JPH11354399A - Substrate heating device - Google Patents

Abstract

(57) Abstract: Provided is a substrate heating apparatus that performs uniform substrate heating even at a wide range of heat treatment temperatures. An inner peripheral side heat insulator and an outer peripheral side heat insulator are provided on an outer peripheral portion of a main substrate heating structure including a first heating element, a thermal diffusion body, a planar heat insulator, and a first temperature sensor. The second heating element 6 and the second temperature sensor 12 sandwiched by the body 7 are buried, and the first heating plate is of a type controlled by independent temperature control circuits, and the same as the first heating plate. The substrate 1 is heated by placing a second heating plate of the system at a position facing the first heating plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for manufacturing a semiconductor substrate, a substrate for a liquid crystal display (LCD), or a photomask used in these exposure processes in the air.
The present invention mainly relates to a substrate heating apparatus and a heating method for performing resist baking after exposure of a wiring pattern or the like.

[0002]

2. Description of the Related Art A high-definition electron beam drawing apparatus or KrF
As a resist material used in the exposing step using an excimer laser, a chemically amplified resist mainly having excellent characteristics in sensitivity to irradiation energy and resolution is used. A chemically amplified resist needs to undergo cross-linking or decomposition reaction of the resin by post-exposure bake (Post Exposure Bake: PEB), for example, to reduce the variation of the wiring width in the substrate plane to 0.01 μm or less. In order to suppress this, it is necessary to suppress the in-plane distribution of the substrate temperature during the heat treatment at about 100 ± 20 ° C. to ± 0.1 ° C. or less.

[0003] For this purpose, how to reduce the heat loss due to natural convection or forced convection from around the heating plate, which is the main factor that causes the substrate temperature to be non-uniform, or to reduce the amount of heat equivalent to the amount of heat lost It is necessary to take effective and simple measures against the issue of how to replenish water.

Conventionally, there is a means disclosed in Japanese Patent Application Laid-Open No. 9-50957 for the purpose of performing such high-precision heat treatment. Hereinafter, this conventional technique will be described with reference to FIG. The substrate 101 includes a first heating plate 102 directly or with a small gap, and a substrate 101.
Is heated by heat transfer from a second heating plate 103 installed at a fixed interval above the plate. here,
First heating plate 102 and second heating plate 103
If the in-plane heat generation density is uniform, heat is removed from the periphery of the first heating plate 102 by convection of air, so that the temperature of the peripheral portion of the substrate 101 is lower than that of the center.

[0005] In the above-mentioned prior art, in order to correct this, a measure is taken so that the amount of heat transfer from the second heating plate 103 to the substrate 101 increases gradually from the center to the periphery. The first of these means is to make the heat value of the second heating plate 103 increase gradually from the center toward the periphery. A second feature of this means is that the thickness of the space where the second heating plate 103 and the substrate 101 face each other is gradually reduced from the center toward the periphery.

[0006]

However, the heat treatment temperature of the resist is not performed at a specific temperature, but is set at successive processing temperatures in order to cope with optimization of the type of the resist to be used and between other processes. Changes are made. In this regard,
In any of the above-described conventional techniques, the heat transfer amount at the outer peripheral portion of the substrate 101 can be larger than that at the central portion, but the heat generation amount or the thickness of the space at the outer peripheral portion depends on the processing temperature of the substrate 101. Since the amount of heat loss due to the convection of the air in the peripheral portion differs when the change is made, it is necessary to optimally adjust the state of the heat generation distribution or the thickness of the opposed space each time.

The present invention solves such a problem,
It is an object of the present invention to provide a means capable of performing uniform heating even in a wide range of heat treatment temperatures only by adjusting the temperature setting of the temperature control circuit, not by changing the structure of the apparatus.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for accurately replenishing heat loss due to convection of air in a peripheral portion and eliminating a temperature difference between a central portion and an outer peripheral portion. Basically, take the following measures. A first heat generating element, a heat diffuser for diffusing heat of the first heat generating element are provided on an upper surface of the first heat generating element, and a heat insulator for suppressing heat release is provided on a lower surface of the first heat generating element. And, in the first heating plate configured by burying a first temperature sensor for controlling the temperature of the first heating element at the center of the heat spreader, at the outer peripheral portion of the heating plate, A second heating element sandwiched between heat insulators is provided, and a second temperature sensor for controlling the temperature of the second heating element is embedded in an outer peripheral portion of the heat diffusion body.

