JPS621793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method for coating a substance in which a solvent is dissolved, and in particular to an LSI pattern in which a photosensitive resin is spin-coated onto a semiconductor substrate to form a uniform coating film, and an LSI pattern is formed by photo-etching. The purpose is to improve the dimensional accuracy of.

Advances in LSI microfabrication are due to advances in lithography and advances in the development of exposure equipment and photosensitive materials.
It goes without saying that the resolution, dimensional accuracy, etc. of the fine pattern depend on the above, but they also greatly affect, for example, the uniformity of the coating state of the photosensitive material on the semiconductor substrate.

A conventional example of the coating method is shown.

Figure 1 shows a conventional general coating method in which a few drops of photosensitive resin 2 are dropped onto a semiconductor substrate 1 fixed to a spinner head 3 using a vacuum chuck method, and then a control system 4 is applied.
The coating is applied onto the semiconductor substrate 1. The coating film thickness can be controlled by the viscosity of the photosensitive resin, the rotation speed, etc., and the film thickness used in the normal process is 1 μm.
Before and after. With this method, when a photosensitive resin in which the solvent component in the photosensitive resin has a high evaporation rate is spin-coated, a radial striped pattern is generated from the center of the semiconductor substrate. Figure 2 shows the radial pattern 6 on the semiconductor substrate, and Figure 3 shows the developed pattern after applying AZ1350J photoresist to a thickness of about 1.35 μm in the normal state (Figure 1) using a mask. It is. Looking at the cross section a-b in FIG. 3, photoresist remains in portions corresponding to the ridges of the radiation stripes, resulting in poor patterning.

In order to determine the degree of unevenness (level difference), scanning measurement is performed on the coated surface coated by the above method using a micro level difference measuring device, as shown in FIG. 4. The vertical axis shows the full scale of 2500 Å, and the horizontal axis shows the measurement location. Approximately 1.4
It can be seen that unevenness of about 1000 Å occurs with respect to the average film thickness of μm. Note that the upward trend to the right comes from the measurement conditions and is unrelated to the evaluation content.

When a fine pattern is formed by photo-etching, if there is radial coating unevenness of the photosensitive resin as described above, the resist pattern after development will naturally have dimensional unevenness and its dimensional accuracy will deteriorate.

The areas corresponding to the ridges of the radial unevenness are underexposed because the photosensitive resin film is thick, and the size of the punched pattern becomes small when forming a punched pattern using a positive photosensitive resin.

The problem becomes even more serious when microfabrication is performed to a size of about 2 μm.

Figure 5 shows another conventional example, for example,
This method is also disclosed in Publication No. 10790. 1st
The difference from the figure is that the conventional example shown in Fig. 1 is surrounded by an enclosure 5, and a photosensitive resin solvent 21 is intentionally and forcibly fed into the enclosure 5, and spin coating is performed in that atmosphere. Although radial unevenness can be removed by this method, the coating film is formed with irregular color change shapes 7 (coating unevenness) remaining as shown in FIG. The reason for this is thought to be that the coating film is filled with the solvent component even at the end of spin coating, making it impossible to remove the solvent component uniformly, and that controlling the supply of the solvent is difficult. Furthermore, this method tends to result in a thin film, and there are also problems in managing the solvent, and there are many problems in terms of high costs for the equipment and coating process.

The present invention was invented in view of the drawbacks of the conventional examples as described above.

Examples of the present invention are shown in FIGS. 7, 8, and 9.

FIG. 7 is a basic diagram of the present invention, in which the spinner head 3
After dropping the photosensitive resin onto the semiconductor substrate 1 fixed above, the control system 4 performs a rotational coating motion to
In order to ensure that the vaporized solvent component in the photosensitive resin dropped onto the semiconductor substrate 1 is saturated on the semiconductor substrate, the control system 10 moves the closed space forming plate 11 onto the semiconductor substrate 1 while maintaining the gap 17. A closed space 21 is formed. Gap 17 is approximately 1cm
Before and after. Thereafter, the control system 4 starts the rotational movement to form a thin film of photosensitive resin on the semiconductor substrate 1.

