KR102413894B1 - Exposure device - Google Patents

Abstract

An exposure apparatus WHEREIN: The in-focus state is detected or confirmed simply and accurately.
A light amount signal is output from the photosensor PD by projecting the pattern column PT composed of the bar-shaped patterns PL1 to PL4 onto the light shielding portion 40 formed in the slits ST1 to ST6 while moving the stage 12 . Then, based on the amplitude ratio M obtained from the light amount signal, it is determined whether the in-focus state is maintained.

Description

Exposure apparatus {EXPOSURE DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for forming a pattern using an array of light modulation elements or the like, and more particularly, to focus detection.

In a maskless exposure apparatus, pattern light is projected onto a substrate by means of a light modulation element array such as a digital micro-mirror device (DMD) while moving a stage on which the substrate is mounted in the scanning direction. There, the light modulation elements (micromirrors, etc.) arranged in a two-dimensional image are controlled so as to project pattern light according to the position of the projection area (exposure area) on the board|substrate mounted on the stage.

In order to adjust the focal position of the pattern light on the upper surface of the substrate on which the photosensitive material is applied or pasted, the focus is adjusted before exposure. For example, during focus adjustment, the DMD projects light in a line & space pattern (L/S pattern) according to a period close to the resolution limit of the projection optical system while moving the focus lens in the optical axis direction. A CCD camera is installed below the projection optical system, and when the CCD camera receives pattern light, a contrast-related value of the L/S pattern is calculated by image processing. And the peak detection position is set as the in-focus position, and the board|substrate position is adjusted (refer patent document 1).

The focal position of the optical system of the exposure apparatus may change with time. Therefore, even if focus adjustment is performed once, there exists a possibility that a focus position may deviate from a focus position. In particular, in recent years, since the depth of focus tends to become shallow as the pattern is refined, it tends to deviate from the in-focus position. Therefore, the beam projected onto the dummy substrate is observed with the observation camera, the position of the focusing lens at which the contrast is maximized is set, and the distance (reference distance) between the substrate and the optical system at that position is elapsed. A calibration operation to adjust according to changes is performed (see Patent Document 2).

On the other hand, in the exposure apparatus, if an output fall occurs due to the life of the light source, the required exposure amount cannot be obtained. In addition, there is a case where a light intensity irregularity occurs locally due to a malfunction or the like of the micromirror of the DMD. In order to determine whether or not the amount of light satisfies specification conditions or the like, a light amount sensor is installed in the exposure apparatus, and pattern light for measurement is projected before exposure to detect the amount of light (refer to Patent Document 3).

There, a photo sensor for directly measuring the amount of light from the light source, a light intensity sensor for measuring the amount of light irradiated to the substrate, and a photosensor for measuring the reflected light of the DMD are provided in the exposure apparatus. When irradiating the output characteristics of the light source, the amount of light is detected by a photo sensor disposed between the light source and the DMD. On the other hand, when examining the optical properties of the DMD and the optical properties of the projection optical system, the photosensor provided on the drawing table receives the pattern light in the case where each micromirror is turned on.

Japanese Patent Application Laid-Open No. 2009-246165 Japanese Patent Laid-Open No. 2013-77677 Japanese Patent Laid-Open No. 2008-242173

If any disturbance (change) occurs in the stage mechanism of the exposure apparatus or the arrangement structure of the projection optical system, the position of the exposure surface will deviate from the focusing (focus) range. In particular, since the depth of focus becomes shallower as the pattern becomes finer, the possibility that the exposure apparatus is used for a long period of time increases the possibility that the focus is shifted.

Therefore, it is preferable to confirm that the position of the substrate is in the in-focus range at a timing such as before the start of exposure. For example, it is possible to form a pattern on the board|substrate for a test, to visualize, or to image with a camera, and to confirm pattern precision.

However, when a change in the amount of light occurs due to a change in the output of the light source, the appearance of the pattern image changes. Therefore, it is necessary to perform an operation such as focus adjustment, such as movement of the substrate in the optical axis (z-axis) direction or driving the optical system, even in the operation of merely checking whether the in-focus state is not deviating. This entails a long working time for in-focus confirmation, which hinders the improvement of throughput in substrate manufacturing.

Therefore, in the exposure apparatus, it is required to be able to detect or monitor the in-focus state simply and accurately.

On the other hand, depending on the installation conditions of the exposure apparatus, dust, water vapor, or the like adheres to the lens surface due to prolonged use. In addition, since a pattern is formed by irradiating light of high luminance to a substrate molded from a resin or the like, the resin component or the like becomes a gas and adheres to the lens surface. If the imaging performance of the optical system deteriorates as dust or the like adheres to the lens surface, the pattern resolution deviates from the required resolution level.

In the case of transparent deposits such as water vapor, since only the imaging performance deteriorates without a decrease in the amount of light, a decrease in resolution cannot be detected even if the amount of light from the light source is monitored. Therefore, before exposure, it is necessary to confirm in advance whether or not a decrease in resolution is occurring. However, forming a pattern on a substrate for a test and judging the resolution from the formed pattern entails a long working time, which hinders improvement in throughput of substrate manufacturing.

Therefore, in the exposure apparatus, it is required to monitor the resolution performance of the optical system simply and accurately.

On the other hand, when parts such as the DMD and optical system deteriorate due to heat or the like during operation, a decrease in the amount of light partially occurs in a small area of the exposure area at first, and then gradually spreads to the periphery. For example, when the performance of a part is deteriorated due to heat, a decrease in the amount of light first occurs in the center and spreads to the periphery. When performance degradation occurs due to a foreign object such as dust in the air, a decrease in the amount of light occurs in the periphery and spreads to the center.

However, simply by installing a photosensor and detecting the amount of light, it is difficult to determine whether the light amount distribution over the entire exposure area is irradiated, whether it is a local decrease in the amount of light due to component deterioration, etc. or a decrease in the overall light amount due to a decrease in lamp output, etc. . Further, since the measurement interval is limited by the cell size of the light quantity sensor, the detected measured value changes stepwise, and it is difficult to accurately detect the light quantity decrease area.

Therefore, in an exposure apparatus, it is calculated|required to monitor the light quantity fall resulting from deterioration of components etc. simply and accurately.

In the exposure apparatus of the present invention, a light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and an exposure area by the light modulation element array are arranged with respect to an object to be drawn in the main scanning direction A scanning unit for relative movement; an exposure control unit for controlling a plurality of light modulation elements based on pattern data corresponding to the relative positions of the exposure areas; an imaging optical system, a light shielding unit having at least one slit formed along the drawing surface, a light metering unit receiving light passing through the slit, and an in-focus detection unit detecting an in-focus state based on the output of the light metering unit equip

The exposure control unit of the present invention projects line & space (L/S) pattern light while the light shielding unit moves relative to the exposure area. When the L/S pattern light passes through the slit while relatively moving, the amount of wavy light is detected based on the output of the light metering unit. Here, the "waveform light quantity" represents a spatial light quantity distribution in which the light quantity change along the scanning direction periodically becomes wavy. The output of the light metering unit becomes a waveform output with periodicity in time series (referred to as the amount of light in the time series waveform), but a spatial light amount distribution in which the light amount in the time series waveform and the characteristics of the change in light amount correspond to each other can be obtained.

Then, the in-focus detection unit determines whether the image to be drawn is in the in-focus range based on the amplitude of the waveform-like light quantity detected by the projection of the L/S pattern light (that is, the width of the light quantity displacement) and the reference amplitude when in the in-focus range. to detect Here, the "reference amplitude when in-focus range" represents the amplitude of the amount of light in the waveform detected in a state determined to be in-focus based on the depth of focus. By the in-focus determination detection based on the amplitude, the in-focus state can be confirmed without driving the substrate or the optical system. In addition, by looking at the change in amplitude with respect to the reference amplitude instead of the contrast, it is possible to determine in-focus by simpler arithmetic processing.

