JP2691228B2 - Heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a heating device.

(Prior Art) Generally, in a step of applying a resist to a surface of an object to be processed such as a semiconductor wafer, the object to be processed is heated for the purpose of stabilizing the resist.

In other words, in order to obtain a uniform resist thin film, it is important to suppress the fluctuation of resist viscosity as much as possible, and as part of the conditions, the air flow around the object to be processed during film formation and the uniform stabilization of the ambient temperature are stabilized. The temperature of the object to be processed can be made uniform, and the resist temperature can be made uniform.

FIG. 9 shows an example of a heating device for heating such an object to be processed. For example, in the inside of the plate body 1 for heating the semiconductor wafer W, a heating element 2 such as nichrome is provided parallel to the surface thereof. 3 and 4 are buried. Each heating element 2,
For example, from 200 V AC power source 5 to 3 phases (3 to 4) (φ1 to φ)
The power for one phase of 3) is supplied respectively.

The AC power supply 5 is connected to a temperature controller 7 that controls the supply operation based on the temperature measurement signal y from the temperature measurement sensor 6 arranged in the plate body 1 and the set temperature R of the plate body 1. .

Then, in the control at the time of supplying the electric power to each heating element 2, 3, 4, when the control interval Tc at 50 Hz is set to 0.05 seconds, for example, as shown in FIG. When the control amount u = 50% is given from, the power supply is cut off at the dotted line portion in the figure.

 Here, the controlled variable u is expressed by u = Kpe + (1 / Ti) ∫edt + Td · (de / dt) in the continuous time system.

However, Kp is proportional gain, e is error, Ti is integration time,
Td is the differential time, and ∫ is the integration, respectively. In the digital control system, digital control is performed at the control interval Tc.

As a result, the heat generated from each of the heating elements 2, 3 and 4 is diffused inside the plate body 1, and then the heat is radiated from the surface thereof.

(Problems to be Solved by the Invention) However, in the above-described conventional heating device, when the control amount u = 50% is given as shown in FIG. Since the power supply is cut off,
Within the control interval Tc, the ON state of the power supply is biased to the left side (total power is ON until Tc × 0.5, then all power is OFF), and power is supplied to each heating element 2, 3, 4 in such a state. Is supplied, the temperature fluctuation of the plate body 1 becomes large, so that the semiconductor wafer W cannot be heated uniformly.

Furthermore, since there are at least two phases that cut off the power supply at a position outside the zero cross point of the power waveform, noise is generated, which causes adverse effects such as causing malfunction of electronic devices such as other computers. Will be lost.

Therefore, as shown in FIG. 10- (b), the AC power supply 5
It is conceivable to turn on / off using a zero-kiss SSR. However, for example, even if the control amount u = 50% is given, 50% or more of the electric power will be supplied,
There is a limit in the temperature control accuracy that accompanies the power control accuracy.

The present invention has been made in response to such a situation, and improves the temperature control accuracy and turns on / off the power supply.
It is an object of the present invention to provide a heating device capable of preventing the generation of noise accompanying turning off.

[Structure of the Invention] (Means for Solving the Problems) A heating device of the present invention is a heating device having a heating body for equalizing the temperature of an object to be processed at a predetermined value. Based on the provided heating element, an AC power source for supplying electric power of a plurality of phases to the heating element, temperature detecting means for detecting the temperature of the heating element, and a detection result and a set value of the temperature detecting means,
And a control means for randomly performing on / off control of at least one phase of the power supply operation of the plurality of phases.

(Operation) In the heating apparatus of the present invention, the control means randomly controls the power supply operation from the AC power supply to be supplied to the heating element within the control interval to turn on / off the power supply. It is possible to reduce the deviation of the supply on-state.

(Example) Hereinafter, details of an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a heating device for heating an object to be processed in a step of applying a resist in semiconductor manufacturing. It should be noted that the same parts as those in FIG. 9 are designated by the same reference numerals, and overlapping description will be omitted.

