JPH046086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a resist coating method suitable for manufacturing semiconductor devices.

[Technical background of the invention and its problems] Generally, to form circuits for various electronic parts, etc., a resist as a photosensitive agent is applied, exposed to light, and developed to form an electric circuit in a desired pattern. It is. To explain this using an example of manufacturing a semiconductor device, in FIG. 1, a rotating vacuum chuck 2 is provided in a chamber 1, and a disc-shaped vacuum chuck 2 with a coating surface 3 on its upper surface is installed. A wafer 4 is held by suction. After dropping an appropriate amount of resist 5 onto the center of rotation, the wafer 4
is rotated to spread the resist 5 and form a resist film 6 on its surface. As shown in Fig. 2, the change in rotation speed over time _is as follows:
It is rotated at a low speed R ₁ (for example, about 500 rpm for a wafer 4 with a diameter of 3 inches) for up to 2 seconds, and spread on the surface 3 to be coated. Then, to obtain the desired thickness, t ₃
Constant rotational speed R ₂ depending on the film thickness up to seconds (e.g. 4000r.
pm) to form a resist film 6 of a predetermined thickness on the surface 3 to be coated. The relationship between the film thickness h of the resist film 6 and the rotation time t in the above case is as shown by curve A in FIG. 3 when the rotation speed is kept constant. That is, the film thickness decreases with time after the resist is dropped, and remains stable after reaching a predetermined rotation speed. Therefore, usually the time required to reach a constant film thickness
The wafer 4 is rotated by t ₃ to form a resist film with a constant thickness.

However, it takes time for the film thickness to become constant, and during that time, the resist 5 continues to be scattered from the surroundings while being supplied from the center of the coated surface 3 to the entire surface of the coated surface 3, and gradually becomes stable. The solvent contained in the resist 5 evaporates fairly quickly, and during the time it spreads from the center to the periphery, a considerable amount of the solvent is lost and the properties of the resist 5 change. Therefore, local variations in film thickness occur radially. Such changes in local film thickness make it impossible to miniaturize patterns or manufacture semiconductor products that require constant characteristics in adjacent areas, so an immediate solution has been desired.

[Object of the Invention] The present invention was made to eliminate the above-mentioned disadvantages, and an object of the present invention is to provide a method for applying a resist to a substantially uniform thickness over the entire surface to be coated.

[Summary of the Invention] The present invention provides a resist coating method characterized in that the surface to be coated is rotated at a rotation speed higher than a predetermined rotation speed corresponding to a desired film thickness, and then rotated at the above-mentioned predetermined rotation speed. , is a resist coating method that uses a high rotational speed to spread the resist quickly and prevents unevenness due to solvent evaporation.

[Embodiments of the Invention] Details of the present invention will be explained by each embodiment with reference to the drawings.

A first embodiment will be described with reference to FIG. This diagram shows the rotation speed on the vertical axis and the elapsed time on the horizontal axis.The equipment used is the same as that described in the conventional example, and the same as in Figure 1 is used, and the object to be coated is a semiconductor wafer. be. After chucking the wafer 4 with the vacuum chuck 2, an appropriate amount of resist 5 is dropped.
Note that the specified rotation speed corresponding to the desired film thickness is
It is assumed to be 4000r・p・m. First, the surface to be coated 3 is rotated at a rotation speed lower than a predetermined rotation speed, for example, 500 r.p.m., until t ₁ ' seconds, and the resist 5 is spread over the entire surface. Thereafter, it is rotated at a rotation speed higher than a predetermined rotation speed, for example, 6500 r.p.m., until t ₂ ' seconds.
During this time, unnecessary resist 4 is discharged from the surface 3 of the wafer 4 in a short time. Thereafter, a predetermined rotational speed corresponding to a uniform desired film thickness, e.g. 4000 r.p.m.
The resist film 6 is rotated for t ₃ ' seconds to obtain the desired resist film 6.

What is shown in FIG. 5 is a diagram explaining the second embodiment, in which the rotation speed is slightly higher than the predetermined rotation speed R ₂ ″ for up to t ₁ ″ seconds, and the entire surface is quickly covered. Expand resist 5, then increase rotation speed
Rotate R ₃ ″ for t ₂ ″ seconds and quickly remove excess resist 5
After discharging, the resist film 6 is rotated at a predetermined rotational speed R ₂ ″ for t ₃ ″ seconds to obtain a desired resist film 6 .

What is shown in FIG. 6 is a diagram explaining the third embodiment, in which the first rotational speed is the highest at R ₁ and t ₁
Rotate up to seconds, then less rotation speed
Rotate at R ₂ until t ₂ seconds to remove excess resist 5, then reduce the rotation speed to the specified rotation speed.
Rotate at R ₂ until t ₃ seconds to obtain a resist film 6 of desired thickness.

[Effects of the Invention] As detailed above, the resist coating method of the present invention is configured such that, before rotating at a predetermined rotation speed, the resist is rotated at a higher speed to quickly remove and discharge excess resist. Therefore, the change in film thickness is the third
As shown by curve B in the figure, excess resist is rapidly discharged and a resist film of the desired thickness can be obtained in a short time, so there is far less negative impact from solvent evaporation, etc. In the striation test, which measures stripes in the shape of a stripe, it has been reduced by about half, making it possible to obtain a significantly better resist film and making it possible to miniaturize circuit patterns.
It has also become possible to manufacture semiconductor products that require consistent characteristics in adjacent parts. In addition, it has various effects such as shortening the resist coating time and improving productivity.

Note that although this embodiment describes the manufacture of a semiconductor device, the present invention is not limited thereto.

[Brief explanation of drawings]

FIG. 1 is an explanatory sectional view of a resist coating device used in the conventional example and each embodiment of the present invention, and FIG.
The figure is a diagram explaining the resist coating method in the conventional example, FIG. 3 is a diagram comparing the film thickness change between the conventional example and the embodiment of the present invention, and FIG. The diagram to be explained, Figure 5, is also the same as Figure 2.
FIG. 6 is a diagram illustrating the third embodiment. 3... Surface to be coated, 5... Resist, 6... Resist film.

Claims (1)

[Claims] 1. In a resist coating method in which a resist dropped at the center of a surface of a substrate is spread and coated on the surface of the substrate by rotating the substrate, after the rotation is started and the dropped resist is spread over the entire surface of the surface, A resist coating characterized in that, before switching to a predetermined rotation speed that uniformizes the entire surface to a desired film thickness, a step of rotating at a rotation speed that is faster than the predetermined rotation speed and that removes the resist from the coated surface is added. Method.