JP2007287817A - Method of calibrating aligner and aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of calibrating an aligner which can accurately detect illumination distribution within an exposure area on a substrate. <P>SOLUTION: The method includes a first measuring step to measure illumination distribution on a sensitive substrate by using a light reflected on the reflection surface of a reference plate that is arranged on the same plane as a reflection type mask, a second measuring step to measure illumination distribution on the sensitive substrate by placing a calibration mask having a reflection surface as reference on a mask stage and using a light reflected on the reflection surface of the calibration mask, an illumination distribution calculation step to calculate illumination distribution of an aligner by using the reflectance distribution of the reflection surface of the calibration mask that is stored in a first memory part and the illumination distribution on the sensitive substrate that is measured in the second measuring step, and an updating step to update the reflectance distribution on the reflection surface of the reference plate by using the illuminance distribution that is calculated in the illumination distribution calculation step and is in the aligner and the illuminance distribution on the sensitive substrate that is measured in the first measuring step and uses a light reflected on the reflection surface of the reference plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure apparatus calibration method for manufacturing microdevices such as semiconductor elements and liquid crystal display elements in a lithography process, and an exposure apparatus calibrated by the exposure apparatus calibration method.

In recent years, along with miniaturization of semiconductor element circuits, a projection lithography technique using EUV (Extreme Ultra Violet) light having a short wavelength (11 to 14 nm) has been developed in order to further improve the resolution. In this wavelength range, a transmission / refraction type optical element such as a conventional lens cannot be used, a reflection type optical element such as a mirror is used, and a reflection type mask is also used (for example, see Patent Document 1).
JP 2003-224053 A

  By the way, in an exposure apparatus for manufacturing a semiconductor element or the like, it is necessary to control the illuminance distribution of an exposure region that illuminates a sensitive substrate such as a wafer in order to maintain high exposure accuracy. As a method for detecting the illuminance distribution in the exposure region, in the above-described EUV exposure apparatus, a reference plate having a known reflectance is provided on the mask stage on which the reflective mask is placed, and is reflected by the reflection surface of the reference plate. It is conceivable to measure the illuminance of the EUV light.

  The reflective surface of the reference plate needs to form a multilayer film having a high reflectance with respect to EUV light. However, as the reference plate is used repeatedly, the reflectance of the reflecting surface may change due to adhesion of contamination to the reflecting surface, alteration of the multilayer film, or the like. In addition, the reflectance of the reflecting surface does not necessarily change uniformly within the reflecting surface of the reference plate, and the variation in reflectance on the reflecting surface varies depending on various factors such as EUV light irradiation frequency and illuminance. May occur. Therefore, there is a problem that the illuminance distribution in the exposure area cannot be accurately detected.

  An object of the present invention is to provide an exposure apparatus calibration method capable of accurately detecting an illuminance distribution in an exposure region on a sensitive substrate surface such as a wafer, and an exposure apparatus calibrated by the exposure apparatus calibration method. It is.

  An exposure apparatus calibration method according to the present invention is an exposure apparatus calibration method for transferring a pattern formed on a reflective mask (M) onto a sensitive substrate (W), and is flush with the reflective mask (M). A first measurement step (S10) for measuring the illuminance distribution on the surface of the sensitive substrate (W) using light reflected by the reflection surface of the reference plate (37) installed on the reference plate (37), and a reference reflection surface; A calibration step having a calibration mask is placed on the mask stage (55), and the light reflected by the reflection surface of the calibration mask placed in the placement step (S11) is used. A second measurement step (S12) for measuring the illuminance distribution on the sensitive substrate (W), the reflectance distribution of the reflection surface of the calibration mask stored in the first storage unit (52), and the second measurement. The calibration mask measured in step (S12) Illuminance distribution calculating step (S13) for calculating the illuminance distribution of the exposure apparatus using the illuminance distribution on the sensitive substrate (W) surface using the light reflected by the reflecting surface, and the illuminance distribution calculating step The sensitive substrate (W) using the illuminance distribution of the exposure apparatus calculated in (S13) and the light reflected by the reflecting surface of the reference plate (37) measured in the first measurement step (S10). ) The reflectance distribution calculating step (S14) for calculating the reflectance distribution of the reflecting surface of the reference plate (37) using the illuminance distribution on the surface, and the second memory (52) stored in the second memory unit (52). An updating step (S15) for updating the reflectance distribution of the reflecting surface of the reference plate (37) to the reflectance distribution of the reflecting surface of the reference plate (37) calculated by the reflectance distribution calculating step (S14). It is characterized by that.

