JPH06186412A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To efficiently produce fine patterns continuously changing in height. CONSTITUTION:Light transmissive parts or light shielding parts are separated to a plurality at the time of forming prescribed patterns on a photoresist 6. A photomask formed by making the ratio of the areas of the light parts or light shielding parts correspondent to a change in the heights of the patterns is used. An exposure distribution is applied to the photoresist 6 by exposing the photoresist 6 via this photomask, by which such patterns as to have the varying heights to a substrate 1 are formed on the photoresist 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a fine pattern.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a fine pattern such as a blazed grating whose height continuously changes, a method disclosed in, for example, Japanese Patent Application Laid-Open No. 2-100004 is known. This method, as shown in FIG.
The electron beam resist 2 is applied on the substrate 1, and then, FIG.
As shown in (b), the electron beam 3 is scanned while the dose amount is changed in a linear function, and after the development, as shown in FIG.
As shown in (c), this is a method of forming the blaze pattern 4 on the substrate 1.

[0003]

However, the above-mentioned conventional method has a problem that it takes a very long time to draw because it is directly drawn by the electron beam 3 and the mass productivity is poor. The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a method for producing a fine pattern capable of efficiently producing a fine pattern whose height continuously changes (slope change). .

[0004]

In order to solve the above-mentioned problems, according to the present invention, when a photoresist is applied on a substrate and a predetermined pattern is formed on the resist, the height with respect to the substrate (resist thickness ) Changes,
In a method of forming a fine pattern on the substrate based on this pattern, when forming a predetermined pattern on the resist, a light-transmitting portion or a light-shielding portion is divided into a plurality of light-transmitting portions. Alternatively, by using a photomask in which the ratio of the area of the light-shielding portion corresponds to the change of the height of the pattern (thickness of the resist), the resist is exposed through the photomask to give an exposure dose distribution to the resist. It was decided to form a pattern on the resist such that the height (resist thickness) with respect to the substrate changes.

Further, according to the present invention, when a photoresist is applied on a substrate and a predetermined pattern is formed on the resist,
A pattern is formed such that the height (resist thickness) with respect to the substrate changes, and a predetermined pattern is formed on the resist in a method of forming a fine pattern on the substrate based on this pattern. At this time, a film thickness of a light shielding material that absorbs light in a wavelength range in which the resist reacts is used by using a photomask formed so as to correspond to a change in height of the pattern (thickness of the resist). By exposing the resist to give an exposure amount distribution to the resist, it was decided to form a pattern on the resist such that the height with respect to the substrate (resist thickness) is changed.

[0006]

[Function] In order to obtain a fine pattern, contact exposure using a photomask, rather than direct drawing (single stroke exposure) with a beam such as an electron beam or a laser beam,
It is clear that the projection exposure of the reticle allows a larger area to be exposed at one time, and thus is superior in mass productivity.

By the way, the photoresist has sensitivity, and the exposure amount and the residual film ratio (ratio of the film thickness of the photoresist remaining after the development) are as shown in FIG. 2, that is, the residual amount gradually increases as the exposure amount increases. There is a relationship that the film rate decreases.
Therefore, if the intensity of the light striking the photoresist is spatially continuously distributed and appropriately controlled, it is possible to obtain a resist pattern whose height continuously changes spatially after development.

Therefore, as in the present invention shown in FIG. 3, a substrate is formed by using a photomask 5 which produces an intensity distribution in which the spatial intensity distribution of light passing through the photomask 5 changes spatially continuously. By exposing the photoresist 6 applied on the substrate 1, the resist thickness after development is thicker in the portion where the light intensity is low, and the resist thickness after development is thinner in the portion where the light intensity is higher. As a result, as shown in FIG. 1, a resist pattern whose height continuously changes spatially can be obtained.

