JP2007156055A - Gray scale mask, manufacturing method of microlens, microlens, spatial optical modulating device, and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gray scale mask etc., capable of avoiding forming a step shape due to a distribution like stepped variation in light transmissivity and accurately forming a resist shape. <P>SOLUTION: The gray scale mask which has a distribution of light transmissivity determined to expose a resist layer in specified pattern has a plurality of unit cells whose light transmissivities are respectively set, and also has a distribution LD2 of light transmission quantities determined to form a second resist shape by using the resist layer exposed corresponding to a first resist shape, and the distribution of light transmissivity is shifted by a length shorter than the width of a unit cell as compared with a case wherein the resist layer is exposed corresponding to the first resist shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a gray scale mask, a microlens manufacturing method, a microlens, a spatial light modulator, and a projector, and more particularly to a grayscale mask technique for manufacturing an optical element such as a microlens having a three-dimensional microstructure.

Conventionally, for example, a photolithography technique is used in the manufacture of an optical element having a three-dimensional microstructure. Photolithography is a technique in which a resist layer, which is a photoreactive photosensitive material, is applied to a substrate, exposed to light, and developed to form a pattern on the resist layer. The pattern of the resist layer can be formed on the substrate by performing etching after forming the pattern on the resist layer. As a method of forming a desired pattern on the resist layer, for example,
A technique for exposing a resist through a gray scale mask is used. The gray scale mask includes a plurality of unit cells each having a light transmittance corresponding to a desired resist shape. The light transmittance of the unit cell can be determined by, for example, an area aperture ratio that is a ratio of the area of the opening portion in the unit cell. As a technique using a gray scale mask that determines the light transmittance based on the area aperture ratio, for example, there is a technique proposed in Patent Document 1. The technique proposed in Patent Document 1 prepares a plurality of gray scale masks, and when using at least one gray scale mask, makes the exposure time different from when using another gray scale mask. For example, Patent Document 2 proposes a technique for heat-treating a resist.

JP 2004-310077 A JP 2003-91066 A

When the light transmittance is changed for each unit cell, the light transmittance of the gray scale mask is distributed so as to change stepwise in the two-dimensional direction. A shape may be formed. Since the optical element is required to have an accurate shape in order to perform functions such as light refraction, it is desired to avoid the formation of a step shape that is not in the design. On the other hand, it is conceivable that varying the exposure time in a plurality of gray scale masks does not change the roughness of the distribution of the resist depth in the two-dimensional direction, and the formation of the step shape cannot be avoided. By subjecting the resist to heat treatment, there may be a case where an accurate shape cannot be obtained due to the influence of heating up to the depth and curvature of the resist shape even if the step shape can be smoothed. As described above, in the conventional technique, it is difficult to avoid the formation of the step shape due to the light transmittance being distributed in a stepwise manner, and thus it is difficult to obtain an accurate resist shape. Produce. The present invention has been made in view of the above-described problems, and can avoid the formation of a step shape due to the light transmittance being distributed so as to change stepwise, and can accurately form a resist shape. An object of the present invention is to provide a gray scale mask, a microlens manufacturing method, a microlens, a spatial light modulator, and a projector.

In order to solve the above-described problems and achieve the object, according to the present invention, a gray scale mask in which a light transmittance distribution is determined to expose a resist layer in a predetermined pattern,
The distribution of light transmittance is determined so as to form a second resist shape using a resist layer having a plurality of unit cells each having a light transmittance set and exposed according to the first resist shape. And providing a gray scale mask characterized in that the light transmittance distribution is shifted by a length shorter than the width of the unit cell as compared with the case where the resist layer is exposed in accordance with the first resist shape. Can do.

For the exposure according to the first resist shape, a gray scale mask having a light transmittance distribution similar to the conventional one can be used. By shifting the light transmittance distribution by a length shorter than the width of the unit cell compared to the case where the resist layer is exposed according to the first resist shape,
Compared with the case where only exposure according to the first resist shape is performed, the light transmittance distribution can be set finely. By making the light transmittance distribution fine, the change in the amount of light on the resist layer can be made close to a continuous one, and a smooth surface can be formed. As a result, it is possible to avoid the formation of a step shape due to the light transmittance being distributed so as to change stepwise, and to obtain a gray scale mask capable of accurately forming a resist shape.

Further, according to a preferred aspect of the present invention, the light transmittance distribution can be shifted by approximately half the width of the unit cell as compared with the case where the resist layer is exposed according to the first resist shape. desirable. By shifting the light transmittance distribution by approximately half the length of the unit cell with respect to the first resist shape, it becomes possible to make the change in the amount of light on the resist layer more continuous. Thereby, a smooth surface can be formed.

