Lithographic apparatus, homogeneity sensor having plurality of sensing elements for use in lithographic apparatus, method of determining property of radiation beam, and method of determining calibration of optical element for lithographic system

Abstract

A method of determining a property of a radiation beam within a lithographic system is described herein. The method includes measuring a plurality of intensities for each of a plurality of segments of the radiation beam having different positions in a first direction. Each of the plurality of intensities is measured using a different one of a plurality of sensing elements of the sensor. Each of the plurality of intensities corresponds to a different one of a plurality of portions of the radiation beam having different positions in the second direction. The plurality of portions of the radiation beam correspond to an entire section of the radiation beam. The method further includes determining a property of the radiation beam using at least one of the measured plurality of intensities for at least one of the plurality of segments of the radiation beam.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to European application 23185163.5, filed on 13 July 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a method for determining the properties of a radiation beam, particularly in a photolithography system. A method for determining the calibration of optical elements used in a photolithography system is also described herein. Background Technology

[0004] A photolithography apparatus is a machine configured to apply a desired pattern onto a substrate. Photolithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A photolithography apparatus can project a pattern from a patterning apparatus (e.g., a mask) onto a radiation-sensitive material (resist) layer disposed on a substrate.

[0005] To project a pattern onto a substrate, a photolithography apparatus can 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 photolithography apparatus using radiation with a wavelength of, for example, 193 nm, a photolithography apparatus using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] Typically, the optics of a photolithography apparatus are arranged to irradiate an irradiation area in the image plane. The irradiation area can be elongated and may have a longer dimension defining a first direction and a shorter dimension defining a second direction. The second direction can be the direction of substrate movement (on the substrate stage), and therefore can be referred to as the scanning direction. The first direction can be referred to as the non-scanning direction. The radiation beam (irradiating the irradiation area) may not be uniform in either the first or second direction.

[0007] A slit uniformity measurement can be performed using a single sensing element that extends across the entire radiation beam in a second direction. Such a slit uniformity measurement can measure the intensity of the radiation beam integrated across the scanning direction at multiple different locations in the non-scanning direction. While such a measurement can be used for dose control, it provides very little additional information, such as information related to the beam's position.

[0008] The objective of this invention is to alleviate one or more problems associated with the prior art. Summary of the Invention

[0009] In a first aspect of the invention, there is a method for determining the properties of a radiation beam within a photolithography system. The method includes measuring a plurality of intensities for each of a plurality of segments of the radiation beam having different positions in a first direction. Each of the plurality of intensities can be measured using a different sensing element of a plurality of sensing elements of a sensor. Each of the plurality of intensities may correspond to a different portion of a plurality of parts of the radiation beam having different positions in a second direction. The plurality of parts of the radiation beam may correspond to entire segments of the radiation beam. The method may further include determining the properties of the radiation beam using at least one of the measured intensities for at least one of the plurality of segments of the radiation beam.

[0010] The method described according to the first aspect is advantageous, as now discussed.

[0011] The total intensity of each segment of the radiation beam can be determined by measuring multiple intensities corresponding to the entire segment of the radiation beam for each segment in a first direction. For example, the total intensity of the radiation beam (integrated in a second direction) of said segment can be determined by adding up all the multiple intensities for a given segment of the radiation beam. This is advantageous because it can form the basis for uniformity (or slit uniformity) measurements. For example, a lithography system can be a scanner and thus capable of forming an image on a substrate (e.g., a wafer coated with resist) as a scanning exposure operation. The first direction can correspond to the non-scanning direction of the lithography system, and the second direction can correspond to the scanning direction of the lithography system. For all locations in the non-scanning direction, it is desirable to ensure that the integral of the intensity of the radiation beam in the scanning direction is the same or as close as possible. This ensures that the dose of radiation received by all portions of the substrate is the same (or as close as possible). Any variation in dose may lead to degraded imaging performance. It is desirable to measure the integral of the intensity of the radiation beam in the scanning direction at multiple locations in the non-scanning direction. These measurements can form part of a feedback loop to improve slit uniformity.

[0012] Currently, these slit uniformity measurements are performed using a single sensing element extending across the entire radiation beam in the scanning direction, and these slit uniformity measurements can therefore measure the intensity integrated across the entire scanning direction at multiple different locations in the non-scanning direction. Since accurate dose control is critical, these slit uniformity measurements are performed regularly in the lithography system.

[0013] In contrast, the method according to the first aspect of this disclosure uses multiple sensing elements (i.e., at least two sensing elements) instead of a single sensing element. Advantageously, this allows other properties of the radiation beam to be determined while performing a slit uniformity measurement. For example, the method may include determining the position of the radiation beam relative to the sensors. Alternatively or additionally, the method allows for the calibration of the orientation of one or more optical elements in the optical path of the radiation beam.

[0014] Such a method can improve the throughput of lithography equipment by reducing the amount of time spent determining the position of the radiation beam. Alternatively, such a method can improve the accuracy of lithography equipment by allowing the position of the radiation beam to be determined more frequently without sacrificing throughput. As another benefit, the method can improve the overlap performance of lithography equipment.

[0015] The nature of the radiation beam can be its position. This position can be in a first direction and / or a second direction.

