JP2018013510A - Optical device, lithography device and manufacturing method of article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device capable of preventing an operation rate from decreasing when a trouble of an actuator is detected.SOLUTION: An optical device is configured to deform a mirror face 1a being a reflection surface of a mirror 1. The optical device includes: a plurality of actuators 4 configured to drive to apply a force for deforming the mirror face 1a to the mirror 1; a trouble detection part 10 configured to detect an abnormality of the actuator 4; and a trouble shooting part 11 configured to determine whether or not to continue driving without changing the actuator, if the abnormality is detected by the trouble detection part 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical apparatus, a lithographic apparatus, and an article manufacturing method.

  In order to increase the resolution in the exposure apparatus, exposure aberration correction using a deformable mirror has been proposed. The deformable mirror incorporates a plurality of actuators for deforming the mirror. However, the actuator may break down due to defective production, poor assembly, aging of components, and the like. Therefore, it is necessary to provide failure diagnosis means for diagnosing whether or not the actuator has failed and perform failure diagnosis in real time or periodically. Patent Document 1 discloses a technique that prohibits updating of the correspondence between the displacement of the movable element and the drive signal by the calibration unit when the abnormality determination unit determines abnormality.

JP 4435691 A

  However, when the actuator of the deformable mirror breaks down, the exposure apparatus equipped with the deformable mirror unit needs to stop the apparatus for exchanging the actuator, leading to a reduction in the operating rate of the apparatus. Patent Document 1 does not disclose a technique related to an apparatus operating rate when an abnormality of a microactuator is determined.

  For example, an object of the present invention is to provide an optical device that can suppress a reduction in operating rate when a failure of an actuator is detected.

  In order to solve the above problem, an optical device according to one aspect of the present invention is an optical device that deforms a reflective surface of an optical element, and applies a force that deforms the reflective surface of the optical element to the optical element. A plurality of actuators that are driven at the same time, a detection unit that detects an abnormality of the actuator, and whether or not to continue the drive without replacing the actuator in which the abnormality is detected when the detection unit detects an abnormality A failure countermeasure unit for determining whether or not.

  ADVANTAGE OF THE INVENTION According to this invention, the optical apparatus which can suppress the fall of an operation rate when the failure of an actuator is detected can be provided, for example.

It is a figure which shows the structure of 1st Embodiment. It is a figure explaining the countermeasure of the failure countermeasure part of 1st Embodiment. It is a figure which shows the structure of 2nd Embodiment. It is a figure explaining the countermeasure of the failure countermeasure part of 2nd Embodiment. It is a figure which shows schematic structure of exposure apparatus.

(First embodiment)
FIG. 1 is a diagram illustrating a basic configuration of an optical device according to the first embodiment. The optical device includes a mirror 1, a holding member 2, a base plate 3, and a plurality of actuators 4. The optical apparatus according to the present embodiment further includes a failure detection unit 10, a failure countermeasure unit 11, a table data storage unit 12, a drive control unit 13, and a drive command calculation unit 14. The mirror 1 is a deformable optical element, and has a mirror surface 1a that is a reflective surface and a back surface 1b that is a surface opposite to the reflective surface. The mirror 1 is fixed to the base plate 3 via a holding member 2. The actuator 4 includes a magnet 4a and a coil 4b. The magnet 4 a is bonded to the back surface 1 b of the mirror, and the coil 4 b is fixed to the base plate 3. The coil 4b is disposed so as to face the magnet 4a through a gap. By passing a current through the coil 4b, a force proportional to the current is generated between the magnet 4a and the coil 4b, and the mirror 1 can be deformed. Therefore, the actuator 4 can change the shape and position / posture of the mirror 1.

  The failure detection unit 10 detects an abnormality by monitoring the operating state of the actuator 4. For example, the abnormality is detected by monitoring the current flowing through the coil 4b. Note that the abnormality detection method is not limited to this, and other methods such as monitoring the drive displacement in each actuator 4 with a displacement meter or the like to detect abnormality including the magnet 4a and the coil 4b. Also good.

