JP2016111200A - Exposure equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and highly accurately monitor an optical system resolution performance in an exposure equipment.SOLUTION: By projecting a pattern array PT constructed by bar shape patterns PL1 to PL4 while moving a stage 12 to a shading part 40 formed to slits ST1 to ST6, a light quantity signal from a photo sensor PD. It is determined whether or not a resolution power is reduced from a limit resolution power.SELECTED DRAWING: Figure 12

Description

  The present invention relates to an exposure apparatus that forms a pattern using a light modulation element array or the like, and more particularly to detection of resolution / resolution of an optical system.

  In a maskless exposure apparatus, pattern light is projected onto a substrate by a light modulation element array such as DMD (Digital Micro-mirror Device) while moving a stage on which the substrate is mounted along the scanning direction. In this case, two-dimensionally arranged light modulation elements (such as micromirrors) are controlled so as to project pattern light according to the position of the projection area (exposure area) on the substrate placed on the stage.

  In order to adjust the focus position of the pattern light on the upper surface of the substrate on which the photosensitive material is applied or pasted, focus adjustment is performed before exposure. For example, at the time of focus adjustment, light of a line & space pattern (L / S pattern) having a period close to the resolution limit of the projection optical system is projected by the DMD while moving the focus lens in the optical axis direction. A CCD camera is provided below the projection optical system. When the CCD camera receives pattern light, the contrast-related value of the L / S pattern is calculated by image processing. Then, the peak detection position is set as the in-focus position, and the substrate position is adjusted (see Patent Document 1).

  The focal position of the optical system of the exposure apparatus may change over time. Therefore, even if the focus adjustment is performed once, the focus position may deviate from the focus position. In particular, in recent years, since the depth of focus tends to become shallower as the pattern becomes finer, it tends to be out of focus. Therefore, the beam projected on the dummy substrate is observed with an observation camera, the position of the focusing lens that maximizes the contrast is set, and the distance (reference distance) between the substrate and the optical system at that position is determined over time. A calibration operation for adjusting according to the change is performed (see Patent Document 2).

JP 2009-246165 A JP 2013-77777 A

  Depending on the installation status of the exposure apparatus, dust, water vapor, or the like adheres to the lens surface with use for a long time. Further, since the pattern is formed by irradiating the substrate formed of resin or the like with high brightness light, the resin component or the like adheres to the lens surface as described above. If the imaging performance of the optical system is deteriorated due to dust or the like adhering to the lens surface, the pattern resolution deviates from the required resolution level.

  In the case of a transparent deposit such as water vapor, only the imaging performance is reduced without a decrease in the amount of light, and therefore a decrease in resolution cannot be detected even if the amount of light from the light source is monitored. For this reason, it is necessary to confirm in advance whether or not the resolution is reduced before exposure. However, forming a pattern on a test substrate and judging the resolution from the formed pattern requires a long working time, and hinders improvement in substrate manufacturing throughput.

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

  An exposure apparatus according to the present invention includes a light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and a scanning unit that relatively moves an exposure area by the light modulation element array with respect to an object to be drawn along a main scanning direction. Based on pattern data corresponding to the relative position of the exposure area, an exposure control unit that controls a plurality of light modulation elements, and an image that forms pattern light from the light modulation element array on the drawing surface of the drawing object The resolving power of the imaging optical system is detected based on the optical system, a light-shielding portion in which at least one slit is formed along the drawing surface, a photometry unit that receives light passing through the slit, and an output from the photometry unit. A resolving power detector.

  The exposure control unit of the present invention projects line & space (L / S) pattern light while the exposure area moves relative to the light shielding unit. As the L / S pattern light passes through the slit while relatively moving, the waveform light quantity is detected based on the output of the photometry unit. Here, the “waveform light quantity” represents a spatial light quantity distribution in which the light quantity change along the scanning direction is periodic and wave-shaped. The output of the metering unit is a waveform output with periodicity in time series (referred to as time-series waveform light quantity), but a spatial light distribution corresponding to the characteristics of time-series waveform light quantity and light quantity change is obtained. It is done.

