JP2002365784A - Multi-gradation mask, method of forming resist pattern and method of manufacturing optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of gradations of a substantial optical density even when the number of the gradations of the optical density is limited by the thickness of a resist. SOLUTION: The mask is provided with various density patterns 2 where the optical density is varied by the prescribed number of the gradations. The various density patterns 2 have first regions 4 having a first optical density level A, second regions 5 having a second optical density level B next to the first optical density level A and mingled regions 6 mingled with first areas 4a having the first optical density level A and second areas 5a having the second optical density level B between the first regions 4 and the second regions 5. As a result, the gradation C between the first optical density level A and the second optical density level B can be spuriously set in the mingled regions 6 between the first regions 4 and the second regions 5, by which the substantial number of the gradations of the multi-gradation mask 1 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-tone mask having a light and shade pattern having different optical densities at a predetermined number of tones. The present invention also relates to a method for forming a resist pattern using such a multi-tone mask. The present invention also relates to a method for manufacturing an optical element using such a method for forming a resist pattern.

[0002]

2. Description of the Related Art Fields such as wavelength division multiplexing (WDM) optical communication requiring a large amount of optical elements such as small prisms, diffraction gratings, and optical switches are continuing to grow.

Incidentally, optical elements such as a ball lens and a prism for optical communication and an objective lens for an optical pickup are:
With the miniaturization, it has become difficult to manufacture by conventional machining. Some optical elements cannot be manufactured by machining, such as charge-coupled devices (CCD) and lens array elements (microlens arrays) that are attached to the entire surface of the liquid crystal and concentrate and distribute light. Some are.

Therefore, as a method of manufacturing such an optical element, there has been proposed a method using a multi-tone mask having a light and shade pattern in which the optical density (shade) is made different at a predetermined number of tones, that is, a so-called gray scale mask. Have been.

For example, when manufacturing a lens using a gray scale mask, first, as shown in FIG. 17, a photoresist 101 is applied on a glass substrate 100.

[0008] Next, as shown in FIGS. 18 and 19, the exposure of the photoresist 101 is set using a gray scale mask 102 on which a light and shade pattern 102 a is formed. An ultraviolet ray 103 is applied to 101.

Next, as shown in FIG. 20, a resist pattern 104 corresponding to the light and shade pattern 102a of the gray scale mask 102 is formed on the glass substrate 100 by performing development.

Here, when the gray scale mask 102 is used under certain conditions, the amount of exposure to the photoresist 101 changes according to the optical density (shading) of the shading pattern 102a. Thereby, the photoresist 10 after development is
1 can be changed, and a resist pattern 104 corresponding to the shading pattern 102a of the gray scale mask 102 can be formed.

Next, as shown in FIG. 21, the resist pattern 104 is formed on the glass substrate 100 on which the resist pattern 104 is formed.
An anisotropic plasma etching only in the vertical direction is performed with an etching rate of 0 to 1: 1. Thereby, the lens shape 100a corresponding to the resist pattern 104 can be transferred to the glass substrate 100. As described above, a lens can be manufactured.

As described above, if an etching technique such as photolithography or dry etching used in a semiconductor manufacturing process or the like is applied, an optical element can be manufactured with a processing accuracy of 1 μm or less, which is the current design dimension of a semiconductor. it can.

[0011]

By the way, a gray scale mask is produced by irradiating, for example, a special glass containing silver with an electron beam and changing the blackening amount of the glass according to the irradiation amount. Is done. Such mask materials are commercially available from several companies and typically have a mask resolution of about 0.1 μm.

Further, as described above, the gray scale
The exposure of the disk to the photoresist is determined by the optical density (absorption).
It changes in accordance with the number of gradations of (amount). Here, optical density =
log ₁₀(Transmissivity)^-1From the expression, for example,
When the transmittance is 10%, the optical density is 1, and the transmittance is
When the rate is 1%, the optical density is 2. Also usually
The range of optical densities for grayscale masks is approximately
0.15 to 2.0, and the minimum gradation width is about 0.0
It is one. Therefore, this grayscale mask
The large number of gradations is about 185.

When a resist pattern is formed using such a gray scale mask, a problem is how much the thickness of the photoresist after exposure and development changes with respect to a certain optical density difference. .

Here, when the horizontal axis is the optical density of the gray scale mask and the vertical axis is the thickness of the photoresist after exposure and development, the exposure and development when the optical density of the gray scale mask is changed FIG. 22 shows the result of measuring the thickness of the photoresist later.

