JPH06310416A - Method and equipment for baking semiconductor wafer - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To improve the processed shape of photoresist in the photolithography process. [Structure] The heat source 2 is provided on the main surface side and the back surface side of the semiconductor wafer 4.
Is provided and the temperature conditions of the main surface side and the back surface side are changed to bake the photoresist applied to the main surface. In the pre-baking, the main surface side is baked at a temperature higher than the back surface side, and in the baking after the exposure and before the development, the back surface side is baked at a higher temperature than the main surface side. The semiconductor wafer is pre-baked while supplying water to the photoresist of the semiconductor wafer placed on the baking device. [Effect] In the pre-baking, the concentration of the remaining organic solvent is low near the surface and high near the base, the solubility near the surface is lowered, and the solubility is improved near the base, so that the film loss and the resist residue are reduced. In the bake after the exposure and before the development, the standing wave generated at the exposure boundary of the resist film is flattened. Moisture is supplied at the time of prebaking to accelerate the reaction of the photosensitive groups of the photoresist.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the baking of semiconductor wafers, and more particularly to a technique effective when applied to the baking of semiconductor wafers prior to the completion of photoresist application and development.

[0002]

2. Description of the Related Art In a photolithography process for microfabrication of a semiconductor wafer, a photoresist is applied to the main surface of the semiconductor wafer, a photoresist having a predetermined pattern is aligned with the photoresist, and then the mask pattern is exposed to the photoresist. The soluble part is dissolved and removed with to form a photoresist pattern, and after the wiring pattern is formed on the main surface of the semiconductor wafer by etching using the formed resist pattern as a mask, the main surface of the semiconductor wafer is removed by removing the resist pattern. Wiring and the like are formed on.

Various baking is performed on the semiconductor wafer during each of the above-mentioned processes of the lithography process. As such a baking, a pre-baking for evaporating the water existing on the surface of the semiconductor wafer before applying the photoresist to improve the adhesiveness between the base of the semiconductor wafer and the applied resist film, and after applying the photoresist , Pre-exposure bake to increase the adhesiveness between the resist film and the base and remove the organic solvent in the applied photoresist, and post-exposure bake to improve the adhesion of the pattern to the base after the photoresist exposure. After the development, the post-development baking is performed to improve the adhesion between the resist film and the base, improve the chemical resistance, and remove the developing solution inside the photoresist during the development.

Conventionally, these bakings are carried out by heating a semiconductor wafer in a dry atmosphere in a baking apparatus, and the semiconductor is placed in a state of being in close contact with or slightly floating on a hot plate which is a heat source with its main surface side facing upward. A wafer is placed and heated from the back side of the semiconductor wafer at a constant temperature for a fixed time, and the temperature of the main surface of the semiconductor wafer is not controlled.

[0005]

With the miniaturization of semiconductor devices, the resist film in the photolithography process is required to be processed finely and highly accurately in terms of both dimensions and shape. Regarding the processed shape of the resist film, the planar shape accurately corresponds to the mask pattern,
Ideally, the cross-sectional shape is rectangular.

However, in reality, there is a difference in the progress of dissolution between the surface of the resist film and the vicinity of the base, so that the photoresist that should be dissolved remains as it approaches the base. Therefore, the resist film is formed in a trapezoidal shape or a triangular shape whose bottom surface is expanded. On the other hand, on the surface of the resist film, the photoresist, which should remain, is dissolved, causing film loss and deteriorating the shape.

Further, during the exposure of the photoresist, a standing wave is generated inside the resist due to the interference effect of the incident light and the multiple reflection light from the photoresist base surface, the substrate surface, etc., so that the intensity of the light is increased. At the boundary of the part, the exposure is performed with wavy unevenness. Therefore, unevenness is generated on the side surface of the resist film after development, and the formability is deteriorated.

Further, in the case of, for example, a positive photoresist, the photosensitive group of the photoresist causes a photoreaction upon exposure and is solubilized to form a resist pattern. At this time, the exposed photosensitive group reacts. However, it may become insoluble and the shape of the resist pattern may deteriorate.

