JPH03169367A - Heating apparatus - Google Patents

Abstract

PURPOSE:To suppress the temp. change of an object to be treated by a method wherein the AC power supplied to the heater of a hot plate is controlled on the basis of the detection result of the temp. detection means of the hot plate and the object to be treated and a temp. set value by the operation of operation quantity and the alteration of a control interval. CONSTITUTION:The temp. of a hot plate 10 uniformizing the temp. of an object to be treated in a predetermined value is detected by the first temp. detection means 20 and the temp. of the object to be treated is detected by the second temp. detection means 18. Further, in a control means 16, the AC power supplied to the heater 11 of the hot plate 10 is controlled on the basis of the detection results of the temp. detection means 20, 18 and a temp. set value by the operation of operation quantity and the alteration of a control interval. As a result, the noise generated by the control of power can be prevented and the temp. change of the object to be treated can be suppressed with high accuracy.

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a heating device that uniformizes the temperature of a processed object at a predetermined value. (Prior art) After the process of applying resist to the surface of an object to be processed, such as a semiconductor wafer, by heating with a hot plate, the object to be processed is heated for the purpose of stabilizing the resist, removing the resist solution, etc. There is. In other words, in order to obtain a uniform thin film of resist, it is important to suppress fluctuations in the viscosity of the resist as much as possible, and as part of the conditions, uniformity and stability of the air flow and ambient temperature around the object to be processed in the film shape is required. , uniformity of the temperature of the processing body itself, uniformity of resist temperature, etc. FIG. 4 shows an example of a heating device for heating a semiconductor wafer after applying resist. Inside the heat diffusion plate 1, which radiates heat evenly from the surface, there is a heating device parallel to the surface. A heating element 2 made of nichrome or the like is buried. Further, a proximity pin 4 is provided on the surface of the heat diffusion plate 1 in order to place the object 3 to be processed, such as a semiconductor wafer, slightly floating.
, 4 are provided. The heating element 2 is supplied with an alternating current of, for example, 200v.
iriFi. 5 is connected. A temperature controller 6 is connected to the AC power source 5, and the temperature controller 6 adjusts the temperature based on the temperature measurement signal from the temperature sensor 7 arranged inside the heat diffusion plate 1 and the target temperature R of the heat diffusion plate 1. to control the power supplied to the heating element 2. As shown in FIGS. 5 and 6, the temperature controller 6 controls the supply operation of the AC power source 5 in pulses within the control interval Tc based on the target temperature R and the temperature measurement signal from the temperature sensor 7. It is controlled by turning it on and off automatically. The control interval Tc at this time is the proximity gap Pg and the temperature fluctuation width ΔTl of the heat diffusion plate 1 and the object to be processed 3.
+ and ΔTv, etc., at a fixed interval based on a prior evaluation. However, the control interval Tc is the temperature fluctuation range Δ of the object 3 to be processed.
Even in the worst case case, Tv is an interval that is below the specification. (Problems to be Solved by the Invention) However, the conventional heating device described above has a limit in suppressing fluctuations in the temperature of the object to be processed due to power control accuracy. In other words, for example, when the control interval Te is 1 second at 50 Hz, the zero cross points p are 100, and when the control power is 1 degree, the maximum power/10
It becomes 0. Therefore, even if an attempt is made to suppress the temperature fluctuation of the object to be processed as much as possible by making the control interval extremely small, the accuracy when the control interval Tc is set to 0.1 seconds as shown in FIG. The power becomes 1/10 2 , the control accuracy decreases, and temperature fluctuations cannot be suppressed. However, when performing this control every 0.1 seconds, it is possible to perform fine-grained power control by, for example, connecting or disconnecting the power at a location other than the zero cross point. However, if the power is turned on or off at a position away from the zero-crossing point of the power waveform, noise may be generated, causing malfunctions in other electronic devices such as computers. Become. The present invention provides such η! I was intimidated by dealing with feelings,
It is an object of the present invention to provide a heating device that can prevent noise caused by power control and suppress fluctuations in the temperature of an object to be processed with high precision. [Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the heating device of the present invention includes a heating device having a hot plate that uniformizes the temperature of the object to be processed at a predetermined value. , a first temperature detection means for detecting the temperature of the hot plate, a second temperature detection means for detecting the temperature of the object to be processed, and detection results and set values of the first and second temperature detection means. and control means for controlling the electric power supplied to the heating element of the hot plate by manipulating the manipulated variable and changing the control interval. (Function) In the heating device of the present invention, the control means operates the input time and control interval of the electric power supplied to the hot plate heating element based on the detection results and set values of the first and second temperature detection means. Since power is turned on and off at the cello cross point, noise caused by power control can be prevented and fluctuations in the temperature of the object to be processed can be suppressed. (Embodiments) Hereinafter, details of embodiments 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 that heats an object to be processed in a baking step after applying a resist solution in a semiconductor manufacturing process. Inside the heat diffusion plate 10 of the hot plate of the heating device described above, a heating element 11 made of, for example, nichrome, is installed parallel to the surface of the hot plate. On the surface of the thermal diffusion plate 10, there are at least three proximity pins 13a, 13b for placing an object to be processed, for example, a semiconductor wafer (hereinafter referred to as wafer) 12 slightly floating from inside the thermal diffusion plate. ．． 14 are provided. The proximity bins 13a, 13b, and 14 form a proximity gap Pg between the thermal diffusion plate 10 and the semiconductor wafer. At least one proximity bin 14 is formed with a communication hole 14a for temperature measurement. The heating element 11 is connected to an AC power source 15 that supplies an AC of, for example, 200V. A Tc variable controller 16 is connected to the AC power source 15. This Te variable type controller 16 calculates, for example, the average power per unit time by the operation of the input time and the control interval T. This is controlled by changing c. The Tc variable controller 16 includes a temperature sensor 1 that measures the temperature Tv of the wafer 12 via a lead wire 17 inserted into the communication hole 14a of the proximity bin 14.
8 is connected to the heat diffusion plate 1 via a lead wire 19.
An IP1 temperature sensor 20 is connected to measure the temperature T I of 0. Next, the operation of the heating device having such a configuration will be explained using FIGS. 2 and 3. First, when the wafer 12 is placed on the heat diffusion plate 10, the Tc variable controller 16 controls the supply operation of the AC power source 15 by turning it on and off within the control interval Tc.
11 The temperature Tv of the wafer 12 from process A measured by the $1 temperature sensor 20 wafer is taken into the Tc variable controller 16. At this time, the temperature Tv from the wafer 12 is compared with the target temperature R of the hot plate, and the Tc variable controller 1
6 outputs an on/off signal over the difference E and temperature Tw. In other words, as shown in FIG. 3(a), for example, the control interval Tc at 50 touches! The zero-crossing point p is 100 in seconds. Here, the power when turned on for that 1 second is 100
%. Here, the control interval Tc refers to one on/off period. For example, when the operation amount is 25%, the control interval Te is set to 0. For example, when commanding the time to be less than 1 second, the number of Xerox points is only 10 at 0.05 seconds, so 20%
(Figure 3 (
a)). In this case, the Tc variable controller 16 performs the following operations. That is, as shown in FIG. 3(b), the control interval Tc is set to 0.
For example, it is turned on at the zero cross point pO and turned off at the zero cross point p5 (the third
Figure (b)). As a result, the supplied power becomes 25%. The control by the variable Tc controller 16 can be expressed as follows. U(z) / E(z) −Kp 10(TI /Tc
) /(1-Z-') + Td. (1-z
-') Here, U is the manipulated variable, E is the error, Kp is the proportional gain, T1 is the integral special period, Tc is the control interval (sampling patent application), Td is the differential time, and 2 is the 2-conversion operator. ing. The Tc variable controller 16 changes the shift interval of z-1 and various parameters accompanying changes in the shift interval. Note that in a situation where the wafer 12 is placed on the heat diffusion plate 10, the above control is performed using the heat diffusion plate temperature Tl1 measured by the δl1 temperature sensor 18. As described above, in this embodiment, the Tc variable type controller controls the average power per time about tlt by controlling the control interval Tc.
Since the control is performed by changing the temperature, temperature fluctuations of the object to be processed can be suppressed without reducing the accuracy of the control power. Furthermore, in this embodiment, since the temperatures of the object to be processed and the heat diffusion plate are taken in separately, the Tc variable controller automatically sets the control interval Tc even if the proximity gap Pg changes. , there is no need to reset the control interval Te. Furthermore, the Tc variable controller controls the power (j
Since the percentage pay is turned on and off, it is also possible to prevent noise from being printed on and off. In this example, the present invention was explained using a hot plate 1 in which a heating element such as nichrome was embedded in a heat diffusion plate, but the heating element is not limited to this example. A heated hot plate or a heat treatment device that performs lamp heating using infrared rays, ultraviolet rays, etc. may be used. In addition, in this embodiment, the case where the present invention is applied to a heating device that heats a wafer in the process of coating a resist is explained, but the present invention is not limited to this example. Even Bulova
It goes without saying that the present invention can be applied to both CvD wafer heating and other methods.