  When the failure detection unit 10 does not detect a failure of the actuator 4, table data (information) representing the relationship between the drive command value of each actuator and the mirror deformation amount stored in advance in the table data storage unit 12 is: It is sent to the drive command calculation unit 14 as it is. Further, on the system 15 side, in order to improve the optical performance, information to be corrected by the deformable mirror unit is calculated in the shape of the target shape, and the target shape is sent to the drive command calculation unit 14 of the deformable mirror unit.

  The drive command calculation unit 14 calculates a drive command value from the table data and the target shape. It is determined whether or not the calculated drive command value is within the allowable range. If the calculated drive command value is within the allowable range, the calculated drive command value is sent to the drive control unit 13 to perform deformation driving of the mirror. If the drive command value exceeds the allowable range, the mirror deformation drive operation is stopped (STOP) to protect the device. Whether or not the drive command value is within the allowable range is determined by whether or not the drive command value is equal to or less than a limiter (threshold value) that is a threshold value.

  When a failure of the actuator 4 is detected by the failure detection unit 10, the failure countermeasure unit 11 determines whether or not to continue using the device. Even if there is a faulty actuator, if the remaining actuator can meet the desired deformation drive accuracy, continue to use the device equipped with the deformable mirror unit. If not, replace or repair the faulty actuator. Do.

  Details of the determination as to whether or not to continue using the device performed by the failure countermeasure unit 11 will be described with reference to FIG. When a failure of the actuator is detected from the failure detection unit 10, the index j (j = 1, 2,... N, where N is the number of actuators) of the corresponding actuator is sent to the failure countermeasure unit 11. The index is individually assigned to all actuators.

In step S201, the failure countermeasure unit 11 reads a data matrix CM that is table data representing the relationship between the drive command value of the actuator 4 and the mirror deformation amount stored in advance in the table data storage unit 12. In Expression (1), M is the number of points necessary to calculate the mirror surface shape.

  Two methods are mainly used to create the data matrix CM. First, the deformation shape of the mirror when each actuator is driven with a certain drive command value is represented by M points on the mirror surface, and the ratio between the displacement of the M points and the drive command value is used. Is the method. The second is to fit the deformed shape of the mirror when each actuator is driven with a certain drive command value using up to M terms of the Zernike polynomial, which is often used in the optical field, and use the ratio of the Zernike coefficient to the drive command value. It is a way of expressing.

  The first method needs to use a sufficient number of points to express the mirror shape with the required accuracy. Therefore, in general, the number of actuators that are arranged is sufficient, but when it is necessary to accurately estimate the shape accuracy of the mirror, the value of M in the data matrix CM may be as large as thousands or tens of thousands. There are many. On the other hand, the second method requires a sufficient number of data points to acquire the mirror deformed shape when driven by an actuator in order to acquire data for creating the data matrix CM. However, after fitting this with a Zernike polynomial, the size of M of the data matrix CM is determined by the number of terms of the polynomial. In general, the number of terms of the Zernike polynomial is often up to 36 terms, and when high accuracy is required, it is satisfactory in most cases when considering up to 169 terms. Therefore, the second method has an advantage that the size of the data matrix CM can be made sufficiently smaller than the first method, and the calculation time of the drive command can be shortened.

In step S202, the data string corresponding to the failed actuator j (column surrounded by the broken line in equation (1)) is deleted, and the table data CMs reduced as in equation (2) is regenerated.

In step S203, the drive command value of each actuator other than the actuator in which the failure is detected is calculated as shown in Expression (3) from the reduced table data CMs and the target shape sent from the system 15 side.

  In step S204, in order to determine whether or not the drive command value is within the allowable range, it is determined whether or not it is within the limiter of each actuator. If there is a drive command value that exceeds the drive limiter of the actuator, the deformation drive with the drive command value may cause damage to the device, so that the process proceeds to step S207 to enter the actuator replacement process. If the drive command value is within the actuator limiter, the process proceeds to step S205.

In step S205, the deformation drive shape of the mirror obtained as a result of driving the actuator using the drive command value is calculated using equation (4).

  In step S206, it is determined whether or not the shape error calculated from the difference shape between the calculated deformation drive shape and the target shape is within an allowable value. If the shape error exceeds the allowable value, the deformable mirror unit does not satisfy the desired accuracy. Therefore, the actuator in which the abnormality is detected cannot be used as it is, and the process proceeds to S208 and the actuator replacement process is executed. When the shape error is within the allowable range, the drive command value is sent to the drive control unit 13 to cause the actuator that has not failed to execute the deformation drive.

