JP6457934B2 - Light source device and exposure apparatus provided with light source device - Google Patents

Description

  The present invention relates to a light source device that can be used in a projector, an exposure apparatus, and the like, and more particularly, to an arrangement of a discharge lamp used as a light source or a light amount / illumination control for the discharge lamp.

In a projector, an exposure apparatus, and the like, a light source device including a short arc discharge lamp having a high brightness and a small size and a small diameter is used. The light source device includes a bowl-shaped reflecting mirror whose reflecting surface is a rotating paraboloid, and light from the discharge lamp is irradiated in a predetermined direction through the reflecting mirror. In particular, when increasing the light emission intensity, a multi-lamp light source device having a plurality of lamp units each composed of a discharge lamp and a reflecting mirror is incorporated.
In the lamp unit, the discharge lamp is mounted along the central axis of the reflector, and the light emitted in the radial direction from the discharge tube is guided in one direction by the reflector. The arc luminescent spot position of the discharge lamp is the position of the reflector. The discharge lamp is coaxially fixed so as to substantially coincide with the focal position (see, for example, Patent Document 1).
As for the light amount adjustment of the discharge lamp, a light source device that translates the position of the discharge lamp along the central axis of a reflecting mirror is known (see Patent Document 2). There, a discharge lamp that is movable in the axial direction is mounted in the projector apparatus. In order to prevent the influence of heat generated during lighting, the luminescent spot position of the discharge lamp is shifted from the focal position of the reflecting mirror, and the amount of light emitted from the reflecting mirror is adjusted.
On the other hand, the exposure apparatus is required to irradiate light with high luminance and constant illuminance. Therefore, when the exposure operation is interrupted, the illuminance is measured using a photometric device, and the constant illuminance lighting control is performed by adjusting the power supplied to the discharge lamp (see, for example, Patent Document 3).

JP 2006-147362 A JP 2010-077251 A JP 2009-205025 A

When the discharge lamp is lit for a long time, the tip of the electrode is deformed due to the influence of convection of rare gas such as halogen gas in the discharge tube, and the position of the arc bright spot gradually changes. As a result, the arc bright spot deviates from the focal position of the reflecting mirror. This fluctuation of the arc bright spot decreases the lamp illuminance early and shortens the lamp life.
Therefore, there is a need for a discharge lamp arrangement that does not reduce illuminance even when the discharge lamp is used for a long period of time.
On the other hand, constant illuminance lighting control is performed in an exposure apparatus or the like. In this case, when the illuminance of the lamp decreases due to the exhaustion of the discharge tube and the electrode, the lamp power is increased accordingly. This control is continued until the lamp life approaches the lamp power upper limit. Therefore, in order to extend the lamp life, it is desirable to suppress the lamp power at the start of lamp lighting as much as possible.
However, if the lamp power at the initial start-up is suppressed, the arc bright spot position may fluctuate irregularly and flicker may occur, and the illuminance becomes unstable. Therefore, it is necessary to light up with a certain level of power. In addition, since the power value varies depending on individual lamp differences, in a multi-lamp type light source device or the like, it is necessary to initially start the lamp with higher power in order to prevent flickering in all the lamps.
Therefore, it is necessary to suppress the decrease in illuminance during the discharge lamp lighting period and to make the increase in supplied power as slow as possible.

The light source device of the present invention includes at least one discharge lamp having an electrode pair disposed opposite to each other in the discharge tube so that the electrode axis coincides with the lamp center axis, and a concave reflecting surface having a focal point. And at least one reflecting mirror for guiding the light in one direction.
For example, the discharge lamp is a high-intensity short arc type lamp containing 0.2 mg / mm ³ or more of mercury and can be used for a projector, an exposure apparatus, and the like. In addition, a lamp unit composed of one discharge lamp and one reflecting mirror may be used alone, or a multi-lamp light source device in which a plurality of lamp units are arranged may be configured.
In the present invention, the discharge lamp is disposed along the central axis of the reflector, and is separated from the reference position by a predetermined distance along a direction perpendicular to the central axis of the reflector. Here, the reference position is determined with respect to the position when the discharge lamp center axis is made coincident with the reflector center axis and the arc bright spot is matched with the reflector focus position, that is, the axial direction and the vertical direction of the conventional discharge lamp. Represents the position. Therefore, when the discharge lamp is arranged along the horizontal direction, the discharge lamp is offset so that the lamp center axis is positioned vertically below the reflector central axis. In addition, it does not have to be strictly perpendicular (90 °) to the central axis of the reflector, and may be along a certain extent with respect to the vertical direction instead of the central axis direction of the reflector.
Since the discharge lamp is offset from the central axis of the reflector along the vertical direction, the arc bright spot moves vertically upward as the lamp is lit for a long time. Therefore, by appropriately adjusting the arrangement of the light source device so that the discharge lamp is horizontal, a decrease in illuminance is suppressed and the lamp life is extended.
The discharge lamp may be arranged strictly parallel to the central axis of the reflecting mirror, or the discharge lamp may be omitted as long as the arc bright spot moves toward the focal direction on the central axis of the reflecting mirror. A parallel offset arrangement may be used. Further, the position may be strictly separated along a vertical line of the central axis of the reflector, or may be offset along a substantially vertical line.
For example, the diameter of the electrode support rod that supports the electrode pair can be set in a range of 0.3 to 0.6 mm. In this case, the lamp central axis is from the reflector central axis to the electrode support rod diameter. It is possible to determine the position at a distance of 5 to 45%. In particular, the center axis of the lamp can be separated from the center axis of the reflector by a distance interval of 10 to 35%, further 20 to 25% of the electrode support rod diameter.
