JP2003318076A - Method and device for heating and cooling substrate in vacuum - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify a device and enhance the process time by using a substrate holder in a heating and cooling treatment in a vacuum. <P>SOLUTION: In a thermal treating method and device for heating and cooling a substrate in a vacuum, the substrate is placed on the substrate holder in a chamber in a vacuum, to heat and cool the substrate holder, thereby simply heating and cooling the substrate in a short process time. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heating and cooling of a substrate in a vacuum, and more particularly to a method and apparatus for heating and cooling a substrate by heating and cooling a substrate plate.

[0002]

2. Description of the Related Art As a method of forming a film such as a resist, there is a method of forming a film by applying a film material onto a wafer or a glass substrate by using a method such as spin coating or slit coating. However, it is difficult to form the film uniformly because the material that can form the film only by coating has high viscosity. For this purpose, the film material is diluted with a certain solvent, the coating film is uniformly applied, and then the diluted solvent is volatilized and removed by heating in the prebaking step to form the film.

In this method, the ratio of the diluent solvent and the solid content of the film material is important. For example, in the case of a liquid having a solid content concentration of 50%, the coating film to be applied is about twice the final film thickness. Become. In thin film formation, the final film thickness is thin, so the applied film can be thin, but the final film thickness is several tens of μm.
In the case of thick film coating, the coating film to be applied often has a thickness of several hundred μm.

When the coating film becomes thick, such as thick film coating, film deformation occurs due to the flow of the coating film until the film formation due to the amount, viscosity and pre-baking conditions of the liquid, and the film thickness of the final formed film. It deteriorates distribution and surface roughness.

Therefore, as a method for forming a thick film, a method of forming a thick film by repeatedly applying thin film coating or a solution diluted with a quick-drying solvent is used, and after forming a coating film, the solvent is volatilized as quickly as possible. Then, there is a method of forming a smooth thick film by suppressing the film deformation from the coating film to the film formation as much as possible. Further, from the pre-baking method, it is considered that the film temperature during baking is precisely controlled to prevent the deterioration of the film thickness distribution.

[0006]

However, the method of forming a thick film by applying thin film coatings repeatedly has a problem that the number of coating films and pre-baking steps is increased and the tact becomes long. In addition, when it is difficult to apply the resist on the resist, for example, when the water-repellent film is repeatedly applied, the lower film may repel the upper film and the film may not be formed. .

When a wafer or glass substrate coated with a coating film is placed on a hot plate and the solvent is volatilized by heating, the temperature of the atmosphere near the film rises under atmospheric pressure, and Convection occurs. In the state where the coating film itself has low viscosity and the viscosity is lowered by heating,
The surface of the coating film is exposed to the air current generated by this convection, which causes the surface to become rough. As a result, both the film thickness distribution and the surface roughness deteriorate. Further, even in the depth direction of the coating film, a temperature difference occurs due to heat radiation from the surface and heating from the lower portion, and the liquid itself causes convection. This is also
Deteriorates film thickness distribution and surface roughness.

Therefore, as a countermeasure by the baking method, for example, the method disclosed in Japanese Patent Application Laid-Open No. 7-254545 is used to control the temperature gradient, the heating / cooling speed by controlling the temperature rising / falling rates during heating and cooling, and the film. It is possible to prevent the deterioration of the thickness distribution. However, even if this method is used in the atmosphere or in a nitrogen atmosphere at atmospheric pressure, for example, if the heating speed is slowed to lower the temperature gradient and the temperature rise rate is lowered, the solvent does not evaporate easily. However, the holding time in the low viscosity state becomes long, and as a result, the liquid flows, so that the film thickness distribution deteriorates. Further, when the heating speed is increased and the temperature increase rate is increased, the temperature gradient in the film thickness direction becomes steep and convection of the film occurs, resulting in deterioration of the film thickness distribution. In any case, since convection of the atmosphere cannot be prevented under atmospheric pressure, deterioration of the film thickness distribution will occur due to convection of the atmosphere. It is difficult to restore the roughened film surface by temperature control by controlling the film temperature during temperature decrease, and it is important how to keep the film thickness distribution good during temperature increase. After all, under atmospheric pressure, it is difficult to prevent the film thickness distribution of the thick film from being deteriorated by the pre-baking method.