With the progress of miniaturization of element patterns of semiconductor devices, the resist patterns have become thinner and the intervals between them have become narrower. Since the deterioration or deterioration of the shape described above becomes an obstacle to pattern miniaturization, it is an issue to further improve the precision of the processed shape of the resist film.

An object of the present invention is to provide a technique capable of improving the processed shape of the photoresist in the photolithography process.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0012]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

A heat source is provided on the main surface side and the back surface side of the semiconductor wafer placed on the baking device, and the temperature conditions of the main surface side and the back surface side of the semiconductor wafer are changed to bake the photoresist applied to the main surface. To do. Specifically, in the pre-bake before exposure, the main surface side is baked at a higher temperature than the back surface side, and in the post-exposure pre-baking, the back surface side is baked at a higher temperature than the main surface side.

The semiconductor wafer is baked while supplying water to the photoresist of the semiconductor wafer placed on the baking device.

[0015]

According to the above-mentioned means, in the pre-baking, the concentration of the organic solvent remaining in the resist film can be made low near the surface and high near the base. Therefore, the solubility of the resist film in the developing solution decreases near the surface and improves near the base, so that the film loss and the resist residue are decreased, and the processed shape of the resist pattern can be improved.

Since the organic solvent remaining in the vicinity of the base of the resist film is mainly heated in the baking after the exposure and before the development, when the electrons of the solvent in the vicinity of the base are warmed and move toward the surface, the resist film exposure boundary is exposed. Since the standing wave generated in 1) is flattened, the processed shape of the resist pattern can be improved.

By supplying water to the photoresist at the time of prebaking, the reaction of the photosensitive groups of the photoresist is promoted, so that a resist pattern corresponding to the mask pattern can be obtained more accurately.

The structure of the present invention will be described below together with embodiments. In all the drawings for explaining the embodiments, parts having the same function are designated by the same reference numerals, and repeated description thereof will be omitted.

[0019]

(Embodiment 1) FIG. 1 is a view showing the schematic arrangement of a baking apparatus which is an embodiment of the present invention. This embodiment is a baking apparatus used for pre-baking, in which heat sources are provided on the upper and lower parts of the semiconductor wafer, the main surface side of the semiconductor wafer is heated by the upper heating source, and the back surface side is the main surface by the lower heat source. Make it cooler than the side.

In the figure, 1 is a base, which is cylindrical and has a cooling plate 2 as a lower heat source on its upper surface. The cooling plate 2 is cooled by circulating the cooling water from the cooling device 3 inside. The semiconductor wafer 4 is mounted on the cooling plate 2 in a state of slightly floating via the wafer holding pins 5. The temperature of the cooling plate 2 is adjusted by changing the temperature and amount of the cooling water, and the temperature of the semiconductor wafer 4 is controlled.

Reference numeral 6 denotes a cover for covering the upper surface of the base 1. The cover 6 is formed in a hollow conical shape having a cylindrical peripheral wall in the lower part, and is made of a heat insulating material, and its inner surface has a structure with little radiation. Has become. An air supply pipe 7 and a humidification pipe 8 are connected to the top of the cover 6. The air supply pipe 7 supplies nitrogen gas supplied from a gas supply device (not shown) into the cover 6.

Nitrogen gas is heated by a heating device 9 provided in the middle of the air supply pipe 7 as an upper heat source, and the semiconductor wafer 4 is baked by the heated nitrogen gas. A temperature sensor 10 is provided in the cover 6, and the control device 11 controls the heating device 9 based on the temperature information from the temperature sensor 10 to adjust the temperature of the supplied nitrogen gas. Control the temperature.

The nitrogen gas supplied from the top of the cover 6 spreads over the entire surface of the semiconductor wafer 4 along the conical slope to heat the photoresist, so that the entire surface of the semiconductor wafer 4 can be baked uniformly.

A humidifying pipe 8 is provided as a water supply means, and pure water vapor generated by a vapor supply device (not shown) is supplied into the cover 6. The amount of steam is controlled by a controller 12 provided in the middle of the humidifying pipe 8.

