JPWO2004077533A1 - Exposure equipment - Google Patents

Abstract

A planar light source is imaged on the spatial light modulator by an illumination optical system composed of a telecentric optical system, and this planar light source is imaged on the exposure position of the photosensitive material through the projection optical system to monitor illumination unevenness of the exposure optical system. A correction table N (x, y) for making the uneven illumination of the measured exposure optical system uniform and a correction table M (x, y) for making the illumination unevenness of the monitor optical system uniform are memorized. A sensitivity curve representing the relationship between the depth of the design value obtained by removing the material and the amount of light and a table G (x, y) of the exposure pattern of the photosensitive material are input, and this table G (x, y) is referred to the sensitivity curve. And converted into a sensitivity-corrected exposure pattern table R (x, y) and a control value table S (x, y) = R (x, y) × N (x) corresponding to each pixel of the spatial light modulator. , Y) × M (x, y) Each pixel of the spatial light modulator is controlled by the control value, and the light of each pixel is imaged on the photosensitive material at the exposure position through the projection optical system and exposed.

Description

  The present invention relates to exposure of a photosensitive material such as a resist, exposure to cause a photoreaction used in the production of a micromachine such as a biochip, exposure to deposit a film in a place exposed to light, such as photo-CVD, and exposure to light. The present invention relates to an exposure apparatus that can be used for exposure for etching the area.

In recent years, semiconductor manufacturing has become a means of creating micro structures such as the production of chips that integrate process processes performed in the laboratory, such as cell culture and chemical reactions and their separation and detection, called micromachines and laboratory chips. Photolithographic technology is used.
Although exposure apparatuses tend to become more complex and larger as semiconductors become finer, demand for simple and inexpensive apparatuses that can be used at the laboratory level has increased. A black and white binary exposure technique that does not use a mask using DMD is proposed in Japanese Patent Laid-Open No. 10-112579 and Japanese Patent Laid-Open No. 2001-500628. Further, in order to make the in-plane distribution uniform on the exposure surface except for the non-uniformity due to the position of the exposure light, which is important in the exposure apparatus, Japanese Patent Application Laid-Open No. 2000-40660 discloses a fly eye for making the illumination light uniform outside. A binary exposure method using a lens is disclosed. However, in multi-tone exposure, in order to obtain a desired exposure value, the uniformity of the illumination light must be less than the resolution of the tone, and the required accuracy is remarkably different from that seen by humans such as display devices. Different. Even if the optical illumination light uniformizing means such as a fly-eye lens is sufficient for two-tone black-and-white exposure, the effect of uniforming is not sufficient when the gradation becomes high. For example, when performing multi-gradation exposure with a resolution of 256 gradations, uniformity within an error of 0.4% is required in the in-plane distribution of illumination light. A monochrome two-tone lithography apparatus is disclosed in Japanese Patent Laid-Open No. 2001-135562. Japanese Laid-Open Patent Publication No. 2002-367900 discloses a two-tone exposure apparatus that illuminates a DMD with a parallel light beam and uniformly exposes using a detection signal from a photodetector provided on a dummy optical system. Yes. However, since the detection points are sparse in the exposure, it is difficult to ensure uniformity in order to ensure resolution corresponding to the gradation when performing multi-gradation exposure. When the DMD is illuminated with convergent light or an expanding light, the focal position on the exposure surface is shifted, so that complete parallelism is required. FIG. 15 shows an example of a case where illumination is performed with extreme convergent light. This is a phenomenon that occurs because the DMD is inclined with respect to the illumination optical axis. When the parallelism deteriorates, the exposure resolution does not become constant within the exposure surface. At present, since a light source having a size that cannot be regarded as a point light source typified by a high-pressure mercury lamp is used, it is difficult to achieve perfect parallelism. When laser is used, parallelism is ensured, but since the coherence is high, the pixels of the spatial light modulator form a two-dimensional array, so that the grating generates an interference pattern on the exposure surface and causes noise. It becomes.
An object of the present invention is to solve the above-described problems by using a table of control values for each pixel corrected by taking into account factors such as illumination unevenness of an exposure optical system and sensitivity characteristics of a photosensitive material. It is an object of the present invention to provide a multi-tone exposure apparatus in which each pixel is controlled and the exposure system in the depth direction of the photosensitive material is enhanced.

When performing exposure of the intermediate gradation, it is necessary to ensure uniformity according to the position with an error equal to or less than the resolution of the intermediate gradation. Specifically, in order to realize exposure with 256 gradations, variation due to a difference in position within the exposure surface must be within 0.4%. The factor that must be dealt with in realizing a high-precision halftone is the nonlinearity of the reaction of the sample to be exposed, such as a photosensitive material, to light, such as uneven brightness of the light source and uneven illumination by the optical system. In order to solve this problem, the present invention provides a planar light source, a planar light source, and spatial light modulation in an exposure apparatus that exposes a photosensitive material by controlling each pixel of a spatial light modulator to generate a multi-tone exposure pattern. And an illumination optical means composed of a telecentric optical system that images the planar light source on the spatial light modulator, and a planar light source imaged on the spatial light modulator by the illumination optical means. Projection optical means for forming an image at an exposure position of the material, monitor optical means for measuring an in-plane distribution of light intensity of the exposure optical system at the exposure position of the photosensitive material for each pixel of the spatial light modulator, and the monitor optical Storage means storing a correction table N (x, y) for uniforming the in-plane distribution of light intensity of the exposure optical system measured by the means, and a correction table M (x, y) for uniforming illumination unevenness of the monitor optical system And obtained by removing the photosensitive material A sensitivity curve representing the relationship between the depth of the design value and the amount of light and a table G (x, y) of the pattern that exposes the photosensitive material as the design value are input, and the sensitivity curve is referred to the table G (x, y). And converted into a sensitivity-corrected exposure pattern table R (x, y) and a control value table S (x, y) = R (x, y) × N (x) corresponding to each pixel of the spatial light modulator. , Y) × M (x, y), a control value calculation means, and a spatial light modulator control means for controlling each pixel of the spatial light modulator by the control value obtained by the control value calculation means, The light of each pixel of the spatial light modulator controlled by the spatial light modulator control means is imaged and exposed on a photosensitive material through the projection optical system of the projection optical means.
According to the present invention, since the planar light source is imaged and illuminated on the spatial light modulator, exposure with high resolution can be realized with less focus shift than when the spatial light modulator is illuminated with substantially parallel light. Furthermore, high-accuracy multi-tone exposure is achieved by two processes: conversion to a light amount that obtains the removal depth of the photosensitive material according to the sensitivity characteristics of the photosensitive material used and correction by the position of each pixel that eliminates illumination unevenness. Realized.