For example, the in-focus detection unit determines whether or not it is within the in-focus range based on an amplitude ratio that is a ratio between the light amount amplitude and the reference amplitude. It becomes possible to determine in-focus by an easy arithmetic process called amplitude ratio. In particular, when the central light quantity (average light quantity) of the waveform light quantity is the same in the in-focus state and the non-focus state, the in-focus detection unit calculates the average light quantity of the L/S pattern light and the base light quantity when the L/S pattern light is not projected. Based on this, the reference amplitude can be calculated. As for the waveform-like light amount amplitude, the maximum light amount and the minimum light amount (Peak to Peak) may be detected.

The in-focus detection unit can measure the amplitude ratio of each focus position in advance during focus adjustment for driving the optical system or the substrate, and store it in the memory as data for focus detection. In this case, based on the in-focus range determined by the data, it is possible for the in-focus detection unit to determine whether or not it is in the in-focus range. The in-focus range may be determined based on at least one of the sensitivity characteristics of the photosensitive material and the required pattern accuracy.

When calculating the average light quantity, you may provide an exclusive opening part and a light receiving part. For example, the light shielding unit has an average light quantity measurement opening, and the light metering unit has an average light quantity light receiving unit that receives L/S pattern light passing through the average light quantity measurement opening.

In consideration of promptly notifying the operator of an out-of-focus range, it is preferable to provide a holding portion that holds the out-of-focus range when it deviates from the in-focus range.

The exposure apparatus projects the L/S pattern light for exposure position detection while the light-shielding unit moves relative to the exposure area. It is possible. In this case, it becomes possible to perform both exposure position detection and focus detection with the same mechanism.

A focus detection apparatus of an exposure apparatus according to another aspect of the present invention includes a light metering unit for receiving line and space (L/S) pattern light, an amplitude of a waveform light quantity detected by projection of L/S pattern light, and focusing and an in-focus detection unit configured to detect whether or not the image to be drawn is in the in-focus range based on the reference amplitude according to the range. In addition, the focus detection method of the exposure apparatus according to another aspect of the present invention receives line & space (L/S) pattern light, and the amplitude of the amount of wavy light detected by projection of the L/S pattern light, and the focusing range Based on the reference amplitude according to

On the other hand, in the exposure apparatus according to another aspect of the present invention, a light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and an exposure area by the light modulation element array are arranged with respect to the object to be drawn in the main scanning direction A scanning unit for relative movement; an exposure control unit for controlling a plurality of light modulation elements based on pattern data corresponding to the relative positions of the exposure areas; a light-shielding unit having at least one slit formed along the drawing surface, a photometric unit receiving light passing through the slit, and a resolution detecting unit detecting the resolution of the imaging optical system based on an output from the light metering unit to equip

The exposure control unit of the present invention projects line & space (L/S) pattern light while the light shielding unit moves relative to the exposure area. When the L/S pattern light passes through the slit while relatively moving, the amount of light in the waveform is detected based on the output of the light metering unit. Here, the "waveform light quantity" represents a spatial light quantity distribution in which the light quantity change along the scanning direction periodically becomes wavy. The output of the light metering unit becomes a waveform output with periodicity in time series (referred to as the amount of light in the time series waveform), but a spatial light amount distribution in which the light amount in the time series waveform and the characteristics of the change in light amount correspond to each other can be obtained.

And the resolution detection unit, based on the amplitude (that is, the width of the light amount displacement) of the amount of light in the waveform detected by the projection of the L/S pattern light, and the reference amplitude when the resolution is greater than or equal to the predetermined limit resolution, the detected resolution is Detects whether it is lower than the limit resolution. Here, the "reference amplitude when in-focus range" represents the amplitude of the amount of light in the waveform detected in a state determined to be in-focus based on the depth of focus. It becomes possible to detect a decrease in resolution only by detecting the amplitude of the amount of light in the waveform.

For example, the resolving power detection unit may determine whether the resolving power is lower than the limit resolving power based on an amplitude ratio that is a ratio between the detected amplitude and the reference amplitude. The resolution can be monitored by an easy arithmetic process called amplitude ratio calculation.

In particular, when the central light quantity (average light quantity) of the waveform light quantity is the same in both cases with resolution and case with lowering power, the resolution detecting unit determines the average light quantity of L/S pattern light and L/S pattern light when not projected. Based on the base light amount, the reference amplitude can be calculated. As for the amplitude of the amount of light in the waveform, the maximum amount of light and the minimum amount of light (Peak to Peak) may be detected.

The in-focus detection unit can determine whether or not the resolution is lower than the limit resolution based on the correspondence relationship between the amplitude ratio and the resolution of the imaging optical system. For example, data representing the relationship between the resolution and amplitude ratio of the imaging optical system can be stored in the memory at the time of focus adjustment or shipment, etc., and judgment can be made based on the data when detecting the resolution. The limiting resolution of the imaging optical system may be determined based on the optical performance of the imaging optical system.

When calculating the average light quantity, you may provide an exclusive opening part and a light receiving part. For example, the light shielding unit has an average light quantity measurement opening, and the light metering unit has an average light quantity light receiving unit that receives L/S pattern light passing through the average light quantity measurement opening.

Considering that the operator is quickly notified that the in-focus range is out of focus, it is preferable to provide a holding unit that notifies the outside of the in-focus range when the operator is out of the in-focus range.

The exposure apparatus projects the L/S pattern light for exposure position detection while the light-shielding unit moves relative to the exposure area. It is possible. In this case, it becomes possible to perform both exposure position detection and focus detection with the same mechanism.

A resolving power detecting apparatus of an exposure apparatus according to another aspect of the present invention includes a light metering unit for receiving line and space (L/S) pattern light passing through a slit, and a waveform light quantity detected by projection of L/S pattern light. and a resolution detection unit configured to detect whether or not the detected resolution is lower than the limit resolution based on the amplitude and the reference amplitude when the resolution is equal to or greater than the predetermined limit resolution. In addition, the exposure method of the exposure apparatus according to another aspect of the present invention receives line & space (L/S) pattern light passing through a slit, and receives the amplitude and , on the basis of the reference amplitude when the resolving power is greater than or equal to the predetermined limit resolving power, it is detected whether the resolving power is lower than the limit resolving power.

On the other hand, in the exposure apparatus of the present invention in another aspect of the present invention, a light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and an exposure area by the light modulation element array are mainly scanned with respect to a drawing object A scanning unit that moves relative to each other according to the direction; The light amount distribution in the exposure area is detected based on the output from the light metering unit that receives light passing through the narrow and long light metering area that is inclined with respect to the line direction of the pattern, and the light metering unit when the L/S pattern moves relative to the light metering area. and a light quantity detection unit. For example, the light-metering portion has a light-shielding portion in which a slit having a size corresponding to the light-metering area is formed.

In the present invention, the pitch of the L/S pattern is determined so that the light amount of each line-shaped pattern of the L/S pattern is sequentially measured. That is, according to the pitch, the light modulation element used for the projection of the patterned light on the line is determined. Here, "the amount of light is measured in sequence" means that when a pattern on a line passes through the light metering area, the next line pattern does not advance to the metering area, and the change in light amount when each pattern on each line passes through, It indicates that each is measured one by one in order.

For example, what is necessary is just to set the inclination angle with respect to the line direction of a photometric area|region so that the following expression may be satisfied.

Lytanθ < PP

However, Ly represents the length along the sub-scan direction of the L/S pattern, θ represents the inclination angle, and PP represents the pitch of the L/S pattern.

The inclination angle of the photometric region with respect to the line direction may be set to, for example, 37° or 30° or less according to the vertical and horizontal size of the optical modulation element array. For example, the inclination angle θ may be set to 1.2°<θ<2.8°.

