JP7492889B2 - Light source device and exposure device - Google Patents

Description

The present invention relates to a light source device, and in particular to the incidence of illumination light on optical elements such as integrators.

A light source device consisting of a lamp unit made up of a discharge lamp and a reflector is known as a light source device used in projectors, exposure devices, etc. Light emitted from the discharge lamp is reflected by the reflector and guided to an illumination optical system including optical elements (integrators such as a focusing lens, rod lens, and fly-eye lens). The illumination light has its illuminance homogenized by the integrator, and is collimated by the collimator lens, and is irradiated onto a light modulation element array such as a DMD, a workpiece, etc.

As discharge lamps age, the electrode tips wear down, and as the lamp is turned on, the proportion of light that enters the integrator decreases, causing a drop in illuminance. To prevent this, in a multi-lamp light source device equipped with multiple lamp units, light with a wider illumination area than the integrator entrance surface is made to enter the integrator (see Patent Document 1).

JP 2009-302218 A

Light source devices installed in projectors, exposure devices, etc. are required to be installed so that the lamp axis is approximately horizontal for reasons such as good performance of the halogen cycle and suppression of electrode wear when using AC discharge lamps. Therefore, the reflector is held so that its open end is approximately vertical.

When the reflector thermally expands while the lamp is on, the reflector's central axis moves vertically due to factors such as the reflector's holding structure. As a result, the cross section of the light beam (irradiation pattern) entering the integrator changes due to differences in the temperature environment between immediately after the lamp is turned on and when the lamp is lit stably, and part of the illumination light does not enter the integrator entrance surface, reducing the illumination efficiency.

Therefore, there is a need for a light source device that allows illumination light to be incident on the integrator entrance surface while suppressing a decrease in illumination efficiency, regardless of the lamp lighting status.

The light source device according to one aspect of the present invention comprises a lamp and a concave reflector whose open end is aligned vertically and which reflects the illumination light emitted from the lamp. The concave reflector can be, for example, an ellipsoidal or parabolic reflector. It can be made up of a single lamp, or it can be made up of multiple lamp units, each of which is made up of a lamp and a concave reflector, arranged in a row.

The illumination light travels along the central axis of the concave reflector and enters an optical element that is positioned in the direction of travel of the illumination light. The optical element can be configured, for example, as an integrator. The illumination light is configured to enter with a luminous flux that corresponds to the size of the entrance surface. In other words, the illumination light does not have an illumination area that is much larger than the entrance surface of the optical element, or an illumination area where the illumination light is only incident on a small part of the entrance surface, but rather, the illumination light enters the optical element with a luminous flux that matches the size of the entrance surface of the optical element so as to minimize loss of illumination light from the light source.

In the present invention, the cross section of the illuminating light beam at the incident surface of the optical element is distorted from a circular shape so that the illuminated area expands along a line corresponding to the vertical direction. The degree and direction of the distortion can be configured in various ways. For example, the illuminated area can be distorted so that it expands to one side of the line. Also, the illuminated area can be distorted so that the end of the illuminated area extends to one side of the line.

For example, if the lamp is a discharge lamp with a pair of electrodes and the concave reflector is an ellipsoidal or parabolic reflector, the discharge lamp is positioned so that the center between the electrodes is offset in a direction along one axis from the focal point of the concave reflector, and is offset along the reflector's central axis to the bottom side opposite the opening end of the concave reflector. The offset amount ΔY along one axis and the offset amount ΔZ along the reflector's central axis can be determined to satisfy 0.2≦ΔY/ΔZ≦4.

Meanwhile, a light source device according to another aspect of the present invention includes a lamp and a concave reflector that forms a circular opening end and directs the illumination light emitted from the lamp in a direction along the center of the reflector, and the illumination light is incident on the entrance surface of the optical element with a luminous flux according to the size of the entrance surface. Then, on the entrance surface of the optical element that is perpendicular to the central axis of the reflector, the cross section of the luminous flux of the illumination light is distorted so that the illuminated area expands along a predetermined line that passes through the intersection with the central axis of the reflector along the traveling direction of the illumination light.

An exposure apparatus according to one aspect of the present invention includes the above-mentioned light source device and an illumination optical system including the above-mentioned optical element, and the light source device is installed so that the central axis of the reflector is aligned along the horizontal direction or inclined within a predetermined angle range relative to the horizontal direction.

The present invention makes it possible to allow illumination light to be incident on the integrator entrance surface while suppressing a decrease in illumination efficiency, regardless of the lamp lighting status.