Here, a substrate is placed on the upper surface of the heat spreader,
Stable and uniform heating is performed by controlling the temperatures of the first heating element and the second heating element by independent temperature control circuits each having a PID control function and the like. In addition, the whole of these structures is isolated from the outside air by a heat insulation case. In addition to simply placing the substrate on the heat diffuser, the substrate may be placed on the surface of the heat diffuser and heated while maintaining a small gap by providing protrusions, or by electrostatic suction or vacuum suction. For example, the heating may be performed while the substrate is being sucked.

Although the above is the basic means of the present invention, in the present invention, in order to simplify the temperature control of the second heating element,
An element R having a characteristic whose resistance value greatly changes with temperature, such as a resistance temperature detector or a thermistor, is provided in the second temperature sensor.
Using c, ON-OFF control of the heating element is performed using a potential difference caused by a difference in resistance value from the reference resistor Rb.

In the above-described basic means, the heat retaining case usually requires an opening for taking the substrate in and out, and a shutter for sealing the opening. When the shutter is opened, the outside air and the inside air are exchanged to some extent.
The temperature near the opening of the heating plate decreases. In order to correct the temperature unevenness, the second heating element is divided into a plurality of parts, and the temperature is controlled independently of each other, so that when the heat loss is different at each position of the outer peripheral portion, the heat supply corresponding thereto is performed. .

Next, for the purpose of suppressing the release of heat from the surface of the substrate, a second heating plate is provided at a position facing the first heating plate, and the second heating plate is connected to the first heating plate. The substrate is heated at the same set temperature as the heating plate. In this case, the distance between the first heating plate and the second heating plate is desirably as small as possible so as not to affect the inside due to convection from the surroundings. Need to be smaller.

Further, the method of controlling the temperature of the second heating plate must be optimized in accordance with the distance between the first heating plate and the second heating plate. That is, the distance between the first heating plate and the second heating plate when the substrate is heated is 1
When the thickness is as large as 0 mm or more, the temperature unevenness in the second heating plate does not significantly affect the substrate. However, in order to reduce the interval and to make the accuracy of the temperature uniformity of the substrate ± 0.1 ° C or less, The second heating plate needs to have the same configuration as the first heating plate.

Alternatively, the first heating plate or the second heating plate
The heating plate is provided with an up-and-down mechanism to increase the space between the plates when transferring the substrate, and to reduce the space between the plates when heating the substrate, thereby improving the heating efficiency. here,
In order to alleviate the turbulence of the air flow generated when the first heating plate or the second heating plate moves, a heat retaining ring is provided on the outer periphery of the second heating plate, and the first heating plate and the second heating plate are arranged. Apparently seal the gap between the heating plates.

[0015]

FIG. 1 is a sectional view showing a basic structure of a first heating plate according to the present invention. On the first heating element 3, a heat diffusion body 2 for diffusing the heat of the first heating element 3 is provided on an upper surface, and a flat heat insulator 4 for suppressing heat release is provided on a lower surface, In addition, the first portion
A first temperature sensor 9 for controlling the temperature of the heating element 3 is embedded. Further, in order to accurately supply the heat loss due to the convection of the air in the peripheral portion and to eliminate the temperature difference between the central portion and the peripheral portion, the inner peripheral side heat insulator 5 and the outer peripheral side heat insulator 7 are provided in the outer peripheral portion.
A second heat sensor 6 for controlling the temperature of the second heat generator 6 is buried in the outer peripheral portion of the heat spreader 2 and near the surface or below the surface. The substrate 1 is placed on the upper surface of the heat spreader 2. The first heating plate having such a basic configuration is isolated from the outside air by the heat retaining case 8.

The first heating element 3 and the second heating element 6 are connected to PI
Independent temperature control circuit 1 having D control function etc.
Stable and uniform heating is performed by controlling the temperature with 0 and 13. The installation form of the substrate 1 on the upper surface of the heat spreader 2 is as follows.
In addition to simply placing the substrate, a form in which a protrusion is provided on the surface of the thermal diffusion body 2 to perform heating while maintaining a small gap, or heating while adsorbing a substrate by electrostatic suction, vacuum suction, or the like is performed. Any of the forms may be used.