FIG. 1 is a schematic view showing a first embodiment of an exposure apparatus according to the present invention.
FIG. 2 is a block diagram showing an embodiment of a planar light source.
FIG. 3 is a block diagram showing another embodiment of the planar light source.
FIG. 4 is a diagram for explaining optical propagation of the rod integrator.
FIG. 5 is a diagram showing an example of a sensitivity curve of a photosensitive material.
FIG. 6 is a diagram showing an example of a designed exposure pattern table G (x, y).
FIG. 7 is a diagram showing an example of a table R (x, y) of sensitivity correction exposure patterns.
FIG. 8 is a diagram showing an example of the correction table N (x, y).
FIG. 9 is a diagram showing an example of the correction table M (x, y).
FIG. 10 is a diagram showing an example of a control value table S (x, y).
FIG. 11 is a schematic view of an exposure apparatus in which a thin film scatterer is applied to a planar light source.
FIG. 12 is a schematic view of an exposure apparatus using a reflective liquid crystal panel.
FIG. 13 is a diagram showing a flow of exposure using DMD.
FIG. 14 is a diagram showing the flow of exposure using a reflective liquid crystal panel.
FIG. 15 is a diagram showing a focal position when the DMD is illuminated with focused light.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of an exposure apparatus according to the present invention. In this embodiment, a digital micromirror device (DMD) is used as a spatial light modulator, and a multi-tone exposure pattern is generated by controlling each pixel (micromirror) arranged two-dimensionally. To be exposed. The configuration of the exposure apparatus includes a planar light source 1, illumination optical means 2, spatial light modulator (DMD) 3, projection optical means 4, monitor optical means 5, and control means 6.
FIG. 2 is a block diagram showing an embodiment of a planar light source. The planar light source 1 has an LED light source arranged so that the optical axes of the plurality of LED lamps 10 are parallel to each other, and condenses the light flux of the LED lamp 10 through the condenser lens 11 to the incident end of the rod integrator 12. Is provided.
In the LED light source, a plurality of LED lamps 10 are arranged on a flat thermally conductive electrode substrate 13 made of, for example, a copper plate, and either the cathode side or the anode side of the LED chip of each LED lamp 10 is mounted. The lead frame is electrically connected to the thermally conductive electrode substrate 13. In order to release heat from the heat conductive electrode substrate 13, the heat conductive electrode substrate 13 is provided with a heat radiating means. As a specific example of the heat dissipating means, as shown in FIG. 2, a Peltier element 14 is arranged on the back surface of the heat conductive electrode substrate 13, and a radiator 15 is provided on the Peltier element 14, and each is thermally coupled to further dissipate heat. The cooler 15 is cooled by a cooling fan 16.
Since the exit end 12 a of the rod integrator 12 is cut obliquely at an angle B, the optical axis is inclined by an angle A determined by the refractive index of the material of the rod integrator 12. In FIG. 1, the DMD 30 and the injection end of the rod integrator 12 are installed so as to satisfy the Sine proof relationship. That is, in this embodiment, an equal-magnification illumination optical system is used. Therefore, if the angle formed by the illumination optical axis and the DMD 30 is C, the angle formed by the exit end of the rod integrator 12 and the illumination optical axis is also C. . With this arrangement, (rod integrator cut angle B) + (offset angle A) + C = 90 degrees.
Such an arrangement of the planar light source 1 can form an image of the planar light source 1 on all the micromirrors of the DMD 30.
FIG. 3 shows another embodiment of the planar light source, and members having the same functions as those in FIG. This flat light source is formed in a spherical surface so that the light of the LED lamp 10 is directed to the incident end of the rod integrator 12 and the incident end of the rod integrator 12 is arranged on the heat conductive electrode substrate 13. It is formed on the convex lens 12b and has the function of condensing the light from the LED lamp 10.
As shown in FIG. 4, the rod integrator 12 is an optical propagating body in which a light beam introduced from the incident end repeats multiple reflections and propagates to the light exit end. Specific examples include a structure in which a clad formed of an optical material having a low refractive index surrounds a core body formed of an optical material having a high refractive index, as in an optical fiber, and is clad in the surrounding air. It is possible to apply a glass rod that can be totally reflected on the surface with the function of, a structure having a core of a plastic rod, a mirror rod that mirrors a surface of glass or plastic with a metal such as aluminum, etc. .
The illumination optical means 2 makes the angle T formed by the optical axis for forming an image on the DMD 30 and the optical axis of the optical system for projecting the light imaged on the DMD 30 twice the tilt angle of the micromirror of the DMD 30. Is set. The illumination optical system is disposed between the DMD 30 and the rod integrator 12, and the planar light source 1 formed at the light exit end of the rod integrator 12 is telecentric including a first convex lens 20, an aperture stop 21, and a second convex lens 22. An image is formed on the DMD 30 through the optical system. The telecentric optical system is installed between the planar light source 1 and the DMD 30 so as to satisfy the Scheinproof relationship.
Thus, by illuminating the planar light source 1 and the DMD 30 with the telecentric optical system that satisfies the Scheinproof relationship, all the micromirrors of the DMD 30 can be illuminated at a predetermined angle, for example, 20 degrees or 24 degrees. There is no focus shift as when illuminated with substantially parallel light. Further, the NA of the illumination light can be easily adjusted by enlarging or reducing the aperture stop.
In this embodiment, a double-sided telecentric optical system is used. At least the DMD side needs to be telecentric. A telecentric optical system with a magnification of 1 was adopted. Of course, if a high-magnification optical system is adopted, the exit end of a small area rod integrator can be imaged on the DMD.
The projection optical means 4 is composed of a double-sided telecentric reduction projection optical system, and controls the micromirrors of the DMD 30 so that light corresponding to the exposure pattern is imaged on the photosensitive material 7 through the projection lens 40 and exposed.
The monitor optical means 5 controls the micromirror of the DMD 30 to form an image of the planar light source 1 for each micromirror, and the reflected planar light source 1 passes through the projection lens 40 and corresponds to the pixel coordinate (x, y). The exposure position (x, y) is imaged, and the in-plane distribution of the light intensity of the exposure optical system is measured. A mounting table for moving the photosensitive material 7 on the substrate to the exposure position is provided. In the measurement of the monitor light, the light of the exposure optical system imaged at the exposure position (x, y) without entering the photosensitive material 7 on the substrate is incident on the diffuser plate 51 through the convex lens 50 and installed behind this. The detected light is detected by the light detector 52 and input to the control means 6.
Illumination unevenness occurs in the optical system. In the case of the exposure optical system, this is because the luminance unevenness of the light source or the light propagation rate is different between the central portion and the peripheral portion of an optical element such as a lens. Also in the case of a monitor optical system, because of the directivity of lenses and detectors, even if the light has the same light intensity, if the monitor position (exposure surface) is different, the detection efficiency will be different. Since it is necessary to perform correction according to the position of the illumination unevenness generated in the exposure optical system and the monitor optical system, the control unit 6 eliminates the illumination unevenness of the exposure optical system, that is, a correction table for making the in-plane distribution of the light intensity uniform. N (x, y), a storage means for storing a correction table M (x, y) for uniforming the illumination unevenness of the monitor optical system, and a table G (x, y) of the exposure pattern of the designed photosensitive material. Conversion to a sensitivity-corrected exposure pattern table R (x, y) with reference to a sensitivity curve representing the relationship between the depth of the design value to be removed after development of the photosensitive material and the amount of light, and corresponding to each pixel of the spatial light modulator Control value calculation means for obtaining the control value table S (x, y) = R (x, y) × N (x, y) × M (x, y), and the control value obtained by the control value calculation means Spatial light modulator control that controls each pixel of the spatial light modulator The control means is configured by a computer that implements software.
A case is assumed in which a mold of this structure is created on a photosensitive material in order to produce a structure having 64 gradation steps designed by using CAD or the like. The design data is designed as a two-dimensional table in which the height L in the Z direction at the position determined by the x and y coordinates is used as an element. This two-dimensional table is used as an exposure pattern including an intermediate gradation. A table G (x, y) of desired values of the depth L from which the photosensitive material is removed is assumed. (X, y) is the coordinates of the position corresponding to the pixel of the spatial light modulator. Photosensitive materials such as resist generally do not react linearly with the amount of light irradiated. Further, as the film thickness increases, the nonlinearity becomes significant due to scattering and absorption. The photosensitive material having a predetermined thickness to be used is irradiated with light while changing the light amount I (w.sec), and a depth L (μ) at which the photosensitive material is removed through a predetermined development process is measured. From this data, a conversion table R (L) corresponding to the light quantity I necessary to obtain a desired removal depth L is created. By referring to the conversion table R (L), the element L of the design value table G (x, y) is converted into a necessary light quantity I. The converted new table R (x, y) is measured. Next, the in-plane distribution of the exposure light is measured with the exposure sample not attached. Only one pixel is turned on, and the light intensity of the exposure optical system is measured with a monitor photodetector. The light intensity is measured by sequentially switching the pixels to be turned on, and a table of in-plane distribution for one screen corresponding to all the pixels is created. The exposure light in-plane distribution table comprehensively reflects light source brightness unevenness, illumination optical system illumination unevenness, spatial light modulator illumination unevenness, projection optical system illumination unevenness, etc., and is uniform for each pixel. is not. A correction table N (x, y) is created so that the in-plane distribution is uniform. The value for each pixel in the correction table N (x, y) is a value obtained by multiplying the inverse of the light intensity by a proportional multiplier k. That is, normalize to k. A product is obtained for each element of the control value table and the correction table N (x, y) to obtain a new control value table S (x, y).
S (x, y) = R (x, y) × N (x, y)
Here, x represents multiplication for each element.
Up to this point, uneven illumination due to the position of the monitor system remains uncorrected. If the illumination unevenness of the monitor system is large and cannot be ignored, a resist film or the like is exposed, and a table M (x, y) for correcting the illumination unevenness of the monitor system is created by a method of measuring the step after development. When the apparatus is assembled, a correction table N (x, y) is created using a monitor system, and a resist film is exposed using the correction table to measure unevenness in detection of the monitor system from the step measurement. A table M (x, y) for correcting this uniformly is created. The value for each pixel in the correction table is the reciprocal of the measurement step. Once the non-uniformity of detection in the monitor system is measured, this non-uniformity does not change and is stored as a device constant.
