JPS59155926A - Forming method of pattern - Google Patents

Abstract

PURPOSE:To thicken the film thickness of a resist film applied, and to reduce the irregularities of a stepped difference section on a substrate by selectively photosensitizing a radiation sensitive resin film in multilayer structure having different developing rates, developing the resin film first by using a developer of high concentration and developing it by a developer of low concentration. CONSTITUTION:A thick positive type ultraviolet resist film 7 is applied onto a semiconductor substrate 1 on which an insulating film 2, the surface thereof has stepped difference section patterns 2a, is formed while burying patterns 2a. Ultraviolet beams 10 are irradiated to the whole surface to change the film 7 into a photosensitized film 7a, the film 7a is turned into a film 7b through heat treatment, a second resist film 8 of the same type as the film 7 is applied onto the film 7b, and the whole surface is exposed and thermally treated. A mask 9 with light shielding sections 9a consisting of Cr is superposed on films in isolated multilayer applying structure difficult to be mutually dissolved as mentioned above, ultraviolet rays are irradiated, one parts of the film 8a of an irradiating section and the film 7b under the film 8a are removed by using a developer in high concentration, and patterns consisting of the films 8 and 7b are left by employing a developer in low concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pattern forming method, particularly to a pattern forming method using a radiation-sensitive resin.

Conventional configurations and their problems High integration and high density of integrated circuits have increased due to advances in conventional phosphorography technology. The minimum line width has become around 1 μm, and in order to achieve this processed line width, there are three methods: ultraviolet exposure using a reduction projection method with a high aperture lens, electron beam exposure that draws directly on the substrate, One example is the gloximity exposure method using X-rays. However, with either method, it is difficult to simultaneously obtain good line width control, high resolution, and good coverage of stepped portions without chronically reducing throughput, that is, mass production. In particular, unevenness inevitably occurs on actual integrated circuits, and after applying radiation-sensitive resin (hereinafter referred to as resist), differences in the resist film thickness occur at the uneven parts, resulting in good lines. Width control becomes impossible.

This will be explained using FIG. FIG. 1 shows a state in which a single-layer resist film is applied to a stepped portion by a conventional method and patterned across the stepped portion. FIG. 1A is a sectional view of a state in which a film 2 such as a wiring q S 102 having a step 2a such as a wiring is formed on a substrate 1 such as a semiconductor substrate, and a resist 3 is applied thereon. In this case, when the film thickness of the resist 3 on the flat substrate 1 without the step 2 is applied to the thickness tR2, the thickness of the resist 3 on the step 2 is determined by the viscosity of the resist itself and the time of coating. The film thickness tR2 is determined by the number of rotations.

At this time, it is physically impossible to set tR1=tR2, that is, to eliminate the difference in the thickness of the resist film at the uneven portions. FIG. 1B shows a plan view of a resist pattern formed with a film thickness of tR1 to "R2" in this manner.

This means that if it is determined that the pattern width is increased at a position where the resist pattern 3 has a film thickness tR1 by intersecting the step pattern 2a at a right angle, then at a position where the film thickness tR2 is tR□>tR.
2, the pattern width is Q and a
l>a2, and a dimensional conversion difference occurs at the stepped portion, resulting in warpage. In the case of a very fine pattern, good line width control cannot be obtained, and furthermore, the edge portion 2b of the stepped material 2a is substantially thicker than the film thickness tR1 of the flat portion, resulting in a decrease in resolution. Generally, the resolution improves as the resist film thickness becomes thinner. This is because the incident energy is attenuated due to interference 9-diffraction development when fine gaps are created due to the wavelength of the radiation itself.

In other words, in order to reduce the difference in resist film thickness on the layered kimono,
Even if an attempt is made to reduce the apparent difference in resist film thickness by simply coating the resist thickly, the resolution deteriorates, which is not preferable in terms of pattern formation.

A three-layer structure resist method has been proposed in order to improve the resolution and dimensional conversion difference value on a step using such a conventional single-layer resist. This method will be explained using FIG. 2. A stepped portion 2 is formed on the substrate 1, an organic film such as a photoresist 4 is thickly coated (FIG. 2A), and an inorganic film layer 5 such as a plasma silicon oxide film is further formed on the organic film 4, and then the uppermost layer is formed. Apply a thin layer of resist 6 to (Figure 2B)
.