[0016] Determining the position of the radiation beam may also include: determining parameters for at least one of a plurality of segments of the radiation beam, depending on at least one of a plurality of measured intensities; and using a calibration function to determine the position of the radiation beam based on the determined parameters.

[0017] For example, the method may include determining a parameter based on each of a plurality of corresponding measured intensities. The determined parameter may be the difference between a determined first intensity and a determined second intensity.

[0018] In some embodiments, a first intensity and a second intensity are determined for each of a plurality of segments of a radiation beam having different positions in a first direction, wherein each of the first intensity and the second intensity corresponds to a different portion of two adjacent portions of the radiation beam having different positions in a second direction, and wherein the two portions of the radiation beam correspond to the entire segment of the radiation beam. For example, the sensor may include only two sensing elements, and therefore the plurality of intensities may consist only of the first intensity and the second intensity. Alternatively, the sensor may include more than two sensing elements, and each of the first intensity and the second intensity may be determined by summing one or more of the measured plurality of intensities. For example, for an embodiment in which the sensor includes four sensing elements, each of the first intensity and the second intensity may be determined by summing two of the measured plurality of intensities. As another alternative, for a sensor including more than two sensing elements, parameters may be determined based on each of the intensities measured by each sensing element. In other words, the measured intensities may not be summed together. Advantageously, by determining parameters in this way, the resolution of the determined parameters can be improved.

[0019] The determined parameter can be the difference between two items: (a) the sum of a first intensity determined for all segments of the radiation beam; and (b) the sum of a second intensity determined for all segments of the radiation beam. The determined parameter can be the difference between two items: (a) the first intensity determined for a segment of the radiation beam; and (b) the second intensity determined for a segment of the radiation beam. The parameter can be determined for each segment of the radiation beam.

[0020] The method may further include applying a calibration function to the determined parameters. In other words, the calibration function can correlate the determined parameters with the position of the beam.

[0021] The method may also include determining a calibration function.

[0022] As an example, determining the calibration function may include determining expected values ​​for parameters at multiple different locations of the radiation beam relative to the sensor. Determining the calibration function may also include interpolating between the expected values ​​of the parameters determined at the multiple different locations of the radiation beam. For example, determining the calibration function may include fitting a model to the determined expected values ​​as a function of the location of the radiation beam (e.g., as a least-squares fit). The model may be a linear relationship.

[0023] The method may also include storing a calibration function in memory. For example, in some embodiments, the calibration function may be stored in memory for future use. For example, in some embodiments, the calibration function may be determined only once. Subsequently, the calibration function can be retrieved from memory.

[0024] The method may also include receiving a calibration function. For example, the calibration function may have been previously determined and stored in a computer-readable storage medium.

[0025] The nature of a radiation beam can be the position of a portion of the beam. The position of such a portion of the beam can indicate the orientation or tilt of an optical element within the optical path of the beam. These measurements can allow for the calibration and / or correction of the orientation or tilt of such optical elements.

[0026] Measuring multiple intensities for each of a plurality of segments of a radiation beam that have different positions in a first direction may include: measuring a first intensity of a first portion using a first sensing element of a plurality of sensing elements of a sensor; and measuring a second intensity of a second portion using a second sensing element of a plurality of sensing elements of a sensor; and the first and second intensities are measured at approximately the same time.

[0027] Advantageously, by measuring multiple intensities at approximately the same time, the time spent measuring multiple intensities can be reduced. It will be understood that, for examples where the sensor includes more than two sensing elements, additional measurements of the intensities can be taken at approximately the same time.

[0028] The first and second parts can correspond to the first segment of the radiation beam.

[0029] The first portion can correspond to a first segment of the radiation beam; and the second portion can correspond to a second segment of the radiation beam. In other words, the first portion can be offset relative to the second portion in the first direction. The first segment and the second segment can be adjacent segments. Advantageously, measuring intensity in this way allows the sensing element to be placed closer together in the second direction.

[0030] In a second aspect of the invention, there is a method comprising: adjusting a first optical element to a position or orientation such that radiation is guided by the first optical element and forms a portion of a radiation beam illuminating at least one of a plurality of sensing elements; adjusting one or more other optical elements such that the radiation guided by the one or more other optical elements does not illuminate at least one of the plurality of sensing elements; measuring the position of the portion of the radiation beam guided by the first optical element; and using the measured position of the portion of the radiation beam guided by the first optical element to determine a calibration for the position or orientation of the first optical element.

[0031] The methods of the first and second aspects can be executed together. Alternatively, either method can be executed individually.

[0032] The first optical element can be a micromirror of a micromirror array. The method allows for the calibration of the position or orientation of the micromirrors during slit uniformity measurements. Advantageously, because these slit uniformity measurements are performed regularly, the orientation of the micromirrors can be determined with little or no loss of additional lithography production. By calibrating a different subset of the micromirrors in the micromirror array using each subsequent slit uniformity measurement, all micromirrors (potentially a large number) can be calibrated within multiple slit uniformity measurements. By using a sensor comprising multiple sensing elements, the micromirror array can be calibrated in two dimensions. In other words, the micromirrors can be calibrated in an additional dimension compared to calibrations performed using known methods and / or sensors. As another advantage, the time required for the calibration process of the micromirror array can be reduced from 24 hours to 5 hours using a sensor comprising twenty sensing elements.