However, in this embodiment, the exposure area is several millimeters in size, and the diameter of the lens 50 used in the monitor system is as large as several centimeters, so that only paraxial rays are used, and scattering is performed immediately before the detector. The elements of M (x, y) depending on the position are all 1 within the required error range due to the effect of placing the body. In this case, it can be omitted.
It is possible to correct a fluctuation factor that frequently fluctuates due to replacement of the light source or the like, and to use a table N (x, y) that uniformly corrects the monitor light intensity.
S (x, y) = R (x, y) × M (x, y)
Here, x represents multiplication for each element. After the correction by the photosensitive material and the correction by the position are completed, the control means controls each pixel of the spatial light modulator by the control value S (x, y), and Exposure is performed by forming image light on a pixel on a photosensitive material through a projection optical system.
FIG. 5 shows an example of the sensitivity curve of the photosensitive material. FIG. 6 shows an example of an exposure pattern table G (x, y) designed. FIG. 7 shows an example of a sensitivity correction exposure pattern table R (x, y). FIG. 8 shows an example of the correction table N (x, y). FIG. 9 shows an example of the correction table M (x, y). FIG. 10 shows an example of the control value table S (x, y).
Another embodiment of the present invention will be described.
FIG. 11 is a schematic view of an exposure apparatus in which a thin film scatterer is applied to a planar light source. In this embodiment, a DMD 30 is used as a spatial light modulator, and each micromirror is controlled to generate a multi-tone exposure pattern to expose the photosensitive material 7. The configuration of the exposure apparatus includes a planar light source 1, illumination optical means 2, spatial light modulator (DMD) 3, total reflection prism 8, projection optical means 4, monitor optical means 5, and control means (not shown). Here, the functions of the monitor optical means 5 and the control means are the same as those of the embodiment shown in FIG.
The optical axis of the illumination optical system and the optical axis of the projection optical system are arranged orthogonally, and the DMD 30 is installed on the optical axis of the projection optical system. A total reflection prism 8 is disposed at a position where the optical axis of the illumination optical system and the optical axis of the projection optical system intersect, and the planar light source 1 is totally reflected by the total reflection prism 8 to form an image on the DMD 30. The imaged planar light source 1 transmits the total reflection prism 8 under the control of the DMD 30 and forms an image on the photosensitive material 7 through the projection optical system 4 for exposure. Therefore, the total reflection prism 8 is inclined so as to totally reflect the planar light source 1 at an angle equal to 20 degrees or 24 degrees to the DMD 30. The light source is made into a planar light source 1 by a thin film scatterer 17, and this planar light source 1 is totally reflected by a total reflection prism or mirror 18 in a direction coinciding with the optical axis of the illumination optical system and is incident on the illumination optical system. The total reflection prism or mirror is inclined so that the incident angle to the total reflection prism or mirror of the planar light source 1 by the thin film scatterer 17 is equal to 20 degrees or 24 degrees. The DMD 30 and the planar light source 1 satisfy the Scheinproof relationship.
FIG. 12 is a schematic view of an exposure apparatus using a reflective liquid crystal panel. In this embodiment, a reflective liquid crystal panel 31 is used as the spatial light modulator 3, and the photosensitive material 7 is exposed by generating a multi-tone exposure pattern by controlling each of the two-dimensionally arranged liquid crystal cells. . The configuration of the exposure apparatus is a flat light source 1, illumination optical means 2, spatial light modulator (reflective liquid crystal panel) 3, PBS (Polarized Beam Splitter) 9, projection optical means 4, monitor optical means 5, and control means (not shown). ). Here, the functions of the projection optical means 4, the monitor optical means 5, and the control means are the same as those of the embodiment shown in FIG.
In this embodiment, the planar light source 1 that has passed through the illumination optical means 2 is deflected by the PBS 9 to form an image on the reflective liquid crystal panel 31, and the voltage applied to each liquid crystal cell is adjusted to reflect the reflected light from each liquid crystal cell. The light intensity is controlled, and this light is imaged on the photosensitive material 7 through the PBS 9 and the projection optical means 4 and exposed.
The planar light source 1 uses the structure shown in FIGS. 2 and 3, and the light exit end 12 a of the rod integrator 12 is cut into a plane perpendicular to the optical axis of the rod integrator 12.
The illumination optical means 2 arranges the optical axis of the illumination optical system and the optical axis of the projection optical system orthogonal to each other, and installs the reflective liquid crystal panel 31 on the optical axis of the projection optical system. A PBS 9 is arranged at a position where the optical axis of the illumination optical system and the optical axis of the projection optical system intersect, and the S wave from the planar light source 1 is reflected by the PBS 9 and imaged on the reflective liquid crystal panel 31. The P wave passes through the PBS 9 and is absorbed (not shown). The imaged planar light source 1 passes through the PBS 9 by the polarization control of the liquid crystal cell, forms an image on the photosensitive material 7 through the projection optical system, and exposes it. Therefore, the polarization separation surface of the PBS 9 is inclined 45 degrees with respect to the planar light source 1.
The reflective liquid crystal panel 31 is a liquid crystal cell in which individual pixels are minute, and the polarization direction of light reflected by an applied voltage (analog amount) is controlled. The reflective liquid crystal panel 31 and the PBS 9 are combined and used for spatial light modulation and intensity modulation. The reflective liquid crystal panel 31 includes, for example, 1365 × 1024 liquid crystal cells having a size of 13.5 μ × 13.5 μ.
In the above optical system, the polarization angle of the reflected light from the liquid crystal cell is controlled by an analog voltage applied to the liquid crystal cell. The light intensity is controlled by the light branching action of the PBS 9 that is reflected by the controlled polarization angle of the light. Specifically, when no voltage is applied to the liquid crystal cell, the light from the planar light source 1 passes through the PBS 9 and exposes the photosensitive material with the strongest light intensity. The light from the planar light source 1 when the rated maximum voltage is applied to the liquid crystal cell is reflected by the PBS 9 and does not expose the photosensitive material 7. When an intermediate voltage equal to or lower than the rated maximum voltage is applied to the liquid crystal cell, the photosensitive material 7 is exposed with a light intensity that is inversely proportional to the applied voltage.
Next, the operation of the control means will be described. FIG. 13 shows the flow of exposure using DMD. An illumination unevenness correction table N _D (x, y) of the exposure optical system and a table M (x, y) for correcting the illumination unevenness of the monitor optical system are stored in advance. Enter the sensitivity curve of the photosensitive material. A designed exposure pattern table G (x, y) is input. The exposure pattern table G (x, y) is converted into a photosensitive correction exposure pattern table R (x, y) with reference to the sensitivity curve of the photosensitive material. A control value table S (x, y) corresponding to each micromirror of the DMD 30 is obtained by the following equation.
S (x, y) = R (x, y) × N _D (x, y) × M (x, y)
The DMD 30 is controlled by the intensity adjustment method or the time adjustment method using the control value table S (x, y).
The intensity adjustment method performs PWM control with the control value table S (x, y) while keeping the micromirror tilt time constant for all micromirrors, and repeats fine switching within the micromirror tilt time. The integrated light intensity within the tilt time of the micromirror is controlled.
In the time adjustment method, the on-time is controlled by the control value table S (x, y) and the light intensity is controlled by utilizing the proportional relationship between the tilt time of the micromirror and the exposure amount.
Next, the operation of the control means of the exposure apparatus using the reflective liquid crystal panel will be described. FIG. 14 shows the flow of exposure using a reflective liquid crystal panel. An illumination unevenness correction table N _L (x, y) of the exposure optical system and an illumination unevenness correction table M (x, y) of the monitor optical system are stored in advance. Enter the sensitivity curve of the photosensitive material. A designed exposure pattern table G (x, y) is input. The exposure pattern table G (x, y) is converted into a photosensitive correction exposure pattern table R (x, y) with reference to the sensitivity curve of the photosensitive material. A control value table S (x, y) corresponding to each liquid crystal cell is obtained by the following equation.
S (x, y) = R (x, y) × N _L (x, y) × M (x, y)
The reflective liquid crystal panel is controlled by the intensity adjustment method or the time adjustment method using the control value table S (x, y).
The intensity adjustment method utilizes the fact that the voltage applied to the liquid crystal cell and the light intensity are in a proportional relationship, and refers to the control value table S (x, y) to control the applied voltage for each liquid crystal cell, and Control strength.
In the time adjustment method, the on-time is controlled by the control value table S (x, y) while the applied voltage for each liquid crystal cell is kept constant in all the liquid crystal cells, and the light intensity for each liquid crystal cell is controlled. .
In the above-described embodiment, the illumination unevenness correction of the monitor optical system is performed. However, the control value S (x, y) = R (x, y) × N (x, y) obtained by performing only the light intensity correction may be used. .
In this embodiment, the sensitivity correction of the photosensitive material is used as R (x, y). However, the correction of the film formation efficiency by the light amount or the correction of the etching efficiency by the light amount can be similarly performed.
According to this embodiment, the following effects are produced.
1. By controlling each micromirror with pulse width modulation (PWM) corresponding to the control value for each micromirror of the DMD, the exposure amount of the control value can be obtained for each pixel.
2. By controlling each micromirror with an ON time corresponding to the control value for each micromirror of the DMD, an exposure amount of the control value can be obtained for each pixel. It does not depend on special hardware (PWM device) and can be controlled with high resolution.
3. Since the telecentric illumination optical system is installed so that the planar light source and the DMD satisfy the Scheinproof relationship, all the DMD micromirrors can be used with respect to the DMD that is installed inclined with respect to the illumination optical axis. On the other hand, a planar light source can be imaged at a predetermined angle.
4). By controlling each liquid crystal cell with an applied voltage corresponding to the control value for each liquid crystal cell of the reflective liquid crystal panel, an exposure amount of the control value can be obtained for each pixel.
5). By controlling each liquid crystal cell by applying a predetermined voltage for a time corresponding to the control value for each liquid crystal cell of the reflective liquid crystal panel, it is possible to obtain an exposure amount of the control value for each pixel and at a high resolution. Easy to control.
6). By using a planar light source as an LED light source, there is no fluctuation in the light emission position as compared with a discharge lamp, and it has a long life and does not require replacement.
7). By using an illuminated thin-film scatterer as the planar light source, the planar light source can be obtained at a lower cost than the rod integrator.
8). By using a flat light source as a light exit end cut obliquely to a rod integrator installed with an offset angle with respect to the illumination optical axis, the Scheimpflug relationship is satisfied and the DMD is tilted with respect to the optical axis. A planar light source for imaging can be made. Moreover, light can be used efficiently by installing with an offset angle.

