JPH06140300A - Exposure method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an exposure method which enables high resolution exposure while maintaining the simplicity of the contact exposure method. [Structure] A phase shift type optical mask made of a fine figure-shaped dielectric provided on a substrate is arranged close to a photosensitive material film, and the phase shift type optical mask is irradiated with light to interfere with diffracted light. An exposure method that directly transfers a light-dark image of light to a photosensitive material film under the condition that 0th-order diffracted light does not appear in the light-dark image of light or is extremely small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for forming a pattern on a photosensitive resin material or a photosensitive material such as a silver salt photographic film used for manufacturing a semiconductor device such as an IC or an LSI, or a photosensitive material thereof. The present invention relates to an exposure method for evaluating the resolution of a conductive material.

[0002]

2. Description of the Related Art In order to increase the degree of integration and speed of semiconductor devices such as ICs and LSIs, it is necessary to miniaturize the internal structure of the semiconductor devices. Therefore, it is required that the photosensitive resist material used for microfabrication when manufacturing the internal structure also has high resolution ability.

The resolution evaluation of the resist material is usually carried out using an exposure apparatus used in the process of actually manufacturing a semiconductor device. However, such devices are very expensive and often cannot be used solely for resolution evaluation of resist materials. Therefore, if there is a simple method for evaluating the resolution of a resist material without using such an apparatus, that method becomes an extremely effective means for developing a new resist material.

Conventionally, the contact exposure method has been used as the simplest method for evaluating the resolution of a resist material. In this method, an optical mask with black and white fine patterns is brought into close contact with the resist coating film, the resist film is exposed through the mask in a pattern shape, and then it is observed how fine patterns can be transferred as a resist film image. Is to do. In addition, as a thing related to this method,
Masatoshi Utaka, Introduction to New LSI Engineering Published by Ohmsha, No. 14
There are pages 8 to 151 (March 1992).

[0005]

The above-mentioned prior art is a simple method as an evaluation means for observing the resolution of a resist material up to several micrometers. However, as a means to see the resolution of 1 micrometer or less,
It is not suitable because the adhesion between the mask and the resist film cannot be kept sufficiently high.

An object of the present invention is to provide an exposure method which enables high resolution exposure while maintaining the simplicity of contact exposure.

[0007]

In order to achieve the above object, the exposure method of the present invention uses a phase shift type optical mask formed of a fine figure-shaped dielectric material provided on a substrate and exposes it. It is a method of arranging in close proximity to the photosensitive material film, irradiating this phase shift type optical mask with light, and directly transferring a bright and dark image of light generated by interference of diffracted light to the photosensitive material film.

When this phase shift type optical mask is used, it is not necessary to bring the optical mask and the photosensitive material film into close contact with each other, and the so-called proximity exposure method enables exposure with sufficiently high resolution. The distance between the optical mask and the photosensitive material film is not theoretically limited, but in reality, since the incident light on the mask is not completely parallel light, it is preferably within 1 mm.

[0009]

The black-and-white optical figure mask that has been widely used for the resolution evaluation by contact exposure and an example of the optical figure mask used in the present invention are shown in comparison in the drawing.
The operation of the present invention will be described.

FIG. 1A is a cross-sectional view of a conventional black-and-white optical figure mask, and FIG. 1B is a bottom view thereof, in which a parallel stripe light-impermeable film 2 is formed on a transparent substrate 1. ing. Figure 1
1C is a cross-sectional view of a dielectric optical figure mask of an example of the present invention, and FIG. 1D is a bottom view thereof, in which parallel stripe dielectric films 3 are formed on a transparent substrate 1.

The two types of optical figure masks shown in FIG.
Both act as light diffraction gratings. At this time,
Among the light after passing through the optical figure mask shown in (a) and (b), there is light (0
The second diffracted light) is always included. However, as shown in FIG.
When light is incident on the optical figure mask shown in (d), such 0th-order diffracted light does not appear if a certain condition is satisfied. That is, in this optical figure mask, the thickness d of the dielectric film is between the wavelength λ of light and the refractive index n of the dielectric at that wavelength,

[0012]

[Equation 1]

In the above relationship, and when the light is vertically incident on the mask, the 0th-order diffracted light does not appear. This is because the phase of the light wave passing through the place where the dielectric exists is shifted (shifted) by half a wavelength with respect to the phase of the light wave passing the place where the dielectric does not exist. It is a phenomenon that occurs because two waves completely cancel each other. In addition,
As the optical figure mask of the present invention, it is preferable to use a mask in which the intensity of the 0th-order diffracted light is zero or smaller than the total intensity of the 1st-order diffracted light (preferably 50% or less).