Next, the resist layer 6 is patterned with a resist pattern 6a.
(Figure 2C). An inorganic film layer pattern 5a is obtained using the dry etching technique through the resist pattern 6a (FIG. 2D).

Finally, an organic film pattern 4a is formed using oxygen-based gas plasma via the resist pattern 6a and the inorganic film layer 5a (FIG. 2E).

In pattern formation using this three-layer structure resist, the top layer resist 6 can be thinned, resulting in good resolution, and the bottom layer organic film layer 4 is coated thickly, so there is no effect of the step 2 on the substrate 1, and the resist layer < Since the turn-rotation a can be obtained, there is little difference in dimensional conversion. However, it is difficult to detect the end point of the dry etching technique and the etching conditions cover multiple layers, and the process time may be long, which is unfavorable in terms of mass production and economy. There is an inconvenience that the resist pattern 6a is removed when the pattern 4a is formed.

OBJECTS OF THE INVENTION Therefore, the present invention presents an obstacle to patterning a conventional single-layer resist on an actual integrated circuit having irregularities. It prevents the difference in pattern size conversion and the accompanying decrease in resolution, has sufficient thickness even if the film is reduced by dry etching, etc., and is economical as a pattern forming method using a three-layer resist. The object of the present invention is to provide a pattern forming method that overcomes drawbacks in mass production.

Structure of the Invention The present invention provides a single-layer resist film that is selectively exposed to light in order to reduce the difference in notch dimension conversion at step portions and to prevent a decrease in resolution while applying a thick resist film. In the case of a resist film with a multilayer structure having different development speeds, two or more types of developers with different concentrations are used, for example, first the development process is performed with a high concentration solution and a retaining solution, and then the second step is performed. attempts to provide a pattern forming method in which development is performed using a developer having a lower concentration than that in the first stage.

Through numerous experiments, the present inventors discovered that a single layer resist film or a second resist film laminated on a photosensitive first resist film was used.
The layer film is developed with a high-concentration developer in the first step, and then developed with a low-concentration developer in the second step to create a stable resist layer with a high P-to-total ratio (
I found that I could get a turn.

In the present invention, as a stable development method for obtaining a high P spectral ratio pattern, the first step is treatment with a high-concentration developer in order to quickly remove the photoreacted portion of the second resist on the first resist. Next, in order to develop and remove the first resist below the photosensitive area of the second resist, it is desirable to use a developer with a low degree of a. These 2
Due to the stepwise development process, the development speed of the unexposed part of the second resist is suppressed during the development of the first resist, resulting in a high P value.
A spectrum ratio pattern is obtained. In general, the method of the present invention can be applied to any radiation resist having a decomposition type and image response.

Description of Actual Gun Example A first actual gun example in which the present invention is applied to a single layer resist will be described. An explanation will be given using a positive resist as an example of an actual gun. Apply a positive resist such as AZ14 on a semiconductor substrate.
70 (manufactured by Shisoplay Co., Ltd.) to a thickness of 2 μm, and this resist was selectively exposed at 100 m I/aj.
It is applied with the energy of Next, as the first developer, MF
1 with a 1:1 dilution of 312 (manufactured by Shisopray) and water.
A development process was performed for 0 seconds, and after continuous development for 50 seconds with a 1:2 dilute solution of MF312 and water, a rinsing process was performed to remove the exposed areas by development. As mentioned above, after rapidly developing the photosensitive layer on the surface with two types of developers with different concentrations, that is, a developer with a higher concentration, it is developed with a developer with a lower concentration in order to prevent film deterioration in the unexposed areas. By 1
It was possible to form a line-and-space pattern with a high P spectral ratio of μm.

As a second practical example of the present invention, a case where the resist is used in a multilayer structure having different development speeds will be described in detail with reference to FIG. As an example, a positive type resist, particularly a positive type ultraviolet resist (hereinafter referred to as positive UV resist) will be explained as an example. A positive UV resist is applied to a semiconductor substrate or the like or a substrate 1 on which an insulating film is formed on the semiconductor substrate to a thickness greater than that of the step pattern 2a such as wiring, the surface is made flat, and soft baking is performed. Figure 3A-). Next, by irradiating the entire surface of the positive UV lettuce) 7 with UV light 10, the entire surface of the resist was exposed to the positive UV register', <
) 7a (Figure 3B). photosensitive positive register)
7a is heat treated with foil to form resist 7b (Fig. 3C)
)゛. This heat treatment is desirable but not necessary.