As can be seen from the measurement results shown in FIG.
The optical density of the gray scale mask is proportional to the thickness of the photoresist, and the straight line s on which the measured values are arranged is generally called a sensitivity straight line.

Further, as shown in FIG. 23, it can be seen that the smaller the inclination of the sensitivity line, the larger the number of gradations of the optical density for a certain photoresist thickness t. For example, the sensitivity straight line b having a smaller slope than the sensitivity straight line a shown in FIG. 22 can provide a larger number of gradations of the optical density with respect to a certain photoresist thickness t. It is advantageous in changing.

However, in the gray scale mask, since the slope of the sensitivity line is determined by the resist material used, the number of gradations of the optical density with respect to the thickness of the photoresist is also determined. Typically, the change in photoresist thickness per gray scale is about 0.1 μm.

For this reason, as schematically shown in FIG.
When a resist pattern is formed using a conventional gray scale mask, the actual resist pattern shape (in FIG. 24) differs from the ideal curved surface shape or slope shape (dashed line shown in FIG. 24) of the resist pattern. (Solid line shown in FIG. 3) is formed with a step of about 0.1 μm.

When an optical element is manufactured, the error in the surface shape is reduced to about 5% of the wavelength of light, that is, about 0.5%.
It needs to be 02 μm. For this reason, when an optical element is manufactured using the above-described resist pattern, the optical resistance of the optical element is reduced to 0.1.
A step of 1 μm has a large error, and as a result, deteriorates the light collecting accuracy and distribution ability of the optical element.

As a solution to this, there has been proposed a method of heating the resist pattern after exposing and developing the photoresist to melt the surface of the resist pattern and smooth the surface of the resist pattern.

However, when such a method is used, it is difficult to control the heating of the resist pattern. If the resist pattern is heated too much, there is a problem that the entire resist pattern is deformed.

From the above, the above-described manufacturing method using the conventional grey-scale mask can be used in a field requiring little processing accuracy, for example, when manufacturing a CCD having a small unit cell or a microlens for a liquid crystal. It is very difficult to use it in a field where high processing accuracy is required, for example, when manufacturing an optical element for an optical pickup or the like.

Therefore, the present invention has been proposed in view of such conventional circumstances, and even when the number of gradations of the optical density is limited by the thickness of the resist, the substantial optical density can be reduced. It is an object to provide a multi-tone mask capable of increasing the number of gradations.

Another object of the present invention is to provide a method of forming a resist pattern which enables a resist pattern to be formed with high resolution by using such a multi-tone mask.

It is another object of the present invention to provide a method for manufacturing an optical element which can manufacture an optical element with high precision by using such a method for forming a resist pattern.

[0026]

In order to achieve this object, a multi-tone mask according to the present invention is provided with a light-and-shade pattern having different optical densities at a predetermined number of gradations. A first area having an optical density level of 1, a second area having a second optical density level next to the first optical density level, and a first area and the second area. It is characterized by having a mixed area in which a first area having a first optical density level and a second area having a second optical density level are mixed.

As described above, in the multi-tone mask according to the present invention, the first optical density level and the second optical density level are set in the mixed area between the first area and the second area. An intermediate gradation can be set in a pseudo manner. Thereby, the substantial number of gradations of the multi-tone mask can be increased.

Further, in the method of forming a resist pattern according to the present invention, the resist is exposed to light by using a multi-tone mask having a light and shade pattern having different optical densities at a predetermined number of tones, and the resist is developed. By,
A resist pattern corresponding to the shading pattern is formed. When exposing the resist, a first region having a first optical density level, a second region having a second optical density level next to the first optical density level, and a first region A light and shade pattern having a mixed area in which a first area having a first optical density level and a second area having a second optical density level are interposed between the first area and the second area; It is characterized in that a multi-tone mask is used.

As described above, in the method for forming a resist pattern according to the present invention, the first optical density level and the second optical density level are set in the mixed area between the first area and the second area. A multi-tone mask capable of pseudo-setting an intermediate gradation between the two is used. This increases the number of substantial tones of the multi-tone mask, so that exposure of the resist can be performed with high resolution using the multi-tone mask, and a resist pattern can be formed with high accuracy.