FIG. 2 shows interference of diffracted light caused by light passing through the optical figure mask shown in FIGS. 1 (a) and 1 (b), and FIGS. 1 (c) and 1 (d). This is a model comparison with a state of interference of diffracted light caused by light passing through an optical figure mask. However,
In the latter case, it is assumed that the condition that 0th-order diffracted light does not appear is satisfied. In FIG. 2, the light and dark of light generated by the interference of a plurality of diffracted lights is represented by the light and dark of a moire pattern. FIG. 2A shows how the diffracted light interferes with the optical mask having the light opaque film. In this case, the light-dark image of light that closely follows the light-darkness of the mask is limited to the immediate vicinity of the mask.

On the other hand, FIG. 2B shows how the diffracted light interferes with the optical mask having the dielectric film. In this case, a light-dark image of light such that the position corresponding to the end face of each dielectric strip becomes a dark part is formed up to a position distant from the mask, and the repetition of the light-dark pattern is twice as large as that in the previous case. It has become. It is the exposure method of the present invention that this light and dark light image is used for exposing the photosensitive material. Therefore, the exposure method of the present invention can perform high-resolution exposure.

[0016]

EXAMPLE 1 An example of the present invention will be described below. First, the manufacturing process of the optical mask used in this embodiment will be described with reference to FIG. A synthetic quartz substrate 11 having a transparent conductive film 12 laminated thereon was prepared (FIG. 3).
(A)). Here, the transparent conductive film 12 is provided to prevent charge-up during electron beam writing, and indium-titanium oxide is used, but the material is not limited to this.

Next, a coating type glass material OCD type 7 (Tokyo Ohka Kogyo Co., Ltd., trade name, a material which becomes SiO ₂ by heating) is spin-coated on the above substrate as a dielectric film to form a coating film 13. (FIG.3 (b)). The coating type glass material used in this example is sensitive to an electron beam,
Since it acts as a negative type, it can be handled in the same manner as a negative type resist material for electron beams.

Generally, the optimum film thickness of the dielectric film is determined by the equation (1) as described above. Here, d is the thickness of the dielectric film, λ is the wavelength of light, and n is the refractive index of the dielectric at the wavelength λ. Λ used in this example is 365 nm, whereas the refractive index n of the coating type glass film after the heat treatment described below is 1.45. From this, according to the formula (1), the optimum value of the film thickness of the coating type glass is 406 nm. On the other hand, it was found that the coating film 13 had a thickness of 90% of the coating film thickness when the steps described below were performed. Therefore,
In this embodiment, the thickness of the coating film 13 is 451 nm.

Then, a predetermined pattern was drawn with an electron beam irradiation amount of 600 μC / cm ² by using an electron beam drawing apparatus with an acceleration voltage of 30 kV. Then, after developing with methanol for 30 seconds, heat treatment is performed at a temperature of 200 ° C. for 30 minutes to form a periodic linear dielectric pattern 14 having a line width of 0.4 μm and a spacing of 0.4 μm, and a desired optical mask is formed. And (Fig. 3
(C)).

In this embodiment, as described above, an optical mask was produced by forming a dielectric pattern using an electron beam drawing device and a negative photosensitive material for electron beams, but the optical mask was manufactured by various other known methods. It goes without saying that the mask may be manufactured. For example, the transparent substrate may be etched into a dielectric pattern by using the resist pattern as a mask.

The following resist film was exposed using the optical mask manufactured as described above. The resist used was a positive type (photo-soluble type) photosensitive resist NPR-Λ18 SH3 (trade name) manufactured by Nagase Electronic Chemical Co., Ltd. The resist solution was spin-coated on a glass substrate and heated to 80 ° C. for 5 minutes to a thickness of about 0.
The coating film had a thickness of 5 μm. The above optical mask is brought close to this via a spacer of 10 μm in thickness, and at a distance of about 1 m from the 500 W ultra-high pressure mercury lamp, the light from the mercury lamp is passed through the Toshiba glass filter UVD1C, and a relatively large amount of ultraviolet rays with a wavelength of 365 nm is emitted. The contained light was vertically incident on the optical mask, and the resist film was exposed for about 60 seconds by the light transmitted through the optical mask.

The exposed resist film was developed with a 2.38% by weight aqueous solution of tetramethylammonium hydroxide for about 2 minutes, washed with water, and dried to obtain fine parallel stripe resist images. The line width of 0.
It was confirmed that a resist line image of 2 μm was obtained.

Although the thickness of the spacer is 10 μm in this embodiment, the distance between the optical mask and the photosensitive material is not logically limited. However, since the incident light on the optical mask is not completely parallel light in reality, the distance is 1
It is desirable to be within mm. Further, the figure of the optical mask is a parallel striped figure, but it may be another figure such as an orthogonal lattice striped figure.