In order to reduce radiant heat from the reflecting mirror, it is preferable to provide one opening. For example, the light source device may be installed so that the discharge lamp is horizontally arranged and the opening is positioned on the lower side of the lamp vertically. Further, when a plurality of lamps composed of a discharge lamp and the reflecting mirror are arranged adjacent to each other, four openings may be provided in four directions.
Furthermore, the light source device of the present invention can include an illumination control unit that performs constant illuminance lighting control by adjusting the power of the discharge lamp. The illumination control unit can drive the discharge lamp with a power value that is larger by a predetermined amount than the initial limit power value corresponding to the initial limit light amount that does not cause flickering at the initial lamp start. Here, the initial limit light amount that does not cause flickering represents the minimum limit light amount within a range in which the lamp emission can be regarded as being stable, and the initial limit power value represents a power value that is supplied accordingly.
When the lamp center axis is arranged so as to be positioned vertically below the reflector center axis, the initial limit power value at the start of lamp lighting is higher than that of a conventional lamp that is not offset arranged. The lamp is driven with a power value higher than the power value.
In the conventional discharge lamp, the lamp power increases as the lighting time elapses at the time of constant illuminance lighting control. Therefore, an attempt is made to suppress the power value at the start of lighting as much as possible. Start lighting the lamp with the value. For this reason, although the power value at the start of lighting is relatively high, the arc bright spot approaches the central axis of the reflector as the lighting time elapses, so that the power increase rate can be suppressed even when the constant illumination is continued. And since the electric power at the time of lighting start is high, it can shift to a stable lighting state quickly without flickering.
For example, when the light source device includes a plurality of discharge lamps and a plurality of reflecting mirrors, that is, a multi-lamp type light source device in which a plurality of lamp units each composed of a discharge lamp and a reflecting mirror are arranged, the illumination control unit At the time of starting, the discharge lamp can be driven by a power value larger than the maximum initial limit power value among the initial limit power values of the plurality of discharge lamps. Since light is emitted at the maximum power value, flicker can be prevented from occurring in any of the discharge lamps.
On the other hand, an exposure apparatus according to another aspect of the present invention is an exposure apparatus including the light source device, and is two-dimensionally arranged with a light amount measurement unit that measures the amount of projection light irradiated to the exposure target area. A plurality of light modulation elements, and a light modulation element array that projects illumination light from the light source device onto the exposure target area of the object to be drawn, and a constant illumination lighting control of the projection light by controlling the power supplied to the discharge lamp. And a light amount adjusting unit capable of adjusting the light amount of the projection light by controlling a plurality of light modulation elements. For example, the discharge lamp is arranged such that the lamp center axis is positioned vertically below the reflector center axis.
Then, the light amount adjusting unit reduces the light amount of the projection light by setting an unused light modulation element for a predetermined period from the initial lamp start. Here, “not used” means that an effective light modulation element that can be used for projection is not used according to the drawing pattern and drawing position, but is not actually used for the exposure operation. The predetermined period is a fixed period in which the instability of lamp emission continues from the start of the initial start, and can be set to several hours to several tens of hours. After the elapse of a predetermined period, the projection light amount reduction by the light modulation element is completed, and drawing processing is performed by the effective light modulation element.
The light amount adjustment unit can determine a usage rate that represents a ratio of actual use among all effective light modulation elements that can be used for projection, and can reduce the projection light amount. For example, the light amount adjusting unit can determine unused light modulation elements so as to have a substantially uniform distribution and an irregular distribution with respect to the light modulation element array region. Here, “substantially uniform distribution” and “irregular distribution” means that the unused light modulation elements are uniformly dispersed and dissipated at substantially equal intervals when viewed from the entire light modulation element array region. On the other hand, it represents a distribution state in which there is no local uneven distribution, a part of the blank space, and a regular arrangement throughout the entire arrangement region. This is similar to a distribution state in which the arrays of unused light modulation elements regularly arranged at regular intervals are slightly shifted.
For constant illuminance lighting control, if the light modulation element array such as DMD becomes a mask / filter to reduce the amount of projection light, the power value increases. On the other hand, due to the offset arrangement of the discharge lamp, the rate of increase in power can be suppressed by bringing the arc bright spot closer to the reverberation center axis. Moreover, even if the usage rate is set to 100% after a certain period of time, since the power at the time of starting is high, it is possible to suppress the amount of power reduction and to prevent flickering and the like.
The light quantity adjusting unit can set the unused light modulation element so that, when the lamp is started, a power larger than the minimum power of the discharge lamp that does not flicker is supplied. Here, the initial limit light amount that does not cause flickering represents the minimum limit light amount within a range in which the lamp emission can be regarded as being stable, and the initial limit power value represents the power value supplied accordingly. Even in unstable light emission at the time of initial start-up, flickering is reliably suppressed, while the increase in power is moderate, so that the lamp life can be extended.
For example, when the light source device is a multi-lamp type light source device including a plurality of discharge lamps and a plurality of reflecting mirrors, the light amount adjusting unit is set to the initial limit power value of each of the plurality of discharge lamps when the lamp is started. The discharge lamp can be driven with a power value larger than the maximum initial limit power value.

  According to the present invention, when performing constant illuminance lighting or the like, the life of the discharge lamp can be extended.