Further, the method of manufacturing an optical element according to the present invention includes a coating step of coating a resist on a base material to be an optical element, and a multi-step having a light and shade pattern having different optical densities at a predetermined number of gradations. Using a tone mask, exposing the resist and developing the resist to form a resist pattern corresponding to the shading pattern, and etching the base material on which the resist pattern is formed And an etching step.
Then, in the pattern forming step, when exposing the resist, a first region having a first optical density level and a second region having a second optical density level following the first optical density level Having a mixed area in which a first area having a first optical density level and a second area having a second optical density level are interposed between the first area and the second area. It is characterized in that a multi-tone mask provided with a pattern is used.

As described above, in the method of manufacturing an optical element according to the present invention, in the pattern forming step, the first optical density level and the second optical density level are mixed in the mixed area between the first area and the second area. A multi-tone mask capable of setting a gray level intermediate with the optical density level of the image is used. This increases the number of substantial tones of the multi-tone mask, so that exposure of the resist can be performed with high resolution using the multi-tone mask, and a resist pattern can be formed with high accuracy. Therefore, in the etching step, the substrate on which the resist pattern is formed can be accurately etched.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-tone mask, a method of forming a resist pattern, and a method of manufacturing an optical element to which the present invention is applied will be described below in detail with reference to the drawings.

First, as shown in FIG. 1, a gray scale mask 1 to which the present invention is applied will be described.

The gray scale mask 1 has a light and shade pattern 2 having different optical densities with a predetermined number of gradations.

The gray scale mask 1 is produced by irradiating a special glass 3 containing, for example, silver with an electron beam and changing the blackening amount of the glass 3 according to the irradiation amount. Also, this gray scale mask 1
Has, for example, a resolution of about 0.1 μm, an optical density range of about 0.15 to 2.0, and a minimum gradation width of about 0.01. Therefore, the maximum number of gradations of the gray scale mask 1 is about 185.

As shown in FIG. 2, the gradation pattern 2 includes a plurality of regions having different optical densities at a predetermined number of gradations.
A first region 4 having an optional first optical density level A, a second region 5 having a second optical density level B next to the first optical density level A, and these first regions A first area (hereinafter, referred to as an A tile) 4a having a first optical density level A between the first area 4 and the second area 5;
A second zone having a second optical density level B (hereinafter B
It is called a tile. ) 5a are arranged alternately,
And a mixed area 6 in which a so-called checkered pattern is formed. Each of the A tile 4a and the B tile 5a is about 0.1 μm square.

In this case, as shown in FIG. 3, a mixed area 6 between the first area 4 and the second area 5 is provided with the first optical density level A and the second optical density level B. Middle gradation C
Can be set in a pseudo manner. That is, the intermediate gradation C is an intermediate optical density level between the first optical density level A and the second optical density level B.

As a result, in the gray scale mask 1, the number of gradations can be substantially increased. Therefore, when a resist pattern is formed using the gray scale mask 1, a step is suppressed. It is possible to approximate the shape of the actual resist pattern (solid line in FIG. 3) to the ideal curved or sloped resist pattern (broken line in FIG. 3).

Specifically, when exposing a photoresist using this gray scale mask 1, the wavelength of light used for the exposure is about 0.432 μm. Therefore, the A tile 4 provided in the checkered pattern mixed area 6
Since the a and B tiles 5a are sufficiently smaller than the wavelength of this light, the checkered pattern is not transferred to the photoresist by exposure.

Further, in the checkered pattern mixed area 6, by changing the ratio between the A tile 4a and the B tile 5a, the intermediate gradation C can be changed to the first optical density level A or the second optical density level B. It is also possible to set the optical density level closer to

For example, if the resolution of light used for exposure is about 0.4 μm, 16 A tiles 2 a and B tiles 2 b can be arranged in the mixed area 6. , 16 intermediate gray levels can be obtained.

In this case, the step of the resist is about 0.00
Although it is 6 μm, it exceeds the processing accuracy of about 0.02 μm required for manufacturing an ordinary optical element, and thus such a step does not substantially cause a problem.

Next, Embodiment 1 in which a spherical lens as an optical element was manufactured using the above-described gray scale mask 1
Will be described.

In the following description, specific materials and dimensions are exemplified, but the present invention is not necessarily limited to these.

When manufacturing this spherical lens, first, as shown in FIG. 4, a glass substrate 10 serving as a spherical lens is prepared. A plurality of lens shapes are formed from the glass substrate 10 at predetermined intervals, and the glass substrate 10 is cut in accordance with the lens shapes, so that a plurality of spherical lenses are finally manufactured collectively. Will be.