  The exposure apparatus of the present invention is an exposure apparatus for transferring a predetermined pattern onto a sensitive substrate (W), and the reflectance of the reflecting surface of the reference plate (37) updated by the calibration method of the exposure apparatus of the present invention. A storage unit (52) for storing the distribution, an illuminance measurement unit (38) for measuring the illuminance distribution on the sensitive substrate (W), and the reference plate (37) stored in the storage unit (52). Calculation for calculating the illuminance distribution of the exposure apparatus using the reflectance distribution of the reflecting surface and the illuminance distribution of the light reflected by the reference plate (37) and irradiating the exposure area on the sensitive substrate (W). Part (51).

  According to the calibration method of the exposure apparatus of the present invention, it is possible to grasp the change in the reflectance of the reflection surface of the reference plate over time using the calibration mask, and therefore the illuminance distribution of the exposure apparatus using the reference plate Can be accurately detected. In addition, since the number of times of replacement with a new reference plate can be reduced, the replacement cost can be reduced.

  In addition, according to the exposure apparatus of the present invention, the exposure apparatus includes the storage unit that stores the reflectance distribution of the reflection surface of the reference plate updated by the calibration method of the exposure apparatus of the present invention. It is possible to accurately detect the illuminance distribution possessed by and to perform good exposure.

  An exposure apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to the embodiment. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W as the sensitive substrate, and the Z axis is set in a direction orthogonal to the wafer W. In this embodiment, an example using a scanning type exposure apparatus that performs exposure while moving the mask and wafer synchronously at a speed substantially corresponding to the reduction magnification will be described. This direction of synchronous movement is called the scanning direction and is set in the Y direction.

  The EUV light 32 emitted from the EUV light source 31 constitutes an illumination optical system 33, becomes a substantially parallel light beam via a concave reflecting mirror 34 that acts as a collimator mirror, and enters the optical integrator 35. The optical integrator 35 includes an incident side fly-eye mirror 35a and an emission side fly-eye mirror 35b. The incident-side fly-eye mirror 35a is composed of a large number of element mirrors arranged in parallel and having an arcuate shape, and its incident surface is at a position optically conjugate with or near the mask M and wafer W surface described later. Has been placed. The EUV light incident on the incident-side fly's eye mirror 35a is divided in wavefront by each element mirror of the incident-side fly's eye mirror 35a.

  The EUV light incident on the incident-side fly-eye mirror 35a is reflected by the incident-side fly-eye mirror 35a and enters the emission-side fly-eye mirror 35b. The exit-side fly-eye mirror 35b is composed of a number of element mirrors arranged in parallel and having a rectangular shape, and its exit surface is at or near a position optically conjugate with the pupil position of the projection optical system PL described later. Is arranged. The EUV light reflected by each element mirror of the incident side fly-eye mirror 35a is incident on each element mirror of the emission side fly-eye mirror 35b. Therefore, on the exit side of the exit side fly-eye mirror 35b or in the vicinity thereof, a large number of condensing points corresponding to the number of element mirrors constituting the exit side fly-eye mirror 35b are formed, and a secondary light source is formed.

  The EUV light reflected by the exit-side fly-eye mirror 35b is deflected by the plane reflecting mirror 36, passes through the elongated arc-shaped field-of-view restriction slit S of the exposure area defining member 1, and has an arc shape on the reflective mask M. An illumination area is formed.

  FIG. 2 is a view showing the configuration of the exposure area defining member 1. The exposure area defining member 1 is disposed between the mask M and the projection optical system PL, and has an arcuate visual field limiting slit S that defines the exposure area on the wafer W. By passing the EUV light through the arc-shaped field-limiting slit S, the surrounding EUV light is shielded, and the exposure area on the wafer W becomes an arc shape that is substantially similar to the field-limiting slit S. Since the exposure area by the EUV light guided onto the wafer W only needs to be defined in a predetermined shape, the EUV light is limited by the field limiting slit S before the EUV light is reflected by the mask M. Alternatively, the EUV light may be limited by the field limiting slit S after the EUV light is reflected by the mask M. In addition, although the exposure area | region concerning this embodiment is prescribed | regulated by circular arc shape, you may make it have another shape.