[0033] The method may further include moving the sensor from a first sensor position to a second sensor position. The method may also include repeating the method for a second optical element. In other words, the method can allow for the calibration of multiple optical elements. Calibration for different optical elements can be determined for each of the different positions in the first direction.

[0034] Calibration for determining the position or orientation of the first optical element may include comparing the determined position of the radiation beam with the expected position of the radiation beam.

[0035] Alternatively, calibration for determining the position or orientation of the first optical element may include: converting the determined position of the radiation beam into the orientation of the first optical element; and comparing the determined orientation of the first optical element with the expected orientation of the first optical element.

[0036] In a third aspect, there exists a computer-readable storage medium that, when executed by one or more processors, causes a lithography system to perform the method described in the first or second aspect.

[0037] In the fourth aspect, there exists a lithography apparatus configured to perform the methods described in the first or second aspect.

[0038] In a fifth aspect, there exists a photolithography apparatus or tool comprising: an optical element arranged to irradiate an irradiation area in an image plane, the irradiation area being elongated and having a longer dimension defining a first direction and a shorter dimension defining a second direction; a substrate stage configured to support a substrate, the substrate stage being movable to position an object thereby supported within the irradiation area; and a sensor supported by the substrate stage and comprising a plurality of sensing elements, wherein each of the plurality of sensing elements is disposed at a different position in the second direction, and wherein the extent of the plurality of sensing elements in the second direction is greater than the shorter dimension of the irradiation area.

[0039] A lithography device can be a scanner and is therefore capable of performing scanning exposure operations to form an image on a substrate (e.g., a wafer coated with resist). A first direction can correspond to the non-scanning direction of the lithography device, and a second direction can correspond to the scanning direction of the lithography device.

[0040] Because the range of multiple sensing elements in the second direction is larger than the shorter dimension of the irradiated area, the sensor can be used to determine the total intensity of radiation received by a segment of the irradiated area at a given location in the first direction. By stepping or scanning the sensor through the irradiated area in the first direction, the total intensity of radiation received by multiple segments of the irradiated area at different locations in the first direction can be determined. This is advantageous because it can form the basis for uniformity (or slit uniformity) measurements. These measurements can form part of a feedback loop to improve slit uniformity and improve dose control.

[0041] The lithography apparatus or tool described in the fifth aspect of this disclosure can be used to implement the method described in the first aspect of the present invention.

[0042] The first sensing element and the second sensing element among the multiple sensing elements can be positioned at the same location in the first direction.

[0043] A first sensing element and a second sensing element among a plurality of sensing elements can be positioned at different locations in a first direction. In other words, the first and second sensing elements can be offset from each other in the first direction. Advantageously, arranging the sensing elements in this way allows the sensing elements to be placed closer together in a second direction. The magnitude of the offset can be equivalent to how much the sensor moves.

[0044] In the sixth aspect, there exists a uniformity sensor comprising multiple sensing elements for use in a lithography apparatus. Advantageously, such a sensor can be used to perform the method described in the first aspect. The uniformity sensor may be a slit uniformity sensor.

[0045] Photolithography equipment may include sensors. Attached Figure Description

[0046] Embodiments of the invention will now be described with reference to the accompanying illustrative drawings, which are by way of example only, in which:

[0047] - Figure 1 Describes a lithography system including lithography equipment and a radiation source;

[0048] - Figure 2A Describe examples of known slit uniformity sensors;

[0049] - Figure 2B An example depicting a sensor according to an embodiment of the present invention;

[0050] - Figure 2C , Figure 2D and Figure 2E Depicting alternative exemplary sensors according to embodiments of the present invention;

[0051] - Figure 3A An exemplary curve depicting the intensity of the radiation beam as a function of the y-coordinate;

[0052] - Figure 3B Depiction can be applied to... Figure 2B An exemplary curve of the calibration function for the sensor's measurement;

[0053] - Figure 4 It is a flowchart of a method for determining the properties of a radiation beam within a photolithography system; and

[0054] - Figure 5 This is a flowchart of a method for determining the calibration of the first optical element. Detailed Implementation

[0055] Figure 1 A lithography system including a radiation source SO and a lithography apparatus LA is shown. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA includes an irradiation system IL, a support structure MT configured to support a pattern forming apparatus MA (e.g., a mask), a projection system PS, and a substrate stage WT configured to support a substrate W.

[0056] The irradiation system IL is configured to adjust the EUV radiation beam B before it is incident on the pattern forming apparatus MA. Furthermore, the irradiation system IL may include a faceted field mirror assembly 10 and a faceted pupil mirror assembly 11. Together, the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11 provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. In addition to or in lieu of the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11, the irradiation system IL may include other mirrors or devices.

[0057] After such adjustment, the EUV radiation beam B interacts with the patterning apparatus MA. As a result of 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 this 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 those on the corresponding features of the patterning apparatus MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS in Figure 1 The diagram shows only two mirrors 13 and 14, but the projection system PS can include a different number of mirrors (e.g., six or eight mirrors).

[0058] The mirrors 10, 11 (or any other mirrors) disposed in the photolithography apparatus LA can be an array of micromirrors. In other words, the mirrors can comprise a large number of smaller mirrors. Each of the smaller mirrors can be independently adjusted to a different position and / or orientation. Therefore, the smaller mirrors can be adjusted to change the properties of the reflected radiation beams B, B'. For example, the direction of the radiation beam B can be changed. Thus, the direction of the patterned radiation beam B' can be changed, causing the irradiation area formed by the radiation beam B' to be moved to a different position. The irradiation area can also be referred to as the projection area.

[0059] The substrate W may include a previously formed pattern. In this case, the photolithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0060] A relative vacuum at pressures far below atmospheric pressure, i.e., a small amount of gas (e.g., hydrogen), can be provided in the radiation source SO, in the irradiation system IL, and / or in the projection system PS.

[0061] The radiation source SO can 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.

[0062] like Figure 1 As shown, sensor S can be supported by a substrate stage WT. Sensor S can be used to perform slit uniformity measurements. Typical slit uniformity measurements are discussed in more detail in [the following section / section / etc.]. Figure 2A middle.

[0063] Figure 2A Example 2100 depicts a known slit uniformity sensor 2120 and an illumination region 2110 of the image plane. The illumination region is composed of, for example... Figure 1 The radiation beam formation of radiation beam B' is depicted in the figure.

[0064] The irradiated area is elongated and has a longer dimension defining a first direction and a shorter dimension defining a second direction. Figure 2A In the examples (and other figures described herein), the first direction corresponds to the x-axis and the second direction corresponds to the y-axis. The irradiation area is arc-shaped. Because the substrate stage can move in the first direction (during the exposure of the substrate to the radiation beam so that the beam can scan across the surface of the substrate), the second direction can be referred to as the scanning direction. The first direction can be referred to as the non-scanning direction.

[0065] The irradiation zone 2110 (and / or radiation beam) can be considered as comprising multiple segments, each segment located at a different coordinate in the non-scanning (x) direction. Each segment can be considered as comprising multiple parts, each part located at a different coordinate in the scanning (y) direction. In other words, each point in a segment will share a similar x-coordinate, and each point in a part will share a similar y-coordinate.

[0066] Figure 3A An exemplary curve 300 is shown, illustrating the intensity of the radiation beam as a function of the y-coordinate. As discussed above, the y-coordinate may correspond to the scanning direction of the substrate stage. The exemplary curve 300 may illustrate the intensity of a single segment of the radiation beam. As shown in the exemplary curve 300, for each segment, the profile of the radiation beam intensity in the scanning (y) direction may be symmetrical about the centroid. For example, the profile has two rising edges 320, 330 symmetrical about the flat region 310. Due to the bow-shaped shape of the radiation beam, the y-coordinate of the first centroid in the first segment may differ from the y-coordinate of the second centroid in the second segment.

[0067] Return to Figure 2A A single sensing element 2121 extends over the entire illumination area 2110 in the scanning (y) direction. That is, because the illumination area is arc-shaped and the slit uniformity sensor 2120 is moved in the non-scanning (x) direction, the single sensing element 2121 needs to extend through the highest y coordinate and the lowest (most negative) y coordinate of the entire illumination area 2110 to be able to measure the intensity of each part in the illumination area.

[0068] The sensing element 2121 can be, for example, a photodiode.

[0069] In use, the slit uniformity sensor 2120 measures the integral of the intensity of the radiation beam in the scanning direction at multiple locations in the non-scanning direction (using a single sensing element 2121). In other words, the slit uniformity sensor 2120 is positioned at multiple locations in the x-direction and at each location is used to measure the intensity of the radiation beam across the entire range of the radiation beam in the y-direction. Therefore, the slit uniformity sensor 2120 provides an intensity measurement for each location in the non-scanning (x) direction. When using the slit uniformity sensor 2120, information relating to the intensity of the radiation beam as a function of the y-coordinate is not provided. Each location in the x-direction may correspond to a different segment of the radiation beam.

[0070] The measurements provided by the slit uniformity sensor 2120 can be used to control the dose supplied to the substrate by the lithography apparatus. For example, the lithography apparatus may be equipped with one or more movable fingers to change the size of the radiation beam and thus the size of the irradiation area 2110. The change in the size of the radiation beam and the irradiation area can occur in the scanning direction. The change in size can change the integral of the intensity in the scanning (y) direction. Therefore, by using the slit uniformity sensor 2120 and the movable fingers, the dose of radiation supplied to the substrate can be controlled and maintained at a consistent value.

[0071] Measurements provided by the slit uniformity sensor 2120 are performed relatively quickly and relatively frequently. However, because the intensity of the radiation beam is integrated in the scanning (y) direction, the measurements have limited applicability.

[0072] Other sensors can be used to measure the properties of the radiation beam. For example, a spot sensor can be used to measure the location of the radiation beam / irradiated area. A spot sensor can also be used to measure the intensity at multiple points within the radiation beam / irradiated area. For instance, a spot sensor can be positioned at multiple points distributed in both the scanning (y) and non-scanning (x) directions and used to measure the intensity of the radiation received at each point. Therefore, while these spot sensors can provide additional information compared to slit uniformity sensors, these measurements are relatively slow because the spot sensor needs to be positioned at multiple points in both directions.