  According to the present embodiment, depending on the target shape sent from the system 15 side, even if there is an actuator in which an abnormality is detected, it may be possible to drive to the target shape with only other actuators. Drive without stopping. Therefore, it is possible to suppress a reduction in the operating rate of the apparatus. In the present embodiment, the countermeasure against failure has been described using an example of a voice coil motor including a magnet and a coil, but the present invention is not limited to the voice coil motor. Other actuators such as an actuator using an electromagnet, a piezoelectric actuator, a magnetostrictive element, a microactuator, or the like may be used. In addition, when the actuator is replaced, the relationship between the drive command value and the mirror deformation amount changes when the characteristics of the replaced actuator differ from the actuator after replacement. Therefore, it is necessary to update the table data representing the relationship. is there.

(Second Embodiment)
The difference between the second embodiment and the first embodiment is whether the reduced table data is stored in the failure countermeasure unit 11 or stored in the table data storage unit 12. In the present embodiment, a command for overwriting the reduced table data (formula (2)) is sent to the table data storage unit 12 to update the data in the table data storage unit 12. Hereinafter, the second embodiment will be described with reference to FIG. 3 and FIG. 4. The same reference numerals as those in the first embodiment are used for the same configurations and steps as those in the first embodiment, and the description thereof will be omitted.

  FIG. 3 is a diagram illustrating a basic configuration of the optical device according to the second embodiment. When the failure countermeasure unit 11 determines that the device can be used continuously despite a failure detected in the actuator, a table data update command is sent to the table data storage unit 12. Upon receiving the update command, the table data storage unit 12 updates the stored table data to the reduced table data by excluding data related to the failed actuator.

  FIG. 4 is a diagram for explaining the details of the determination as to whether or not to continue using the device performed by the failure countermeasure unit 11. If the failure countermeasure unit 11 determines in step S206 that the shape error is within the allowable range, that is, determines that the use of the apparatus can be continued, the failure countermeasure unit 11 proceeds to step S402. In step S402, the failure countermeasure unit 11 sends a command to the table data storage unit 12 to update the table data.

  Only the storage location of the reduced table data is different, and in this embodiment as well, as in the first embodiment, a reduction in the operating rate of the apparatus can be suppressed. In order to effectively suppress a decrease in the apparatus operating rate due to a failure, the number of actuators may be arranged in excess of the necessary minimum, and the countermeasure of the present invention may be applied. However, in this case, there is a trade-off between space and cost for arranging an extra actuator, ease of maintenance, and the like. In addition, even if there is a faulty actuator, it can be considered that this actuator is regarded as normal, the drive command value is calculated, and the input to the faulty actuator is set to zero when the drive command value is sent to the drive control unit. It is done. Even in such a method, the apparatus can continue to operate without exchanging the actuator.

(Third embodiment)
FIG. 5 is a view showing a schematic configuration of the exposure apparatus. The exposure apparatus 50 may include an illumination optical system IL, a projection optical system UM, a mask stage MS that can move while holding the mask 55, and a substrate stage PS that can move while holding the substrate 56. The exposure apparatus 50 includes a control unit 51 that controls processing for exposing the substrate 56.

  Light emitted from a light source (not shown) included in the illumination optical system IL forms, for example, an arc-shaped illumination region that is long in the Y direction on the mask 55 by a slit (not shown) included in the illumination optical system IL. can do. The mask 55 and the substrate 56 are respectively held by the mask stage MS and the substrate stage PS, and are optically conjugate positions (positions of the object plane and the image plane of the projection optical system UM) via the projection optical system UM. Be placed. The projection optical system UM has a predetermined projection magnification (for example, ½ times), and projects the pattern formed on the mask 55 onto the substrate 56. Then, the mask stage MS and the substrate stage PS are scanned in a direction parallel to the object plane of the projection optical system UM (for example, the X direction in FIG. 5) at a speed ratio corresponding to the projection magnification of the projection optical system UM. Thereby, the pattern formed on the mask 55 can be transferred to the substrate 56.

