JP2010066415A - Calibration method of exposure power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately correct light quantity supplied from each light supply element even when light such as laser of high coherency is used, in an exposure apparatus constituted so as to emit light from light supply element groups arranged in line towards an object. <P>SOLUTION: Light is supplied from a peripheral light supply element positioned around a specific light supply element, of a plurality of light supply element groups, and, in a fixed state of the light quantity of the peripheral light supply element, the light quantity of the specific light supply element is varied from a first light quantity level to a second light quantity level. By measuring the variation amount of the light quantity distribution of the light supplied from the light supply element groups when the light quantity of the specific light supply element is thus varied, a profile function is generated expressing the variation amount of the light quantity distribution of the light supplied from the light supply element groups when only the light quantity of the specific light supply element is varied, and a control value for driving each light supply element is calibrated based on the profile function. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure power calibration method, and more particularly to the amount of light supplied from each light supply element in an exposure apparatus configured to emit light toward an object from a group of light supply elements arranged in a line. The present invention relates to a calibration method for correction.

  In an exposure apparatus that irradiates line-shaped light toward an object, for example, when it is desired to irradiate light uniformly on the exposure surface due to changes over time or optical characteristics that differ from exposure position to exposure position. There is a problem in that the distribution of the amount of light is not uniform and the exposure result is adversely affected. In order to solve such a problem, various methods for calibrating the amount of light on the exposure surface have conventionally existed.

  In Patent Document 1, all of a plurality of light emitting portions are simultaneously turned on to expose a photosensitive material, the photosensitive material is developed to measure a color density, and a variation in light amounts of the plurality of light emitting portions is determined based on the measurement result. A calibration method for correction is disclosed.

In Patent Document 2, in order to equalize the light emission amount of each light emitting dot in a line light source having a plurality of light emitting dots, the light amount distribution of light emitted from each light emitting dot is individually measured, and adjacent light emission A calibration method is disclosed in which the light quantity of each light emitting dot is corrected in consideration of leakage light emission to an area to be exposed by the dot.
JP-A-9-127485, page 7-8 and FIG. 5 (A). Japanese Patent No. 3269425

  However, the calibration method described in Patent Document 1 has a problem that it takes time and effort to develop the photosensitive material, and the variation in light quantity cannot be corrected quickly and easily.

  Further, in the calibration method described in Patent Literature 2, interference of light from two adjacent light emitting dots (light is strengthened or weakened according to the phase relationship of light from the two light emitting dots) is considered. In addition, when this method is applied to a light-emitting device using light such as a laser having high coherency, there is a problem that accurate correction cannot be performed.

  Therefore, the present invention provides an exposure apparatus configured to emit light toward an object from a group of light supply elements arranged in a line, even when using light such as a laser having high coherency, from each light supply element. It is an object to make it possible to correct the amount of light supplied with high accuracy.

  In order to achieve the above object, the present invention is configured as follows. Note that the reference numerals and figure numbers in parentheses show examples of correspondence with the drawings in order to help understanding of the present invention, and do not limit the scope of the present invention.

  In the calibration method of the present invention, each light supply element (32b) in the exposure apparatus (1) configured to emit light from the light supply element group (31) arranged in a line toward the object (20). It is the calibration method which correct | amends the light quantity supplied from. In the calibration method, a peripheral light emitting step (S20) for supplying light from a peripheral light supply element located around a specific light supply element in the light supply element group, and a light amount of the peripheral light supply element are fixed. In this state, the light quantity changing step (S22) for changing the light quantity of the specific light supply element from the first light quantity level to the second light quantity level, and the light quantity of the specific light supply element in the light quantity change process. By measuring the amount of change in the light quantity distribution of the light supplied from the light supply element group when changed, the light supply element group supplied from the light supply element group when only the light quantity of the specific light supply element is changed is measured. A profile function generation step (S24) for generating a profile function representing the amount of change in the light amount distribution of the light to be stored in the storage device, and the control value for driving each light supply element Calibration step of calibrating based on a function (S11, S12) and a.

  In the light amount changing step, the light amount of the specific light supply element may be changed from the first light amount level to the second light amount level in a state where the light amount of the peripheral light supply element is fixed to a halftone. Good.

  The calibration step includes a correction function determination step (S11) for determining a correction function based on the profile function, and the light supply elements by driving each light supply element with a predetermined individual control value. A light emitting step (S40) for supplying light from the group, a light amount distribution measuring step (S41) for measuring a light amount distribution of the light supplied from the light supplying element group, and a light amount distribution measured in the light amount distribution measuring step. A difference calculation step (S42) for calculating a difference from the target light amount distribution, and a correction amount calculation step (S43) for calculating a correction amount of the control value of each light supply element by convolution integration of the difference and the correction function. And by correcting the control value of each light supply element used in the light emitting step according to the correction amount of the control value of each light supply element calculated in the correction amount calculation step, Serial control value update step of updating the control value of each light supply device for realizing the target light amount distribution (S44) and may contain.