Since the humidifying pipe 8 is provided on the top of the conical cover 6 adjacent to the air supply pipe 7, the supplied vapor spreads over the entire surface of the semiconductor wafer 4 and uniformly supplies the moisture to the photoresist. You can

An exhaust pipe 13 discharges the nitrogen gas supplied from the air supply pipe 7 and circulated in the cover 6 to the outside. During this discharge, the gaseous organic solvent removed from the photoresist by baking is discharged together with the nitrogen gas.

In the pre-baking by the apparatus of this embodiment, the main surface side of the semiconductor wafer 4 is heated by the nitrogen gas heated by the heating device 9 which is the upper heat source, and at the same time, the semiconductor wafer 4 is heated by the cooling plate 2 which is the lower heat source. By cooling the back surface side, the temperature of the back surface side can be made lower than the temperature of the main surface side while heating the semiconductor wafer 4 in the entire apparatus. As a result, the temperature of the resist film applied to the main surface of the semiconductor wafer 4 becomes higher on the surface side than on the base side. Therefore, the solvent remaining near the surface is removed at a higher rate than the solvent remaining near the base. Due to the difference in solvent concentration thus generated,
During development, the amount of solvent remaining in the vicinity of the surface is small, which makes it difficult to proceed with the development. Therefore, the film loss on the surface of the resist film is prevented, and the resist residue near the base is reduced.

Further, by supplying vaporized pure water and supplying water to the photoresist, it is possible to accelerate the exposure and solubilization of the photosensitive group, so that a resist pattern more accurately corresponding to the mask pattern can be obtained. be able to.

Although the humidifying pipe 8 is opened in the cover 6 in this embodiment, it is also possible to open the humidifying pipe in the air supply pipe and supply the nitrogen gas to which water has been supplied into the cover.

(Embodiment 2) FIG. 2 is a diagram showing a schematic construction of a baking apparatus which is another embodiment of the present invention. The present embodiment is a baking device used for baking after exposure and before development, in which heat sources are provided in the upper and lower portions of the semiconductor wafer, the back side of the semiconductor wafer is heated by the lower heating source, and the cold heat source in the upper portion. Make the temperature of the main surface lower than that of the back surface.

In the figure, 1 is a base, which is cylindrical and has a hot plate 14 as a lower heat source on its upper surface. The hot plate 14 is heated by an electric heater (not shown) housed inside. The controller 15 controls the temperature of the hot plate 14 and controls the temperature of the semiconductor wafer 4.

Reference numeral 16 is a cover for covering the upper surface of the base 1.
The cover 16 is formed in a hollow cylindrical shape whose upper part is closed,
A heat-insulating material is used, and the inner surface has a structure with less radiation.

A cooling plate 2 is provided as an upper heat source in the cover 16, and the semiconductor wafer 4 is cooled by the cooling plate 2. 3 is a cooling device.

The air supply pipe 7 is connected to the center of the upper portion of the cover 16 and supplies nitrogen gas supplied from a gas supply device (not shown) into the cover 16. Reference numeral 13 is an exhaust pipe.

In the baking after the exposure and the development by the apparatus of this embodiment, the back surface of the semiconductor wafer 4 is heated by the hot plate 14 which is the lower heat source, and at the same time, the main surface of the semiconductor wafer 4 is heated by the cooling plate 2 which is the upper heat source. By cooling the side, baking is performed while heating the semiconductor wafer 4 in the entire apparatus while lowering the temperature on the main surface side with respect to the temperature on the back surface side. As a result, the temperature of the resist film applied to the main surface of the semiconductor wafer 4 is lower on the surface side than on the base side. Therefore, the organic solvent remaining near the base of the resist film is mainly heated,
When the electrons of the solvent near the base are warmed and move toward the surface, the standing wave generated in the resist film can be flattened and the processed shape of the resist pattern can be improved.

As described above, the inventions made by the present inventor are
Although the present invention has been specifically described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

For example, in the above-described embodiment, the heat source and the cold heat source are provided as heat sources. However, when the set temperature difference is small, the heat source is adopted instead of the cold heat source, and the temperature of both heat sources is changed. By changing the conditions, it is possible to change the temperature conditions of the main surface side and the back surface side of the semiconductor wafer. In this configuration, the baking time can be shortened by heating from both the main surface side and the back surface side.

