Optical device and method for controlling the optical device

Abstract

This invention provides an optical device that can achieve a focusing height even with a pellicle-equipped mask, and a method for controlling the optical device. [Solution] The optical device 1 according to the present disclosure is an optical device 1 that acquires the focus height for each of a plurality of positions on the surface on the side where a pattern P of a mask with a pellicle 62 is formed, and comprises an illumination optical system 10 that illuminates the surface with light L1, a detector 30 that detects reflected light L2 reflected from the surface by light L1, an illumination control unit 20 that controls the output of light L1, and a processing unit 40 that acquires the focus height of a measurement position based on the detection result of the detector 30 when the measurement position to be measured is illuminated with light L1, and the surface includes a first region A1 not covered by the pellicle 62 and a second region A2 covered by the pellicle 62, and the detector 30 detects reflected light L2 of a predetermined intensity or higher when the first region A1 is illuminated with light L1 of a first output.

Description

Technical Field

[0001] The present disclosure relates to an optical device and a method for controlling the optical device.

Background Art

[0002] In an inspection apparatus that inspects an object such as a photomask using light including the wavelength of EUV (Extreme Ultra Violet) (referred to as EUV light), the inspection illumination of the EUV light is focused and irradiated at a height position suitable for inspecting the object, and light generated from the object irradiated with the inspection illumination is detected in a favorable focused state by the imaging optical system of the inspection apparatus. It is preferable to measure the focus height for each planar coordinate of the object.

[0003] For example, Patent Document 1 discloses an apparatus that measures the focus height using an optical lever.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, in a mask with a pellicle, since the transmittance of the illumination used when measuring the focus height varies depending on the pellicle, an improvement in the measurement of the focus height considering this is required.

[0006] An object of the present disclosure is to provide an optical device and a method for controlling the optical device that can obtain the focus height even for a mask with a pellicle in order to solve such problems.

Means for Solving the Problems

[0007] The optical device according to this disclosure is an optical device for acquiring the focus height for each of a plurality of positions on the surface on which a pattern is formed of a pellicle-attached mask, comprising: an illumination optical system for illuminating the surface with light; a detector for detecting reflected light reflected from the surface; an illumination control unit for controlling the output of the light; and a processing unit for acquiring the focus height of a measurement position among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with light, wherein the surface includes a first region not covered by the pellicle and a second region covered by the pellicle, and the detector is configured such that the first region is first When the second region is illuminated with the output light, the reflected light of a predetermined intensity or greater is detected; when the second region is illuminated with the first output light, the reflected light of a predetermined intensity or greater is not detected; when the second region is illuminated with the second output light which is greater than the first output light, the reflected light of a predetermined intensity or greater is detected; when the measurement position is illuminated and the detector detects the reflected light of a predetermined intensity or greater, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light; and the illumination control unit illuminates the surface included in the second region with the second output light.

[0008] The optical device further comprises a scanning unit that changes the relative position of the mask and the illumination position of the light relative to the mask, and the illumination control unit may illuminate the measurement position with the first output light when the surface included in the second region of the mask is set as the measurement position for the first time after the mask has been loaded, and illuminate the measurement position with the second output light when the detector does not detect reflected light of a predetermined intensity or higher.

[0009] The optical device according to this disclosure is an optical device for acquiring the focus height for each of a plurality of positions on the surface on which a pattern of a mask is formed, comprising: an illumination optical system for illuminating the surface with light; a detector for detecting reflected light reflected by the light from the surface; an illumination control unit for controlling the output of the light; a processing unit for acquiring the focus height of a measurement position among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with light; and a scanning unit for changing the relative position of the mask and the illumination position of the light with respect to the mask, wherein the processing unit When the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or greater, the focusing height of the measurement position is obtained based on the detection result of the detected reflected light. The surface includes a peripheral region and a central region, and the illumination control unit illuminates the measurement position with the first output of light when the surface included in the central region of the mask is designated as the measurement position for the first time after the mask has been loaded. If the detector does not detect reflected light of a predetermined intensity or greater, the illumination control unit illuminates the measurement position with the second output of light, which is greater than the first output.

[0010] In the optical apparatus described above, the illumination control unit may, after the mask has been loaded and before the surface included in the central region is designated as the measurement position, illuminate the surface included in the peripheral region with the light of the first output as the measurement position, and the processing unit may obtain the focus height of the measurement position. Subsequently, the illumination control unit may illuminate the surface included in the central region with the light of the first output as the measurement position, and if the detector does not detect reflected light with a value equal to or greater than the predetermined intensity, illuminate the measurement position with the light of the second output, and the processing unit may obtain the focus height of the measurement position belonging to the central region based on the detection result that the detector has detected reflected light with a value equal to or greater than the predetermined intensity.

[0011] In the optical device described above, if the focus height of a measurement position belonging to the peripheral region is to be acquired after the focus height of the measurement position belonging to the central region has been acquired, the illumination control unit may illuminate the measurement position belonging to the peripheral region with the light of the second output.

[0012] In the optical device described above, the peripheral region includes a first peripheral region, a second peripheral region, a third peripheral region, and a fourth peripheral region that surround the four sides of the central region and have different directions when viewed from the central region. The illumination control unit may, after the mask is loaded and before the surface included in the central region is designated as the measurement position, illuminate the surface included in the first peripheral region, the surface included in the second peripheral region, the surface included in the third peripheral region, and the surface included in the fourth peripheral region with the light of the first output, each as the measurement position, and then illuminate the surface included in the central region with the light of the first output, with the surface included in the central region as the measurement position.

[0013] In the optical device described above, the peripheral region includes a first peripheral region and a second peripheral region that is opposite to the first peripheral region with the central region in between. The illumination control unit illuminates the surface included in the first peripheral region and the surface included in the second peripheral region with the first output light as the measurement position after the mask has been loaded and before the surface included in the central region is designated as the measurement position. Subsequently, the illumination control unit illuminates the surface included in the central region with the first output light as the measurement position. The processing unit may limit the acquisition of the focus height for the central region during the process in which the measurement position changes from the surface included in the first peripheral region to the surface included in the second peripheral region.

[0014] In the optical device described above, the processing unit may determine whether the pellicle is torn based on the difference in detection results when the first region and the second region are illuminated with light of substantially equal output, including at least one of the first output or the second output.

[0015] In the optical apparatus described above, the processing unit may determine whether the pellicle covering the surface of the mask is torn based on the difference in detection results when the peripheral region and the central region are illuminated with light of substantially equal output, including at least one of the first output or the second output.

[0016] In the optical device described above, the processing unit may determine if the pellicle is torn when the difference is less than or equal to a threshold.

[0017] In the optical device described above, the threshold value may be set based on the transmittance of the pellicle.

[0018] The optical device control method according to this disclosure is a method for controlling an optical device that acquires the focus height for each of a plurality of positions on the surface on which a pattern of a pellicle-attached mask is formed, comprising: illuminating the surface with light using an illumination optical system; controlling the output of the light using an illumination control unit; detecting reflected light reflected from the surface using a detector; and acquiring the focus height of a measurement position among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with light using a processing unit, wherein the surface includes a first region not covered by the pellicle and a second region covered by the pellicle, and in the step of detecting the reflected light, the detector In the step of obtaining the focus height, the output device detects reflected light of a predetermined intensity or greater when the first region is illuminated with the light of the first output, does not detect reflected light of a predetermined intensity or greater when the second region is illuminated with the light of the first output, and detects reflected light of a predetermined intensity or greater when the second region is illuminated with the light of the second output which is greater than the first output, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light when the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or greater, and controls the output of the light, the illumination control unit illuminates the surface included in the second region with the light of the second output.

[0019] The above optical device control method further includes a step of changing the relative position of the mask and the illumination position of the light relative to the mask by a scanning unit, and in the step of controlling the output of the light, the illumination control unit may illuminate the measurement position with the first output of light when the surface included in the second region of the mask is set as the measurement position for the first time after the mask has been loaded, and illuminate the measurement position with the second output of light when the detector does not detect reflected light of a predetermined intensity or higher.

[0020] A control method for an optical device according to this disclosure is a control method for an optical device that acquires the focus height for each of a plurality of positions on the surface on which a pattern of a mask is formed, comprising: illuminating the surface with light using an illumination optical system; detecting reflected light reflected from the surface using a detector; controlling the output of the light using an illumination control unit; acquiring the focus height of a measurement position among the plurality of positions on the surface based on the detection result of the detector when the measurement position to be measured is illuminated with light using a processing unit; and changing the relative position of the mask and the illumination position of the light with respect to the mask using a scanning unit. In the step of obtaining the focus height, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light when the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or greater, and the surface includes a peripheral region and a central region, and in the step of controlling the output of the light, the illumination control unit illuminates the measurement position with the first output of the light when the measurement position is the surface included in the central region of the mask for the first time after the mask has been loaded, and illuminates the measurement position with the second output of the light which is greater than the first output when the detector does not detect reflected light of a predetermined intensity or greater.