  Then, the resolving power detection unit is based on the amplitude of the waveform light amount detected by the projection of the L / S pattern light (that is, the width of the light amount displacement) and the reference amplitude when the resolving power exceeds a predetermined limit resolving power, Detecting whether or not the detected resolving power is lower than the limit resolving power. Here, the “reference amplitude when in the in-focus range” means a wave detected in a state where it is determined to be in focus based on the depth of focus. Represents the amplitude of the shape light quantity. It is possible to detect a decrease in resolving power simply by detecting the amplitude of the waveform light quantity.

  For example, the resolving power detection unit can determine whether or not 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 resolving power can be monitored by an easy calculation process of calculating the amplitude ratio.

  In particular, when the center light quantity (average light quantity) of the waveform light quantity is the same in both the case where the resolution is low and the case where the resolution is low, the resolution detector detects the average light quantity of the L / S pattern light and the L / S pattern light. The reference amplitude can be calculated based on the base light amount when not being projected. For the amplitude of the waveform light quantity, the maximum light quantity and the minimum light quantity (Peak to Peak) may be detected.

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

  When calculating the average light quantity, a dedicated opening and a light receiving part may be provided. For example, the light shielding unit includes an average light amount measurement opening, and the photometry unit includes an average light amount light receiving unit that receives L / S pattern light passing through the average light amount measurement opening.

  In consideration of promptly notifying the operator that it is not in the focus range, it is preferable to provide a notification unit that notifies the operator that it is out of the focus range when it is out of the focus range.

  An exposure apparatus detects an exposure position based on the amount of light output from the photometry unit by projecting an L / S pattern light for detecting the exposure position while the exposure area moves relative to the light shielding unit. Can be provided. In this case, both exposure position detection and focus detection can be performed by the same mechanism.

  According to another aspect of the present invention, a resolving power detection device for an exposure apparatus includes a photometric unit that receives line and space (L / S) pattern light that passes through a slit, and a waveform light quantity detected by projection of the L / S pattern light. And a resolving power detector that detects whether or not the resolving power detected is lower than the limiting resolving power based on a predetermined resolving power greater than a predetermined resolving power. According to another aspect of the present invention, there is provided an exposure method of an exposure apparatus that receives line & space (L / S) pattern light that passes through a slit and detects an amplitude of a waveform light quantity detected by projection of the L / S pattern light. Whether or not the resolving power is lower than the limit resolving power is detected based on the reference amplitude when the resolving power is equal to or higher than the predetermined resolving power.

  According to the present invention, the resolution performance of the optical system can be monitored easily and accurately in the exposure apparatus.

It is a block diagram of the exposure apparatus which is 1st Embodiment. It is the figure which showed the light-shielding part and the pattern row | line | column for focus adjustment and focus detection. It is the schematic side view which showed arrangement | positioning of a photo sensor and a light-shielding part. It is the figure which showed the graph which showed the spatial light quantity distribution when the light of one bar-shaped pattern passed through one slit, and a time-sequential light quantity distribution. It is the figure which showed the graph which showed the spatial light quantity distribution when the light of one bar-shaped pattern passed through one slit. It is the figure which showed the spatial light quantity distribution according to the bar-shaped pattern row | line | column. It is the figure which showed the graph of spatial light quantity distribution which has a different amplitude ratio. It is the figure which showed the graph showing the correlation of a focal moving amount | distance and amplitude ratio. It is the figure which showed the flow of the focus state monitoring process. It is the figure which showed light quantity distribution when resolution performance is maintained, and light quantity distribution when resolution performance falls. It is the figure which showed the graph showing the relationship between resolution and an amplitude ratio. It is the figure which showed the spatial light quantity distribution with the amplitude used as a reference | standard. It is the figure which showed the flow of the monitoring process of resolution performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

  The exposure apparatus 10 is a maskless exposure apparatus that forms a pattern by irradiating light onto a substrate W to which a photosensitive material such as a photoresist is applied or pasted, and a stage 12 on which the substrate W is mounted extends in the scanning direction. It is installed to be movable. 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). The exposure head 18 includes a DMD 22, an illumination optical system (not shown), and an imaging optical system. 23. The light source 20 is constituted by a discharge lamp (not shown), for example, and is driven by a light source driving unit 21.

  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 minute micromirrors are two-dimensionally arranged, and each micromirror selectively switches the light reflection direction by changing the posture. By controlling the posture of each mirror by the DMD driving circuit 24, light corresponding to the pattern is projected (imaged) onto the surface of the substrate W via the imaging optical system 23. As a result, a pattern image is formed on the substrate W.