An LED lamp with no light emission position variation is used as a light source, a flat light source is generated from the light source, and the flat light source and the spatial light modulator are telecentrically imaged on the spatial light modulator so that the Schein-proof relationship is satisfied. Therefore, there is little focus shift on the exposure surface, and the exposure pattern on the spatial light modulator can be transferred in a high resolution state or a predetermined reaction can be caused.
In the case of exposing the photosensitive material to multiple gradations, the exposure characteristic is corrected so as to be a design value for removing the photosensitive material in consideration of the sensitivity characteristic of the photosensitive material to be used, and uneven exposure is caused. A structure with a multi-tone depth structure can be created on the photosensitive material with high accuracy by performing correction according to the position for each pixel so that the exposure amount can be precisely controlled even under bright illumination. Can do.

  The present invention relates to exposure of a photosensitive material such as a resist, exposure to cause a photoreaction used in the production of a micromachine such as a biochip, exposure to deposit a film in a place exposed to light, such as photo-CVD, and exposure to light. The present invention relates to an exposure apparatus that can be used for exposure for etching the area.

In recent years, as a means of making micro structures such as semiconductor manufacturing, manufacturing of chips that integrate processing processes performed in laboratories such as cell culture, chemical reaction and separation detection called micromachines and laboratory chips Photolithographic technology is used.
Although exposure apparatuses tend to become more complex and larger as semiconductors become finer, demand for simple and inexpensive apparatuses that can be used at the laboratory level has increased. Patent Document 1 and Patent Document 2 propose a black and white binary exposure technique that does not use a mask using DMD. Further, in order to make the in-plane distribution uniform on the exposure surface except for the non-uniformity due to the position of the exposure light, which is important in the exposure apparatus, Patent Document 3 uses a fly-eye lens to make the illumination light uniform outside. A binary exposure method is disclosed. However, in multi-tone exposure, in order to obtain a desired exposure value, the uniformity of the illumination light must be less than the resolution of the tone, and the required accuracy is remarkably different from that seen by humans such as display devices. Different. Even if the optical illumination light uniformizing means such as a fly-eye lens is sufficient for two-tone black-and-white exposure, the effect of uniforming is not sufficient when the gradation becomes high. For example, when performing multi-gradation exposure with a resolution of 256 gradations, uniformity within an error of 0.4% is required in the in-plane distribution of illumination light. A black-and-white two-tone lithography apparatus is disclosed in Patent Document 4. Patent Document 5 discloses a two-tone exposure apparatus that illuminates a DMD with a parallel light beam and uniformly exposes using a detection signal from a photodetector provided on a dummy optical system. However, since the detection points are sparse in the exposure, it is difficult to ensure uniformity in order to ensure resolution corresponding to the gradation when performing multi-gradation exposure. When the DMD is illuminated with convergent light or an expanding light, the focal position on the exposure surface is shifted, so that complete parallelism is required. FIG. 15 shows an example of a case where illumination is performed with extreme convergent light. This is a phenomenon that occurs because the DMD is inclined with respect to the illumination optical axis. When the parallelism deteriorates, the exposure resolution does not become constant within the exposure surface. At present, since a light source having a size that cannot be regarded as a point light source typified by a high-pressure mercury lamp is used, it is difficult to achieve perfect parallelism. When laser is used, parallelism is ensured, but since the coherence is high, the pixels of the spatial light modulator form a two-dimensional array, so that the grating generates an interference pattern on the exposure surface and causes noise. It becomes.

JP 10-112579 A JP-T-2001-500628 JP 2000-40660 A Japanese Patent Laid-Open No. 2001-135562 JP 2002-367900 A

  An object of the present invention is to solve the above-described problems by using a table of control values for each pixel corrected by taking into account factors such as illumination unevenness of an exposure optical system and sensitivity characteristics of a photosensitive material. It is an object of the present invention to provide a multi-tone exposure apparatus in which each pixel is controlled to improve exposure accuracy in the depth direction of the photosensitive material.