Here, the material of the glass substrate 10 is
Quartz glass having a diameter of about 50.8 mm is used. Also,
The material of the glass substrate 10 is not particularly limited as long as it has a light-transmitting property, has no or very small birefringence, and is capable of reactive ion etching, in addition to the above-described materials. . For example, examples of the material for an optical element for infrared light include silicon, germanium, gallium arsenide, indium phosphide, and cadmium sulfide. In addition, examples of the material for an optical element for red light include gallium phosphide, zinc selenide, cubic silicon carbide, and the like. Examples of optical element materials for blue light include optical plastics, acrylic resins, polycarbonates, CR-39 manufactured by PPG, sulfur-containing urethane resins manufactured by Nikon, and Teslalid (trade name) manufactured by HOYA. Can be mentioned. Further, as the inorganic material, titanium-niobium-containing optical glass, stabilized zirconia, silicon nitride, zinc sulfide, gallium nitride,
Hexagonal silicon carbide and the like can be mentioned.

Next, as shown in FIG. 5, a photoresist material is applied on the glass
Form one.

Here, as a photoresist material, a positive type photoresist AZP manufactured by Clariant Japan Co., Ltd. is used.
Using 4903, a resist layer 11 having a film thickness of about 17 μm is formed by uniformly applying the solution on the glass substrate 10 using a spin coater manufactured by Mikasa Corporation and then heating it on a hot plate for 3 minutes. As such a photoresist material, in addition to the above-mentioned materials, a positive type photoresist AZP4400 manufactured by Clariant Japan Co., Ltd.
And AZP4620, PMER P- manufactured by Tokyo Ohka Kogyo Co., Ltd.
LA900PM and PMER P-LA1300PM, J
Examples include THB-500P and THB-611P manufactured by SR Corporation.

Next, as shown in FIGS. 6 and 7, the gray scale mask 1 on which the above-described light and shade pattern 2 is formed
The resist layer 11 is irradiated with ultraviolet rays 12 through the gray scale mask 1 while setting the exposure of the resist layer 11 by using.

Here, as a material of the gray scale mask 1, Canyon Materials (Canyon Materials) is used.
Inc.) is used. Further, the shade pattern 2 is formed by irradiating such a special glass with an electron beam to form the above-mentioned checkered pattern. Further, the material of the gray scale mask 1 is not necessarily limited to a material commercially available from NIPT Inc., as long as a light and shade pattern 2 such as a photographic plate can be formed.

The gray scale mask 1 has 64 gradations. The wavelength of light used for exposure is
About 0.432 μm, and the exposure amount is 200 mJ / cm
² .

Next, as shown in FIG. 8, a resist pattern 13 having a predetermined shape is formed on the glass substrate 10 by performing development.

Here, A manufactured by Clariant Japan Co., Ltd.
Z400K (main component is aqueous potassium hydroxide solution) 4: 1
The exposed portion of the resist layer 11 is dissolved and removed using a developing solution diluted with water, washed with water, and then the resist pattern 13 formed on the glass substrate 10 is dried.

Here, when the gray scale mask 1 is used under certain conditions, the amount of exposure to the resist layer 11 changes according to the optical density (shading) of the shading pattern 2. Thereby, the thickness of the resist layer 11 after development can be changed, and a resist pattern 13 corresponding to the shading pattern 2 of the gray scale mask 1 can be formed.

Next, as shown in FIG. 9, using an inductively coupled plasma-reactive ion etching apparatus, the glass substrate 10 having the resist pattern 13 formed thereon is
For example, the etching rate between the resist pattern 13 and the glass substrate 10 is 1: 1 and anisotropic plasma ion etching is performed only in the vertical direction. As a result, the lens shape 10a corresponding to the resist pattern 13 is
0 can be transferred. Here, ICP-RIE manufactured by STS is used as an etching apparatus, and a mixed gas of carbon tetrafluoride and oxygen is used as an etching gas.

By cutting the glass substrate 10 having been subjected to the above-described etching processing in accordance with the lens shape 10a, the spherical lens of the first embodiment is manufactured.

Here, when fabricating the spherical lens of Example 1, the cross-sectional shape of the resist pattern 13 formed by using the gray scale mask 1 to which the present invention was applied was changed to zy.
The measurement was performed using an interference microscope NewView100 manufactured by Go. FIG. 11 shows the measurement results.