The light amount detection unit can determine whether or not the light amount ratio in the exposure area is equal to or less than a predetermined threshold based on the light amount distribution. When the amount of light is equal to or less than the threshold, a holding portion for holding the fact may be provided. Moreover, the light amount detection part can create the light amount distribution graph of an exposure area.

In the exposure method in another aspect of the present invention, an exposure area by a light modulation element array in which a plurality of light modulation elements are arranged in a matrix is relatively moved with respect to an object to be drawn along a main scanning direction, and the plurality of light modulation elements are modulated. By controlling the element, light of a line and space (L/S) pattern arranged along the main scanning direction is projected onto an object to be drawn, and light passing through a narrow and long photometric region inclined with respect to the line direction of the L/S pattern is received. It is an exposure method that detects the light amount distribution of the exposure area based on the output from the light metering unit when the L/S pattern moves relative to the light metering area, so that the light amount of the pattern on each line of the L/S pattern is sequentially measured , the pitch of the L/S pattern is determined.

In another aspect of the present invention, a light metering device for an exposure apparatus is provided on a stage on which an object to be drawn of an exposure apparatus having a light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and sub-scan defined on the stage A light shielding unit having a slit inclined with respect to the direction and a light metering unit for receiving light passing through the slit are provided, and the inclination angle of the slit with respect to the sub-scanning direction is set to 37° or less. In addition, the exposure apparatus operating in conjunction with the light metering apparatus includes a light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and an exposure area by the light modulation element array in the main scanning direction with respect to the object to be drawn. A line and space (L/S) pattern of light arranged in a line along the main scanning direction by controlling a scanning unit to move relative to each other and a plurality of light modulation elements, and having a fixed pitch so that the light amount of each pattern on each line is sequentially measured. An exposure control unit for projecting the to-be-drawn object, and a light quantity detection unit for detecting a light quantity distribution of an exposure area based on the output from the light metering unit are provided.

ADVANTAGE OF THE INVENTION According to this invention, in an exposure apparatus, the in-focus state can be detected or confirmed simply and accurately.

Further, according to the present invention, in the exposure apparatus, it is possible to monitor the resolution performance of the optical system simply and accurately.

Furthermore, according to the present invention, in the exposure apparatus, it is possible to monitor the optical system performance simply and accurately.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the exposure apparatus which is 1st Embodiment.
Fig. 2 is a view showing a light shielding unit and a pattern column for focus adjustment and focus detection.
3 is a schematic side view illustrating an arrangement of a photosensor and a light blocking unit.
FIG. 4 is a graph showing the spatial light quantity distribution and time-series light quantity distribution when light of a single bar-shaped pattern passes through one slit.
5 is a diagram illustrating a graph showing spatial light quantity distribution when light of one bar-shaped pattern passes through one slit.
6 is a diagram illustrating spatial light quantity distribution according to a bar-shaped pattern column.
7 is a diagram illustrating a graph of spatial light quantity distribution having different amplitude ratios.
8 is a graph illustrating a correlation between a focus shift amount and an amplitude ratio.
9 is a diagram showing a flow of in-focus state monitoring processing.
10 is a diagram illustrating a light amount distribution when the resolution performance is maintained and a light amount distribution when the resolution performance is lowered.
11 is a diagram illustrating a graph showing the relationship between the resolution and the amplitude ratio.
12 is a diagram illustrating a spatial light quantity distribution having an amplitude serving as a reference.
Fig. 13 is a diagram showing a flow of monitoring processing for maritime performance.
Fig. 14 is a diagram showing a light-shielding section and a pattern column for measuring light quantity distribution.
15A is a diagram illustrating a process in which one bar-shaped pattern PL1 passes through a slit SL.
15B is a diagram illustrating a process in which one bar-shaped pattern PL1 passes through a slit SL.
15C is a diagram illustrating a process in which one bar-shaped pattern PL1 passes through a slit SL.
15D is a diagram illustrating a process in which one bar-shaped pattern PL1 passes through a slit SL.
16 is a light quantity distribution along the sub-scan direction obtained when one bar-shaped pattern PL1 passes through the slit SL.
17 is a diagram illustrating a movement pitch of a slit according to a light amount detection time interval of a photo sensor.
18 is a diagram illustrating a light amount distribution for each bar-shaped pattern overlaid.
19 is a diagram showing the light quantity distribution over the entire exposure area in three dimensions.
20 is a flowchart showing light amount distribution measurement and warning processing.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

1 is a block diagram of an exposure apparatus according to a first embodiment.

The exposure apparatus 10 is a maskless exposure apparatus that forms a pattern by applying light to a substrate W on which a photosensitive material such as a photoresist is applied or pasted, and the stage 12 on which the substrate W is mounted is movable along the scanning direction. is properly installed. The stage drive mechanism 15 can move the stage 12 along the main scanning direction X and the sub scanning direction Y.

The exposure apparatus 10 includes a plurality of exposure heads that project pattern light (only one exposure head 18 is shown here), and the exposure head 18 includes a DMD 22 and an illumination optical system (not shown). not), and an imaging optical system 23 is provided. The light source 20 is comprised, for example with a discharge lamp (not shown), and is driven by the light source drive part 21. As shown in FIG.

When CAD/CAM data composed of vector data or the like is input to the exposure apparatus 10, the vector data is sent to the raster conversion circuit 26, and the vector data is converted into raster data. The generated raster data is temporarily stored in a buffer memory (not shown) and then sent to the DMD driving circuit 24 .

The DMD 22 is a light modulation element array (light modulator) in which micromirrors are arranged two-dimensionally, and each micromirror selectively switches the reflection direction of light by changing its posture. When each mirror is attitude-controlled by the DMD driving circuit 24, light according to the pattern is projected (imaged) on the surface of the substrate W through the imaging optical system 23 . Thereby, a pattern image is formed on the board|substrate W.

The stage drive mechanism 15 moves the stage 12 according to a control signal from the controller 30 . The stage drive mechanism 15 is equipped with a linear encoder (not shown), measures the position of the stage 12 and feeds it back to the controller 30 . The controller 30 controls the operation of the exposure apparatus 10 , and outputs a control signal to the stage drive mechanism 15 and the DMD drive circuit 24 . In addition, display control processing for displaying a menu screen or the like on a monitor (not shown) is executed. A program related to the exposure operation is stored in the memory 32 in advance.

The photodetector 28 is provided near the end of the stage 12 , and includes a photosensor PD and a pulse signal generator 29 . Above the light detection unit 28, a light shielding unit 40 that partially passes light is provided. The light detection unit 28 is used for focus adjustment and alignment adjustment. The calculating unit 27 calculates a light quantity amplitude ratio as a parameter for monitoring the in-focus state based on the signal sent from the light detecting unit 28 . Moreover, the calculating part 27 can calculate the exposure position, ie, the position of the board|substrate W (stage 12) with respect to the exposure head.

The focusing prism 25 provided on the optical path between the imaging optical system 23 and the light-shielding unit 40 is an optical system in which two tongue-shaped prisms are oppositely arranged so as to be in contact with each other at an oblique angle, and a prism driving unit At (33), the two prisms are moved relative to each other so that the thickness in the optical axis direction is changed. The focal position of the imaging optical system 23 is moved along the substrate vertical direction (z-axis direction) by driving the prism 25 .

During the exposure operation, the stage 12 moves at a constant speed along the scanning direction X. The projection area (henceforth an exposure area) by the DMD22 whole moves relatively on the board|substrate W with the movement of the board|substrate W. The exposure operation is performed according to a predetermined exposure pitch, and the micromirror is controlled to project pattern light according to the exposure pitch.

