power controller for controlling the electric power supplied to the heater by a control signal from the temperature controller, and a deviation signal of the temperature controller for detecting that the heater detected temperature is out of a proportional band with respect to a target temperature. A proportional band outside detection means, and a control means for making the maximum output of the power controller smaller than a preset output value for a predetermined period when it is detected that the heater detected temperature is out of the proportional band for the target temperature. , A heater control device.