Example 2 An example will be described in which the optical mask manufactured in Example 1 is used to form parallel lines of extremely fine metal on a transparent substrate. Such metal parallel lines are used as a non-absorbing polarizing filter.

First, an aluminum film was vapor-deposited to a film thickness of 300 nm on a synthetic quartz substrate. In order to process this aluminum film, MP140 is used as the lower organic film.
0 (Shipley Far East Co., Ltd., product name) with a thickness of 0.7 μm, coating type glass material OC as an intermediate film
D type 2 (Tokyo Ohka Kogyo Co., Ltd., trade name) with a film thickness of 1
A positive type photosensitive resist NPR-Λ18SH3 (Nagase Electronic Chemical Co., Ltd., trade name) was laminated to the thickness of 00 nm as an upper layer resist to a thickness of 0.5 μm.

Through this, a spacer having a thickness of 10 μm is used.
The optical mask was brought close to the resist film, and the resist film was exposed for about 60 seconds under the same conditions as in Example 1. The resist film after exposure is 2.
It was developed with a 38% by weight aqueous solution of tetramethylammonium hydroxide for about 2 minutes, washed with water, and dried to obtain a parallel stripe resist image having a line width of 0.3 μm. Next, after heat-treating at 160 ° C. for 120 seconds, the intermediate film and the lower layer film at the positions where no resist image was formed were sequentially dry-etched by reactive fluorine ion etching and reactive oxygen ion etching to form a resist pattern.

This time, using the formed resist pattern as a mask, the aluminum film was dry-etched with chlorine-based gas under the conditions of RF power 140 W, microwave power 580 W and gas pressure 1.3 Pa. Under these conditions, the etching rate of the aluminum film was about 30 times the etching rate of the glass substrate, so that the aluminum film could be etched with high precision. After that, the resist pattern was removed using a hydrofluoric acid and oxygen ashing device, and a line width of 0.3 μm and a period of 0.6 were formed on the glass substrate.
A μm aluminum pattern was formed.

[0028]

As described above, by using the phase shift type optical mask using the dielectric, it becomes possible to perform high resolution exposure which cannot be realized by using the conventional black and white optical mask. In this way, it is not necessary to pay particular attention to keeping the distance between the mask and the photosensitive material small, yet a resolution of one-half the width of the dielectric strip can be obtained. These two characteristics are characteristics that are not found in the conventional contact exposure method, and by using the method of the present invention, it is much cheaper and simpler than the method for evaluating the resolution of a photosensitive material using a practical exposure apparatus. The method enables a higher resolution evaluation than when using a practical exposure apparatus.

The method of the present invention is not only an effective means for evaluating the resolution of a photosensitive material, but by applying this method to the exposure step of a photosensitive resist material in an actual photographic etching method, for example, an extremely fine pattern can be obtained. Parallel lines of different metals can be formed on the transparent substrate, and such parallel lines of metal have practical value as a non-absorbing polarizing filter.

[Brief description of drawings]

1A and 1B are schematic cross-sectional views and bottom views of a conventional black-and-white optical figure mask and a dielectric optical figure mask of the present invention, respectively.

FIG. 2 is a schematic diagram showing interference of diffracted light generated by a conventional black-and-white optical figure mask and a dielectric optical figure mask of the present invention.

FIG. 3 is a manufacturing process diagram of the dielectric optical graphic mask of the present invention used in Example 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Light impermeable film 3 ... Dielectric film 11 ... Synthetic quartz substrate 12 ... Transparent conductive film 13 ... Coating film 14 ... Periodic linear dielectric pattern

Claims (4)

[Claims] 1. A phase shift type optical mask formed of a fine figure-shaped dielectric provided on a substrate is arranged in the vicinity of a photosensitive material film, and the phase shift type optical mask is irradiated with light and diffracted. An exposure method characterized in that a bright and dark image of light generated by light interference is directly transferred to the photosensitive material film. 2. The exposure method according to claim 1, wherein the phase shift type optical mask is 1 mm from the photosensitive material film.
An exposure method characterized in that the exposure method is arranged at a distance within the range. 3. The exposure method according to claim 1, wherein
The exposure method, wherein the fine figure-shaped dielectric is a dielectric having fine parallel stripes. 4. The exposure method according to claim 1, 2 or 3, wherein the thickness of the fine figure-shaped dielectric is d, the wavelength of light irradiating the phase shift type optical mask is λ, When the refractive index of the dielectric at that wavelength is n, d =
An exposure method which satisfies the condition of λ / {2 (n-1)}.