JPH09211849A - Resist material and pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease halation without causing deterioration in the resist shape or in the depth of focus by using such an effect that the transmittance of the resist comprising a base polymer and a photosensitive agent decreases by exposure. SOLUTION: This resist for photolithograph is composed of a base polymer and a photosensitive agent and has a function to decrease its transmittance by exposure. To give the function to decrease the transmittance by exposure, it is preferable to add at least one photo-coloring agent selected from spiropyran compds., azobenzene and fulgides which have property to decrease the transmittance by exposure. The decomposition rate of the photocoloring agent by exposure is preferably proportional to the intensity of light and the density of the photocoloring agent itself. After the resist material is applied on a substrate 1 having high reflectance, the resist is exposed and developed to form a resist pattern 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoresist material and a method of using the same, and more particularly, to a photoresist material used as an etching mask, an ion implantation mask or the like on a substrate to be processed such as a semiconductor substrate and the like. The present invention relates to a pattern forming method.

[0002]

2. Description of the Related Art In a conventional resist pattern forming method,
Apply a resist layer on the substrate and g-line (wavelength 436n
m), i-line (wavelength 365 nm) or KrF excimer laser (wavelength 248 nm) is used for exposure, and a method of developing with an alkaline aqueous solution has been used.

In such a conventional method, deterioration of the resist shape due to light reflected from the underlying substrate, which is called halation, is a serious problem. This problem causes problems such as variations in transistor characteristics or disconnection when manufacturing a semiconductor element.

As a method for solving such a problem, Solid State Technology (Japan Version), 1993.
Method using an antireflection film under the resist as described in November 23, Nos. 23 to 25, or a dye as described in Semiconductor World, July 1993, pages 34 to 41. A method of using a mixed resist can be mentioned. The former method using an antireflection film has a high effect of suppressing halation, but the process is complicated, resulting in an increase in cost and an increase in particles. On the other hand, the method using the dye-containing resist is
Since it is a normal resist process, there are no problems such as cost and particle increase, but since there is a trade-off relationship between suppression of halation and depth of focus, the effect of suppressing halation becomes smaller when trying to secure the required depth of focus. I will end up.

[0005]

The first problem is that, as described above, in the resist containing the dye, when the amount of the dye is increased and the resist transmittance is decreased in order to further suppress the halation, the resist shape deterioration and This means that the depth of focus will decrease. The reason is that lowering the resist transmittance causes a difference in light intensity between the resist bottom and the resist surface.

An object of the present invention is to reduce halation without causing deterioration of resist shape and reduction of depth of focus. Another object of the present invention is to solve the above-mentioned problems and to achieve high integration of bun formation and improve its productivity.

[0007]

The inventor of the present application has made earnest studies to solve the above problems and arrived at the present invention. That is, the present invention is to provide a resist material for photolithography comprising a base polymer and a photosensitizer, which has a function of lowering the transmittance upon exposure.

The present invention also provides the above-mentioned resist material, characterized in that a photocoloring agent having a property of decreasing the transmittance due to the exposure is added in order to impart the function of decreasing the transmittance upon the exposure. Is.

The present invention also provides the above resist material, wherein the decomposition reaction rate of the photocoloring agent upon exposure is proportional to the light intensity and the concentration of the photocoloring agent itself.

The present invention also provides the above resist material, wherein the photocoloring agent is at least one selected from spiropyran compounds, azobenzene and fulgide.

Further, the present invention relates to a method for forming a pattern on a substrate having a high reflectance, which comprises applying the resist material described above on the substrate and then exposing and developing the resist material to form a resist pattern. It is to provide a pattern forming method characterized by the above.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The base polymer used as a component of the resist material in the method of the present invention is a known base polymer which can be usually used as a base polymer of a resist material. For example, a novolac resin is used as a base polymer for g rays and an i ray, and a polyvinylphenol resin is used as a KrF excimer laser.

As the photosensitizer that can be used in the method of the present invention, known photosensitizers that are usually used can be used, and for g or i rays, a naphthoquinone type photosensitizer can be used. Since the sulfonic acid ester is converted into an acid, it becomes soluble in an alkaline aqueous solution which is a developing solution. As the naphthoquinone-based photosensitizer, o-diazonaphthoquinone-5-sulfonic acid ester is preferably used.

The resist material of the present invention is required to have a function of decreasing the transmittance upon exposure, and the photocoloring agent is particularly preferably one which can impart the function of decreasing the transmittance upon exposure. Although not limited, the preferred method of imparting the function of decreasing the transmittance upon exposure in the method of the present invention is a method of adding a photocoloring agent having the property of decreasing the transmittance upon exposure to the resist material.

