Optical apparatuses, related lithographic apparatus or a lithographic system, and methods of forming a pattern on a target region of a substrate

Abstract

This invention provides a device for regulating and guiding a radiation beam, comprising a first optical assembly and an energy sensor. The first optical assembly includes a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source. The two-dimensional array of independently movable reflective optical elements includes: a first set configured to guide a first portion of the received radiation to the energy sensor; and a second set configured to guide a second portion of the received radiation to an illumination area. The number of reflective optical elements in the first set is such that the energy of the first portion of the radiation is less than 4% of the total energy of the first and second portions. The reflective optical elements in the first set are uniformly distributed within the first optical assembly.

Description

[Technical Field]

[0001] This invention relates to an apparatus for adjusting, guiding, and monitoring radiation beams. The apparatus can form part of a lithography apparatus, for example, at least some parts of an illumination system within the apparatus that can form part of a lithography apparatus. The apparatus is suitable for receiving and guiding extreme ultraviolet (EUV) radiation. This invention also relates to corresponding methods for adjusting, guiding, and monitoring radiation beams. These methods can form part of a lithography process and / or part of a method for forming patterns on a target area of ​​a substrate. [Previous Technology]

[0002] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. Lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can, for example, project a pattern at a patterning device (e.g., a mask) onto a radiation-sensitive material (resist) layer disposed on a substrate.

[0003] To project a pattern onto a substrate, a lithography apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to a lithography apparatus using radiation with a wavelength of, for example, 193 nm, a lithography apparatus using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4-20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0004] It is desirable to provide control over various properties of a radiation beam used in a lithography apparatus to project a pattern onto a substrate. For example, it is desirable to monitor the energy of the radiation beam to allow control over the dose of radiation delivered to the substrate. Furthermore, it is desirable to provide control over the shape (i.e., spatial distribution) of the radiation beam in the plane of the patterning apparatus. Additionally, it is desirable to provide control over the angular distribution of the radiation beam in the plane of the patterning apparatus. The angular distribution of the radiation beam in the plane of the patterning apparatus may be referred to as the illumination pattern, which may be selected based on the imaging pattern to increase the image contrast on the substrate.

[0005] It may be desirable to provide new alternative devices and / or methods for modulating, guiding and monitoring radiation beams (e.g., in lithography equipment) that at least partially address one or more of the problems associated with prior art configurations, whether identified herein or otherwise. [Summary of the Invention]

[0006] According to a first aspect of the present invention, an apparatus is provided, comprising: a first optical component including a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source; and a sensor operable to determine the intensity of the received radiation; wherein the two-dimensional array of independently movable reflective optical elements includes: a first set of reflective optical elements configured to guide a first portion of the radiation received by the first set to the sensor; and a second set of reflective optical elements configured to guide a second portion of the radiation received by the second set to an illumination area; and wherein the number of reflective optical elements in the first set is such that the energy of the first portion of the radiation is less than 4% of the total energy of the first and second portions of the radiation.

[0007] The first optical component may form part of the illumination system of the lithography apparatus. The apparatus may be adapted to receive and guide extreme ultraviolet (EUV) radiation. For example, the first optical component may form a field-faceted mirror device of the illumination system of the lithography apparatus. In use, a patterning device (e.g., a magnifying mask or shield) may be placed in the illumination area. For example, during scanning lithography exposure, the patterning device may move through the illumination area. The image of the patterning device may be formed on a target area of ​​the substrate using a second portion of the radiation (e.g., using projection optics).

[0008] In principle, the equipment can be modified to fit an existing lithography system.

[0009] The device according to the first state allows a second portion of the radiation to be used to project a pattern onto a target portion of the substrate, while simultaneously allowing the intensity or energy of the first portion of the radiation to be measured using a sensor. The intensity or energy of the second portion of the radiation can be determined from the measured intensity or energy of the first portion of the radiation, which allows for accurate control of the radiation dose delivered to the target portion of the substrate. The device according to the first state is advantageous because it allows for this accurate dose control while reducing the amount of radiation used for intensity or energy measurement (and thus increasing the amount of radiation used for exposure) compared to existing configurations.

[0010] In some embodiments, the number of reflective optical elements in the first set may be such that the energy of the first portion of radiation is less than 2.5% of the total energy of the first and second portions of radiation. In some embodiments, the number of reflective optical elements in the first set may be such that the energy of the first portion of radiation is less than 1% of the total energy of the first and second portions of radiation. In some embodiments, the number of reflective optical elements in the first set may be such that the energy of the first portion of radiation is less than 0.5% of the total energy of the first and second portions of radiation. In some embodiments, the number of reflective optical elements in the first set may be such that the energy of the first portion of radiation is approximately 0.1% of the total energy of the first and second portions of radiation.

[0011] The embodiment provides a significant improvement over existing lithography illumination systems, which can direct between 5% and 10% of the total radiation to the energy sensor. In part, this reduction in the amount of radiation used for energy measurement is a result of using a two-dimensional array of independently movable reflective optics.

[0012] Furthermore, this reduction in the amount of EUV radiation directed to the sensor is feasible with current sensor technology. Currently, a mask-level EUV energy sensor may include a filter for filtering out any out-of-band radiation. The filter may also include an element (made of aluminum) configured to reduce the intensity of EUV radiation to within the dynamic range of the photosensitive portion of the sensor. Currently, this EUV radiation attenuation is approximately 100 times, for example, from 10% to 0.1%. Therefore, by adjusting the filter stack in the energy sensor to reduce the thickness of the EUV blocking element (or completely removing the stack), it would be feasible to measure using 0.1% of the radiation received by the device.

[0013] It is estimated that approximately 0.1% of the EUV radiation beam can be used to achieve adequate energy measurements. This is 50 times smaller than that currently used in EUV lithography scanners. One advantage of directing this lower intensity of radiation to the energy sensor is that it reduces secondary electron emissions from such sensors, resulting in improved (linear) performance. Together with reduced filter stacking and optimized electronics and gain settings, the extremely low EUV intensity level can be sufficient while still ensuring measurement accuracy.

[0014] Advantageously, this significant high-power gain (approximately 5% of the EUV radiation power) in the second portion of the radiation used for exposure is expected to cause a significant gain in delivery. It is also estimated that the first-state sample will cause improvements in dose control and thus in critical size uniformity.

[0015] In some embodiments, the number of reflective optical elements in the first set can be optimized to minimize the amount of radiation received by the first set of reflective optical elements, while allowing the total intensity of radiation received by the second set of reflective optical elements to be determined with the desired accuracy.

[0016] According to a second aspect of the present invention, an apparatus is provided, comprising: a first optical component including a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source; and a sensor operable to determine an intensity of the received radiation; wherein the two-dimensional array of independently movable reflective optical elements includes: a first set of reflective optical elements configured to guide a first portion of radiation received by the first set to the sensor; and a second set of reflective optical elements configured to guide a second portion of radiation received by the second set to an illumination area, such that the radiation from the second set of reflective optical elements overlaps in the illumination area to substantially cover the illumination area a first number of times; and wherein the number of reflective optical elements in the first set is equal to or greater than the first number.

[0017] It should be understood that the second state sample can be combined with the first state sample. For example, the number of one of the reflective optical elements in the first set can be such that the energy of the first portion of radiation is less than 4% of the total energy of the first and second portions of radiation.

[0018] A second set of reflective optical elements is configured to guide a second portion of radiation to the illumination area such that radiation from the second set of reflective optical elements overlaps at the illumination area to substantially cover the illumination area a first number of times. For example, a two-dimensional array of independently movable reflective optical elements may comprise a first number of groups, each of which substantially covers the illumination area and contributes to the second set of reflective optical elements. Each group may comprise clusters of adjacent reflective optical elements. The device according to the second configuration ensures that at least one reflective optical element from each of these groups contributes to the guidance to the first set of sensors. This ensures that sampling in the measurement of the energy or intensity of the radiation contributes to the radiation dose delivered to the illumination area, and this ensures that the measurement of the energy or intensity of the first portion of the radiation is an accurate estimate of the energy or intensity of the second portion of the radiation.

[0019] In some embodiments, the number of reflective optical elements in the first set may be an integer multiple of the first number. For example, in some embodiments, and the integer number (e.g., 1, 2, 3...) of reflective optical elements from each of these groups helps to direct a first portion of the radiation to the first set of sensors.

[0020] According to a third aspect of the present invention, an apparatus is provided, comprising: a first optical component including a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source; and a sensor operable to determine an intensity of the received radiation; wherein the two-dimensional array of independently movable reflective optical elements includes: a first set of reflective optical elements configured to guide a first portion of the radiation received by the first set to the sensor; and a second set of reflective optical elements configured to guide a second portion of the radiation received by the second set to an illumination area; and wherein the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical component.