[0073] Figure 2B Example 2200 of a sensor 2220 according to an embodiment of the present invention is depicted. Sensor 2220 can be used for slit uniformity measurement and may be referred to as a uniformity sensor and / or a slit uniformity sensor. Additionally or alternatively, exemplary sensor 2220 can be used to perform other measurements (as described below). Figure 4 and Figure 5 (As described). For example, sensor 2220 can be used to determine the location of the irradiated area.

[0074] Sensor 2220 includes a first sensing element 2221 and a second sensing element 2222. The sensing elements 2221 and 2222 can be, for example, photodiodes.

[0075] The first sensing element 2221 and the second sensing element 2222 are positioned at different locations in the scanning (y) direction. Compared to the slit uniformity sensor 2120 (which measures a single value for each segment of the radiation beam), the sensor 2220 can measure two values ​​for each segment of the radiation beam. The sensing elements 2221 and 2222 together extend over the entire irradiation area 2210 in the scanning direction.

[0076] Each of the two sensing elements 2221, 2222 may be the same or similar in size. In some examples, the two sensing elements 2221, 2222 may be identical (e.g., having the same height and width).

[0077] It should be understood that although sensing elements 2221 and 2222 are in Figure 2B The image is depicted as aligned in the non-scanning (x) direction, but sensing elements 2221, 2222 can be provided in any suitable manner. For example, Figure 2C An alternative exemplary sensor 2320 is depicted (the irradiation area is not shown). Sensor 2320 includes sensing elements 2321, 2322 disposed offset from each other in the non-scanning (x) direction. In some examples, the sensing elements 2321, 2322 are offset such that the sensing elements 2321, 2322 can perform measurements of adjacent segments of the radiation beam. In other examples, the sensing elements can be further offset and spaced apart. Thus, in use, each of the sensing elements 2321, 2322 can simultaneously provide measurements corresponding to different segments of the radiation beam. Advantageously, arranging the sensing elements in this way can, for example, provide space for readout electronics for reading measurements from each sensing element. Thus, by further spacing the sensing elements in the non-scanning (x) direction, the sensing elements can be positioned closer to each other in the scanning (y) direction.

[0078] While the exemplary sensor 2220 includes two sensing elements 2221, 2222, it will be understood that sensor 2220 may include any suitable number of sensing elements. Therefore, in some examples, sensor 2220 may be able to perform a corresponding number of measurements on the radiation beam. For example, Figure 2D An alternative exemplary sensor 2420 is shown, comprising four sensing elements 2421, 2422, 2423, and 2424. In sensor 2420, sensing elements 2421, 2422, 2423, and 2424 are generally aligned with each other (i.e., sharing common coordinates in the non-scanning x-direction). Advantageously, by providing a larger number of sensing elements to sensor 2420 (compared to the sensing elements provided in sensor 2220), sensor 2420 can be used to calibrate a larger number of optical elements at approximately the same time. Figure 2E Another alternative exemplary sensor 2520 is shown. Similar to sensor 2420, sensor 2520 includes four sensing elements 2521, 2522, 2523, and 2524. In sensor 2520, two of the sensing elements 2521 and 2523 are offset relative to the other two sensing elements 2522 and 2524 in the non-scanning x-direction.

[0079] As will be understood, in some examples, a sensor can be configured with multiple sensing elements that share common coordinates in the scanning (y) direction. In other words, the sensor can be segmented not only in the non-scanning (x) direction but also in the scanning (y) direction. Such a sensor can be called a 2D sensor.

[0080] Return to Figure 2B In use, sensor 2220 can be connected with Figure 2A The sensor 2120 is used in a similar manner. Figure 2B Each of the two sensing elements 2221 and 2222 of the sensor 2220 can measure the integral of the intensity of the radiation beam in the scanning direction at multiple locations in the non-scanning direction. In other words, although Figure 2A The sensor 2120 provides a single integral at each position in the non-scanning direction, but Figure 2B The sensor 22220 provides two integrals. The integral of the intensity provided by the two sensing elements 2221, 2222 can correspond to a single portion of a single segment of the radiation beam.

[0081] It can be made by ( Figure 2B The integral of the intensity of radiation measured by the first sensing element 2221 and the second sensing element 2222 of the sensor 2220 is summed together to provide a measurement of the integral of the intensity, which can be combined with the integral of the intensity measured by (the first sensing element 2221 and the second sensing element 2222 of the sensor 2220). Figure 2A The intensity measurement provided by the single sensing element 2121 of the sensor 2120 is used in the same manner. (See below for details.) Figure 4 and Figure 5 As discussed in more detail, in addition to slit uniformity or as an alternative to slit uniformity, sensor 2220 can also be used to determine the properties of the radiation beam.

[0082] Figure 4 This is a flowchart of a method 400 for determining the properties of a radiation beam within a photolithography system. In step 401, multiple intensities are measured for each of multiple segments of the radiation beam. In step 402, the properties of the radiation beam are determined.

[0083] Method 400 may be a method of using sensor 2220 according to embodiments of the present disclosure.

[0084] At step 401, multiple intensities are measured for each of the multiple segments of the radiation beam. For example, sensor 2220 can be moved such that sensor 2220 is positioned at each segment of the radiation beam. The direction of movement of the sensor can be the non-scanning (x) direction of the substrate platform.