In this basic configuration, the first heating element 2 and the second heating element 6 are insulated by a sheath heater insulated internally or a Si-based rubber or the like, and are formed into a planar pattern that has been subjected to a predetermined patterning. Any of heaters may be used. The plane heat insulator 4, the inner peripheral side heat insulator 5 and the outer peripheral side heat insulator 7 are made of polyimide resin, polyamide resin, fluorine resin, or the like.
It is desirable to use a material which has a small thermal diffusivity as compared with metal and is easy to process. Further, as the thermal diffuser 2, a metal having a large thermal diffusivity such as Al or Cu is desirable.

The above is the basic embodiment of the present invention. As shown in the circuit diagram of FIG.
In order to simplify the temperature control circuit of the heating element 6, the second temperature sensor 12 has a characteristic such that a resistance value greatly changes depending on the temperature, such as a resistance temperature detector or a thermistor (FIG. 2).
Using the element Rc of (b), a potential difference caused by a difference between the resistance value and the reference resistance Rb is preliminarily amplified by an operational amplifier and input to a relay or an SSR.
N-OFF control is performed.

In order to perform this control method accurately, calibration data of the temperature T and the resistance value Rc (T) of the second temperature sensor 12 is measured in advance, and the resistance value Rc1 corresponding to the set temperature T1 is added to the reference resistance Rb. To adjust. This is an effective means in terms of apparatus cost when a plurality of second heating elements as shown in FIG. 3 are required.

In FIG. 3, the heat retaining case 8 usually requires an opening 15 for taking the substrate 1 in and out, and a shutter 16 for sealing the opening 15. When the shutter 16 is opened, the outside air and the inside air are exchanged to some extent,
The temperature near the opening 15 of the first heating plate decreases. In order to correct the temperature unevenness, the second heating element 6 is divided into a plurality of parts, and the temperature is controlled independently of each other, so that when the heat loss is different at each position of the outer peripheral portion, the heat supply corresponding thereto is replenished. Do. In this case, it is more cost-effective to use the simplified circuit shown in FIG. 2 than to use a high-performance circuit having a PID control function or the like for the temperature control circuit of the second heating element 6.

Next, for the purpose of suppressing the release of heat from the surface direction of the substrate 1, a second heating plate is installed at a position facing the first heating plate, and the second heating plate is connected to the first heating plate. The substrate 1 is heated at the same set temperature as that of the heating plate.

FIG. 4A shows this configuration. The basic configuration of the second heating plate is as follows. First heating element 1
7 is provided with a heat spreader 18 for diffusing the heat of the first heating element 17, and a flat heat insulator 19 and a side heat insulator 20 for suppressing heat release are provided on the upper surface and the outer peripheral side surface. ,
Further, a first temperature sensor 21 for controlling the temperature of the first heating element is buried in the center of the heat diffusion body 18.

In this case, it is desirable that the distance hg between the first heating plate and the second heating plate be as small as possible in order to prevent the influence of convection from the surroundings from being applied to the inside. It is necessary to reduce the size to a level where there is no problem. Also, the method of controlling the temperature of the second heating plate must be optimized according to the size of the distance hg between the first heating plate and the second heating plate. That is, if the distance hg between the first heating plate and the second heating plate when the substrate 1 is heated is as large as 10 mm or more, the second
The temperature unevenness of the heating plate does not significantly affect the substrate temperature distribution. However, in order to make the accuracy of temperature uniformity of the substrate 1 ± 0.1 ° C. or less after narrowing the interval hg to 10 mm or less, the second Needs to have the same configuration as the first heating plate as shown in FIG. 1 or FIG.

That is, as shown in FIG. 4B, a second heating element 24 sandwiched between an inner peripheral side heat insulator 22 and an outer peripheral side heat insulator 23 is installed on the outer peripheral portion of the second heating plate. A second temperature sensor 25 for controlling the temperature of the second heating element 24 at the outer peripheral portion and near the surface or below the surface of the heat diffusion body 18
Buried.