By the way, in order to obtain the photomask 5 as described above, as shown in FIG. 4, the area ratio between the divided adjacent light shielding portions 7, that is, the area of the light transmitting portion (opening portion) 8. The ratio may be changed according to the height of the desired resist pattern (thickness of the photoresist). here,
The total amount of light transmitted through the photomask 5 is proportional to the area of the transparent portion 8. However, the transmitted light spreads due to the diffraction phenomenon and has a mountain-shaped intensity distribution, as shown in FIG.
Therefore, when exposure is performed using such a photomask 5, as shown in FIG. 6, due to the light (b) that passes through each portion and is diffracted, the entire intensity distribution is continuous as shown in (c). Will change. Therefore, when the photoresist 6 is exposed using the photomask 5 and developed, a resist pattern that changes into a gentle mountain shape can be obtained as shown in FIG.

Further, as shown in FIG.
The film thickness of the light shielding portion 7 may be continuously changed in accordance with the desired height of the resist pattern. In this case, since the light transmittance changes according to the film thickness of the light shielding portion 7, the spatial intensity distribution of the light passing through the photomask 5 is substantially the same as the film thickness distribution of the light shielding portion 7, as shown in FIG. The intensity distribution is similar.

[0011]

[Embodiment 1] FIG. 10 shows a cross-sectional shape of a desired fine pattern of the present embodiment. This fine pattern has a right-angled triangular shape with a base length of 2.5 μm and a height of 1 μm. The photomask for forming such a fine pattern is configured as follows. That is, FIG.
The horizontal direction of the right-angled triangle shown in 0 is divided into five equal parts as shown in FIG. 11, and the average value of the heights of the divided parts (the average value for the hypotenuse) is calculated as shown in FIG. The photomask 5 has an area ratio of the light shielding portion 7 in the corresponding portion 9 of the photomask 5 corresponding to each divided portion. As shown in FIG. 13, the exposure is performed on the photoresist 6 coated on the substrate 1 through the photomask 5. The light transmitted through the photomask 5 is diffracted, and the light intensity distribution becomes a distribution that continuously changes as shown in FIG.

When the photoresist 6 is exposed to the light having the intensity distribution shown in FIG. 14, the residual film rate due to the development of the photoresist 6 changes depending on the light intensity of the exposure. In this case, assuming that the photoresist 6 is a positive type, the shape of the photoresist 6 after development is a desired fine pattern in the shape of a right triangle as shown in FIG.

[0013]

[Embodiment 2] FIG. 16 shows the shape of a fine pattern formed in this embodiment, which is a blazed grating used in an optical element, a spectroscope or the like. The pitch is 5 μm and the height is 0.5 μm. As shown in FIG. 17, the photomask 5 used in the present embodiment has one sawtooth shape of the fine pattern divided into 5 in every 1 μm in the lateral direction, and the average height of each divided portion is h. , H / 0.5 is defined as the area ratio of the light shielding portion 7 to the total area of the corresponding portion 9 of the photomask 5 corresponding to the divided portion. The photomask 5 is a chrome mask and is created by electron beam drawing. To perform exposure using this photomask 5, as shown in FIG. 18, first, the glass substrate 1 is used.
After performing a silane coupling treatment on the above, a standard positive photoresist 6 is applied by a spin coater, a roll coater or a spray coater, and prebaked.
Next, the photomask 5 is brought into close contact with the photoresist 6 and exposed.

At this time, the light passing through the photomask 5 is
As shown in FIG. 19, a sawtooth-like intensity distribution is shown by diffraction. Then, the photoresist 6 is exposed according to the light intensity. Here, the portion where the light intensity is strong is the photoresist 6
Although it is exposed to the bottom of the film thickness of, the weak light intensity is exposed to the film surface of the photoresist 6, and the exposed portion for absorbing light by the resist itself does not reach the bottom of the film thickness. afterwards,
When development is performed, the residual film rate of the photoresist 6 depends on the photosensitivity, so that the resist pattern after development is almost as shown in FIG.
A desired fine pattern is obtained with the shape shown in FIG. According to this embodiment, a blazed grating pattern can be obtained with good production efficiency by a simple method of contact exposure.