Further, according to the present invention, the first exposure step of exposing the resist layer using the gray scale mask whose light transmittance distribution is determined according to the first resist shape, and the first resist shape according to the first resist shape. A second exposure step of exposing the resist layer using a gray scale mask whose light transmittance distribution is determined so as to form a second resist shape using the exposed resist layer; and a second resist A lens shape forming step of forming a lens shape by transferring the shape to another member, and a light transmittance distribution is determined by a plurality of unit cells each having a light transmittance set, The light transmittance distribution for forming the second resist shape in the exposure step is compared with the light transmittance distribution for exposing the resist layer in accordance with the first resist shape in the first exposure step. , Characterized in that it is shifted positions width shorter length of the cell it is possible to provide a manufacturing method of a microlens. Compared with the case where exposure is performed without changing the light transmittance distribution by shifting the light transmittance distribution by a length shorter than the width of the unit cell in the first exposure step and the second exposure step. Thus, the light transmittance distribution can be set finely. By making the light transmittance distribution fine, the change in the amount of light on the resist layer can be made close to a continuous one, and a smooth surface can be formed. In addition, the second resist shape having an accurate depth distribution can be stably formed in a portion corresponding to the vicinity of the outer periphery of the microlens. By accurately forming a portion corresponding to the vicinity of the outer periphery of the microlens, incident light can be advanced in a predetermined direction with high efficiency, and a microlens having high performance can be formed. Thereby, it is possible to avoid the formation of a step shape due to the distribution in which the light transmittance changes stepwise, and the resist shape can be formed accurately.

In a preferred embodiment of the present invention, in the first exposure step, the resist layer is exposed using the first gray scale mask, and in the second exposure step, the first gray scale mask has a light transmittance. It is desirable to expose the resist layer using a second gray scale mask whose distribution is shifted by a length shorter than the width of the unit cell. Thereby, the resist layer can be exposed with a plurality of patterns in which the distribution of light transmittance is shifted.

Further, a preferred embodiment of the present invention includes a gray scale mask moving step for moving the gray scale mask used in the first exposure step. In the second exposure step, the gray scale moved in the gray scale mask moving step is included. It is desirable to expose the resist layer using a scale mask. For example, the gray scale mask can be moved so as to shift the center position of the light transmittance distribution region in which the light transmittance is distributed. By moving the gray scale mask, the resist layer can be exposed with a plurality of patterns in which the distribution of light transmittance is shifted. Further, by making it possible to perform multiple exposures with a single gray scale mask, the number of gray scale masks to be used can be reduced, and the number of steps for replacing the gray scale mask can be reduced. Thereby, the exposure of the resist layer by a plurality of patterns in which the distribution of light transmittance is shifted can be performed at low cost.

Furthermore, according to the present invention, it is possible to provide a microlens that is manufactured using the gray scale mask. The exposure using the gray scale mask can avoid the formation of a step shape and can accurately form a resist shape.
Thereby, it is possible to obtain a microlens that is formed with high accuracy and can accurately control the traveling direction of light.

Furthermore, according to the present invention, it is possible to provide a microlens characterized by being manufactured by the above-described microlens manufacturing method. Thereby, it is possible to obtain a microlens that is formed with high accuracy and can accurately control the traveling direction of light.

Furthermore, according to the present invention, it is possible to provide a spatial light modulation device including the above microlens. By providing the above microlens, it is possible to efficiently use light by the microlens having an accurate shape. Accordingly, it is possible to obtain a spatial light modulation device that can efficiently use light and obtain a high-efficiency, bright, and high-contrast image.

Furthermore, according to the present invention, it is possible to provide a projector including the spatial light modulation device described above. By using the spatial light modulation device, a projector capable of displaying a high-efficiency, bright and high-contrast image can be obtained.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 illustrates a gray scale mask 20 according to a first embodiment of the present invention, and shows a configuration of a reduction projection exposure apparatus 10 using the gray scale mask 20. The reduction projection exposure apparatus 10 reduces the light from the gray scale mask 20 and exposes the material substrate 17. The gray scale mask 20 has a light transmittance distribution determined to expose the resist layer with a predetermined pattern. The gray scale mask 20 is disposed on the optical axis AX of the optical system of the reduction projection exposure apparatus 10 and between the light source 11 and the projection lens 13. The light from the light source 11 passes through the gray scale mask 20 and then enters the projection lens 13 having a reduced magnification. The light from the projection lens 13 is incident on the material substrate 17 placed on the stage 15. The reduced projection exposure apparatus 10 is, for example, a g-line stepper that uses g-line that is light having a wavelength of 435 nm.

FIG. 2 illustrates the configuration of the gray scale mask 20. Here, the gray scale mask 20 for forming a single microlens will be described. When forming a microlens array in which a plurality of microlenses are arranged in an array, a grayscale mask 20 shown in FIG. 2 arranged in an array can be used. The gray scale mask 20 has a square light transmittance distribution region having a side length d of 70 μm. For example, when the reduced projection exposure apparatus 10 performs reduction exposure of 1/5, a microlens having a side of 14 μm can be formed by the gray scale mask 20 having a side length d of 70 μm.