[0021] It should be understood that the third state sample can be combined with the first and second state samples. For example, the number of one of the reflective optical elements in the first set can be such that the energy of the first portion of radiation is less than 4% of the total energy of the first and second portions of radiation.

[0022] Advantageously, since the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical assembly, the sampling of the radiation beam at the first optical assembly can be improved relative to the sampling provided by the energy sensor and field-faceted mirror of the existing lithography illumination system. These existing lithography illumination systems only sample the area of ​​the field-faceted mirror that is not used for substrate exposure. In contrast, the device according to the third state sample can be configured to sample the area of ​​the field-faceted mirror that is not used for substrate exposure but is surrounded by reflective optical elements and is a (smaller) area used for substrate exposure. Therefore, the device according to the third state sample can provide a more accurate determination of the energy of the radiation used for exposure, and / or provide information on the variation of the energy of the radiation across the illumination area.

[0023] Each position in the illumination area can receive radiation from a plurality of reflective optical elements in the second set of reflective optical elements.

[0024] The illumination area may be referred to as an illumination field or an object field. The first optical assembly may contain approximately 100,000 independently movable reflective optical elements. Each location in the illumination area may receive radiation from approximately 100 independently movable reflective optical elements.

[0025] The two-dimensional array of independently movable reflective optical elements may comprise a plurality of groups. Each group may comprise a plurality of adjacent independently movable reflective optical elements, and the plurality of adjacent independently movable reflective optical elements may comprise: a first subgroup of reflective optical elements configured to guide radiation received by the first subgroup to the sensor; and a second subgroup of reflective optical elements configured to guide radiation received by the second subgroup to the illumination area.

[0026] Each of the plurality of groups of reflective optical elements may be referred to as a cluster of reflective optical elements.

[0027] The radiation directed to the illumination area by the second subgroup of different groups of reflective optical elements may spatially overlap in the illumination area.

[0028] Each of the plurality of subgroups may be referred to as a field-faceted mirror or a virtual field-faceted mirror. There may be approximately 100 (e.g., 300) groups of independently movable reflective optical elements. Each group may contain approximately 1000 independently movable reflective optical elements. For example, in one embodiment, each group may contain 10 columns of independently movable reflective optical elements, each column having 100 independently movable reflective optical elements. A first subgroup of each group may contain approximately one reflective optical element. The remaining independently movable reflective optical elements in each group may form a second subgroup.

[0029] In some embodiments, a plurality of adjacent, independently movable reflective optical elements in each group may substantially cover a continuous area of ​​the first optical assembly. It should be understood that this may mean that any gap between adjacent reflective optical elements may be minimal.

[0030] The shape of a continuous region of a first optical component covered by a plurality of adjacent independently movable reflective optical elements in a group of independently movable reflective optical elements may be referred to as the shape of the group of independently movable reflective optical elements. The shape of each of the group of independently movable reflective optical elements may substantially correspond to the shape of the illumination area.

[0031] Each of the plurality of groups of independently movable reflective optical elements may have substantially the same size and shape.

[0032] In some embodiments, the shape of each of the plurality of groups may be curved. In some embodiments, the shape of each of the plurality of groups may be generally rectangular.

[0033] In some embodiments, a plurality of groups of movable reflective optical elements may substantially cover the area of ​​the first optical component that receives radiation during use. It should be understood that this may mean that any gaps between adjacent groups of reflective optical elements within the area of ​​the first optical component that receives radiation during use can be minimized.

[0034] The first subgroup of reflective optical elements from different groups of reflective optical elements may be placed in different positions within the groups.

[0035] For example, in an embodiment where each group of independently movable reflective optical elements is arranged in multiple columns and rows, a first subgroup of reflective optical elements from any two different groups (which is configured to direct radiation received from the radiation source to the sensor) may be arranged in different columns and / or rows within its group.

[0036] Advantageously, this configuration reduces the effect of directing a subset of independently movable reflective optical elements from each group toward the sensor. By removing the elements of the first subset from different parts of the group, different areas of the illumination zone are affected. Furthermore, ensuring that the first subgroups of reflective optical elements from different groups of reflective optical elements are positioned at different locations within the group allows for determination of intensity variations within the illumination zone and / or allows for sampling or measurement of the slit profile. As used herein, the illumination zone may also be referred to as an illumination slit or a gap. Additionally, as used herein, the spatial intensity distribution of radiation across the illumination zone may be referred to as a slit profile. Particularly advantageously, the elements of the first subset from all groups coincide with the positions distributed within the illumination zone in the non-scanning direction of the device.

[0037] The device may further include a second optical component configured to receive radiation and guide it to the illumination area by the second set of self-reflective optical elements.

[0038] The second optical component can be configured to form an image of one of the second subgroups of each of the plurality of groups in the illumination area, all such images spatially overlapping in the illumination area.

[0039] The second optical component may include a plurality of optical elements disposed at different positions along the optical axis of the device.

[0040] The second optical component may be a faceted mirror containing one of a plurality of facets.

[0041] The second optical component may form part of the illumination system of the lithography device. For example, the second optical component may form the pupil surface of the illumination system of the lithography device.

[0042] In use, the first optical component and the second optical component can be configured together to adjust the radiation beam before it is incident on the patterning device placed in the illumination area. The first optical component and the second optical component can together provide the radiation beam with the desired cross-sectional shape and the desired spatial and angular distribution. In addition to the first optical component and the second optical component, the illumination system may include other mirrors or devices.

[0043] The sensor may be mounted on or connected to the second optical component.

[0044] That is, the sensor can be placed on the pupil surface mirror inside the lighting system of the lithography device.

[0045] Each of these independently movable reflective optical elements may include a microelectromechanical system (MEMS) micromirror.

[0046] Therefore, the first optical component can be considered as containing a MEMS micro-mirror array.

[0047] The device may further include a controller operable to control a position and / or orientation of each of the independently movable reflective optical elements.

[0048] Therefore, the controller can be operated to configure the orientation of the independently movable reflective optical element so as to guide a portion of the received radiation to the sensor and another portion of the received radiation to the illumination area.

[0049] Therefore, the controller can be operated to configure the orientation of the independently movable reflective optical element so as to guide a portion of the received radiation to the sensor and another portion of the received radiation to the illumination area.

[0050] The sensor is operable to determine the intensity of the radiation received thereon. Specifically, the sensor is operable to determine the intensity of radiation directed onto the first set of reflective optical elements. The sensor is operable to output a signal indicating the intensity of the radiation received thereon. This signal can be received by the controller.

[0051] It should be understood that the sensor may use any available photosensitive technology. For example, the sensor may include one or more of the following: photodiode, complementary metal-oxide-semiconductor (CMOS) and / or charge-coupled device (CCD).

[0052] The controller is operable to periodically and temporarily control the position and / or orientation of one of the independently movable reflective optical elements in order to position it in a second configuration.

[0053] For example, during exposure of a target area of ​​a substrate, the controller may be operable to control the reflective optical elements to position them in a first configuration. The first configuration may be referred to as the exposure configuration. In the first configuration, the controller may position the reflective optical elements such that: (a) the energy of a first portion of the radiation is less than a threshold percentage of the total energy of the first and second portions of the radiation (as in the first configuration); (b) the amount of radiation received by the first set of reflective optical elements is minimized, while allowing the total intensity of radiation received by the second set of reflective optical elements to be determined with a certain accuracy (as in the second configuration); and / or (c) the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical assembly (as in the third configuration).

[0054] When the independently movable reflective optical elements are in the second configuration, one of the radiated first portions of energy may be greater than the energy when the independently movable reflective optical elements are in the first configuration.

[0055] For example, more accurate and / or detailed measurements of the energy of radiation and / or the spatial distribution of radiation in the exposure area can be achieved by placing independently movable reflective optical elements in the second configuration. This is achieved by increasing the number of reflective optical elements in the first set. Independently movable reflective optical elements can be placed in the second configuration for this purpose when the equipment does not expose the target area of ​​the substrate to radiation. That is, this can be done outside of standard batch exposures in the lithography equipment (e.g., during mask replacement, wafer replacement, or between exposures of different target areas).

[0056] Additionally, independently movable reflective optical elements can be placed in a second configuration during the initial system setup and / or calibration of the device.

[0057] The sensor may include an array of sensing elements. Each sensing element may be configured to receive radiation from a location on the first optical assembly corresponding to a different location within the illumination area.

[0058] For example, each sensing element may be configured to receive radiation from a different location within one of a group of independently movable reflective optical elements.

[0059] The array of sensing elements can be a one-dimensional or two-dimensional array.