  When performing exposure of the intermediate gradation, it is necessary to ensure uniformity according to the position with an error equal to or less than the resolution of the intermediate gradation. Specifically, in order to realize exposure with 256 gradations, the variation due to the difference in position within the exposure surface must be within 0.4%. The factor that must be dealt with in realizing a high-precision halftone is the nonlinearity of the reaction of the sample to be exposed, such as a photosensitive material, to light, such as uneven brightness of the light source and uneven illumination by the optical system.

In order to solve this, the invention of claim 1 forms an image of a light source on a spatial light modulator, controls each pixel of the spatial light modulator to generate a multi-tone exposure pattern, and exposes the photosensitive material. In the exposure apparatus, the monitor optical means for measuring the in-plane distribution of the light intensity of the exposure optical system at the exposure position of the photosensitive material for each pixel of the spatial light modulator, and the exposure optical system measured by the monitor optical means The storage means storing the correction table N (x, y) for uniforming the in-plane distribution of light intensity, the correction table M (x, y) for uniforming the illumination unevenness of the monitor optical system, and the photosensitive material are removed. A sensitivity curve representing the relationship between the depth of the designed value and the amount of light to be obtained and a table G (x, y) of the exposure pattern of the photosensitive material are input, and the sensitivity of the table G (x, y) is referred to the sensitivity curve. It is converted into a corrected exposure pattern table R (x, y), and a pair of pixels for each of the spatial light modulators. A control value for obtaining a table S (x, y) = R (x, y) × N (x, y) × M (x, y) of control values in which the corresponding illumination unevenness is made uniform and the linearity of the photosensitive material is corrected And a spatial light modulator control means for controlling each pixel of the spatial light modulator by the control value obtained by the control value calculation means.
Preferably, the spatial light modulator is constituted by a DMD or a reflective liquid crystal panel.

According to a fourth aspect of the present invention, in the first aspect, the spatial light modulator configured by the DMD, the planar light source set obliquely with respect to the illumination optical axis, and the planar light source and the DMD are disposed. An illumination optical unit configured to form an image on the DMD so that the planar light source satisfies the Schein-proof relationship, and a plane imaged on the DMD by the illumination optical unit. Projection optical means for forming an image of the light source at the exposure position of the photosensitive material, and controlling each micromirror of the DMD.
Preferably, the planar light source is composed of a light exit end cut obliquely of a rod integrator installed with an offset angle with respect to the illumination optical axis.

  According to the first aspect of the present invention, there are two processes, namely, conversion to a light quantity for obtaining the removal depth of the photosensitive material of the designed value depending on the sensitivity characteristic of the photosensitive material to be used, and correction by the position for each pixel excluding illumination unevenness. High-precision multi-tone exposure is realized.

  According to the invention of claim 3, since the planar light source is imaged and illuminated on the spatial light modulator composed of DMD so as to satisfy the Scheinproof relationship with the telecentric optical system, the spatial light modulation is performed with substantially parallel light. Compared to the case of illuminating the instrument, exposure with high resolution can be realized with less focus shift.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of an exposure apparatus according to the present invention. In this embodiment, a digital micromirror device (DMD) is used as a spatial light modulator, and a multi-tone exposure pattern is generated by controlling each pixel (micromirror) arranged two-dimensionally. To be exposed. The configuration of the exposure apparatus includes a planar light source 1, illumination optical means 2, spatial light modulator (DMD) 3, projection optical means 4, monitor optical means 5, and control means 6.

  FIG. 2 is a block diagram showing an embodiment of a planar light source. The planar light source 1 has an LED light source arranged so that the optical axes of the plurality of LED lamps 10 are parallel to each other, and condenses the light flux of the LED lamp 10 through the condenser lens 11 to the incident end of the rod integrator 12. Is provided.

  In the LED light source, a plurality of LED lamps 10 are arranged on a flat thermally conductive electrode substrate 13 made of, for example, a copper plate, and either the cathode side or the anode side of the LED chip of each LED lamp 10 is mounted. The lead frame is electrically connected to the thermally conductive electrode substrate 13. In order to release heat from the heat conductive electrode substrate 13, the heat conductive electrode substrate 13 is provided with a heat radiating means. As a specific example of the heat radiating means, as shown in FIG. 2, a Peltier element 14 is disposed on the back surface of the thermally conductive electrode substrate 13, a radiator 15 is provided on the Peltier element 14, and each is thermally coupled. 15 is cooled by a cooling fan 16.

Since the exit end 12 a of the rod integrator 12 is cut obliquely at an angle B, the optical axis is inclined by an angle A determined by the refractive index of the material of the rod integrator 12. In FIG. 1, the DMD 30 and the injection end of the rod integrator 12 are installed so as to satisfy the Scheinproof relationship. That is, in this embodiment, an equal-magnification illumination optical system is used. Therefore, if the angle formed by the illumination optical axis and the DMD 30 is C, the angle formed by the exit end of the rod integrator 12 and the illumination optical axis is also C. . In this arrangement, (rod integrator cut angle B) + (offset angle A) + C = 90 degrees.
Such an arrangement of the planar light source 1 can form an image of the planar light source 1 on all the micromirrors of the DMD 30.

  FIG. 3 shows another embodiment of the planar light source, and members having the same functions as those in FIG. This flat light source is formed in a spherical surface so that the light of the LED lamp 10 is directed to the incident end of the rod integrator 12 and the incident end of the rod integrator 12 is arranged on the heat conductive electrode substrate 13. It is formed on the convex lens 12b and has the function of condensing the light from the LED lamp 10.

  As shown in FIG. 4, the rod integrator 12 is an optical propagating body in which a light beam introduced from the incident end repeatedly propagates multiple reflections and propagates to the light exit end. Specific examples include a structure in which a clad formed of an optical material having a low refractive index surrounds a core body formed of an optical material having a high refractive index, as in an optical fiber, and is clad in the surrounding air. It is possible to apply a glass rod that can be totally reflected on the surface with the function of, a structure having a core of a plastic rod, a mirror rod that mirrors a surface of glass or plastic with a metal such as aluminum, etc. .

  The illumination optical means 2 makes the angle T formed by the optical axis for forming an image on the DMD 30 and the optical axis of the optical system for projecting the light imaged on the DMD 30 twice the tilt angle of the micromirror of the DMD 30. Is set. The illumination optical system is disposed between the DMD 30 and the rod integrator 12, and the planar light source 1 formed at the light exit end of the rod integrator 12 is telecentric including a first convex lens 20, an aperture stop 21, and a second convex lens 22. An image is formed on the DMD 30 through the optical system. The telecentric optical system is installed between the planar light source 1 and the DMD 30 so as to satisfy the Scheinproof relationship.

  Thus, by illuminating the planar light source 1 and the DMD 30 with the telecentric optical system that satisfies the Scheinproof relationship, all the micromirrors of the DMD 30 can be illuminated at a predetermined angle, for example, 20 degrees or 24 degrees. There is no focus shift as when illuminated with substantially parallel light. Further, the NA of the illumination light can be easily adjusted by enlarging or reducing the aperture stop.

  In this embodiment, a double-sided telecentric optical system is used. At least the DMD side needs to be telecentric. A telecentric optical system with a magnification of 1 was adopted. Of course, if a high-magnification optical system is adopted, the exit end of a small area rod integrator can be imaged on the DMD.

  The projection optical means 4 is composed of a double-sided telecentric reduction projection optical system, and controls the micromirrors of the DMD 30 so that light corresponding to the exposure pattern is imaged on the photosensitive material 7 through the projection lens 40 and exposed.

  The monitor optical means 5 controls the micromirror of the DMD 30 to form an image of the planar light source 1 for each micromirror, and the reflected planar light source 1 passes through the projection lens 40 and corresponds to the pixel coordinate (x, y). Is imaged at the exposure position (x, y), and the in-plane distribution of the light intensity of the exposure optical system is measured. A mounting table for moving the photosensitive material 7 on the substrate to the exposure position is provided. In the measurement of the monitor light, the light of the exposure optical system imaged at the exposure position (x, y) without entering the photosensitive material 7 on the substrate is incident on the diffuser plate 51 through the convex lens 50 and installed behind this. The detected light is detected by the light detector 52 and input to the control means 6.