The gray scale mask 20 is configured by arranging a plurality of unit cells 21 having a square shape with a side length of 2.5 μm in an array. The plurality of unit cells 21 each have a light transmittance corresponding to a desired resist shape. By arranging the unit cells 21 each having a light transmittance set in an array, a resist shape having a three-dimensional microstructure can be formed. One gray scale mask 20 has 784 (= 28 × 28) unit cells 21. For example, the gray scale mask 20 can set the light transmittance for each of the 24 equally divided areas on the square diagonal line DL included in the light transmittance distribution region.

Each unit cell 21 has an opening and a light shielding part (not shown). The opening allows light from the light source 11 (see FIG. 1) of the reduction projection exposure apparatus 10 to pass therethrough. The opening is constituted by a minute cell that transmits light. The light shielding unit blocks light from the light source 11. The shading part
It is composed of minute cells that block light. The light transmittance of the unit cell 21 is determined by the area aperture ratio. The area opening ratio is a ratio of the area of the opening to the unit cell 21.

3 and 4 illustrate the shape of a microlens formed using the gray scale mask of the present invention. The microlens has a side length m shown in FIG.
It is formed on m square areas. The graph shown in FIG. 4 represents the curved surface of the microlens in the xyxy ′ cross section of FIG. The microlens has a height of 6 μm from the apex to the bottom in the xyxy ′ cross section.

FIG. 5 shows an example of the γ characteristic. The γ characteristic indicates the relationship between the area aperture ratio OR and the depth of the resist shape formed in the resist layer by exposure. Here, the depth of the resist shape is a value that increases as it approaches the surface on the light source 11 side, assuming that the position farthest from the surface on the light source 11 side of the resist layer, in other words, the position corresponding to the vertex of the microlens is zero. It is said. The depth of resist shape is determined by laser microscope or atomic force microscope (Atomic).
Force Microscope, interferometric optical measuring instrument, Scanning Electron Microsc
ope). The γ characteristic is obtained by plotting the depth of the resist shape when the area aperture ratio OR is set for each value. Here, an example will be described in which a positive resist AZP4903 manufactured by Clariant Japan is used as the resist material. In the positive resist, the exposed portion is removed by development. The depth of the resist shape is shallower as the area aperture ratio OR is larger, and the resist pattern is deeper as the area aperture ratio OR is smaller.

In order to form a resist having an accurate height corresponding to the change in the area aperture ratio OR, a range in which the γ characteristic shows a linear change according to the change in the area aperture ratio OR, for example, 10% to 50%.
It is desirable to take gradation at the area aperture ratio OR. Further, it is desirable to select a resist material that exhibits a linear change in γ characteristics. The resist material selected in the present embodiment is one that obtains a resist depth of 6 μm by an area aperture ratio OR of 10% to 50% width. By taking gradations in a range where the γ characteristic shows a linear change, it is possible to accurately control the resist depth and form a highly accurate microlens.

FIG. 6 illustrates the first gray scale mask 70 for exposing the resist layer in accordance with the first resist shape. The gray scale mask 70 is a first gray scale mask used in the first exposure process. First grayscale mask 70
Has the same configuration as that of the gray scale mask 20 of the present invention described with reference to FIG. Here, the light transmittance distribution in the gray scale mask 70 is schematically represented by the openings 71. The larger the opening 71, the higher the light transmittance. The first gray scale mask 70 has a light transmittance distribution that has the highest light transmittance at the center position and becomes lower as the distance from the center position increases. Thus, the first gray scale mask 70 has the same light transmittance distribution as that of the conventional gray scale mask for forming the microlens.

FIG. 7 shows a comparison between the resist shape S1 formed using only the first grayscale mask 70 and the designed resist shape S0. In the first gray scale mask 70, similarly to the gray scale mask 20 of the present invention, the light transmittance is set for each area equally divided into 24 on the diagonal line DL (see FIG. 2). Thus, the first gray scale mask 70
The light transmittance is distributed so as to change stepwise in the two-dimensional direction. Therefore, the resist shape S1 having a step shape may be formed with respect to the resist shape S0 having a smooth surface. Since the microlens is required to have an accurate shape in order to perform functions such as light refraction, it is desirable to avoid the formation of a step shape that is not in the design.

FIG. 8 illustrates the resist shape S2 obtained by heating the resist layer on which the resist shape S1 is formed. It is considered possible to obtain a resist shape S2 having a smoothed step shape by performing a heat treatment on the resist layer on which the resist shape S1 is formed. However, the resist shape S2 may be greatly different from the designed resist shape S0 due to the influence of heating up to the depth and curvature itself.

FIG. 9 shows reactive ion etching (Reac) on the resist layer in which the resist shape S1 is formed.
tive Ion Etching. Hereinafter, it is referred to as “RIE” as appropriate. The resist shape S3 obtained by applying () will be described. In RIE, ions generated from plasma are accelerated and bombarded on an object to be etched. In this case, it is only possible to round the corners of the step shape, and it is difficult to obtain a smooth surface.