It is a perspective view of the exposure apparatus which is 1st Embodiment. It is a block diagram of an exposure apparatus. It is a top view of a light source device. It is a schematic sectional drawing of a light source device. It is the figure which showed the electrode arrangement | positioning in a discharge tube. It is the figure which showed the positional relationship of a lamp | ramp center axis | shaft and a reflector center axis | shaft. It is the graph which showed the lamp | ramp electric power accompanying lamp | ramp lighting time progress. It is a front view of the light source device in 2nd Embodiment. It is a schematic sectional drawing of the light source device in 2nd Embodiment. It is a schematic sectional drawing of one light source device which is 3rd Embodiment. It is the figure which showed the flowchart of the lamp lighting control at the time of the lamp lighting start in 4th Embodiment. It is the flowchart which showed the light control process performed by the controller in 5th Embodiment. It is the figure which showed the light control filter data. It is the figure which showed the light control filter data. It is the graph which showed the light quantity of the projection light, input power, and the usage rate of DMD with the use time passage of a discharge lamp. It is the flowchart which showed the drawing process by a step & repeat system. It is the figure which showed the change of the DMD usage rate and lamp electric power in 6th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of an exposure apparatus according to the first embodiment. FIG. 2 is a block diagram of the exposure apparatus.
The exposure apparatus 10 is a maskless exposure apparatus that directly forms a pattern on a substrate W on which a photosensitive material such as a photoresist is formed. The exposure unit 13 mounted on the base 14 includes a discharge lamp 22. And an exposure head 30 including a DMD (Digital Micro-mirror Device) 32.
The substrate W is mounted on the stage 12, and the stage 12 can be moved by the stage driving mechanism 15. Here, it is movable along the scanning direction X and the sub-scanning direction Y, and XY coordinates are defined on the stage 12.
Light emitted from the discharge lamp 22 is guided to the DMD 32 by an illumination optical system (not shown). The DMD 32 is a light modulation element array (here, 1024 × 1280) in which micro rectangular micromirrors of several μm to several tens μm are two-dimensionally arranged in a matrix, and is driven by the DMD driving circuit 24.
Vector data such as CAD / CAM data transmitted from a workstation (not shown) is converted into raster data of a two-dimensional dot pattern by the raster conversion circuit 26. Then, the exposure data generation circuit 28 generates exposure data obtained by synthesizing the dimming filter data serving as the mask pattern and the raster data as necessary.
In the DMD 32, each micromirror is selectively ON / OFF controlled based on the exposure data sent from the DMD drive circuit 24. The light reflected by the micromirror in the ON state is irradiated onto the substrate W as light of a pattern image through a projection optical system (not shown).
When the substrate W is moved in the scanning direction X by the stage drive mechanism 15, the projection area (exposure area) by the DMD 32 moves relative to the substrate W. While moving the exposure area relative to the XY direction, The pattern is formed on the entire substrate W by performing the exposure operation at a predetermined exposure pitch. The position of the substrate W, that is, the position of the exposure area is detected by the position detection sensor 17.
The exposure apparatus 10 includes a photometric device 34 that measures the amount of light projected on the stage 12, and the position is controlled by a photometric drive unit 35. When the exposure operation is not performed, the photometric drive unit 35 arranges the photometric device 34 on the optical path, and moves the photometric device 34 to the retracted position when the measurement is completed. However, it is also possible to attach the photometric device 34 to the stage 12 and measure the amount of light as the substrate W moves.
The controller 50 controls the entire exposure operation such as exposure data generation timing, DMD drive, and the like. When data related to light control is read from the memory 52, light control filter data is sent to the exposure data generation circuit 28. A control program for the exposure operation is stored in a ROM (not shown) in the controller 50.
The controller 50 has a dimming process (illuminance / light quantity adjustment process) function, and executes the dimming process by combining mirror control for the DMD 32 and output control for the discharge lamp 22. During the life cycle of the discharge lamp 22, that is, the entire period from the start of lighting (initial lighting) to the end of lighting based on the lamp life, the controller 50 executes mirror control and lamp output control based on the measured light quantity. The amount of light projected / irradiated on the substrate W is adjusted.
FIG. 3 is a plan view of the light source device. FIG. 4 is a schematic cross-sectional view of the light source device.
The discharge lamp 22 of the light source device 20 is a short arc type mercury lamp composed of a spherical discharge tube 22A located at the center and a pair of sealing portions 22B integrally connected to both ends thereof, and a pair of electrodes 23A. , 23B are disposed opposite to each other in the discharge tube 22A. When the central axis (not shown) of the reflecting mirror 21 is in the horizontal direction, the discharge lamp 22 is arranged along the horizontal direction.
In the discharge tube 22A, together with a rare gas and a halogen, 0.2 mg / mm ³ Contains more mercury. When the lamp is lit, an AC voltage is applied to the electrode pair 23A and 23B, and the cathode and the anode are alternately switched between the electrode pair 23A and 23B.
The reflecting mirror 21 is a saddle type mirror in which a concave reflecting portion 21A and a cylindrical neck portion 21B are integrally formed, and the reflecting surface 21S of the reflecting portion 21A is formed on a rotating paraboloid having a focus. . As will be described later, the discharge lamp 22 has an offset coaxial arrangement with respect to the reflecting mirror 21, and is fixed by a holding member MS disposed between the neck portion 21B and the base 25 connected to the discharge lamp 22. Has been. It is possible to fix the discharge lamp 22 with an adhesive or the like.
FIG. 5 is a diagram showing the electrode arrangement in the discharge tube. FIG. 6 is a diagram showing the positional relationship between the lamp center axis and the reflector center axis. The arrangement of the discharge lamp will be described with reference to FIGS.
The electrode pairs 23A and 23B are supported by electrode support bars 27A and 27B, and the electrode pairs 23A and 23B are fused and integrated with the electrode support bars 27A and 27B, respectively. The electrode tip portions 29A and 29B of the electrode pairs 23A and 23B are formed along the electrode support rods 27A and 27B, and arc discharge occurs between the electrode tip portions 29A and 29B.