Alternatively, as shown in FIG. 5, the up-down mechanisms 26, 2 are attached to the first heating plate or the second heating plate.
The distance between the plates is increased when the substrate 1 is conveyed, and the distance between the plates is reduced when the substrate is heated, thereby improving the heating efficiency. Here, a heat retaining ring 28 is provided on the outer peripheral portion of the second heating plate, and a gap between the first heating plate and the second heating plate is apparently sealed to thereby form the first heating plate or the second heating plate. The turbulence of the air flow that occurs when the vehicle moves can be reduced.

[0026]

As described in the above embodiments, according to the present invention, the temperature control is performed by using the individually controlled heating elements to accurately supply heat from the side and top surfaces of the substrate. Only by adjusting the temperature setting of the circuit, uniform substrate heating can be performed even at a wide range of heat treatment temperatures.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a heating plate unit according to a first embodiment having a basic configuration of the present invention.

FIG. 2 is a simplified circuit diagram of a control circuit of a second heating element and a temperature characteristic diagram of a resistor Rc.

FIGS. 3A and 3B are a cross-sectional view and a vertical cross-sectional view of a first heating plate unit provided with a plurality of second heating elements.

FIG. 4 is a longitudinal sectional view of an embodiment in which a second heating plate is added to a first heating plate.

FIG. 5 is a longitudinal sectional view of an embodiment in which a vertical mechanism and a heat retaining ring are added to the configuration of FIG. 4;

FIG. 6 is a configuration diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... thermal diffusion body, 3 ... 1st heating element, 4 ... plane heat insulator, 5 ... inner peripheral side heat insulator, 7 ... outer peripheral side heat insulator, 6
... Second heating element, 8 ... Insulation case, 9 ... First temperature sensor, 12 ... Second temperature sensor, 10, 13 ... Temperature control circuit, 11,14 ... Power supply, 15 ... Opening, 16 ... Shutter , 17: first heating element, 18: thermal diffuser, 19: plane heat insulator, 20: side heat insulator, 21: temperature sensor, 22 ...
Inner peripheral side heat insulator, 23 ... outer peripheral side heat insulator, 24 ... second heating element, 25 ... second temperature sensor, 26, 27 ... vertical mechanism, 28 ... heat retaining ring.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masafumi Kinyu 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (5)

[Claims] 1. A first heat generating element and a heat diffuser for diffusing heat of the first heat generating element are provided on an upper surface of the first heat generating element, and a heat release is suppressed on a lower surface. And a first temperature sensor for controlling the temperature of the first heating element is buried in a central portion of the heat diffusion body, and a heat insulation case is provided between the first heat sensor and the outside air. In the isolated first heating plate, a second heating element sandwiched between heat insulators is provided on an outer peripheral portion of the first heating plate, and the second heating element is disposed on an outer peripheral portion of the heat diffusion body.
A second temperature sensor for controlling the temperature of the heating element is embedded, a substrate is provided on the upper surface of the heat diffusion body, and the first heating element and the second heating element are independent of each other. A substrate heating apparatus characterized in that the temperature is adjusted by the temperature. 2. The method according to claim 1, wherein the second temperature sensor used for controlling the temperature of the second heating element is a resistor element such as a resistance thermometer or a thermistor having a characteristic whose resistance value largely changes depending on the temperature. The heating element is turned on by using a potential difference caused by a difference in resistance between the reference resistor and a reference resistor that can be adjusted by temperature.
The substrate heating apparatus according to claim 1, wherein -OFF control is performed. 3. The method according to claim 1, wherein the second heating element is divided into a plurality of parts, and the temperature is independently controlled, so that when the heat loss is different at each position of the outer peripheral part, the heat supply corresponding thereto is performed. The substrate heating apparatus according to claim 1 or 2, wherein 4. A second heating plate is provided at a position opposed to said first heating plate for the purpose of suppressing the release of heat from a surface direction of said substrate, and said second heating plate is connected to said second heating plate. 4. The substrate heating apparatus according to claim 1, wherein the substrate is heated at the same temperature as that of the first heating plate. 5. An up-and-down mechanism is provided on the first heating plate or the second heating plate, and an interval is provided between the first heating plate and the second heating plate when the substrate is transferred. In the case of heating the substrate, the distance between the first heating plate and the second heating plate is reduced, and the gap between the first heating plate and the second heating plate is apparently sealed. 5. The substrate heating apparatus according to claim 4, wherein a heat retaining ring capable of being mounted is provided on an outer peripheral portion of said second heating plate.