  Further, as shown in FIG. 2, the exposure region defining member (adjustment unit) 1 is configured by arranging a plurality of members 1a and 1b in a comb shape. An actuator 2 is connected to each member 1a, and each member 1a is configured to be individually movable in the Y direction. Each member 1a is individually moved in the Y direction by the actuator 2 based on the drive signal output from the movement control device 51, for example, as shown in FIG.

  In this way, the exposure amount distribution can be changed by moving each member 1a and changing the shape of the field limiting slit S, that is, the width of the predetermined position in the scanning direction. Therefore, when an illuminance distribution occurs in the exposure region on the wafer W during exposure, the illuminance distribution is corrected by appropriately changing the width of a predetermined position in the scanning direction of the field-limiting slit S, and the exposure amount The distribution can be corrected.

  The mask stage 55 on which the mask M is placed is configured to be largely movable in the Y direction (scanning direction). The mask stage 55 is configured to be movable in a minute amount in the X direction, and is configured to be movable in the Z direction and the rotational directions around the X, Y, and Z axes. The mask stage 55 is provided with a reference plate 37 having a known reflectance distribution for detecting the illuminance distribution of EUV light that irradiates the exposure area on the wafer W. The reflection surface of the reference plate 37 is composed of a multilayer film having a high reflectance with respect to EUV light. The reflectance distribution of the reflecting surface of the reference plate 37 is input in advance from an input unit (not shown) or the like and stored in the storage unit 52. In this example, the reflectance distribution of the reference plate 37 is measured in advance, but this is not always necessary, and may be measured during calibration using the reflectance distribution of a calibration mask described later.

  The EUV light reflected by the mask M forms an image of the pattern of the mask M on the wafer W via the projection optical system PL composed of a plurality of reflecting mirrors (six exemplary reflecting mirrors M1 to M6 in FIG. 1). The pattern of the mask M is formed and transferred onto the wafer W. The wafer W is mounted on the wafer stage 56, and the wafer stage 56 is configured to be movable in the X, Y, and Z axial directions and the rotational directions around the respective axes.

  The wafer stage 56 is provided with an illuminance sensor (illuminance measurement unit) 38 that detects the illuminance distribution of EUV light that is reflected by the reference plate 37 and irradiates the exposure area on the wafer W. When the illuminance sensor 38 is arranged on the same plane as the wafer surface, the illuminance distribution on the wafer surface can be measured. The illuminance sensor 38 is reflected by the illumination area I (see FIG. 4) in the reflection surface R of the reference plate 37 illuminated by EUV light via the illumination optical system 33, and is formed by EUV light via the projection optical system PL. The illuminance in the exposure area A (see FIG. 5) on the wafer W to be measured is measured. Specifically, the wafer stage 56 on which the illuminance sensor 38 is mounted is moved two-dimensionally in the X and Y directions, and the illuminance at each measurement point in the X and Y directions within the exposure region is measured. The detection result by the illuminance sensor 38 is output to the control device 51.

  In this embodiment, one illuminance sensor 38 is provided, but two or more illuminance sensors may be provided. For example, a plurality of illuminance sensors may be arranged in a line in the X direction, and the illuminance at each measurement point in the exposure area on the wafer W may be measured while moving the wafer stage 56 in the Y direction. A plurality of them may be arranged two-dimensionally. Although the illuminance sensor 38 is fixed on the wafer stage 56, the illuminance sensor 38 may be disposed so as to be movable relative to the wafer stage 56. Alternatively, the illuminance sensor 38 may be disposed on a separate stage independent of the wafer stage 56. It is also possible to adopt a configuration in which this stage is moved in the X and Y directions.

  The positions of the mask stage 55 and the wafer stage 56 in the X and Y directions are measured by interferometers (not shown). The measurement result by the interferometer is output to the control device 51, and the control device 51 outputs drive signals 57 and 58 to the mask stage 55 and the wafer swage 56. Based on drive signals 57 and 58 from the control device 51, the mask stage 55 and the wafer stage 56 are moved by an actuator (not shown) such as a linear motor or an air actuator.