The positions of the electrode pairs 23A, 23B and the electrode support rods 27A, 27B are adjusted so that their electrode axes coincide with the lamp central axis E, that is, the central axis of the cylindrical sealing portion 22B. Therefore, the positions of the electrode tip portions 29A and 29B are also along the lamp central axis E.
As described above, since the cathode and the anode are alternately switched between the electrodes 23A and 23B, the bright spot of the arc discharge is also alternately switched between the electrode tip portions 29A and 29B. Therefore, arc discharge occurs around the lamp center axis E when the lamp is started.
However, since the discharge lamp 22 is disposed along the horizontal direction, gas convection occurs in the discharge tube 22A during lamp operation. In the vicinity of the electrode tip portions 29A and 29B, an upward flow of gas is generated from the vertically lower side to the vertically upper side in accordance with a halogen cycle such as halogen enclosed with a rare gas. As a result, a temperature difference is generated between the vertically upper side and the lower side of the discharge tube 22A.
Due to this temperature difference, gas convection becomes even more intense, and the electrode tip portions 29A and 29B are deformed and move vertically upward. The temperature difference affects the deformation amount of the electrode tip portions 29A and 29B, and the deformation amount of the electrode tip portions 29A and 29B increases as the temperature difference increases.
In the present embodiment, the lamp center axis E of the discharge lamp 22 does not coincide with the center axis T of the reflecting mirror 21 and is arranged vertically below the predetermined distance d in parallel with the offset. The predetermined distance d is set to a length of 5 to 45% with respect to the diameter D of the electrode support rods 27A and 27B. In particular, it is desirable to set it in the range of 10 to 35%, further 20 to 25%, for example, 22%. However, the diameter D of the electrode support rods 27A and 27B is determined in the range of 0.3 to 0.6 mm.
Regarding the position of the discharge lamp 22 with respect to the lamp center axis E, the position of the discharge lamp 22 is determined so that the arc bright spot exists at a position moved by a distance d along the vertically downward direction from the focal point FP of the reflecting mirror 21. ing. Here, the focal point FP is positioned at a distance d along the direction perpendicular to the central axis T of the reflector from the arc bright spot generation point (vertex) of the electrode tip portion 29B.
As described above, the discharge lamp 22 is not completely coaxially disposed with respect to the reflecting mirror 21 but is offset so that the lamp life can be extended. Hereinafter, a description will be given with reference to FIG.
FIG. 7 is a graph showing the lamp power as the lamp lighting time elapses.
During constant illuminance control, the lamp power is increased in order to compensate for fluctuations in the arc luminescent spot due to deformation of the electrode tip portions 29A and 29B and a decrease in illuminance. The increase rate can be regarded as substantially constant.
Since the discharge lamp 22 is offset from the lamp center axis E with respect to the center axis T of the reflector 21, the lamp center axis E and the reflector center axis T coincide with each other when the lamp is initially started. It is lit at the initial limit power W1 having a larger power value than when the power is set. However, the initial limit power W1 represents the minimum power value at which the occurrence of flicker is suppressed. FIG. 7 also shows the initial limit power W0 when the discharge lamp 22 is arranged completely coaxially with the reflecting mirror 21.
If the discharge lamp 22 is continuously lit for a long time, the electrode tip portions 29A and 29B are deformed vertically upward as time elapses, and the position of the arc bright spot is moved vertically upward, before reaching the pre-lamp life. The arc bright spot arrives on the central axis T of the reflecting mirror 21 in the middle stage. When the lamp life is near, the arc bright spot moves further vertically above the central axis T.
Unlike the conventional lamp, the arc luminescent spot does not move away from the focal position with the passage of time, but the arc luminescent spot approaches the focal position halfway and then leaves. Although the lamp power inevitably increases due to the exhaustion of the discharge tube or the like, the increase in illuminance due to the vertical movement of the arc bright spot suppresses the overall decrease in illuminance. As a result, the increase rate of the supplied lamp power is reduced. In FIG. 7, a change in lamp power of a conventional discharge lamp is indicated by a line k0, and a change in power according to the present embodiment is indicated by a line k1.
Therefore, even if the initial limit power is relatively large, the increase rate of the lamp power is suppressed, and as a result, the lamp life is extended. However, as described above, the offset distance d of the lamp center axis E from the reflector center axis T is set in a range of 5 to 45% of the diameter D of the electrode support rods 27A and 27B. The size of the electrode tip, that is, the diameter D of the electrode support rods 27A and 27B is set to 0.3 to 0.6 mm.
If the offset distance d is too large, the initial limit power becomes larger than necessary, and the discharge tube is consumed and the tip of the electrode is deformed very quickly, resulting in an early decrease in illuminance. In addition, when the arc bright spot moves to the central axis T of the reflector, arc discharge occurs near the top of the discharge tube, and there is a risk of the discharge tube being deformed by heat.
On the other hand, if the offset distance d is too small, the initial limit power is not different from that of the conventional lamp, and the lamp life is not extended. Further, if the diameter D of the electrode support rods 27A and 27B is too small, the electrode is likely to be deformed. If the diameter D is too large, the position of the arc bright spot is likely to fluctuate.
As described above, according to the present embodiment, in the light source device 20 including the discharge lamp 22 arranged along the horizontal direction and the reflecting mirror 21 whose reflecting surface is a rotating paraboloid, the discharge lamp 22 is the reflecting mirror. On the other hand, the lamp central axis E is arranged in parallel at a distance d from the reflector central axis T along the vertical direction.
Next, a second embodiment will be described with reference to FIGS. In the second embodiment, an opening is formed in the reflecting mirror. About another structure, it is the same as 1st Embodiment.