  The correction function is such that the received light amount in the light receiving region corresponding to the light supplying element other than the specific light supplying element is not changed, and only the received light amount in the light receiving region corresponding to the specific light supplying element is a unit amount. It may be a function that represents the amount of change in the amount of light of each light supply element when only the change is made.

  The correction function determination step includes a correction coefficient automatic selection step (S30, S31) for automatically selecting a correction function corresponding to the profile function from a plurality of correction functions prepared in advance. May be.

  The correction function determination step includes a first step (S30) of selecting a typical profile function corresponding to the profile function from a plurality of typical profile functions prepared in advance, and pre-associating with the selected typical profile function. A second step (S31) of determining the obtained correction function as a correction function corresponding to the profile function.

  The correction function determination step may further include a third step (FIG. 17) for correcting the correction function determined in the second step according to the profile function.

  Re-emission step (S50) for supplying light from the light supply element group by driving each light supply element with the control value updated in the control value update process, and light supplied from the light supply element group Based on the light quantity distribution measured in the light quantity distribution re-measurement step and the light quantity distribution re-measurement step (S51) for measuring the light quantity distribution, the control value of each light supply element for realizing the target light quantity distribution is re- A calibration result evaluation step (S52) for determining whether or not it is necessary to update, and when it is determined in the calibration result evaluation step that the control value of each light supply element needs to be updated again, The difference calculation step, the correction amount calculation step, and the control value update step may be re-executed using the light amount distribution measured in the light amount distribution re-measurement step (S55).

  Re-emission step (S50) for supplying light from the light supply element group by driving each light supply element with the control value updated in the control value update process, and light supplied from the light supply element group Whether or not the correction function determined in the correction function determination step is appropriate based on the light amount distribution re-measurement step (S51) for measuring the light amount distribution and the light amount distribution measured in the light amount distribution re-measurement step. A correction function evaluation step (S53) for determining whether or not the correction function is determined to be inappropriate in the correction function evaluation step (S54). In addition, using the new correction function changed in the correction function changing step, the light emission step, the light quantity distribution measurement step, the difference calculation step, the correction amount calculation Extent and may be re-run the control value updating step (S55).

  The exposure apparatus may emit coherent light from the light supply element group toward the object.

  The exposure apparatus may include a diffraction grating light modulation element as the light supply element group.

  An exposure apparatus according to the present invention is an exposure apparatus (1) configured to emit light toward a target from a group of light supply elements arranged in a line, and is supplied from each light supply element by the calibration method. Calibration means (50) for correcting the amount of light to be emitted.

  According to the present invention, in an exposure apparatus configured to emit light toward an object from a group of light supply elements arranged in a line, even when using light such as a laser with high coherency, from each light supply element The amount of light supplied can be corrected with high accuracy.

  1 and 2 are diagrams showing the configuration of an exposure apparatus 1 according to an embodiment of the present invention. The exposure apparatus 1 draws a pattern by irradiating the object (photosensitive material) with light that is spatially modulated based on input image data. The exposure apparatus 1 includes a stage 11 for placing a substrate 20 coated with a photoresist, and a stage moving mechanism 10 for moving the stage 11 in the Y direction (main scanning direction) and the X direction (sub scanning direction). And eight drawing heads 30 that irradiate the substrate with spatially modulated line-shaped light toward the substrate, and image data input to light modulators 31 (details will be described later) included in the respective drawing heads 30. The modulation control unit 60 that is driven based on the above and the adjustment unit 50 that adjusts the operation of the modulation control unit 60 are provided.

  The stage moving mechanism 10 moves the stage 11 in the Y direction (main scanning), and moves the stage 11 in the X direction (sub scanning) to the start position of the next main scanning every time the main scanning ends. Then, the next main scan is performed in the opposite direction to the previous main scan. As described above, in the exposure apparatus 1, the eight drawing heads 30 can be moved relative to the stage 11 in the X direction and the Y direction by the stage moving mechanism 10.

  The exposure apparatus 1 further includes a sensor unit disposed on the stage 11 side of the stage moving mechanism 10. The sensor unit receives the light from the drawing head 30, the sensor stage 45 with the light receiving element 40 fixed on the upper surface, and the output from the light receiving element 40 with the upper surface of the sensor stage 45 being processed. The sensor processing unit 44 is provided. In the present embodiment, a photodiode is used as the light receiving element 40. As shown in FIG. 1, the light receiving surface of the light receiving element 40 and the upper surface of the substrate 20 are located at the same height.