By adjusting the control timing of each micromirror of the DMD 22 according to the relative position of the exposure area, the light of the pattern to be drawn on the position of the exposure area is sequentially projected. And a pattern is formed in the whole board|substrate W by drawing the whole board|substrate W with the some exposure head including the exposure head 18. As shown in FIG.

In addition, as an exposure method, not only the continuous movement method which moves at a constant speed, but also the step & repeat which moves intermittently is possible. In addition, multiple exposures (overlap exposure) in which the images of the micromirror are partially overlapped and exposed are also possible.

When the type of the substrate is changed or the like, focus adjustment is performed using the focus adjustment prism 25 before exposure. Specifically, the focus adjustment amount is calculated according to the thickness change of the substrate W or the photoresist, the focus adjustment prism 25 is driven according to the focus adjustment amount, and the focus position of the imaging optical system 23 is set on the drawing surface of the substrate W match with

When focus adjustment is performed, it is detected/monitored whether or not the in-focus state is maintained before the start of the exposure operation for each substrate or when the exposure operation time elapses for a predetermined time. Specifically, the pattern light for focus detection is projected while moving the stage 12 at a constant speed. The controller 30 determines whether or not it is in the in-focus state based on the output signal from the photodetector 28 .

Further, in order to form the pattern at the correct position, correction processing regarding the exposure start position is performed before the exposure operation starts. Specifically, the light of the pattern for position detection is projected while moving the stage 12 at a constant speed. The pattern light for position detection here is a pattern string different from the pattern light for focus detection. The controller 30 corrects the exposure start position based on the positional information transmitted from the calculating unit 27 .

Hereinafter, detection and monitoring of an in-focus state are demonstrated using FIGS. 2-6.

Fig. 2 is a diagram showing a light shielding unit and a pattern column for focus adjustment and focus detection. Fig. 3 is a schematic side view showing the arrangement of the photosensor and the light-shielding unit.

The light shielding portion 40 is disposed upward on the light source side of the photosensor PD, and the slit area ST is formed along the main scanning direction X. Here, six bar-shaped slits ST1 to ST6 perpendicular to the main scanning direction X, ie, parallel to the sub scanning direction Y, are formed at equal intervals with a slit pitch SP. The size of the light-shielding part 40 is larger than the size of the whole photosensor PD, and the photosensor PD arrange|positioned just below the light-shielding part 40 receives only the light which passed through the slit ST.

As shown in FIG. 3 , the photosensor PD that detects light intensity/light quantity is held by the support mechanism 60 , and the support mechanism 60 is attached to the stage 12 . The light-shielding part attaching member 50 supports the both ends of the light-shielding part 40 parallel to the light-receiving surface PS of the photosensor, and the drawing surface of the board|substrate W, and is held by the support mechanism 60 .

When the focus adjustment and the in-focus state are detected, the exposure area passes through the light-shielding portion 40 in accordance with the movement of the stage 12 . At this time, the light of the pattern column PT shown in FIG. 2 is projected toward the light blocking unit 40 . The pattern row PT is a so-called line & space (L/S) pattern, and is a pattern row in which a plurality of bar-shaped patterns are arranged in a line perpendicular to the main scanning direction X, ie, parallel to the sub scanning direction Y. Here, it is comprised by the four bar-shaped patterns PL1, PL2, PL3, PL4 arranged at equal intervals with the pattern pitch PP. Here, the line width K of the pattern column PT is equal to the width of the interline space. That is, the pattern pitch PP becomes twice the line width K.

Each pattern width K of the bar-shaped patterns PL1, PL2, PL3, and PL4 is wider than the slit width Z of each of the slits ST1 to ST6 formed in the light-shielding portion 40 . Moreover, the pattern pitch PP is also wider than the slit width Z. Therefore, after one bar-shaped pattern completely passes through one slit at a predetermined speed, the next bar-shaped pattern starts passing through the slit. In addition, each pattern width K of the bar-shaped patterns PL1, PL2, PL3, PL4 is set to the width|variety close to the upper limit of the resolution performance of the imaging optical system 23. FIG. For example, the pattern width K of the pattern column PT is determined by the width of the images (2 cells) of two adjacent micromirrors.

As shown in Fig. 2, the overall width PW along the main scanning direction X of the pattern column PT is smaller than the slit pitch SP. For this reason, when the tail-end bar-shaped pattern PL4 of the pattern row PT finishes passing through one slit at a constant speed, the leading bar-shaped pattern PL1 starts passing through the next slit.

When the light of the pattern column PT passes through the light shielding portion 40 at a constant speed and when the bar-shaped pattern PL1 passes through the slit ST6, the signal (hereinafter referred to as the light amount signal) output from the photosensor PD is time-sequentially change continuously. This is due to the fact that, as described above, the slit width Z is shorter than the pattern width K of the bar-shaped pattern PL1. Therefore, even when the different bar-shaped patterns PL2, PL3, and PL4 sequentially pass through the slit SL6, they continuously change in time series.

4 and 5 are graphs showing spatial light quantity distribution and time-series light quantity distribution when light of one bar-shaped pattern passes through one slit divided into in-focus state and defocused state. However, "spatial light quantity distribution" here shows the state of the light quantity change along the X direction, and the light quantity along the Y direction is not included.

The light intensity distribution/light amount distribution along the main scanning direction X of the bar image pattern PL1 close to the resolution limit of the imaging optical system 23 is approximately Gaussian, and the light amount decreases back and forth with the peak value as the center. As a result, the time series distribution (hereinafter referred to as light amount signal distribution) AL of the amount of light detected by the photosensor PD also becomes an approximately Gaussian distribution, and the time series light amount signal distribution AL and the spatial light amount distribution GD are similar to each other ( It has a positive correlation (refer to FIG. 4). Here, the light amount signal distribution AL represents a locus in which the light amount signal value detected according to the slit width Z is continuously plotted with respect to the movement of the stage 12 .

In order for the light intensity signal distribution AL and the light intensity distribution GD to have a similar relationship, the slit width Z needs to be shorter than the bar-shaped pattern width K, and by making it sufficiently short, the ridge shape of the light intensity signal distribution AL corresponds to the ridge shape of the light intensity distribution GD. getting closer Here, the slit width Z is determined to be 0.1 to 0.5 times the bar-shaped pattern width K. To achieve such a ratio, either the area setting of the micromirror that projects the light of the bar-shaped pattern PL1 or the adjustment of the slit width Z is adjusted, or both.

On the other hand, in FIG. 5, the spatial light quantity distribution in the state out of focus is shown. Even in this case, the light quantity distribution gradually increases and gradually decreases through the light quantity peak P', but the light quantity peak P' is smaller than the light quantity peak P in the in-focus state. This is because, since the focal position does not coincide with the surface of the light-shielding portion 40 , that is, the surface of the substrate W, the range of the light quantity distribution expands and the light intensity near the center decreases.

6 is a diagram illustrating spatial light quantity distribution according to a bar-shaped pattern column PT.

In FIG. 6, the light quantity distribution which connected the spatial light quantity distribution after passing through the slit of the four bar-shaped patterns PT1 - PT4 is shown. However, this distribution is a light amount distribution obtained when slits are formed according to the positions of each bar-shaped pattern, and in reality, spatial light-quantity distribution can be sequentially obtained according to the passage of each bar-shaped pattern.

A series of light quantity distributions shown in this way is represented by a periodic waveform (wavy shape), and has an amplitude S from the center. The amplitude S obtained at the focus position is larger than the amplitude S' when the focus is out of focus. However, as described above, since the line/space width of the pattern column PT is equal (=K), the center of the waveform coincides with both the focus position and the out-of-focus position. Accordingly, the magnitude of the amplitude of the spatial light quantity distribution becomes a barometer indicating whether or not the amplitude is at the focus position, that is, the in-focus position.

7 is a diagram illustrating a graph of spatial light quantity distribution having different amplitude ratios.