1 is a schematic block diagram of an exposure apparatus equipped with a light source device according to a first embodiment. FIG. 2 is a schematic cross-sectional view of a light source device. FIG. 3 is a partially enlarged view of the vicinity of the discharge lamp in FIG. 2. 4 is a diagram showing an irradiation pattern of illumination light incident on an entrance surface of an integrator. FIG. FIG. 5 is a diagram showing an irradiation pattern different from that shown in FIG. 4. FIG. 13 is a diagram showing an irradiation pattern when the discharge lamps are not arranged offset. FIG. 13 is a diagram showing an exposure apparatus according to a second embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings.

Figure 1 is a schematic block diagram of an exposure device equipped with a light source device according to the first embodiment.

Here, the exposure apparatus 10 is configured as a contact exposure apparatus that projects pattern light onto the substrate W using a photomask 14. The exposure apparatus 10 includes a light source device 20 and an exposure head 11, and is turned on by a light source driver 19 controlled by a controller 15. The exposure head 11 includes an illumination optical system 12 including an integrator 13 that uniforms the illuminance, and a photomask 14.

The light emitted from the light source device 20 passes through the illumination optical system 12 and is incident on the photomask 14. The light that passes through the photomask 14 is projected onto the substrate W on the exposure stage 18. This forms a predetermined pattern on the substrate W.

In the exposure apparatus 10, a high-illuminance mode and a low-illuminance mode can be set. When the high-illuminance mode is set by the user, high power is input to the discharge lamp 30, and when the low-illuminance mode is set, low power is input. The exposure apparatus 10 can also be configured as a maskless exposure apparatus or a projection exposure apparatus.

Figure 2 is a schematic cross-sectional view of the light source device 20. Figure 3 is a partially enlarged view of the vicinity of the discharge lamp 30 in Figure 2.

The light source device 20 is composed of a lamp unit consisting of a discharge lamp 30 and a concave reflector 40, and in this case is composed of one lamp unit. The discharge lamp 30 is, for example, an AC type high pressure or ultra-high pressure mercury lamp, and is provided with a pair of electrodes 32, 34 inside the light emitting tube 33. Sealing tubes 36, 38 are integrally formed on both ends of the light emitting tube 33 of the discharge lamp 30, and the sealing tube 38 is supported or held by a holding member 60.

The concave reflector 40 is a reflector that guides the light emitted from the discharge lamp (hereinafter referred to as illumination light) toward the illumination optical system 12 along the reflector central axis Z, and is configured here as an elliptical reflector with an elliptical cross section. The illumination light emitted from the circular opening end 40A is incident on the entrance surface 13A of the integrator of the illumination optical system 12.

The reflector central axis Z is perpendicular to the incident surface 13A of the integrator 13 as the optical axis of the illumination light, and the illumination light is incident on the incident surface 13A with a luminous flux equivalent to its area size. A folding mirror or the like may be provided between the concave reflector 40 and the integrator 13. The concave reflector 40 may also be configured as a parabolic reflector.

The concave reflector 40 is fixed to the holder 50 so that the central axis Z of the concave reflector 40 (hereinafter referred to as the reflector central axis) is horizontal, for reasons such as favorable expression of the halogen cycle in the discharge lamp 30 and prevention of electrode wear in the AC discharge lamp 30. The holder 50 has an opening 50A corresponding to the opening end 40A side, and is fixed within the device so that the surface (herein referred to as the reference surface) 50S facing the opening end 40A side is vertical.

The concave reflector 40 has its opening end 40A in contact with the reference surface 50S, fits into the annular protrusion 52 provided on the reference surface 50S, and is fixed by a force acting from the bottom side of the reflector toward the reference surface 50S. As a result, the opening end 40A of the concave reflector 40 is aligned vertically.

Because the concave reflector 40 thermally expands when the lamp is turned on, the diameter size of the annular protrusion 52 is set to be larger than the size of the opening end 40A of the concave reflector 40. Therefore, when the concave reflector 40 is fitted into the holder 50, the opening end 40A abuts against the lower end 52B of the protrusion 52, while a gap SB is created between the opening end 40A and the upper end 52A of the protrusion 52.

In this embodiment, the center C between the electrodes of the discharge lamp 30 is not located at the focal point C0 of the concave reflector 40, but is offset with respect to the reflector central axis Z and the axis Y (hereinafter referred to as the vertical axis) along the vertical direction (reference plane 50S) passing through the focal point C0.