  As a mechanism for moving the sensor unit in the X direction (sub-scanning direction), the exposure apparatus 1 has a ball screw 43 that faces the X direction to which the sensor stage 45 is attached and a X direction that supports the sensor stage 45. Two guide rails 41 a and 41 b and a motor 42 connected to the ball screw 43 are provided. When the modulation control unit 60 is calibrated, the ball screw 43 is rotated by the motor 42, so that the light receiving element 40 and the sensor processing unit 44 together with the sensor stage 45 along the guide rails 41a and 41b in the X direction (sub-scanning direction). The light from the drawing head 30 is sequentially received by the light receiving element 40 and sent to the sensor processing unit 44. Then, the data calculated by the sensor processing unit 44 is output to the adjustment unit 50.

  Next, the drawing head 30 will be described in more detail.

  The drawing head 30 includes an illumination optical system including an illumination lens into which laser light emitted from a laser light source is incident, an optical modulator 31, and an imaging optical system including a prism, an imaging lens, and a lens. The laser light source is a light source that emits laser light having a peak wavelength in the range of 800 nm to 820 nm. The laser light emitted from the illumination optical system is applied to the light modulator 31. In the present embodiment, a diffraction grating type light modulation element is used as the light modulator 31. Details of the optical modulator 31 will be described later. The laser light applied to the optical modulator 31 is divided and modulated into a large number by the optical modulator 31 and then reflected as diffracted light. Of the diffracted light, the 0th-order diffracted light is reflected on the substrate 20 through the imaging optical system. The image is formed on the light receiving element 40 during calibration.

  FIG. 3 is a plan view showing the structure of the light modulator (diffraction grating type light modulation element) 31, and FIG. 4 is a partial perspective view thereof.

  As shown in FIG. 3, the optical modulator 31 has a configuration in which several thousand (16384 as an example in this embodiment) reflectors (hereinafter referred to as ribbons) 32 are arranged in a row on a support base 33. Have. More specifically, as shown in FIG. 4, these ribbons 32 are composed of fixed ribbons 32a and movable ribbons 32b arranged alternately. A metal thin film is formed on the surface of the ribbon 32 so as to function as a reflection mirror and an electrode, and a common electrode is provided below the ribbon 32 with a release layer therebetween.

  The fixed ribbon 32a is configured to have a fixed surface position. On the other hand, the movable ribbon 32b is configured such that a part of the effective movable region on the surface descends according to the applied voltage. When no voltage is applied to each movable ribbon 32b, the surfaces of all the fixed ribbons 32a and the surfaces of the movable ribbons 32b are arranged on the same plane. When a voltage is applied to the movable ribbon 32b, the movable ribbon 32b is lowered by a width corresponding to the applied voltage, and the same effect as that of the reflective diffraction grating is obtained due to the difference in height from the adjacent fixed ribbon 32a. For this reason, the light modulator 31 reflects the 0th-order diffracted light of the laser beam to be illuminated when no voltage is applied to the movable ribbon 32b, and the voltage is applied to the movable ribbon 32b. In, two positive and negative first-order diffracted lights and higher-order diffracted lights are reflected. Therefore, when the surface of the optical modulator 31 is illuminated with laser light, a large number of diffracted lights that can be modulated independently of each other are obtained. As such an optical modulator 31, as described above, a grating light valve (Grating Light Valve: trademark of Silicon Light Machines) manufactured by Silicon Light Machines of the United States, also called GLV, may be used. it can.

  A voltage can be individually applied to each movable ribbon 32 b of the optical modulator 31. In the present embodiment, the optical modulator 31 has 16384 ribbons 32, of which 8192 is the movable ribbon 32b, so that the optical modulator 31 of the present embodiment has 8192 light supply elements. In other words, it is composed of groups. Hereinafter, as shown in FIG. 5, the minimum control unit of the optical modulator 31 (that is, the minimum unit capable of individually controlling the voltage) is referred to as a “channel”.

  The modulation control unit 60 drives each movable ribbon 32b of the light modulator 31 based on a control value (digital) corresponding to input image data. Specifically, the control value of each channel corresponding to the input image data is converted into a voltage by a DA converter circuit, and these voltages are applied to the movable ribbon 32b of each channel. In the present embodiment, input image data has five levels of gradation, and accordingly, the modulation control unit 60 performs gradation control of five levels for each channel.