FIG. 10 explains the second gray scale mask 20 which is the gray scale mask of the present invention. The first transmitted light amount distribution LD of the first gray scale mask 70 is shown in FIG.
The second transmitted light amount distribution LD2 of the first and second gray scale masks 20 is compared. The total light amount distribution LD3 includes the first transmitted light amount distribution LD1 and the second transmitted light amount distribution LD.
2 is the total. Each light quantity distribution LD1, LD2, LD3 is shown by taking the position on the resist when the vertical axis represents the light quantity of an arbitrary unit and the horizontal axis represents the center position of the resist shape.

The first transmitted light amount distribution LD1 has a maximum light amount at the center position of the region forming the resist shape, and is set to be substantially concentric. The center position of the first resist shape formed by the first gray scale mask 70 coincides with the center position of the region for forming the resist shape.
In the second transmitted light amount distribution LD2 shown in FIG. 10, the right side of the center position of the region where the resist shape is formed coincides with the first transmitted light amount distribution LD1 shifted to the right by the distance t. In the second transmitted light amount distribution LD2, the left side of the center position of the region where the resist shape is formed coincides with the first transmitted light amount distribution LD1 shifted to the left by the distance t.
As described above, the second transmitted light amount distribution LD2 is obtained by shifting the first transmitted light amount distribution LD1 as it is in the direction away from the center position of the region where the resist shape is formed. The second gray scale mask 20 is the first gray point except for the point where the light transmittance distribution is shifted.
The gray scale mask 70 is formed in the same manner.

The distance t is shorter than the width of the unit cell 21 and corresponds to approximately half the width of the unit cell 21. By shifting the light transmittance distribution of the second gray scale mask 20 by a distance t corresponding to approximately half the width of the unit cell 21, the transmitted light amount distribution LD 2 of any gray scale mask 20, 70, It becomes possible to make the pitch of the total light quantity distribution LD3 finer than LD1. By making the pitch of the total light amount distribution LD3 finer, it becomes possible to make the change in the light amount on the resist layer more continuous. By using the second gray scale mask 20 in which the distribution of the light transmittance of the first gray scale mask 70 is shifted in the direction away from the center position, the change in the amount of light is more continuous in the two-dimensional direction on the resist layer. It can be a typical one.

FIG. 11 compares the second resist shape S4 formed by exposure using the second gray scale mask 20 with the designed resist shape S0. By making the change in the amount of light on the resist layer more continuous, the resist shape S1 (see FIG. 7).
2), the second resist shape S4 having a smoothed step shape can be formed. In addition, the second resist shape S4 can be stably formed with an accurate depth distribution in a portion corresponding to the vicinity of the outer periphery of the microlens as compared with the resist shape S1. By accurately forming a portion corresponding to the vicinity of the outer periphery of the microlens, incident light can be advanced in a predetermined direction with high efficiency, and a microlens having high performance can be formed. As described above, the exposure using the second gray scale mask 20 makes it possible to obtain a resist shape S4 having a smooth surface with few steps and close to the desired resist shape S0. Thereby, it is possible to avoid the formation of a step shape by distributing the light transmittance so as to change stepwise,
There is an effect that the resist shape can be accurately formed.

The gray scale mask 20 is first formed by forming a light shielding film on a transparent substrate that is a parallel plate. As the transparent substrate, for example, a quartz substrate can be used. The gray scale mask 20 of this embodiment forms a light shielding film using chromium which is a light shielding member.
Then, the opening 71 is formed in the transparent substrate on which the light shielding film is formed by electron beam (EB) drawing or the like. A portion of the unit cell 21 other than the portion where the opening 71 is formed is a light shielding portion.

12 and 13 show a procedure for manufacturing a microlens using the gray scale mask 20 of this embodiment. First, in step a shown in FIG. 12, a resist layer 102 is formed on the substrate 101. The resist layer 102 is formed by applying a resist material on the substrate 101 and further pre-baking. Next, in step b, the resist layer 102 is exposed through the first gray scale mask 70 using the g-line stepper which is the reduction projection exposure apparatus 10 shown in FIG. The resist layer 102 is exposed to light L that has passed through the gray scale mask 20 and has been reduced to approximately one fifth. Step b is a first exposure step in which exposure is performed using the first gray scale mask 70 in which the light transmittance distribution is determined according to the first resist shape S5. In step b, an exposure region 103 having a first resist shape S5 is formed.

After the first exposure step, the first gray scale mask 70 is removed, and the second gray scale mask 20 is attached to the reduced projection exposure apparatus 10. In step c, the reduction projection exposure apparatus 1
0 is used to expose the resist layer 102 through the second gray scale mask 20.
Step c uses the resist layer 102 exposed according to the first resist shape S1, and the second step
This is a second exposure step of exposing the resist layer 102 using the second gray scale mask 20 in which the light transmittance distribution is determined so as to form the resist shape S2. According to step c
An exposure region 103 having a second resist shape S4 having a smooth surface with fewer steps than the first resist shape S1 is formed.

