JP6532332B2 - EXPOSURE APPARATUS AND EXPOSURE METHOD, AND ARTICLE MANUFACTURING METHOD - Google Patents

Description

  The present invention relates to an exposure apparatus and an exposure method, and a method of manufacturing an article.

  The exposure apparatus is a lithography process included in a manufacturing process of a semiconductor device, a liquid crystal display device, etc., in which a pattern of an original (a reticle or a mask) is exposed via a projection optical system to a photosensitive substrate (a resist layer is formed on the surface It is an apparatus which transfers to a wafer, a glass plate, etc.). In order to transfer the pattern of the original to the substrate with high accuracy, it is necessary to maintain the imaging performance of the projection optical system. However, if exposure light continues to pass through the projection optical system while continuous exposure is being performed, the temperature in the projection optical system changes, and its imaging performance changes. Therefore, Patent Document 1 discloses an exposure apparatus that keeps the temperature in the projection optical system constant by controlling the temperature of the outer surface of the lens barrel of the projection optical system.

JP 2005-203522 A

  In the exposure apparatus of Patent Document 1, the temperature control of the outer surface of the lens barrel is performed based on the amount of change in the imaging performance of the projection optical system calculated based on the pressure and temperature distribution around the projection optical system. We are trying to maintain the performance. However, if the accuracy of this calculation result is insufficient, it may be difficult to maintain sufficient imaging performance. A general method of measuring the amount of change in imaging performance can not grasp the amount of change during exposure.

  An object of the present invention is, for example, to provide an exposure apparatus that is advantageous for maintaining the imaging performance of a projection optical system.

An exposure apparatus of one embodiment of the present invention is an exposure apparatus having a projection optical system for projecting a pattern of an original onto a substrate, comprising a measuring system for evaluating the imaging performance of the projection projection optical system, the measuring system, A reference plate provided with a first mark and a second mark, a first light source for emitting a first light beam passing through the reference plate and the projection optical system, and a second light beam passing through a second mark a second light source, is provided between the original and the light projecting projection optical system, passes through a reflecting section for reflecting the first light beam, a first mark and the projection optical system in the order, it is reflected by the reflective portion The image pickup device picks up an image of the first mark by receiving the first light beam that has passed through the projection optical system again, and the image pickup device picks up an image of the second mark by receiving the second light beam. Calculate the relative position of the first mark and the second mark Characterized in that it comprises an evaluation unit for evaluating on the basis of the results.

  According to the present invention, it is possible to provide an exposure apparatus that is advantageous for maintaining the imaging performance of a projection optical system.

FIG. 1 is a view showing the arrangement of an exposure apparatus according to the first embodiment of the present invention. It is a figure which shows the positional relationship of an exposure area | region and a measurement system. It is a figure which shows a reference mark. It is a figure which shows the reference mark provided in a reference reflective surface. It is a figure which shows the field stop with respect to the light source of the light beam which does not pass a projection optical system. It is a figure which shows the field stop with respect to the light source of the light beam which passes a projection optical system. It is a figure showing a fiducial mark picturized by an image sensor. It is a figure which shows the structure of the exposure apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the intensity | strength on the imaging surface of the reference mark which concerns on 2nd Embodiment. It is the graph which plotted the intensity | strength of each mark which concerns on 2nd Embodiment. It is a figure which shows the structure of the exposure apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows an exposure apparatus when a measurement system is driven in the exposure area | region.

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

First Embodiment
FIG. 1 is a view showing an example of the arrangement of an exposure apparatus and a measurement system. In the present embodiment, an example of illuminating a mask (original plate) and drawing a pattern on a substrate (plate) will be described, but the present invention is not limited to this. It may be an exposure apparatus that illuminates a reticle (original plate) and draws a substrate (wafer).

  The exposure apparatus according to the present embodiment includes an illumination optical system 40, a mask stage 10, a projection optical system 30, a substrate 21, a plate stage 20, a control unit 601, and a measurement system (first measurement system 50, second measurement system 80). Have. The illumination optical system 40 uniformly irradiates the mask 11 with a desired angular distribution with exposure light. In the mask 11, a pattern to be projected on the plate 21 is drawn. The mask stage 10 holds the mask 11 and can be driven in the Y direction. The mask stage 10 may be driven in the X direction or in the θ direction (rotational direction around the X axis, rotational direction around the Y axis, and rotation around the Z axis).