[0021] The above-described control method for the optical device may, in the step of controlling the output of the light, illuminate the surface included in the peripheral region with the first output of light as the measurement position after the mask has been loaded and before the surface included in the central region is designated as the measurement position, and in the step of obtaining the focus height, the processing unit obtains the focus height of the measurement position thereafter, and in the step of controlling the output of the light, illuminate the surface included in the central region with the first output of light as the measurement position, and if the detector does not detect reflected light with a value of a predetermined intensity or higher, illuminate the measurement position with the second output of light, and in the step of obtaining the focus height, the processing unit may obtain the focus height of the measurement position belonging to the central region based on the detection result that the detector has detected reflected light with a predetermined intensity or higher.

[0022] In the above-described control method for the optical device, in the step of acquiring the focus height, after acquiring the focus height of the measurement position belonging to the central region, the focus height of the measurement position belonging to the peripheral region is acquired, and in the step of controlling the output of the light, the illumination control unit may illuminate the measurement position belonging to the peripheral region with the light of the second output.

[0023] In the above-described method for controlling the optical device, the peripheral region includes a first peripheral region, a second peripheral region, a third peripheral region, and a fourth peripheral region that surround the four sides of the central region and have different directions when viewed from the central region, and in the step of controlling the output of the light, the illumination control unit may, after the mask has been loaded and before the surface included in the central region is designated as the measurement position, illuminate the surface included in the first peripheral region, the surface included in the second peripheral region, the surface included in the third peripheral region, and the surface included in the fourth peripheral region with the light of the first output, each as the measurement position, and then illuminate the surface included in the central region with the light of the first output, with the surface included in the central region as the measurement position.

[0024] In the control method of the optical device, the peripheral region includes a first peripheral region and a second peripheral region facing the first peripheral region with the central region interposed therebetween. In the step of controlling the output of the light, after the mask is loaded and before the surface included in the central region is set as the measurement position, the illumination control unit illuminates the surface included in the first peripheral region and the surface included in the second peripheral region with the light of the first output as the measurement position, respectively. Then, the surface included in the central region is illuminated with the light of the first output as the measurement position. In the step of acquiring the focusing height, the processing unit may limit the acquisition of the focusing height for the central region in the process of the measurement position changing from the surface included in the first peripheral region to the surface included in the second peripheral region.

[0025] In the control method of the optical device, the processing unit may further include a step of determining the breakage of the pellicle based on the difference in the detection results when illuminating the first region and the second region with the light of substantially equal output including at least one of the first output or the second output.

[0026] In the control method of the optical device, the processing unit may further include a step of determining the breakage of the pellicle covering the surface of the mask based on the difference in the detection results when illuminating the peripheral region and the central region with the light of substantially equal output including at least one of the first output or the second output.

[0027] In the control method of the optical device, the processing unit may further include a step of determining the breakage of the pellicle when the difference is less than or equal to a threshold value.

[0028] In the control method of the optical device, the threshold value may be set based on the transmittance of the pellicle.

Effect of the Invention

[0029] This disclosure provides an optical device and a control method for the optical device that can achieve focus height even with a pellicle-equipped mask. [Brief explanation of the drawing]

[0030] [Figure 1] This is a diagram illustrating an optical device according to Embodiment 1. [Figure 2] This is a plan view illustrating an object in the optical device according to Embodiment 1. [Figure 3] This is a flowchart illustrating a control method for an optical device according to Embodiment 1. [Figure 4] This is a plan view illustrating an example of an object in the control method for an optical device according to Embodiment 2. [Figure 5] This is a plan view illustrating an example of an object in the control method for an optical device according to Embodiment 3. [Figure 6] This is a plan view illustrating an example of an object in the control method for an optical device according to Embodiment 4. [Figure 7] This is a diagram illustrating an inspection device according to Embodiment 6. [Modes for carrying out the invention]

[0031] The specific configuration of this embodiment will be described below with reference to the drawings. The following description illustrates preferred embodiments of the present disclosure, and the scope of the present disclosure is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same thing. Some reference numerals and hatching have been omitted to avoid cluttering the drawings.

[0032] <Embodiment 1> An optical device according to Embodiment 1 will be described. The optical device of this embodiment may include an inspection device for inspecting an object, and an exposure device for performing a lithography process using the object as a patterning device. The optical device may also include a review device for displaying the object on a monitor or the like. The optical device of this embodiment may include an inspection device for inspecting an object, an exposure device for performing a lithography process using the object as a patterning device, and a review device for displaying the object on a monitor or the like. Figure 1 is a configuration diagram illustrating an optical device 1 according to Embodiment 1. As shown in Figure 1, the optical device 1 comprises an illumination optical system 10, an illumination control unit 20, a detector 30, and a processing unit 40. In addition to these components, the optical device 1 may also include a scanning unit 50. The optical device 1 may also include other components such as optical elements. The optical device 1 acquires the focus height of the mask on the object 60. The focus height is the position on the upper surface 63 of the mask where a predetermined light, such as illumination light, is in focus. The upper surface 63 of the mask is sometimes referred to as the surface. The mask used on object 60 may be an EUV mask 61 used for EUV photography, or a mask used for photography other than EUV photography. Below, an EUV mask 61 will be described as an example, but the term "mask" may be used instead of the EUV mask 61. The EUV mask 61 and the mask may be collectively referred to simply as "mask."

[0033] Here, for the sake of explaining the optical device 1, we introduce the XYZ Cartesian coordinate system. The direction along the +Z axis is referred to as "up," and the direction along the -Z axis is referred to as "down." Note that "up" and "down" are merely for the sake of explaining the optical device 1 and do not indicate the actual direction in which the optical device 1 is positioned.

[0034] Figure 2 is a plan view illustrating an object 60 in the optical apparatus 1 according to Embodiment 1. As shown in Figures 1 and 2, the object 60 includes, for example, an EUV mask 61 with a pellicle 62. Therefore, the object 60 includes the EUV mask 61 and the pellicle 62. The direction from the EUV mask 61 toward the pellicle 62 is defined as the +Z axis direction. The surface of the EUV mask 61 on the +Z axis direction side is called the top surface 63. A pattern P is formed on at least a part of the top surface 63 of the EUV mask 61. In Figures 2 and later, the pattern P is omitted to avoid making the diagrams too complex.

[0035] A frame 64 is positioned on the upper surface 63 of the EUV mask 61. The frame 64 may be frame-shaped. For example, one frame-shaped frame 64 may be positioned to surround the central part of the EUV mask 61. Alternatively, multiple frames 64 may be positioned on the upper surface 63. Multiple frames 64 may be positioned to surround the central part of the upper surface 63 of the EUV mask 61. The frame 64 protrudes upward from the upper surface 63 of the EUV mask 61. The frame 64 supports the pellicle 62.

[0036] The pellicle 62 may be a thin film. The pellicle 62 may contain silicon (Si) as a material. The pellicle 62 may contain carbon nanotubes (CNT) as a material. The pellicle 62 is positioned to cover the upper surface 63 of the EUV mask 61. The pellicle 62 may be positioned to cover the central part of the upper surface 63 of the EUV mask 61. The pellicle 62 covers the upper surface 63 of the EUV mask 61 by being supported by a frame 64. As a result, the pellicle 62 is positioned with a gap between it and the upper surface 63 of the EUV mask 61. The pellicle 62 is positioned to cover at least a portion of the upper surface 63 of the EUV mask 61 for purposes such as preventing foreign matter from adhering to the pattern P formed on the upper surface 63 of the EUV mask 61.

[0037] The upper surface 63 of the EUV mask 61 on the object 60 may include a first region A1 and a second region A2. The first region A1 includes the area of ​​the upper surface 63 of the EUV mask 61 that is not covered by the pellicle 62. The second region A2 includes the area of ​​the upper surface 63 of the EUV mask 61 that is covered by the pellicle 62. The optical device 1 of this embodiment acquires the focus height at multiple positions on the upper surface 63 of the EUV mask 61 on the object 60. Specifically, the optical device 1 acquires the focus height at multiple positions on the upper surface 63 on the side of the EUV mask 61 with pellicle 62 on which the pattern P is formed. The upper surface 63 on the side of the EUV mask 61 with pellicle 62 on which the pattern P is formed may include the first region A1 and the second region A2.

[0038] The illumination optical system 10 illuminates the object 60, including the EUV mask 61 and the pellicle 62, with light L1. Specifically, the illumination optical system 10 illuminates the upper surface 63 of the EUV mask 61 with the pellicle 62 on the side where the pattern P is formed with light L1. The illumination optical system 10 may include a light source 11 that generates the light L1. The illumination optical system 10 may also guide light L1 generated by a separate, independent light source 11 into the interior of the illumination optical system 10. The wavelength of light L1 is, for example, in the visible range. The illumination optical system 10 may illuminate the object 60 with obliquely incident light L1. Alternatively, the illumination optical system 10 may illuminate the object 60 from directly above. The illumination optical system 10 may further include optical elements such as lenses, mirrors, neutral density filters, shutters, and apertures for oblique incident illumination or illumination from directly above.

