JPH02101470A - Method for heat treating photosensitive resist - Google Patents

Abstract

PURPOSE:To facilitate temperature control of a heat conducting medium, to shorten heat treatment time, to enhance efficiency, and to enable a wafer substrate to be cleaned of dust by heat treating a photosensitive resist formed on the substrate by using an inactive fluorinated liquid as the heat treating medium. CONSTITUTION:The inert fluorinated liquid to be used as the heat treating medium is stable even at a temperature as high as 150 deg.C and nonreactive with the wafer substrate and the resist, and very high in heat conductivity, thus permitting the temperature control of the medium to be made easy, a time required for heating the resist to a temperature necessary for the treatment to be shortened, and a treatment efficiency to be enhanced, and the medium to be very high in specific gravity as compared with gases used as the heat conducting medium, and dust attached to the wafer substrate, lower in specific gravity than the fluorinated medium to float up apart from the wafer and to be easily removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat treatment method for photosensitive resist, and in particular,
The present invention relates to a method of heat treating a resist film formed in a semiconductor manufacturing process.

[Prior Art] In the semiconductor device manufacturing process, in the process of forming a desired resist pattern, resist is used to improve the adhesion between the applied resist and the wafer substrate, or to remove organic solvents in the resist. A heat treatment process is required. One of these is a process called post-bake, which is a heat treatment after resist development that primarily aims to remove the organic solvent from the resist and improve the adhesion between the resist and the wafer substrate.

In the conventional post-bake resist pattern heat treatment method, a gas such as N2 or dry air is used as a thermal conductive medium to harden the desired resist pattern obtained through the 26i exposure and development process of the wafer substrate. , in a baking oven with temperature control function, approximately 150
Beta for 1 hour at ℃.

[Problems to be Solved by the Invention] FIG. 4 shows the state around the resist-covered wafer substrate when the developed resist pattern is heat-treated using the conventional resist heat-treating method as described above. It is a diagram.

As shown in FIG. 4, the heat transfer medium to the resist is N2
Alternatively, a gas such as dry air was used. However, since gas has low thermal conductivity, it is difficult to control the temperature when heat-treating the resist. In addition, there is a problem in that the time required to apply the temperature necessary for resist processing is long, and the heat treatment time for the resist is long, resulting in poor processing efficiency.

In order to solve these problems, it is necessary to use a substance with high thermal conductivity as a heat conductive medium in resist heat treatment, and one example of this is a liquid. However, such a liquid must be stable even at a temperature of about 150° C. required for pre-baking, and must not react with the resist or wafer substrate. Conventionally, there has been no liquid that satisfies the above conditions.

Furthermore, since gas has a very low specific gravity, as shown in Figure 4, the resist slag and other particles that adhere to the wafer substrate during resist development, which have a heavier specific gravity than the surrounding gas, are removed without leaving the wafer substrate. could not. For this reason, there is a problem in that when the resist is heat-treated, the dust is also heat-treated at the same time.

Conventionally, in order to remove dust to solve this problem, it was necessary to directly contact the resist, which resulted in further staining of the resist, and there was no suitable method.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to facilitate temperature control of a thermally conductive medium in a resist heat treatment process, shorten processing time and improve efficiency, and further improve the efficiency of a wafer substrate. The purpose is to provide a method for removing the above debris.

[Means for Solving the Problems] In order to achieve the above objects, the resist heat treatment method according to the present invention is a recently developed method that is stable even at high temperatures of about 150° C. and is suitable for wafer substrates and resists. An inert fluorine-based inert liquid that does not react with the heat transfer medium is used as a heat transfer medium.
This is what I used.

[Function] The fluorine-based inert liquid has a very high thermal conductivity and good thermal conductivity compared to gases conventionally used as heat transfer media. Therefore, by using a fluorine-based inert liquid as a heat transfer medium during resist heat treatment, the temperature of the heat transfer medium can be easily controlled, and the time required to provide the resist with the temperature required for processing is shortened. is,
Processing efficiency is improved.

Furthermore, the fluorine-based inert liquid has a specific gravity (1.7 to 2.0
) is very large. Therefore, when a wafer substrate is placed in a fluorine-based inert liquid as a heat conduction medium during resist heat treatment, dust with a specific gravity lower than the specific gravity of the liquid on the wafer substrate will float above the wafer substrate and be removed. Ru.