Next, a second positive UV resist 8 of the same type as the first layer of positive UV resist is applied onto the first positive UV resist 7b which has been exposed to light over the entire surface and subjected to heat treatment, and soft baking is performed. At this time, 1. If the resist 7b whose film quality has changed after heat treatment ktfifx is used, it will be a positive UV lettuce) 7
b and the second positive UV resist 8 are unlikely to dissolve each other and can form a separate multilayer coating structure (Fig. 3D).

Next, using a mask 9 having a pattern, ultraviolet light is selectively applied to areas other than the chrome cap 9a which is a light shielding part. Irradiate the second positive UV resist 8, 7b (Fig. 3 E)
. Then, the second positive UV resist 8a in the ultraviolet irradiation area and a part of the first positive UV resist b below it are developed with a high concentration developer, and finally the first positive UV resist 8a is developed with a developer with a low concentration.
(Positive UV lettuce) 7b'i developed and removed resist 8,
7b is formed (FIG. 3F).

Needless to say, in the above embodiment, only the second positive UV resist 8a may be developed with a high-concentration developer.

By obtaining a series of these steps, it is possible to form a fine pattern while applying a thick resist, and it is possible to reduce the difference in dimension conversion at the stepped portion.

Therefore, a more specific example will be explained using FIG. 3. A first resist 7 such as AZ1470 (manufactured by GGREY Co., Ltd.) is applied to a thickness of 2.4 μm on the step pattern 2a having a thickness of 1 μm formed on the substrate 1 (FIG. 3A). Next, UV light with all wavelengths in the ultraviolet region is applied to 150 m
The first resist 7a is irradiated with an exposure energy of J/crri to sufficiently cause a photosensitive reaction (FIG. 3B).
. Therefore, heat treatment 11 for 30 minutes at 90C is performed (C1
, the photosensitive reaction of the first resist 7b at this time is the heat treatment 11.
It will not deteriorate over time. Next, a second resist 8, for example AZ1470 (manufactured by Sickray Co., Ltd.) similar to the first resist 7, is applied to a thickness of 1.0 .mu.m, and soft baking is performed for 30 minutes. The film thickness at this time is 3.4
.mu.m, which is the sum of the film thicknesses of the first resist 8 and the second resist 8 (FIG. 3D).

Next, using the reduction projection exposure method, the first . The second resists 7b and 8 are selectively exposed to light to form an exposed area 8a (see FIG. 3E).Then, as a first stage development process, an alkaline developer (tetromethyl hydroxide ammonia type) is used. MF312 (
MF312 was developed in a 1:1 diluted solution (manufactured by Shipley) and water for 20 seconds, followed by continuous development as a second step.
After developing for 50 seconds with a 1:2 dilution of water and water, a rinsing process was performed. 2nd resin) 7b, 8b are simultaneously developed and removed (FIG. 3F). By performing the series of steps as described above, it was possible to form a pattern with a thickness of 3.4 μm and a learn-and-space pattern of 1 μm with a high P spectral ratio.

FIG. 4 shows the development rate for exposed and unexposed resists depending on the concentration of the developing solution in the pattern forming method of the present invention. According to this, photosensitive resist has 1:
The development rate of one high-concentration developer is 5008/sec,
With the low concentration developer of 1:2 liquid, the development rate is 125 people/second, which is about 3 times higher. , 1:2 liquid for 1.
The 1:1 solution has a higher development rate of 7 A/sec, which is 3 times higher.

This will be further explained using FIG. 5 to explain the developing mechanism in the pattern forming method according to the present invention. FIG. 5 shows the first step according to the method of the present invention. A hypothetical cross section of the resist is shown when the second resist is applied in two layers and then selectively exposed. Figure 5a
The second resist 8 is applied on the first resist 7b which has been subjected to full-surface exposure and heat treatment, and the second resist 8 is selectively exposed)
The 8th layer section is in an exposed state. 2 with the above 1:1 solution
Apply for 0 seconds. At this time, the second resist in the photosensitive area and a part of the first resist directly below are developed in the vertical direction at a rate of 500 people/second. On the other hand, the penetration of the unexposed second resist 8 in the lateral direction by development is determined by a development rate of 5 persons/second (FIG. 5b).