In the case where both the first gray scale mask 70 and the second gray scale mask 20 have the same light transmittance as that of a conventionally used single mask, either the first exposure process or the second exposure process is used. However, it is desirable that the exposure time be approximately half that of the conventional case. Furthermore, when both the first exposure step and the second exposure step have the same exposure time as when a conventional single mask is used, the light transmittance of the first gray scale mask 70, the second gray It is desirable that all of the light transmittances of the scale mask 20 be approximately half that of the conventional mask. Thereby, it is possible to perform exposure with the same amount of light as when a single mask is used.

In step d shown in FIG. 13, the second resist shape S4 is formed in the resist layer 102 by developing the resist layer 102 after the second exposure step with a developer. The resist layer 102 after development is further cured by post-baking. In this way, a desired resist shape S4 is formed in the resist layer 102.

Next, in step e, the resist layer 102 and the substrate 101 are etched. By etching the resist layer 102 and the substrate 101, the second resist shape S4 of the resist layer 102 is transferred to the substrate 101. By transferring the second resist shape S4 to the substrate 101, a lens shape 106 substantially the same as the second resist shape S4 is formed on the substrate 101. Step e is a lens shape forming step of forming the lens shape 106 by transferring the second resist shape S4 to the substrate 101 which is another member. Etching is performed by dry etching or a combination of dry etching and wet etching.

Finally, in step f, the microlens 108 is formed by filling the lens-shaped portion between the substrate 101 and the cover glass 107 with a transparent resin material. A microlens array having a plurality of microlenses 108 may be formed by mold transfer using a mold. The mold is manufactured by applying electroless Ni plating to the second resist shape S4 or the lens shape 106. Next, a replica is created by transferring the shape of the mold to another member such as an acrylic resin. Thereby, a lot of replicas can be manufactured easily. Also,
The optical element may be formed by injection molding using the microlens 108 as a mold. The gray scale mask 20 of the present embodiment is not limited to a microlens used as a spatial light modulation element for modulating light according to an image signal, and other optical elements such as a microprism, a communication device, and a medical device. Can be used in the manufacture of

In the production of the microlens, exposure using a gray scale mask other than the first gray scale mask 70 and the second gray scale mask 20 may be performed. It is not restricted to the case where 20 is used. The two gray scale masks 70 and 20 may be further exposed using another gray scale mask whose light transmittance distribution is shifted. Thereby, a resist shape having a smooth surface with fewer step shapes can be formed.

Further, the production of the microlens is not limited to the case where the two gray scale masks 70 and 20 are used, and the single gray scale mask 70 may be moved and used.
In this case, instead of replacing the first gray scale mask 70 with the second gray scale mask 20 prior to step c shown in FIG. 12, the gray scale mask 70 used in the first exposure step is moved. A scale mask moving step is included. In the second exposure step, the resist layer is exposed using the gray scale mask 70 moved in the gray scale mask moving step.

For example, the gray scale mask 70 can be moved so as to shift the center position of the light transmittance distribution region in which the light transmittance is distributed. Here, as shown in FIG. 14, the light transmittance distribution is shifted by a predetermined distance, for example, the distance t described above, in both orthogonal directions. By moving the gray scale mask 70, the resist layer can be exposed with a plurality of patterns in which the distribution of light transmittance is shifted. As shown in FIG. 15, the first transmitted light amount distribution LD1 of the gray scale mask 70 and the second transmitted light amount distribution LD4 obtained by shifting the entire first transmitted light amount distribution LD1 by the distance t are superimposed. Thus, it is possible to obtain a total light amount distribution LD5 having a finer pitch than the first transmitted light amount distribution LD1.

In addition, by making it possible to perform multiple exposures with one gray scale mask 70, it is possible to reduce the number of gray scale masks to be used and the number of steps for replacing gray scale masks. Thus, the resist layer can be exposed with a plurality of patterns whose center positions are shifted from each other by an inexpensive method, and a smooth surface can be formed. Note that the movement of the gray scale mask 70 is not limited to the case where the movement is performed in any of the two orthogonal directions, and only one of the two directions may be used depending on the desired resist shape.

The distance t for moving the gray scale mask 70 is, for example, about 1.25 μm. In the gray scale mask moving step, for example, a reticle alignment mark shifted from a normal reticle alignment mark is provided, and the method of moving the gray scale mask 70 in accordance with this and the coordinate setting of the gray scale mask 70 are changed. A method can be considered.
In addition, the reduction projection exposure apparatus 10 (see FIG. 1) itself may have a function of adjusting the position of the gray scale mask 70.

FIG. 16 shows a schematic configuration of a projector 200 according to Embodiment 2 of the present invention. The projector 200 includes a microlens manufactured using the gray scale mask of the first embodiment. The projector 200 includes a screen 21 provided on the viewer side.
6 is a so-called front projection type projector that supplies light to 6 and observes an image by observing light reflected by a screen 216.

The light source unit 201 supplies light including red light (hereinafter referred to as “R light”), green light (hereinafter referred to as “G light”), and blue light (hereinafter referred to as “B light”). Ultra high pressure mercury lamp. The integrator 204 makes the illuminance distribution of the light from the light source unit 201 uniform. The light whose illuminance distribution is made uniform is polarized light having a specific vibration direction by the polarization conversion element 205, for example, s.
Converted to polarized light. The light converted into the s-polarized light is incident on the R light transmitting dichroic mirror 206R constituting the color separation optical system. The light source unit 201 is not limited to a configuration using an ultrahigh pressure mercury lamp. For example, a solid light emitting element such as a light emitting diode element (LED) may be used.