  For example, as shown in FIG. 5, the projection optical system UM is configured to include a plane mirror 52, a mirror 1 that is a concave mirror, and a convex mirror 54. The exposure light emitted from the illumination optical system IL and transmitted through the mask 55 has its optical path bent by the first surface 52 a of the plane mirror 52 and is incident on the first surface 1 a 1 of the mirror 1. The exposure light reflected by the first surface 1a1 of the mirror 1 is reflected by the convex mirror 54 and enters the second surface 1a2 of the mirror 1. The exposure light reflected by the second surface 1 a 2 of the mirror 1 is bent on the optical path by the second surface 52 b of the plane mirror 52 and forms an image on the substrate 56. In this embodiment, an example of application to an exposure apparatus has been described. However, an apparatus to which the optical apparatus according to the above embodiment can be applied forms a latent image pattern of a resist on a substrate by irradiation with EUV light, for example. There is a lithographic apparatus. In addition, the present invention can be applied to a laser processing apparatus, a fundus photographing apparatus, a telescope, and the like.

(Embodiment related to article manufacturing method)
The method for manufacturing an article according to the present embodiment is suitable for manufacturing an article such as a microdevice such as a semiconductor device or an element having a fine structure, for example. In the method for manufacturing an article according to the present embodiment, a latent image pattern is formed on the photosensitive agent applied to the substrate using the above-described exposure apparatus (a step of exposing the substrate), and the latent image pattern is formed in this step. Developing the substrate. Further, the manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like). The method for manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 1 Mirror 1a Mirror surface 1b Mirror back surface 4 Actuator 4a Magnet 4b Coil 10 Failure detection part 11 Failure countermeasure part

Claims (11)

An optical device for deforming a reflective surface of an optical element,
A plurality of actuators for driving the optical element to apply a force to deform the reflecting surface of the optical element;
A detection unit for detecting an abnormality of the actuator;
An optical device comprising: a failure countermeasure unit that determines whether or not to continue the driving without replacing the actuator in which the abnormality is detected when an abnormality is detected in the detection unit.   The failure countermeasure unit, when an abnormality is detected in the detection unit, changes a drive command value of an actuator other than the actuator in which the abnormality is detected among the plurality of actuators, and each of the changed actuators 2. The optical apparatus according to claim 1, wherein if the drive command value is within an allowable range, it is determined that the drive is continued without replacing the actuator in which the abnormality is detected.   The failure countermeasure unit calculates the shape of the optical element obtained as a result of driving with the changed drive command value, and if the shape error between the calculated shape and the target shape is within an allowable range, the abnormality is The optical apparatus according to claim 2, wherein it is determined that the driving is continued without replacing the detected actuator.   The failure countermeasure unit changes a drive command value of an actuator other than the actuator in which the abnormality is detected based on information indicating a relationship between a drive command value of the plurality of actuators and a deformation amount of the reflecting surface. The optical apparatus according to claim 1, wherein the optical apparatus is characterized in that:   The optical device according to claim 4, wherein the failure countermeasure unit calculates a shape of the optical element obtained as a result of driving with the changed drive command value based on the information. A storage unit for storing the information;
The optical device according to claim 4, wherein the failure countermeasure unit reads the information from the storage unit.   7. The actuator according to claim 1, wherein the actuator includes a magnet attached to a surface opposite to the reflecting surface, and a coil disposed at a position facing the magnet. Optical device.   The optical device according to claim 7, wherein the detection unit detects an abnormality of the actuator based on a current flowing through the coil. A control method of an optical device that deforms the reflecting surface by a plurality of actuators that are driven to apply a force that deforms the reflecting surface of the optical element to the optical element,
Detecting an abnormality of the actuator;
When the abnormality is detected, a step of changing a drive command value of an actuator other than the actuator from which the abnormality is detected among the plurality of actuators;
Determining whether the changed drive command value of each actuator is within an allowable range; and
A step of calculating a shape of the optical element obtained as a result of driving with the changed drive command value when it is determined that the drive command value is within an allowable range;
Determining whether a shape error between the calculated shape and the target shape is within an allowable range;
And a step of continuing the driving without replacing the actuator in which the abnormality is detected when it is determined that the shape error is within an allowable range.   An exposure apparatus comprising the optical apparatus according to claim 1. Exposing the substrate using the exposure apparatus according to claim 10;
Developing the exposed substrate. A method for manufacturing an article.

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