Specifically, it is offset downward by ΔY along the vertical axis Y, and offset by ΔZ along the reflector central axis Z to the opposite side (bottom side) of the opening end 40A of the concave reflector 40. Therefore, the lamp axis E of the discharge lamp 30 is located below the reflector central axis Z. There is no offset with respect to the X-axis that passes through the focal point C0 and is perpendicular to the vertical axis Y (perpendicular to the paper).

The offset amounts ΔY and ΔZ are determined according to the material, size, etc. of the concave reflecting mirror 40. Here, ΔY and ΔZ are determined so as to satisfy 0.2≦ΔY/ΔZ≦4. For example, ΔY and ΔZ are set to satisfy ΔY/ΔZ=1, i.e., to the same offset amount.

By offsetting the discharge lamp 30 from the concave reflector 40 in this way, the amount of illumination light incident on the incident surface 13A of the integrator 13 is not reduced in either the high-illuminance mode or the low-illuminance mode, making it possible to suppress a reduction in illuminance. This will be described in more detail below.

Figure 4 shows the cross-sectional shape of the luminous flux of illumination light incident on the incident surface 13A of the integrator 13 (hereinafter also referred to as the irradiation pattern). Figure 5 shows an irradiation pattern different from that of Figure 4. Figure 6 shows an irradiation pattern when the discharge lamp 30 is not offset (the center C between the electrodes is aligned with the focal point C0). First, the thermal expansion of the concave reflector 40 when the lamp is turned on and the distortion of the luminous flux of the illumination light based on the conventional arrangement of the discharge lamp 30 in Figure 6 will be explained.

The integrator 13 is composed of a rod lens or the like, and here the incident surface 13A is formed in a square shape. The illumination light emitted from the circular opening end 40A of the light source device 20 is incident on the incident surface 13A of the integrator 13 as a light beam with a circular cross section. Therefore, when illuminating light is incident on the entire area of the incident surface 13A of the integrator 13, it is necessary to form an irradiation pattern that includes the vicinity of the four corners 13K1 to 13K4 of the area of the incident surface 13A.

On the other hand, if a large amount of illumination light does not enter the integrator 13 by deviating from the entrance surface 13A, the illumination efficiency decreases, resulting in unnecessary power consumption. Therefore, it is desirable to have illumination light with a luminous flux size with a diameter from the center A0 of the entrance surface 13A to the four corners 13K1 to 13K4 of the area enter the entrance surface 13A of the integrator 13. Therefore, the concave reflector 40 and the like are designed so that the illumination enters the integrator 13 with a luminous flux size according to the entrance surface 13A of the integrator 13.

When the lamp is lit, the concave reflector 40 thermally expands, but because the opening end 40A abuts against the lower end 52B of the convex portion 52, the entire concave reflector 40 is deformed as a whole so that the reflector central axis Z moves upward, and the opening end 40A abuts against the upper end 52A of the convex portion 52, eliminating the gap SB (see Figure 1). A similar deformation occurs when the discharge lamp 30 transitions from immediately after the lamp is lit to when the lamp is lit stably. As a result, the irradiation pattern of the illumination light incident on the entrance surface 13A of the integrator 13 also changes.

Generally, the concave reflector 40 and other components are designed to maximize the illumination efficiency in high-illuminance mode and when the lamp is lit steadily. In that case, immediately after the lamp is turned on or in low-illuminance mode, part of the illumination light does not enter the entrance surface 13A of the integrator 13, resulting in a drop in illuminance.

Figure 6 shows an irradiation pattern C1 in low illuminance mode (immediately after the lamp is turned on) and an irradiation pattern C2 in high illuminance mode (when the lamp is stably turned on) on the incident surface 13A. Here, the axis that passes through the area center A0 of the incident surface 13A and is aligned vertically to the opening end 40A of the concave reflector 40 is the y-axis, and the axis that passes through the area center A0 and is perpendicular to the y-axis is the x-axis.

The y-axis corresponds to the Y-axis along the vertical direction passing through the focal point C0 of the concave reflector 40, and the x-axis corresponds to the X-axis. In the high-illuminance mode (when the lamp is lit stably), the position c where the reflector central axis Z intersects with the incident surface 13A approximately coincides with the position of the area center A0. In other words, the central position of the circular irradiation pattern C2 approximately coincides with the area center A0.