  Illumination unevenness occurs in the optical system. In the case of the exposure optical system, this is because the luminance unevenness of the light source or the light propagation rate is different between the central portion and the peripheral portion of an optical element such as a lens. Also in the case of a monitor optical system, because of the directivity of lenses and detectors, even if the light has the same light intensity, if the monitor position (exposure surface) is different, the detection efficiency will be different. Since it is necessary to perform correction according to the position of the illumination unevenness generated in the exposure optical system and the monitor optical system, the control unit 6 eliminates the illumination unevenness of the exposure optical system, that is, a correction table for making the in-plane distribution of light intensity uniform. N (x, y), a storage means that stores a correction table M (x, y) for making the illumination unevenness of the monitor optical system uniform, and the designed exposure pattern table G (x, y) of the photosensitive material Converts the sensitivity correction exposure pattern table R (x, y) with reference to the sensitivity curve representing the relationship between the depth of the design value to be removed after development of the photosensitive material and the amount of light, and supports each pixel of the spatial light modulator Control value calculation means for obtaining the control value table S (x, y) = R (x, y) × N (x, y) × M (x, y), and the control value obtained by the control value calculation means And a spatial light modulator control means for controlling each pixel of the spatial light modulator by a computer that implements software. There.

A case is assumed in which a mold of this structure is created on a photosensitive material in order to produce a structure having 64 gradation steps designed by using CAD or the like. The design data is designed as a two-dimensional table in which the height L in the Z direction at the position determined by the x and y coordinates is used as an element. This two-dimensional table is used as an exposure pattern including an intermediate gradation. A desired value table G (x, y) of the depth L from which the photosensitive material is removed is defined. (x, y) is the coordinates of the position corresponding to the pixel of the spatial light modulator.
Photosensitive materials such as resist generally do not react linearly with the amount of light irradiated. Further, as the film thickness increases, the nonlinearity becomes significant due to scattering and absorption. A photosensitive material having a predetermined thickness to be used is irradiated with light while changing a light amount I (w.sec), and a depth L (μ) at which the photosensitive material is removed through a predetermined development process is measured. From this data, a conversion table R (L) is created that correlates the light quantity I necessary to obtain the desired removal depth L. By referring to the conversion table R (L), the element L of the design value table G (x, y) is converted into the necessary light quantity I. It is assumed that the converted new table R (x, y).

Next, the in-plane distribution of the exposure light is measured with the exposure sample not attached. Only one pixel is turned on, and the light intensity of the exposure optical system is measured with a monitor photodetector. The light intensity is measured by sequentially switching the pixels to be turned on, and a table of in-plane distribution for one screen corresponding to all the pixels is created. The exposure light in-plane distribution table comprehensively reflects light source brightness unevenness, illumination optical system illumination unevenness, spatial light modulator illumination unevenness, projection optical system illumination unevenness, etc., and is uniform for each pixel. is not. A correction table N (x, y) is created so that the in-plane distribution is uniform. The value for each pixel in the correction table N (x, y) is a value obtained by multiplying the inverse of the light intensity by a proportional multiplier k. That is, normalize to k. A product is obtained for each element of the control value table and the correction table N (x, y) to obtain a new control value table S (x, y).
S (x, y) = R (x, y) × N (x, y)
Here, x represents multiplication for each element.

  Up to this point, uneven illumination due to the position of the monitor system remains uncorrected. If the illumination unevenness of the monitor system is large and cannot be ignored, a resist film or the like is exposed, and a table M (x, y) for correcting the illumination unevenness of the monitor system is created by a method of measuring the step after development. When the apparatus is assembled, a correction table N (x, y) is created using the monitor system, and the resist film is exposed using this to measure the unevenness in detection of the monitor system from the step measurement. A table M (x, y) for correcting this uniformly is created. The value for each pixel in the correction table is the reciprocal of the measurement step. Once the non-uniformity of detection in the monitor system is measured, this non-uniformity does not change and is stored as a device constant.

  However, in this embodiment, the exposure area is several millimeters in size, and the diameter of the lens 50 used in the monitor system is as large as several centimeters, so that only paraxial rays are used, and scattering is performed immediately before the detector. The element of M (x, y) depending on the position was set to 1 in the required error range due to the effect of placing the body. In this case, it can be omitted.

It is possible to correct a fluctuation factor that frequently fluctuates due to the replacement of the light source and the like by a table N (x, y) that uniformly corrects the monitor light intensity.
S (x, y) = R (x, y) × M (x, y)
Here, x represents multiplication for each element.

  After the correction by the photosensitive material and the correction by the position are completed, the control means controls each pixel of the spatial light modulator by the control value S (x, y), and the light of each pixel is applied to the photosensitive material through the projection optical system. Image exposure is performed.

  FIG. 5 shows an example of the sensitivity curve of the photosensitive material. FIG. 6 shows an example of the designed exposure pattern table G (x, y). FIG. 7 shows an example of a sensitivity correction exposure pattern table R (x, y). FIG. 8 shows an example of the correction table N (x, y). FIG. 9 shows an example of the correction table M (x, y). FIG. 10 shows an example of the control value table S (x, y).

  Another embodiment of the present invention will be described.

  FIG. 11 is a schematic view of an exposure apparatus in which a thin film scatterer is applied to a planar light source. In this embodiment, a DMD 30 is used as a spatial light modulator, and each micromirror is controlled to generate a multi-tone exposure pattern to expose the photosensitive material 7. The configuration of the exposure apparatus includes a planar light source 1, illumination optical means 2, spatial light modulator (DMD) 3, total reflection prism 8, projection optical means 4, monitor optical means 5, and control means (not shown). Here, the functions of the monitor optical means 5 and the control means are the same as those of the embodiment shown in FIG.

  The optical axis of the illumination optical system and the optical axis of the projection optical system are arranged orthogonally, and the DMD 30 is installed on the optical axis of the projection optical system. A total reflection prism 8 is disposed at a position where the optical axis of the illumination optical system and the optical axis of the projection optical system intersect, and the planar light source 1 is totally reflected by the total reflection prism 8 to form an image on the DMD 30. The imaged planar light source 1 transmits the total reflection prism 8 under the control of the DMD 30 and forms an image on the photosensitive material 7 through the projection optical system 4 for exposure. Therefore, the total reflection prism 8 is inclined so as to totally reflect the planar light source 1 at an angle equal to 20 degrees or 24 degrees on the DMD 30. The light source is made into a planar light source 1 by a thin film scatterer 17, and this planar light source 1 is totally reflected by a total reflection prism or mirror 18 in a direction coinciding with the optical axis of the illumination optical system and is incident on the illumination optical system. The total reflection prism or mirror is inclined so that the incident angle to the total reflection prism or mirror of the planar light source 1 by the thin film scatterer 17 is equal to 20 degrees or 24 degrees. The DMD 30 and the planar light source 1 satisfy the Scheinproof relationship.

  FIG. 12 is a schematic diagram of an exposure apparatus using a reflective liquid crystal panel. In this embodiment, a reflective liquid crystal panel 31 is used as the spatial light modulator 3, and the photosensitive material 7 is exposed by generating a multi-tone exposure pattern by controlling each of the two-dimensionally arranged liquid crystal cells. . The configuration of the exposure apparatus includes a planar light source 1, illumination optical means 2, spatial light modulator (reflection liquid crystal panel) 3, PBS (Polarized Beam Splitter) 9, projection optical means 4, monitor optical means 5, and control means (not shown). ). Here, the functions of the projection optical means 4, the monitor optical means 5, and the control means are the same as those of the embodiment shown in FIG.

  In this embodiment, the planar light source 1 that has passed through the illumination optical means 2 is deflected by the PBS 9 to form an image on the reflective liquid crystal panel 31, and the voltage applied to each liquid crystal cell is adjusted to reflect the reflected light from each liquid crystal cell. The light intensity is controlled, and this light is imaged on the photosensitive material 7 through the PBS 9 and the projection optical means 4 and exposed.