It is also possible to implement the present invention with a structure in which a cooling device is provided in the air supply pipe instead of the cooling plate as the cold heat source to cool the nitrogen gas. Also,
It is also possible to implement the present invention as a configuration in which nitrogen gas is supplied from the base side as a lower heat source, and a cooling device or a heating device is provided in the nitrogen gas supply pipe to cool or heat the nitrogen gas.

Further, a heating means and a cooling means are provided as an upper heat source, a heating means and a cooling means are also provided as a lower heat source, and the respective settings are changed so that the pre-baking and the post-exposure bake are performed. It is also possible to adopt a configuration in which one device can be used.

[0040]

The effects obtained by the typical ones of the inventions disclosed in this application will be briefly described as follows.
It is as follows.

(1) Since the main surface side of the semiconductor wafer is heated at a temperature higher than that of the back surface side during prebaking, the concentration of the organic solvent remaining in the resist film is low near the surface and high near the base, The solubility of the above in the developing solution is lowered near the surface and is improved near the base.

(2) During the baking after the exposure and before the development, the back surface side of the semiconductor wafer is heated at a temperature higher than that of the main surface side to reduce the unevenness of the exposed portion boundary due to the standing wave inside the resist film. There is an effect that can be.

(3) By supplying water to the photoresist at the time of prebaking, it is possible to accelerate the reaction of the photosensitive groups of the photoresist and obtain an accurate resist pattern.

(4) The above effects (1), (2), (3)
Therefore, there is an effect that the shape of the photoresist is improved.

(5) From the above effect (4), the dimensional accuracy of the processed shape of the resist film can be improved, so that the yield and quality of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a semiconductor wafer baking apparatus that is an embodiment of the present invention;

FIG. 2 is a diagram showing a schematic configuration of a semiconductor wafer baking apparatus that is another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Cooling plate (heat source), 3 ... Cooling device (heat source), 4 ... Semiconductor wafer, 5 ... Wafer holding pin, 6,16 ... Cover, 7 ... Air supply pipe, 8 ... Humidification pipe (moisture supply) Means), 9 ... Heating device (heat source), 10 ... Temperature sensor, 11, 12, 15 ... Control device, 13 ... Exhaust pipe, 14
… Hot plate (heat source).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Kanai 2-3-3 Fujibashi, Ome-shi, Tokyo 2 Hitachi Hitachi Electronics Co., Ltd. (72) Inventor Keizo Kuroiwa 5-20 Komimizuhoncho, Kodaira, Tokyo No. 1 Incorporated company Hitachi Ltd. Semiconductor Division (72) Inventor Shinya Ogane 3-3 Fujibashi, Ome-shi, Tokyo 2 Hitachi Tokyo Electronics Co., Ltd. (72) Masahiro Ishiuchi 3-chome, Fujibashi, Ome-shi, Tokyo 3-2 Hitachi Tokyo Electronics Co., Ltd. (72) Inventor Susumu Komoritani 5-201-1, Kamimizuhonmachi, Kodaira-shi, Tokyo Within Hitachi, Ltd. Semiconductor Business Division

Claims (6)

[Claims] 1. A method of baking a semiconductor wafer after applying photoresist and before development, wherein the semiconductor wafer is heated by providing a temperature difference between the main surface side and the back surface side. 2. A baking device for a semiconductor wafer after photoresist application and before development, wherein a heat source capable of setting temperature conditions at arbitrary temperatures is provided on the main surface side and the back surface side of the semiconductor wafer, respectively. Wafer baking device. 3. The baking method or the baking apparatus for a semiconductor wafer according to claim 1, wherein the semiconductor wafer main surface side is heated to a temperature higher than the back surface side after the photoresist application and before the exposure. 4. The baking method or the baking apparatus for a semiconductor wafer according to claim 1, wherein the back surface side of the semiconductor wafer is heated to a temperature higher than the main surface side after the photoresist exposure and before the development. 5. A method of baking a semiconductor wafer after photoresist application and before exposure, wherein water is supplied to the applied photoresist. 6. A baking device for a semiconductor wafer after photoresist application and before exposure, comprising a supply means for supplying water to the applied photoresist.