In some cases, the photosensitizer also serves as the one having the function of the above-mentioned coloring agent, but in this case, the optimum concentration for the role of the photosensitizer and the optimum concentration for the role of the photo coloring may be different. Since it is high, it is more preferable to add the photosensitizer and the coloring agent separately because the optimum concentration can be freely adjusted depending on the purpose.

The photocoloring agent used in the method of the present invention is not particularly limited as long as it can impart the function of decreasing the transmittance upon exposure as described above, and examples thereof include spiropyran compounds, azobenzene and fulgide. However, the present invention is not limited to this.

The addition amount of the photo-coloring agent varies depending on the material, but those skilled in the art can apply it in a pattern forming method of forming a resist pattern by applying a resist material on a substrate and then performing exposure and development. A person skilled in the art can easily determine the purpose of the present invention by appropriately selecting it.

The photocoloring agent causes a change in transmittance upon exposure, and the amount of change preferably depends on the amount of exposure. Therefore, where the light intensity is high, the decrease in the transmittance is large, and conversely, where the light intensity is low, the decrease in the transmittance is small. Halation is caused by the light incident on the step portion being reflected obliquely at the step portion as shown in FIG. Here, when comparing the light intensity of the step portion and the light intensity of the pattern end portion, as shown in FIG. 2, the step portion becomes larger. Therefore, when exposure is performed using a resist containing a photo-coloring agent, as shown in FIG. 3, the transmittance at the end of the pattern is maintained at a high level with almost no decrease, whereas the transmittance at the step is reduced. The rate will be low. Therefore, the light reflected by the step portion is easily absorbed, the halation is reduced, and the transmittance at the pattern end portion is kept high, so that the shape of the resist and the depth of focus are not lowered.

On a high-reflectance substrate, the reflected light becomes strong, so that the halation becomes large. Therefore, the photo coloring characteristic is effective. In the method of the present invention, the light reflectance substrate means a substrate having a reflectance of KrF excimer laser light (wavelength 248 nm) of 50% or more.

Regarding the effects of the present invention, the simulation results using a model will be described below.

FIG. 4 shows the result of calculation of the resist shape on the step by simulation, assuming that the decomposition reaction rate of the photocoloring agent upon exposure is proportional to the light intensity and the concentration of the photocoloring agent. Exposure is Kr
The F-excimer laser beam and the substrate are assumed to be polysilicon. Further, the transmittance of the resist containing the photo coloring agent was gradually changed from 70% / μm to 10% / μm by exposure. For comparison, a resist whose transmittance does not change by exposure (transmittance 30% / μ
The resist shape of m) is also shown in FIG. Although these two resists have the same performance (depth of focus, resist side wall angle) on a step-free substrate, the resist having a photo coloring agent is more prone to shape deterioration due to halation. It got smaller. This can be explained as follows.

First, the spatial light intensity of the exposure light transmitted through the mask formed on the resist is higher in the step portion than in the pattern end portion as shown in FIG. Therefore, the transmittance distribution in the resist is as follows when the exposure amount is 1/3.
As shown in FIG. 6, the transmittance at the step portion is lower than the transmittance near the mask edge. Therefore, the light at the step portion is absorbed by the resist and the halation is reduced.
Further, since the decrease in the transmittance at the pattern end portion is small, a good resist shape can be obtained.

The results of the simulation have been described on the assumption that the decomposition reaction rate of the photocoloring agent upon exposure is proportional to the light intensity and the concentration of the photocoloring agent. It is possible in principle if the transmittance decreases due to the above, and the decrease in the transmittance increases with an increase in the exposure amount. In particular, it is not necessary to include the above photo coloring agent. Absent. For example, the object of the present invention can be achieved even if the photosensitizer has the properties of a photocoloring agent.

[0024]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 A tungsten silicide substrate was used, and a nopolak resin as a base resin and o-diazonaphthoquinone-5-sulfonic acid ester as a photosensitizer were used in an amount of 8 wt.
%, And a benzothiopyran spiropyran (Chemical formula 1) having the following structural formula as a photo-coloring agent is used, for example, using a resist material containing 10 wt% with respect to the resin, and then applied on a tungsten silicide substrate having a step, Exposure with a g-line exposure machine is performed and development is performed with a 2.38% tetramethylammonium hydroxide developer. The resist pattern obtained by the above method is
As shown in FIG. 8, a good pattern with less deterioration of the resist shape was formed. The pattern shape formed similarly using the conventional resist can suppress the halation as compared with the pattern shape shown in FIG.

[0026]

Embedded image FIG. 6 is an explanatory view showing the transmittance distribution in the resist in the present embodiment. The dark black portion shows the portion where the resist transmittance is low in the order of concentration. FIG. 7 shows a schematic diagram showing the distribution of numerical values of the transmittance based on the actual measured values of FIG.