[0060] Advantageously, this allows for the measurement of slit uniformity and its offset within the illumination area. This avoids the need for wafer-level slit scanning. Furthermore, it enables combined reproducibility and slit uniformity correction and allows for monitoring of imaging performance at a much higher frequency than currently possible via wafer-level slit scanning. Consequently, this can result in a significant improvement in performance and also in improved throughput gain.

[0061] The device may further include a radiation source operable to generate a pulsed radiation beam and supply the pulsed radiation beam to the first optical component.

[0062] The radiation beam may include EUV radiation. The radiation source may be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free electron laser (FEL) or any other radiation source capable of generating EUV radiation.

[0063] One pulse of the pulsed radiation beam may be generated by the radiation source depending on an intensity determined by the sensor when a portion of a previous pulse of radiation is received.

[0064] For example, the sensor can determine the energy of the radiation beam pulse by pulse, and this energy can be used as part of a feedback loop to stabilize the energy of the radiation beam.

[0065] One of the pulses of the pulsed radiation beam may be generated by the radiation source depending on the spatial intensity information determined by the sensor when a portion of a previous pulse of radiation is received.

[0066] That is, the device can feed back the slit profile information determined by the sensor array for each pulse to the radiation source. Specifically, this data not only provides intensity information to ensure dose reproducibility, but also provides information on slit uniformity and far-field stability. For LPP sources, this information will allow the radiation source to optimize the laser beam and stabilize it with small droplet alignment, thereby further improving slit uniformity and far-field stability.

[0067] The sensor is operable to quantify an alignment between the first optical component and one of the radiation beams received therefrom.

[0068] The device may further include a support structure configured to support a patterning device such that the patterning device is placed in the illumination area or movable through the illumination area, and wherein the sensor is accessible to the support structure for placement.

[0069] That is, the sensor can be provided at the photomask level.

[0070] The device may further include: a substrate stage configured to support a substrate; and a projection system including imaging optics configured to receive radiation from the illumination area and form an image of an object disposed in the illumination area on a substrate supported by the substrate stage.

[0071] For example, an object may include a patterning device supported by a support structure. A radiation beam may interact with the patterning device to generate a patterned radiation beam. A projection system is configured to project the patterned radiation beam onto a substrate. For that purpose, an imaging optics may include a plurality of mirrors configured to project the patterned radiation beam onto a substrate held by a substrate stage.

[0072] The sensor can be placed between the imaging optics and the substrate stage.

[0073] That is, the sensor can be disposed at the substrate or wafer level. For example, the sensor can be disposed close to the dynamic airlock between the optics of the projection system and the substrate. With this configuration, the sensor can be operated to measure the intensity and uniformity of the radiation beam behind the entire optical column (illumination system and projection system). This will enable additional real-time and highly accurate system transmission measurements and dose reproducibility correction.

[0074] Improvements in system transmission measurement and / or monitoring can lead to more accurate diagnostics, thereby reducing unscheduled downtime and increasing the availability of lithography equipment.

[0075] According to a fourth embodiment of the present invention, a lithography device or lithography system is provided, which includes any of the devices of the first, second or third embodiments of the present invention.

[0076] According to a fifth aspect of the present invention, a method for forming a pattern on a target area of ​​a substrate is provided. The method includes: generating a radiation beam; guiding the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array comprising a first set of reflective optical elements and a second set of reflective optical elements; guiding a first portion of the radiation beam to a sensor using the first set of reflective optical elements and determining the intensity of the first portion of the radiation beam using the sensor; and guiding a second portion of the radiation beam to a magnifying glass using the second set of reflective optical elements to impart a pattern to the second portion of the radiation beam and form a patterned radiation beam; and projecting the patterned radiation beam onto the target area of ​​a substrate; wherein the energy of the first portion of the radiation is less than 4% of the total energy of the first and second portions of the radiation.

[0077] The method according to the fifth state sample can be implemented using the equipment according to the first state sample.

[0078] According to a sixth aspect of the present invention, a method for forming a pattern on a target area of ​​a substrate is provided, the method comprising: generating a radiation beam; guiding the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array comprising a first set of reflective optical elements and a second set of reflective optical elements; guiding a first portion of the radiation beam to a sensor using the first set of reflective optical elements and determining the intensity of the first portion of the radiation beam using the sensor; and guiding a second portion of the radiation beam to a magnifying glass using the second set of reflective optical elements to impart a pattern to the second portion of the radiation beam and form a patterned radiation beam; and projecting the patterned radiation beam onto the target area of ​​a substrate; wherein the second portion comprises a plurality of spatial overlap contributions each originating from a group of adjacent reflective optical elements; and wherein the first set comprises one or more reflective optical elements from each of the plurality of groups.

[0079] The method according to the sixth state sample can be implemented using the equipment according to the second state sample.

[0080] The first set may contain an integer number of reflective optical elements from each of the plurality of groups.

[0081] It may be necessary to minimize the integers. For example, the integers can be small integers, such as 1, 2, or 3.

[0082] According to a seventh aspect of the present invention, a method for forming a pattern on a target area of ​​a substrate is provided. The method includes: generating a radiation beam; guiding the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array comprising a first set of reflective optical elements and a second set of reflective optical elements; guiding a first portion of the radiation beam to a sensor using the first set of reflective optical elements and determining the intensity of the first portion of the radiation beam using the sensor; and guiding a second portion of the radiation beam to a magnifying glass using the second set of reflective optical elements to impart a pattern to the second portion of the radiation beam and form a patterned radiation beam; and projecting the patterned radiation beam onto the target area of ​​a substrate; wherein the first portion is formed by a plurality of samples of the radiation beam uniformly distributed within the radiation beam.

[0083] The method according to the seventh state sample can be implemented using the equipment according to the third state sample.

[0084] The method of any of the fifth, sixth or seventh states may further include using the sensor to determine one spatial distribution of the radiation beam at the patterning device.

[0085] The method of any of the fifth, sixth or seventh states may include forming a pattern sequentially on a plurality of target areas of one or more substrates.

[0086] The method may further include a more accurate and / or more detailed measurement of the energy of the radiation beam and / or a spatial distribution of the radiation beam at the patterning device, periodically determining between exposures of different target areas.

[0087] The radiation beam is a pulsed radiation beam, and one pulse of the pulsed radiation beam can be generated depending on an intensity determined by the sensor when a portion of a previous pulse of radiation is received.

[0088] One pulse of the pulsed radiation beam can be generated based on spatial intensity information determined by the sensor when a portion of a previous pulse of radiation is received.

Implementation Method

[0090] Figure 1 illustrates a lithography system including a radiation source SO and a lithography device LA. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography device LA. The lithography device LA includes an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate stage WT configured to support a substrate W.

[0091] The illumination system IL is configured to adjust the EUV radiation beam B before it is incident on the patterning device MA. Additionally, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and the faceted pupil mirror device 11 together provide the desired cross-sectional shape and desired intensity distribution to the EUV radiation beam B. In addition to or in lieu of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may include other mirrors or devices.

[0092] After such adjustment, the EUV radiation beam B interacts with the patterning device MA. Due to this interaction, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. For that purpose, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate stage WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thus forming an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated in FIG. 1 as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0093] The substrate W may include a previously formed pattern. In this case, the lithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0094] A relative vacuum, i.e. a small amount of gas (e.g., hydrogen) at a pressure sufficiently below atmospheric pressure, may be provided in the radiation source SO, the lighting system IL and / or the projection system PS.

[0095] The radiation source SO shown in Figure 1 is of the type that may be called a laser-generated plasma (LPP) source, for example. A laser system 1, which may include a CO2 laser, is configured to deposit energy via a laser beam 2 onto a fuel (such as tin (Sn)) supplied by, for example, a fuel emitter 3. Although tin is mentioned in the following description, any suitable material may be used. The fuel may be, for example, in liquid form and may be, for example, a metal or alloy. The fuel emitter 3 may include a nozzle configured to guide tin, for example, in the form of droplets, along a trajectory toward the plasma forming region 4. The laser beam 2 is incident on the tin at the plasma forming region 4. The deposition of laser energy into the tin generates tin plasma 7 at the plasma forming region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during the de-excitation and recombination of electrons and ions in the plasma.

[0096] EUV radiation from the plasma is collected and focused by collector 5. Collector 5 includes, for example, a near-normal incident radiation collector 5 (sometimes more commonly referred to as a normal incident radiation collector). Collector 5 may have a multi-layered mirror structure configured to reflect EUV radiation (e.g., EUV radiation with a desired wavelength such as 13.5 nm). Collector 5 may have an ellipsoidal configuration with two focal points. The first of the focal points may be located at the plasma formation region 4, and the second of the focal points may be located at the intermediate focal point 6, as discussed below.