As shown in Fig. 7, a difference occurs in the amplitude of the waveforms in the case of being in the in-focus state and the case of being out of the in-focus state. Also, depending on the range of the depth of focus, different amplitudes are obtained even in the in-focus state. On the other hand, as described above, the waveform center position C does not substantially change even if the amplitudes are different. This is because a decrease in the amount of light in the vicinity of the light intensity peak (mountain portion of the waveform) occurs, and a complementary light amount increase portion occurs in the vicinity of the bottom of the light intensity (curve portion of the waveform).

Therefore, by setting the amplitude in the in-focus state as a reference, and comparing the reference amplitude with the amplitude of the detected spatial light quantity distribution, whether the in-focus state is present without performing a focus adjustment operation accompanied by a change in the focus position. can be monitored. For example, the in-focus state can be monitored by determining the ratio of the reference amplitude and the detected amplitude to determine the in-focus state, that is, the amplitude ratio that falls within the range of the focal depth.

However, as shown in Fig. 4, since spatial light quantity distribution and time series light quantity distribution have a similar relationship, by projecting the light of the pattern column PT for position detection onto the light shielding unit 40 while moving the stage 12 , a time-series light quantity distribution as shown in FIG. 7 can be obtained. Moreover, since the magnitude|size of the amplitude of the temporal-sequential light quantity distribution detected by the photosensor PD corresponds to the magnitude|size of the amplitude of spatial light quantity distribution, the amplitude ratio of time-series light quantity distribution corresponds to the amplitude ratio of spatial light quantity distribution. Accordingly, it becomes possible to judge the in-focus state based on the amplitude ratio in the time-series light quantity distribution.

When the light quantity of the pattern column PT for position detection is constant, the central position C of the spatial light quantity distribution is constant regardless of the in-focus state or the out-of-focus state, so it is better to calculate the amplitude A by detecting the central position and the minimum or maximum light quantity. It is possible. The central position C can be calculated from, for example, the peak light amount (maximum light amount) and the bottom light amount (minimum light amount) of the spatial light amount distribution.

Alternatively, since the central position C is equal to the average amount of light in one period (a pair of one line and one space) of the pattern column PT, a light meter such as a photosensor is provided for the central position C to measure and measure the amount of light You may obtain the average value of the light quantity of the pattern row|line|column PT. Here, the central position C is obtained by integrating or averaging the time-series light quantity obtained by the light passing through each slit according to the period.

On the other hand, with respect to the amplitude (reference amplitude) B when the focal position of the imaging optical system 23 coincides with the surface of the substrate W, by detecting the light amount signal level (base light amount) detected when not projecting a pattern, the central position An amplitude B between C and the detected light amount signal level can be obtained as the reference amplitude.

In addition, when the light metering unit is provided for calculating the average light amount, an independent light metering unit different from the light blocking unit or the photosensor may be provided, or the light blocking unit and/or the photosensor may also serve as a light metering unit. . In that case, what is necessary is just to provide an opening part separately in the position different from the above-mentioned slit in the light shielding part, and just to measure the amount of light which has passed through the opening part. As the opening, an opening having a light-transmitting portion at least wider than the line width K of the pattern column PT, preferably wider than the width PW of the entire pattern column PT is provided. Moreover, you may arrange|position separately the photosensor for measuring the amount of light, or you may measure light with the photo sensor mentioned above.

8 is a diagram illustrating a graph showing a correlation between a focus shift amount and an amplitude ratio.

In FIG. 8, the graph which plotted the amplitude ratio calculated based on the light quantity distribution detected while changing a focal position is shown. The larger the amplitude ratio A/B, that is, the closer the detected amplitude A is to the maximum amplitude B, the closer to the in-focus position, and as the focus position moves away from the in-focus position, the smaller the amplitude ratio A/B.

Therefore, at the time of shipment or the like, the amplitude ratio in the entire range in which the focus can be moved is calculated in advance, and data (master data) in which the amplitude ratio and the focal position of the imaging optical system 23 at that time are correlated (master data) is stored in the memory 32 . . Specifically, the light of the pattern for focus adjustment is projected while moving the stage 12 at a constant speed. Then, while driving the focus adjustment prism 25 to change the focus position within the movable distance range, this is repeatedly performed.

The controller 30 calculates the amplitude ratio based on the signal output from the photodetector 28 and creates master data. In addition, the in-focus position FP of the substrate W is stored in the memory 32 . Then, the in-focus range AR centering on the in-focus position FP is determined.

The in-focus position FP is determined as a position offset from the in-focus range AR0 with the largest amplitude ratio. In this case, there is a difference between the position of the light blocking portion 40 and the position of the drawing surface of the substrate W by the thickness T of the substrate W (refer to FIG. 1 ), and the light incident surface of the light blocking portion 40 is the mounting surface of the substrate W This is due to the fact that it is installed at a slightly lower position than (the stage surface). The width (upper limit, lower limit) of the in-focus range AR is determined based on the depth of focus of the imaging optical system 23, the thickness T of the substrate W, the type of photosensitive material formed on the surface of the substrate W, a required pattern order, and the like.

9 is a diagram showing a flow of in-focus state monitoring processing. Here, after the focus adjustment prism 25 is adjusted to the focus position calculated according to the board|substrate W etc. used, a process is performed before the exposure operation start of each board|substrate, or when a predetermined time passes.

The controller 30 controls the DMD driving circuit 24 so as to irradiate the bar-shaped pattern column PT toward the light shielding unit 40 while moving the stage 12 ( S101 ). Then, when the amplitude ratio M is calculated based on the light amount signal output from the photosensor PD (S102), it is determined whether the focus position according to the amplitude ratio M among the master data stored in the memory 32 is included in the focusing range R becomes (S103). In addition, you may carry out with the controller 30 about the calculation of an amplitude ratio.

When the focus position according to the detected amplitude ratio M deviates from the in-focus range R, the controller 30 executes display control processing for displaying a warning on the monitor (S104). Accordingly, the user can recognize that the focus position is out of the focus range R. In addition, it is also possible to notify the operator by other holding means, such as generation of a buzzer sound other than the warning display.

As described above, according to the first embodiment, while moving the stage 12, the pattern column PT composed of the bar-shaped patterns PL1 to PL4 is projected onto the light shielding portion 40 in which the slits ST1 to ST6 are formed from the photosensor PD. A light amount signal is output. Then, based on the amplitude ratio M obtained from the light amount signal, it is determined whether the in-focus state is maintained.

Without using a CCD whose resolution is limited by pixel size or the like, by scanning the pattern light for focus detection onto the substrate W, the in-focus or out-of-focus of the imaging optical system 23 is determined, so the in-focus state can be detected with high precision. In addition, in the in-focus range R determined for the master data stored in the memory, the rate of change of the amplitude ratio monotonically decreases, so that when out-of-focus occurs, the direction in which the focus position deviates from the in-focus range R can be reliably detected. . On the other hand, since the light detection unit 28 is used in combination with exposure position detection, it is not necessary to provide a dedicated CCD for focus detection, and the cost can be reduced.

In addition, even when pattern light passes through a plurality of slits and the average center value is calculated based on the relative movement amount, even when fluctuations in the light source or irregularity in the sensitivity of the photosensor occur, the influence can be suppressed. In addition, when the plurality of bar-shaped patterns pass through the plurality of slits, the parameter of the average value is enlarged, and the amplitude ratio is accurately measured.

The bar-shaped pattern of the pattern column for focus detection may not be perpendicular to the main scanning direction, and the main scanning direction width of the slit, the main scanning direction of the pattern light, so that the pattern shape is determined according to the slit formation direction to obtain the above-described continuous light quantity distribution It is free to set the direction width. About a photo sensor, it is also possible to provide a photo sensor with respect to each scanning band.