[0039] The illumination optical system 10 may illuminate the first region A1 of the object 60 with light L1. The illumination optical system 10 may also illuminate the second region A2 of the object 60 with light L1. Furthermore, as will be described later, the illumination optical system 10 may illuminate the central region of the object 60 with light L1. Also, as will be described later, the illumination optical system 10 may illuminate the peripheral region of the object 60 with light L1. The transmittance of light L1 to the pellicle 62 is less than 100 percent.

[0040] The lighting control unit 20 controls the output of light L1 that the lighting optical system 10 uses to illuminate the object 60. For example, the lighting control unit 20 may control the output of light L1 by controlling the output of a light source 11 in the lighting optical system 10. Alternatively, the lighting control unit 20 may control the output of light L1 by controlling the output of a light source 11 separate from the lighting optical system 10. Furthermore, the lighting control unit 20 may control the output of light L1 by controlling the position and orientation of optical elements such as lenses, mirrors, neutral density filters, shutters, and apertures in the lighting optical system 10.

[0041] The lighting control unit 20 controls the output of light L1 to a first output. The lighting control unit 20 also controls the output of light L1 to a second output. For example, the second output is greater than the first output. The first and second outputs may include a predetermined range of outputs. The lighting control unit 20 may also control the light output to be less than the first output or greater than the second output.

[0042] The illumination control unit 20 may illuminate multiple positions included in the first region A1 with the first output light L1. The illumination control unit 20 may illuminate multiple positions included in the second region A2 with the first output light L1. The illumination control unit 20 may illuminate multiple positions included in the second region A2 with the second output light L1. The illumination control unit 20 illuminates the measurement position with the first output light L1. Subsequently, the illumination control unit 20 may illuminate the measurement position with the second output light L1. The illumination control unit 20 illuminates the measurement position with the first output light L1 when the upper surface 63 of the EUV mask 61 included in the second region A2 is designated as the measurement position for the first time after the EUV mask 61 has been loaded into the holding unit (for example, the stage 51). Then, the illumination control unit 20 illuminates the measurement position with the second output light L1 when the detector 30 does not detect reflected light L2 of a predetermined intensity or higher.

[0043] The detector 30 detects reflected light L2, which is the light L1 reflected from the object 60. Specifically, the detector 30 detects reflected light L2, which is reflected from the upper surface 63 of the EUV mask 61 with pellicle 62 on the side where the pattern P is formed. The reflected light L2, which is the light L1 reflected from the object 60, may be specular reflection. The detector 30 may include, for example, a TDI (Time Delay Integration) sensor or a CMOS sensor. The detector 30 outputs the detected information to the processing unit 40.

[0044] When the first region A1 is illuminated with the first output light L1, the detector 30 detects reflected light L2 of a predetermined intensity or higher. In other words, the illumination control unit 20 pre-adjusts or adjusts the value of the first output so that when the first region A1 is illuminated with the first output light L1, the detector 30 detects reflected light L2 of a predetermined intensity or higher. When the second region A2 is illuminated with the first output light L1, the detector 30 does not need to detect reflected light L2 of a predetermined intensity or higher. This is because at least a portion of the light L1 does not pass through the pellicle 62. On the other hand, when the second region A2 is illuminated with a second output that is greater than the first output, the detector 30 detects reflected light L2 of a predetermined intensity or higher. Although at least a portion of the light L1 does not pass through the pellicle 62, the detector 30 detects reflected light L2 of a predetermined intensity or higher because the object 60 is illuminated with a second output that is greater than the first output.

[0045] The relationship between the detection value of the detector 30 and the second output of the illumination control unit 20 is explained below. If T is the transmittance of light L1 to the pellicle 62, then, as an example, the second output is 1 / (T^2) times the first output. The illumination control unit 20 may determine the second output in this way if it can obtain the transmittance T. Alternatively, when illuminating the second region A2 or the central region B2 described later with the second output, the illumination control unit 20 may sequentially increase the output of light L1 from the first output until the detector 30 detects reflected light L2 of a target intensity of a predetermined intensity or higher, and refer to this output value as the value of the second output. Furthermore, when the illumination control unit 20 illuminates the second region A2 or the central region B2 described later with the second output, it may sequentially decrease the output of light L1, starting from a large output sufficient to detect reflected light L2 of a predetermined intensity or higher in the detector 30, regardless of the type of pellicle 62 attached (i.e., even if a pellicle 62 with the lowest transmittance rank is attached), and refer to the output value when the detector 30 detects reflected light L2 of a target intensity of a predetermined intensity or higher, and set this as the value of the second output. Alternatively, when the illumination control unit 20 illuminates the second region A2 or the central region B2 described later with the second output, it may change the output of light L1 randomly or in a predetermined sequence, and refer to the output value when the detector 30 detects reflected light L2 of a target intensity of a predetermined intensity or higher, and set this as the value of the second output. The target intensity may be defined as a certain range. Therefore, when the second region A2 is illuminated with a second output greater than the first output, the detector 30 can detect reflected light L2 of a predetermined intensity or greater.

[0046] The processing unit 40 obtains the focus height of a measurement position based on the detection result of the detector 30 when the measurement position to be measured is illuminated with light L1, among a plurality of positions on the upper surface 63 of the EUV mask 61. The measurement position to be measured is the position from which the focus height is to be obtained. It may also be simply called the measurement position. The processing unit 40 may obtain the focus height of the measurement position by any method. For example, the processing unit 40 may obtain the focus height of the measurement position using the principle of optical leverage. For example, the processing unit 40 may obtain the focus height of the measurement position based on which pixel among the plurality of pixels constituting the detector 30 detected light L2 of what intensity. For example, the processing unit 40 determines how far away a pixel is from a reference pixel that detected light L2 of a predetermined intensity, and obtains the focus height at that measurement position. The processing unit 40 may acquire the focus height at the measurement position based on how much positive or negative the height of the measurement position is moved relative to the reference height by driving a holding unit such as the stage 51, and how much light L2 of a predetermined intensity is detected at the reference pixel. The focus height may be acquired as a difference from the height at which the best focus should be achieved at the measurement position when the object 60 is supported at a specific height by the holding unit such as the stage 51 (this is the reference height), or as a value obtained by adding or subtracting this difference from the reference height. The focus height may be referred to as the height of the upper surface 63 at the measurement position, or the reference ratio height of the upper surface 63 at the measurement position, etc. When the measurement position is illuminated and the detector 30 detects reflected light L2 of a predetermined intensity or higher, the processing unit 40 acquires the focus height of the measurement position based on the detection result of the detected reflected light L2. The phrase "when the detector 30 detects reflected light L2 of a predetermined intensity or greater" may also mean, in view of the specifications of the EUV mask 61, when at least one of the multiple pixels arranged on the detector 30 so that the detector 30 can receive reflected light from the upper surface 63 regardless of how the upper surface 63 is bent, detects reflected light L2 of a predetermined intensity or greater.

[0047] The scanning unit 50 changes the relative position between the object 60 and the illumination position of the light L1 relative to the object 60. Specifically, the scanning unit 50 may change the illumination position to which the light L1 irradiates the object 60 by driving the illumination optical system or optical elements. The optical elements may be galvanometer mirrors or other known optical elements. The scanning unit 50 may also change the illumination position to which the light L1 irradiates the object 60 by changing the position of a holding part such as the stage 15, which will be described later. The scanning unit 50 thereby illuminates the object 60 with light L1 at any measurement position, including positions on the upper surface 63 belonging to the first region A1, positions on the upper surface 63 belonging to the second region A2, positions on the upper surface 63 belonging to the peripheral region B1, which will be described later, and positions on the upper surface 63 belonging to the central region B2, which will be described later. The positions (coordinate positions) of the first region A1, the second region A2, the peripheral region B1, and the central region B2 on the upper surface 63 may be determined by the scanning unit 50 based on the identification information of the object 60 and the coordinate positions of the alignment marks. In the following description, the scanning unit 50 will change the relative position between the object 60 and the illumination position of light L1 relative to the object 60 by changing the position of the holding part such as the stage 51.

[0048] The stage 51 supports the object 60. The stage 51 moves the object 60 in the X-axis, Y-axis, and Z-axis directions by changing its position by the scanning unit 50. Alternatively, the stage 51 may rotate the object 60 around the X-axis, Y-axis, and Z-axis as axes of rotation by changing its orientation by the scanning unit 50. The stage 51 is an example of a holding unit. The holding unit may be an arm or the like, in addition to the stage 51. Placing the object 60 on a holding unit such as the stage 51 (loading the object 60 into the holding unit) is sometimes called loading. The object 60 is loaded into the holding unit by a loader (not shown) and supported by the holding unit.

[0049] The housing 52 secures the illumination optical system 10 and the detector 30. The housing 52 may also secure other components. The illumination optical system 10 and the detector 30 may be secured to the housing 52 after optical adjustments such as predetermined optical path adjustments have been made. The illumination optical system 10 and the detector 30 may be secured to the housing 52 in such a way that their position and orientation can be changed by actuators or the like.