  FIG. 6 shows a control value table that is referred to when the modulation control unit 60 drives the optical modulator 31. This control value table is held in an arbitrary storage device provided inside or outside the modulation control unit 60. For example, when the light amount level of the first channel corresponding to the input image data is L1, the modulation control unit 60 refers to the control value table and moves the movable ribbon 32b of the first channel to the control value V1 ( 1) (that is, a voltage corresponding to the control value V1 (1) is applied to the movable ribbon 32b of the first channel). Similarly, when the light quantity level of the second channel corresponding to the input image data is L5, the modulation control unit 60 refers to the control value table and sets the movable ribbon 32b of the second channel to the control value V5. Driven in (2) (that is, a voltage corresponding to the control value V5 (2) is applied to the movable ribbon 32b of the second channel).

  Note that, based on the control value table as shown in FIG. 6, when the movable ribbon 32b is driven with a control value corresponding to the same light amount level (for example, the light amount level L1) for all channels, the output from the light modulator 31. The distribution of the amount of light that is generated may not be uniform. For example, FIG. 7 shows an example of the difference between the target light amount distribution and the actual light amount distribution. Therefore, in the present embodiment, calibration processing is executed by the adjustment unit 50 in order to obtain a target light amount distribution. Hereinafter, the details of the calibration process by the adjustment unit 50 will be described.

  FIG. 8 is a flowchart showing the flow of calibration processing by the adjustment unit 50.

  When the calibration process is started, first, in step S10, the adjustment unit 50 executes a profile function generation process. The profile function is a function that represents the amount of change in the light amount distribution when only the light amount of a specific channel is changed in a state where the light amount of a channel around the specific channel is fixed. Details of the profile function generation process will be described below with reference to FIGS.

  In the present embodiment, as shown in FIG. 9, the first channel to the 8192th channel of the optical modulator 31 are divided into eight sections, and a profile function is generated for each of these eight sections. For example, the first section is a range from the first channel to the 1000th channel, and the specific channel for the first section is the 500th channel at the center of the range. Similarly, the second section is the range from the 1001st channel to the 2000th channel, and the specific channel for the second section is the first 1500 channel in the center of the range.

  FIG. 10 is a flowchart showing details of the profile function generation processing by the adjustment unit 50. In the present embodiment, the profile function is generated individually for each of the eight sections. That is, a profile function is individually generated for each of the above eight sections, and calibration processing (correction function determination processing and control value update processing described later) is performed based on the profile function of each section. .

  When the profile function generation process is started, in step S20, the adjustment unit 50 makes the intermediate ribbons of the movable ribbons 32b of all the channels through the modulation control unit 60 (for example, an intermediate level between the minimum light amount level and the maximum light amount level). Drive with.

  In step S <b> 21, the adjusting unit 50 controls the stage moving mechanism 10 and the motor 42 to move the light receiving element 40 in the X direction below the drawing head 30, and the laser light emitted from the light modulator 31. The light quantity distribution is measured, and the measured light quantity distribution is stored in an arbitrary storage device. An example of the light quantity distribution measured here is shown in FIG. However, FIG. 11 shows the light amount distribution in the peripheral region of the specific channel.

  In step S <b> 22, the adjustment unit 50 changes only the light amount of the specific channel to the maximum level through the modulation control unit 60 while fixing the light amount of the remaining channels at the halftone.

  In step S23, the adjustment unit 50 measures the light amount distribution of the laser light emitted from the light modulator 31 in the same manner as in step S21, and stores the measured light amount distribution in an arbitrary storage device. An example of the light quantity distribution measured here is shown in FIG. However, FIG. 12 shows the light amount distribution in the peripheral region of the specific channel.

  In step S24, the adjustment unit 50 calculates a difference between the light amount distribution measured in step S21 and the light amount distribution measured in step S23, and stores the difference as a profile function f (x) in an arbitrary storage device. To do. For example, FIG. 13 shows a profile function f (x) calculated from the light quantity distribution of FIG. 11 and the light quantity distribution of FIG. According to the profile function f (x) of FIG. 13, if only the light amount of the k-th channel (k is an arbitrary natural number) is increased while the light amounts of the other channels are fixed, the k-th channel and the number of channels are increased accordingly. It can be seen that the amount of light received in the light receiving region corresponding to the k + 1 channel decreases, and the amount of light received in the light receiving regions corresponding to the k-2 and k + 2 channels increases.

  In this embodiment, the movable ribbons 32b of all the channels are driven in halftone in step S20, but the influence when the light amount of the specific channel is changed is only in the vicinity of the light receiving region corresponding to the specific channel. Therefore, it is only necessary to drive the movable ribbon 32b of at least peripheral channels of the specific channel (for example, when the Nth channel is the specific channel, all five channels from the N-2th channel to the N + 2th channel) in halftone. The remaining channels may be turned off (minimum light level).