On the other hand, in the low-illuminance mode (immediately after the lamp is turned on), the effect of thermal expansion of the concave reflector 40 is small, so an irradiation pattern C1 is formed with its center at position c', which is the intersection point of the reflector central axis Z on the incident surface 13A. The center of the irradiation pattern C1 is shifted downward by Δy from the area center A0 along the y axis.

In low-illuminance mode (immediately after the lamp is turned on), illumination light is not incident on a portion of the incident surface 13A (particularly near the two corners 13K1 and 13K4). Therefore, in order to obtain the required amount of exposure to the substrate W, it is necessary to increase the illuminance by supplying excessive power in low-illuminance mode or immediately after the lamp is turned on.

On the other hand, if the size of the illumination area of the illumination patterns C1 and C2 is designed to be enlarged in advance to prevent this, the illumination light will be incident on the entire area of the entrance surface 13A, but the amount of illumination light that falls outside the entrance surface 13A area will increase, resulting in a decrease in illumination efficiency.

Figure 4 shows the irradiation patterns when the discharge lamp 30 in this embodiment is offset. As shown in Figure 4, in both the low illuminance mode (immediately after the lamp is turned on) and the high illuminance mode (when the lamp is lit stably), the irradiation patterns C'1 and C'2 are patterns that include the entire area of the entrance surface 13A.

Compared to irradiation patterns C1 and C2 in FIG. 6, irradiation patterns C'1 and C'2 are distorted so that the ends of their irradiation areas expand in the positive direction of the y axis, i.e., the pattern shape extends in the +y direction. The positive y axis direction corresponds to the positive Y axis direction of the concave reflector 40, i.e., the vertical direction. On the other hand, there is no distortion in irradiation patterns C'1 and C'2 with respect to the x axis, and the pattern shape is symmetrical with respect to the y axis. In FIG. 4, irradiation patterns C'1 and C'2 have a pattern shape close to an egg shape.

Figure 5 shows other irradiation patterns C"1 and C"2. Unlike Figure 4, in the low illuminance mode (immediately after the lamp is turned on), irradiation pattern C"1 does not include the areas near corners 13K1 and 13K4 of the entrance surface 13A, and no illumination light is incident on the area. However, as is clear from a comparison with Figure 6, the amount of illumination light that is not incident is suppressed. On the other hand, irradiation pattern C"2 is formed as an irradiation pattern that includes corners 13K1 to 13K4 of the entrance surface 13A. Note that, even in the case of irradiation pattern C"2, even if no illumination light is incident on the areas near corners 13K1 and 13K4 of the entrance surface 13A, the decrease in illumination efficiency is suppressed compared to the case where the discharge lamp 30 is not offset.

Thus, according to this embodiment, in the exposure apparatus 10 equipped with the light source device 20 that causes illumination light to be incident on the integrator 13, the light source device 20 is composed of a lamp unit equipped with a discharge lamp 30 and a concave reflector 40. The discharge lamp 30 has its inter-electrode center C offset from the focal point C0 along the Y axis that is perpendicular to the concave reflector 40 and the bottom side of the reflector central axis Z.

As a result, the irradiation patterns C'1 and C'2 incident on the incident surface 13A of the integrator 13 become irradiation patterns that are distorted relative to the circular pattern so that the irradiation area expands in the + direction of the y axis corresponding to the vertical direction (upward direction of the device). With such an irradiation pattern, the illumination light can be effectively incident on the integrator 13 without reducing the illumination efficiency in both the low-illuminance mode (immediately after the lamp is turned on) and the high-illuminance mode (when the lamp is lit stably).

As mentioned above, the offset amounts ΔY and ΔZ are set to satisfy 0.2≦ΔY/ΔZ≦4. This is because if ΔZ is too large relative to ΔY, the irradiation pattern itself will simply deform and the distortion will be small, whereas if ΔZ is too small relative to ΔY, the irradiation pattern will be extremely distorted.

In Figures 4 to 6, the incident surface 13A of the integrator 13 is formed in a square shape, but it can also be rectangular or circular instead. Even in this case, the same effect can be obtained by distorting the irradiation pattern in the positive direction of the y axis.

The distortion of the irradiation pattern may be achieved by means other than offsetting the discharge lamps 30. For example, it is possible to distort the irradiation pattern by deforming the opening end shape of the concave reflector so that it is not circular. It is also possible to configure a concave reflector so that the irradiation pattern becomes elliptical.