[0015]

[Embodiment 3] FIG. 20 shows the shape of a diffraction grating type optical low-pass filter prepared in this embodiment. In the photomask 5 used in this embodiment, when the pattern is divided into 10 μm in the pitch direction and the average height of each divided portion is h, a value of h / 0.5 corresponds to the divided portion. The area ratio of the transparent portion to the total area of the corresponding portion of the photomask 5 is set. To perform exposure using this photomask 5, as shown in FIG. 21, first, a silane coupling treatment is performed on the quartz glass substrate 1, and then a spin coater,
A negative type photoresist 6 is applied with a roll coater or a spray coater and prebaked. Next, the photomask 5 is brought into close contact with the bottom of the substrate 1, and the photoresist 6 on the substrate 1 is exposed from the substrate 1 side.

At this time, the light passing through the photomask 5 is
Diffraction shows an intensity distribution as shown in FIG. Then, as shown in FIG. 23, the photoresist 6 is exposed according to the light intensity. The exposed portion becomes insoluble in the developing solution. Therefore, when the development is performed thereafter, FIG.
A negative resist pattern as shown in FIG.

According to this embodiment, the shape of the diffraction grating type optical low-pass filter can be obtained with high productivity by a simple method. This can be used not only as an element as it is, but also as a master for electroforming the resist pattern obtained in the present embodiment to produce a mold for plastic molding. It is also possible to process the surface of the substrate into a desired shape by performing dry etching such as ion milling or RIBE using the obtained resist pattern as an etching mask.

In this embodiment, a negative type photoresist is used as the photoresist 6, so that
When the photomask 5 is placed on the photoresist 6 and exposed as described above, the resist removed by the development and the resist remaining on the substrate 1 after the development are reversed, so that the above pattern cannot be obtained. Therefore, in this embodiment,
By exposing the photoresist 6 from the substrate side rather than from the resist side, it is possible to form a fine pattern even when the negative photoresist 6 is used.

[0019]

Fourth Embodiment FIGS. 24 to 28 show the manufacturing process of the photomask 5 used in this embodiment. First, as shown in FIG. 24, 20 parts of cerium oxide 11 was formed on the quartz mask substrate 10.
00Å Vacuum deposition. Next, as shown in FIG. 25, an electron beam resist 12 is spin-coated on the cerium oxide 11 at 3500 Å. Next, as shown in FIG.
The electron beam resist 12 is exposed while the irradiation amount (dose amount) of the electron beam 13 is periodically changed by a drawing device (not shown). After that, development is performed to obtain a blazed resist pattern as shown in FIG. Next, with argon ion beam, applied voltage 500V, current 0.56m
The resist pattern is subjected to ion beam etching under the condition of A / cm ² . When the etching is performed for 10 minutes, the electron beam resist 12 and the cerium oxide 11 are etched, and a blazed cerium oxide pattern is obtained as shown in FIG. This is the photomask 5 in this embodiment.
Used as.

When a positive type photoresist is exposed using this photomask 5 in the same manner as in Example 2, approximately 2000 liters of cerium oxide 11 cuts out almost 100% of the ultraviolet rays which expose the photoresist. The intensity of the transmitted light is as shown in FIG. 19, and as a result, a blazed grating similar to that of the second embodiment can be obtained.

According to this embodiment, since the photomask 5 has a smooth film thickness of the absorbing material in the ultraviolet region, it is easy to control the light intensity distribution of the transmitted light.
The material of the film is not limited to cerium oxide, but may be any material that absorbs in the ultraviolet region, such as molybdenum oxide, indium oxide, ITO, and silicon oxide.

[0022]

As described above, according to the method of forming a fine pattern of the present invention, a fine pattern having a shape whose height continuously changes can be obtained with high productivity.

[Brief description of drawings]

FIG. 1 is a front view showing a resist pattern to be obtained by the present invention.

FIG. 2 is a graph showing a relationship between an exposure amount and a residual film rate.

FIG. 3 is a front view showing an exposed state in the manufacturing method of the present invention.