First, a method for detecting an illuminance distribution generated in an exposure area on the wafer W and correcting illuminance distribution unevenness during scanning exposure will be described. The control device 51 moves the mask stage 55 to a position where the EUV light that has passed through the field-of-view restriction slit S illuminates the reference plate 37, and at the same time, the illuminance sensor 38 is reflected by the reference plate 37 and passes through the projection optical system PL. The wafer stage 56 is moved so that the illuminance at the measurement point C ₁₁ (see FIG. 5) in the exposure area A formed by light can be detected. The control device 51 acquires the illuminance at the measurement point C ₁₁ detected by the illuminance sensor 38. While moving the wafer stage 56 stepwise in the −Y direction, the illuminance at the measurement points C ₂₁ , C ₃₁ ,... C _n1 detected by the illuminance sensor 38 shown in FIG.

Next, the control device 51 steps the wafer stage 56 in the + X direction to acquire the illuminance at the measurement point C _n2 detected by the illuminance sensor 38, and the illuminance while moving the wafer stage 56 stepwise in the + Y direction. measurement points shown in FIG. 5 which is sequentially detected by the sensor _{38 C (n-1) 2} , to obtain the illuminance at ··· C _22, C _12. Similarly, while moving the wafer stage 56 stepwise in the X and Y directions, the illuminance at the measurement points sequentially detected by the illuminance sensor 38 is acquired, and the illuminance in the exposure area A is acquired. In this example, n measurement points are selected in the Y direction and m measurement points are selected in the X direction. However, the number of measurement points can be arbitrarily determined in consideration of the accuracy required for illuminance distribution correction. Good. The measurement points C _{11 to} C _nm on the wafer surface correspond to the measurement points D _{11 to} D _nm (see FIG. 4) on the reference plate 37. Each reflectance at the measurement point D ₁₁ to D _nm represents the RA ₁₁ to RA _nm, the measurement light intensity at each measurement point C ₁₁ -C _nm represents the IMA ₁₁ ~IMA _nm, the measurement point C ₁₁ -C _The measurement light intensity (illuminance possessed by the exposure apparatus) to be measured when the reflectance of the reference plate is 100% in _nm is I _{11 to} I _nm . (Note that n and m are integers) Then, the measurement light intensity at each measurement point is expressed by the following equation.

IMA _ij = I _ij × RA _ij (i = 1 to n, j = 1 to m, n and m are integers)
Reflectance RA ₁₁ to RA _nm of each measurement point _D 11 _{to D nm} are as described above, are measured in advance, because it is stored in the storage unit 52, the exposure from the measured intensity IMA ₁₁ ~IMA _nm of each measurement point devices The illuminance I _{11 to} I _nm of the can be obtained.

Next, the control device 51 obtains an integrated value of the illuminance I _nm of the exposure apparatus at the measurement point having the same Y coordinate, and calculates an illuminance distribution in the X direction by performing scanning exposure from each integrated value.

The control device 51 calculates the movement amount of each member 1a of the exposure region defining member 1 for correcting the calculated illuminance distribution, and moves the members 1a based on the calculation result to thereby change the shape of the field limiting slit S. change. For example, the width of the visual field limiting slit S in the scanning direction is expanded by moving the member 1a arranged at a position where the illuminance needs to be increased. Moreover, the width | variety in the scanning direction of the visual field restriction | limiting slit S is narrowed by moving the member 1a arrange | positioned in the position which needs to reduce illumination intensity. In the above description, after _obtaining the absolute illuminance value I _nm , the illuminance in each scanning direction is integrated, and the movement amount of each member of the exposure region defining member 1 so that the exposure amount is uniform in the X direction. Have decided. However, in order to correct the exposure amount so as to be uniform along the X direction, it is sufficient to obtain the relative X direction distribution of the integrated illuminance. Therefore, the reflectance _RA 11 _{to RA nm} of each measurement point _D 11 _{to D nm} is even without absolute value, relative reflectance distribution (i.e. the difference in reflectance between the respective measurement points) is sufficient Knowing Become. Therefore, the reflectance of the reference plate 37 stored in the storage unit 52 may be an absolute value or a relative value. In this embodiment, in order to correct illumination unevenness, the slit width in the scanning direction is adjusted as shown in FIG. 3, for example, but the integrated illuminance in the scanning direction is in a direction orthogonal to the scanning direction. Other methods may be used as long as they are constant. For example, in addition to the method of changing the slit width, various methods such as inserting a structure in the slit or introducing a device for changing the transmittance distribution in the exposure region can be used.