  Further, in the present embodiment, the profile function f (x) is calculated by changing the light amount of a specific channel from the same state as the light amount of other channels to the maximum level and calculating the difference in the light amount distribution before and after the change. However, the light intensity distribution of a specific channel is changed from an arbitrary level (for example, the minimum light intensity level) to another arbitrary level (for example, the maximum light intensity level). The profile function f (x) may be generated by calculating the difference.

  Note that when generating the profile function f (x), the light amount of the specific channel is changed in a halftone state instead of turning off the light amount of the channels around the specific channel. This is to check whether the amount of light received in the light receiving region corresponding to the peripheral channel increases or decreases due to interference between the light of the specific channel and the light of the peripheral channel.

  In the present embodiment, the profile function f (x) is generated by changing the light amount of one channel as a specific channel every eight sections, but the present invention is not limited to this. The profile function f (x) may be generated by setting a plurality of adjacent channels as specific channels and changing the light quantity of those channels. For example, in the section from the first channel to the 1000th channel, the profile function f (x) may be generated using three adjacent channels of the 499th channel to the 501st channel as specific channels. As a result, even if the change in the light amount distribution is small and the profile function f (x) cannot be appropriately generated by changing the light amount of one channel, the light amount distribution can be obtained by changing the light amount of the plurality of channels. It is possible to appropriately generate the profile function f (x) by increasing the change of.

  Note that the shape of the profile function f (x) changes depending on various factors, and particularly changes over time. Therefore, it is desirable to generate the profile function every time calibration is executed.

  Strictly speaking, the profile function f (x) varies depending on the position of a specific channel (that is, which channel is set as the specific channel). Particularly, when the profile function f (x) is generated with the first channel as the specific channel and when the profile function f (x) is generated with the 8192th channel as the specific channel, the shape of the profile function f (x) is It can be very different. However, if the channels are relatively close to each other, the profile function f (x) when these channels are generated as specific channels is expected to have a substantially similar shape. Therefore, in this embodiment, as shown in FIG. 9, all 8192 channels are divided into eight sections, and a common profile function f (x) is generated for each of these sections. This makes it possible to perform appropriate calibration, shorten the calibration time, and save a storage area (an area for temporarily storing a profile function). However, in the present invention, it is not always necessary to divide all channels into a plurality of sections and perform the profile function f (x) for each section.

  Note that the profile function f (x) of a specific section may be obtained by interpolation from the profile functions f (x) of other sections. For example, the profile function f (x) in the second section may be linearly interpolated from the profile functions f (x) in the first section and the third section in FIG. As a result, the calibration time can be shortened and the storage area (area for temporarily storing the profile function) can be saved.

  In FIG. 8, when the profile function generation process in step S10 is completed, in the subsequent step S11, the adjustment unit 50 executes a correction function determination process. The correction function is a function used to update the control value, and only the received light amount in the light receiving region corresponding to the specific channel is changed without changing the received light amount in the light receiving region corresponding to the channel other than the specific channel. It is a function representing the amount of change in the light amount of each channel when the amount is changed by an amount (for example, 1 mW). Details of the correction function determination process will be described below with reference to FIGS. In the present embodiment, the correction function is determined for each of the eight sections shown in FIG. That is, for each of the eight sections shown in FIG. 9, the correction function is individually determined using the corresponding profile function generated in the profile function generation process.

  When the correction function determination process is started, first, in step S30, the adjustment unit 50 is prepared and stored in advance based on the profile function f (x) generated by the profile function generation process in step S10 of FIG. A typical profile function most similar to the profile function f (x) is selected from among a plurality of typical profile functions recorded in the apparatus by pattern matching. FIG. 15 shows a specific example of the typical profile function. In this case, the second typical profile function is selected as the typical profile function most similar to the profile function f (x) in FIG. As a pattern matching method, any known method can be used. For example, pattern matching may be performed using an index such as a full width at half maximum or a correlation coefficient. Each typical profile function is associated with a correction function h (x) prepared in advance.

  In step S31, the adjustment unit 50 determines the correction function h (x) associated with the typical profile function selected in step S30 as the correction function h (x) to be used in the control value update process described later. To do. For example, when the second typical profile function is selected in step S30, the correction function h (x) to be used in the control value update process is used as the second correction function associated with the second typical profile function. Determine as. Note that when the shape of the profile function f (x) is, what shape correction function h (x) should be used can be determined by a mathematical method or an empirical law. In the present embodiment, for each typical profile function, a corresponding correction function h (x) is obtained in advance mathematically or empirically and associated with the typical profile function.

  Note that the correction function h (x) prepared in advance may be appropriately corrected according to the shape of the profile function f (x). For example, as shown in FIG. 16, when the peak position of the profile function f (x) is shifted in the plus direction by one channel, as shown in FIG. 17, the correction function h selected in step S31. The correction function h (x) may be corrected so that the peak position of (x) is shifted by one channel in the negative direction.