FIG. 4 is a front view showing an example of a photomask used in the present invention.

FIG. 5 is a light intensity distribution diagram showing a light intensity distribution of a light transmitting part when exposed using the photomask shown in FIG.

FIG. 6 is a light intensity distribution chart showing a light intensity distribution over the whole when exposure is performed using the photomask shown in FIG.

7 is a front view showing a resist pattern obtained when exposure is performed using the photomask shown in FIG.

FIG. 8 is a front view showing an example of a photomask used in the present invention.

9 is a light intensity distribution chart showing a light intensity distribution showing the entire light intensity distribution when exposed using the photomask shown in FIG.

FIG. 10 is a vertical cross-sectional view showing a fine pattern obtained in Example 1 of the present invention.

11 is a front view showing a divided state of the fine pattern shown in FIG.

FIG. 12 is a bottom view showing the main part of the photomask used in Example 1 of the present invention.

FIG. 13 is a front view showing an exposure state of the first embodiment.

FIG. 14 is a light intensity distribution diagram showing a light intensity distribution over the entire area when exposure is performed using the photomask shown in FIG.

FIG. 15 is a front view showing the shape of the photoresist obtained in Example 1 of the present invention.

FIG. 16 is a front view showing a fine pattern obtained in Example 2 of the present invention.

FIG. 17 is a bottom view showing the photomask used in the second embodiment.

FIG. 18 is a front view showing an exposure state of the second embodiment.

FIG. 19 is a light intensity distribution chart showing a light intensity distribution when exposed in the second embodiment.

FIG. 20 is a front view showing the shape of a diffraction grating type optical low-pass filter obtained in Example 3 of the present invention.

FIG. 21 is a front view showing an exposure state of the third embodiment.

FIG. 22 is a light intensity distribution chart showing a light intensity distribution at the time of exposure in the third embodiment.

FIG. 23 is a front view showing a photosensitive state of the photoresist of Example 3.

FIG. 24 is a process drawing showing the manufacturing process of the photomask used in Example 4 of the present invention.

FIG. 25 is a process drawing showing the manufacturing process of the photomask used in the fourth embodiment.

FIG. 26 is a process drawing showing the manufacturing process of the photomask used in the fourth embodiment.

FIG. 27 is a process drawing showing the manufacturing process of the photomask used in Example 4 of the present invention.

FIG. 28 is a process drawing showing the manufacturing process of the photomask used in Embodiment 4.

FIG. 29 is a process drawing showing a conventional fine pattern forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electron beam resist 3 Electron beam 4 Blazed pattern 5 Photomask 6 Photoresist 7 Photoreceptive part 8 Light transmitting part 9 Corresponding part 10 Quartz mask substrate 11 Cerium oxide 12 Electron beam resist 13 Electron beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/027

Claims (2)

[Claims] 1. When a photoresist is applied on a substrate and a predetermined pattern is formed on the resist, a pattern is formed such that the height with respect to the substrate changes, and a fine pattern is formed on the substrate based on this pattern. In the method of forming a fine pattern to be formed, when a predetermined pattern is formed on the resist, a light-transmitting portion or a light-shielding portion is divided into a plurality of portions, and the ratio of the area of the light-transmitting portion or the light-shielding portion is defined as the height of the pattern. Is used to form a pattern in which the height with respect to the substrate is changed by exposing the resist through the photomask and giving an exposure amount distribution to the resist using the photomask. How to create a fine pattern. 2. When a photoresist is applied on a substrate and a predetermined pattern is formed on the resist, a pattern is formed such that the height with respect to the substrate changes, and a fine pattern is formed on the substrate based on this pattern. In the method of forming a fine pattern to be formed, when forming a predetermined pattern on the resist, the film thickness of a light shielding material that absorbs light in a wavelength range in which the resist reacts is made to correspond to a change in height of the pattern. A fine pattern characterized by forming a pattern on the resist whose height with respect to the substrate changes by using the formed photomask and exposing the resist through the photomask to give an exposure dose distribution to the resist. How to create.