Next, 2nd Embodiment is demonstrated using FIGS. 10-13. In the second embodiment, the resolution performance of the imaging optical system is monitored. About the structure other than that, it is substantially the same as 1st Embodiment.

Fig. 10 is a diagram showing a light amount distribution when the resolution performance is maintained and a light amount distribution when the resolution performance is lowered.

When the resolution performance of the imaging optical system 23 is high (no problem), as described in the first embodiment, the spatial light amount distribution GD obtained by passing light of a bar-shaped pattern close to the resolution performance limit through one slit is, It becomes a Gaussian distribution centered on the peak, and the change in the amount of light (slope) at the edge of the bar-shaped pattern is relatively large. However, when the resolution performance decreases, in the spatial light quantity distribution GD1, the light quantity change at the edge portion of the bar-shaped pattern becomes gentle, and the peak light quantity decreases, resulting in a flat wavy light quantity distribution.

As a result, in the continuous spatial light quantity distribution by the pattern column PT, the distance from the center position of both the peak (peak light quantity) and the valley (bottom light quantity) of the waveform becomes small. That is, the amplitude of spatial light quantity distribution becomes small. Accordingly, the resolution performance can be monitored by determining the amplitude according to the required minimum resolution performance as the reference amplitude, and calculating the amplitude ratio by detecting the amplitude of the spatial light quantity distribution as in the first embodiment.

11 is a diagram showing a graph showing the relationship between the resolution and the amplitude ratio. 12 is a diagram illustrating a spatial light quantity distribution having an amplitude serving as a reference.

In Fig. 11, a curve CG showing the correspondence between the resolution and the amplitude ratio is drawn. However, the resolution indicating the horizontal axis of the graph of FIG. 11 indicates the number of straight lines that can be imaged per unit length (1 mm) for the imaging optical system 23 . Since the amplitude decreases when the resolution performance decreases, the resolution decreases as the value of the amplitude ratio decreases. Accordingly, if the amplitude ratio to be measured is greater than the amplitude ratio D0 which becomes the limit (lower limit), the required resolution performance is maintained.

The spatial light quantity distribution GD' shown in Fig. 12 represents the light quantity distribution obtained when the spatial light quantity distributions GD1 and GD2 for one bar-shaped pattern are adjacent to each other according to the limit of the required resolution performance. Waveforms of spatial light quantity distributions GD1 and GD2 according to resolution performance limits are determined according to the specifications of the exposure apparatus and optical performance of the imaging optical system 23 and the like.

If the ratio (A0/B) between the amplitude A0 of the spatial light distribution GD' and the maximum amplitude B in the case of the highest resolution performance is defined as the limit amplitude ratio D0, if the ratio A/B between the detected amplitude A and the reference amplitude B is greater than D0 , it can be judged that the required resolution performance is satisfied. Data relating to the limit amplitude ratio D0 and the curve CG are stored in advance in the memory 32 .

Fig. 13 is a diagram showing a flow of monitoring processing for resolution performance. As in the first embodiment, processing is performed at an arbitrary timing (when lot production is started, when a predetermined time has elapsed, etc.).

The controller 30 controls the DMD driving circuit 24 so as to irradiate the bar-shaped pattern column PT toward the light blocking unit 40 while moving the stage 12 ( S201 ). Then, when the amplitude ratio M is calculated based on the light amount signal output from the photosensor PD (S202), it is determined whether the amplitude ratio M is equal to or greater than the limit amplitude ratio D0 (S203). When the amplitude ratio M is less than the limit amplitude ratio D0, an operator is notified of a decrease in resolution performance by a warning buzzer or the like (S204).

In this way, according to the second embodiment, the photo sensor PD is projected by projecting the pattern column PT composed of the bar-shaped patterns PL1 to PL4 onto the light shielding portion 40 in which the slits ST1 to ST6 are formed while the stage 12 is moved. A light intensity signal is output from And based on the amplitude ratio M calculated|required from the light quantity signal, it is judged whether the resolution is falling below the resolution used as a limit.

In the first and second embodiments, it is assumed that the central position (average light quantity) of the light quantity amplitude is constant as the line/space widths of the pattern columns are the same, and the reference amplitude in the in-focus state is the average light quantity and the light quantity in the pattern non-projection state. , but the reference amplitude may be calculated by other methods, and it is possible to obtain the amplitude ratio even when the line/space widths of the pattern columns are not the same. For example, in focus adjustment performed while moving the optical system or substrate, the amplitude of the waveform-like light amount is calculated in the in-focus state or in the state with resolution, and the reference amplitude is determined at the time of focus detection based on fluctuations in the light source output, etc. is also free

In addition, the L/S pattern light may be projected to an image sensor such as a CCD without projecting a bar-shaped pattern row while moving the stage, and the in-focus state or the resolution performance state may be determined from the spatial light quantity distribution.

Next, 3rd Embodiment is demonstrated using FIGS. 14-20. In the third embodiment, the light quantity distribution over the entire exposure area is detected, and whether there is a decrease in the light quantity is monitored.

The exposure apparatus of the third embodiment adopts the same configuration as that of the first embodiment shown in FIG. 1 . However, the prism and the prism driving unit are not provided.

In order to check whether there is no deterioration of the optical system, light quantity measurement is performed between lots or when the exposure operation time elapses for a predetermined time. Specifically, the pattern light for light quantity distribution detection is projected while moving the stage 12 at a constant speed. The controller 30 determines whether or not a decrease in the amount of light occurs based on the output signal from the light detection unit 28 .

Further, in order to form the pattern at the correct position, correction processing regarding the exposure start position is performed before the exposure operation starts. Specifically, the pattern light for position detection is projected while moving the stage 12 at a constant speed. The controller 30 corrects the exposure start position based on the positional information transmitted from the calculating unit 27 .

Hereinafter, detection and monitoring of an in-focus state are demonstrated using FIGS. 14-15.

Fig. 14 is a diagram showing a pattern column and a light shielding unit for measuring the light quantity distribution.

The pattern PT for measuring the amount of light distribution is a pattern row (hereinafter also referred to as a line & space (L/S) pattern) in which a plurality of bar-like patterns PL1, PL2, ... each having a pattern length Ly are arranged at equal intervals along the main scanning direction. ), and each bar-shaped pattern parallel to the sub-scan direction is arranged at equal intervals with a pitch PP. The width of each bar-shaped pattern here corresponds to the width of the micro-projection area of the micromirror for one line along the sub-scan direction.

The slits SL formed in the light shielding portion 40 have a length SLL along the sub-scan direction greater than the length Ly along the sub-scan direction of the pattern PT. Further, the slits SL are inclined by a minute angle θ with respect to the line direction (longitudinal direction) of the pattern PT. Here, the pattern PT is formed to be inclined by a minute angle θ° (not shown in FIG. 3 ) with respect to the Y direction (sub-scan direction) of the X-Y coordinate system defined on the stage 12 as described above. Accordingly, the slits SL are inclined by θ±θ° with respect to the sub-scan direction Y.

The photosensor PD disposed below the slit SL is constituted by one photodiode having one light receiving surface here, and only the light that has passed through the slit SL having a narrow and elongated area (photometric area) PDS on the bar is received. That is, the light transmitted through the slit SL is incident on a part of the entire area PDS of the light receiving surface of the photosensor PD. Moreover, the length SB along the sub-scan direction is longer than the pattern length Ly, and the photosensor PD has the photosensor width PDW larger than the width of the slit SL so that all the light which has passed through the slit SL may reach the photosensor PD. On the other hand, as will be described later, the slit width SLB is smaller than the width of each bar-shaped pattern.