FIG. 8 is a front view of the light source device according to the second embodiment. FIG. 9 is a schematic cross-sectional view of the light source device according to the second embodiment.
The light source device 20 includes a reflecting mirror 121, and the discharge lamp 22 is offset along the central axis. A rectangular opening 121 </ b> A is formed on the vertically lower side of the reflecting mirror 121. Note that the opening 121A may have other shapes.
During the lamp operation, the influence of the arc discharge heat is dominant in the temperature above the discharge tube. On the other hand, the temperature on the lower side is also affected mainly by the heat of arc discharge, but in addition, it is also affected by the radiant heat of the reflecting mirror. Since the discharge lamp 22 is offset vertically downward, the temperature on the discharge tube vertically lower side reduces the distance between the reflector that reflects radiant heat with high efficiency and the discharge tube vertically lower portion. It is greatly affected and the temperature rises.
In the second embodiment, since the opening 121A is formed in the vertically lower part of the reflecting mirror 121, the temperature of the lower part of the discharge tube is not approached by the reflecting mirror, and thus the influence of radiant heat is suppressed. As a result, the temperature difference between the discharge tube lower side and the discharge tube upper side increases. This intensifies gas convection in the discharge tube and increases the amount of deformation of the electrode tip, that is, the amount of movement of the arc bright spot.
As a result, it is possible to set the offset distance interval of the discharge lamp 22 as long as possible, and it is possible to increase the initial limit power at the initial lamp start.
Next, an exposure apparatus according to the third embodiment will be described with reference to FIG. In the third embodiment, four light source devices having openings in four directions are arranged adjacent to each other. About another structure, it is the same as 1st Embodiment.
FIG. 10 is a schematic cross-sectional view of one light source device according to the third embodiment.
The light source device 20 is an assembly structure in which the above-described four light source devices are prepared and assembled in a square shape. The light source device 20 has a right side (or left side), a vertically lower side, and a diagonally lower side along the horizontal direction of the light source device 20 shown in FIG. Three light source devices (not shown) are arranged adjacent to each other.
And the reflective mirror 221 of the light source device 20 is formed with openings of the same shape at substantially equal intervals in the upper, lower, left and right directions. In FIG. 10, only one opening is illustrated. With this configuration, heat from the reflecting mirror outer surface side of the adjacent light source device can be suppressed, and temperature rise on the discharge tube vertical lower side can be suppressed. That is, the temperature difference between the upper part and the lower part of the arc tube is widened, and the arc bright spot moving amount can be increased.
Next, a fourth embodiment will be described with reference to FIG. In the fourth embodiment, the lamp power at the initial start is adjusted.
FIG. 11 is a diagram showing a flowchart of lamp lighting control at the start of lamp lighting.
In step S101, the light quantity is measured and a target light quantity is set. The target light amount represents a minimum light amount within a range where flicker does not occur, and is set in advance by an operator or the like. Then, the discharge lamp is driven by the power value (initial limit power value) corresponding to the target light amount.
When it is confirmed that the measured light quantity is equal to or more than the target light quantity, the discharge lamp is driven with a power value W2 that is larger than the initial limit power value by a predetermined value in order to further increase the lamp output (S102, S103). ). This power value W2 is determined based on the offset distance d from the central axis of the reflector of the discharge lamp.
In the case of a multi-lamp type light source device, the initial limit power value varies depending on individual differences of lamps. Therefore, a power value larger than the initial limit power value that is the maximum value is supplied.
Thus, according to the fourth embodiment, the discharge lamp 22 arranged along the horizontal direction and the reflecting mirror 21 whose reflecting surface is a rotating paraboloid are provided, and the discharging lamp 22 is the center of the reflecting mirror 21. On the other hand, in the light source device in which the lamp center axis E is arranged in parallel at a distance d along the vertical direction from the reflector center axis T, the lamp is turned on with a power value larger than the initial limit power. The
Since the discharge lamp is offset with respect to the reflecting mirror, the power increase rate is low when the lamp is lit for a long period of time and controlled for constant illumination. Therefore, even if the lamp power at the initial start is set large, the period until the lamp life is extended. On the other hand, since the lamp initial power is high, the lamp quickly shifts to a stable lighting state while reliably suppressing flickering.
Thus, by setting a value that exceeds the previously set minimum power value, it is possible to reliably prevent the occurrence of flickering at the initial lamp start and to extend the lamp life. In particular, in the case of a multi-lamp light source device, flickering can be reliably prevented regardless of individual lamp differences.
Next, a fifth embodiment will be described with reference to FIGS. In the fifth embodiment, dimming processing that combines the light amount adjustment of the projection light by the DMD and the illumination light amount adjustment by the lamp output control is periodically performed.
FIG. 12 is a flowchart showing the dimming process executed by the controller.
There are various timings for the dimming process, such as when a new discharge lamp is installed, when processing a substrate of a photosensitive material with a different sensitivity, and for each lot (product unit), when a certain number of substrates are processed, every certain period It is also possible to perform a dimming process. Here, dimming processing is executed at regular intervals.
When the dimming process is started by a user input operation or the like, the photometry device 34 moves on the optical path while the discharge lamp 22 is lit, and the light quantity is measured (S201). At this time, all the mirrors (hereinafter referred to as effective mirrors) that can be used for drawing in the DMD 32 are turned on, and the amount of light is measured.
Therefore, in the photometry device 34, the light amount of the light in the state where all the effective mirrors are in the ON state is measured for the projection area (exposure area). The effective mirror refers to a mirror excluding all mirrors of the DMD that are previously determined not to be used for drawing (such as a mirror at the periphery of the DMD).