[Example] Figure 1 shows the area near the wafer substrate with a resist pattern during processing when a resist pattern obtained after development is heat-treated using an embodiment of the resist heat treatment method according to the present invention. FIG.

As shown in FIG. 1, a wafer substrate 1 having a resist pattern 2 obtained after development is left in a fluorine-based inert liquid 4 controlled at a temperature of about 150° C. necessary for heat treatment of the resist. Then, as shown in FIG.
The upper dust 3 floats up from the wafer substrate and is removed.

For example, if the dust 3 is resist dregs attached during development, the specific gravity is about 1.25. After being left in this state for 3 to 5 minutes, the resist patterned wafer substrate 1 is taken out of the fluorine-based inert liquid 4, and the fluorine-based inert liquid 4 adhering to the resist patterned wafer substrate 1 is removed. In addition,
An example of a fluorinated inert liquid is Fluorinert FC-43 (trade name), which has a specific gravity of 1.86 at 25°C.

FIG. 2 is a schematic diagram showing an example of a batch-type heat treatment apparatus for performing the above-described heat treatment method for a resist pattern after development. In FIG. 2, a plurality of resist-coated wafer substrates 1 are fixed to a wafer cassette 6 and moved into and out of a fluorine-based inert liquid 4 by an arm 7.

The fluorine-based inert liquid 4 is filtered by a filter device 8, and the temperature of the liquid is controlled by a temperature control device 5. Further, the temperature of the tank containing the liquid 4 is maintained by an overflow type constant temperature bath.

FIG. 3 shows the heat treatment of the resist according to the present invention in pre-bake, which is heat treatment of the resist after coating, and post-exposure bake, which is heat treatment after exposure to even out the distribution of the photosensitizer on the resist. 1 is a schematic diagram of an example of a single-wafer type heat treatment apparatus for applying an embodiment of the method; FIG. In FIG. 3, a resist-coated wafer substrate 1 adsorbed onto a spinner 11 is rotated at a low speed by the spinner 11 while a fluorine-based inert liquid 4 controlled at a desired temperature is dripped from a dripping nozzle 10. After several minutes, when the heat treatment is completed, dropping of the fluorine-based inert liquid 4 from the dripping nozzle 10 is stopped, and the spinner 11 is rotated at high speed to remove the fluorine-based inert gas 4.

In the above examples, the heat treatment according to the present invention was carried out using a batch heat treatment method as shown in FIG. 2 for post-baking. This is done in consideration of the fact that the wafer substrate is placed in a wafer cassette during development before post-baking.

Note that the fluorine-based inert liquid has the effect of improving the stability of the resist when used not only as a heat conduction medium in the heat treatment of the resist, but also as a storage medium for the resist-attached wafer after exposure. . In addition, when the same liquid is used as a storage medium for a wafer substrate before resist coating, the wafer substrate is not affected by moisture in the air, so the adhesion to the resist does not deteriorate during resist coating. It's also effective.

[Effects of the Invention] As described above, according to the present invention, it becomes easy to control the temperature JU of a thermally conductive medium, which has been difficult in the past, and the time required for conventional resist heat treatment can be significantly shortened. Processing efficiency is improved. Furthermore, it is possible to remove dust that could not be removed from the wafer substrate and was heat-treated at the same time as the resist.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the vicinity of a wafer substrate with a resist pattern during processing when the resist heat treatment method of one embodiment of the present invention is used for a resist pattern after development, and FIG. 2 is a diagram showing such a resist heat treatment. A schematic diagram of an example of a heat treatment apparatus for carrying out the knob method, and FIG. 3 is an example of a heat treatment apparatus necessary when the resist heat treatment method of an embodiment of the present invention is used for a resist after coating and a resist after exposure. FIG. 4 is a diagram showing the state around the resist-attached wafer MIN during processing when the conventional resist heat treatment method is used for the resist pattern after development. In the figure, 1 is a wafer substrate, 2 is a resist pattern after development, 3 is dust, 4 is a fluorine thread inert LFK body, 5 is a temperature control device, 6 is a wafer cassette, 7 is an arm, 8 is a filtration device, 9 1 is a constant temperature bath, 10 is a dropping nozzle, 11 is a spinner, and 12 is a gas. Note that the same symbols in the figures indicate the same or equivalent parts. First cause Figure 2

Claims (1)

[Claims] A method for heat-treating a photosensitive resist, the method comprising heat-treating the photosensitive resist on a substrate using a fluorine-based inert liquid as a heat-conducting medium.