The pitch PP of the pattern PT is determined to be larger than the occupied length B along the main scanning direction of the slits SL. Here, the occupied length B is the length occupied along the main scanning direction (when projected) between the arbitrary point T1 of the slit SL (here, the slit position aligned with the pattern PT) and the point T2 separated by Ly in the sub-scan direction. length), and since the inclination angle θ is minute, it can be expressed as the occupied length B ≒ Lytanθ in the main scanning direction.

In this way, by setting the pattern pitch PP to be larger than the occupied length B in the main scanning direction of the slit SL, when the pattern PT passes through the slit SL, when one bar-shaped pattern starts passing through the slit SL and then ends Until then, the following bar-like pattern does not initiate the passage of the slit SL. That is, the photo sensor PD, which is a line sensor, sequentially receives the bar-shaped light one by one in time series.

15A to 15D are diagrams illustrating a process in which one bar-shaped pattern PL1 passes through a slit SL. 16 is a light quantity distribution along the sub-scan direction obtained when one bar-shaped pattern PL1 passes through the slit SL. In addition, for explanation, the inclination angle of the slit SL with respect to the pattern PT is exaggerated.

Since the slit SL is inclined with respect to the bar-shaped pattern PL1, one longitudinal side LT1 of the bar-shaped pattern PL1 starts to intersect the slit SL at its end EL (see Fig. 15A). As the bar-shaped pattern PL1 moves relative to each other, the intersection range R between the pattern PL1 and the slit SL is widened (refer to FIG. 15B ), and the slit SL intersects both sides LT1 and LT2 of the bar-shaped pattern PL.

After the state in which the slit SL intersects both sides LT1 and LT2 of the bar-like pattern PL1 continues (see Fig. 15c), only the side LT2 moves to the step of intersecting the bar-like pattern PL, and finally, the entire bar-like pattern PL1 goes beyond the slit SL (see Fig. 15d).

In Fig. 16, the light quantity distribution along the sub-scan direction detected when the bar-shaped pattern PL1 passes through the slit SL is shown. The photo sensor PD, which is a line sensor, detects the amount of light in time-series, but as described above, from the start to the end of the intersection of one bar-shaped pattern PL1 with the slit SL, the adjacent bar-shaped pattern PL2 and the slit SL do not cross

Therefore, the light quantity distribution in one bar-shaped pattern detected time-sequentially by the photosensor PD corresponds to the light quantity distribution along the sub-scan direction. Figs. 16A to 16D show the amount of light when the bar-shaped pattern PL1 is located at the positions shown in Figs. 15A to 15D, respectively.

Fig. 17 is a diagram showing the movement pitch of the slits according to the light amount detection time interval of the photosensor.

When the amount of light is detected by the photosensor PD every time the slit SL moves by the movement pitch d along the main scanning direction, the measurement length L (=Lx/tanθ) is equal to the pitch P (=d/tanθ) along the sub-scan direction Move. However, the measurement length L represents the slit length along the sub-scan direction in which the amount of light is detected by the photosensor PD.

Here, since the width Lx of the pattern PL1 is sufficiently larger than the movement pitch d along the main scanning direction, the measurement length L becomes sufficiently longer than the pitch P along the sub-scan direction (L»P). Since the pitch P represents the resolution along the sub-scan direction, the pitch P becomes smaller than the micro-projection area size (cell size) of one micromirror.

As a result, if the light quantity distribution detected for each movement pitch d is regarded as the light quantity distribution along the sub-scan direction, the light quantity change is expressed as a change equal to or less than the cell size, and the light quantity distribution curve becomes smooth. That is, it is possible to obtain a light quantity distribution curve having no level difference as shown in FIG. 16 . When the bar-shaped pattern sequentially passes through the slit SL, the light amount distribution along the sub-scan direction is detected. As a result, the light amount distribution for the entire exposure area EA can be obtained.

Fig. 18 is a diagram showing the light amount distribution for each bar-shaped pattern overlaid. 19 is a diagram showing the light quantity distribution over the entire exposure area three-dimensionally.

19, the light quantity distribution LG with respect to the whole exposure area is shown. Here, although a decrease in the amount of light does not occur in the vicinity of the periphery, the amount of light is falling in the center. As shown in Fig. 18, when the maximum light amount MM is detected in the light amount distribution DPL1 around the exposure area and the minimum light amount ML is detected in the light amount distribution DPLm near the center, the optical system is based on the light amount ratio (ML/MM) Deterioration of the back can be detected. However, for light amount detection, the light amount ratio is calculated with the range BE effective for detection as a target.

Fig. 20 is a flowchart showing light amount distribution measurement and warning processing. Here, it is executed for every predetermined operating time.

While the exposure area is moved relative to the slit SL, the bar-shaped pattern PT is projected, and the amount of light is detected by the photosensor PD (S301). And based on the output signal from photosensor PD, light quantity ratio is computed. In addition, three-dimensional light quantity distribution data is created along with the calculation of the light quantity ratio and stored in a memory (not shown) or the like (S302).

When the light quantity ratio is equal to or less than a predetermined threshold, a warning is displayed on an operation screen or the like to keep the decrease in light quantity (S303, S304). At this time, the information notifying the fact may be recorded in the file for production management. Moreover, you may compare the three-dimensional light quantity distribution data obtained by calculation process with the light quantity distribution data of the initial stage without component deterioration, and you may judge whether the light quantity fall has arisen.

Thus, according to 3rd Embodiment, in the stage 12 of the exposure apparatus 10, the light detection part 28 in which the slit SL was formed in the upward direction of the photosensor PD is provided. Then, the bar-shaped pattern PT is projected in a state in which the slit SL is inclined with respect to the sub-scan direction, and the slit SL is passed through. At this time, the pitch PP of the bar-shaped pattern PT is determined to be smaller than the occupied length B along the main scanning direction of the slit SL.

While the pattern PT passes through the slit SL, on each bar pattern PT1, PT2… are projected on the photosensor PD while being changed one by one in order. While one bar-like pattern is passing through the slit SL, the next pattern does not start passing through the slit SL. And when the projection area|region in the photosensor PD moves according to the minute angle (theta), it becomes possible to detect the light quantity distribution along the sub-scan direction, and it becomes possible to acquire the light quantity distribution of the whole exposure area.

In order to form the light amount distribution of the exposure area, all of the light of each bar-shaped pattern needs to be received when passing through the slits of the exposure area. can be realized For example, when the vertical and horizontal size of the optical modulation element array (micromirror array) is 4:3 according to the image standard, the inclination angle θ may be set to 37° or less. Further, when the vertical and horizontal size of the optical modulation element array is 16:9, the inclination angle θ may be set to 30° or less.

In addition, when an exposure area is made to incline a minute angle and is relatively moved, the angle is minute. Therefore, the same light quantity distribution can be obtained by setting the inclination angle of the slit to be 37 degrees or less with respect to the sub-scan direction prescribed in the drawing table.

The inclination angle θ of the slit SL with respect to the pattern PT can be set to various angles, but in consideration of the precision, it is preferable to increase the number of pattern arrangements of the L/S pattern as much as possible. In that sense, it is preferable to project each bar-like pattern with one line of the micromirror. In this case, since the width of the pattern PT and the like are affected by the micromirror micro-projection area (cell size), etc., it is preferable to set the inclination angle to be less than or equal to a predetermined angle in order to satisfy B < PP.

On the other hand, within a range satisfying B < PP, the resolution can be further increased by making θ as large as possible. Also, as the length of the light quantity rising/falling region increases as the measurement length L increases, the detection effective range BE becomes narrower by that amount. In order to widen the effective range BE as much as possible, it is desirable to make θ as large as possible.

As an example, in the case of using a DMD composed of a 1024×768 micromirror according to the XGA standard (1024 pixels in the line direction), the line pitch PP may be determined by the number of lines of the L/S pattern. If the number of lines is set to 16 or more in consideration of the precision of the light distribution data, the pitch PP when there are 16 lines becomes 768/15 = 51 pixels, so it is necessary to satisfy B(=1024 tanθ) < PP(=51) Therefore, the inclination angle θ is set to be smaller than 2.8°. Since the resolution P in the Y direction is expressed by d/tanθ, when the moving pitch d = 1 µm, the resolution P = 20 µm when θ = 2.8°.