  In the present embodiment, as described above, the typical profile function corresponding to the profile function f (x) is first selected, and the correction function h (x) is determined according to the typical profile function. The invention is not limited to this. For example, an optimal correction function h (x) is selected from a plurality of correction functions h (x) prepared in advance based on the shape (various feature amounts) of the profile function f (x). Therefore, you may make it the adjustment part 50 select automatically. For example, the adjustment unit 50 may mathematically calculate the correction function h (x) from the profile function f (x) in real time.

  In FIG. 8, when the correction function determination process in step S11 is completed, in the subsequent step S12, the adjustment unit 50 executes a control value update process. Details of the control value update process will be described below with reference to FIGS. In this embodiment, the control value is updated individually for each of the eight sections shown in FIG. That is, for each of the eight sections shown in FIG. 9, the control values are individually updated using the corresponding correction function generated in the correction function determination process.

  When the control value update process is started, first, in step S40, the adjustment unit 50 drives the movable ribbons 32b of all channels through the modulation control unit 60 with a control value corresponding to the target light amount distribution. For example, in the control value table shown in FIG. 6, when it is desired to calibrate the control value of each channel of the light quantity level L1, the first channel is the control value V1 (1) and the second channel is the control value V1 (2). Then, the third channel is driven with the control value V1 (3),..., And the 8192 channel is driven with the control value V1 (8192). Similarly, when it is desired to calibrate the control value of each channel at the light amount level L2, the first channel is controlled by the control value V2 (1), the second channel is controlled by the control value V2 (2), and the third channel is controlled by the control value. With V2 (3)..., The 8192st channel is driven with the control value V2 (8192). Below, the case where the control value of each channel of the light quantity level L1 is calibrated is demonstrated. In step S40, instead of driving the movable ribbons 32b of all the channels with a control value corresponding to the target light amount distribution, the movable ribbons 32b of the respective channels may be driven at an arbitrary light amount level.

  In step S41, the adjustment unit 50 measures the light amount distribution of the laser light emitted from the light modulator 31 in the same manner as in step S21, and stores the measured light amount distribution in an arbitrary storage device. An example of the light amount distribution measured here is shown in FIG.

  In step S42, the adjusting unit 50 determines the difference g (x) between the actual light amount distribution measured in step S41 and the target light amount distribution (that is, “target light reception for each light receiving region corresponding to each channel). A function representing a difference between “amount” and “actual light reception amount” is calculated. An example of the difference g (x) calculated here is shown in FIG.

  In step S43, the adjustment unit 50 calculates the difference g (x) calculated in step S42 and the correction function h (x for the corresponding section determined in the correction function determination process in step S11 of FIG. 8 described above. ) And the convolution integral to calculate the control value correction amount for each channel. An example of the correction amount of the control value of each channel calculated here is shown in FIG. In FIG. 21, C (1), C (2), C (3), and C (8192) are the correction amount of the control value of the first channel, the correction amount of the control value of the second channel, and the third channel, respectively. The control value correction amount and the control value correction amount for channel 8192 are shown.

  In step S44, the adjustment unit 50 updates the corresponding control value in the control value table shown in FIG. 6 according to the correction amount of the control value of each channel calculated in step S43. Specifically, as shown in FIG. 22, the light amount level L1 is obtained by adding the correction amount C (1) to the control value V1 (1) _old of the first channel before update corresponding to the light amount level L1. The control value V1 (1) _new of the updated first channel corresponding to is determined. Similarly, the updated second channel corresponding to the light amount level L1 is added by adding the correction amount C (2) to the control value V1 (2) _old of the second channel before updating corresponding to the light amount level L1. The control value V1 (2) _new is determined. The same applies to the remaining channels.

  In step S43, the correction amount of the control value of each channel is obtained on the assumption that the relationship between the control value of each channel and the amount of light is linear. However, if the relationship between the control value of each channel and the amount of light is not linear (or if it is inappropriate to approximate it to be linear), the value of the correction amount of each channel obtained in step S43 is, for example, Correcting may be performed as appropriate based on a light amount characteristic curve indicating the relationship between the control value and the light amount (non-linear relationship) as shown in FIG.

  Further, the value of the correction amount of each channel obtained in step S43 may be appropriately corrected by PID control.