As Comparative Example 1, a spherical lens was manufactured in the same manner as in Example 1 except that a conventional gray scale mask having no checkered pattern mixed area was used. Then, when producing the spherical lens of Comparative Example 1, the cross-sectional shape of a resist pattern formed using a conventional gray scale mask was measured using an interference microscope NewView100 manufactured by zygo.
FIG. 11 shows the measurement results.

From the measurement results shown in FIG. 10 and FIG. 11, the gray scale mask 1 to which the present invention is applied can substantially increase the number of gradations. It can be seen that the resist pattern shown in FIG. 10 has a smoother arc shape with a reduced level of difference than the resist pattern formed using the conventional gray scale mask shown in FIG. As described above, when the gray scale mask 1 to which the present invention is applied is used, it is possible to form the resist pattern 13 which is very similar to the design value of the desired resist pattern.

Next, a second embodiment will be described.
An aspherical lens was manufactured in the same manner as in the case of manufacturing the spherical lens, that is, using the gray scale mask 1 provided with the checkered pattern mixed area 6.

On the other hand, as Comparative Example 2, Comparative Example 1 described above was used.
An aspherical lens is produced using the same method as that of the first embodiment except that a conventional gray scale mask having no checkered pattern mixed area is used. Was prepared.

For the spherical lens of Example 1, the aspherical lens of Example 2, and the aspherical lens of Comparative Example 2, the focal images of the laser light irradiated through each lens were measured. FIGS. 12, 13 and 14 schematically show the measured focal images of the respective lenses.

From the measurement results shown in FIGS. 12, 13, and 14, the focal image of Example 1 shown in FIG. 12 is smaller than the focal image of Comparative Example 2 shown in FIG. 14, and the occurrence of aberration is suppressed. You can see that there is. Furthermore, the focal image of Example 2 shown in FIG. 13 is smaller than the focal image of Example 1 shown in FIG. 12, and it can be seen that the occurrence of aberration is suppressed.

Incidentally, an aspherical lens is very effective in correcting spherical aberration generated by one spherical lens optical system. However, the difference between the shapes of the aspherical lens and the spherical lens is as small as about 0.1 μm, and when the aspherical lens is manufactured using a conventional gray scale mask, the shape of the aspherical lens and the spherical lens is reduced. It is difficult to properly express the difference between the two.

On the other hand, when an aspheric lens is manufactured using the gray scale mask 1 to which the present invention is applied, the substantial number of gradations of the gray scale mask 1 increases, so that the The difference in shape from the lens can be appropriately expressed, and an aspheric lens can be easily manufactured.

As described above, in the gray scale mask 1 to which the present invention is applied, the first optical density level A and the first optical density level A are located between the first area 4 and the second area 5 of the gray pattern 2. Since the mixed area 6 having the intermediate gradation C with the second optical density level B is provided, even if the number of gradations of the optical density is limited by the thickness of the resist layer 11, this gray level is not changed. It is possible to increase the number of gradations of the substantial optical density of the scale mask 1.

Therefore, the use of such a gray scale mask 1 makes it possible to set the exposure of the resist layer 11 at a high resolution, so that the resist pattern 13 can be precisely formed on the glass substrate 10 described above. It is possible to form.

Further, by using such a resist pattern 13, it is possible to perform a highly accurate etching process on the glass substrate 10, so that an optical element with improved quality can be easily manufactured. It is.

For example, when an on-chip microlens of a charge-coupled device (CCD) is manufactured as an optical element manufactured by applying the present invention, by improving the light-collecting efficiency of the on-chip microlens, the CCD is improved. Can be improved. If the sensitivity of the CCD is improved, the number of pixels of the CCD can be increased and the size of the CCD can be reduced.

Further, when a lens array element (microlens array) for a liquid crystal is manufactured, the light distribution efficiency of the microlens array is improved, so that a projected image can have higher definition.

Further, when an optical pickup for an optical recording disk is manufactured, it is possible to improve the recording density and the like by increasing the precision.

In the field of wavelength division multiplexing (WDM) optical communication, the number of wavelengths that can be multiplexed is increased and the size of the optical element itself is reduced by manufacturing optical elements such as prisms and diffraction gratings with high precision. Becomes possible. Further, by increasing the precision of the optical waveguide, it is possible to reduce the size of the optical switch, increase the number of multiplexable wavelengths, and the like. Therefore, it is possible to realize an increase in communication speed, a reduction in the unit price of information bits, a reduction in size of the device, a reduction in price, and the like.