[0050] Next, the control method for the optical device 1 of this embodiment will be described. Figure 3 is a flowchart illustrating the control method for the optical device 1 according to Embodiment 1. As shown in Figure 3, the control method for the optical device 1 includes the steps of: illuminating the object 60 with light L1 in step S11; controlling the output of light L1 in step S12; detecting reflected light L2 in step S13; determining whether the intensity of the reflected light L2 is equal to or greater than a predetermined intensity in step S14; obtaining the focus height in step S15; determining whether to move to the next position in step S16; and moving to the next position in step S17. Below, we will first describe the steps S11 to S17 when illuminating the first region A1 of the object 60 with light L1. Then, we will describe the steps S11 to S17 when illuminating the second region A2 of the object 60 with light L1.

[0051] In step S11, the illumination optical system 10 illuminates the object 60, including the EUV mask 61 and the pellicle 62, with light L1. For example, the illumination optical system 10 illuminates the first region A1 of the object 60 with light L1.

[0052] In step S12, the lighting control unit 20 controls the output of light L1. For example, when the lighting optical system 10 illuminates the first region A1 of the object 60 with light L1, the lighting control unit 20 controls the output of light L1 to the first output. If the lighting control unit 20 is configured by default to set the output of light L1 to the first output, step S12 may be omitted.

[0053] In step S13, the detector 30 detects reflected light L2 that has been reflected by light L1 from the object 60. For example, if the first region A1 is illuminated by the first output light L1, the detector 30 detects reflected light L2 of a predetermined intensity or higher. The detector 30 outputs the detection result to the processing unit 40.

[0054] In step S14, the processing unit 40 determines whether the intensity of the reflected light L2 is equal to or greater than a predetermined intensity. For example, if the first region A1 is illuminated by the first output light L1 and the detector 30 detects reflected light L2 of a predetermined intensity or greater (Yes), the process proceeds to step S15.

[0055] In step S15, the processing unit 40 obtains the focus height of the measurement position in the first region A1 based on the detection result of the detected reflected light L2. Specifically, the processing unit 40 obtains the focus height of the measurement position in the first region A1, among multiple positions on the EUV mask 61, based on the detection result of the detector 30 when the measurement position to be measured is illuminated with light L1.

[0056] In step S16, the processing unit 40 determines whether to move to the next position. If it decides to move to the next position (Yes), the process proceeds to step S17.

[0057] In step S17, the scanning unit 50 moves the object 60 to the next position. For example, the scanning unit 50 moves the object 60 so that another measurement position in the first region A1 is illuminated by light L1. Alternatively, the scanning unit 50 may move the object 60 so that the second region A2 is illuminated by light L1. Then, the process returns to step S11. In the following, it will be assumed that in step S17, the scanning unit 50 moves the object 60 so that the second region A2 is illuminated by light L1.

[0058] In step S11, the illumination optical system 10 illuminates the second region A2 of the object 60 with light L1.

[0059] In step S12, when the illumination optical system 10 illuminates the second region A2 of the object 60 with light L1, the illumination control unit 20 controls the output of light L1 to the first output. If the illumination control unit 20 is configured by default to set the output of light L1 to the first output, step S12 may be omitted.

[0060] In step S13, if the second region A2 is illuminated with the first output light L1, the detector 30 does not detect reflected light L2 of a predetermined intensity or higher.

[0061] Therefore, in step S14, the processing unit 40 determines that the detector 30 does not detect reflected light L2 of a predetermined intensity or higher. In this case (No), the process proceeds to step S12.

[0062] In step S12, when the illumination optical system 10 illuminates the second region A2 of the object 60 with light L1, the illumination control unit 20 controls the output of light L1 to the second output. In this way, the illumination control unit 20 illuminates the position included in the second region A2 with the second output light L1. Thus, the illumination control unit 20 illuminates the measurement position in the second region A2 with the first output light L1, and then illuminates the measurement position with the second output light L2.

[0063] In that case, if the second region A2 is illuminated with the second output light L1 in step S13, the detector 30 detects reflected light L2 of a predetermined intensity or higher.

[0064] Therefore, in step S14, if the second region A2 is illuminated by the second output light L1, the processing unit 40 determines that the detector 30 has detected reflected light L2 of a predetermined intensity or higher. In this case (if Yes), the process proceeds to step S15.

[0065] In step S15, the processing unit 40 obtains the focus height of the measurement position in the second region A2 based on the detection result of the detected reflected light L2. Specifically, the processing unit 40 obtains the focus height of the measurement position in the second region A2, among multiple positions on the EUV mask 61, based on the detection result of the detector 30 when that measurement position is illuminated with light L1. In step S16, if the processing unit 40 determines that it will not move to the next position (No), the process is terminated.

[0066] In step 16, a decision may be made on whether to move to the next position based on whether or not the focus height was obtained for all measurement positions where the focus height should be obtained for the object 60.

[0067] Next, the effects of this embodiment will be described. The optical device 1 of this embodiment obtains reflected light L2 of a predetermined intensity or higher by illuminating the second region A2 covered by the pellicle 62 with light L1 of a higher output than the first region A1 not covered by the pellicle 62. As a result, the processing unit 40 can obtain the focus height of the upper surface 63 of the EUV mask 61 of the second region A2 covered by the pellicle 62. Furthermore, the processing unit 40 can obtain the focus height of both the upper surface 63 of the EUV mask 61 of the first region A1 not covered by the pellicle 62 and the second region A2 covered by the pellicle 62.

[0068] If the pellicle 62 is illuminated with high-intensity light L1, there is a risk of damage to the pellicle 62. In this embodiment, the object 60 is first illuminated with a low-intensity first-output light L1. Then, if the detector 30 cannot detect reflected light L2 of a predetermined intensity or higher, the output is changed to a second output which is higher than the first output. This suppresses damage to the pellicle 62 and allows for achieving a focus height even with the EUV mask 61 with the pellicle 62.

[0069] <Embodiment 2> Next, the optical device 1 and the control method for the optical device 1 of Embodiment 2 will be described. Figure 4 is a plan view illustrating the object 60 in the control method for the optical device 1 according to Embodiment 2. As shown in Figure 4, the object 60 of this embodiment includes a peripheral region B1 and a central region B2. The central region B2 includes the central region of the object 60. The peripheral region B1 includes the peripheral region of the object 60. The peripheral region B1 includes the region surrounding the central region B2. The peripheral region B1 may or may not correspond to the first region A1. The central region B2 may or may not correspond to the second region A2. In this embodiment, the object 60 is an EUV mask 61, but it is not necessary to know whether or not it has a pellicle 62. The central region B2 includes the central region of the upper surface 63 of the EUV mask 61. The peripheral region B1 includes the peripheral region of the upper surface 63 of the EUV mask 61. In this embodiment, the lighting control unit 20 illuminates the object 60 with the first output light L1, and then illuminates the object 60 with the second output light L1.

[0070] Furthermore, replacing the peripheral region B1 with the first region A1 and the central region B2 with the second region A2 in the following description also falls within the scope of the technical concept of this disclosure. Additionally, replacing the first region A1 with the peripheral region B1 and the second region A2 with the central region B2 in the above-described embodiment 1 also falls within the scope of the technical concept of this disclosure.

[0071] In this embodiment, first, as shown in Figure 4(i), the illumination optical system 10 illuminates the peripheral region B1 of the object 60 with light L1. The illumination control unit 20 illuminates the peripheral region B1 of the object 60 with the first output light L1. When the detected value at the detector 30 is equal to or greater than a predetermined intensity, the processing unit 40 obtains the focus height of the measurement position belonging to the peripheral region B1. In other words, the processing unit 40 obtains the focus height of the measurement position belonging to the peripheral region B1 based on the result of the detector 30 detecting reflected light L2 of equal or greater intensity. Here, the peripheral region B1 is the region not covered by the pellicle 62, even if the EUV mask 61 has a pellicle 62. Therefore, in this case (when the peripheral region B1 of the object 60 is illuminated with the first output light L1), the detected value of the reflected light L2 at the detector 30 is equal to or greater than a predetermined intensity.

[0072] Subsequently, as shown in Figure 4(ii), the illumination control unit 20 illuminates the central region B2 of the object 60 with the first output light L1. If the detected value at the detector 30 is less than a predetermined intensity, the illumination control unit 20 illuminates the central region B2 with the second output light L1. Then, if the detected value at the detector 30 when the measurement position is illuminated with the second output light L1 is equal to or greater than the predetermined intensity, the processing unit 40 obtains the focus height of the measurement position in the central region B2. In other words, the processing unit 40 obtains the focus height of the measurement position belonging to the central region B2 based on the result of the detector 30 detecting reflected light L2 of a predetermined intensity or greater. Here, the central region B2 is the region covered by the pellicle 62 if the EUV mask 61 has a pellicle 62. Therefore, if the EUV mask 61 has a pellicle 62 and the central region B2 of the object 60 is illuminated with the first output light L1, the detected value of the reflected light L2 at the detector 30 may be less than a predetermined intensity. Furthermore, when the EUV mask 61 is not equipped with a pellicle 62 and the central region B2 of the object 60 is illuminated with the first output light L1, the detected value of reflected light L2 by the detector 30 is equal to or greater than a predetermined intensity. Thus, in this embodiment, after the EUV mask 61 is loaded into the holding unit and before the upper surface 63 included in the central region B2 is designated as the measurement position, the illumination control unit 20 illuminates the upper surface 63 included in the peripheral region B1 with the first output light L1 as the measurement position. The processing unit 40 obtains the focus height of the measurement position. Subsequently, the illumination control unit 20 illuminates the upper surface 63 included in the central region B2 with the first output light L1 as the measurement position. If the illumination control unit 20 does not detect reflected light L2 with a detected value of equal or greater than a predetermined intensity by the detector 30, it illuminates the measurement position with the second output light L1. Based on the detection result that the detector 30 has detected reflected light L2 with equal or greater than a predetermined intensity, the processing unit 40 obtains the focus height of the measurement position belonging to the central region B2.