The R light transmitting dichroic mirror 206R transmits R light and reflects G light and B light. R
The R light transmitted through the light transmitting dichroic mirror 206R enters the reflecting mirror 207.
The reflection mirror 207 bends the optical path of the R light by 90 degrees. The R light whose optical path is bent is incident on the spatial light modulator 210R. The spatial light modulator 210R is a transmissive liquid crystal display device that modulates R light according to an image signal.

The spatial light modulator 210R includes a λ / 2 phase difference plate 223R, a glass plate 224R, a first polarizing plate 2
21R, a liquid crystal panel 220R, and a second polarizing plate 222R. λ / 2 phase difference plate 223
The R and the first polarizing plate 221R are disposed in contact with the light-transmitting glass plate 224R that does not change the polarization direction. Thereby, the problem that the 1st polarizing plate 221R and (lambda) / 2 phase difference plate 223R will be distorted by heat_generation | fever can be avoided. Note that the second polarizing plate 222R may be disposed independently, or may be disposed in contact with the exit surface of the liquid crystal panel 220R or the entrance surface of the cross dichroic prism 212.

The s-polarized light incident on the spatial light modulator 210R is converted into p-polarized light by the λ / 2 phase difference plate 223R. The R light converted into p-polarized light is a glass plate 224R and a first polarizing plate 221R.
And is incident on the liquid crystal panel 220R. The p-polarized light incident on the liquid crystal panel 220R is converted into s-polarized light by modulation according to the image signal. The R light converted into s-polarized light by the modulation of the liquid crystal panel 220R is emitted from the second polarizing plate 222R. In this way, the R light modulated by the spatial light modulator 210R enters the cross dichroic prism 212 that is a color synthesis optical system.

The G light and B light reflected by the R light transmitting dichroic mirror 206R have their optical paths bent 90 degrees. The G light and B light whose optical paths are bent are the B light transmitting dichroic mirror 2.
Incident on 06G. The B light transmitting dichroic mirror 206G reflects G light and transmits B light. The G light reflected by the B light transmitting dichroic mirror 206G is converted into the spatial light modulator 2
Incident to 10G. The spatial light modulator 210G is a transmissive liquid crystal display device that modulates G light according to an image signal. The spatial light modulator 210G includes a liquid crystal panel 220G, a first polarizing plate 2
21G and the second polarizing plate 222G.

The G light incident on the spatial light modulator 210G is converted into s-polarized light. The s-polarized light incident on the spatial light modulator 210G is transmitted through the first polarizing plate 221G as it is, and the liquid crystal panel 2
Incident to 20G. The s-polarized light incident on the liquid crystal panel 220G is converted into p-polarized light by modulation according to the image signal. G converted to p-polarized light by modulation of the liquid crystal panel 220G
Light is emitted from the second polarizing plate 222G. In this way, the G light modulated by the spatial light modulation device 210G enters the cross dichroic prism 212 that is a color synthesis optical system.

The B light transmitted through the B light transmitting dichroic mirror 206G is converted into two relay lenses 208.
Then, the light enters the spatial light modulator 210B via the two reflecting mirrors 207. The spatial light modulator 210B is a transmissive liquid crystal display device that modulates B light according to an image signal. The reason why the B light passes through the relay lens 208 is that the optical path length of the B light is longer than the optical path lengths of the R light and the G light. By using the relay lens 208, the B light transmitted through the B light transmitting dichroic mirror 206G can be directly guided to the spatial light modulator 210B. The spatial light modulator 210B includes a λ / 2 phase difference plate 223B, a glass plate 224B, a first polarizing plate 221B, a liquid crystal panel 220B, and a second polarizing plate 222B. Since the configuration of the spatial light modulation device 210B is the same as the configuration of the spatial light modulation device 210R described above, detailed description thereof is omitted.

The B light incident on the spatial light modulator 210B is converted into s-polarized light. The s-polarized light incident on the spatial light modulator 210B is converted into p-polarized light by the λ / 2 phase difference plate 223B. The B light converted into p-polarized light passes through the glass plate 224B and the first polarizing plate 221B as it is, and enters the liquid crystal panel 220B. The p-polarized light incident on the liquid crystal panel 220B is converted to s-polarized light by modulation according to the image signal. The B light converted into the s-polarized light by the modulation of the liquid crystal panel 220B is emitted from the second polarizing plate 222B. The B light modulated by the spatial light modulator 210B is incident on a cross dichroic prism 212 which is a color synthesis optical system.