  The projection optical system 30 forms an image of the pattern of the mask 11 illuminated by the illumination optical system 40 on the plate 21. The pattern of the mask 11 illuminated by the illumination optical system 40 is drawn on the plate 21. The plate stage 20 holds the plate 21 and can be driven in the X direction, the Y direction, the Z direction, and the θ direction. The measurement system includes a first measurement system 50 and a second measurement system 80. The first measurement system 50 includes a light source 58 and a light source 59, a reference plate 514, a reference reflection surface 532, an evaluation unit 600, and an imaging device 500. The second measurement system has a reference reflecting surface 536 and a bending mirror 535.

  Furthermore, the first measurement system 50 includes an objective lens 51, an imaging system relay lens 52, a reference system relay lens 53, illumination system lenses 54a to 54d, beam splitters 56, 57 and 531, field stops 512 and 513, an objective stop 521 and A wave plate 533 is provided. The measurement system illuminates the measurement mark drawn on the reference plate 514 in the measurement system, and measures an amount of positional deviation in the X direction, the Y direction or the Z direction by imaging.

  For example, the light source 58 and the light source 59 emit luminous fluxes of different wavelengths to illuminate the reference plate 514. The reference reflective surfaces 532 and 536 are disposed at positions conjugate to the plate surface and the mask surface, and the reference reflective surface 536 is provided with measurement marks. The imaging element 500 captures an image of the measurement mark that has passed through the imaging system relay lens 52. The beam splitter 531 separates the light beam passing through the projection optical system 30 and the light beam not passing through it.

  The light beam passing through the projection optical system 30 illuminates and reflects the measurement mark on the reference reflection surface 536, is re-incident on the projection optical system 30, passes through, and forms an image of the measurement mark on the imaging element 500. The evaluation unit 600 calculates the relative position of the image of the captured mark, and evaluates the imaging performance of the projection optical system based on the calculated relative position. The control unit 601 controls the projection optical system so as to maintain the imaging performance of the projection optical system in accordance with the control signal from the evaluation unit 600.

  FIG. 2 is a view showing measurement marks of the reference plate 514. As shown in FIG. A plurality of X-direction measurement marks and Y-direction measurement marks are drawn on the same surface of the reference plate 514 as a second mark 514a and a first mark 514b. In addition, the part shown with a grid is a light-shielding part, and others show a permeation | transmission part. FIG. 3 is a view showing a reference reflective surface 536 configured at a position conjugate to the reference plate 514. As shown in FIG. On the reference reflecting surface 536, a plurality of measurement marks in the X direction and measurement marks in the Y direction are drawn as a third mark 536c. In addition, the part shown with a grating | lattice is a transmission part, and others show a reflection part. The second mark 514 a, the first mark 514 b, and the third mark 536 c are configured so as not to overlap when forming an image on the imaging device 500.

  FIG. 4 and FIG. 5 are diagrams showing an example of the field stop according to the present embodiment. Field stops 512 and 513 are configured in a conjugate position with reference plate 514. The field stop 512 is shaped to illuminate the second mark 514a. On the other hand, the field stop 513 is shaped to illuminate the first mark 514 b and the third mark 536 c. Thereby, the second mark 514 a is illuminated by the light source 58, and the first mark 514 b and the third mark 536 c are illuminated by the light source 59.

  The light source 58 and the light source 59 emit light fluxes of different wavelength bands to illuminate the reference plate 514. The beam splitter 531 transmits the wavelength band of the light beam emitted from the light source 58, but has the characteristics of the polarization beam splitter for the wavelength band of the light beam emitted from the light source 59. Specifically, the light flux emitted from the light source 58 passes through the beam splitter 531, passes through the wavelength plate 533 and the reference reflecting surface 532, passes through the beam splitter 531 again, and is imaged by the imaging device 500.