  The stage drive mechanism 15 moves the stage 12 in accordance with a control signal from the controller 30. The stage drive mechanism 15 includes a linear encoder (not shown), and 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. Further, display control processing for displaying a menu screen or the like on a monitor (not shown) is executed. A program relating to the exposure operation is stored in the memory 32 in advance.

  The light detection unit 28 is installed near the end of the stage 12 and includes a photosensor PD and a pulse signal generation unit 29. A light blocking unit 40 that partially transmits light is provided above the light detection unit 28. The light detection unit 28 is used during focus adjustment and alignment adjustment. Based on the signal sent from the light detection unit 28, the calculation unit 27 calculates a light intensity amplitude ratio that is a parameter for monitoring the in-focus state. Further, the calculation unit 27 can calculate the exposure position, that is, the position of the substrate W (stage 12) with respect to the exposure head.

  The focus adjustment 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 wedge-shaped prisms are arranged to face each other so as to be in contact with each other at an inclined surface. 33 moves the two prisms relative to each other so that the thickness in the optical axis direction changes. The focal position of the imaging optical system 23 moves along the substrate vertical direction (z-axis direction) by driving the prism 25.

  During the exposure operation, the stage 12 moves along the scanning direction X at a constant speed. A projection area (hereinafter referred to as an exposure area) by the entire DMD 22 relatively moves on the substrate W as the substrate W moves. The exposure operation is performed according to a predetermined exposure pitch, and the micromirror is controlled to project pattern light in accordance with 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 is sequentially projected at the position of the exposure area. Then, a pattern is formed on the entire substrate W by drawing the entire substrate W with a plurality of exposure heads including the exposure head 18.

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

  When the substrate type is changed, focus adjustment is performed using the focus adjustment prism 25 before exposure. Specifically, the focus adjustment amount is calculated according to changes in the thickness of the substrate W and 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 to the substrate W. Match the drawing surface of.

  When the 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 every time the exposure work time elapses. Specifically, pattern light for focus detection is projected while moving the stage 12 at a constant speed. Based on the output signal from the light detection unit 28, the controller 30 determines whether or not it is in focus.

  Further, in order to form a pattern at an accurate position, correction processing relating to the exposure start position is performed before the exposure operation is started. Specifically, the light of the pattern for position detection is projected while moving the stage 12 at a constant speed. The position detection pattern light here is a pattern row different from the focus detection pattern light. The controller 30 corrects the exposure start position based on the position information sent from the calculation unit 27.

  Hereinafter, detection and monitoring of the in-focus state will be described with reference to FIGS.

  FIG. 2 is a diagram illustrating a light shielding unit and a pattern row for focus adjustment and focus detection. FIG. 3 is a schematic side view showing the arrangement of the photosensor and the light shielding portion.

  The light shielding portion 40 is disposed above 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, that is, 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 entire size of the photosensor PD, and the photosensor PD arranged directly below the light-shielding part 40 receives only light that has passed through the slit ST.

  As shown in FIG. 3, the photosensor PD for detecting light intensity / light quantity is held by a support mechanism 60, and the support mechanism 60 is attached to the stage 12. The support mechanism 50 supports both ends of the light shielding unit 40 parallel to the light receiving surface PS of the photosensor and the drawing surface of the 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 unit 40 as the stage 12 moves. At this time, the light of the pattern row PT shown in FIG. 2 is projected toward the light shielding 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 perpendicular to the main scanning direction X, that is, parallel to the sub-scanning direction Y are arranged. Here, it is constituted by four bar-shaped patterns PL1, PL2, PL3, and PL4 arranged at equal intervals with a pattern pitch PP. Here, the line width K of the pattern row PT is equal to the width of the inter-line space. That is, the pattern pitch PP is twice the line width K.

  Each pattern width K of the bar-shaped patterns PL1, PL2, PL3, PL4 is wider than the slit width Z of each of the slits ST1 to ST6 formed in the light shielding part 40. The pattern pitch PP is also wider than the slit width Z. Therefore, after one bar-shaped pattern has completely passed through one slit at a predetermined speed, the next bar-shaped pattern starts to pass through the slit. Each pattern width K of the bar-shaped patterns PL1, PL2, PL3, and PL4 is set to a width close to the upper limit of the resolution performance of the imaging optical system 23. For example, the pattern width K of the pattern row PT is determined to be the width of two adjacent two micromirror images (2 cells).

