JPH01260304A - Method of measuring thickness of resist film - Google Patents

Abstract

PURPOSE:To measure the thickness of a resist film during coating, by comparing the intensity of the light incident on the resist film applied to the surface of an object to be coated with that of the reflected light being the light passed through the resist film and reflected from the interface of the resist film and the object to be coated. CONSTITUTION:When light 1 is incident on the surface of a liquid resist film 3 in an oblique direction, the incident light 1 is refracted from the surface of the resist film 3 to be incident to the interior of the resist film 3 and totally reflected from the boundary surface of the resist film 3 and an object 4 to be coated to again pass through the resist film 3 and refracted from the surface of the resist film 3 to become reflected light 2. Since there is a definite relation between the ratio of the intensity of the incident light 1 and that of the reflected light 2, the absorbability and concentration of the solute of the resist film and the length of the light passing route in the resist film, the thickness of the resist film at a drying time can be estimated by calculating the ratio of the intensity of the incident light 1 and that of the reflected light 2.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of the method for measuring the thickness of resist films applied to wafers, reticles, photomasks, etc., improvements to resist coating equipment that can be easily carried out have improved the thickness of each coated film. The purpose of this method is to provide a method for measuring resist film thickness that allows highly accurate control of the resist film thickness for each object. The strength of the light and
The thickness of the resist film being coated is measured by comparing the intensity of reflected light that passes through the resist film and is reflected by the resist film and the surface of the object to be coated.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and particularly to improvements in the ability and method for measuring the thickness of a resist film applied to a wafer, reticle, photomask, etc.

2. Description of the Related Art In the manufacturing process of semiconductor devices, a process of applying resist to the surface of an object to be coated, such as a wafer, reticle, or photomask, is performed at various locations.

In recent years, with the miniaturization of semiconductor device patterns, there has been a demand for highly accurate control of the thickness of resist films applied to wafers, reticles, photomasks, and the like.

In the conventional resist coating process, it is not possible to simultaneously measure the film thickness during resist application, so the film thickness of the applied resist is measured after the resist has dried, so the film thickness is controlled by the rotation speed of the chuck. This is done according to the regulations regarding time and time.

For this reason, the thickness of the resist coated on each wafer, reticle, photomask, etc. varies.

Under the above circumstances, there is a need for a resist film thickness measuring method that can measure the resist film thickness during resist coating and control the film thickness.

[Conventional technology]

The resist film thickness in the conventional resist coating process is controlled by specifying the rotation speed and time of the chuck of the resist coating device that carries the object to be coated, since it is not possible to measure the film thickness simultaneously during resist coating. ing.

The resist film thickness was measured after the resist was dried.

For this reason, it has become difficult to precisely control the thickness of a resist film applied to a wafer, reticle, photomask, etc., which is required as the patterns of semiconductor elements become finer.

[Problem to be solved by the invention]

In the conventional resist film thickness measurement method described above, it is not possible to simultaneously measure the resist film thickness during resist coating, and the measurement is performed based on the stipulations of the rotation speed and time of the chuck of the resist coating device that carries the object to be coated. , the resist film thickness was measured after the resist was dried. For this reason, there was a problem that variations occurred in the resist film thickness for each object to be coated.

The purpose of the present invention is to provide a resist film thickness measuring method that allows highly accurate control of resist film thickness for each object to be coated by improving a resist coating device that can be easily implemented under the above circumstances. That is.

[Means to solve the problem]

The problem mentioned above is that during the resist coating process, incident light is incident on the resist film coated on the surface of the object to be coated, and the intensity of this incident light and the amount of light that passes through the resist film and the object to be coated are This problem is solved by the resist film thickness measuring method according to the present invention, which measures the thickness of the resist film during coating by comparing the intensity of the reflected light reflected from the surface of the resist film.

[Effect]

That is, in the present invention, as shown in FIG.
When the incident light 1 is incident on the surface of the liquid resist film 3 from an oblique direction, the incident light 1 is refracted at the surface of the resist film 3 and enters the resist film 3, and is refracted at the interface between the resist film 3 and the object to be coated 4. The light is totally reflected, passes through the resist film 3 again, is refracted at the surface of the resist film 3, and becomes reflected light 2.