  On the other hand, the light beam emitted from the light source 59 passes through the beam splitter 531, passes through the wavelength plate 533 and the reference reflecting surface 532 in order, is reflected by the beam splitter 531, and passes through the projection optical system 30 as a reference. The reflective surface 536 is reached. The luminous flux reaching the substrate reflection surface 536 illuminates the measurement mark on the substrate reflection surface 536, is reflected, and returns to the beam splitter 531 through the projection optical system 30 again.

  The light beam returned to the beam splitter 531 passes through the beam splitter 531 again via the wavelength plate 533 and the reference reflection surface 532 in this order, and is imaged by the imaging device 500. That is, the light flux not passing through the projection optical system 30 and the light flux passing through the projection optical system 30 are received by the imaging device 500. The wave plate 533 is a λ / 4 plate.

  Next, measurement of the mark imaged by the imaging element 500 will be described. FIG. 6 is a view showing a measurement mark captured by the image sensor 500. As shown in FIG. The second mark 514a, the first mark 514b and the third mark 536c correspond to the mark images 500a, 500b and 500c, respectively. That is, the mark image 500a is a mark which has not passed through the projection optical system 30, the mark image 500b is a mark which has passed (reciprocated) twice through the projection optical system 30, and the mark image 500c is a projection optical system It is a mark that has passed 30 times.

  In the correction of the imaging performance of the projection optical system 30, the evaluation unit measures the measurement values of the measurement marks in the X direction and the measurement marks in the Y direction of the second mark 514a, the first mark 514b, and the third mark 536c. The amount of change is calculated from the difference, and the imaging performance is evaluated based on the calculation result. The control unit 601 adjusts the magnification, distortion, telecentricity, and the like based on the amount of change sent from the evaluation unit 600. The change amount of the mark measurement value of the marks 500a and 500b indicates the telecentric deviation amount of the projection optical system 30 (the amount of inclination of the chief ray not to be parallel to the optical axis but to the optical axis).

  On the other hand, the amount of change of the mark measurement value of the marks 500 b and 500 c indicates the amount of change (shift) in the X direction and the Y direction of the projection optical system 30. Since the projection optical system 30 is a telecentric optical system, the position of the mark returns to the original position if the projection optical system 30 reciprocates even if there is a shift. However, when passing through the projection optical system 30 once, the position of the mark does not return to the original position, and appears as a shift amount.

  FIG. 7 is a diagram showing an example in which a plurality of measurement systems 50 are configured. By arranging a plurality of measurement systems 50 around the exposure area 12, the imaging performance of the projection optical system 30 in the exposure area can be grasped more accurately. The evaluation unit calculates the shift amount in the exposure region and the telecentric displacement amount from the measurement results of the plurality of measurement systems 50, and evaluates the imaging performance of the projection optical system 30. The control unit 601 adjusts the magnification, distortion, telecentricity, and the like according to the amount of change (the amount of shift or the amount of shift) sent from the evaluation unit 600.

  In addition, when the reproducibility of the mark measurement value is low, it is expected that a rapid change occurs in the temperature distribution inside the projection optical system. Therefore, the imaging performance is deteriorated by changing the conditions of temperature control and air conditioning. You can prevent. In addition, since the measurement system 50 is independent of the original plate and the substrate, it can be measured even during exposure which is scanning the original plate and the substrate, and magnification, distortion, telecentricity and the like can be adjusted. Thereby, it is possible to prevent the deterioration of the imaging performance without reducing the throughput.

  In addition, since the XY coordinate axis is changed by the routing of the optical system, it is necessary to adjust the measurement value in the X direction, the measurement value in the Y direction, and the sign according to the change. In addition, since the appropriate light source output differs depending on the transmittance of each light path and the reflectance of the light shielding portion, it is necessary to adjust the light source output so as to obtain an optimal light amount for measurement. Further, the reflectances of the reference reflective surfaces 536 and 531 may be adjusted according to the transmittance of the projection optical system 30.

  As described above, according to the present embodiment, the imaging performance of the projection optical system 30 can be accurately grasped by acquiring the relative position change amount of the measurement mark of the reference plate 514. Further, by forming a plurality of measurement systems 50 around the exposure area 12, the imaging performance of the projection optical system 30 can be grasped more accurately. As a result, it is possible to improve the exposure performance without lowering the throughput while adjusting the imaging performance with high accuracy.

Second Embodiment
In the second embodiment, an exposure apparatus capable of measuring the position of the projection optical system 30 in the Z direction will be described. FIG. 8 is a view showing an example of an exposure apparatus using the measurement system 60 in which the reference mark 515 is inclined. The design of the tilted reference mark 515 is the same as the design of the reference plate 514 shown in FIG. When the reference mark 515 is tilted in the direction of rotation about the X axis, the Z position changes depending on the position of the reference mark surface, so that the strength of each mark in the imaging device 500 differs.

  FIG. 9 is a diagram showing each mark and the strength of each mark when the reference mark 515 is inclined. For example, the intensities of the respective marks of the reference mark 514b when the reference mark 515 is inclined in the Y direction are shown by 514B-1 and 514B-2. It is assumed that 514B-1 and 514B-2 have a difference in time of measurement.

  FIG. 10 (A) is a graph in which the intensity of each mark is plotted. Here, calculation of the amount of change in the Z direction of the projection optical system 30 will be described. First of all. From the graph shown in FIG. 10A, the mark position at which the mark intensity is minimum is taken as the Z direction position, and the difference between the mark intensities 514A-1 and 514A-2 is calculated as ΔZa which is the position in the Z direction. Similarly, from the graph shown in FIG. 10B, ΔZb, which is the difference in the Z direction position, is calculated for the reference mark 514b. Since the difference between the second mark 514 a and the first mark 514 b is whether or not the light passes through the projection optical system 30, the difference between the difference in the Z direction between the second mark 514 a and the first mark 514 b (ΔZa−ΔZb) represents the amount of change of the projection optical system 30 in the Z direction.

  In this embodiment, only the amount of change in the Z direction when the reference mark 515 is tilted in the Y direction is calculated. However, by changing the reference mark 515 in the X direction and Y direction, or by using an inclined mask. The amount of change in the Z direction may be calculated, and the ass of the projection optical system 30 may be measured.

  Further, by forming a plurality of measurement systems 60 capable of measuring the Z direction around the exposure area, the imaging performance of the projection optical system 30 in the exposure area can be grasped with higher accuracy. Specifically, from the measurement results of the plurality of measurement systems 60, it is possible to predict the amount of focus, ashes, and image plane in the exposure region. In addition, since the strength of the mark capable of measuring the position in the X and Y directions can be sufficiently obtained by the amount of inclination of the reference mark 515, it is possible to simultaneously measure the position in not only the Z direction but also the X and Y directions. It may be in the form.

  As described above, according to the present embodiment, it is possible to measure the position of the projection optical system 30 in the Z direction. Thereby, the exposure performance can be improved while adjusting the imaging performance with high accuracy also in the Z direction.

Third Embodiment
In the third embodiment, an embodiment capable of directly measuring the imaging performance in the exposure region of the projection optical system 30 will be described. 11 and 12 have a measurement system 70 capable of driving the objective lens 51, the beam splitter 531, the reference reflection surface 532 and the wavelength plate 533 into the exposure region of the projection optical system 30 as compared with the first embodiment. It is a figure which shows an exposure apparatus. In the present embodiment, the objective lens 51, the beam splitter 531, the reference reflecting surface 532 and the wavelength plate 533 are referred to as a light guide. The drive control system 700 (drive unit) drives the light guide to move the measurement area of the measurement system 70 into and out of the exposure area of the projection optical system 30. Thereby, the imaging performance in the exposure area of the projection optical system 30 can be directly measured.

  Specifically, the imaging performance of the projection optical system 30 in the exposure area is directly measured at the time of replacing the original plate or the substrate. Next, the difference with the correction value estimated from the measurement result measured in the first embodiment is confirmed, and is fed back to the correction value. At this time, direct measurement in the exposure region may be performed at a plurality of positions in order to improve the accuracy. For example, two imaging systems 70 may be disposed to straddle the exposure region 12 in the scanning direction, and the imaging performance of the projection optical system 30 may be measured. When the imaging performance in the exposure area is directly measured, the exposure is interrupted.