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

  When light of the pattern row PT passes through the light shielding unit 40 at a constant speed, a signal (hereinafter referred to as a light amount signal) output from the photosensor PD when the bar-shaped pattern PL1 passes through the slit ST6 is time-sequentially. It changes continuously. As described above, this is because the slit width Z is shorter than the pattern width K of the bar-shaped pattern PL1. Therefore, even when the other 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 the spatial light amount distribution and time-series light amount distribution when light of one bar-shaped pattern passes through one slit, divided into an in-focus state and an out-of-focus state. is there. However, the “spatial light amount distribution” here represents a change in the light amount along the X direction, and does not include the light amount along the Y direction.

  The light intensity distribution / light quantity distribution along the main scanning direction X of the bar-shaped pattern PL1 close to the resolution limit of the imaging optical system 23 is substantially Gaussian, and the light quantity decreases back and forth around the peak value. I will do it. As a result, the time series distribution (hereinafter referred to as the light quantity signal distribution) AL of the light quantity detected by the photosensor PD is also substantially Gaussian, and the time series light quantity signal distribution AL and the spatial light quantity distribution GD are similar to each other. (See FIG. 4). However, the light quantity signal distribution AL here represents a locus obtained by continuously plotting the light quantity signal values detected according to the slit width Z with respect to the movement of the stage 12.

  In order for the light amount signal distribution AL and the light amount distribution GD to have a similar relationship, the slit width Z needs to be shorter than the bar-shaped pattern width K. By making it sufficiently short, the chevron shape of the light amount signal distribution AL becomes the light amount distribution GD. It becomes closer to the Yamagata shape. Here, the slit width Z is set to 0.1 to 0.5 times the bar-shaped pattern width K. Either the region setting of the micromirror for projecting the light of the bar-shaped pattern PL1 or the adjustment of the slit width Z is adjusted, or both are performed so as to obtain such a ratio.

  On the other hand, FIG. 5 shows a spatial light quantity distribution in a state where the subject is out of focus. Even in this case, the light amount distribution has a distribution shape that gradually increases and gradually decreases through the light amount peak P ′, but the light amount peak P ′ is smaller than the light amount peak P in the focused state. This is because the focal position does not coincide with the surface of the light shielding unit 40, that is, the surface of the substrate W, so that the range of the light amount distribution is expanded and the light intensity near the center is decreased.

  FIG. 6 is a diagram showing a spatial light quantity distribution according to the bar-shaped pattern row PT.

  FIG. 6 shows a light amount distribution obtained by connecting the spatial light amount distributions after passing through the slits of the four bar-shaped patterns PT1 to PT4. However, this distribution is a light amount distribution obtained when a slit is formed in accordance with the position of each bar-shaped pattern. In practice, a spatial light amount distribution is sequentially obtained in accordance with the passage of each bar-shaped pattern.

  The series of light quantity distributions represented in this way is represented by a periodic waveform (Nanami) 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 row PT is the same (= K), the center of the waveform coincides with both the focus position and the position out of focus. Therefore, the magnitude of the amplitude of the spatial light quantity distribution is a barometer indicating whether or not it is in the focus position, that is, the in-focus position.

  FIG. 7 is a graph showing a spatial light quantity distribution having different amplitude ratios.

  As shown in FIG. 7, there is a difference in the amplitude of the waveform between the in-focus state and the out-of-focus state. Also, different amplitudes can be obtained in the in-focus state according to the range of the focal depth. On the other hand, as described above, the waveform center position C does not substantially change even if the amplitude is different. This is because a light amount decrease near the light amount peak (the peak portion of the waveform) occurs, and at the same time, a complementary light amount increase portion occurs near the light amount bottom (the portion other than the waveform).

  Therefore, by setting the amplitude in the in-focus state as a reference and comparing the reference amplitude and the amplitude of the detected spatial light amount distribution without performing a focus adjustment operation with a change in the focal position, It is possible to monitor whether or not it is in focus. For example, the in-focus state can be monitored by obtaining a ratio between the reference amplitude and the detected amplitude and determining an in-focus state, that is, an amplitude ratio that falls within the range of the focal depth.