On the other hand, if it is desired that the detection effective range BE exceeds 90% of the pattern length Ly (that is, L is 5% or less of Ly), the width Lx of the line of pattern light is 1 pixel, so L = Lx/tanθ < Ly From ×0.05, tanθ > 1/51.2 is derived. That is, the inclination angle θ is determined to be an angle greater than 1.2°. In this case, at θ = 1.2°, the resolution P = 48 μm.

From the above, it is possible to determine the angle θ between the slit SL and the pattern PT in the range of 1.2° < θ < 2.8°, and more preferably, in the range of 2.0° < θ < 2.8°, θ may be determined. In the case where the exposure area has an inclination angle θ°, if it is inclined on the same side as the slit, it is subtracted by that amount, and if it is inclined on the side opposite to the slit, it may be added by that much.

In addition, about the photo sensor PD, you may comprise sensors other than the narrow and elongate photodiode extending in the longitudinal direction mentioned above, and a photo sensor with the light receiving surface size which can receive light in a bar-shaped pattern may be sufficient. It is also possible to detect light quantity distribution by structures other than the light shielding part which provided the slit on the photo sensor PD. Moreover, it is possible to apply L/S patterns other than the above-mentioned pattern also to a projection pattern. By determining the pitch of the L/S pattern light so that the light amount of the pattern on each line of the L/S pattern is sequentially measured, the light amount distribution of the entire exposure area can be measured. Moreover, when there are a plurality of exposure heads, what is necessary is just to form a slit with respect to each exposure head.

The configuration of the light metering unit is not limited to the above configuration, and for example, the light metering unit in which the light shielding unit and the photosensor are integrally configured may be detachably attached to the exposure apparatus or provided integrally with the exposure apparatus. A photo sensor having a light receiving area capable of receiving light passing through a narrow and elongated (extending in the longitudinal direction) light metering area inclined with respect to the line pattern is provided, and when the pattern light passes through the entire light receiving area, the area corresponding to the metering area It is good to configure so that light is incident.

In addition, it may be determined that deterioration of the optical system occurs when the difference is equal to or greater than a predetermined threshold by obtaining the light quantity difference, not the light quantity ratio. The light quantity change may be detected by parameters other than the light quantity ratio and the light quantity difference.

10: exposure apparatus
22: DMD (Light Modulation Element Array)
27: arithmetic unit (light amount detection unit)
28: light detection unit (metering unit)
30: controller (exposure control unit, light quantity detection unit, holding unit)
40: light blocking unit
PD: photo sensor
SL: slit (metering area)

Claims (13)

a light modulation element array in which a plurality of light modulation elements are arranged in a matrix;
a scanning unit for relatively moving the exposure area by the optical modulation element array with respect to the object to be drawn along the main scanning direction;
an exposure control unit configured to control the plurality of light modulation elements based on pattern data corresponding to the relative positions of the exposure areas;
an imaging optical system for imaging the patterned light from the light modulation element array on a drawing surface of the drawing object;
a light-shielding unit having at least one slit formed along the drawing surface;
a light metering unit for receiving the light passing through the slit;
an in-focus detection unit configured to detect an in-focus state based on the output of the light metering unit;
the exposure control unit projects line and space (L/S) pattern light while the light blocking unit moves relative to the exposure area;
The in-focus detection unit detects whether or not the image to be drawn is in the in-focus range based on the amplitude of the waveform-like light amount detected by projection of the L/S pattern light and the reference amplitude when it is in the in-focus range exposure device. According to claim 1,
The exposure apparatus according to claim 1, wherein the in-focus detection unit determines whether or not the in-focus range is within the in-focus range based on an amplitude ratio that is a ratio between a light quantity amplitude and a reference amplitude. 3. The method of claim 2,
The exposure apparatus according to claim 1, wherein the in-focus detection unit determines whether or not the in-focus range is present based on a correspondence relationship between the amplitude ratio and a focal position of the imaging optical system. 4. The method according to any one of claims 1 to 3,
The exposure apparatus according to claim 1, wherein the in-focus detection unit calculates a reference amplitude based on an average light amount of the L/S pattern light and a base light amount when the L/S pattern light is not projected. 5. The method of claim 4,
The light-shielding unit has an opening for measuring the average light quantity,
The exposure apparatus according to claim 1, wherein the light metering unit has a light receiving unit for an average light quantity that receives the L/S pattern light passing through the opening for measuring the average light quantity. a light modulation element array in which a plurality of light modulation elements are arranged in a matrix;
a scanning unit for relatively moving the exposure area by the optical modulation element array with respect to the object to be drawn along the main scanning direction;
an exposure control unit configured to control the plurality of light modulation elements based on pattern data corresponding to the relative positions of the exposure areas;
an imaging optical system for imaging the patterned light from the light modulation element array on a drawing surface of the drawing object;
a light-shielding unit having at least one slit formed along the drawing surface;
a light metering unit for receiving the light passing through the slit;
a resolution detection unit configured to detect the resolution of the imaging optical system based on the output from the light metering unit;
the exposure control unit projects line & space (L/S) pattern light while the light blocking unit moves relative to the exposure area;
Detecting whether the resolution is lower than the limit resolution based on the amplitude of the waveform light amount detected by the projection of the L/S pattern light and the reference amplitude when the resolution detection unit has a resolution greater than or equal to a predetermined limit resolution Exposure apparatus characterized in that. 7. The method of claim 6,
The exposure apparatus according to claim 1, wherein the resolving power detection unit determines whether the resolving power is lower than a limit resolving power based on an amplitude ratio that is a ratio between the detected amplitude and the reference amplitude. 8. The method of claim 7,
The exposure apparatus according to claim 1, wherein the resolving power detecting unit determines whether or not the resolving power is lower than the limit resolving power based on a correspondence relationship between the amplitude ratio and the resolving power of the imaging optical system. a light modulation element array in which a plurality of light modulation elements are arranged in a matrix;
a scanning unit for relatively moving the exposure area by the optical modulation element array with respect to the object to be drawn along the main scanning direction;
an exposure control unit that controls the plurality of light modulation elements to project light in a line and space (L/S) pattern arranged along the main scanning direction onto the object to be drawn;
A light metering unit for receiving light passing through a narrow and long light metering area inclined with respect to the line direction of the L/S pattern;
a light quantity detection unit configured to detect a light quantity distribution of an exposure area based on an output from the light metering unit when the L/S pattern moves relative to the light metering area;
An exposure apparatus characterized in that the pitch of the L/S pattern is determined so that the light amount of the pattern on each line of the L/S pattern is sequentially measured. 10. The method of claim 9,
The exposure apparatus according to claim 1, wherein the inclination angle of the photometric area with respect to the line direction satisfies the following expression.
Lytanθ < PP
However, Ly represents the length along the sub-scan direction of the L/S pattern, θ represents the inclination angle, and PP represents the pitch of the L/S pattern. 11. The method according to any one of claims 9 to 10,
The exposure apparatus according to claim 1, wherein the inclination angle of the photometric area with respect to the line direction satisfies the following expression.
θ ≤ 37°
However, θ represents the inclination angle of the photometric area. 12. The method of claim 11,
The exposure apparatus according to claim 1, wherein the inclination angle of the photometric area with respect to the line direction satisfies the following expression.
1.2 °< θ < 2.8°
However, θ represents the inclination angle of the photometric area. 10. The method of claim 9,
The said light amount detection part creates the light amount distribution graph of an exposure area, The exposure apparatus characterized by the above-mentioned.

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