[0009]

In order to solve the above-mentioned problems, the present invention comprises heating a coating film formed on a substrate in a vacuum to volatilize a solvent and then cooling the film in a vacuum. In order to prevent the film thickness distribution from deteriorating by opening to the atmosphere, the heating is stopped by moving the substrate holder away from the hot plate without changing the hot plate temperature, and the substrate plate is brought into contact with the upper cooling unit. By cooling the substrate by cooling the substrate, the substrate can be rapidly cooled even in a vacuum. As a result, the film deformation due to atmospheric pressure change is suppressed and the heating plate temperature is not changed, so that the plate temperature rise and fall time is eliminated, and heat conduction by heat transfer is realized in a vacuum, thereby enabling tact up.

The solvent in the coating film is volatilized as soon as possible,
In addition, in order to minimize the flow of the coating film during the pre-baking due to the non-uniform heat distribution of the coating film and the atmosphere, it is necessary to perform the pre-baking in forming the thick film in vacuum.

Since the gas in the vicinity of the film is thin in a vacuum,
Convection due to heat can be suppressed, undulations on the film surface can be prevented, and deterioration in film thickness distribution and film surface roughness can be prevented. Further, the heat insulating effect of the vacuum suppresses the outflow of heat from the surface of the coating film, and the thermal gradient in the depth direction of the coating film becomes small. As a result, heat convection of the coating film itself is prevented, and deterioration of the film thickness distribution and surface roughness can be prevented.

Further, by prebaking under reduced pressure, a large amount of solvent can be removed faster. Since the boiling point of the solvent in the coating film decreases in vacuum compared to prebaking under atmospheric pressure, the boiling point reaches faster in vacuum even if the temperature of the film is the same. As a result, the curing of the film is accelerated due to the reduction of the solvent, the residual amount of the solvent in the final coated film is reduced, and the deterioration of the film thickness distribution due to the flow of the coating film and the roughness of the film surface can be reduced.

However, in the pre-baking process in a vacuum, it is necessary to return the atmosphere in a reduced pressure state to the atmospheric pressure when the work is taken out after the vacuum heating. At this time, if the workpiece is leaked in a heated state, there is a problem that the surface of the film becomes rough for the object whose film viscosity is low at a high temperature because the film itself becomes soft. The air flow at the time of the leak affects the soft thick film, and even if the air flow is not directly applied to the film surface,
Roughening of the film surface occurs due to the influence of the pressure change of the atmosphere. Applying pressure while the film is soft means the film thickness distribution,
It deteriorates the surface roughness of the film surface. Therefore, it is necessary to cool the film before opening it to the atmosphere to prevent film deformation due to opening to the atmosphere.

Since the cooling method is also in a vacuum environment, the heat transfer due to the physical properties of the atmosphere and the heat transfer due to convection are significantly reduced, and the heat transfer due to radiation becomes dominant. Therefore, it is difficult to cool the work in a vacuum. As a method of cooling the work, for example, a method of cooling the heating plate with a coolant or the like and thereby cooling the work can be considered. When the work and the heating plate are in contact with each other, the cooling of the work follows the cooling of the heating plate, and if the heating plate cools, the work also cools. In this case, the cooling rate of the work under vacuum depends on the cooling rate of the heating plate. However, in this method, the heating plate itself needs to be cooled, so that there is a problem that the cooling time of the work becomes longer due to the cooling rate of the heating plate compared to the case where only the work is cooled. Since it is necessary to raise the heating plate temperature again when heating, the tact becomes longer. Further, in order to increase the cooling rate of the heating plate, for example, it is necessary to create a pipe through which a refrigerant passes in the heating plate, which complicates the structure.
This increases the cost of the device.