  As shown in FIG. 4, since the spatial light quantity distribution and the time-series light quantity distribution have a similar relationship, the light of the position detection pattern row PT is projected onto the light shielding unit 40 while moving the stage 12. Thus, a time-series light amount distribution similar to that in FIG. 7 can be obtained. In addition, since the magnitude of the amplitude of the time-series light quantity distribution detected by the photosensor PD corresponds to the magnitude of the amplitude of the spatial light quantity distribution, the amplitude ratio of the time-series light quantity distribution is spatial. This corresponds to the amplitude ratio of the light quantity distribution. Therefore, it is possible to determine the in-focus state based on the amplitude ratio in the time-series light amount distribution.

  When the light amount of the pattern row PT for position detection is constant, the center position C of the spatial light amount distribution is constant regardless of the in-focus state and the out-of-focus state, so the center position and the minimum or maximum light amount are detected. By doing so, the amplitude A can be calculated. The center 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 center position C is equal to the average light amount of one cycle (one line and one space pair) of the pattern row PT, the center position C is measured by measuring the light amount by providing a photometric unit such as a photosensor. You may obtain | require the average value of the light quantity of the made pattern row | line | column PT. Here, the center position C is obtained by integrating or averaging the time-series light quantity values obtained from the light transmitted through each slit in accordance with the period.

  On the other hand, for the amplitude (reference amplitude) B when the focal position of the imaging optical system 23 coincides with the surface of the substrate W, the light amount signal level (base light amount) detected when the pattern is not projected is detected. Thus, the amplitude B between the center position C and the detected light amount signal level can be obtained as the reference amplitude.

  When a photometric unit is provided for calculating the average light quantity, an independent photometric unit different from the light shielding unit and the photosensor may be provided, or the photometric unit may be used by the light shielding unit and / or the photosensor. May be. In that case, it is preferable to separately provide an opening at a position different from the above-described slit in the light shielding portion and measure the amount of light that has passed through the opening. As the opening, an opening having a translucent portion that is at least wider than the line width K of the pattern row PT, and preferably wider than the width PW of the entire pattern row PT may be provided. In addition, a photosensor for measuring the amount of light may be separately arranged, or photometry may be performed by the above-described photosensor.

  FIG. 8 is a graph showing a correlation between the focus movement amount and the amplitude ratio.

  FIG. 8 shows a graph in which the amplitude ratio calculated based on the light amount distribution detected while changing the focal position is plotted. 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 the closer the focal position is to the focal depth of the imaging optical system 23, the larger the amplitude ratio A / B. Is getting smaller.

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

  The controller 30 calculates the amplitude ratio based on the signal output from the light detection unit 28, and creates master data. Further, the focus position FP of the substrate W is stored in the memory 32. Then, an in-focus range AR centered on the in-focus position FP is determined.

  The focus position FP is determined at a position offset from the focus range AR0 having the largest amplitude ratio. This is because the position of the light shielding portion 40 and the position of the drawing surface of the substrate W are different by the thickness T (see FIG. 1) of the substrate W, and the light incident surface of the light shielding portion 40 is the mounting surface of the substrate W ( This is because it is installed at a position slightly lower than the stage surface. The width (upper limit, lower limit) of the focusing range AR depends 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, the required pattern order, and the like. Determined based on.

  FIG. 9 is a flowchart illustrating the focus state monitoring process. Here, after the focus adjustment prism 25 is adjusted to the focal position calculated in accordance with the substrate W to be used, the process is performed before the exposure operation of each substrate starts or every time a predetermined time elapses.

  The controller 30 controls the DMD drive circuit 24 to irradiate the bar-shaped pattern row 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), the focus position corresponding to the amplitude ratio M is selected from the master data stored in the memory 32. It is determined whether or not it is included in the range R (S103). The calculation of the amplitude ratio may be executed by the controller 30.

  When the focus position corresponding to the detected amplitude ratio M is out of the 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 focal position is out of the focusing range R. It is also possible to notify the operator by other notifying means such as generation of a buzzer sound other than the warning display.