FIG. 8 shows a specific example in which the control system 9 drops the photosensitive resin 2 onto the semiconductor substrate 1 from the tip of the nozzle 8, and then the control system 10 moves the closed space forming plate 11 onto the wafer. After that, the closed space 21 is formed, and then the control system 4 enters the spin coating process.
In this spin coating step, the exhaust control valve 16 is closed, and the solvent gas component generated in the spin coating step is closed in the system of the protective cover 12, the exhaust port 14, and the photosensitive resin storage box 15. After the spin coating process is completed, the exhaust control solenoid valve 16 is opened.
The entire spin coating process is centrally controlled by a control system 13.
In this case, the reason why the present invention is not carried out in a constantly evacuated state is because the "closed space effect" on the semiconductor substrate will be diminished. If the gap 17 of the closed space 21 is made very small, for example, 1 cm or less, there will be no problem even if the air is not exhausted.

Another embodiment is shown in FIG. In this case, what forms the closed space 21 is not the closed space forming plate 11, but something like the closed space forming cover 20,
In this case, something like the control 10 in FIG. 8 is unnecessary, and for example, the photosensitive resin coating nozzle 8 and the surfactant coating nozzle 18 (19 is the control system thereof) can be integrated with the closed space forming cover 20. . However, in this case, if the gap 17 is made extremely small (approximately 1 cm), the influence of the tips of the nozzles 8 and 18 will appear, and the area corresponding to the nozzle position will be coated in a small regular manner (that is, a film). (thickness may vary), so care must be taken.

In these embodiments, the closed space forming plate 11 and the closed space forming cover 20 suppress the divergence of vaporized solvent components on the semiconductor substrate 1 in the spin coating process, and
Any shape may be used as long as it can be set near the saturated vapor pressure.

In the conventional coating method, the surface condition of the coating film of photosensitive resin (especially quinonediazite type) is as shown in Figure 4, where unevenness occurs radially from the center of the semiconductor substrate.If you look at the pattern after exposure and development, you can see that Striped photosensitive resin residue (part of radial stripes) as shown in FIG. 3 is generated.

Furthermore, in the conventional spin coating method in which a solvent atmosphere is intentionally created, as shown in Japanese Patent Publication No. 46-10790, the radial striped pattern can be reduced, but the conventional method tends to result in a supersaturated atmosphere, as shown in Figure 6. Irregular film thickness unevenness occurs as shown in . In addition, there are many problems in practical use, such as the complexity of the equipment due to intentional supply, the high cost of solvents, and problems in pollution control.

When the closed space coating method of the present invention is used, the surface of the photosensitive resin is extremely flat as shown in Figure 10 (the scale etc. are the same as in Figure 4), and the pattern after exposure and development is as shown in Figure 11. Very good results were obtained, and the irregular film thickness unevenness unlike the conventional example in which solvent components were intentionally supplied did not occur, resulting in significantly better results.
The photoresist, exposure, development conditions, etc. are the same as in FIG. 4. FIG. 11 is a diagram showing patterning of the spin coating according to the present invention.

The present invention makes it possible to apply a very uniform thin film of photosensitive resin, which is essential for ultrafine processing, and also prevents dust from entering the semiconductor substrate from the external atmosphere during the spin coating process due to its structure. This invention can be said to be extremely useful for future VLSI technology.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the conventional coating method, Figure 2 shows the configuration of the conventional coating method.
The figure shows the pattern of the photosensitive resin on the semiconductor substrate when the same method is used, Figure 3 is a diagram of the developed pattern when the same method is used, and Figure 4 shows the state of the level difference when the same method is used. FIG. 5 is a diagram showing the configuration of another conventional coating method, FIG. 6 is a diagram showing the pattern of photosensitive resin on a semiconductor substrate when the same method is used, and FIG. FIG. 8 is a diagram showing the basic configuration of the coating method of one embodiment. FIG. 9 is a diagram showing the basic configuration of another embodiment of the present invention. FIG. 10 is a diagram showing the state of the level difference in the case of the method of the present invention, and FIG. 11 is a diagram of a developed pattern in the case of the method of the present invention. 1...Semiconductor substrate, 3...Spinner head, 1
1... Closed space forming plate, 20... Closed space forming cover, 21... Closed space.

Claims (1)

[Scope of Claims] 1. When a substance dissolved in a solvent is dropped onto the object to be coated and spin-coated, the vaporized solvent component in the dropped substance does not evaporate in the spin-coating process and becomes saturated vapor. A confined space region that maintains the pressure near the target object is provided above the coating surface of the object to be coated, and the solvent component present in the confined space region is formed by the solvent component dropped onto the object to be coated. A coating method characterized by: 2. The coating method according to claim 1, wherein the confined space region is formed by an enclosure that covers the surface to be coated of the object to be coated. 3. The coating method according to claim 1, wherein the substance dissolved in the solvent is a photosensitive resin.