After the light amount is measured, it is determined whether or not the measured light amount is equal to or greater than a predetermined light amount (hereinafter referred to as a target light amount) (S202). If it is determined that the measured light quantity is equal to or greater than the target light quantity, the ratio of mirrors actually used for drawing (hereinafter referred to as usage ratio) in the entire effective mirrors of the DMD 32 is calculated (S204).
When the usage rate is 100%, the entire effective mirror constituting the drawing area is in the ON state, and the usage rate decreases as the number of mirrors set to the OFF state increases (the number of used mirrors decreases). The light control processing here is to match the amount of light projected onto the substrate W with the target amount of light, and the degree of dimming, that is, the usage rate is determined based on the measured amount of light.
Here, when the mirror usage rate is R, the light quantity measured in the effective mirror total number ON state is L1, and the target light quantity is L0, the usage ratio R is obtained by the light quantity ratio (R = L0 / L1). When the usage rate R is determined, a mirror that is not used at the time of drawing, that is, a mirror that is turned off regardless of the pattern is specified and set (S204). At this time, in order to reduce the amount of light projected onto the substrate W as a whole, not locally, the light is extracted so as not to be substantially uniform and regular when viewed from the entire effective mirror of the DMD.
Specifically, the unused mirrors are determined so that the unused mirrors have a substantially two-dimensional distribution in the entire mirror region. That is, the arrangement of the unused mirrors is determined so that the unused mirrors are arranged at substantially equal distance intervals within the effective mirror area of the DMD 32 and are arranged in a state where the unused mirrors are uniformly scattered without local concentration. Is done.
Furthermore, in addition to the substantially uniform distribution, in order to prevent moiré due to light interference, the unused mirrors are arranged randomly rather than regularly and periodically. In order to maintain such a substantially uniform distance interval and to select an irregular unused mirror, a pseudo random number is used here. For example, it is possible to generate a random number based on an improved Römer method using uniform random numbers.
In such a pseudo-random number, if the number of effective mirrors is N and the number of unused mirrors is n (= N (1-R)), pseudo-random numbers are selected from the effective mirrors M1, M2,. Use and select unused mirrors. An unused mirror is determined by repeating this n times. At this time, the unused mirror is determined from the entire effective mirror regardless of the pattern data.
However, when a predetermined number of mirrors already extracted are selected again, unused mirrors are extracted again. If a predetermined number of mirrors adjacent to each other among the mirrors extracted as unused mirrors exist, the selection is invalidated and the unused mirrors are extracted again. The number of adjacent mirrors that invalidate unused mirrors is adjusted according to the usage rate.
In this way, data representing the array of unused mirrors (herein, dimming filter data) is calculated and created based on the usage rate R, and the dimming filter data is stored in the memory 52 (S206).
13A and 13B are diagrams showing dimming filter data. FIG. 13A shows dimming filter data when all effective mirrors are used. The black part represents the mirror ON state, and the area is black because the usage rate is 100%.
On the other hand, FIG. 13B shows dimming filter data in which the usage rate R = 80%, that is, the ratio of unused mirrors is 20%. As is apparent from FIG. 13B, the unused mirrors are distributed in a substantially uniform distribution with respect to the mirror area at substantially equal distance intervals. On the other hand, when viewed from the entire mirror area, the unused mirrors have a regular arrangement. is not.
As described above, the light amount of the projection light is uniformly adjusted in the entire projection area by the dimming filter data corresponding to the usage rate. By superimposing the light control filter data and the pattern data for drawing, it is possible to form a pattern with a light amount reduction in the projection area. The dimming filter data does not depend on the pattern data.
On the other hand, when the light amount measured in step S103 is less than the target light amount, the light amount adjustment using the DMD 32 cannot be performed. That is, the measured light quantity does not reach the target light quantity even when all the effective mirrors are in the ON state, and therefore cannot be matched with the target light quantity by selecting the unused mirror.
This is a decrease in output as the discharge lamp 22 is used and occurs after a relatively long lighting time. In such a state, the input power to the lamp is adjusted so that the output of the discharge lamp 22 is increased (S203).
Specifically, the lamp input power is adjusted so that the amount of illumination light from the discharge lamp 22 becomes a reference amount of light that is a predetermined amount greater than the target amount of light. For example, the lamp input power is increased until the measured light quantity reaches 120% of the target light quantity. Then, dimming filter data is created again. Once the output of the discharge lamp 22 is adjusted, the input power is kept constant until the measured light quantity falls below the target light quantity again.
FIG. 14 is a graph showing the amount of projection light, input power, and usage rate of DMD with the passage of time of use of the discharge lamp.
As shown in FIG. 14, the input power (initial power) at the start of use of the discharge lamp 22 is set to the power W <b> 1 that obtains a reference light amount higher than the target light amount. While maintaining this input power constant, the light amount of the projection light is adjusted to the target light amount L0 by light amount adjustment (dimming) using the DMD 32.
During the lighting of the discharge lamp 22, the output of the discharge lamp 22 may fluctuate finely, and the mirror usage rate increases or decreases accordingly. However, as the lighting time becomes longer, the output of the discharge lamp 22 gradually decreases. Along with this, the mirror usage rate gradually increases.
When the measured light quantity falls below the target light quantity L0, the lamp input power is increased, and the input power is increased by VD until the reference light quantity is reached again. While maintaining the newly set input power, the mirror usage rate is calculated to adjust the light amount.
As a result, as shown in FIG. 14, the mirror usage rate increases toward 100% and finally reaches almost 100% while increasing or decreasing the lamp input power for a certain period, and this is repeated. Note that the light amount when the mirror usage rate is 100% is indicated by a two-dot chain line L1 in FIG.