  As described above, according to the first embodiment, by moving the stage 12, the pattern row PT including the bar-shaped patterns PL1 to PL4 is projected onto the light shielding unit 40 in which the slits ST1 to ST6 are formed. A light amount signal is output from the photosensor PD. Then, based on the amplitude ratio M obtained from the light quantity signal, it is determined whether or not the in-focus state is maintained.

  The focus or out-of-focus of the imaging optical system 23 is determined by scanning the substrate W with pattern light for focus detection without using a CCD whose resolution is limited by the pixel size or the like. The state can be detected with high accuracy. In addition, the focus range R determined for the master data stored in the memory has a monotonically decreasing rate of change in the amplitude ratio. Therefore, when a defocus occurs, the focus position deviates from the focus range R. It is possible to reliably detect the direction of being. On the other hand, since the light detection unit 28 is also used for exposure position detection, it is not necessary to install a dedicated CCD for focus detection, and the cost can be reduced.

  Moreover, even if pattern light passes through a plurality of slits and the average center value is calculated based on the relative movement amount, fluctuations in the light source and uneven sensitivity of the photosensor occur, the effect is suppressed. be able to. Furthermore, when the plurality of bar-shaped patterns pass through the plurality of slits, the parameter of the average value is expanded, and the amplitude ratio is accurately measured.

  The bar-shaped pattern of the focus detection pattern row does not have to be perpendicular to the main scanning direction. The pattern shape is determined in accordance with the slit forming direction, and the width of the slit in the main scanning direction so as to obtain the above-described continuous light quantity distribution. The main scanning direction width of the pattern light may be determined. As for the photo sensor, it is also possible to install a photo sensor for each scanning band.

  Next, a second embodiment will be described with reference to FIGS. In the second embodiment, the resolution performance of the imaging optical system is monitored. About another structure, 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, it is obtained by allowing one slit to pass light of a bar-like pattern close to the resolution performance limit. The spatial light amount distribution GD is a Gaussian distribution centered on the peak, and the light amount change (tilt) is relatively large at the edge of the bar-shaped pattern. However, when the resolution performance deteriorates, the spatial light quantity distribution GD1 has a gentle change in the light quantity at the edge of the bar-shaped pattern, and the peak light quantity decreases, resulting in a flat waveform light quantity distribution.

  As a result, in the continuous spatial light quantity distribution by the pattern row 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 the spatial light quantity distribution is reduced. Accordingly, the amplitude corresponding to the required minimum resolution performance is determined as a reference amplitude, and the amplitude is calculated by detecting the amplitude of the spatial light quantity distribution and calculating the amplitude ratio, as in the first embodiment. Image performance can be monitored.

  FIG. 11 is a graph showing a relationship between the resolving power and the amplitude ratio. FIG. 12 is a diagram showing a spatial light quantity distribution having a reference amplitude.

  In FIG. 11, a curve CG showing the correspondence between the resolving power and the amplitude ratio is drawn. However, the resolving power representing the horizontal axis of the graph in FIG. 11 represents the number of straight lines that can be imaged per unit length (1 mm) with respect to the imaging optical system 23. Since the amplitude decreases when the resolution performance decreases, the resolution decreases as the amplitude ratio value decreases. Therefore, if the measured amplitude ratio is larger than the limit (lower limit) amplitude ratio D0, the required resolution performance is maintained.

  A spatial light quantity distribution GD ′ shown in FIG. 12 indicates a 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 required resolution performance limit. . The waveforms of the spatial light quantity distributions GD1 and GD2 corresponding to the resolution performance limit are determined according to the specifications of the exposure apparatus and the optical performance of the imaging optical system 23 and the like.

  When the ratio (A0 / B) between the amplitude A0 of the spatial light quantity distribution GD ′ and the maximum amplitude B when the resolution performance is the highest is defined as the limit amplitude ratio D0, the ratio between the detected amplitude A and the reference amplitude B If A / B is D0 or more, it can be determined that the required resolution performance is satisfied. Data relating to the limit amplitude ratio D0 and the curve CG is stored in the memory 32 in advance.

  FIG. 13 is a diagram illustrating a flow of monitoring processing for resolution performance. As in the first embodiment, the process is performed at an arbitrary timing (at the start of lot production or every time a predetermined time elapses).

  The controller 30 controls the DMD drive circuit 24 so that the bar-shaped pattern row PT is irradiated toward the light shielding unit 40 while moving the stage 12 (S201). 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, the operator is informed of a decrease in resolution performance by a warning buzzer or the like (S204).