Example 2 As a base resin, a copolymer of poly (pt-ptoxycarponylmethoxystyrene) and poly (4-hydroxystyrene), and as a photosensitizer, triphenylsulfonium antimonate as an acid generator was used as a resin. For example, 5
% by weight, and an azo benzene (Chemical Formula 2) having the following structural formula as a photo coloring agent is added to the resin, for example, 1
Using a resist material containing 0 wt%, a resist pattern was prepared in the same manner as in Example 1, and a good pattern similar to that in Example 1 with little deterioration of the resist shape was formed.

[0028]

Embedded image Example 3 Poly (pt-Putyl Acrylate) as Pace Resin
And a copolymer of poly (4-hydroxystyrene),
An acid generator N-camphor sulfonyloxynaphthamide as a photosensitizer is contained in the resin in an amount of, for example, 3 wt%, and a photocoloring agent, fulgide (Chemical Formula 3) having the following structural formula is included in the resin in an amount of, for example, 8 wt%. Using a resist material, a resist pattern was produced in the same manner as in Example 1, and a good pattern similar to that in Example 1 with little deterioration of the resist shape was formed.

[0029]

Embedded image The resist material shown in Example 1 is applied on a stepped tungsten silicide substrate, exposed by a g-line exposure machine, and developed with a 2.38% tetramethylammonium hydroxide developer. As shown in FIG. 8, the resist pattern obtained by the above method is a good pattern with little deterioration of the resist shape. The pattern shape formed similarly using the conventional resist can suppress the halation as compared with the pattern shape shown in FIG.

Although the embodiments have been described above, various other modifications can be made in the present invention. In the embodiments, benzothiopyran spiropyran, azobenzene and fulgide were used as the photocoloring agent. The same effect can be obtained as long as the material has a transmittance reduced by exposure. Further, in each of the examples, the exposure was performed using the g-line exposure device, but depending on the photo coloring material, the same effect can be obtained by exposure with i-line or KrF and ArF excimer laser. Further, in FIG. 4, the case where the transmittance change before and after the exposure is 60% / μm is simulated, but if it is smaller than this, the same effect can be obtained. Although the tungsten silicide substrate is used as the substrate in the first embodiment, it can be applied to various substrates such as an aluminum substrate and a polysilicon substrate.

[0031]

As described above, according to the present invention,
Deterioration of the resist shape due to halation can be prevented without degrading basic performance such as resolution and depth of focus. Therefore, in forming a fine resist pattern, it is possible to reduce the dimensional variation and increase the process margin.

[Brief description of drawings]

1] Illustration of halation

FIG. 2 is an explanatory diagram showing a light intensity distribution on a resist.

FIG. 3 is an explanatory view showing a transmittance distribution of a resist containing a photo coloring agent.

FIG. 4 is an explanatory view showing a resist shape by simulation.

FIG. 5 is an explanatory diagram showing a light intensity distribution on a resist in KrF excimer laser exposure (NA = 0.5) and a 0.25 μm line pattern in Example 1.

FIG. 6 is an explanatory diagram showing a transmittance distribution in a resist in Example 1.

7 is a schematic diagram showing the transmittance distribution of FIG. 6 in a numerical range.

FIG. 8 is an explanatory diagram of a resist pattern obtained in Example 1.

FIG. 9 is an explanatory diagram of a resist pattern obtained in a conventional example.

[Explanation of symbols]

 1 Substrate 2 Resist 3 Exposure Light 4 Mask 5 Light Intensity 6 Low Transmittance Part 7 High Transmittance Part 8 Polysilicon Substrate 9 Resist Pattern Containing Photo-Coloring Agent 10 Conventional Resist Pattern 11 Light Intensity 12 Mask 13 Tungsten Silicide Substrate 14 Resist pattern 15 Resist pattern

Claims (7)

[Claims] 1. A resist material for photolithography comprising a base polymer and a photosensitizer, which has a function of lowering the transmittance upon exposure. 2. The resist material according to claim 1, wherein a photocoloring agent having the above property is added in order to impart a function of lowering the transmittance upon exposure. 3. The resist material according to claim 2, wherein the decomposition reaction rate of the photocoloring agent upon exposure is proportional to the light intensity and the concentration of the photocoloring agent itself. 4. The resist material according to claim 2, wherein the photocoloring agent is a spiropyran compound. 5. The resist material according to claim 2, wherein the photo coloring agent is azobenzene. 6. The resist material according to claim 2, wherein the photo coloring agent is fulgide. 7. A method for forming a pattern on a substrate having a high reflectance, wherein the pattern is formed on the substrate.
Alternatively, a pattern forming method comprising applying the resist material according to any one of 6 to 6 and then performing exposure and development to form a resist pattern.