[0097] The laser system 1 may be spatially separated from the radiation source SO. In this case, the laser beam 2 may be delivered from the laser system 1 to the radiation source SO by means of a beam delivery system (not shown) including, for example, suitable guide mirrors and / or beam expanders and / or other optical devices. The laser system 1, the radiation source SO and the beam delivery system may be considered together as a radiation system.

[0098] The radiation reflected by collector 5 forms an EUV radiation beam B. The EUV radiation beam B is focused at intermediate focal point 6 to form an image at intermediate focal point 6 of the plasma present in plasma formation region 4. The image at intermediate focal point 6 serves as a virtual radiation source for illumination system IL. Radiation source SO is configured such that intermediate focal point 6 is located at or near opening 8 in enclosure structure 9 of radiation source SO.

[0099] Although Figure 1 depicts the radiation source SO as a laser-generated plasma (LPP) source, any suitable source such as a discharge-generated plasma (DPP) source or a free electron laser (FEL) can be used to generate EUV radiation.

[0100] The faceted field mirror device 10 and the faceted pupil mirror device 11 are configured to provide the desired angular distribution of the radiation beam B at the patterning device MA, and to provide the desired uniformity of radiation intensity at the patterning device MA. The illumination system IL can be configured to provide Köhler illumination of the illumination area IR (through which the patterning device MA can move during exposure of the substrate W), such that the plasma at the plasma formation area 4 is defocused in the conjugate plane of the patterning device MA and the substrate W (and thus does not affect the properties of the radiation beam). As used herein, the illumination area IR may also be referred to as the illumination slit or slit.

[0101] In lithography, the illumination of the patterning device MA is extremely important. Specifically, it is desirable to control the angular distribution of radiation at the illuminated area IR of the patterning device MA exposed to radiation. This angular distribution of radiation is conveniently described by the spatial distribution of radiation in the illumination pupil plane, which describes how the light cone incident on each point of the patterning device MA is filled. In conventional illumination modes, radiation uniformly fills a circular area of ​​the illumination pupil plane centered on the optical axis, such that each point on the patterning device is illuminated by a solid light cone. In bipolar illumination modes, radiation fills two areas of the illumination pupil plane spaced apart from and on the opposite side of the optical axis. Many other illumination modes are known. In principle, an optimal illumination mode can be defined to image a given pattern under given conditions. Therefore, it is desirable to provide flexibility in the illumination mode.

[0102] The uniformity of illumination is also extremely important. The uniformity of illumination affects the uniformity of the dose exposed to the target portion of the substrate W, which in turn affects the critical dimensional uniformity (CDU), an important measurement of the uniformity of the dimensions of features formed on the substrate W. For example, it may be desirable to maintain a desired spatial intensity distribution of radiation across the illumination region IR. As used herein, the spatial intensity distribution of radiation across the illumination region IR may be referred to as the slit profile.

[0103] The collector 5 is generally in the form of a concave mirror, which is configured to direct radiation emitted from the plasma forming region 4 into the solid angle opposite the collector 5. This radiation is reflected and focused at the intermediate focal point 6. Therefore, within the housing, the radiation beam B generally has the form of a converging radiation cone that converges at the intermediate focal point 6, the outer edge of which is indicated by two lines in FIG. 1. Downstream of the intermediate focal point 6, the radiation beam B generally has the form of a diverging radiation cone incident on the generally circular field-faceted mirror device 10. However, the radiation source SO may include a shield that blocks a portion of this radiation cone so that a portion of the diverging radiation cone will not receive radiation from the collector 5. For example, the radiation source SO may include a shield (not shown) configured to prevent the laser beam 2 from propagating through the opening 8 and into the lithography device LA (where it could damage optical components). This shield may be supported by an enclosure structure via a support (not shown). The shielding element and the support element together form a shield for the radiation source SO. Therefore, as schematically indicated in Figure 2A, the generally circular portion 20 of the field-faceted mirror device 10 may include: a central portion 22, which coincides with the shield for the radiation source SO and does not receive any radiation; and two portions 24 and 26, which receive radiation. It should be understood that this is schematic and the shield can have any shape or configuration.

[0104] The known faceted field mirror device 10 for use in an EUV lithography apparatus of the type shown in FIG1 is now described with reference to FIG2A and FIG2B.

[0105] In known EUV lithography equipment, the faceted field mirror device 10 includes a plurality of field facets. Specifically, in such known EUV lithography equipment, the portions 24 and 26 of the faceted field mirror device 10 that receive radiation from the radiation source SO have a plurality of field facets. For example, the portions 24 and 26 of the faceted field mirror device 10 that receive radiation from the radiation source SO may have approximately 100 field facets (e.g., 300 field facets). In the plane of the faceted field mirror device 10, each field facet may have a curved shape 28, as shown in FIG2B. Generally, in the plane of the faceted field mirror device 10, each field facet may have an elongated shape having a longer dimension in the x-direction and a shorter dimension in the y-direction. Each field facet includes a mirror surface, which may be configured to image the intermediate focal point 6 onto the faceted pupil mirror device 11. To achieve this, the field facet may, for example, be concave.

[0106] The faceted pupil mirror device 11 includes a plurality of pupil facets. The faceted pupil mirror device 11 is configured to project the image of each field facet of the faceted field mirror device 10 onto the illumination area IR (also referred to as a slit or illumination slit) at the patterning device MA. The illumination system IL is configured such that each field facet is imaged onto the illumination area IR in an overlapping manner. Ideally, each image of the field facet fills the illumination area IR. The overlapping of the images of the field facets at least partially averages the irregularity of the radiation beam B provided by the radiation source SO.

[0107] The illumination area IR can be curved or straight. Generally, in a scanning lithography apparatus LA, the illumination area IR is elongated, having a longer dimension and a shorter dimension. The shorter dimension may coincide with the scanning direction of the support structure MT, and the longer dimension may coincide with the non-scanning direction. The illumination area IR can be curved or straight. The illumination area IR is indicated in Figure 1, which shows the patterning apparatus in cross-section. The longer dimension of the illumination area IR (in the x-direction) is perpendicular to the plane of Figure 1, and the shorter dimension of the illumination area IR (in the y-direction) lies in the plane of Figure 1.

[0108] It should be understood that the illumination region IR may have a shape in the plane of the patterning device MA that generally corresponds to the shape of each of the field surfaces, for example, typically in the form of shape 28 shown in Figure 2B. It should be noted that the shape and size of each field surface may not be exactly the same as the illumination region IR, and depends on the magnification factors applied in the x and y directions by the field surfaces, the pupil surface (and any other optics upstream of the illumination region IR). The edge of the illumination region IR may be defined by two sets of magnifying mask blades (not shown) that cut off radiation so that the radiation does not incident on the patterning device outside the illumination region IR. Therefore, each of the field surfaces may be configured such that, in the absence of such magnifying mask blades, it will overfill the illumination region IR. The illumination region IR may receive radiation from the central portion of each field surface, as indicated by the dashed line 29 inside the example shape 28 of the field surface shown in Figure 2B.

[0109] Therefore, in some existing EUV lithography equipment, EUV radiation is also provided in the area surrounding the illumination area IR (although the illumination area at the patterning device MA is masked by this portion of EUV radiation, which is not used to expose the substrate W). This area surrounding the illumination area IR can receive EUV radiation from the edge portion of each field-faceted mirror (which may be the portion positioned between the dashed line 29 and the shape edge in the schematic diagram of FIG. 2B). At least a portion of this portion of EUV radiation not used to expose the substrate W can be incident on an energy sensor, which can be used to monitor and control the dose of radiation delivered to the substrate W. Typically, these known lithography illumination systems can direct between 5% and 10% of the total radiation to the area between the dashed line 29 and the shape edge in the schematic diagram of FIG. 2B.

[0110] It has been proposed to use a faceted field mirror device 10 with a large number of individually directional or movable reflective optical elements in order to provide better control over the illumination pattern of the lithography equipment.

[0111] Embodiments of the present invention may include a faceted field mirror device 10 comprising a two-dimensional array of independently movable reflective optical elements. Specifically, embodiments of the present invention may utilize the additional flexibility provided by the faceted field mirror device 10 comprising a two-dimensional array of independently movable reflective optical elements to optimize and / or improve the measurement of the energy and / or intensity of radiation that can be used for dose control, as discussed herewith reference to Figures 3 through 6.

[0112] FIG3 is a schematic diagram of a device 30 for adjusting, guiding and monitoring a radiation beam according to an embodiment of the present invention. The device 30 includes a first optical component 32 and a sensor 34.

