JPH06283417A - Film-coating device - Google Patents

Abstract

PURPOSE:To make the film thickness uniform on the peripheral part of a semiconductor substrate. CONSTITUTION:A nozzle 8 is placed adjacent to the outer circumferential part of a substrate 4 which is set on a rotating part 6 for rotating the substrate 4. An excessive solution of precursor on the substrate 4 is removed by jetting a gas such as a nitrogen gas, etc., outwardly viewed from the center of the substrate 4 and spraying the gas over the outer circumferential part while the substrate 4 is rotated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for forming a functional thin film such as a ferroelectric thin film on a semiconductor substrate.

[0002]

2. Description of the Related Art A spin coating method is known as a method for forming a functional thin film. In this method, a precursor solution obtained by dissolving a metal compound, which is a precursor of a target functional thin film, in a solvent is rotated with an axis passing through the center of a semiconductor substrate (hereinafter simply referred to as “substrate”) as a rotation axis. After obtaining a precursor thin film having a uniform film thickness on the substrate by dropping it onto the substrate, the precursor film is heated to volatilize the organic functional groups of the solvent or the metal compound that is the precursor. Further, it is a method of crystallizing to form a target functional thin film.

The precursor solution applied on the substrate moves toward the outer peripheral portion of the substrate due to the centrifugal force generated by the rotation of the substrate. Only a thin precursor film remains on the substrate. Therefore, the precursor thin film having a desired film thickness is formed on the substrate, and the excess precursor solution is shaken off to the outside of the substrate.

The film thickness obtained by a single spin coating depends on the number of rotations of the substrate, the mucous membrane of the precursor solution, and the like. Therefore, in order to obtain a uniform and desired film thickness, it is necessary to properly select the type of precursor solution and the rotation speed of the substrate.

The precursor solution of the type used in the spin coating method must have such a viscosity that it is uniformly spread on the substrate by rotation and is wettable to the substrate.

If the viscosity is too high or the substrate has poor wettability, the precursor solution does not spread cleanly on the substrate, resulting in an uneven film. On the other hand, if the viscosity is too low, the film thickness of one coating film becomes too thin, and the coating must be applied many times.

[0007]

However, in this spin coating method, the excess precursor solution cannot be completely shaken off by the centrifugal force due to the rotation, and it accumulates on the outer peripheral portion of the substrate. Due to this excess precursor liquid, the precursor thin film 2 becomes thicker on the outer peripheral portion of the substrate 4 as shown in FIG. 1 (A), or wraps around to the back surface of the substrate 4 as shown in FIG. 1 (B). Such problems occur.

As a result, the semiconductor element using the functional thin film formed by the spin coating method cannot be used from the beginning in the vicinity of the outer peripheral portion of the substrate, or the desired characteristics due to the difference in film thickness. There is a problem such as not being able to obtain.

Further, other problems also occur. For example, when a normal photo-etching process is used, the distance between the mask and the precursor thin film becomes non-uniform, and the resolution of the pattern such as wiring is adversely affected when exposed.

Further, when it adheres to the back surface of the substrate, the smoothness of the back surface is also lost, which may cause defective fixing of the substrate due to so-called vacuum pressure bonding which is often used in a normal semiconductor process, and the substrate may be horizontally attached to the stage. Problems such as not being able to take off will also occur. It is an object of the present invention to solve the above problems and provide a coating film apparatus capable of forming a thin film formed on a semiconductor substrate with a uniform film thickness.

[0011]

In order to solve the above problems and to achieve the object, the present invention provides a rotating means for rotating a semiconductor substrate and a rotating means for rotating the semiconductor substrate by the rotating means. In a coating film apparatus having a film forming means for forming a precursor thin film by dropping a precursor solution of a functional thin film on the semiconductor substrate, the excess precursor solution existing on the semiconductor substrate is removed. The removal means is provided. As a result, the excess precursor solution existing on the semiconductor substrate is removed, and a thin film having a uniform film thickness is formed on the semiconductor substrate.

[0012]

EXAMPLE A first example of the coating apparatus according to the present invention will be described below with reference to FIG.

As shown in FIG. 2, a nozzle 8 for ejecting nitrogen gas is provided in the vicinity of the outer peripheral portion of the substrate 4 fixed to a rotating portion 6 of a coating device (hereinafter referred to as "spin coater"). The nozzle 8 is movable along the radial direction of the substrate 4 so that a substrate having a size different from the substrate 4 on which a thin film is normally formed can be handled.

Nitrogen gas is ejected from the nozzle 8 in a direction away from the rotation center 10 of the substrate 4, and the substrate 4
It is jetted slightly downward from the plane parallel to the plane of rotation of. The gas ejected from the nozzle 8 is used for the rotating substrate 4
Excessive precursor solution is blown out of the substrate 4 by hitting the outer peripheral portion of the substrate. This prevents excess precursor liquid from accumulating on the outer peripheral portion of the substrate 4, and consequently prevents the film thickness from increasing on the outer peripheral portion of the substrate 4.

At this time, if the gas ejection angle with respect to the rotating surface of the substrate 4 is too deep, the rotation of the substrate is disturbed, and if the angle is too shallow, excess precursor solution can be efficiently blown off. It will be difficult. Therefore, the incident angle of the gas and the amount of ejected gas must be adjusted so that the gas is ejected at an appropriate angle and the surplus precursor solution is blown off. The gas incident angle and the gas ejection amount depend on the viscosity of the precursor solution, the rotation speed of the substrate 4, and the like, and thus are determined according to the viscosity and the rotation speed. Further, another nozzle may be provided on the back surface side of the substrate 4 in order to prevent an excessive precursor solution from flowing around to the back surface. Next, a second embodiment will be described with reference to FIG.