[0073] Furthermore, as shown in Figure 4(iii), if the focus height of another peripheral region B1 is to be acquired after acquiring the focus height of the measurement position in the central region B2, the illumination control unit 20 may illuminate the measurement position in the peripheral region B1 with the second output light L1. This reduces the number of times the illumination control unit 20 changes its output, simplifying control. Alternatively, if the focus height of another peripheral region B1 is to be acquired after acquiring the focus height of the measurement position in the central region B2, the illumination control unit 20 may illuminate the measurement position in the peripheral region B1 with the first output light L1. Note that in the figure, the peripheral region B1 and another peripheral region B1 are arranged opposite each other in the X-axis direction with the central region B2 in between, but this is not limited to this. The peripheral region B1 and another peripheral region B1 may be arranged opposite each other in the Y-axis direction with the central region B2 in between, or they may be arranged on the +X-axis side and the +Y-axis side as viewed from the central region B2, etc. Furthermore, peripheral region B1 does not need to surround central region B2 on all four sides. In other words, peripheral region B1 does not need to surround central region B2 on all four sides with another peripheral region B1.

[0074] In this embodiment, the control method for the optical device 1 is as follows: In step S11 of Figure 3, the illumination optical system 10 illuminates the peripheral region B1 of the object 60 with light L1 (Figure 4(i)). Next, in step S12, the illumination control unit 20 controls the output of light L1 to the first output. If the illumination control unit 20 is configured to set the output of light L1 to the first output by default, step S12 may be omitted. As a result, the illumination control unit 20 illuminates the peripheral region B1 of the object 60 with the first output light L1.

[0075] In step S13, the detector 30 detects reflected light L2 of a predetermined intensity or higher. In step S14, if the processing unit 40 determines that the detected value from the detector 30 is of a predetermined intensity or higher (Yes), in step S15, the processing unit 40 obtains the focus height of the measurement position belonging to the peripheral region B1. Then, in step S16, the processing unit 40 determines whether to move to the next position. If it decides to move to the next position (Yes), the scanning unit 50 moves the object 60. In step S17, the scanning unit 50 moves the object 60, for example, so that another measurement position in the peripheral region B1 is illuminated with light L1. Alternatively, the scanning unit 50 may move the object 60 so that the central region B2 is illuminated with light L1. In the following, it will be assumed that in step S17, the scanning unit 50 moved the object 60 so that the central region B2 is illuminated with light L1.

[0076] In step S11, the illumination optical system 10 illuminates the central region B2 of the object 60 with light L1 (Figure 4(ii)). In step S12, the illumination control unit 20 controls the output of light L1 to the first output. If the illumination control unit 20 is configured by default to set the output of light L1 to the first output, step S12 may be omitted. As a result, the illumination control unit 20 illuminates the central region B2 of the object 60 with the first output light L1.

[0077] In step S13, if the EUV mask 61 is a mask with a pellicle 62, the detector 30 does not detect reflected light L2 with an intensity greater than or equal to a predetermined level. Therefore, in step S14, the processing unit 40 determines that the detected value at the detector 30 is less than the predetermined level. In this case (No), the process proceeds to step S12. In step S12, the illumination control unit 20 controls the output of light L1 to the second output. As a result, the illumination control unit 20 illuminates the central region B2 of the object 60 with the light L1 of the second output.

[0078] As a result, in step S13, the detector 30 detects reflected light L2 of a predetermined intensity or higher. In step S14, the processing unit 40 determines that the value detected by the detector 30 is of a predetermined intensity or higher. In this case (if Yes), in step S15, the processing unit 40 obtains the focus height of the measurement position belonging to the central region B2.

[0079] In step S16, the processing unit 40 determines whether to move to the next position. If it decides to move to the next position (Yes), the scanning unit 50 moves the object 60. In step S17, the scanning unit 50 moves the object 60, for example, so that another measurement position in the central region B2 is illuminated by light L1. Alternatively, the scanning unit 50 may move the object 60 so that another peripheral region B1 is illuminated by light L1. In the following, it will be assumed that in step S17, the scanning unit 50 moved the object 60 so that another peripheral region B1 is illuminated by light L1.

[0080] In step S11, the illumination optical system 10 illuminates another peripheral region B1 of the object 60 with light L1 (Figure 4(iii)). In step S12, the illumination control unit 20 controls the output of light L1 to the second output. As a result, the illumination control unit 20 illuminates another peripheral region B1 of the object 60 with the second output light L1.

[0081] In step S13, the detector 30 detects reflected light L2 of a predetermined intensity or higher. In step S14, the processing unit 40 determines that the value detected by the detector 30 is of a predetermined intensity or higher. In this case (Yes), in step S15, the processing unit 40 obtains the focus height of a measurement position belonging to another peripheral region B1. In step S16, if the processing unit 40 determines that it will not move to the next position (No), the process is terminated.

[0082] According to this embodiment, even when there are peripheral regions B1 and central regions B2 whose correspondence with the first region A1 and the second region A2 is unknown, that is, even when it is unknown whether the object 60, which is the EUV mask 61, is a mask with a pellicle 62, the focus height can be obtained by controlling the output of light L1. Even in the case of an EUV mask 61 with a pellicle 62, since it is first illuminated with a small first output of light L1, the focus height can be obtained while suppressing damage to the pellicle 62. Other configurations and effects are described in Embodiment 1.

[0083] In this embodiment, the measurement position of the central region B1 of the object 60 may be illuminated and the focus height obtained before illuminating the measurement position of the peripheral region B1 of the object 60 and obtaining the focus height. In other words, the control method of the optical device 1 may be started from the second step S11 shown in (ii) of Embodiment 2 described above. Similar effects can be obtained with such a configuration.

[0084] <Embodiment 3> Next, the optical device 1 and the control method for the optical device 1 according to Embodiment 3 will be described. Figure 5 is a plan view illustrating an object 60 in the control method for the optical device 1 according to Embodiment 3. As shown in Figure 5, the object 60 in this embodiment has a peripheral region B1 and a central region B2, similar to Embodiment 2 described above. The peripheral region B1 surrounds the central region B2 on all four sides and includes a first peripheral region B11, a second peripheral region B12, a third peripheral region B13, and a fourth peripheral region B14, which have different directions when viewed from the central region B2. In this embodiment, the processing unit 40 acquires the focus height of the measurement position belonging to the central region B2 after acquiring the focus height of the measurement position belonging to the peripheral region B1 around the central region B2. Specifically, the scanning unit 50 scans the peripheral region B1 (B11 to B14) with light L1 so that the processing unit 40 can acquire the focus height at multiple positions belonging to the peripheral region B1, and then scans the central region B2 with light L1 so that the processing unit 40 can acquire the focus height at multiple positions belonging to the central region B2.

[0085] The illumination control unit 20 illuminates the peripheral region B1 of the object 60 with the first output light L1. The processing unit 40 obtains the focus height of the measurement position belonging to the peripheral region B1. Subsequently, the illumination control unit 20 illuminates the central region B2 of the object 60 with the first output light L1. Thus, in this embodiment, after the EUV mask 61 is loaded into the holding unit and before the upper surface 63 included in the central region B2 is designated as a measurement position, the illumination control unit 20 illuminates the upper surface 63 included in the first peripheral region B11, the upper surface 63 included in the second peripheral region B12, the upper surface 63 included in the third peripheral region B13, and the upper surface 63 included in the fourth peripheral region B14 with the first output light L1, each as a measurement position. Subsequently, the upper surface 63 included in the central region B2 is designated as a measurement position and illuminated with the first output light L1. If the detected value from the detector 30 is less than a predetermined intensity, the illumination control unit 20 illuminates the object 60 with the second output light L1. The processing unit 40 obtains the focus height of the measurement position belonging to the central region B2.

[0086] In the above example, the peripheral region B1 is shown as surrounding the central region B2 on all four sides, but this is not the only example. An optical device 1 according to Embodiment 3 is also included in which the focus height of measurement positions belonging to multiple peripheral regions B1 that are in contact with the central region B2 from different directions is obtained, and then the focus position of the measurement position belonging to the central region B2 is obtained.