[0113] The first optical component 32 includes a two-dimensional array of independently movable reflective optical elements configured to receive radiation 36 (e.g., from a radiation source). Each of these independently movable reflective optical elements includes a microelectromechanical system (MEMS). Therefore, the first optical component 32 can be considered as including a MEMS micromirror array.

[0114] Each of the reflective optical elements may, for example, be a multi-layered mirror. Each of the reflective optical elements may be configured such that its orientation can be controlled about one or two axes, thereby controlling the position to which it directs radiation. For example, each of the reflective optical elements may have one or more actuators by which the reflective optical element can rotate about one axis or two orthogonal axes. In this way, each of the reflective optical elements can be controlled to direct radiation in a specific direction.

[0115] Depending on the circumstances, each of the reflective optical elements can be configured to be set to an inactive state, in which the reflective optical element directs the radiation received from the intermediate focus 6 in a direction that prevents the radiation from reaching the illumination area IR. For example, radiation from a reflective optical element set to an inactive state can be directed to a beam cutoff to absorb the radiation.

[0116] Sensor 34 is operable to determine the intensity of the radiation received therefrom. Sensor 34 may be referred to as an energy sensor or an intensity sensor. It should be understood that sensor 34 may use any available photosensitive technology. For example, sensor 34 may include one or more of the following: photodiode, complementary metal-oxide-semiconductor (CMOS), and / or charge-coupled device (CCD).

[0117] As will be discussed further below, the two-dimensional array of independently movable reflective optical elements comprises a first set of reflective optical elements and a second set of reflective optical elements.

[0118] A first set of reflective optical elements is configured to direct a first portion 38 of the radiation received therefrom to a sensor 34. A second set of reflective optical elements is configured to direct a second portion 40 of the radiation received therefrom to an illumination area 42.

[0119] The first optical component 32 can form a portion of the illumination system IL of a lithography apparatus LA of the type shown in FIG. 1 and described above. The device 30 can be adapted to receive and guide extreme ultraviolet (EUV) radiation. For example, the first optical component can form a field-faceted mirror device 10 of the illumination system IL of the lithography apparatus LA. In use, a patterning device MA (e.g., a magnifying mask or shield) can be placed in the illumination area 42. For example, during scanning lithography exposure, the patterning device MA can move through the illumination area 42 in the scanning direction, as schematically indicated by arrow 43. The image of the patterning device MA can be (e.g., using a projection optics PS) formed on a target area of ​​the substrate W using a second portion 40 of the radiation.

[0120] The device 30 shown in Figure 3 allows the second portion 40 of radiation to be used to project a pattern onto a target portion of the substrate W, and simultaneously allows the sensor 34 to measure the intensity or energy of the first portion 38 of radiation. The intensity or energy of the second portion 40 of radiation can be determined from the measured intensity or energy of the first portion 38 of radiation, which allows for accurate control of the radiation dose delivered to the target portion of the substrate W.

[0121] As shown in FIG. 4, depending on the situation, the device 30 may further include a second optical component 44, which is configured to receive radiation from a second portion 40 (a second set of self-reflecting optical elements) and guide it to the illumination area 42. The second optical component 44 may be a faceted mirror device comprising a plurality of facets. For example, the second optical component 44 may form part of the illumination system IL of a lithography device LA. For example, the second optical component 44 may form the pupil faceted mirror device 11 of the illumination system IL of a lithography device LA of the type shown in FIG. 1 and described above.

[0122] In use, the first optical component 32 and the second optical component 44 can be configured together to adjust the radiation beam 36 before it is incident on the patterning device MA disposed in the illumination area 42. The first optical component 32 and the second optical component 44 can together provide the desired cross-sectional shape and desired spatial and angular distribution to the radiation beam. It should be understood that, in addition to the first optical component and the second optical component, this illumination system may include other mirrors or devices. To achieve a desired illumination mode, the orientation of the reflective optical element of the first optical component 32 can be controlled to guide radiation to a selected pupil facet of the second optical component 44. Some pupil facets may receive radiation from more than one reflective optical element; other pupil facets may not receive radiation. This configuration can be used to achieve a large number of different illumination modes.

[0123] Depending on the situation, as shown in FIG4, in some embodiments, the sensor 34 may be mounted on or connected to the second optical component 44. In some embodiments, the sensor 34 may be mounted on the pupil faceted mirror device 11 inside the illumination system IL of the lithography device LA, as schematically indicated by box 34a in FIG1.

[0124] Alternatively, in some embodiments, the sensor 34 may be positioned close to the support structure MT, as schematically indicated by box 34b in FIG1. ​​In this configuration, the sensor 34 may be described as being at the magnification level. With this configuration, the sensor 34 may be positioned in a location corresponding to the area surrounding the illumination area IR, which receives EUV radiation from the edge portion of each field-faceted mirror (which may be the portion positioned between the dashed line 29 and the shape edge in the schematic illustration in FIG2B).

[0125] Alternatively, in some embodiments, the sensor 34 may be positioned close to the substrate stage WT. For example, the sensor 34 may be positioned between the imaging optics 13, 14 within the projection system PS and the substrate stage WT, as schematically indicated by box 34c in FIG1. ​​In this configuration, the sensor 34 may be described as being located at the substrate or wafer level. For example, the sensor 34 may be positioned close to the dynamic gas lock. With this configuration, the sensor 34 can be operated to measure the intensity and uniformity of the patterned radiation beam B' across the entire optical column. Advantageously, this will enable additional real-time and highly accurate system transfer measurements and dose reproducibility correction. Such improvements in system transfer measurements and / or monitoring can lead to more accurate diagnostics, thereby reducing unscheduled downtime of the lithography equipment LA and increasing the availability of the lithography equipment LA.

[0126] In some embodiments, each location in the illumination region IR may receive radiation from a plurality of reflective optical elements in a second set of reflective optical elements, as discussed herein.

[0127] The first optical assembly 32 may comprise approximately 100,000 independently movable reflective optical elements. These reflective optical elements may substantially cover portions 24 and 26 of the faceted field mirror device 10 that receive radiation from the radiation source SO (see Figure 2A and accompanying discussion). Each location in the illumination area IR may receive radiation from approximately 100 independently movable reflective optical elements, as discussed further hereafter.

[0128] In some embodiments, a two-dimensional array of independently movable reflective optical elements disposed on the faceted field mirror device 10 can be considered as comprising a plurality of groups of reflective optical elements. Each group of reflective optical elements may comprise a plurality of adjacent independently movable reflective optical elements on the faceted field mirror device 10. Each of the plurality of groups of reflective optical elements may be referred to as a cluster of reflective optical elements.

[0129] Each group of reflective optical elements can be configured to substantially replace one of the field surfaces discussed above. For example, each group can cover an area of ​​the faceted field mirror device 10 that substantially corresponds to the shape of the field surface of the existing faceted field mirror device 10 (e.g., an area having a shape substantially the same as shape 28 shown in FIG. 2B). It should be understood that the shape of each of the reflective optical elements can be substantially square or rectangular, and therefore if the group is configured as a substantially curved elongated area of ​​the faceted field mirror device 10 (similar to shape 28 shown in FIG. 2B), the shape can have serrated or pixelated edges along the curved side of the shape. Furthermore, the orientation of the reflective optical elements within each group can be configured to provide equivalent optical power or concave shape to the field surface of the existing faceted field mirror device 10.

[0130] Each group of reflective optical elements may include: a first subgroup of reflective optical elements configured to direct radiation received by the first subgroup to the sensor 34; and a second subgroup of reflective optical elements configured to direct radiation received by the second subgroup to the illumination area 42. In some embodiments, the first subgroup may include a single reflective optical element or a few reflective optical elements.

[0131] Furthermore, the radiation guided to the illumination area 42 by the second subgroup of each of the different groups of reflective optical elements spatially overlaps at the illumination area 42 (in a manner similar to the overlap of each image of the field facet described above).

[0132] Each of the plurality of groups may be referred to as a field-faceted mirror or a virtual field-faceted mirror. There may be approximately 100 (e.g., 300) groups of independently movable reflective optical elements. Each group may contain approximately 1000 independently movable reflective optical elements. For example, in one embodiment, each group may contain 10 columns of independently movable reflective optical elements, each column having 100 independently movable reflective optical elements. A first subgroup of each group may contain approximately one reflective optical element. The remaining independently movable reflective optical elements in each group may form a second subgroup.

[0133] In some embodiments, a plurality of adjacent, independently movable reflective optical elements in each group may substantially cover a continuous area of ​​the first optical component 32. It should be understood that this may mean that any gap between adjacent reflective optical elements may be minimal.