【Effect of the invention】

As explained above, according to the heating device of the present invention, since the control means controls the average power supplied per unit of patent application by appropriately changing the control interval, fluctuations in the temperature of the object to be processed can be controlled. can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention applied to a heating device for heating a body in the process of coating a resist, and FIG. 2 is a block diagram showing the main parts of the heating device shown in FIG. 1. , FIG. 3 is a waveform diagram for explaining the operation of the heating device shown in FIG. 1, FIG. 4 is a diagram showing a conventional heating device, and FIGS. 5 and 6 are diagrams showing the operation of the heating device shown in FIG. It is a figure for explaining. DESCRIPTION OF SYMBOLS 10... Thermal diffusion plate, 11... Heating element, 12... Semiconductor wafer (wafer), 13a, 13b, 14... Proximity bin, 15... AC power supply, 16... T
c variable type controller, 18.20...temperature sensor.

Claims (1)

[Claims] (1) A heating device having a hot plate that uniformizes the temperature of the object to be processed at a predetermined value, comprising: a first temperature detection means for detecting the temperature of the hot plate; and a first temperature detection means for detecting the temperature of the object to be processed. a second temperature detection means; and based on the detection results and temperature setting values of the first and second temperature detection means, the AC power supplied to the hot plate heating element is controlled by manipulating the manipulated variable and changing the control interval. A heating device comprising: a control means for controlling the heating device;