At this time, for example, the exposure area pattern t1 of the resist in FIG. 5A. 0 μm, the pattern width B after 20 seconds of development with the 1:1 solution in the first stage in Figure 5B
is slightly expanded to 1.01 μm. By the way, if you develop the first resist 7b with a 1:1 solution for 60 seconds until the end, 1.
03 μm. However, in reality, since the pattern widths A and J of the exposed area portion are exposed due to interference development, the pattern width after the above-mentioned development is further promoted and expanded. Next 1
: Develop the first resist b to the end at a development rate of 125 people/second by developing 5 layers with two liquids for seconds.

At this time, the pattern width C of the second unexposed resist area, i) N light area, is 1.02 μm, and the expansion from the initial dimension t is greater than the one-stage development using a 1:1 solution. It is also narrow (Fig. 5C). Furthermore, because of the difference in development rate, the 1:2 liquid requires less intrusion into the seventh resist 7b in the horizontal direction, and the initial dimension a can be faithfully reproduced.

Actual gun example of the present invention (see Fig. 3) and the result of Fig. 4 Pattern 3 (resin) 7 patterned on step pattern 2
b, 8) is as shown by the dotted line in FIG. 6 according to the conventional method, but when the pattern forming method according to the present invention is used, the dimensional change is reduced as shown by the solid line in FIG. 6.

In the example, 1. The film thickness conditions of the second resist are as follows:
It should be determined based on the level difference in the unevenness of the underlying substrate. Due to the nature of the present invention, the first and second resists may have different development speeds. Regarding the type of resist, it is clear that the present invention can be applied to any of X-rays, electron beams, ion beams, and deep ultraviolet rays. Furthermore, the first. It is convenient that the second resist has a different radiation reaction mechanism but can be developed with the same developer. Although the heat treatment temperature for curing differs for various resists, it is preferably 120C or lower at a temperature that does not eliminate the development reaction.

Effects of the Invention As described above, according to the present invention, by coating the resist thickly, it is possible to eliminate unevenness at the stepped portion, and in addition, it is possible to reduce the pattern width variation rate at the stepped portion, resulting in a decrease in resolution and sensitivity. I don't know. Furthermore, since the resist film is thick, dry etching resistance is improved. In addition, since no plasma treatment is required, pattern formation can be performed in-line, making it an excellent method for mass production and economy. Furthermore, the present invention has excellent dimensional controllability and stability, and will exhibit important value in the production of semiconductor integrated circuits for future miniaturization.

[Brief explanation of the drawing]

Fig. 1A is a cross-sectional view of step patterning using the conventional single-layer resist method, Fig. 1B is a plan view of Fig. 2A, and Fig. 2A-
E is a process cross-sectional view of the conventional three-layer resist method, Figure 3 A
1 to F are process diagrams of a pattern forming method according to an embodiment of the present invention, FIG. 4 is a development rate diagram using each developer, FIGS. FIG. 2 is a plan view of a pattern formed according to the present invention. 1...Substrate, 2...Step, 7...
... Positive resist, 7a... Photosensitive positive resist, 7b... Heat-treated photosensitive positive resist, 8... Positive resist, 9... Mask. Name of agent: Patent attorney Toshio Nakao and one other famous confectioner Figure 1 Figure 2? 2nd figure 2α? Yu? a Figure 3, Figure 3, Figure 4, Injury TI? j time (minutes) □ Figure 5 Figure 6? leather

Claims (1)

[Claims] (2) A pattern forming method characterized by sequentially developing a selectively exposed photosensitive resin film using two or more types of developing solutions with different degrees of a. A pattern forming method characterized by developing a radiation-sensitive resin film with a multilayer structure with a high development speed using two or more types of developers with different concentrations. (3) After developing with a developer with a high concentration, Claim 2, characterized in that the image is developed using a low-concentration developer.
The pattern forming method described in section.