[0087] The peripheral region B1 may surround the central region B2 from three sides. In this case, after the EUV mask 61 is loaded into the holding unit and before the upper surface 63 included in the central region B2 is designated as a measurement position, the illumination control unit 20 illuminates the upper surface 63 included in the first peripheral region B11, the upper surface 63 included in the second peripheral region B12, and the upper surface 63 included in the third peripheral region B13 with the first output light L1, each as a measurement position. Subsequently, the upper surface 63 included in the central region B2 is designated as a measurement position and illuminated with the first output light L1.

[0088] Furthermore, the peripheral region B1 may be in contact with the central region B2, comprising a first peripheral region B11 extending in the X-axis direction and a second peripheral region B12 extending in the Y-axis direction. In this case, after the EUV mask 61 is loaded into the holding unit and before the upper surface 63 included in the central region B2 is designated as a measurement position, the illumination control unit 20 illuminates the upper surface 63 included in the first peripheral region B11 and the upper surface 63 included in the second peripheral region B12 with the first output light L1, respectively, as measurement positions. Subsequently, the upper surface 63 included in the central region B2 is designated as a measurement position and illuminated with the first output light L1.

[0089] Furthermore, the peripheral region B1 may be a first peripheral region B11 and a second peripheral region B12 that are opposite each other, flanking the central region B2. In this case, after the EUV mask 61 is loaded into the holding unit and before the upper surface 63 included in the central region B2 is designated as a measurement position, the illumination control unit 20 illuminates the upper surface 63 included in the first peripheral region B11 and the upper surface 63 included in the second peripheral region B12 with the first output light L1, respectively, as measurement positions. Subsequently, the upper surface 63 included in the central region B2 is designated as a measurement position and illuminated with the first output light L1.

[0090] The processing unit 40 may restrict the acquisition of the focus height for the central region B2 during the process in which the measurement position changes from the upper surface 63 included in the first peripheral region B11 to the upper surface 63 included in the second peripheral region B12.

[0091] After the EUV mask 61 is loaded into the holding unit, and before the upper surface 63 included in the central region B2 is designated as the measurement position, the illumination control unit 20 may illuminate the upper surface 63 included in the first peripheral region B11 and the upper surface 63 included in the second peripheral region B12 with the first output light L1, in that order, as measurement positions. After that, the upper surface 63 included in the central region B2 may be designated as the measurement position and illuminated with the first output light L1. During the process in which the measurement position changes from the upper surface 63 included in the first peripheral region B11 to the upper surface 63 included in the second peripheral region B12, the output of light L1 may be stopped, or the acquisition of the focus height in the processing unit 40 may be restricted.

[0092] According to this embodiment, after scanning multiple peripheral regions B1 that are in contact with the central region B2 from different directions, the central region B2 is scanned to obtain the focus height. Therefore, the switching of the output of light L1 can be limited to only between the peripheral regions B1 and the central region B2. This simplifies the adjustment of light L1 for obtaining the focus height. Other configurations and effects are described in Embodiments 1 and 2.

[0093] <Embodiment 4> Next, the optical device 1 and the control method for the optical device 1 according to Embodiment 4 will be described. Figure 6 is a plan view illustrating an object 60 in the control method for the optical device 1 according to Embodiment 4. As shown in Figure 6, the object 60 in this embodiment has a peripheral region B1 and a central region B2, similar to Embodiments 2 and 3 described above. In this embodiment, the processing unit 40 obtains the focus height by scanning along a path that includes a path in which the regions are alternated in the order of peripheral region B1, central region B2, and peripheral region B1. Specifically, the scanning unit 50 scans the first peripheral region B11 with light L1 so that the processing unit 40 can obtain the focus heights of multiple positions belonging to the first peripheral region B11, and then scans the central region B2 with light L1 so that the processing unit 40 can obtain the focus heights of multiple positions belonging to the central region B2. After that, the scanning unit 50 scans the second peripheral region B12 with light L1 so that the processing unit 40 can obtain the focus heights of multiple positions belonging to the second peripheral region B12. Here, the first peripheral region B11 is the peripheral region B1 on the -X-axis side of the central region B2. The second peripheral region B12 is the peripheral region B1 on the +X-axis side of the central region B2. The second peripheral region B12 faces the first peripheral region B11 across the central region B2. Note that the first peripheral region B11 may also be the peripheral region B1 on the -Y-axis side of the central region B2. The second peripheral region B12 may also be the peripheral region B1 on the +Y-axis side of the central region B2. The second peripheral region B12 faces the first peripheral region B11 across the central region B2.

[0094] The illumination control unit 20 illuminates the object 60 with the first output light L1 in the first peripheral region B11. The processing unit 40 obtains the focus height of the measurement position belonging to the first peripheral region B11. Subsequently, the illumination control unit 20 illuminates the object 60 with the first output light L1 in the central region B2. If the detected value from the detector 30 is less than a predetermined intensity, the illumination control unit 20 illuminates the central region B2 with the second output light L1. The processing unit 40 obtains the focus height of the measurement position belonging to the central region B2.

[0095] The scanning unit 50 keeps the coordinate position of the object 60 in the Y-axis direction approximately constant, and changes the coordinate position in the X-axis direction toward a first direction, which is either the +X-axis direction or the -X-axis direction. Next, after the processing unit 40 has obtained the focus height at all the necessary measurement positions in the Y-axis direction, the scanning unit 50 moves the relative position of the object 60 by ΔY in the -Y-axis direction. Next, the scanning unit 50 keeps the coordinate position of the object 60 in the Y-axis direction approximately constant, and changes the coordinate position in the X-axis direction toward a second direction, which is opposite to the first direction. Next, after the processing unit 40 has obtained the focus height at all the necessary measurement positions in the Y-axis direction, the scanning unit 50 moves the relative position of the object 60 by ΔY in the -Y-axis direction. Next, the scanning unit 50 keeps the coordinate position of the object 60 in the Y-axis direction approximately constant, and changes the coordinate position in the X-axis direction toward a first direction. Through this zigzag scanning by the scanning unit 50, the processing unit 40 obtains the focus height at all necessary measurement positions on the object 60.

[0096] In this embodiment, the lighting control unit 20 may illuminate the second peripheral region B12 with the second output light L1 after illuminating the central region B2. If the detected value at the detector 30 does not exceed the detection limit intensity, the lighting control unit 20 may illuminate the second peripheral region B12 with the second output light L1.

[0097] According to this embodiment, the focus height at all necessary measurement positions on the object 60 can be sequentially acquired according to the path taken when inspecting the object 60, or according to the path taken when reviewing the object 60 or patterning the object 60. Furthermore, since the central region B2 and the second peripheral region B12 can be illuminated with the same second output light L1, the adjustment of the light L1 for acquiring the focus height can be simplified, as in Embodiment 2 and the like. Other configurations and effects are described in Embodiments 1 to 3.

[0098] <Embodiment 5> Next, an optical device 1 and a control method for the optical device 1 according to Embodiment 5 will be described. This embodiment determines whether the pellicle 62 is torn.

[0099] The processing unit 40 obtains detection results when the first region A1, which is not covered by the pellicle 62, and the second region A2, which is covered by the pellicle 62, are illuminated with the first output light L1. For example, the processing unit 40 obtains 15000 as the detection result for the first region A1 and 0 as the detection result for the second region A2. The processing unit 40 obtains 15000 as the difference between the detection result for the first region A1 and the detection result for the second region A2. If the threshold for judgment is 2000, the processing unit 40 determines in this case that the pellicle 62 is not broken.

[0100] Furthermore, the processing unit 40 may obtain detection results when the first region A1 and the second region A2 are illuminated with the second output light L1. For example, the processing unit 40 obtains 20000 as the detection result for the first region A1 and 5000 as the detection result for the second region A2. The processing unit 40 obtains 15000 as the difference between the detection result for the first region A1 and the detection result for the second region A2. If the threshold for judgment is 2000, the processing unit 40 will also determine that the pellicle 62 is not broken in this case.

[0101] On the other hand, when the processing unit 40 illuminates the first region A1 and the second region A2 with the first output light L1, it obtains 15000 as the detection result for the first region A1 and 14000 as the detection result for the second region A2. The processing unit 40 obtains 1000 as the difference between the detection result for the first region A1 and the detection result for the second region A2. If the threshold for judgment is 2000, the processing unit 40 determines in this case that the pellicle 62 is broken.

[0102] Furthermore, when the processing unit 40 illuminates the first region A1 and the second region A2 with the second output light L1, it obtains 20000 as the detection result for the first region A1 and 19000 as the detection result for the second region A2. The processing unit 40 obtains 1000 as the difference between the detection result for the first region A1 and the detection result for the second region A2. If the threshold for judgment is 2000, the processing unit 40 also determines that the pellicle 62 is broken in this case.

[0103] Thus, in this embodiment, the processing unit 40 determines that the pellicle 62 is torn based on the difference in detection results when the first region A1 and the second region A2 are illuminated with light L1 of substantially equal output including at least one of the first output or the second output. Specifically, the processing unit 40 determines that the pellicle 62 is torn when the difference in detection results when the first region A1 and the second region A2 are illuminated with light L1 of at least one of the first output or the second output is less than or equal to a threshold. Alternatively, the processing unit 40 may determine that the pellicle 62 covering the upper surface 63 of the EUV mask 61 is torn based on the difference in detection results when the peripheral region B1 and the central region B2 are illuminated with light L1 of substantially equal output including at least one of the first output or the second output.