  The planar light source 1 uses the structure shown in FIGS. 2 and 3, and the light exit end 12 a of the rod integrator 12 is cut into a plane orthogonal to the optical axis of the rod integrator 12.

  The illumination optical means 2 arranges the optical axis of the illumination optical system and the optical axis of the projection optical system orthogonal to each other, and installs the reflective liquid crystal panel 31 on the optical axis of the projection optical system. A PBS 9 is arranged at a position where the optical axis of the illumination optical system and the optical axis of the projection optical system intersect, and the S wave from the planar light source 1 is reflected by the PBS 9 and imaged on the reflective liquid crystal panel 31. The P wave passes through the PBS 9 and is absorbed (not shown). The imaged planar light source 1 passes through the PBS 9 by the polarization control of the liquid crystal cell, forms an image on the photosensitive material 7 through the projection optical system, and exposes it. Therefore, the polarization separation surface of the PBS 9 is inclined 45 degrees with respect to the planar light source 1.

  The reflective liquid crystal panel 31 is a liquid crystal cell in which individual pixels are minute, and the polarization direction of light reflected by an applied voltage (analog amount) is controlled. The reflective liquid crystal panel 31 and the PBS 9 are combined and used for spatial light modulation and intensity modulation. For example, the reflective liquid crystal panel 31 includes 1365 × 1024 liquid crystal cells each having a size of 13.5 μ × 13.5 μ.

  In the above optical system, the polarization angle of the reflected light from the liquid crystal cell is controlled by an analog voltage applied to the liquid crystal cell. The light intensity is controlled by the light branching action of the PBS 9 that is reflected by the controlled polarization angle of the light. Specifically, when no voltage is applied to the liquid crystal cell, the light from the planar light source 1 passes through the PBS 9 and exposes the photosensitive material with the strongest light intensity. The light from the planar light source 1 when the rated maximum voltage is applied to the liquid crystal cell is reflected by the PBS 9 and does not expose the photosensitive material 7. When an intermediate voltage equal to or lower than the rated maximum voltage is applied to the liquid crystal cell, the photosensitive material 7 is exposed with a light intensity that is inversely proportional to the applied voltage.

Next, the operation of the control means will be described. FIG. 13 shows a flow of exposure using DMD. An illumination unevenness correction table N _D (x, y) of the exposure optical system and a table M (x, y) for correcting the illumination unevenness of the monitor optical system are stored in advance. Enter the sensitivity curve of the photosensitive material. The designed exposure pattern table G (x, y) is input. The exposure pattern table G (x, y) is converted into a photosensitive correction exposure pattern table R (x, y) with reference to the sensitivity curve of the photosensitive material. A control value table S (x, y) corresponding to each micromirror of the DMD 30 is obtained by the following equation.
S (x, y) = R (x, y) × N D (x, y) × M (x, y)

  The DMD 30 is controlled by the intensity adjustment method or the time adjustment method using the control value table S (x, y).

  The intensity adjustment method performs PWM control with the control value table S (x, y) while keeping the micromirror tilt time constant for all micromirrors, and repeats fine switching within the micromirror tilt time. The integrated light intensity within the tilt time of the micromirror is controlled.

  In the time adjustment method, the on-time is controlled by the control value table S (x, y) and the light intensity is controlled by utilizing the proportional relationship between the tilt time of the micromirror and the exposure amount.

Next, the operation of the control means of the exposure apparatus using the reflective liquid crystal panel will be described. FIG. 14 shows the flow of exposure using a reflective liquid crystal panel. An illumination unevenness correction table N _L (x, y) of the exposure optical system and an illumination unevenness correction table M (x, y) of the monitor optical system are stored in advance. Enter the sensitivity curve of the photosensitive material. The designed exposure pattern table G (x, y) is input. The exposure pattern table G (x, y) is converted into a photosensitive correction exposure pattern table R (x, y) with reference to the sensitivity curve of the photosensitive material. A control value table S (x, y) corresponding to each liquid crystal cell is obtained by the following equation.
S (x, y) = R (x, y) × N _L (x, y) × M (x, y)

  The reflective liquid crystal panel is controlled by the intensity adjustment method or the time adjustment method using the control value table S (x, y).

  The intensity adjustment method uses the fact that the voltage applied to the liquid crystal cell and the light intensity are in a proportional relationship, and controls the applied voltage for each liquid crystal cell with reference to the control value table S (x, y) Control strength.

  In the time adjustment method, the applied voltage for each liquid crystal cell is kept constant in all the liquid crystal cells, the on-time is controlled by the control value table S (x, y), and the light intensity for each liquid crystal cell is controlled. .

In the above embodiment, the uneven illumination correction of the monitor optical system is performed, but the control value S (x, y) = R (x, y) × N (x, y) obtained by performing only the light intensity correction may be used. .
In this embodiment, the sensitivity correction of the photosensitive material is used as R (x, y). However, the correction of the film formation efficiency by the light amount or the correction of the etching efficiency by the light amount can be similarly performed.

According to this embodiment, the following effects are produced.
1. By controlling each micromirror with pulse width modulation (PWM) corresponding to the control value for each micromirror of the DMD, the exposure amount of the control value can be obtained for each pixel.
2. By controlling each micromirror with an ON time corresponding to the control value for each micromirror of the DMD, an exposure amount of the control value can be obtained for each pixel. It does not depend on special hardware (PWM device) and can be controlled with high resolution.
3. Since the telecentric illumination optical system is installed so that the planar light source and the DMD satisfy the Scheinproof relationship, all the DMD micromirrors can be used with respect to the DMD that is installed inclined with respect to the illumination optical axis. On the other hand, a planar light source can be imaged at a predetermined angle.
4). By controlling each liquid crystal cell with an applied voltage corresponding to the control value for each liquid crystal cell of the reflective liquid crystal panel, an exposure amount of the control value can be obtained for each pixel.
5). By controlling each liquid crystal cell by applying a predetermined voltage for a time corresponding to the control value for each liquid crystal cell of the reflective liquid crystal panel, it is possible to obtain an exposure amount of the control value for each pixel and at a high resolution. Easy to control.
6). By using a planar light source as an LED light source, there is no fluctuation in the light emission position as compared with a discharge lamp, and it has a long life and does not require replacement.
7). By using an illuminated thin-film scatterer as the planar light source, the planar light source can be obtained at a lower cost than the rod integrator.
8). By using a flat light source as a light exit end cut obliquely to a rod integrator installed with an offset angle with respect to the illumination optical axis, the Scheimpflug relationship is satisfied and the DMD is tilted with respect to the optical axis. A planar light source for imaging can be made. Moreover, light can be used efficiently by installing with an offset angle.

  An LED lamp with no light emission position variation is used as a light source, a flat light source is generated from the light source, and the flat light source and the spatial light modulator are telecentrically imaged on the spatial light modulator so that the Schein-proof relationship is satisfied. Therefore, there is little focus shift on the exposure surface, and the exposure pattern on the spatial light modulator can be transferred in a high resolution state or a predetermined reaction can be caused.

  In the case of exposing the photosensitive material to multiple gradations, the exposure characteristic is corrected so as to be a design value for removing the photosensitive material in consideration of the sensitivity characteristic of the photosensitive material to be used, and uneven exposure is caused. A structure with a multi-tone depth structure can be created on the photosensitive material with high accuracy by performing correction according to the position for each pixel so that the exposure amount can be precisely controlled even under bright illumination. Can do.