  Specifically, although the correction values calculated from the two measurement systems 70 across the exposure area 12 are the characteristics of the linear function, as a result of directly measuring the inside of the exposure area, the correction values were the characteristics of the quadratic function. In this case, it is possible to correct the imaging performance with higher accuracy by correcting according to the coefficient of the quadratic function.

  The functions and coefficients for performing the above-described correction differ depending on the mask pattern to be actually exposed and the amount of exposure energy irradiated to the projection optical system 30. As in the first embodiment, in addition to the position measurement in the X direction and the position measurement in the Y direction, the embodiment may be combined with a mode capable of position measurement in the Z direction shown in the second embodiment. Also, the measurement meter 70 may be driven into the exposure region.

  According to the present embodiment, by directly measuring the imaging performance in the exposure region and reflecting it on the correction, it is possible to grasp the imaging performance of the projection optical system 30 more accurately. As a result, it is possible to improve the exposure performance without lowering the throughput while adjusting the imaging performance with high accuracy.

(Product manufacturing method)
The method for producing an article according to the embodiment of the present invention is suitable, for example, for producing an article such as a microdevice such as a semiconductor device or a liquid crystal display device or an element having a fine structure. The manufacturing method comprises the steps of: forming a latent image pattern on the photosensitizer on a substrate (plate, wafer, etc.) coated with the photosensitizer using the exposure apparatus described above (step of drawing on the substrate); Developing the substrate on which the latent image pattern has been formed. Furthermore, the manufacturing method may include other known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist peeling, dicing, bonding, packaging, etc.). The method of manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of an article, as compared to the conventional method.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the present invention.

10 mask stage 11 mask 12 exposure area 20 plate stage 21 plate 30 projection optical system 40 illumination optical system 50 first measurement system 80 second measurement system

Claims (9)

An exposure apparatus having a projection optical system for projecting an original pattern onto a substrate ,
Comprising a measuring system for evaluating the imaging performance of the previous SL projection optical system,
The measurement system is
A reference plate provided with a first mark and a second mark;
A first light source for emitting a first light beam passing through the reference plate and the projection optical system;
A second light source for emitting a second light beam passing through the second mark;
A reflecting unit provided between the original and the projection optical system and reflecting the first light flux;
After passing through the first mark and the projection optical system in order, the first light flux is reflected again by the reflection section to receive the first light flux that has passed through the projection optical system again to pick up the first mark. An image pickup element for picking up an image of the second mark by receiving the second light flux;
An evaluation unit that calculates a relative position between the first mark and the second mark, which is imaged by the imaging element, and performs the evaluation based on a calculation result. The reflective portion is provided with a third mark,
The image pickup element picks up an image of the third mark by receiving the first light flux which has sequentially passed through the third mark and the projection optical system.
The evaluation unit calculates the relative position of the first mark and the third mark, which is imaged by the imaging device, and the calculation result of the relative position of the first mark and the third mark. The exposure apparatus according to claim 1, wherein the evaluation is performed on the basis of The exposure apparatus according to claim 1, wherein the first light flux and the second light flux have different wavelengths.   The exposure apparatus according to any one of claims 1 to 3, wherein the first mark and the second mark are formed on the same surface of the reference plate. The exposure apparatus according to any one of claims 1 to 4, wherein a plurality of measurement systems are disposed around an exposure area of the projection optical system. The exposure apparatus according to claim 5, wherein the measurement system is disposed across the exposure region. The exposure apparatus according to any one of claims 2 to 6, wherein the reflection section is provided at a position conjugate to the reference plate. A drive unit for driving the measurement system;
The exposure apparatus according to any one of claims 1 to 7, wherein the drive unit drives the measurement system into an exposure area of the projection optical system. A step of exposing a substrate using the exposure apparatus according to any one of claims 1 to 8.
Developing the substrate exposed in the step;
A method of producing an article comprising obtaining an article from a developed substrate.

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