Therefore, when considering a cooling method that does not depend on the temperature of the heating plate, for example, it is conceivable to install another cooling plate and move the heated work there to cool it. However, in this case, the size of the vacuum chamber becomes large, and it is necessary to install a transfer device in the vacuum chamber, which makes the device large and complicated, and increases the cost. Therefore, it is considered that the cooling plate is installed above the heating plate, the work is lifted to separate the work from the heating plate, and the work is cooled by being close to the cooling plate installed above. In the atmosphere, heat transfer by atmospheric gas and heat transfer by convection are the main heat transfer parameters.
Since heat transfer by this is easily performed, the work can be quickly cooled only by being close to the cooling plate. However, in a vacuum, heat transfer due to the atmosphere is small, so even if the workpiece is brought close to the cooling plate,
The cooling rate becomes slow.

Further, as in the method of Japanese Patent Laid-Open No. 2001-085440, a method of providing a heat shielding shutter between a heating source and a work has been proposed as a means for stopping heating, but the shutter is provided in a vacuum chamber. If the shutter is moved on the workpiece, it is necessary to take measures against particles from the movable part, which may lead to new problems such as complicated structure and particle problem. .

Therefore, it is considered that the substrate is heated and cooled by setting the substrate holder, placing the substrate on the substrate holder, and heating and cooling the substrate holder.

In order to increase the heating / cooling speed of the substrate holder, a material having a high thermal conductivity is used for the substrate holder. At the time of heating, the substrate holder is placed on the heating plate to heat the substrate holder, thereby heating the substrate. In order to increase the heating efficiency, the surface of the heating plate and the surface of the substrate holder that contacts the heating plate are mirror-finished to increase the heat transfer efficiency during contact.

At the time of cooling, the heating is stopped by separating the substrate holder from the heating plate. Since it is in a vacuum, the heat transfer rate drops sharply when the substrate plate is separated from the heating plate. By subjecting the surface of the substrate holder, which faces the heating plate, and the surface of the heating plate to mirror finishing or plating with low emissivity, it is possible to suppress heat transfer of radiation that is dominant under vacuum, As a result, the heating can be stopped only by slightly separating it from the heating plate, and it is not necessary to insert a special device such as a heat shield shutter, and the space of the device can be saved.
Further, along with this, it is not necessary to install a movable portion above the substrate, and the particle problem can be reduced. Further, since it is not necessary to lower the temperature of the heating plate, it becomes possible to always keep the heating plate temperature constant, and it is possible to improve the tact time. Further, by bringing the cooling unit into contact with the substrate holder separated from the heating plate, contact heat transfer is realized in a vacuum, and the substrate holder can be rapidly cooled. Thereby, the substrate holder can be rapidly cooled in a vacuum, and the substrate on the substrate holder can be rapidly cooled.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1A shows the structure of a film forming apparatus according to an embodiment of the present invention. In the figure, 1
01 is a vacuum chamber, 102 is a substrate such as a silicon wafer, 103 is a substrate holder, 104 is a heating plate, 105 is a cooling unit, 106 is a support pin, 107
Is a lifting controller, 108 is a lifting motor, 109
Is a cooling unit controller, 110 is a vacuum pump,
111 is a heating controller. The substrate 102 coated with a resist is set on the substrate holder 103.
The substrate holder has a round shape, a square shape, or the like depending on the shape of the substrate. As a method of fixing the substrate, a groove is formed in the substrate shape or pins or the like are erected on the substrate holder to prevent the substrate from moving so that the cooling unit does not hit the substrate during cooling. The inside of the chamber 101 is decompressed by performing vacuum exhaustion with the vacuum pump 110. The board holder is driven by the lifting controller 107 to drive the motor 108 to lower the support pins 106, thereby
It is installed on the heating plate 104. The timing of depressurization in the vacuum chamber and heating of the substrate holder differ depending on the process, and there are heating after completion of depressurization, heating while depressurizing, and depressurization after heating. By bringing the substrate holder into contact with the heating plate, the heating plate heats the substrate holder, thereby heating the substrate on the substrate holder. When the heating is completed, the support pins are raised to bring the substrate holder into contact with the upper cooling unit 105 as shown in FIG. It is desirable for the cooling unit to have as many contact surfaces as possible with the substrate holder. For example, if the substrate holder has a circular shape, the cooling unit is also processed into a circular shape so as to contact the entire outer peripheral portion of the substrate holder that is not hidden by the substrate. Is preferred. As a cooling method of the cooling unit, there are a method of bringing a part of the unit into contact with the upper surface of the vacuum chamber and cooling the upper surface of the chamber by air cooling, a method of passing a water cooling pipe through the cooling unit, and forced water cooling. In addition, the number of support pins is set to be in a heat insulating state or a state close thereto with respect to the heating plate, and the number of support pins is 3 in order to maintain contact with the cooling plate during cooling.
Better than a book. The substrate holder is cooled by bringing the substrate holder into contact with the cooling unit, and the substrate on the substrate holder is cooled. After cooling is complete,
The substrate is taken out, and the baking process is completed. When cooling the substrate in vacuum, the substrate holder is brought into contact with the cooling unit to perform cooling by heat conduction, so the cooling rate in vacuum is increased and the cooling time can be shortened. Since it is not necessary to change the temperature, it is possible to improve the tact time because it is immediately put into the next heating step.