The cross dichroic prism 212, which is a color synthesis optical system, is configured by arranging two dichroic films 212a and 212b perpendicularly to an X shape. Dichroic membrane 21
2a reflects B light and transmits G light and R light. The dichroic film 212b reflects R light and transmits G light and B light. In this manner, the cross dichroic prism 212 combines the R light, G light, and B light modulated by the spatial light modulators 210R, 210G, and 210B, respectively. The projection optical system 214 projects the light combined by the cross dichroic prism 212 onto the screen 216. Thereby, a full color image can be displayed on the screen 216.

As described above, the light incident on the cross dichroic prism 212 from the spatial light modulator 210R and the spatial light modulator 210B is set to be s-polarized light. Further, the light incident on the cross dichroic prism 212 from the spatial light modulator 210G is set to be p-polarized light. In this way, by changing the polarization direction of the light incident on the cross dichroic prism 212, the light emitted from each spatial light modulator in the cross dichroic prism 212 can be effectively combined. Dichroic film 212a
212b are usually excellent in the reflection characteristics of s-polarized light. Therefore, the dichroic film 212
The R light and B light reflected by a and 212b are s-polarized light, and the dichroic films 212a, 2b
The G light transmitted through 12b is p-polarized light.

FIG. 17 shows a cross-sectional configuration of a main part of the liquid crystal panel 220R. The projector 200 described with reference to FIG. 16 includes three liquid crystal panels 220R, 220G, and 220B. These three liquid crystal panels 220R, 220G, and 220B differ only in the wavelength region of the light to be modulated,
The basic configuration is the same. For this reason, the liquid crystal panel 220R will be described below as a representative example. The R light from the light source unit 201 enters the liquid crystal panel 220R from the upper side shown in FIG. 17 and is emitted downward, which is the direction of the screen 216. A cover glass 302 is fixed to the incident side of the incident side dustproof glass 300 which is a dustproof glass via an adhesive layer 301. Cover glass 30
A black matrix portion 303a and a counter electrode 304 are formed on the 2 emission side.

On the incident side of the exit side dust-proof glass 308, there is an adhesive layer 307 and an alignment film 3 for aligning liquid crystals.
06c, and TFT substrate 30 having TFT (thin film transistor) and transparent electrode 306a
6 is formed. The incident-side dust-proof glass 300 and the exit-side dust-proof glass 308 are the counter electrode 30.
4 and the TFT substrate 306 are bonded to each other. A liquid crystal layer 305 is sealed between the counter electrode 304 and the TFT substrate 306. The liquid crystal layer 305 is a modulation unit that modulates R light, which is incident light, according to an image signal. On the incident side of the liquid crystal layer 305, a black matrix portion 303a is formed.

The opening 303b allows incident light to enter the liquid crystal layer 305 that is a modulation unit. Opening 303
The R light that passes through b passes through the counter electrode 304, the liquid crystal layer 305, and the TFT substrate 306. R
The polarization state of light is converted by modulation according to the image signal in the liquid crystal layer 305. The opening 303b forms a pixel of a projected image.

On the incident side dust-proof glass 300, a microlens array 310 is formed. The microlens array 310 includes microlenses 311 arranged in an array on a reference plane 300b that is an XY plane. The microlens 311 opens the R light that is incident light to the opening 303b.
Refract in the direction of. The microlens 311 is provided with a curved surface 311a that refracts light facing the incident side. The liquid crystal panel 220R is disposed such that the reference surface 300b on which the microlens 311 is disposed and the Z axis that is the optical axis are substantially orthogonal.

In the configuration shown in FIG. 16, the first polarizing plate 221R and the second polarizing plate 222R are provided separately from the liquid crystal panel 220R. Instead of this, a polarizing plate may be provided between the incident-side dust-proof glass 300 and the counter electrode 304, between the emission-side dust-proof glass 308 and the TFT substrate 306, and the like. Further, the microlens array 310 may be formed on the first polarizing plate 221R.

The microlens 311 can be formed using the gray scale mask of the first embodiment. By using the gray scale mask of the first embodiment, the micro lens 311 is used.
Can form a smooth curved surface 311a with few step shapes. By using the microlens 311 having a small step shape and an accurate shape, unnecessary reflection on the curved surface 311a is reduced, and light can be used efficiently. The projector 200 can display a bright image by enabling efficient use of light in each spatial light modulator. Furthermore, by using the microlens 311 having an accurate shape, the light beam angle can be accurately controlled and a high-contrast image can be displayed. Thereby, a highly efficient, bright and high-contrast image can be obtained. By preventing the concentration of light in the opening 303b with the microlens 311 having an accurate shape, deterioration of the liquid crystal, the alignment film, and the like, and further deterioration of the spatial light modulator can be reduced.

The projector 200 according to the present embodiment is not limited to the configuration using an ultrahigh pressure mercury lamp as the light source unit 201. For example, a solid light emitting element such as a light emitting diode element (LED) may be used. Further, the projector 200 is not limited to a so-called three-plate type projector provided with three transmissive liquid crystal display devices, and for example, a projector provided with one transmissive liquid crystal display device or a projector using a reflective liquid crystal display device. It is also good. Further, the projector is not limited to the front projection type projector 200, and may be a so-called rear projector in which a laser beam is supplied to one surface of the screen and an image is viewed by observing light emitted from the other surface of the screen. . Further, the microlens array 310 is not limited to a projector, and can be applied to a light receiving element such as a CCD camera or a C-MOS sensor.