As shown in the figure, the temperature controller of the heating device is provided with a PID control unit 8 that outputs a controlled variable u based on the temperature measurement signal of the temperature sensor. Further, in the temperature controller, an AC power waveform of each of a plurality of phases, for example, three phases (φ1 to φ3) supplied from the AC power source based on the control amount u from the PID control unit 8 within the control interval Tc. A decoder 9 for outputting ON / OFF signals U, V, W for randomly controlling and turning on / off each is provided. The output of the decoder 9 is connected to the zero cross SSR17 that connects and disconnects the power supplied to the load of each phase.

FIG. 2 shows an example of the configuration of the control circuit provided in the decoder 9 described above. This control circuit has three phases (φ1 to φ3).
Corresponding to the respective phases, the three-system circuit is provided, and each has the same configuration.

Therefore, only the control circuit corresponding to φ1 will be described here, and description of the other control circuits corresponding to φ2 and φ3 will be omitted.

First, immediately before the zero cross point, the output level is "0" →
The timing pulse generator having a change of "1" will be described.

As shown in FIG. 2, the control circuit corresponding to φ1 has
A photocoupler 11 for transmitting a signal corresponding to a positive input waveform in an electrically insulated state and a photocoupler 12 for transmitting a signal corresponding to a negative input waveform are connected to an AC power supply 10 that supplies an alternating current of φ1. It is equipped.

Each photocoupler 11, 12 has a threshold value and a Schmitt trigger type inverter 1 that generates a rectangular wave within a half cycle of each waveform transmitted from each photocoupler 11, 12.
3,14 are connected.

An OR circuit 15 that outputs a "1" level signal when an output from either one of these inverters 13 and 14 is connected to each inverter 13 and 14.

As a result, "0" is displayed immediately before the zero cross point of each phase.
→ A timing pulse that rises to "1" can be obtained.

The OR circuit 15 has a clock (CL
K) The gate is connected.

To the Q gate of the flip-flop 16, a zero cross type solid stay relay (SSR) 17 which is turned on at the next zero cross point when a "1" level signal is output from the Q gate is connected.

A load 18, which is a heating element of a hot plate, to which electric power of φ1 is supplied from the AC power supply 10 by the ON / OFF operation of the SSR 17 is connected to the SSR 17.

On the other hand, for example, a random number generation circuit 19 is connected to the J gate of the flip-flop circuit 16 as random control means.

The random number generation circuit 19 generates a random number of the required number by, for example, the mixed congruential method based on the timing from the timing controller 20 that sets the control amount u and the control interval Tc from the PID control unit 8 described above. The generator 21 is provided.

For example, when the random number generator 21 responds to the random numbers as shown in FIG. 3, the black portion is supplied with electric power as shown in FIG.

A memory 22 for storing the random numbers generated by the random number generator 21 is connected to the random number generator 21.

A latch circuit 23 is connected to the memory 22, and the latch circuit 23 fetches the random number output from the memory 22 in synchronization with the timing from the timing controller 20 based on the address designation from the address counter 24.

Next, the operation of the heating device having such a configuration will be described with reference to FIGS.

First, when the control amount u is output from the PID control unit 8, the timing controller 20 of the decoder 9 controls the control amount u.
Based on the above, for example, as shown in FIG.
Set 0.1 seconds.

Next, the random number from the random number table 21a of the random number generator 21 is stored in the memory 22.

At this time, the generated random number corresponds to the black-painted portion in the waveform of each φ1 to φ3 of the applied voltage in FIG. 5 when the control amount u = 50%, for example.

Then, the latch circuit 23 is connected to the timing controller 20.
After taking in the random numbers stored in the memory 22 in correspondence with φ1 to φ3 respectively, based on the timing from, the flip-flop 16 of the flip-flop 16 of the control circuit corresponding to φ1.
Output to the gate.

When the "1" level is output from the OR circuit 15,
An ON / OFF signal u is output from the Q gate of the flip-flop 16, and when this signal is at the "1" level, the SSR 17 is turned on and the output of φ1 is supplied from the AC power supply 10.