In this way, while performing the dimming process using the DMD at predetermined time intervals, the lamp input power is increased stepwise in a span longer than the DMD dimming process time interval, and finally the maximum power that becomes the upper limit Up to. From the start of use of the discharge lamp 22 to the end of use due to its life, the light quantity and illuminance with respect to the projection area of the substrate W are always maintained at the target light quantity L0 suitable for drawing.
By the way, considering the resolution required for the pattern, there is a limit to dimming using the DMD 32, and it is necessary to set a lower limit for the usage rate R. The lower limit value of the usage rate R is determined by the tilt angle of the DMD 32, the number of pixels, the pixel size, the magnification of the projection optical system, the resolution, the sensitivity of the photoreceptor, and the like. Here, an adjustment range in which there is no difference in the required resolution is determined, and the lower limit value RZ of the usage rate R is set to 65%.
Therefore, when the output of the discharge lamp 22 is increased, it is necessary that the usage rate R does not become lower than the lower limit value RZ = 65%. In the present embodiment, the reference light amount referred to when the output increases corresponds to the lower limit value RZ, and the usage rate R decreases to the lower limit value RZ each time the lamp output increases. As a result, the light amount adjustment range in which the usage rate R is the lower limit value RZ = 65% to 100% is used during the increase of the lamp output.
Further, in the present embodiment, the discharge lamps 22 are arranged offset as in the first embodiment. Therefore, although the electric power W1 at the time of initial start is larger than the initial start electric power W0 when the discharge lamp is not offset, the decrease in illuminance can be suppressed by moving the arc bright spot vertically upward. As a result, the rate of increase in the DMD usage rate is suppressed, and accordingly, the fixed power period until switching to the next power value becomes longer.
Furthermore, since the arc bright spot approaches the reflection axis with time, the amount of power increase ΔV until reaching the reference light amount that is higher than the target light amount is smaller than in the prior art. As described above, the lamp life period is greatly extended by expanding the power constant period and suppressing the power increase. In FIG. 14, a change in light amount, a change in power, and a change in DMD usage rate when the discharge lamps are not offset are indicated by a two-dot chain line.
Note that the constant power period may be shortened by further reducing the DMD usage rate in order to further suppress a single power increase.
FIG. 15 is a flowchart showing drawing processing by the step & repeat method.
While the substrate W moves, the relative position of the projection area (exposure area) is detected, and when the exposure area reaches the area on the substrate on which the pattern corresponding to the generated pattern data is to be projected, the substrate W stops ( S301 to S303). Then, raster data is generated from the vector data (S304).
When the dimming filter data is read from the memory 52, exposure data is generated by superimposing (logical product) the raster data and the dimming filter data (S305, S306). The exposure light is sent to the DMD driving circuit 24, and thereby pattern light is projected (S307). Such exposure operation is repeated until drawing is completed (S308, S309).
As described above, according to the present embodiment, when adjusting the light amount, the effective mirror of the DMD 32 is turned on, the light amount of the projection light is measured, and the usage rate R that is the ratio between the measured light amount and the target light amount is determined. . Based on the usage rate R, dimming filter data indicating an array of unused mirrors is generated. At this time, the unused mirrors are arranged in a substantially uniform distribution and irregularly.
While the light intensity adjustment using the DMD 32 is performed, if the output of the discharge lamp 22 gradually decreases and the measured light quantity does not reach the target light quantity, the discharge is performed until the measured light quantity reaches a reference light quantity that is a predetermined amount larger than the target light quantity. The output of the lamp 22 is increased.
The light intensity adjustment for the entire exposure target area is performed by the DMD 32, and the lamp output is increased only when the DMD 32 cannot adjust the light intensity (the light intensity cannot be increased), so that the lamp life cycle is not adversely affected without adversely affecting the lamp life. A good light quantity adjustment can be performed over the entire area. In addition, the lamp output can be adjusted without frequent changes to the fluctuation of the short-term span of the lamp output caused by fluctuations in the discharge during lamp operation and non-linkable fluctuations in the emission spectrum distribution across the bright line and the entire broadband. can do.
In particular, since the array of unused mirrors is a two-dimensionally substantially uniform distribution with no regularity over the entire exposure target area, optical phenomena such as moire are also caused by two-dimensional dot irradiation. It is possible to realize a uniform light amount reduction over the entire exposure target area without occurring.
In the present embodiment, when the measured light quantity does not reach the target light quantity, the output of the discharge lamp 22 is increased. However, the timing at which such a situation occurs is empirically acquired in advance, and the discharge lamp 22 is output every predetermined time. An output increase may be performed. As for the output increase of the lamp, whether or not the measurement light quantity has reached the target light quantity is confirmed by the measurement device, but the input power may be increased by a predetermined constant value.
The ratio of mirrors used in the light amount adjustment using the DMD 32, that is, the usage rate, can be set in a range that satisfies any of the requirements in the exposure conditions. The range of the usage rate depends on the size of the DMD, the pixel pitch, the resolution, the DMD tilt angle, the number of times of multiple exposure of the photosensitive member such as a photoresist, and the like. For example, it can be set in the range of 20% to 100%.
The usage rate of the used mirror can be set stepwise (for example, 5%) according to the required light amount accuracy instead of being set continuously. The dimming filter data may be created in advance according to the usage rate and stored in the memory, and the corresponding dimming filter data may be selected from the ratio between the measured light amount and the target light amount.
Next, a sixth embodiment will be described with reference to FIG. In the sixth embodiment, the power is increased by causing DMD to function as a mask as in the fifth embodiment for a certain period from the start of lamp lighting start. Then, after a certain period of time, constant illuminance lighting control is performed as in the first embodiment.
FIG. 16 is a diagram showing changes in the DMD usage rate and lamp power in the sixth embodiment.