[0085] Because sensor 2220 includes multiple sensing elements, multiple intensities can be measured approximately simultaneously. Therefore, each of the multiple intensities can be measured using a different sensing element of sensor 2220, and each of the multiple intensities can correspond to a different portion of the multiple portions of the radiation beam.

[0086] Multiple portions of the radiation beam can correspond to the entire segment of the radiation beam. In other words, for each x-coordinate, the sensing element of sensor 2220 can be used to measure the entire range of the radiation beam in the y-direction. Therefore, the measurements provided by method 400 can be used to determine slit uniformity in a common manner.

[0087] At step 402, the properties of the radiation beam are determined. The properties can be determined using at least one of a plurality of measured intensities for at least one segment of the radiation beam. In some examples, all measured intensities can be used to determine the properties.

[0088] The property (i.e., the property determined at step 402) can be the position of the radiation beam. Alternatively or alternatively (and referred to below) Figure 5 (Discussed in more detail), the property can be the position of a portion of the radiation beam. The position of such a portion of the radiation beam can indicate the orientation or tilt of an optical element within the optical path of the beam. These measurements can allow for the calibration and / or correction of the orientation or tilt of such optical elements.

[0089] In an example where the property is the location of a radiation beam, determining the location of the radiation beam may further include determining a parameter for at least one of a plurality of segments of the radiation beam, depending on at least one of a plurality of measured intensities. For example, the method may include determining the parameter depending on each of the corresponding plurality of measured intensities. The determined parameter may be the difference between a determined first intensity and a determined second intensity.

[0090] For example, when using Figure 2BWhen sensor 2220 is used, the first intensity can be determined as the sum of each intensity measured by the first sensing element 2221. In other words, the first intensity can be the intensity integrated across the entire width of the irradiation area in the non-scanning (x) direction. The first intensity can also be the sum of the intensities measured at the portion of the irradiation area sharing coordinates in the scanning (y) direction. Similarly, the second intensity can be determined as the sum of each intensity measured by the second sensing element 2222. A parameter can be determined as the difference between the determined first intensity and the determined second intensity. The parameter can indicate the offset in the scanning (y) direction between sensor 2220 and the irradiation area formed by the radiation beam. Specifically, the parameter can be zero when the global centroid (i.e., the centroid of the region across the non-scanning y direction where the profile of the radiation beam's intensity in the scanning y direction spans) is aligned with the midpoint between sensing elements 2221 and 2222.

[0091] As an alternative example, the first intensity can be determined as the intensity measured by the first sensing element for a segment of the radiation beam. In other words, the first intensity may correspond only to a segment of the radiation beam and may not span the entire width of the irradiated area in the non-scanning (x) direction. Similarly, the second intensity can be determined as the intensity measured by the second sensing element for a segment of the radiation beam. In other words, the first and second intensities may correspond to a first portion and a second portion of the same segment of the irradiated area. A parameter can be determined as the difference between the determined first intensity and the determined second intensity. In a manner similar to that described above, the parameter can indicate the offset in the scanning (y) direction between the sensor 2220 and the segment of the irradiated area. Multiple first and second intensities can be measured in this manner. Multiple parameters can be measured in this manner. In other words, multiple parameters can be determined, each corresponding to a different segment of the irradiated area. Each parameter can indicate the offset in the scanning (y) direction of a different coordinate in the non-scanning (x) direction. Multiple parameters can be combined, for example, by averaging.

[0092] As an alternative example, when using Figure 2D When using sensor 2420, the first intensity can be determined as the sum of the intensities measured by sensing elements 2421 and 2422. The second intensity can be determined as the sum of the intensities measured by sensing elements 2423 and 2424. In other words, the first intensity can be the sum of the intensities measured by sensing elements 2421 and 2422 corresponding to a first portion of the measured area. The second intensity can be the sum of the intensities measured by sensing elements 2423 and 2424 corresponding to a second portion of the measured area. Each of the first and second portions can have similar dimensions. When using such a sensor, the parameter can be zero when the global centroid is aligned with the midpoint between the first and second portions.

[0093] It will be understood that sensing elements can be used in other ways. For example, when using Figure 2D When using sensor 2420, measurements provided by each of sensing elements 2421, 2422, 2423, and 2424 can be used individually. That is, a first intensity can be the intensity measured by sensing element 2421, a second intensity can be the intensity measured by sensing element 2422, a third intensity can be the intensity measured by sensing element 2423, and a fourth intensity can be the intensity measured by sensing element 2424. Parameters can be determined based on combinations of the first, second, third, and fourth intensities. By using multiple intensities in this way, the resolution of the determined parameters can be improved. Specifically, for an example where the profile of the intensity of the radiation beam in the scanning (y) direction is asymmetrical, the resolution can be improved.

[0094] As another example, parameters can indicate the edge of the radiation beam in the non-scanning (x) direction. For instance, the total intensity can be determined for each segment of the radiation beam. One or more of the total intensities can be used to determine the position of the radiation beam in the non-scanning (x) direction. In other words, a segment with a significantly higher total intensity than its neighboring segments can indicate that the edge of the radiation beam coincides with said segment.

[0095] In the example of the location of a radiation beam, determining the location of the radiation beam may also include using a calibration function to determine the location of the radiation beam based on the determined parameters.