50 at the first control interval Tc = 0.1 second
% When the power supply at the time of ON is finished, the random number from the random number table 21a of the random number generator 21 in the second control interval Tc = 0.1 second and the second control amount u = 50% is stored in the memory 22. Remembered.

At this time, the generated random numbers correspond to black-painted portions in the waveforms of φ1 to φ3 of the applied voltage shown in FIG. 6, for example.

And 50% at the first control interval Tc = 0.1 seconds
The second control interval Tc as in the power supply operation at the time of ON
= 0.1 second, the power supply operation at 50% ON is performed, that is, the AC power supply 10 supplies the power of φ1. The fifth
As can be seen by comparing Fig. 6 and Fig. 6, the characteristic that the distribution of the waveforms to which power is applied is different stochastically even at the same Tc and u, avoiding periodic power supply. You can

7 and 8, the control interval Tc = 0.
The figure shows 40% ON time at 04 seconds and 70% ON time at control interval Tc = 0.5 seconds, and the total number of power waveforms supplied to each load within the control interval Tc and the control interval Tc are shown above. The ratio of the total number of power waveforms that can be supplied to each load is set so as to substantially correspond to the controlled variable u.

As described above, in this embodiment, the control interval is based on the random number.
Since the ON waveform part in Tc is made to vary sequentially,
It is possible to prevent the bias of the ON state of the power supply. As a result, temperature fluctuations of the hot plate can be suppressed, so that the object to be processed can be heated uniformly.

Further, in this embodiment, since the phases of φ1 to φ3 are individually turned on / off, it is possible to improve the temperature control accuracy associated with the power control accuracy.

Further, in the present embodiment, since the power supply is turned on / off at the zero cross points of the respective power waveforms of φ1 to φ3, it is possible to prevent the generation of noise during the on / off. .

Furthermore, in the above embodiment, the case where random control is performed on each of φ1, φ2, and φ3 has been described, but the random control may be at least one phase random control such as only φ1, only φ2, only φ3, and only φ1 and φ2 two phases.

[Effects of the Invention] As described above, according to the heating device of the present invention, it is possible to prevent the generation of noise accompanying the on / off of power supply and improve the adjustment accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment in the case of being applied to a heating device for heating an object to be processed in a step of applying a resist in semiconductor manufacturing, and FIG. 2 is provided for decoding the heating device of FIG. FIG. 3 is a diagram showing a control circuit, FIG. 3 is a diagram showing an example of random number correspondence to the memory of FIG. 2, and FIG. 4 is on / off of power supply based on the random number in the random number table of FIG. FIG. 5, FIG. 6 and FIG. 6 show the state in which the power supply is turned on / off based on the random numbers in the random number table in FIG. 3 at the control interval Tc = 0.1 seconds of 50%.
FIG. 7 shows an example of turning on, and FIG. 7 shows an example of turning on / off the power supply based on the random number in the random number table of FIG. 3 at 40% on at the control interval Tc = 0.04 seconds. 8 and 9 show the control interval Tc = 0.5 when the power supply is turned on / off based on the random number in the random number table of FIG.
FIG. 9 is a diagram showing an example in which 70% is turned on in seconds, FIG. 9 is a diagram showing an example of a conventional heating device, and FIG. 10 is a diagram showing an example of control by the temperature controller of FIG. 8 ... PID control unit, 9 ... Decoder, 10 ... AC power supply, 1
1,12 …… Photo coupler, 13,14 …… Inverter, 15 ……
OR circuit, 16 ... Flip-flop, 17 ... SSR, 19 ...
… Random number generator, 20 …… Timing controller, 21a
…… Random number table, 21 …… Random number generator, 22 …… Memory,
23 …… Latch circuit, 24 …… Address counter.

Claims (1)

(57) [Claims] 1. A heating device having a heating element for equalizing the temperature of an object to be processed to a predetermined value, wherein a heating element provided to heat the heating element and a plurality of phases of electric power are supplied to the heating element. An alternating current power source to be supplied, temperature detecting means for detecting the temperature of the heating body, and based on a detection result and a set value of the temperature detecting means,
And a control means for performing on / off control of at least one phase of the power supply operation of the plurality of phases at random.