  When the calibration process as described above is completed, ideally, the light amount distribution output from the light modulator 31 based on the updated control value should completely match the target light amount distribution. Actually, due to various factors, for example, as shown in FIG. 24, the light amount distribution actually output from the optical modulator 31 based on the updated control value does not completely match the target light amount distribution. Normally, by repeatedly executing the control value update process in step S12 of FIG. 8, the light amount distribution actually output from the light modulator 31 gradually approaches the target light amount distribution. However, in a special case, as the control value update process is repeated, the difference between the light amount distribution actually output from the light modulator 31 and the target light amount distribution may increase in reverse. As a typical case in which such a situation occurs, there is a case where an inappropriate correction function h (x) is selected in the correction function determination process in step S11. Therefore, it is desirable to perform a verification process for verifying the effect of the calibration process after the control value update process in step S12 of FIG. Hereinafter, the verification process will be described with reference to FIG.

  When the verification process is started, first, in step S50, the adjustment unit 50 drives the movable ribbons 32b of all the channels through the modulation control unit 60 with the control values updated by the immediately previous control value update process.

  In step S51, the adjustment unit 50 measures the light amount distribution of the laser light emitted from the optical modulator 31 in the same manner as in step S21, and stores the measured light amount distribution in an arbitrary storage device.

  In step S52, the adjustment unit 50 determines whether or not the error of the actual light amount distribution measured in step S51 with respect to the target light amount distribution is within an allowable range (that is, whether or not the renewal of the control value is unnecessary). If the error is within the allowable range, the verification process is terminated. If the error is not within the allowable range, the process proceeds to step S53. As a method for determining whether the error is within the allowable range, an arbitrary method according to the required accuracy may be used from various known methods. For example, a mean square error, an SNR (signal-to-noise ratio), a correlation coefficient, or the like may be used as an index representing the error.

  In step S53, the adjustment unit 50 determines whether or not the error of the actual light amount distribution measured in step S51 with respect to the target light amount distribution is reduced as compared with that before execution of the control value update process performed immediately before. If the error is reduced, the process proceeds to step S55. If the error is not reduced, the process proceeds to step S54.

  The fact that the error of the actual light amount distribution measured in step S51 with respect to the target light amount distribution is not reduced as compared with the one before the execution of the control value update process performed immediately before is the control value update process. This means that the correction function h (x) used is not appropriate. Therefore, in step S53, it can be said that the adjustment unit 50 determines whether the correction function h (x) is appropriate.

  In step S54, the adjustment unit 50 changes the correction function h (x). For example, from among a plurality of correction functions h (x) prepared in advance, a correction function h (x) different from the correction function h (x) used in the control value update process performed immediately before. Select.

  In step S55, the adjustment unit 50 performs a control value update process. Since this control value update process is the same as the control value update process in step S12 of FIG. 8, the description thereof is omitted here.

  When the control value update process in step S55 ends, the process returns to step S50.

  The correction function h (x) is applied as necessary until the error between the light amount distribution actually output from the light modulator 31 and the target light amount distribution falls within the allowable range by the verification process as described above. The control value update process is repeated while changing. If the error between the light amount distribution actually output from the light modulator 31 and the target light amount distribution does not fall within the allowable range even when the control value update process is repeated a certain number of times, an error notification is sent to the user. The calibration process may be terminated by performing the above.

  As described above, according to the present embodiment, the light amount distribution of the light modulator 31 can be corrected with high accuracy.

  In this embodiment, a diffraction grating type light modulation element is used as the light modulator 31. However, the present invention is configured to emit light from a group of light supply elements arranged in a line toward a target. It can be applied to other exposure apparatuses. The light supply element group arranged in a line is not limited to the reflective type as in the present embodiment, but may be a self-luminous type or a transmissive type.

  The numerical values such as the number of drawing heads 30, the number of ribbons 32 in the optical modulator 31, and the number of gradations of image data shown in the present embodiment are merely examples, and are not limited to these numerical values. .

  The present invention provides a light quantity supplied from each light supply element in an exposure apparatus using light such as a laser having high coherency, which is configured to emit light toward a target from a group of light supply elements arranged in a line. This is suitable as a calibration method for correcting the image with high accuracy.

External view of exposure apparatus 1 External view of exposure apparatus 1 The figure which shows the structure of the optical modulator 31 Partial perspective view of the optical modulator 31 The figure which shows the structure of the optical modulator 31 The figure which shows an example of a control value table An example of the light intensity distribution before the calibration process Flow chart showing the flow of calibration process Specific channel setting example Flow chart showing details of profile function generation processing Example of measurement result of light distribution Example of measurement result of light distribution Example of profile function Flow chart showing details of correction function determination processing Example of typical profile function and correction function prepared in advance Example of profile function Example of correction of correction function according to profile function Flow chart showing details of control value update processing Example of measurement result of light distribution Example of difference between measured light quantity distribution and target light quantity distribution An example of the amount of light correction for each channel calculated based on the difference and the correction function Example of control value update contents Example of light intensity characteristic curve Example of light intensity distribution after control value correction processing Flow chart showing details of verification process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 10 Stage moving mechanism 11 Stage 20 Substrate 30 Drawing head 31 Optical modulator 32 Reflector (ribbon)
32a Fixed Ribbon 32b Movable Ribbon 33 Support Base 40 Photodetector 41a, 41b Guide Rail 42 Motor 43 Ball Screw 44 Sensor Processing Unit 45 Sensor Stage 50 Adjustment Unit 60 Modulation Control Unit