[0096] The method may also include applying a calibration function to the determined parameters. Figure 3B Depiction can be applied to from Figure 2B An exemplary curve 350 of the calibration function 360 for the measurement of sensor 2220. (Example curve 350 is shown.) Figure 3B As can be seen, the calibration function correlates the determined parameters with the determined properties. Figure 3B In the example, the calibration function includes a region (indicated by dashed lines 371, 372) in which the calibration function is approximately linear. As described above, the determined parameter can be the difference between a determined first intensity and a determined second intensity. As an example, applying the calibration function can include applying the calibration function to the intensity difference (i.e., the difference between the determined first intensity and the determined second intensity). By applying the calibration function to the intensity difference, the position of the radiation beam can be determined.

[0097] The method may also include determining a calibration function.

[0098] As an example, determining the calibration function may include using calibration data, which includes multiple determined intensity differences and the measured locations of the radiation beam. A model can be fitted to the calibration data. For example, a least-squares fit can be used to fit the model. The model can be fitted to a region where the relationship between the calibration data is linear. For example, the region could be defined by… Figure 3B The dashed lines 371 and 372 indicate the areas. More typically, determining the calibration function may involve fitting a model to calibration data that includes multiple determined parameters and measured properties.

[0099] The method may also include storing a calibration function in memory. For example, in some embodiments, the calibration function may be stored in memory for future use. For example, in some embodiments, the calibration function may be determined only once. Subsequently, the calibration function can be retrieved from memory.

[0100] The method may also include receiving a calibration function. For example, the calibration function may have been previously determined and stored in a computer-readable storage medium.

[0101] Figure 5 This is a flowchart of a method 500 for determining the calibration of a first optical element. At step 501, the first optical element is adjusted. At step 502, one or more other optical elements are adjusted. At step 503, the position of a portion of the radiation beam is measured. At step 504, the calibration for the first optical element can be determined.

[0102] At step 501, the first optical element is adjusted. The first optical element may be a micromirror of a micromirror array. Adjusting the first optical element may include adjusting its position and / or orientation such that radiation guided by the first optical element forms a portion of a radiation beam illuminating at least one of the plurality of sensing elements. For example, the radiation guided by the first optical element may form the entire radiation beam illuminating at least one of the plurality of sensing elements. In an example where the optical element is a mirror, the guiding radiation may include reflected radiation.

[0103] At step 502, one or more other optical elements are adjusted. These other optical elements may be adjusted such that radiation guided by them does not illuminate at least one of the plurality of sensing elements. In other words, one or more other optical elements are adjusted such that sensing elements illuminated by radiation guided by the first optical element are not illuminated by radiation guided by the other optical elements. Radiation guided by the other optical elements may illuminate other sensing elements. Alternatively, radiation guided by the other optical elements may illuminate, for example, a beam collector.

[0104] At step 503, the position of a portion of the radiation beam is measured. For example, the position of the portion of the radiation beam can be measured using the same or similar method as method 400. For example, the portion of the radiation beam may illuminate two adjacent sensing elements of the sensor, and the difference between the intensities measured by the two sensing elements can be used to determine the position of the portion of the radiation beam.

[0105] At step 504, calibration for the first optical element can be determined. For example, the expected position of a portion of the radiation beam can be compared with the determined position of a portion of the radiation beam. Alternatively, the position / orientation of the first optical element can be determined based on the determined position of a portion of the radiation beam. The determined position / orientation of the first optical element can be compared with the expected orientation of the first optical element.

[0106] Method 500 may further include moving the sensor from a first sensor position to a second sensor position. In other words, corrections based on the determined calibration can be applied to the sensor position / orientation.

[0107] The steps of method 500 can be repeated for the second optical element. In other words, the method allows for the calibration of multiple optical elements. For example, when using sensor 2220, calibration for different optical elements can be determined for each of the different positions in the non-scanning (x) direction. When using a sensor with more sensing elements (such as...) Figure 2D and Figure 2E When using sensors 2420 and 2520, calibration for more than one optical element can be determined for each of the different positions in the non-scanning (x) direction. For example, a first optical element can be used to guide a first portion of the radiation beam to illuminate sensing elements 2421 and 2422, and a second optical element can be used to guide a second portion of the radiation to illuminate sensing elements 2423 and 2424. Therefore, both the first and second optical elements can be calibrated at approximately the same time. As an example, five portions of the radiation beam can be calibrated at approximately the same time using a sensor comprising approximately twenty sensing elements.

[0108] Apart from Figure 4 Method 400 or as Figure 4 Alternatives to method 400 can also be implemented. Figure 5 Method 500. Method 400 can perform slit uniformity measurements while simultaneously determining the properties of the radiation beam. Method 500 can be used to calibrate one or more optical elements. One or more optical elements can be calibrated without determining the properties of the radiation beam or measuring slit uniformity.

[0109] The steps of methods 400 and 500 can be performed in any appropriate order. For example, when using methods such as (e.g.) Figure 2B In the case of sensor 2221 (as depicted), multiple measurements corresponding to a single segment of the radiation beam can be measured simultaneously. As an alternative example, in the case of using a sensor (such as sensor 2320, 2520) in which the first sensing element is offset relative to the second sensor element, the intensity measurement of the first portion of the first segment of the radiation beam can be performed simultaneously (by the first sensor element) and the intensity measurement of the second portion of the second segment of the radiation beam can be performed simultaneously (by the second sensor element).

[0110] While specific references are made to the use of lithography equipment in IC manufacturing in this article, it should be understood that the lithography equipment described herein can have other applications. Possible other applications include manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memories, flat panel displays, liquid crystal display panels (LCDs), thin-film magnetic heads, etc.

[0111] While specific reference may be made herein to embodiments of the invention within the context of a photolithography apparatus, embodiments of the invention can be used in other apparatuses. Embodiments of the invention can form part of any apparatus that forms a mask inspection apparatus, a measurement apparatus, or measures or processes objects such as wafers (or other substrates) or masks (or other patterning apparatuses). These apparatuses can generally be referred to as photolithography tools. Such photolithography tools can be used under vacuum conditions or ambient (non-vacuum) conditions.

[0112] While specific reference has been made above to the use of embodiments of the invention in the context of optical lithography, it will be understood that the invention is not limited to optical lithography and can be used in other applications, such as imprint lithography, where circumstances permit.

[0113] Where circumstances permit, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination of hardware, firmware, and software. 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. A machine-readable medium may include any means for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a 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.). Additionally, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it should be understood that these descriptions are merely for convenience, and these actions are actually caused by a computing device, processor, controller, or other means that execute firmware, software, routines, instructions, etc., and may, in execution, cause actuators or other devices to interact with the physical world.

[0114] While specific embodiments of the invention have been described above, it will be understood that the invention can be practiced in other ways than those described. The above description is intended to be illustrative and not restrictive. Therefore, those skilled in the art will understand that modifications can be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A method for determining the properties of a radiation beam within a photolithography system, the method comprising: For each of a plurality of segments of the radiation beam that have different positions in the first direction: Measure multiple intensities, wherein each of the multiple intensities is measured using a different sensing element of a sensor, wherein each of the multiple intensities corresponds to a different portion of a plurality of portions of the radiation beam that are located at different positions in a second direction, and wherein the plurality of portions of the radiation beam correspond to an entire segment of the radiation beam; and The properties of the radiation beam are determined using at least one of the measured intensities for at least one of the plurality of segments of the radiation beam.

2. The method according to claim 1, wherein, The nature of the radiation beam is its position.

3. The method according to claim 2, wherein, Determining the position of the radiation beam further includes: For at least one of the plurality of segments of the radiation beam, parameters are determined based on at least one of the measured plurality of intensities; and The position of the radiation beam is determined using a calibration function based on the determined parameters.

4. The method of claim 3, further comprising determining the calibration function.

5. The method of claim 4, further comprising storing the calibration function in a memory.

6. The method according to any of the preceding claims further includes receiving the calibration function.

7. The method according to any of the preceding claims, wherein, The nature of the radiation beam is the location of a portion of the radiation beam.

8. The method according to any of the preceding claims, wherein, Measuring multiple intensities for each of a plurality of segments having different positions in a first direction of the radiation beam includes: The first intensity of the first portion is measured using the first sensing element of the plurality of sensing elements of the sensor; and The second intensity of the second portion is measured using the second sensing element of the plurality of sensing elements of the sensor; and The first intensity and the second intensity were measured at approximately the same time.

9. The method according to claim 8, wherein, The first portion and the second portion correspond to the first segment of the radiation beam.

10. The method according to claim 8, wherein: The first portion corresponds to the first segment of the radiation beam; and The second part corresponds to the second segment of the radiation beam.

11. The method according to any of the preceding claims, further comprising: The first optical element is adjusted to a position or orientation such that radiation is guided by the first optical element and forms part of the radiation beam illuminating at least one of the plurality of sensing elements; Adjust one or more other optical elements such that radiation guided by the one or more other optical elements does not illuminate at least one of the plurality of sensing elements; Measure the position of the portion of the radiation beam guided by the first optical element; The position of the portion of the radiation beam guided by the first optical element is used to determine the calibration of the position or orientation of the first optical element.

12. A computer-readable storage medium that, when executed by one or more processors, causes a lithography system to perform the method according to any of the preceding claims.

13. A lithography apparatus configured to perform the method according to any one of claims 1 to 11.

14. A photolithography apparatus or tool, comprising: An optical device arranged to illuminate an illuminating area in an image plane, the illuminating area being elongated and having a longer dimension defining a first direction and a shorter dimension defining a second direction; A substrate stage configured to support a substrate, the substrate stage being movable to position an object thereby supported in the irradiation area; as well as The sensor is supported by the substrate stage and includes a plurality of sensing elements, wherein each of the plurality of sensing elements is disposed at a different position in the second direction, and wherein the extent of the plurality of sensing elements in the second direction is greater than the shorter dimension of the irradiation area.

15. The photolithography apparatus or tool according to claim 14, wherein: The first sensing element and the second sensing element among the plurality of sensing elements are positioned at the same location in the first direction.

16. The photolithography apparatus or tool according to claim 14, wherein: The first sensing element and the second sensing element among the plurality of sensing elements are disposed at different positions in the first direction.

17. A uniformity sensor comprising a plurality of sensing elements for use in a photolithography apparatus.

18. A photolithography apparatus comprising the uniformity sensor according to claim 17.

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