(Example 1) A silicon wafer having a diameter of 150 mm was coated with a solution of the following composition by a slit coating method so as to have a coating film thickness of 250 μm, and prebaked in vacuum to a thickness of about 120 μm. I baked it.

Composition EHPE-3150 (trade name, manufactured by Daicel Chemical Industries, Ltd.) 100 parts by weight SP-170 (trade name, manufactured by Asahi Denka Co., Ltd.) 1.5 parts by weight Diethylene glycol dimethyl ether 100 parts by weight Coating film Figure 1 shows a silicon wafer coated with 250 μm of
The vacuum chamber 101 shown in (a) is placed on a substrate holder 103 installed on a vertically movable support pin 106, and the inside of the chamber is evacuated by a vacuum pump 110. By lowering the support pin 106 as shown in FIG. 1B, the substrate holder is placed on the heating plate 104,
Heat in a vacuum bake oven at a heating plate temperature of 100 ° C. for 6 minutes. If the material of the substrate holder is copper, which has high thermal conductivity, the rate of temperature rise can be increased.
After that, the support pins 106 are raised to bring the substrate holder into contact with the upper cooling unit 105 as shown in FIG. 1A, and the substrate holder is cooled to cool the substrate. The wafer was cooled to a temperature of 60 ° C., opened to the atmosphere, and taken out. The film surface formed by vacuum baking was uniform without being deformed by the pressure applied to the atmosphere.

(Example 2) A silicon wafer having a diameter of 150 mm was coated with a solution having the same composition as in Example 1 by a slit coating method so as to have a coating film thickness of 250 μm.
Baking was performed by pre-baking in vacuum so that the thickness was about 120 μm.

A silicon wafer coated with a coating film of 250 μm is placed on the substrate holder 203 installed in the cooling unit 205 in the vacuum chamber 201 shown in FIG. 2A, and the chamber is evacuated by the vacuum pump 209. To do. Lifting unit 2 by lifting controller 206
At 07, the heating plate 204 is raised as shown in FIG. 2B to bring the heating plate into contact with the substrate holder,
Further, after the contact, the substrate holder is further lifted by the heating plate to be separated from the cooling unit 205 to heat the substrate holder, and thereby the substrate is heated. Heat in a vacuum bake oven at a heating plate temperature of 100 ° C. for 6 minutes. After that, the heating plate 204 is lowered by the elevating unit 207, the substrate holder 203 is placed on the cooling unit as shown in FIG. 2A, and further lowered to separate the heating plate 204 and the substrate holder 203, and the heating is finished and the cooling is finished. Are started at the same time. Wafer temperature is 60 ° C
The wafer was taken out. The film surface formed by vacuum baking was uniform without being deformed by the pressure applied to the atmosphere.