As described above, the gray scale mask according to the present invention is suitable for manufacturing a microlens that is a minute optical element having a smooth surface.

The figure which shows the structure of the reduction | restoration projection exposure apparatus which uses a gray scale mask. FIG. 3 is a diagram illustrating the configuration of a grayscale mask according to the first embodiment of the invention. The figure explaining the shape of a micro lens. The figure explaining the shape of a micro lens. The figure showing the example of (gamma) characteristic. The figure explaining a 1st gray scale mask. The figure explaining the 1st resist shape. The figure explaining the resist shape obtained by heating a resist layer. The figure explaining the resist shape obtained by giving RIE. The figure explaining the 2nd gray scale mask. The figure explaining the 2nd resist shape formed in a resist layer. The figure explaining the procedure which manufactures a microlens. The figure explaining the procedure which manufactures a microlens. The figure explaining the process of moving a gray scale mask. The figure explaining the transmitted light amount distribution in the case of moving a gray scale mask. FIG. 5 is a diagram illustrating a schematic configuration of a projector according to a second embodiment of the invention. The figure which shows the principal part cross-section structure of a liquid crystal panel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reduction projection exposure apparatus, 11 Light source, 13 Projection lens, 15 Stage, 17 Material substrate, 20 Gray scale mask (2nd gray scale mask), AX Optical axis, 2
1 unit cell, DL diagonal, 23 microcell, 70 first grayscale mask, 7
1 opening, S0, S1, S2, S3 resist shape, S4 second resist shape, 10
1 substrate, 102 resist layer, 103 exposure area, 106 lens shape, 107 cover glass, 108 micro lens, S5 first resist shape, 200 projector,
201 Light Source, 204 Integrator, 205 Polarization Conversion Element, 206R R Light Transmitting Dichroic Mirror, 206GB Light Transmitting Dichroic Mirror, 207 Reflecting Mirror, 208 Relay Lens, 210R, 210G, 210B Spatial Light Modulator, 212 Cross Dichroic Prism, 212a 212b Dichroic film, 214 projection optical system, 216 screen, 220R, 220G, 220B liquid crystal panel, 221R, 2
21G, 221B first polarizing plate, 222R, 222G, 222B second polarizing plate, 223R
223B λ / 2 phase difference plate, 224R, 224B glass plate, 300 incident side dustproof glass,
300b Reference surface, 301 Adhesive layer, 302 Cover glass, 303a Black matrix part, 303b Opening part, 304 Counter electrode, 305 Liquid crystal layer, 306 TFT substrate,
306a Transparent electrode, 306c Alignment film, 307 Adhesive layer, 308 Output side dust-proof glass, 3
10 micro lens array, 311 micro lens, 311a curved surface

Claims (9)

A gray scale mask having a light transmittance distribution determined to expose a resist layer in a predetermined pattern,
Each having a plurality of unit cells in which the light transmittance is set;
A distribution of the light transmittance is determined so as to form a second resist shape using the resist layer exposed according to the first resist shape, and the resist according to the first resist shape. A gray scale mask, wherein the light transmittance distribution is shifted by a length shorter than the width of the unit cell as compared with the case of exposing a layer. 2. The light transmittance distribution is shifted by approximately half the width of the unit cell as compared with the case where the resist layer is exposed according to the first resist shape.
The gray scale mask described in 1. A first exposure step of exposing the resist layer using a grayscale mask having a light transmittance distribution determined according to the first resist shape;
The resist layer is exposed using a gray scale mask whose light transmittance distribution is determined so as to form a second resist shape using the resist layer exposed according to the first resist shape. 2 exposure steps;
A lens shape forming step of forming a lens shape by transferring the second resist shape to another member,
The distribution of the light transmittance is determined by a plurality of unit cells in which the light transmittance is set,
The light transmittance distribution for forming the second resist shape in the second exposure step is for exposing the resist layer in accordance with the first resist shape in the first exposure step. The method of manufacturing a microlens, wherein the microlens is shifted by a length shorter than the width of the unit cell as compared with the light transmittance distribution. In the first exposure step, the resist layer is exposed using a first grayscale mask,
In the second exposure step, the resist layer is formed by using a second gray scale mask in which the light transmittance distribution is shifted by a length shorter than the width of the unit cell. 4. The method for producing a microlens according to claim 3, wherein exposure is performed. A gray scale mask moving step of moving the gray scale mask used in the first exposure step;
4. The method of manufacturing a microlens according to claim 3, wherein, in the second exposure step, the resist layer is exposed using the gray scale mask moved in the gray scale mask moving step. A microlens manufactured using the grayscale mask according to claim 1. A microlens manufactured by the method for manufacturing a microlens according to claim 3.   A spatial light modulator comprising the microlens according to claim 6.   A projector comprising the spatial light modulation device according to claim 8.

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