Claims (11)

A calibration method for correcting the amount of light supplied from each light supply element in an exposure apparatus configured to emit light toward an object from a group of light supply elements arranged in a line,
A peripheral light emitting step of supplying light from an ambient light supply element located around a specific light supply element in the light supply element group;
A light amount changing step of changing the light amount of the specific light supply element from the first light amount level to the second light amount level in a state where the light amount of the peripheral light supply element is fixed;
Only the light amount of the specific light supply element is measured by measuring the amount of change in the light amount distribution of the light supplied from the light supply element group when the light amount of the specific light supply element is changed in the light amount change step. A profile function generation step of generating a profile function representing a change amount of the light amount distribution of the light supplied from the light supply element group when it is changed and storing it in a storage device;
And a calibration step of calibrating a control value for driving each light supply element based on the profile function.   In the light amount changing step, the light amount of the specific light supply element is changed from a first light amount level to a second light amount level in a state where the light amount of the peripheral light supply element is fixed to a halftone. The calibration method according to claim 1. The calibration step includes
A correction function determining step for determining a correction function based on the profile function;
A light emitting step of supplying light from the light supply element group by driving each light supply element with a predetermined individual control value;
A light amount distribution measuring step for measuring a light amount distribution of light supplied from the light supply element group;
A difference calculating step for calculating a difference between the light amount distribution measured in the light amount distribution measuring step and the target light amount distribution;
A correction amount calculating step of calculating a correction amount of the control value of each light supply element by convolution integration of the difference and the correction function;
By correcting the control value of each light supply element used in the light emission step according to the correction amount of the control value of each light supply element calculated in the correction amount calculation step, to realize the target light amount distribution The calibration method according to claim 1, further comprising a control value update step of updating a control value of each light supply element.   The correction function determining step includes a correction coefficient automatic selection step of automatically selecting a correction function corresponding to the profile function from a plurality of correction functions prepared in advance. Calibration method.   The correction function determining step includes a first step of selecting a typical profile function corresponding to the profile function from a plurality of typical profile functions prepared in advance, and a correction associated in advance with the selected typical profile function The calibration method according to claim 3, further comprising a second step of determining a function for use as a correction function corresponding to the profile function.   The calibration method according to claim 5, wherein the correction function determination step further includes a third step of correcting the correction function determined in the second step according to the profile function. A re-emission step of supplying light from the light supply element group by driving each light supply element with the control value updated by the control value update step;
A light amount distribution re-measurement step of measuring a light amount distribution of light supplied from the light supply element group;
A calibration result evaluation step for determining whether or not it is necessary to re-update the control value of each light supply element for realizing the target light amount distribution based on the light amount distribution measured in the light amount distribution re-measurement step; Further comprising
When it is determined in the calibration result evaluation step that the control value of each light supply element needs to be updated again, it is measured in the light amount distribution re-measurement step instead of the light amount distribution measured in the light amount distribution measurement step. The calibration method according to claim 3, wherein the difference calculation step, the correction amount calculation step, and the control value update step are re-executed using the obtained light amount distribution. A re-emission step of supplying light from the light supply element group by driving each light supply element with the control value updated by the control value update step;
A light amount distribution re-measurement step of measuring a light amount distribution of light supplied from the light supply element group;
A correction function evaluation step for determining whether or not the correction function determined in the correction function determination step is appropriate based on the light amount distribution measured in the light amount distribution re-measurement step;
A correction function changing step of changing the correction function when it is determined that the correction function is not appropriate in the correction function evaluation step,
Using the new correction function changed in the correction function changing step, the light emission step, the light amount distribution measurement step, the difference calculation step, the correction amount calculation step, and the control value update step are re-executed. The calibration method according to claim 3, wherein:   The calibration method according to claim 1, wherein the exposure apparatus emits coherent light from the light supply element group toward the object.   The calibration method according to claim 1, wherein the exposure apparatus includes a diffraction grating light modulation element as the light supply element group.   It is an exposure apparatus comprised so that light may be emitted toward the target object from the light supply element group located in a line form, Comprising: Each light supply element by the calibration method as described in any one of Claims 1-10 An exposure apparatus comprising calibration means for correcting the amount of light supplied from.

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