[0134] The shape of a continuous region of a first optical component covered by a plurality of adjacent independently movable reflective optical elements in a group of independently movable reflective optical elements may be referred to as the shape of the group of independently movable reflective optical elements. The shape of each of the group of independently movable reflective optical elements may substantially correspond to the shape of the illumination region IR (in a manner similar to how the shape of each of the field surfaces described above substantially corresponds to the shape of the illumination region IR).

[0135] Each of the plurality of groups of independently movable reflective optical elements may have substantially the same size and shape. In some embodiments, the shape of each of the plurality of groups may be curved. In some embodiments, the shape of each of the plurality of groups may be generally rectangular.

[0136] In some embodiments, a plurality of groups of movable reflective optical elements may substantially cover a region of the first optical component 32 that receives radiation during use. This region of the first optical component 32 that receives radiation during use may, for example, substantially cover portions 24, 26 of the faceted field mirror device 10 that receive radiation from the radiation source SO. It should be understood that this may mean that any gaps between adjacent groups of reflective optical elements within the region of the first optical component that receives radiation during use can be minimized.

[0137] In some embodiments, a first subgroup of reflective optical elements from different groups of reflective optical elements may be disposed in different locations within the group.

[0138] For example, in an embodiment where the independently movable reflective optical elements of each group are arranged in multiple columns and rows, a first subgroup of reflective optical elements from any two different groups (configured to guide radiation received from the radiation source to the sensor) can be arranged in different columns and / or rows within its group. For example, in an embodiment where each group covers a region of the faceted field mirror device 10 that substantially corresponds to the shape of the field facet of the existing faceted field mirror device 10 (e.g., a region having a shape substantially the same as that of shape 28 shown in FIG. 2B), the first subgroups of reflective optical elements from different groups can be arranged in different positions within shape 28. Advantageously, this arrangement can reduce the effect of directing a subset of independently movable reflective optical elements of each group to the sensor 34 (different from the illumination area 42). By removing elements of the first subset from different portions of different groups, multiple different areas of the illumination area 42 are affected. Furthermore, ensuring that the first subgroup of reflective optical elements from different groups of reflective optical elements is positioned at different locations within the group allows for the determination of intensity variations within the illumination area and / or allows for sampling or measurement of slit profiles. Particularly advantageous is that the elements from the first subset of all groups coincide with their positions within the illumination area distributed along the non-scanning direction of the device (e.g., the x-direction in the figure).

[0139] In some embodiments, the second optical component 44 may be configured to form images of a second subgroup of each of a plurality of groups in the illumination region IR, all of which spatially overlap in the illumination region IR.

[0140] In some embodiments, a second set of reflective optical elements is configured to direct a second portion 40 of the radiation received by the second set to the illumination area 42, such that the radiation from the second set of reflective optical elements overlaps at the illumination area 42 to substantially cover the illumination area 42 a first number n1 times. For example, the first number n1 may correspond to the number of groups of reflective optical elements (each group substantially replacing a field-faceted mirror). In such embodiments, the number of reflective optical elements in the first set is equal to or greater than the first number n1. The first number n1 may be about 100, for example 300.

[0141] A second set of reflective optics is configured to guide a second portion 40 of radiation to an illumination area 42 such that radiation from the second set of reflective optics overlaps at the illumination area 42 to substantially cover the illumination area 42 a first number n1 times. For example, a two-dimensional array of independently movable reflective optics may comprise a first number n1 groups, each of which substantially covers the illumination area 42 and contributes to the second set of reflective optics. As explained above, each group may comprise clusters of adjacent reflective optics. Device 30 ensures that at least one reflective optic from each of these groups (which are all imaged onto the illumination area 42) contributes to the guidance to the first set of sensors. This ensures that sampling in the measurement of the energy or intensity of the radiation contributes to the radiation dose delivered to the illumination area 42 for each group, and that the measurement of the energy or intensity of the first portion of the radiation is an accurate estimate of the energy or intensity of the second portion of the radiation.

[0142] In some embodiments, the number of reflective optical elements in the first set may be an integer multiple of a first number n1 (which may be the number of groups of reflective optical elements that substantially replace the field-faceted mirror). For example, in some embodiments, and the integer number (e.g., 1, 2, 3...) of reflective optical elements from each of these groups helps to direct a first portion of the radiation to the first set of sensors.

[0143] In some embodiments, the number of reflective optical elements in the first set is such that the energy of the first portion of the radiation is less than 4% of the total energy of the first and second portions of the radiation. For such embodiments, the device 30 shown in FIG3 is advantageous because it allows for this accurate dose control while reducing the amount of radiation used for intensity or energy measurement (and thus increasing the amount of radiation used for exposure) compared to existing configurations.

[0144] In some embodiments, the number of reflective optical elements in the first set may be such that the energy of the first portion of radiation is less than 1% of the total energy of the first and second portions of radiation. In some embodiments, the number of reflective optical elements in the first set may be such that the energy of the first portion of radiation is approximately 0.1% of the total energy of the first and second portions of radiation.

[0145] Therefore, the device 30 shown in FIG3 provides a significant improvement over existing lithography illumination systems, which can direct between 5% and 10% of the total radiation to the energy sensor (e.g., by providing radiation to the entire area between the dashed line 29 and the edge of the shape in the schematic illustration in FIG2B). In part, this reduction in the amount of radiation used for energy measurement is a result of using a two-dimensional array of independently movable reflective optics.

[0146] Furthermore, this reduction is feasible with current sensor technology. Currently, zoom masks and EUV energy sensors include filters for filtering out any out-of-band radiation. The filters also include elements (made of aluminum) configured to reduce the intensity of EUV radiation to within the dynamic range of the photosensitive portion of the sensor. Currently, EUV radiation attenuates by approximately 100 times, for example from 10% to 0.1%. Therefore, by adjusting the filter stack in the energy sensor to reduce the thickness of the EUV blocking element (or completely removing the stack), it would be feasible to measure using 0.1% of the radiation.

[0147] Therefore, it is estimated that approximately 0.1% of the EUV radiation beam can be used to achieve adequate energy measurements. This is 50 times smaller than that currently used in EUV lithography scanners. One advantage of directing this lower intensity of radiation to the energy sensor is that it reduces secondary electron emissions from such sensors, resulting in improved (linear) performance. Together with reduced filter stacking and optimized electronics and gain settings, the extremely low EUV intensity level can be sufficient while still ensuring measurement accuracy.

[0148] Advantageously, this significant high-power gain (approximately 5% of the EUV radiation power) in the second portion of the radiation used for exposure is expected to cause a significant gain in delivery. It is also estimated that the first-state sample will cause improved dose control and thus improved critical size uniformity.

[0149] In some embodiments, the number of reflective optical elements in the first set can be optimized to minimize the amount of radiation received by the first set of reflective optical elements, while allowing the total intensity of radiation received by the second subgroup of reflective optical elements to be determined with the desired accuracy.

[0150] In some embodiments, the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical assembly 32. Advantageously, since the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical assembly, the radiation beam 36 can be sampled at the first optical assembly relative to the sampling improvement sensor 34 provided by the energy sensor and field-faceted mirror of the conventional lithography illumination system. Such conventional lithography illumination systems only sample the area of ​​the field-faceted mirror device 10 that is not used for the exposure of the substrate W. In contrast, the embodiment of the device 30 shown in FIG3 can be configured to sample the area of ​​the field-faceted mirror device 10 that is not used for the exposure of the substrate but is surrounded by reflective optical elements and is used for the exposure of the substrate (smaller area). That is, embodiments of the present invention can be configured to sample a smaller area within the exposure zone of the field-faceted mirror device 10 for the substrate W (e.g., using a single MEMS mirror), rather than sampling only the entire edge portion of each field-faceted mirror (which may be the portion positioned between the dashed line 29 and the shape edge in the schematic illustration of FIG. 2B). Therefore, embodiments of the present invention can provide a more accurate determination of the energy of the radiation used for exposure, and / or provide information on the variation of the energy of the radiation across the illumination zone 42.

[0151] In some embodiments, the device may further include a controller 46 operable to control the position and / or orientation of each of the independently movable reflective optics, as discussed now with reference to FIG. 5. FIG. 5 is a schematic diagram illustrating some functions of the controller 46, which may form part of the device 30 shown in FIG. 3 or 4. The controller 46 is operable to configure the orientation of the independently movable reflective optics to direct a portion 38 of the received radiation to the sensor 34 and another portion 40 of the received radiation to the illumination area 42. To achieve this, the controller 46 is operable to send appropriate control signals 48 to the first optical component 32.

[0152] Sensor 34 may be operable to determine the intensity of the radiation received thereon. Specifically, sensor 34 may be operable to determine the intensity of radiation directed onto the first set of reflective optical elements. The sensor may be operable to output a signal 50 indicating the intensity of the radiation received thereon. This signal 50 indicating the intensity of the radiation received by sensor 34 may be received by controller 46.