As shown in FIG. 3, a nozzle 12 for dropping the solvent of the precursor solution is provided near the outer periphery of the substrate 4 placed on the substrate rotating unit 6 of the spin coater. This nozzle 1
2 is installed movably in the radial direction of the substrate 4 so that substrates 4 of different sizes can be handled.

From the nozzle 12, the solvent of the precursor solution is dropped on the substrate 4. For example, in a system in which a precursor such as metal methoxyethoxide is dissolved in a solvent such as methoxyethanol, this methoxyethanol is dropped from the nozzle 12. As a result, the concentration of the precursor thin film applied on the substrate 4 is locally reduced near the outer peripheral portion of the substrate 4. As a result, after the solvent is dried, excess precursor does not accumulate on the outer peripheral portion, and as a result, it is possible to prevent the outer peripheral portion of the final functional thin film from becoming thick. The amount of the solvent dropped in this example is adjusted depending on the type and concentration of the precursor solution, the rotation speed of the substrate 4, and the like. Next, a third embodiment is shown in FIG.
Will be explained.

As shown in FIG. 4, a spatula 14 is provided so as to contact the outer peripheral portion of the rotating substrate 4. The spatula 14 is installed movably in the radial direction of the substrate 4 so that substrates 4 of different sizes can be handled. With this spatula 14,
Excessive precursor solution collected on the outer peripheral portion of the substrate 4 during the rotation is removed. Thus, the excess precursor solution does not accumulate on the outer peripheral portion of the substrate 4, and as a result, the film thickness is prevented from becoming thicker on the outer peripheral portion of the substrate 4.

The spatula 14 is made of a soft material such as silicone rubber and resistant to chemicals so that it does not damage the substrate 4 and does not adversely affect the characteristics of the functional thin film by melting the material of the spatula 14. It is composed of good materials. The spatula 14 does not damage the substrate 4 and does not remove the precursor solution more than necessary.
The contact pressure on the substrate 4, the contact area, etc. are adjusted. The same effect can be obtained by replacing the spatula 14 with a sponge-like member that absorbs the precursor solution. Next, a fourth embodiment will be described with reference to FIG.

As shown in FIG. 5, a heating device 16 capable of uniformly heating the entire surface of the substrate 4 placed on the rotating portion 6 of the spin coater is provided. The heating device 16 is provided so as to uniformly heat even the largest substrate that can be used in the spin coater. The heating device 16 can heat to a temperature at which the solvent of the precursor solution and the organic functional group of the metal compound of the precursor are volatilized, about 300 ° C.

The substrate 4 is placed on the rotating portion 6 of the spin coater, the precursor solution is dropped, and the substrate 4 is rotated. After that, the substrate 4 is rotated until the film thickness reaches a target thickness, and then the substrate 4 is heated by the heating device 16 while being rotated to volatilize and remove the solvent and the like. The heating temperature is determined according to the type and number of solvents. Generally, a temperature slightly higher than the boiling point of the solvent is set. When there are two or more kinds of solvents, heating is performed a plurality of times from the low temperature side. Next, a fifth embodiment will be described with reference to FIG.

As shown in FIG. 6, a humidifying device 18 capable of uniformly humidifying is provided on the entire surface of the substrate 4 placed on the rotating portion 6 of the spin coater. The humidifying device 18 has the ability to evenly humidify the largest substrate that can be used in the spin coater. The humidifier 18 can uniformly generate water vapor so that the precursor film is not locally hydrolyzed.

The substrate 4 is placed on the rotating part 6 of the spin coater, the precursor solution is dropped and the substrate 4 is rotated. The precursor, which is the medium of the precursor solution used in this example, contains a metal alkoxide as at least one component. After the substrate 4 is rotated, the substrate 4 is rotated until a desired film thickness is obtained. Then, while rotating, water vapor is generated by a humidifier to hydrolyze the precursor thin film and gel it.
Then, the precursor film is heated to remove the solvent and the like, dried, and sintered.

[0024]

By using the apparatus of the present invention, it is possible to obtain a functional thin film having a uniform film thickness on the substrate 4 and its peripheral portion after spin coating.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a semiconductor substrate showing a state of thin film formation in a conventional coating apparatus, FIG. 1A is a diagram showing a state in which a surplus precursor solution is accumulated on an outer peripheral portion of the semiconductor substrate; (B) is a diagram showing a state in which the excess precursor solution is flowing around the back surface of the outer peripheral portion of the semiconductor substrate, and (C) is a state in which the excess precursor solution is present outside the outer peripheral edge of the semiconductor substrate. FIG.

FIG. 2 is a perspective view showing a first embodiment of a coating apparatus according to the present invention.

FIG. 3 is a perspective view showing a second embodiment.

FIG. 4 is a perspective view showing a third embodiment.

FIG. 5 is a perspective view showing a fourth embodiment.

FIG. 6 is a perspective view showing a fifth embodiment.

[Explanation of symbols]

2 ... Precursor thin film, 4 ... Substrate, 6 ... Rotating part, 8 ... (For nitrogen gas) nozzle, 10 ... Rotation center, 12 ... (For solvent dropping)
Nozzle, 14 ... Spatula, 16 ... Heating device, 18 ... Humidifying device.

Claims (1)

[Claims] 1. A rotating means for rotating a semiconductor substrate, and a precursor solution of a functional thin film is dropped on the semiconductor substrate while the semiconductor substrate is being rotated by the rotating means to form a precursor thin film. A coating film apparatus provided with a film forming means for forming a film, characterized in that a removing means for removing an excessive precursor solution existing on the semiconductor substrate is provided.