Therefore, it is possible to distort the irradiation pattern in both the positive and negative directions of the y axis to make it elliptical. It is also possible to create an irradiation pattern with asymmetric distortion with respect to the y axis.

Figure 7 shows an exposure apparatus according to the second embodiment.

The exposure device 10' is equipped with a multi-lamp light source device 20', which has multiple lamp units 20N each consisting of a concave reflector 40 and a discharge lamp 30. The multiple lamp units 20N are arranged in a row along the vertical direction, and each lamp unit 20N is held by a holder so that its open end is aligned vertically, as in the first embodiment.

The illumination light from the light source device 20' is reflected by mirrors M1 and M2 and enters the entrance surface 13A of the integrator 13. At this time, the illumination light from each lamp unit enters the entrance surface 13A of the integrator 13.

Even with such a multi-lamp light source device 20', in the illuminance mode (immediately after the lamp is turned on) and in the high illuminance mode (when the lamp is lit stably), there is a shift near the upper and lower ends of the irradiation pattern. Therefore, as in the first embodiment, by offsetting the center between the electrodes of each discharge lamp with respect to the focal point of the concave reflector and forming an irradiation pattern in each lamp unit in which the irradiation pattern is distorted in a direction corresponding to the vertical direction, it is possible to make the light enter the entrance surface 13A of the integrator 13 while suppressing a decrease in illumination efficiency. Note that instead of arranging multiple lamp units 20N vertically, they may be fixedly arranged at an angle (for example, in the range of ±20°) inclined.

The light source device shown in the first and second embodiments can also be applied to devices other than exposure devices, such as projectors. In this case, the opening end of the concave reflector 40 can be positioned and fixed in accordance with the offset arrangement direction of the discharge lamp 30.

REFERENCE SIGNS LIST 10 Exposure device 13 Integrator 20 Light source device 30 Discharge lamp 40 Concave reflecting mirror

Claims (8)

A discharge lamp having a pair of electrodes ;
an ellipsoidal or parabolic concave reflector whose open end is aligned along a vertical direction and which reflects illumination light emitted from the discharge lamp;
the illumination light is incident on an incident surface of an optical element with a luminous flux according to the size of the incident surface;
The center between the electrodes is offset with respect to the central axis of the reflector and a vertical axis along a vertical direction passing through the focal point of the concave reflector,
A light source device characterized in that, at the incident surface of the optical element, the cross section of the illuminating light beam is distorted so that the irradiation area expands in the vertical direction of a line corresponding to the vertical axis, relative to the circular cross section of the illuminating light beam when the center between the electrodes coincides with the focus of the concave reflector . A discharge lamp having a pair of electrodes ;
a concave reflector having an elliptical or parabolic surface that forms a circular opening end and guides the illumination light emitted from the discharge lamp in a direction along a central axis of the reflector;
the illumination light is incident on an incident surface of an optical element with a luminous flux according to the size of the incident surface,
The center between the electrodes is offset with respect to the reflector central axis and a vertical axis along the open end that passes through the focal point of the concave reflector;
A light source device characterized in that, on the incident surface of the optical element perpendicular to the central axis of the reflector, the cross section of the illuminating light beam is distorted so that the illuminated area expands along one side of a predetermined line corresponding to the vertical axis, relative to the circular cross section of the illuminating light beam when the center between the electrodes coincides with the focal point of the concave reflector. 3. The light source device according to claim 1, wherein a cross section of the luminous flux of the illumination light is asymmetric with respect to a vertical line that is perpendicular to the line and passes through the center of the incidence surface. 4. The light source device according to claim 1, wherein a cross section of the illuminating light is distorted so that an end of the illuminated area extends in a vertical direction or in one direction of the line. 2. The light source device according to claim 1, wherein the discharge lamp is arranged so that the center between the electrodes is offset from the focal point of the concave reflector in a direction opposite to the vertical direction of the vertical axis , and is offset along the central axis of the reflector toward the bottom side opposite the opening end of the concave reflector. The light source device according to claim 5, characterized in that the offset amount ΔY and the offset amount ΔZ along the central axis of the reflecting mirror are determined to satisfy 0.2≦ΔY/ΔZ≦4. a plurality of lamp units each including a lamp and a concave reflecting mirror are arranged in a row;
7. The light source device according to claim 1, wherein illumination light from said plurality of lamp units is incident on an incident surface of said optical element. A light source device according to any one of claims 1 to 7,
an illumination optical system including the optical element,
1 is a perspective view of an exposure apparatus according to the first embodiment of the present invention; and

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