According to the Lambert-Bell law, the relationship between the intensity Io of the incident light 1 and the intensity I of the reflected light 2 is the absorption rate of the solute in the C resist.

Concentration of solute in C resist [unit 2M (molar concentration)]
.

If the thickness of the resist film is 1 (unit: Cl1), then e
cl I/l0=10.

Here, the concentration of the solute and the length of the light path in the resist change as the resist dries, but since the product of C and l is always constant, the intensity of the incident light 1 is . By determining the ratio between the intensity of the reflected light 2 and the intensity of the reflected light 2, the thickness of the resist film can be controlled.

Therefore, even when the solvent is still sufficiently contained, it is possible to control the resist film thickness so that the resist film has a desired thickness after drying.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

Figure 2 is a configuration diagram showing one embodiment of the present invention, and shows the chuck part of the resist coating device that mounts the object to be coated.

In the figure, the same parts as those shown in FIG. The chuck 5 rotates at high speed as shown in FIG. 6 is an infrared light emitting diode, and 7 is an infrared light receiving element.

The object 4 to be coated is mounted on the chuck 5, and the chuck 5 is rotated at high speed while dropping resist onto the surface of the object 4 to be coated. During high-speed rotation of the chuck 5, incident light l emitted from the infrared light emitting diode 6 is incident on the surface of the liquid resist film 3 from an oblique direction.

Then, the incident light 1 is refracted on the surface of the resist film 3, enters the resist film 3, is totally reflected at the interface between the resist film 3 and the object to be coated 4, passes through the resist film 3 again, and is exposed to the resist film 3. The light is refracted at the surface of the film 3 and becomes reflected light 2.

In order to measure the thickness of the resist film 3 based on the intensity of the incident light 1 and the reflected light 2, it is necessary to measure the thickness before the resist solvent evaporates.

In the present invention, the amount of solute per unit area is measured based on the light absorption rate of the solute dissolved in the solvent of the resist.

For this reason, the light used in the measurement method of the present invention must be selected at a wavelength that is easily absorbed by the solvent so as not to be affected by absorption by the solvent.

While comparing the intensity of the incident light 1 and the intensity of the reflected light 2, the chuck 5 is held until the resist film thickness reaches the desired thickness.
Continue to rotate to reduce the film thickness, and when the film thickness reaches the desired value, reduce the rotation and dry.

According to the Lambert-Bell law, during the resist coating process, the intensity of the incident light 1 incident on the resist film 3 and the difference between the intensity of the incident light 1 that passes through the resist film 3 and the resist film 3 and the object to be coated 4 are determined. There is a certain relationship between the ratio of the intensity of the reflected light 2 reflected at the interface, the absorption rate and concentration of the solute in the resist, and the length of the light path through the resist. The concentration of C and the length of the light path through the resist change as the resist dries, but since the product of C and l is always constant, it is possible to predict the film thickness when the resist dries. .

〔Effect of the invention〕

As is clear from the above description, according to the present invention, by adding simple improvements to the resist coating device, it is possible to measure the thickness of the resist film applied to the surface of the object to be coated during the coating process. Therefore, it is possible to eliminate variations in the thickness of the resist film between each object to be coated, and it is possible to eliminate subtle differences in the pattern during development of the resist film due to differences in resist film thickness in the manufacturing process of semiconductor 'AN'. It has the advantage that it can be eliminated and that it is possible to manufacture miniaturized semiconductor devices, and it is expected to have significant economical and reliability improvement effects, making it extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a configuration diagram showing an embodiment according to the present invention. In the figure, 1 is the incident light, 2 is reflected light, 3 is a resist film, 4 is the object to be coated, 5 is Chuck, 6 is an infrared light emitting diode, 7 is an infrared receiving element; shows.

Claims (1)

[Claims] During the resist coating process, incident light (1) is incident on the resist film (3) coated on the surface of the object to be coated (4), and the intensity of the incident light (1) and the inside of the resist film (3) are determined. The film thickness of the resist film (3) during coating is measured by comparing the intensity of the reflected light (2) that passes through the resist film (3) and is reflected on the surfaces of the resist film (3) and the object to be coated (4). A resist film thickness measuring method characterized by: