JPH04313215A - Low-pressure or vacuum baking apparatus and baking treatment method - Google Patents

Abstract

PURPOSE:To obtain a low-pressure or vacuum baking apparatus and a baking treatment method which can evaporate a solvent in a resist film with good efficiency by reducing a pressure during a baking operation, which can lower a baking temperature as compared with that in conventional cases, which restrains a stress generated in a resist pattern and which can enhance the heat- resistant property of the resist film. CONSTITUTION:A hot plate 2 as a heating means is installed on a support stand 1; a semiconductor wafer 3 is placed on the hot plate 2. A resist film is formed on the semiconductor wafer 3 after a resist solution has been coated, exposed to light, developed and patterned during a photolithographic process. An over cover 4 is installed at the upper part of the hot plate 2 so as to cover the semiconductor wafer 3 airtightly. The pressure inside the airtight oven cover 4 is reduced to a pressure within a range from normal pressure to 10Torr by an evacuation means, e.g. vacuum pump 5.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a reduced pressure or vacuum baking device and a baking method, and more particularly to a reduced pressure or vacuum baking device and a baking method used for baking resist films, etc. in semiconductor manufacturing processes. .

0002

[Prior Art] Conventionally, in the semiconductor manufacturing process, a resist solution is applied onto a semiconductor wafer, the solvent is removed by pre-baking, then exposure and development are performed, and post-baking is performed to remove the solvent and water. was forming. Further, wet etching is performed through this resist film, post-baking is performed to remove the etching solution, dry etching is performed, and then the resist film is removed.

FIG. 2 is a schematic cross-sectional view showing a baking device that performs baking on a hot plate in a baking method used in conventional photolithography. In the figure, a semiconductor wafer 3 is placed on a hot plate 2 provided on a support stand 1. An oven cover 4 is provided on the top of the hot plate 2.

The conventional baking apparatus is constructed as described above, in which a semiconductor wafer 3 coated with a resist solution is placed on a hot plate 2, and the solvent in the resist solution is evaporated by heating the semiconductor wafer 3. Especially in the post-bake after development, as shown in FIG.
℃, the stress per unit area of the resist film increases due to shrinkage, and at the same time, the amount of side etching (indicated by black circles in the figure) increases when wet etching is performed. On the other hand, in order to remove the remaining solvent, the amount of remaining solvent (indicated by a white circle in the figure) must be 1 or less (relative value).
It is necessary to raise the temperature to 150°C or higher. Note that the above wet etching is performed on Si using buffered hydrofluoric acid.
O2 etching was performed. Therefore, removing the residual solvent and reducing the amount of side etching during wet etching by reducing the stress are not compatible.

[0005]

[Problems to be Solved by the Invention] In the vacuum baking apparatus as described above, during baking after resist pattern formation in the photolithography process, as shown in FIG. 3, as the baking temperature increases, stress in the resist decreases. The amount of side etching increases when wet etching is performed. In other words, the adhesion between the resist film and the semiconductor substrate decreases. Further, if there is a large amount of residual solvent in the resist film after baking, there is a problem in that during the next step of dry etching, the resist film will reflow, resulting in tilted edges and receding of the resist film. Another problem is that if the baking temperature is high, low-molecular-weight substances with low sublimation points in the resist film sublimate, causing the generation of foreign matter.

The present invention was made to solve these problems, and by reducing the pressure during baking, the solvent in the resist film can be efficiently evaporated, and the baking temperature can also be lowered than before. An object of the present invention is to provide a reduced pressure or vacuum baking apparatus and a baking treatment method that can suppress stress generated in a resist pattern and improve the heat resistance of the resist.

[0007]

Means for Solving the Problems A depressurization or vacuum baking apparatus according to claim 1 of the present invention is provided with an exhaust means for depressurizing or vacuuming a semiconductor wafer in a heated state. Further, in the baking method according to claim 2 of the present invention, the semiconductor wafer is heated to a predetermined temperature, and the temperature is increased from normal pressure to 10T.
The baking process is carried out by reducing the pressure to a pressure range of orr.

[0008]

[Function] In this invention, by reducing the pressure during baking, the solvent in the resist solution or resist film can be efficiently evaporated, and the baking temperature can be lowered than before, so that the resist pattern This stress can be reduced. Thereby, the adhesion between the resist film and the semiconductor substrate can be improved, and the heat resistance of the resist pattern can also be improved. Furthermore, generation of sublimate during baking can also be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic sectional view showing a reduced pressure or vacuum baking apparatus according to an embodiment of the present invention. Note that in each figure, the same reference numerals indicate the same or equivalent parts. In the figure, a hot plate 2 is provided as a heating means on a support stand 1, and a semiconductor wafer 3 is placed on this hot plate 2. A resist solution is applied to this semiconductor wafer 3 in a lithography process in photolithography, and a resist film is formed by patterning by exposure and development. An oven cover 4 is provided above the hot plate 2 to airtightly cover the semiconductor wafer 3. The pressure inside the airtight oven cover 4 is reduced to a pressure in the range from normal pressure to 10 Torr by an evacuation means, such as a vacuum pump 5.

In the reduced pressure or vacuum baking apparatus configured as described above, after the semiconductor wafer 3 is placed on the hot plate 2, the hot plate 2 is hermetically covered with the oven cover 4. Next, a baking process is performed while the inside of the airtight oven cover 4 is reduced in pressure from normal pressure to 10 Torr. As a result, the solvent in the resist film is evaporated and the resist film is cured. Therefore, the solvent of the resist film can be removed efficiently, and
Since the baking temperature can be lowered than before, the adhesion between the resist film and the semiconductor substrate can be improved. Further, since it is possible to prevent a decrease in the heat resistance of the resist film due to the influence of residual solvent in the resist film, reflow can be prevented and more precise etching can be performed. Furthermore, generation of sublimated substances in the resist film can also be reduced. Note that the level of pressure that should be reduced depends on the type of resist film (organic film) and organic solvent. In the above pressure range, for example, a novolac resin-naphthoquinone diazide (positive type) organic film, ethyl cellosolve acetate as an organic solvent, etc. can be effectively removed.

In the above embodiment, the semiconductor wafer 3 is placed on the hot plate 2, but the semiconductor wafer 3 may be placed in a post-bake oven to evaporate the solvent and harden the resist film. , the same effect as described above is achieved.

0012

Effects of the Invention As explained above, the present invention is provided with an evacuation means that reduces the pressure or evacuates the semiconductor wafer in a heated state, and performs the baking process by reducing the pressure from normal pressure to 10 Torr. As the solvent can be removed efficiently and the baking temperature can be lowered than before, the adhesion between the resist film and the semiconductor substrate can be improved, and the heat resistance of the resist film due to the influence of residual solvent in the resist film can be improved. It is possible to prevent the decline, and furthermore,
This has the effect of reducing the generation of sublimates in the resist film.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a reduced pressure or vacuum baking device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a conventional reduced pressure or vacuum baking device.

FIG. 3 is a diagram showing the relationship between various properties of a resist film and bake temperature.

[Explanation of symbols]

1 Support stand 2 Hot plate 3 Semiconductor wafer 4 Oven cover 5 Vacuum pump

Claims (2)

[Claims] Claim 1: A heating means for heating a semiconductor wafer;
A depressurization or vacuum baking apparatus comprising an evacuation means for depressurizing or evacuating the semiconductor wafer in a heated state. 2. A baking process, which comprises heating a semiconductor wafer to a predetermined temperature and reducing the pressure around the semiconductor wafer from normal pressure to 10 Torr.