  By the way, in the exposure apparatus, in order to maintain high exposure accuracy, the above-described correction of the illuminance distribution is frequently performed, for example, every time the exposure apparatus is started up or every time the mask is replaced. That is, the frequency of use of the reference plate 37 is very high, and as the reference plate 37 is used repeatedly, the multilayer film constituting the reflection surface of the reference plate 37 changes in quality, or contamination adheres to the reflection surface. As a result, the reflectance of the reflecting surface of the reference plate 37 changes. This reflectance does not always change uniformly over the entire reflecting surface, and unevenness occurs in the change in reflectance on the reflecting surface according to the irradiation frequency and illuminance of EUV light. Therefore, it has a reflectance distribution different from the reflectance distribution of the reflecting surface of the reference plate 37 stored in advance in the storage unit 52, and the illuminance distribution in the exposure area on the wafer W cannot be accurately detected. .

  In this embodiment, the exposure apparatus can be calibrated by updating the reflectance distribution of the reflecting surface of the reference plate 37. FIG. 6 is a flowchart showing a calibration method of the exposure apparatus according to this embodiment.

First, step S10 which is the first illuminance distribution measurement is performed. Since this is the same as the measurement of the measurement points D _{11 to} D _nm of the reference plate 37 described above, description thereof is omitted.

  Next, when the mask M is placed on the mask stage 55, the control device 51 retracts the mask M and places the calibration mask on the mask stage 55 where the mask M is placed. (Step S11, placement process). Note that the processing in step S11 may be performed before the processing in step S10. FIG. 4 shows a state in which the calibration mask M2 is placed on the mask stage 55. FIG. The calibration mask M2 has a reflective surface having a known reflectance distribution as a reference. The reflectance distribution on the reflecting surface of the calibration mask M2 is measured by another measuring device (not shown), input in advance by an input unit (not shown), and stored in the storage unit 52. In the present embodiment, the medium for storing the reflectance distribution of the calibration mask M2 and the reflectance distribution of the reference plate 37 is described as the same medium. Then, it may be stored in a storage medium installed at a different location from the exposure apparatus. Further, it is not always necessary that the storage medium is always connected to the exposure apparatus, and it may be configured such that it is connected manually or automatically by the operator when necessary.

Next, the process of step S12 that is the second illuminance distribution measurement will be described. The control device 51 moves the mask stage 55 to a position where the illumination area I indicated by the broken line illuminates the measurement points F _{11 to} F _nm (see FIG. 4). Then, in the same manner as the illuminance distribution measurement using the reference plate 37 described above, the illuminance at the measurement points C _{11 to} C _nm (see FIG. 5) on the wafer W surface corresponding to the measurement points F _{11 to} F _nm is measured. Thus, the illuminance distribution of the calibration mask M2 is measured. At this time, the relative positions of the measurement points D _{11 to} D _nm with respect to the illumination area I (area indicated by the solid line in FIG. 4) and the measurement points F ₁₁ to F relative to the illumination area I (area indicated by the broken line in FIG. 4). Position so that the relative positions of _nm are the same. This is to prevent the illuminance (for example, I ₁₁ ) from changing at the measurement points (for example, D ₁₁ and F ₁₁ ) to be compared as will be described later.

Next, the control device 51 considers the reflectance distribution of the reflection surface of the calibration mask M2 stored in advance in the storage unit 52 from the illuminance distribution based on the calibration mask M2 measured in step S12, and performs illumination. The illuminance distribution in the Y direction of the optical system 33 and the projection optical system PL is calculated (step S13, illuminance distribution calculating step). Specifically, the reflectance of each measurement point _F 11 _{to F nm} of the calibration mask M2 and _RB 11 _{~RB nm,} the measured illuminance and _IMB 11 _{~IMB nm,} illuminance of obtaining the _I 11 _{~I nm} Then, each value has the following relationship.

IMB _ij = I _ij × RB _ij (i = 1 to n, j = 1 to m, n and m are integers)
From this relationship, the illuminance distributions I _{11 to} I _nm of the exposure apparatus can be obtained. Next, the control device 51 considers the illuminance distribution in the Y direction of the illumination optical system 33 and the projection optical system PL calculated in step S13 from the illuminance distribution based on the reference plate 37 measured in step S10. The reflectance distribution of the reflecting surface of the reference plate 37 is calculated (step S14, reflectance distribution calculating step). Specifically, the above-mentioned IMA _ij = I _ij × RA _ij (i = 1 to n, j = 1 to m, n and m are integers)
The true RA _ij value is calculated using the measured IMA _ij and the I _ij value calculated in step S13.

As described above, the reflectance value does not need to be an absolute value, and it is only necessary to know the difference in reflectance at each measurement point. Therefore, the reflectance _RA 11 _{to RA nm} reflectance _RB 11 _{~RB nm} also reference plate 37 of the calibration mask M2 is also for example, be a reflectance normalized, relative to the reflection factor of one of the measuring points What is necessary is just to memorize | store as a reflectance.

  Next, the control device 51 updates the reflectance distribution of the reflecting surface of the reference plate 37 stored in the storage unit 52 to the reflectance distribution of the reflecting surface of the reference plate 37 calculated in Step S14 (Step S15). , Renewal process). The calibration of the exposure apparatus according to the above-described embodiment may be performed every predetermined number of times of use of the reference plate 37, for example, at a rate of once for every 100 uses of the reference plate 37, or for a predetermined period. For example, it may be performed once a week. In addition, when updating the reflectance distribution of the reflecting surface of the reference plate 37, it is not necessary to compare the old reflectance distribution with the reflectance distribution to be updated. Therefore, the old reflectance distribution data is added before the sequence shown in FIG. It may be deleted from the storage unit 52 and only the work of writing the newly obtained reflectance distribution in the storage unit 52 may be performed in step S15. In the present invention, such a case is also called update of the reflectance distribution. Furthermore, as described above, in this embodiment, the reflectance distribution of the reference plate 37 is measured by another device and the reflectance distribution data is input from the external input device. Good. This is because the reflectance distribution of the reference plate 37 can be calculated by performing the sequence shown in FIG. 6, and the calculated reflectance distribution data may be stored in the storage unit 52 and used. It doesn't matter.

  The illuminance distribution unevenness described above is corrected using the reflectance distribution updated in this way. That is, the control device 51 is reflected by the reflecting surface of the reference plate 37 every time the exposure apparatus is started or the mask is replaced, for example, in an exposure region formed by EUV light that illuminates the wafer W. From the illuminance distribution, the illuminance distribution of the illumination optical system 33 and the projection optical system PL is acquired in consideration of the reflectance distribution updated in step S15. Then, the movement amount of each member 1a of the exposure area defining member 1 is calculated from the acquired illuminance distribution, and the shape of the field-limiting slit S is changed by moving each member 1a based on the calculation result, and the illuminance in the Y direction Correct the distribution.

  According to the exposure apparatus calibration method of this embodiment, since the change in the reflectance of the reflective surface of the reference plate 37 over time can be grasped using the calibration mask M2, the reference plate 37 is used. The illuminance distribution of the exposure apparatus (illumination optical system 33 and projection optical system PL) can be accurately detected. In addition, since the number of times of replacement with a new reference plate can be reduced, the replacement cost can be reduced.

  Further, according to the exposure apparatus of this embodiment, the updated reflectance distribution of the reflecting surface of the reference plate 37 and the illuminance distribution of the light that is reflected by the reference plate 37 and irradiates the exposure area on the wafer W. By using this, the illuminance distribution of the exposure apparatus can be detected accurately, and good exposure can be performed.

  In the exposure apparatus according to the above-described embodiment, the mask stage 55 is configured to be largely movable only in the Y direction (scanning direction). That is, the mask stage 55 can only finely move in the X direction (non-scanning direction). In the embodiment described above, the illuminance sensor is fixed in a state where the masking stage 55 is fixed so that the reflection surface R of the reference plate 37 or the reflection surface R2 of the calibration mask M2 exists with respect to the entire illumination area I. Each measurement point was measured by moving the wafer stage 56. However, the mask stage 55 can be stepped in the Y direction during measurement. The advantage in this case is that the width in the Y direction of the reflecting surface R of the reference reflector can be reduced, and the same location on the reflecting surface R can be used for measurement in the Y direction. It is possible to correct the illuminance distribution unevenness without considering the reflectance distribution in the Y direction.

  Further, if the mask stage 55 can be moved greatly in the X and Y directions, the reference plate 37 can be further reduced, and if one point of the reference plate 37 is used for measurement, the reflection region of that point can be reduced. Only the change over time may be measured.

  Further, the reference plate 37 and the calibration mask M2 do not necessarily have to be fixed to the same mask stage 55, and if the reference plate 37 can be arranged on the same surface as the mask surface, the reference plate 37 is referred to as the mask stage 55. You may arrange | position and move on a different stage.

  In this embodiment, the calibration mask in which the reflectance distribution measured by a measuring device (not shown) is stored in the storage unit 52 is used. However, the calibration mask whose reflectance distribution is unknown is used. The reflectance distribution may be calculated based on the illuminance measured by the exposure apparatus according to this embodiment. That is, first, the calibration mask M2 shown in FIG. Then, the illuminance at the respective measurement points in the exposure area formed by the EUV light reflected by the reflection surface R2 of the calibration mask M2 by the illuminance sensor 38 is moved stepwise in the Y direction and the illuminance sensor 38 is moved. Are sequentially measured while stepping the wafer stage 56 to which X is fixed in the X and Y directions.

  Next, the calibration mask M2 is removed from the mask stage 55 once and rotated 90 degrees, and then placed on the mask stage 55 again. Then, the illuminance sensor 38 stepwise moves the mask stage 55 in the Y direction for the illuminance at each measurement point in the exposure region formed by the EUV light reflected by the reflecting surface R2 of the calibration mask M2 shown in FIG. Further, the wafer stage 56 is sequentially measured while being moved stepwise in the X and Y directions.

  Next, the reflectance distribution at each measurement point on the reflection surface of the calibration mask M2 is obtained from the illuminance at each measurement point measured before the rotation and the illuminance at each measurement point measured after the rotation. That is, in the measurement before the 90-degree rotation, by measuring different positions in the Y direction of the calibration mask M2 at the same measurement position in the illumination area, the reflectance distribution in the Y direction of the reflection surface of the calibration mask M2 is obtained. Although it can be obtained, the distribution of the reflectance in the X direction of the reflecting surface cannot be obtained only by this measurement. Therefore, by rotating the calibration mask M2 by 90 degrees and obtaining the Y-direction reflectance distribution again, the relationship of the reflectance distribution at each Y coordinate obtained in the measurement before the 90-degree rotation can be obtained. The reflectance distribution in the X direction and the Y direction of the calibration mask M2 can be obtained.

  In this embodiment, the exposure area defining member 1 shown in FIG. 2 is provided. However, instead of the exposure area defining member 1, an exposure area defining member 1 ′ shown in FIG. The exposure region defining member 1 ′ shown in FIG. 8 is configured by combining two members 1c and 1d, for example, and the scanning direction (X direction) of the field limiting slit S is changed by changing the combination position of the members 1c and 1d. ) Can be changed. FIG. 9 is a diagram illustrating an example in which the combination position of the members 1c and 1d is changed. As shown in FIG. 9, for example, when the member 1c is moved by a predetermined amount in the −X direction, the width W2 can be made larger than the width W1 in the scanning direction of the visual field limiting slit S. In this way, by changing the width of the field limiting slit S in the scanning direction, an inclination component can be given to the exposure amount by the exposure light passing through the field limiting slit S. ) Occurs, the exposure amount distribution can be corrected by appropriately changing the width of the visual field limiting slit S in the scanning direction.

  In this embodiment, the storage unit 52 stores the reflectance distribution of the reflection surface of the reference plate 37 and the reflectance distribution of the reflection surface of the calibration mask. However, the storage unit 52 includes two storage units, The storage unit may store the reflectance distribution of the reflection surface of the reference plate 37, and the other storage unit may store the reflectance distribution of the reflection surface of the calibration mask.

  In this embodiment, the illuminance distribution is corrected by changing the shape of the field limiting slit S. However, the angles and orientations of the reflecting surfaces of some of the element mirrors constituting the optical integrator 35 are adjusted. The illuminance distribution may be corrected by changing.

  Also, the illuminance sensor can be a single sensor, or can be configured to measure the illuminance at a plurality of measurement points at once by arranging a large number of sensors in a one-dimensional direction or a two-dimensional direction.

  Further, although the reference plate 37 is configured to be placed on the mask stage 55, the reference plate 37 can be arranged on another stage different from the mask stage 55.

It is a figure which shows schematic structure of the exposure apparatus concerning Embodiment. It is a figure which shows the structure of an exposure area prescription | regulation member. It is a figure which shows the structure of an exposure area prescription | regulation member. It is a figure which shows the positional relationship of the reference | standard reflecting plate mounted in the mask stage, and the calibration mask. It is a figure which shows a part of each measurement point at the time of an illumination intensity sensor measuring the illumination intensity in an exposure area | region. It is a flowchart for demonstrating the calibration method of the exposure apparatus concerning Embodiment. It is a figure which shows the positional relationship of a mask for calibration and an illumination area. It is a figure which shows the other structure of an exposure area prescription | regulation member. It is a figure which shows the other structure of an exposure area prescription | regulation member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exposure area | region definition member, 31 ... Light source, 33 ... Illumination optical system, 35 ... Optical integrator, 35a ... Incident side fly eye mirror, 35b ... Emission side fly eye mirror, 37 ... Reference | standard board, 38 ... Illuminance sensor, 51 ... Control device 52... Storage unit 55... Mask stage 56. Wafer stage S S field-limiting slit M mask M2 calibration mask PL projection optical system W wafer

Claims (5)

An exposure apparatus calibration method for transferring a pattern formed on a reflective mask onto a sensitive substrate,
A first measurement step of measuring an illuminance distribution on the sensitive substrate surface using light reflected by a reflective surface of a reference plate installed on the same plane as the reflective mask;
A placing step of placing a calibration mask having a reference reflecting surface on a mask stage;
A second measurement step of measuring an illuminance distribution on the sensitive substrate surface using the light reflected by the reflection surface of the calibration mask placed by the placement step;
On the sensitive substrate surface using the reflectance distribution of the reflection surface of the calibration mask stored in the first storage unit and the light reflected by the reflection surface of the calibration mask measured in the second measurement step. The illuminance distribution calculating step of calculating the illuminance distribution of the exposure apparatus using the illuminance distribution of
The illuminance distribution of the exposure apparatus calculated by the illuminance distribution calculation step, and the illuminance distribution on the sensitive substrate surface using light reflected by the reflection surface of the reference plate measured by the first measurement step A reflectance distribution calculating step for calculating a reflectance distribution of the reflecting surface of the reference plate,
An update step of updating the reflectance distribution of the reflecting surface of the reference plate stored in the second storage unit to the reflectance distribution of the reflecting surface of the reference plate calculated by the reflectance distribution calculating step;
A calibration method for an exposure apparatus.   The first measurement step and the second measurement step are performed so that the illuminance distribution of the exposure apparatus is the same between the measurement point measured in the first measurement step and the measurement point measured in the second measurement step. The exposure apparatus calibration method according to claim 1, wherein the exposure apparatus calibration is performed.   The exposure using the reflectance distribution of the reflecting surface of the reference plate updated by the updating step and the illuminance distribution of light that is reflected by the reflecting surface of the reference plate and irradiates the exposure area on the sensitive substrate surface. 3. The exposure apparatus calibration method according to claim 1, wherein an illuminance distribution of the apparatus is calculated.   The reflectance distribution of the reflection surface of the calibration mask stored in the first storage unit is the illuminance distribution on the sensitive substrate using light reflected by the reflection surface of the calibration mask using the exposure apparatus. After the measurement, the calibration mask is rotated 90 degrees with respect to the mask stage, and the illuminance distribution on the sensitive substrate is measured again using the light reflected by the reflection surface of the calibration mask. 4. The exposure apparatus calibration method according to claim 1, wherein the exposure apparatus is calculated using the illuminance distribution before the rotation and the illuminance distribution after the rotation. In an exposure apparatus that transfers a predetermined pattern onto a sensitive substrate,
A storage unit that stores the reflectance distribution of the reflecting surface of the reference plate updated by the exposure apparatus calibration method according to any one of claims 1 to 4.
An illuminance measuring unit for measuring an illuminance distribution on the sensitive substrate;
The exposure apparatus has a reflectance distribution of the reflecting surface of the reference plate stored in the storage unit and an illuminance distribution of light that is reflected by the reference plate and irradiates an exposure area on the sensitive substrate. A calculation unit for calculating an illuminance distribution;
An adjustment unit that adjusts the illuminance distribution of the exposure apparatus calculated by the calculation unit;
An exposure apparatus comprising:

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