[0153] In some embodiments, the device 30 has a plurality of configurations that can be controlled using the controller 46, as discussed herein.

[0154] For example, during exposure of a target area of ​​substrate W, controller 46 is operable to control the reflective optical elements to position them in a first configuration, as described above. The first configuration may be referred to as the exposure configuration. In the first configuration, controller 46 can position the reflective optical elements such that: (a) the energy of the first portion 38 of radiation is less than a threshold percentage of the total energy of the first portion 38 and the second portion 40 of radiation; (b) the amount of radiation received by the first set of reflective optical elements is minimized, while allowing the total intensity of radiation received by the second subgroup of reflective optical elements to be determined with a certain accuracy; and / or (c) the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical assembly 32.

[0155] In some embodiments, the controller 46 is operable to periodically and temporarily control the position and / or orientation of the independently movable reflective optical element of the first optical component 32 to position it in a second configuration. When the independently movable reflective optical element is in the second configuration, the energy of the first portion 38 radiated is greater than the energy when the independently movable reflective optical element is in the first configuration.

[0156] For example, more accurate and / or detailed measurements of the energy of radiation and / or the spatial distribution of radiation in the exposure area 42 can be achieved by placing independently movable reflective optical elements in the second configuration. This is achieved by increasing the number of reflective optical elements in the first set. Independently movable reflective optical elements can be placed in the second configuration for this purpose when the equipment 30, LA does not expose the target area of ​​the substrate W to radiation. That is, this can be done outside of standard batch exposures in the lithography equipment LA (e.g., during mask replacement, wafer replacement, or between exposures of different target areas).

[0157] Additionally, independently movable reflective optical elements can be placed in a second configuration during the initial system setup and / or calibration of the device.

[0158] In some embodiments, the sensor 34 may include an array of sensing elements, each configured to receive radiation from a location on the first optical assembly 32 corresponding to a different location within the illumination area 42. For example, each sensing element may be configured to receive radiation from a different location within one of a group of independently movable reflective optical elements. In such embodiments, the signal 50 output by the sensor 34 may indicate the intensity distribution of radiation across the illumination area 42.

[0159] The array of sensing elements can be a one-dimensional or two-dimensional array.

[0160] Advantageously, this allows for the measurement of slit uniformity and its offset within the illumination area IR. This avoids the need for wafer-level slit scanning. Furthermore, it enables combined reproducibility and slit uniformity correction and allows for monitoring of imaging performance at a much higher frequency than currently possible via wafer-level slit scanning. Consequently, this can result in a significant improvement in performance and also in improved throughput gain.

[0161] In some embodiments, a signal 50 output by sensor 34, indicating the intensity of the received radiation, may be received by radiation source SO (directly or indirectly via controller 46). In response, a pulsed radiation beam B generated by radiation source SO may be generated depending on the intensity determined by sensor 34 after receiving a portion of a previous pulse of radiation B. For example, sensor 34 may determine the energy of radiation beam B pulse by pulse, and this energy may be used as part of a feedback loop to stabilize the energy of the radiation beam generated by radiation source SO.

[0162] As discussed above, in some embodiments, sensor 34 is operable to determine spatial intensity information (e.g., if sensor 34 includes a sensor array). In such embodiments, signal 50 output from sensor 34 can also indicate the intensity distribution of radiation across illumination zone 42. In such embodiments, a pulse of pulsed radiation beam B generated by radiation source SO can be generated after receiving a portion of a previous pulse of radiation, depending on the spatial intensity information determined by sensor 34. That is, device 30 can feed back slit profile information determined by sensor array 34 for each pulse to radiation source SO. Specifically, this data not only provides intensity information to ensure dose reproducibility, but also provides information on slit uniformity and far-field stability. For LPP sources (as shown in FIG. 1), this information will allow the radiation source to optimize and stabilize the laser beam 2 to facilitate droplet alignment (at plasma formation zone 4), thereby further improving slit uniformity and far-field stability.

[0163] In some embodiments of the device 30, the sensor 34 is operable to quantify the alignment between the first optical component 32 and the radiation beam B received therefrom.

[0164] FIG6 is a schematic diagram of a method 60 according to an embodiment of the present invention. Method 60 can be implemented using the device 30 shown in FIG3 and FIG4 and described above. It should be understood that method 60 can implement any of the functions of the device 30 shown in FIG3 and FIG4 and described above.

[0165] Method 60 includes step 62 of generating a radiation beam (e.g., using a radiation source SO).

[0166] Subsequently, method 60 includes step 64 of guiding the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array of independently movable reflective optical elements comprising a first set of reflective optical elements and a second set of reflective optical elements.

[0167] Method 60 further includes step 66 of using a first set of reflective optical elements to guide a first portion of the radiation beam to a sensor and using the sensor to determine the intensity of the first portion of the radiation beam.

[0168] Method 60 further includes step 68 of using a second set of reflective optical elements to guide a second portion of the radiation beam to a magnifying mask so as to impart a pattern to the second portion of the radiation beam and form a patterned radiation beam.

[0169] As can be seen from the description of the device 30 shown in Figure 6 and Figures 3 and 4 above, steps 64 and 66 can be performed in parallel.

[0170] Method 60 further includes step 70 of projecting a patterned radiation beam onto a target area of ​​a substrate. The method is characterized in that it corresponds to the function of the device 30 shown in Figures 3 and 4 and described above.

[0171] Specifically, the energy of the first portion of the radiation (see step 66) may be less than 4% of the total energy of the first and second portions of the radiation. Furthermore, the number of reflecting optical elements in the first set may be equal to or greater than a first number n1 of the number of times the radiation from the second set of reflecting optical elements overlaps at the illumination area to substantially cover the illumination area. Furthermore, the first portion may be formed by a plurality of samples of the radiation beam uniformly distributed within the radiation beam at the first optical component.

[0172] Method 60 may include sequentially forming patterns on a plurality of target areas of one or more substrates W. For example, method 60 may include forming patterns on a plurality of substrates W and the patterns may be formed on a plurality of target areas on each substrate W. In such embodiments, method 60 may further include periodically determining the energy of the radiation beam and / or a more accurate and / or more detailed measurement of the spatial distribution of the radiation beam at the patterning device between exposures of different target areas.

[0173] Method 60 may include a feedback procedure in which the intensity of a first portion of the radiation beam determined by a sensor at step 66 is used to control the subsequent generation of radiation at step 62. The radiation beam generated at step 62 may be a pulsed radiation beam. In such embodiments, the pulse of the pulsed radiation beam generated at step 62 may be generated after a portion of a previous pulse of radiation has been received, depending on the intensity determined by the sensor at step 66.

[0174] At step 66, method 60 may further include using a sensor to determine the spatial distribution of the radiation beam at the patterning device. In such embodiments, the pulse of the pulsed radiation beam generated at step 62 may be generated after receiving a portion of a previous pulse of radiation, depending on the spatial intensity information determined by the sensor at step 66.

[0175] While reference may be specifically made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications. Possible other applications include manufacturing integrated optical systems, guiding and detecting magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and so on.

[0176] Although embodiments of the invention may be specifically referenced herein in the context of lithography apparatus, embodiments of the invention can be used in other apparatuses. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). Such apparatuses may be generally referred to as lithography tools. These lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0177] Where the context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. The machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, the machine-readable medium may include read-only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.); and others. Additionally, firmware, software, conventions, and instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and such actions are actually caused by a computing device, processor, controller, or other means of executing firmware, software, conventions, instructions, etc., and in performing such actions, enable actuators or other means to interact with the physical world.

[0178] Although specific embodiments of the invention have been described above, it will be understood that the invention may be practiced in other ways different from those described. The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the invention as described without departing from the scope of the claims set forth below. [Simplified Explanation of the Diagram]

[0089] Embodiments of the invention will now be described by way of example only with reference to the accompanying schematic drawings, in which: - FIG1 depicts a lithography system comprising a lithography device and a radiation source; - FIG2A schematically shows a generally circular portion of the field-faceted mirror device of the lithography system shown in FIG1, showing an intermediate shielding portion and two portions for receiving radiation; - FIG2B shows an example shape of the field facet of a faceted field mirror device in a known EUV lithography device of the form shown in FIG1; - FIG3 is a schematic diagram of a device for adjusting, guiding, and monitoring a radiation beam according to an embodiment of the invention; - FIG4 is a schematic diagram of a variation of the device shown in FIG3; - FIG5 is a schematic diagram showing some of the functions of a controller that can form part of the device shown in FIG3 or FIG4; and - FIG6 is a schematic diagram of a method according to an embodiment of the invention.