[0104] The threshold may be set based on the material of the pellicle 62. Specifically, the threshold may be set based on the transmittance of the pellicle 62. If the transmittance of the pellicle 62 is high, the threshold should be set low. If the transmittance of the pellicle 62 is low, the threshold should be set high.

[0105] <Embodiment 6> Next, an optical device of Embodiment 6 will be described. This embodiment describes an inspection device that, as an example of an optical device, inspects an object 60 whose focus height at multiple measurement positions has been acquired based on illumination with light L1, using light L10 that is appropriately focused on the object 60 based on the acquired focus height. The object 60 may be an EUV mask 61 with a pellicle 62. The optical device may be an exposure device that performs a lithography process using the object 60 as a patterning device with light L10, or a review device that displays the object 60 illuminated by light L10 on a display or the like. Figure 7 is a configuration diagram illustrating an inspection device 2 according to Embodiment 6. As shown in Figure 7, the inspection device 2 includes an inspection optical system 70 and an imaging optical system 80.

[0106] The inspection optical system 70 illuminates the object 60 using illumination light L10. The inspection optical system 70 includes, for example, a light source 71, a collector mirror 72, an ellipsoidal mirror 73, and a recessed mirror 74.

[0107] The imaging optical system 80 images the object 60 illuminated by the illumination light L10. The imaging optical system 80 includes a perforated concave mirror 81, a convex mirror 82, and a detector 83. The perforated concave mirror 81 and the convex mirror 82 constitute a Schwarzschild magnifying optical system. The inspection optical system 70 and the imaging optical system 80 may further include optical components other than those described above, or any of the above optical components may be omitted.

[0108] The light source 71 generates illumination light L10, for example, EUV light. The light source 71 generates illumination light L10 from plasma generated by irradiating a molten metal such as molten tin (Sn) with excitation light. The illumination light L10 includes, for example, EUV light at 13.5 nm, the same wavelength as the exposure wavelength of the photomask for EUV light, which is the object 60.

[0109] The illumination light L10 generated from the light source 71 is reflected by the collector mirror 72. The light L10 reflected by the collector mirror 72 travels while being narrowed as convergent light and is focused at the focusing position IF. The focusing position IF is positioned conjugate to the upper surface 63 of the object 60.

[0110] After passing through the focusing position IF, the illumination light L10 spreads out as divergent light and travels towards a reflecting mirror such as the ellipsoidal mirror 73. The illumination light L10 that enters the ellipsoidal mirror 73 is reflected by the ellipsoidal mirror 73, travels towards the recessed mirror 74 while being focused, and enters the object 60. The illumination light L10 that enters the recessed mirror 74 and is reflected enters the object 60.

[0111] The ellipsoidal mirror 73 focuses the illumination light L10 onto the object 60. The inspection optical system 70 is positioned so that when the illumination light L10 illuminates the object 60, the image of the light source 71 is projected onto the upper surface 63 of the object 60. Therefore, the inspection optical system 70 provides critical illumination. In this way, the inspection optical system 70 illuminates the object 60 using critical illumination provided by the illumination light L10 generated by the light source 71.

[0112] The object 60 is placed on the stage 51. The illumination light L10 may be incident on the object 60 at an oblique angle as oblique incidence illumination. This allows for bright-field observation. Alternatively, the illumination light L10 may be incident from a direction perpendicular to the upper surface 63 of the object 60. This allows for dark-field observation. The light L20 reflected by the object 60 from the illumination light L10 enters the perforated concave mirror 81. The light L20 may include reflected light, scattered light, diffracted light, and photoluminescent light. A hole 81a is provided in the center of the perforated concave mirror 81.

[0113] Light L20 reflected by the perforated concave mirror 81 enters the convex mirror 82. The convex mirror 82 reflects the light L20 that entered from the perforated concave mirror 81 toward the hole 81a of the perforated concave mirror 81. The light L20 that passes through the hole 71a is detected by the detector 83. In this way, the imaging optical system 80 collects the light L20 from the object 60 illuminated by the illumination light L10, and the collected light L20 is detected by the detector 83. The light L20 contains information such as defects in the object 60. With this configuration, the inspection device 2 can inspect the object 60 for defects and contamination.

[0114] Once the object 60 is loaded onto the stage 51 of the inspection device, as described in Embodiments 1 to 5, the processing unit 40 obtains the focus height of the object 60, which is the EUV mask 61, at multiple measurement positions by illumination with light L1. Subsequently, the object 60, which is the EUV mask 61, is inspected with illumination light L10. Light L1 and illumination light L10 may be light of different wavelengths. Light L1 is, for example, visible light. Illumination light L10 includes, for example, EUV light.

[0115] The imaging optical system 80 is adjusted so that when the upper surface 63 of the EUV mask 61, which is the object 60, is at a reference height, the light L20 is properly focused on the detector 83. Based on the focus height information acquired by the processing unit 40, the scanning unit 50 adjusts the height position z for each of the multiple inspection target areas on the upper surface 63 of the EUV mask 61, which is the object 60, so that illumination light L10 is properly irradiated onto each area and the light L20 is properly focused on the detector 83. As a result, the light L20 resulting from the illumination light L10 irradiating each inspection target area is properly focused on the detector 83. This allows the detector 83 to acquire properly focused images for each inspection target area.

[0116] According to this embodiment, a focusing height can be obtained even with the EUV mask 61 with the pellicle 62, so the illumination light L10 can be easily focused when inspecting the EUV mask 61 with the pellicle 62. This improves inspection accuracy.

[0117] As described above, the optical device 1 may also be a review device or an exposure device. The same functions and effects as described above apply when the optical device 1 is a review device or an exposure device. When the optical device 1 is a review device for the object 60, the scanning unit 50 adjusts the height position z for each of the multiple review target areas on the upper surface 63 of the EUV mask 61, which is the object 60, based on the focus height information acquired by the processing unit 40, so that illumination light L10 is appropriately irradiated onto each area and light L20 is appropriately focused on the detector 83. As a result, the light L20 resulting from the illumination light L10 irradiating each review target area is appropriately focused on the detector 83, and the detector 83 can acquire an appropriately focused image for each review target area.

[0118] If the optical device 1 is an exposure apparatus that performs a lithography process using an object 60 as a patterning device, the scanning unit 50 adjusts the height position z for each of the multiple transfer target regions on the upper surface 63 of the EUV mask 61, which is the object 60, based on the focusing height information acquired by the processing unit 40, so that illumination light L10 (which may also be exposure light L10) is appropriately irradiated onto each of the transfer target regions and light L20 is appropriately irradiated onto the pattern formation target. As a result, the light L20 resulting from the irradiation of each transfer target region with illumination light L10 is appropriately focused onto the pattern formation target, for example, a wafer coated with resist.

[0119] While embodiments of the present disclosure have been described above, the disclosure includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the above embodiments. Furthermore, the configurations in embodiments 1 to 6 may be combined as appropriate. [Explanation of Symbols]

[0120] 1 Optical device 10 Illumination optical system 11 Light source 20 Lighting Control Unit 30 detectors 40 Processing Unit 50 Scanning Unit 51 stages 52 cabinets 60 Objects 61 EUV Mask 62 Pellicle 63 Top surface 64 frames 70 Inspection Optical System 71 Light source 72 Collector Mirror 73 Ellipsoidal mirror 74 Recessed Mirror 80 Imaging Optical System 81. Perforated concave mirror 81a Hole 82 Convex mirror 83 detectors A1 1st area A2 2nd area B1 Peripheral Region B2 central area L1 light L2 reflected light L10 illumination light L20 light P pattern

Claims

1. An optical device for acquiring the focus height at multiple positions on the surface of a pellicle-attached mask on which a pattern is formed, An illumination optical system that illuminates the aforementioned surface with light, A detector for detecting reflected light reflected from the surface, A lighting control unit that controls the output of the aforementioned light, A processing unit that acquires the focus height of a measurement position from among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with light, Equipped with, The surface includes a first region not covered by the pellicle and a second region covered by the pellicle. The detector is When the first region is illuminated by the light of the first output, the reflected light of a predetermined intensity or greater is detected. When the second region is illuminated by the light of the first output, the reflected light of a predetermined intensity or higher is not detected. If the second region is illuminated with the light of the second output which is greater than the first output, the reflected light of the predetermined intensity or greater is detected. When the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or greater, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light. The lighting control unit illuminates the surface included in the second region with the light of the second output. optical equipment.

2. The system further comprises a scanning unit that changes the relative position of the mask and the illumination position of the light relative to the mask, The illumination control unit illuminates the measurement position with the light of the first output when the surface included in the second region of the mask is designated as the measurement position for the first time after the mask has been loaded, and illuminates the measurement position with the light of the second output when the detector does not detect reflected light of a predetermined intensity or higher. The optical apparatus according to claim 1.