  As described above, according to the second embodiment, while moving the stage 12, the pattern row 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. A light amount signal is output from the photosensor PD. Then, based on the amplitude ratio M obtained from the light quantity signal, it is determined whether or not the resolution is lower than the limit resolution.

  In the first and second embodiments, it is considered that the center position (average light amount) of the light amount amplitude is constant because the line / space width of the pattern row is equal, and the reference amplitude in the focused state is determined as the average light amount and the pattern non-projection. Although it is calculated from the amount of light in the state, the reference amplitude may be calculated by other methods, and the amplitude ratio can be obtained even when the line / space widths of the pattern rows are not equal. For example, in the focus adjustment performed while moving the optical system or the substrate, the amplitude of the waveform light quantity in the in-focus state or the resolving power may be calculated, and the reference amplitude may be determined at the time of focus detection while taking into account the light source output fluctuation. .

  It should be noted that the L / S pattern light is projected onto an image sensor such as a CCD without projecting the bar-shaped pattern array while moving the stage, and the in-focus state or the resolution performance state is determined from the spatial light quantity distribution. You may judge.

10 Exposure Equipment 22 DMD (Light Modulation Element Array)
27 Calculation unit 28 Photodetection unit (photometry unit)
30 controller (exposure controller)
40 Light-shielding part PD Photo sensor

Claims (10)

A light modulation element array in which a plurality of light modulation elements are arranged in a matrix, and
A scanning unit that relatively moves the exposure area by the light modulation element array along the main scanning direction with respect to the drawing object;
An exposure control unit that controls the plurality of light modulation elements based on pattern data according to a relative position of the exposure area;
An imaging optical system that forms an image of the pattern light from the light modulation element array on the drawing surface of the drawing object;
A light shielding portion having at least one slit formed along the drawing surface;
A photometric unit that receives light transmitted through the slit;
A resolving power detection unit that detects resolving power of the imaging optical system based on an output from the photometry unit;
The exposure control unit projects line & space (L / S) pattern light while the exposure area moves relative to the light shielding unit,
The resolving power is lower than the limit resolving power based on the amplitude of the waveform light quantity detected by the projection of the L / S pattern light and the reference amplitude when the resolving power has a resolving power equal to or higher than a predetermined limit resolving power. An exposure apparatus characterized by detecting whether or not.   2. The exposure according to claim 1, wherein the focus detection unit determines whether or not the resolving power is lower than the limit resolving power based on an amplitude ratio that is a ratio between the detected amplitude and a reference amplitude. apparatus.   3. The exposure apparatus according to claim 2, wherein the resolving power detection unit determines whether or not the resolving power is lower than a limit resolving power based on a correspondence relationship between the amplitude ratio and the resolving power of the imaging optical system. .   The 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. The exposure apparatus according to claim 3. The light-shielding portion has an average light amount measurement opening,
5. The exposure apparatus according to claim 4, wherein the photometry unit includes an average light amount light receiving unit that receives L / S pattern light passing through the average light amount measurement opening.   4. The exposure apparatus according to claim 3, wherein a limit resolving power of the imaging optical system is determined based on an optical performance of the imaging optical system.   The exposure apparatus according to claim 1, further comprising a notifying unit that notifies that the resolution is lower than the limit resolution when the resolution is lower than the limit resolution.   An exposure position detection unit that detects an exposure position based on a light amount output from the photometry unit by projecting L / S pattern light while the exposure area moves relative to the light shielding unit. An exposure apparatus according to any one of claims 1 to 7. A photometric unit that receives line & space (L / S) pattern light that passes through the slit;
Detects whether or not the resolving power is lower than the limit resolving power based on the amplitude of the waveform light quantity detected by the projection of the L / S pattern light and the reference amplitude when the resolving power exceeds a predetermined limit resolving power A resolving power detection unit for an exposure apparatus, comprising: Receives line & space (L / S) pattern light that passes through the slit,
Detects whether or not the resolving power is lower than the limit resolving power based on the amplitude of the waveform light quantity detected by the projection of the L / S pattern light and the reference amplitude when the resolving power exceeds a predetermined limit resolving power A focus detection method for an exposure apparatus.

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