As shown in FIG. 16, in order to increase the lamp power for a certain period (power increase period) from the start of lamp start, the DMD usage rate D1 is set so that electric power larger than the initial limit power without flickering is supplied. It has been established. The usage rate D1 is smaller than the usage rate D2 when the discharge lamps are arranged coaxially as in the prior art, and the projection light is greatly reduced. In the power augmentation period, the DMD usage rate D1 does not change and is constant.
On the other hand, when a multi-lamp light source device having a plurality of discharge lamps, that is, a plurality of lamp units, is used, the usage rate D1 is determined so that power larger than the largest initial limit power value is supplied. It is done.
In order to perform constant illuminance control, the lamp power is set to a large value immediately after the start of the lamp, but the arc bright spot approaches the central axis of the reflector over time, so the power increase rate is higher than that of the conventional discharge lamp. It can be suppressed. In FIG. 16, the power change in the present embodiment is indicated by a practice line K4, and the power change in the conventional discharge lamp is indicated by a broken line K3.
As described above, the DMD is used to reduce the amount of projection light, and accordingly, the power is increased by the constant illuminance lighting control, and the power can be increased while maintaining a constant illuminance.
After a certain period of time when the power is increased, the DMD usage rate is set to 100%. As a result, the power decreases simultaneously with the DMD usage rate change. However, since the power increase width in a certain period is small, the power decrease width is also smaller than the conventional one. As a result, it is possible to prevent instability and flickering of the constant illuminance lighting control that accompanies rapid power reduction. After a certain period of time, constant illuminance lighting control similar to that in the first and second embodiments is performed.
Thus, according to the sixth embodiment, the discharge lamp 22 arranged along the horizontal direction and the reflecting mirror 21 whose reflecting surface is a rotating paraboloid are provided, and the discharge lamp 22 is the center of the reflecting mirror 21. In an exposure apparatus provided with a light source device in which the lamp center axis E is arranged in parallel by a distance d from the reflector center axis T along the vertical direction, a predetermined power from the start of the lamp is provided. In the augmentation period, the DMD usage rate D1 is determined and the DMD functions as a mask / filter. And electric power is increased so that it may become fixed illumination intensity.
Note that the power value immediately after the start of the lamp start may be determined based on the light amount of the projection light and the target light amount at the usage rate of 100% detected as in the fifth embodiment.
A continuous scanning method may be applied instead of step & repeat. Further, instead of the multiple exposure method, a method of performing a single shot exposure may be used. Furthermore, a light modulation element array other than DMD may be used, and a light source other than a discharge lamp can be applied. Further, in an exposure apparatus using a mask and a reticle, a light modulation element array such as a DMD may be separately provided as a dedicated filter device.
Various changes, substitutions and alternatives are possible with respect to the present invention without departing from the spirit and scope of the present invention as defined by the appended claims. Furthermore, the present invention is not intended to be limited to the specific embodiments of the processes, apparatus, manufacture, components, means, methods, and steps described in the specification. Those skilled in the art will appreciate from the disclosure of the present invention devices, means, and methods that perform substantially the same functions as those provided by the embodiments described herein, or that provide substantially the same operations and effects. You will recognize it. Accordingly, the appended claims are intended to be included within the scope of such devices, means, and methods.
This application is an application that claims priority as a basic application of Japanese applications (Japanese Patent Application Nos. 2013-081666, 2013-081663, 2013-081670, filed on April 9, 2013). The disclosure, including the specification, drawings and claims, is hereby incorporated by reference in its entirety.

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 20 Light source apparatus 21 Reflector 22 Discharge lamp 50 Controller (light quantity adjustment part, illumination control part)

Claims (6)

A plurality of light source devices each having a discharge lamp and a reflecting mirror are adjacent to each other,
The discharge lamp has an electrode pair disposed opposite to each other in the discharge tube so that the electrode axis coincides with the lamp central axis;
The reflecting mirror has a concave reflecting surface having a focal point, and guides light from the discharge lamp in one direction;
By adjusting the electric power of the discharge lamp, with an illumination control unit for controlling the constant illuminance lighting,
The discharge lamp is disposed along the central axis of the reflector, and is disposed along the horizontal direction.The lamp central axis is located vertically below the central axis of the reflector,
The discharge lamp is spaced apart from a reference position corresponding to the focal point of the reflector by an arc bright spot at the time of starting the discharge lamp by a predetermined distance interval along a direction perpendicular to the central axis of the reflector,
In the reflecting mirror, openings having the same shape are formed at substantially equal intervals in the four directions of up, down, left and right from the central axis of the reflecting mirror,
The lighting control unit, when the lamp initial startup, the larger power value than the maximum of the initial limit power value among the plurality of discharge lamps respective initial limit power value that does not generate flicker, driving the discharge lamp,
The lighting control unit determines a power value larger than a maximum initial limit power value among the initial limit power values of each of the plurality of discharge lamps based on the predetermined distance interval when the lamp is initially started. Light source device.   The light source device according to claim 1, wherein the light source device is a multi-lamp type light source device in which four light source devices are arranged in a square shape. The diameter of the electrode support rod supporting the electrode pair is in the range of 0.3 to 0.6 mm;
The light source device according to claim 1, wherein the lamp central axis is separated from the central axis of the reflector by a distance of 5 to 45% of the electrode support rod diameter.   4. The light source device according to claim 3, wherein the lamp central axis is separated from the central axis of the reflector by a distance interval of 20 to 25% of the electrode support rod diameter. The light source device according to claim 1, wherein the discharge lamp contains 0.2 mg / mm ³ or more of mercury.   The light source device according to claim 1, wherein the opening formed in the reflecting mirror includes an opening formed in a vertically lower portion.

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