In the above description, the gray scale mask 1 in which a checkered pattern is formed in the mixed area 6 has been described. However, the present invention is not necessarily limited to such a structure. That is, in the gray scale mask to which the present invention is applied, among a plurality of regions having different optical densities by a predetermined number of gradations of a gray pattern, a first region having an arbitrary first optical density level A A second optical density level B next to the first optical density level A;
A first optical density level A having a first optical density level A
And a second area having the second optical density level B may be provided.

For example, as shown in FIG.
A first area 4b having a first optical density level A between the first area 4 and the second area 5 along a direction in which the first area 4 and the second area 5 are arranged; Optical density level B
May be provided in which the mixed region 7 of the vertical stripe pattern in which the second areas 5b having

In this case, the above-described checkered pattern mixed area C is used.
Is provided in the mixed area 7 between the first area 4 and the second area 5 in the same manner as the gray scale mask 1 provided with the first optical density level A and the second optical density level B. Can be set in a pseudo manner, and the substantial number of tones of the gray scale mask can be increased.

As shown in FIG. 16, the first region 4
Between the first region 4 and the second region 5 along a direction substantially orthogonal to the direction in which the first region 4 and the second region 5 are arranged.
The first zone 4c having the optical density level A and the second zone 5c having the second optical density level B are arranged alternately in a horizontal stripe pattern mixed region 8 even if the structure is provided. Good.

Also in this case, like the gray scale mask 1 provided with the checkered pattern mixed area 6 described above, the first
In the mixed area 8 between the area 4 and the second area 5, a gray level E intermediate between the first optical density level A and the second optical density level B can be set in a pseudo manner. Yes, it is possible to increase the substantial number of gradations of the gray scale mask.

[0078]

As described above in detail, according to the present invention, an intermediate gradation between the first optical density level and the second optical density level is pseudo-set in the mixed area of the light and shade patterns. Therefore, even when the number of gradations of the optical density is limited by the thickness of the resist, it is possible to increase the number of gradations of the substantial optical density of the multi-tone mask. .

Therefore, by using such a multi-tone mask, the resist can be exposed at a high resolution, so that the resist pattern can be formed with high precision.

In addition, by using such a resist pattern, it is possible to perform highly accurate etching on a base material to be an optical element, so that an optical element with improved quality can be easily manufactured. It is possible.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a gray scale mask to which the present invention is applied.

FIG. 2 is an enlarged plan view of a main part of the gray scale mask on which a checkered pattern is formed.

FIG. 3 is a characteristic diagram for explaining a relationship between an ideal shape and an actual shape when the gray scale mask is used.

FIG. 4 is a diagram for explaining a manufacturing process of a spherical lens using the gray scale mask, and is a schematic cross-sectional view showing a glass substrate to be a spherical lens.

FIG. 5 is a diagram for explaining a manufacturing process of a spherical lens using the gray scale mask, and is a schematic cross-sectional view showing a state where a resist layer is formed on a glass substrate.

FIG. 6 is a view for explaining a manufacturing process of a spherical lens using the gray scale mask, and is a schematic plan view showing a state where a resist layer is irradiated with ultraviolet rays through the gray scale mask.

FIG. 7 is a diagram for explaining a manufacturing process of a spherical lens using the gray scale mask, and is a line segment X- in FIG. 6;
It is a schematic sectional drawing by X '.

FIG. 8 is a diagram for explaining a manufacturing process of a spherical lens using the gray scale mask, and is a schematic cross-sectional view showing a state where a resist pattern is formed on a glass substrate.

FIG. 9 is a diagram for explaining a manufacturing process of the spherical lens using the gray scale mask, and is a schematic cross-sectional view showing a state where a lens shape is transferred to a glass substrate.

FIG. 10 is a characteristic diagram illustrating a cross-sectional shape of a resist pattern formed using the gray scale mask as Example 1.

FIG. 11 is a characteristic diagram illustrating a cross-sectional shape of a resist pattern formed using a conventional gray scale mask as Comparative Example 1.

FIG. 12 is a schematic diagram showing a focal image of laser light emitted through the spherical lens of Example 1.

FIG. 13 is a schematic diagram illustrating a focal image of laser light emitted through an aspheric lens according to a second embodiment.