3. An optical device for acquiring the focus height at multiple positions on the surface on which a mask pattern is formed, An illumination optical system that illuminates the aforementioned surface with light, A detector for detecting reflected light reflected from the surface, A lighting control unit that controls the output of the aforementioned light, A processing unit that acquires the focus height of a measurement position from among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with light, A scanning unit that changes the relative position of the mask and the position of light illumination relative to the mask, Equipped with, When the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or higher, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light. The surface includes a peripheral region and a central region. The illumination control unit illuminates the measurement position with the first output of light when the surface included in the central region of the mask is designated as the measurement position for the first time after the mask has been loaded, and illuminates the measurement position with the second output of light which is greater than the first output when the detector does not detect reflected light of a predetermined intensity or greater. optical equipment.

4. The illumination control unit illuminates the surface included in the peripheral region with the light of the first output, after the mask has been loaded and before the surface included in the central region is designated as the measurement position, The processing unit acquires the focus height of the measurement position, After that, The aforementioned lighting control unit, The surface included in the central region is illuminated with the light of the first output as the measurement position. If the detector does not detect reflected light with a value equal to or greater than the predetermined intensity, the measurement position is illuminated with the light from the second output. The processing unit obtains the focus height of the measurement position belonging to the central region based on the detection result in which the detector detects reflected light of a predetermined intensity or higher. The optical apparatus according to claim 3.

5. If, after obtaining the focus height of the measurement position belonging to the central region, the focus height of the measurement position belonging to the peripheral region is obtained, The lighting control unit illuminates the measurement position belonging to the peripheral region with the light of the second output. The optical apparatus according to claim 3 or 4.

6. The peripheral region includes a first peripheral region, a second peripheral region, a third peripheral region, and a fourth peripheral region, which surround the central region on all four sides and have different directions when viewed from the central region. After the mask is loaded and before the surface included in the central region is designated as the measurement position, the illumination control unit illuminates the surface included in the first peripheral region, the surface included in the second peripheral region, the surface included in the third peripheral region, and the surface included in the fourth peripheral region with the light of the first output, each of these surfaces as the measurement position. Subsequently, the surface included in the central region is illuminated with the light of the first output, with the measurement position being used. The optical apparatus according to claim 4.

7. The peripheral region includes a first peripheral region and a second peripheral region that is opposite to the first peripheral region, with the central region in between. The illumination control unit illuminates the surface included in the first peripheral region and the surface included in the second peripheral region with the light of the first output, after the mask has been loaded and before the surface included in the central region is designated as the measurement position, and thereafter illuminates the surface included in the central region with the light of the first output, with the surface included in the central region being designated as the measurement position. The processing unit restricts the acquisition of the focus height for the central region during the process in which the measurement position changes from the surface included in the first peripheral region to the surface included in the second peripheral region. The optical apparatus according to claim 4.

8. The processing unit determines whether the pellicle is torn based on the difference in detection results when the first region and the second region are illuminated with light of substantially equal output, including at least one of the first output or the second output. The optical apparatus according to claim 1.

9. The processing unit determines whether the pellicle covering the surface of the mask is torn based on the difference in detection results when the peripheral region and the central region are illuminated with light of substantially equal output, including at least one of the first output or the second output. The optical apparatus according to claim 3.

10. The processing unit determines that the pellicle is torn when the difference is less than or equal to a threshold. The optical apparatus according to claim 8 or 9.

11. The threshold is set based on the transmittance of the pellicle. The optical apparatus according to claim 10.

12. A control method for an optical device that acquires the focus height at multiple positions on the surface of a mask with a pellicle on which a pattern is formed, The steps include illuminating the surface with light using an illumination optical system, The steps include controlling the output of the light using a lighting control unit, The steps include detecting the reflected light reflected from the surface using a detector, The processing unit performs the steps of obtaining the focus height of a measurement position from among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with the light, Equipped with, The surface includes a first region not covered by the pellicle and a second region covered by the pellicle. In the step of detecting the reflected light, The detector is When the first region is illuminated by the light of the first output, the reflected light of a predetermined intensity or greater is detected. When the second region is illuminated by the light of the first output, the reflected light of a predetermined intensity or higher is not detected. If the second region is illuminated with the light of the second output which is greater than the first output, the reflected light of the predetermined intensity or greater is detected. In the step of obtaining the focus height, When the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or greater, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light. In the step of controlling the output of the light, The lighting control unit illuminates the surface included in the second region with the light of the second output. A method for controlling optical devices.

13. The scanning unit further includes a step of changing the relative position of the mask and the position of light illumination relative to the mask, In the step of controlling the output of the light, The illumination control unit illuminates the measurement position with the light of the first output when the surface included in the second region of the mask is designated as the measurement position for the first time after the mask has been loaded, and illuminates the measurement position with the light of the second output when the detector does not detect reflected light of a predetermined intensity or higher. A method for controlling an optical device according to claim 12.

14. A control method for an optical device that acquires the focus height at multiple positions on the surface on which a mask pattern is formed, The steps include illuminating the surface with light using an illumination optical system, The steps include detecting the reflected light reflected from the surface using a detector, The steps include controlling the output of the light using a lighting control unit, The processing unit performs the steps of obtaining the focus height of a measurement position from among the plurality of positions on the surface, based on the detection result of the detector when the measurement position to be measured is illuminated with the light, The scanning unit performs a step of changing the relative position of the mask and the position of light illumination relative to the mask. Equipped with, In the step of obtaining the focus height, When the measurement position is illuminated and the detector detects reflected light of a predetermined intensity or higher, the processing unit obtains the focus height of the measurement position based on the detection result of the detected reflected light. The surface includes a peripheral region and a central region. In the step of controlling the output of the light, The illumination control unit illuminates the measurement position with the first output of light when the surface included in the central region of the mask is designated as the measurement position for the first time after the mask has been loaded, and illuminates the measurement position with the second output of light which is greater than the first output when the detector does not detect reflected light of a predetermined intensity or greater. A method for controlling optical devices.

15. In the step of controlling the output of the light, The illumination control unit illuminates the surface included in the peripheral region with the light of the first output, after the mask has been loaded and before the surface included in the central region is designated as the measurement position, In the step of obtaining the focus height, The processing unit acquires the focus height of the measurement position, After that, In the step of controlling the output of the light, The aforementioned lighting control unit, The surface included in the central region is illuminated with the light of the first output as the measurement position. If the detector does not detect reflected light with a value equal to or greater than the predetermined intensity, the measurement position is illuminated with the light from the second output. In the step of obtaining the focus height, The processing unit obtains the focus height of the measurement position belonging to the central region based on the detection result in which the detector detects reflected light of a predetermined intensity or higher. A method for controlling an optical device according to claim 14.

16. In the step of obtaining the focus height, After obtaining the focus height of the measurement position belonging to the central region, the focus height of the measurement position belonging to the peripheral region is obtained. In the step of controlling the output of the light, The lighting control unit illuminates the measurement position belonging to the peripheral region with the light of the second output. A method for controlling an optical device according to claim 14 or 15.

17. The peripheral region includes a first peripheral region, a second peripheral region, a third peripheral region, and a fourth peripheral region, which surround the central region on all four sides and have different directions when viewed from the central region. In the step of controlling the output of the light, After the mask is loaded and before the surface included in the central region is designated as the measurement position, the illumination control unit illuminates the surface included in the first peripheral region, the surface included in the second peripheral region, the surface included in the third peripheral region, and the surface included in the fourth peripheral region with the light of the first output, each of these surfaces as the measurement position. Subsequently, the surface included in the central region is illuminated with the light of the first output, with the measurement position being used. A method for controlling an optical device according to claim 15.

18. The peripheral region includes a first peripheral region and a second peripheral region that is opposite to the first peripheral region, with the central region in between. In the step of controlling the output of the light, The illumination control unit illuminates the surface included in the first peripheral region and the surface included in the second peripheral region with the light of the first output, after the mask has been loaded and before the surface included in the central region is designated as the measurement position, and thereafter illuminates the surface included in the central region with the light of the first output, with the surface included in the central region being designated as the measurement position. In the step of obtaining the focus height, The processing unit restricts the acquisition of the focus height for the central region during the process in which the measurement position changes from the surface included in the first peripheral region to the surface included in the second peripheral region. A method for controlling an optical device according to claim 15.

19. The processing unit further comprises the step of determining whether the pellicle is torn based on the difference in detection results when the first region and the second region are illuminated with light of substantially equal output including at least one of the first output or the second output. A method for controlling an optical device according to claim 12.

20. The processing unit further comprises the step of determining whether the pellicle covering the surface of the mask is torn based on the difference in detection results when the peripheral region and the central region are illuminated with light of substantially equal output including at least one of the first output or the second output. A method for controlling an optical device according to claim 14.

21. The processing unit further includes a step of determining whether the pellicle is torn if the difference is less than or equal to a threshold. A method for controlling an optical device according to claim 19 or 20.

22. The threshold is set based on the transmittance of the pellicle. A method for controlling an optical device according to claim 21.

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