(Comparative Example 1) A silicon wafer having a diameter of 150 mm was coated with a solution having the same composition as in Example 1 by a slit coating method so as to have a coating film thickness of 250 μm.
Baking was performed by pre-baking in vacuum so that the thickness was about 120 μm. A silicon wafer coated with a coating film of 250 μm is placed on the substrate holder 103 installed on the vertically movable support pins 106 in the vacuum chamber 101 shown in FIG. 1, and the inside of the chamber is evacuated by the vacuum pump 109. . By lowering the support pin 106,
The substrate holder is placed on the heating plate 104 and heated in a vacuum baking oven at a heating plate temperature of 100 ° C. for 6 minutes. After that, open the atmosphere while heating the substrate,
The wafer was taken out. It was observed that the formed film surface was deformed by the pressure applied to the atmosphere, the surface was roughened by visual observation, and the film thickness distribution was deteriorated over the entire film surface.

(Comparative Example 2) A silicon wafer having a diameter of 150 mm was coated with a solution having the same composition as in Example 1 by a slit coating method so as to have a coating film thickness of 250 μm.
It was baked by prebaking in the atmosphere so that the thickness was about 120 μm.

A silicon wafer coated with a coating film of 250 μm is supported by a support pin 304 that can be moved up and down as shown in FIG.
The wafer is placed on the heating plate 302 and heated at a heating plate temperature of 100 ° C. for 6 minutes under atmospheric pressure, and then the support pins 304 are raised by the motor 305 to bring the wafer closer to the upper cooling plate 303 and cool it. The wafer temperature was cooled to 60 ° C., and the wafer was taken out. It was observed that the surface of the film formed by prebaking in the air was roughened by visual observation, and the film thickness distribution was deteriorated over the entire surface of the film.

[0028]

As described above, according to the present invention,
When a substrate is heated and cooled in a vacuum, the substrate holder can be used to heat and cool the substrate to increase the cycle time of the process. In addition, in the film forming method, in particular, after prebaking in vacuum, film deformation due to pressure change when opening to the atmosphere, roughness of the film surface due to it, and deterioration of film thickness distribution are prevented, and the film is formed by prebaking in vacuum. Good film extraction can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment and an example of the present invention.

FIG. 2 is a diagram illustrating an experiment in an example.

[Explanation of symbols]

101 vacuum chamber 102 substrate 103 substrate plate 104 heating plate 105 Cooling unit 106 Support pin 107 Lift controller 108 Lifting motor 109 Cooling controller 110 vacuum pump 111 heating controller 201 vacuum chamber 202 substrate 203 substrate holder 204 heating plate 205 cooling unit 206 Lift controller 207 Lifting unit 208 Cooling controller 209 vacuum pump 210 heating controller

Claims (5)

[Claims] 1. In a heat treatment method of heating and cooling a substrate in a vacuum, (1) placing the substrate on a substrate holder in a vacuum chamber, and (2) placing the substrate holder on a heating plate, Heating the substrate to heat the substrate, (3) after heating is completed, the substrate holder is separated from the heating plate to finish heating, and (4) the substrate holder is brought into contact with the cooling unit to cool the substrate holder. And a step of cooling the substrate by performing a heating and cooling method and apparatus for the substrate. 2. An apparatus for performing the method of heating and cooling the substrate, which includes a substrate holder for holding the substrate in a vacuum chamber, a heating plate for heating the substrate holder, a cooling unit for cooling the substrate holder, and a support pin. Of the substrate heating and cooling device having a mechanism for moving the substrate plate in the vacuum chamber. 3. A substrate heating / cooling device, wherein the substrate holder is made of a material having a high thermal conductivity. 4. An apparatus for heating and cooling a substrate, characterized in that, in the substrate holder, a contact surface with a heating plate is a surface having a low emissivity by mirror finishing or plating treatment, or both. 5. The surface of the heating plate is made low by mirror finishing or plating in order to increase heat transfer efficiency when heating the substrate holder and reduce heat transfer to the substrate holder when the substrate holder is peeled off. Substrate heating / cooling device with emissivity surface.