Claims

1. An optical device comprising: a first optical component including a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source; and a sensor operable to determine the intensity of the received radiation; wherein the two-dimensional array of independently movable reflective optical elements includes: a first set of reflective optical elements configured to guide a first portion of the radiation received by the first set to the sensor; and a second set of reflective optical elements configured to guide a second portion of the radiation received by the second set to an illumination area; and wherein the number of reflective optical elements in the first set is such that the energy of the first portion of the radiation is less than 4% of the total energy of the first and second portions of the radiation.

2. An optical device comprising: a first optical component including a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source; and a sensor operable to determine an intensity of the received radiation; wherein the two-dimensional array of independently movable reflective optical elements includes: a first set of reflective optical elements configured to guide a first portion of radiation received by the first set to the sensor; and a second set of reflective optical elements configured to guide a second portion of radiation received by the second set to an illumination area, such that the radiation from the second set of reflective optical elements overlaps in the illumination area to substantially cover the illumination area a first number of times; and wherein the number of reflective optical elements in the first set is equal to or greater than the first number.

3. The optical device of claim 2, wherein the number of one of the reflecting optical elements in the first set is such that the energy of the first portion of radiation is less than 4% of the total energy of the first and second portions of radiation.

4. An optical device comprising: a first optical assembly including a two-dimensional array of independently movable reflective optical elements configured to receive radiation from a radiation source; and a sensor operable to determine an intensity of the received radiation; wherein the two-dimensional array of independently movable reflective optical elements includes: a first set of reflective optical elements configured to guide a first portion of the radiation received by the first set to the sensor; and a second set of reflective optical elements configured to guide a second portion of the radiation received by the second set to an illumination area; and wherein the reflective optical elements in the first set of reflective optical elements are uniformly distributed within the first optical assembly.

5. The optical apparatus of claim 4, wherein the number of one of the reflecting optical elements in the first set is such that the energy of the first portion of radiation is less than 4% of the total energy of the first and second portions of radiation.

6. The optical apparatus of claim 4 or claim 5, wherein each position in the illumination area receives radiation from a plurality of reflective optical elements in the second set of reflective optical elements.

7. The optical device of claim 4 or claim 5, wherein the two-dimensional array of independently movable reflective optical elements comprises a plurality of groups, each group comprising a plurality of adjacent independently movable reflective optical elements, the plurality of adjacent independently movable reflective optical elements comprising: a first subgroup of reflective optical elements configured to direct radiation received by the first subgroup to the sensor; and a second subgroup of reflective optical elements configured to direct radiation received by the second subgroup to the illumination area.

8. The optical apparatus of claim 7, wherein the radiation directed to the illumination area by the second subgroup of different groups of reflective optical elements spatially overlaps in the illumination area.

9. The optical apparatus of claim 7, wherein each of the plurality of groups of independently movable reflective optical elements has substantially the same size and shape.

10. The optical apparatus of claim 7, wherein the first subgroup of reflective optical elements from different groups of reflective optical elements is disposed in different positions within those groups.

11. The optical device of claim 7, further comprising a second optical component configured to receive radiation and direct it to the illumination area by the second set of self-reflective optical elements.

12. The optical apparatus of claim 11, wherein the second optical component is configured to form an image of one of the second subgroups of each of the plurality of groups in the illumination area, all such images spatially overlapping in the illumination area.

13. The optical device of claim 11, wherein the second optical component is a faceted mirror comprising a plurality of facets.

14. The optical device of claim 11, wherein the sensor is disposed on or connected to the second optical component.

15. The optical device of claim 4 or claim 5, wherein each of the independently movable reflective optical elements comprises a microelectromechanical system (MEMS) micromirror.

16. The optical device of claim 4 or claim 5 further includes a controller operable to control a position and / or orientation of each of the independently movable reflective optical elements.

17. The optical device of claim 16, wherein the controller is operable to periodically and temporarily control the position and / or orientation of one of the independently movable reflective optical elements in order to position it in a second configuration.

18. The optical device of claim 17, wherein when the independently movable reflective optical elements are in the second configuration, one portion of the energy of the first portion of the radiation is greater than the energy when the independently movable reflective optical elements are in the first configuration.

19. The optical device of claim 4 or claim 5, wherein the sensor comprises an array of sensing elements, each sensing element being configured to receive radiation from a location on the first optical assembly corresponding to a different location within the illumination area.

20. The optical device of claim 19, further comprising a radiation source operable to generate a pulsed radiation beam and supply the pulsed radiation beam to the first optical component.

21. The optical apparatus of claim 20, wherein one pulse of the pulsed radiation beam is generated by the radiation source depending on an intensity determined by the sensor when a portion of a previous pulse of radiation is received.

22. The optical apparatus of claim 20, wherein one pulse of the pulsed radiation beam is generated by the radiation source depending on spatial intensity information determined by the sensor when a portion of a preceding pulse of radiation is received.

23. The optical device of claim 4 or claim 5, wherein the sensor is operable to quantify an alignment between the first optical component and a radiation beam thereby received.

24. The optical device of claim 4 or claim 5 further includes a support structure configured to support a patterning device such that the patterning device is disposed in or movable through the illumination area, and wherein the sensor is disposed close to the support structure.

25. The optical apparatus of claim 4 or claim 5, further comprising: a substrate stage configured to support a substrate; and a projection system comprising an imaging optics configured to receive radiation from the illumination area and form an image of an object disposed in the illumination area on a substrate supported by the substrate stage.

26. The optical apparatus of claim 25, wherein the sensor is disposed between the imaging optics and the substrate stage.

27. A lithography apparatus or a lithography system comprising the optical device of any one of claims 1 to 26.

28. A method of forming a pattern on a target area of ​​a substrate, the method comprising: generating a radiation beam; directing the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array comprising a first set of reflective optical elements and a second set of reflective optical elements; directing the first portion of the radiation beam to a sensor using the first set of reflective optical elements and determining the intensity of the first portion of the radiation beam using the sensor; and directing the second portion of the radiation beam to a reticle using the second set of reflective optical elements to impart a pattern onto the second portion of the radiation beam and form a patterned radiation beam; and projecting the patterned radiation beam onto the target area of ​​a substrate; wherein the energy of the first portion of the radiation is less than 4% of the total energy of the first and second portions of the radiation.

29. A method of forming a pattern on a target area of ​​a substrate, the method comprising: generating a radiation beam; directing the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array comprising a first set of reflective optical elements and a second set of reflective optical elements; directing the first portion of the radiation beam to a sensor using the first set of reflective optical elements and determining the intensity of the first portion of the radiation beam using the sensor; and directing a second portion of the radiation beam to a magnifying glass using the second set of reflective optical elements to impart a pattern to the second portion of the radiation beam and form a patterned radiation beam; and projecting the patterned radiation beam onto the target area of ​​a substrate; wherein the second portion comprises a plurality of spatially overlapping contributions, each originating from a group of adjacent reflective optical elements; and wherein the first set comprises one or more reflective optical elements from each of the plurality of groups.

30. The method of claim 29, wherein the first set comprises an integer number of reflective optical elements from each of the plurality of groups.

31. A method for forming a pattern on a target area of ​​a substrate, the method comprising: generating a radiation beam; directing the radiation beam to a first optical assembly comprising a two-dimensional array of independently movable reflective optical elements, the two-dimensional array comprising a first set of reflective optical elements and a second set of reflective optical elements; directing the first portion of the radiation beam to a sensor using the first set of reflective optical elements and determining the intensity of the first portion of the radiation beam using the sensor; and directing a second portion of the radiation beam to a magnifying glass using the second set of reflective optical elements to impart a pattern to the second portion of the radiation beam and form a patterned radiation beam; and projecting the patterned radiation beam onto the target area of ​​a substrate; wherein the first portion is formed by a plurality of samples of the radiation beam uniformly distributed within the radiation beam.

32. The method of claim 31, further comprising using the sensor to determine one spatial distribution of the radiation beam at the patterning device.

33. The method of claim 31 or claim 32, comprising sequentially forming a pattern on a plurality of target areas of one or more substrates.

34. The method of claim 33, further comprising a more accurate and / or more detailed measurement of the energy of the radiation beam and / or a spatial distribution of the radiation beam at the patterning device, periodically determining between exposures of different target areas.

35. The method of claim 32, wherein the radiation beam is a pulsed radiation beam, and wherein a pulse of the pulsed radiation beam is generated depending on an intensity determined by the sensor when a portion of a previous pulse of radiation is received.

36. The method of claim 35, wherein one pulse of the pulsed radiation beam is generated based on spatial intensity information determined by the sensor when a portion of a previous pulse of radiation is received.

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