FIG. 14 is a schematic diagram showing a focal image of laser light emitted through an aspheric lens of Comparative Example 2.

FIG. 15 is an enlarged plan view of a main portion of another grayscale mask to which the present invention is applied, in which a vertical stripe pattern is formed.

FIG. 16 is an enlarged plan view of a main part of another grayscale mask to which the present invention is applied, in which a horizontal stripe pattern is formed.

FIG. 17 is a view for explaining a manufacturing process of a lens using a conventional gray scale mask, and is a schematic cross-sectional view showing a state where a photoresist is applied on a glass substrate.

FIG. 18 is a view for explaining a lens manufacturing process using the above-mentioned conventional gray scale mask, and is a schematic plan view showing a state where a resist layer is irradiated with ultraviolet rays through the gray scale mask.

FIG. 19 is a diagram for explaining a manufacturing process of the lens using the above-described conventional gray scale mask, and is a schematic cross-sectional view taken along line YY ′ in FIG.

FIG. 20 is a diagram for explaining a manufacturing process of the lens using the conventional gray scale mask, and is a schematic cross-sectional view showing a state where a resist pattern is formed on a glass substrate.

FIG. 21 is a diagram for explaining a manufacturing process of a lens using the above-mentioned conventional gray scale mask, and is a schematic cross-sectional view showing a state where a lens shape is transferred to a glass substrate.

FIG. 22 is a characteristic diagram showing the relationship between the optical density of a gray scale mask and the thickness of a photoresist.

FIG. 23 is a characteristic diagram showing the relationship between the slope of the sensitivity line and the thickness of the photoresist.

FIG. 24 is a characteristic diagram for explaining a relationship between an ideal shape and an actual shape when the conventional gray scale mask is used.

[Explanation of symbols]

1 gray scale mask, 2 shading pattern, 4 first area, 5 second area, 4a A tile (first area), 5a B tile (second area), 6 mixed area,
Reference Signs List 10 glass substrate, 10a lens shape, 11 resist layer, 12 ultraviolet ray, 13 resist pattern

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H042 AA06 AA11 AA12 AA25 2H095 BB02 BB36 BC09 2H096 AA28 EA30 HA23 JA04

Claims (11)

[Claims] 1. A light and shade pattern having different optical densities with a predetermined number of gradations is provided, wherein the light and shade pattern includes a first area having a first optical density level, and a first area having a first optical density level. A second region having a next second optical density level; and a first region having the first optical density level between the first region and the second region.
And a mixed area in which the second area having the second optical density level is mixed. 2. The multi-tone mask according to claim 1, wherein the first area and the second area form a checkered pattern in the mixed area. 3. The multi-tone mask according to claim 1, wherein the first area and the second area form a stripe pattern in the mixed area. 4. A resist corresponding to the gradation pattern by exposing the resist using a multi-tone mask having a gradation pattern having different optical densities with a predetermined number of gradations and developing the resist. In the method of forming a resist pattern for forming a pattern, when exposing the resist, a first region having a first optical density level and a second optical density level subsequent to the first optical density level are set. A second region having
A mixed area in which a first area having the first optical density level and a second area having the second optical density level are interposed between the first area and the second area; A method of forming a resist pattern, comprising using the multi-tone mask provided with the light and shade pattern having the following. 5. The method according to claim 4, wherein the first area and the second area form a checkered pattern in the mixed area. 6. The method according to claim 4, wherein the first area and the second area form a striped pattern in the mixed area. 7. A coating step of coating a resist on a substrate to be an optical element, and exposing the resist to light using a multi-tone mask having a gradation pattern having different optical densities at a predetermined number of gradations. And forming the resist by developing the resist to form a resist pattern corresponding to the light and shade pattern, and an etching step of etching the base material on which the resist pattern is formed; In the forming step, when exposing the resist, a first region having a first optical density level and a second region having a second optical density level subsequent to the first optical density level; A first section having the first optical density level and a second section having the second optical density level between the first area and the second area;
Using the multi-tone mask provided with the light and shade pattern having a mixed area in which the areas are mixed. 8. The method according to claim 7, wherein the first area and the second area form a checkered pattern in the mixed area. 9. The method according to claim 7, wherein the first area and the second area form a stripe pattern in the mixed area. 10. The method according to claim 7, wherein the optical element is an optical lens. 11. The method according to claim 10, wherein the optical lens is an aspherical lens.