1 is a schematic diagram showing a first embodiment of an exposure apparatus according to the present invention. It is a block diagram which shows one Example of a planar light source. It is a block diagram which shows the other Example of a planar light source. It is a figure explaining the optical propagation of a rod integrator. It is a figure which shows an example of the sensitivity curve of a photosensitive material. It is a figure which shows an example of table G (x, y) of the designed exposure pattern. It is a figure which shows an example of table R (x, y) of a sensitivity correction exposure pattern. It is a figure which shows an example of the correction table N (x, y). It is a figure which shows an example of the correction table M (x, y). It is a figure which shows an example of table S (x, y) of a control value. It is a schematic diagram of the exposure apparatus which applied the thin film scatterer to the planar light source. It is a schematic diagram of the exposure apparatus using a reflection type liquid crystal panel. It is a figure which shows the flow of exposure using DMD. It is a figure which shows the flow of exposure using a reflection type liquid crystal panel. It is a figure which shows the focus position at the time of illuminating DMD with focused light.

To solve this, a first aspect of the invention images the light source DMD, an exposure apparatus that exposes a photosensitive material by generating a control to multi-gradation exposure pattern to each of the micromirrors of the DMD, the illumination A planar light source set obliquely with respect to the optical axis and a telecentric optical system that is disposed between the planar light source and the DMD and forms an image of the planar light source on the DMD so that the planar light source satisfies the Scheimpflug relationship Illuminating optical means for forming an image on the DMD, projection optical means for forming an image of the planar light source imaged on the DMD by the illuminating optical means at the exposure position of the photosensitive material, and the exposure position of the photosensitive material for each micromirror of the DMD. Monitor optical means for measuring the in-plane distribution of the light intensity of the exposure optical system, a correction table N (x, y) for uniformizing the in-plane distribution of the light intensity of the exposure optical system measured by the monitor optical means, and the monitor optical system Storage means storing correction table M (x, y) for making illumination unevenness uniform, sensitivity curve representing relationship between design value depth and light quantity obtained by removing photosensitive material, and photosensitive material exposure pattern table G (x, y) is input, and the table G (x, y) is converted to a sensitivity-corrected exposure pattern table R (x, y) with reference to the sensitivity curve, and for each micromirror of the DMD. Control value for obtaining a table S (x, y) = R (x, y) × N (x, y) × M (x, y) of control values in which the corresponding uneven illumination is made uniform and the linearity of the photosensitive material is corrected And a spatial light modulator control unit that controls each micromirror of the DMD by the control value obtained by the control value calculation unit.

  The invention of claim 2 is characterized in that, in claim 1, the planar light source is an obliquely cut light emitting end of a rod integrator installed with an offset angle with respect to the illumination optical axis.

  In addition, since a planar light source is imaged and illuminated on a spatial light modulator composed of DMD so as to satisfy the Scheimpflug relationship with a telecentric optical system, it is compared with the case where the spatial light modulator is illuminated with substantially parallel light. Therefore, exposure with high resolution with little focus shift can be realized.

In order to solve this problem, an exposure apparatus according to the invention of claim 1 includes a DMD that generates a multi-tone exposure pattern, and a telecentric optical system including a first lens, an aperture stop, and a second lens, An illumination optical system for illuminating a DMD, a planar light source installed obliquely at a predetermined angle with respect to the optical axis of the telecentric optical system so as to satisfy the conditions of the DMD and Shine proof by the telecentric optical system, A projection optical system for forming an exposure pattern on a photosensitive material, and the optical axis of the illumination optical system is twice the tilt angle of each micromirror of the DMD with respect to the optical axis of the projection optical system perpendicular to the DMD An exposure optical system set to be inclined at an angle of
A monitor optical system for measuring the in-plane distribution of the light intensity of the exposure optical system at the exposure position of the photosensitive material for each micromirror of the DMD;
The monitor optical system correction table to equalize the in-plane distribution of the light intensity of the exposure optical system measured in N (x, y), the correction table M to uniform the illumination unevenness of the monitor optical system (x, y) Storage means for storing
A sensitivity curve representing the relationship between the depth of the design value obtained by removing the photosensitive material and the amount of light, and a table G (x, y) of the exposure pattern of the photosensitive material are input, and the table G (x, y) is used as the sensitivity. A control value table S obtained by converting the sensitivity-corrected exposure pattern table R (x, y) with reference to the curve and making the illumination unevenness corresponding to each micromirror of the DMD uniform and correcting the linearity of the photosensitive material. control value calculating means for obtaining (x, y) = R (x, y) × N (x, y) × M (x, y);
Spatial light modulator control means for controlling each micromirror of the DMD by the control value obtained by the control value calculation means;
It is characterized by having.

In addition, a DMD that generates a multi-tone exposure pattern, a telecentric optical system including a first lens, an aperture stop, and a second lens, and an illumination optical system that illuminates the DMD, and the telecentric optical system A planar light source installed obliquely at a predetermined angle with respect to the optical axis of the telecentric optical system so as to satisfy the conditions of the DMD and Shineproof, and a projection optical system that forms an image of the exposure pattern on a photosensitive material And an exposure optical system in which the optical axis of the illumination optical system is set to be inclined with respect to the optical axis of the projection optical system perpendicular to the DMD by twice the tilt angle of each micromirror of the DMD. As a result , compared with the case where the DMD is illuminated with substantially parallel light, high-definition exposure can be realized with less focus shift.

Claims (9)

In an exposure apparatus that controls each pixel of the spatial light modulator to generate a multi-tone exposure pattern to expose a photosensitive material,
A planar light source;
Illumination optical means that is disposed between the planar light source and the spatial light modulator, and includes a telecentric optical system that forms an image of the planar light source on the spatial light modulator;
Projection optical means for imaging a planar light source imaged on the spatial light modulator by the illumination optical means at an exposure position of the photosensitive material;
Monitor optical means for measuring an in-plane distribution of light intensity of an exposure optical system at an exposure position of the photosensitive material for each pixel of the spatial light modulator;
A correction table N (x, y) for uniforming the in-plane distribution of light intensity of the exposure optical system measured by the monitor optical means and a correction table M (x, y) for uniforming illumination unevenness of the monitor optical system are stored. Storage means
A sensitivity curve indicating the relationship between the depth of the design value obtained by removing the photosensitive material and the amount of light and a table G (x, y) of the exposure pattern of the photosensitive material are input, and the table G (x, y) is used as the sensitivity. The curve is converted into a sensitivity-corrected exposure pattern table R (x, y) and a control value table S (x, y) = R (x, y) × corresponding to each pixel of the spatial light modulator. Control value calculating means for obtaining N (x, y) × M (x, y);
Spatial light modulator control means for controlling each pixel of the spatial light modulator by the control value obtained by the control value calculation means,
An exposure apparatus characterized in that light of each pixel of the spatial light modulator controlled by the spatial light modulator control means is imaged and exposed on a photosensitive material through a projection optical system of the projection optical means. 2. The exposure apparatus according to claim 1, wherein the spatial light modulator is constituted by a DMD, and each micromirror is controlled by pulse width modulation (PWM) corresponding to a control value for each micromirror of the DMD. 3. The exposure apparatus according to claim 1, wherein the spatial light modulator is constituted by a DMD, and each micromirror is controlled with an on-time corresponding to a control value for each micromirror of the DMD. 4. The exposure apparatus according to claim 1, wherein the planar light source and the DMD are installed so as to satisfy the Scheinproof relationship. 2. The exposure apparatus according to claim 1, wherein the spatial light modulator is constituted by a reflective liquid crystal panel, and each liquid crystal cell is controlled by an applied voltage corresponding to a control value for each liquid crystal cell of the reflective liquid crystal panel. 2. The spatial light modulator according to claim 1, wherein the spatial light modulator is constituted by a reflective liquid crystal panel, and each liquid crystal cell is controlled by applying a predetermined voltage for a time corresponding to a control value for each liquid crystal cell of the reflective liquid crystal panel. A featured exposure apparatus. 2. The exposure apparatus according to claim 1, wherein the planar light source includes a light source composed of LEDs. 7. The exposure apparatus according to claim 1, wherein the planar light source is an illuminated thin film scatterer. 5. The exposure apparatus according to claim 4, wherein the planar light source is an obliquely cut light emitting end of a rod integrator installed with an offset angle with respect to the illumination optical axis.

Images