Exposure apparatus, exposure method, production method of article

Abstract

To provide an advantageous technique for correcting aberration of a projection optics system with high precision.SOLUTION: An exposure apparatus for performing an exposure operation of exposing a substrate through a projection optics system includes: a temperature control part for controlling a temperature distribution of an optical element of the projection optics system; and a control part for performing a first treatment of controlling the temperature control part to reduce changes in the aberration of the projection optic system due to the performance of the exposure operation during an exposure operation period where the exposure operation is performed. The control part performs a second treatment for reducing the aberration of the projection optics system by a method different from the first treatment before performing the first treatment in accordance with the detection of a predetermined event before the exposure operation period.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exposure apparatus, an exposure method, and an article manufacturing method.

Background Art

[0002] In the manufacture of articles such as semiconductor devices, an exposure apparatus is used which illuminates a master (reticle or mask) with an illumination optical system and projects the pattern of the master onto a substrate through a projection optical system to expose the substrate. Since the imaging characteristics of the projection optical system vary depending on the irradiation of exposure light, correction of the imaging characteristics is performed in a timely manner.

[0003] For example, Patent Document 1 (Japanese Patent No. 5266641) describes correcting imaging characteristics by applying a temperature distribution to an optical element using a heating element. However, when correcting imaging characteristics using a heating element as in Patent Document 1, if the time constant related to the temperature of the projection optical system is shorter than the time constant related to the heating of the heating element, the accuracy of correction decreases. On the other hand, Patent Document 2 (Japanese Patent No. 5334945) describes a method of starting correction before the imaging characteristics of the projection optical system change.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 2 describes performing control of a correction mechanism in advance based on a change in the gradient of the time-temperature characteristics of imaging characteristics. However, depending on the timing of detecting the change in the gradient, the correction residual may not be sufficiently reduced.

[0006] In light of these problems, the present invention provides an advantageous technique for correcting aberrations in projection optical systems with high precision. [Means for solving the problem]

[0007] According to one aspect of the present invention, an exposure apparatus is provided that performs an exposure operation to expose a substrate through a projection optical system, comprising: a temperature adjustment unit that adjusts the temperature distribution of the optical elements of the projection optical system; and a control unit that performs a first processing operation to control the temperature adjustment unit during the exposure operation period in which the exposure operation is performed so as to reduce the change in aberration of the projection optical system caused by the exposure operation, wherein the control unit performs a second processing operation to reduce the aberration of the projection optical system in a manner different from the first processing operation before performing the first processing operation in response to the detection of a predetermined event before the exposure operation period. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique that is advantageous for correcting aberrations in projection optical systems with high precision. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing the configuration of an exposure apparatus. [Figure 2] A diagram showing an example configuration of an optical element and a temperature control unit. [Figure 3] A diagram illustrating the temperature distribution of a lens heated by a temperature control unit. [Figure 4] A diagram illustrating the distribution of light beam passing through the lens of the projection optical system of a scanning exposure apparatus. [Figure 5] A diagram illustrating the temporal characteristics of astigmatism changes. [Figure 6] A flowchart illustrating the correction process for astigmatism. [Figure 7] A diagram illustrating the effect of astigmatism correction. [Figure 8] This diagram illustrates the effect of astigmatism correction when processing two batches consecutively. [Figure 9] This diagram illustrates the effect of astigmatism correction when processing two batches consecutively. [Figure 10] A diagram showing an example of the configuration of a control system related to substrate transport. [Figure 11] A flowchart illustrating the aberration correction process in the event of an interruption in lot processing. [Figure 12] A flowchart illustrating the aberration correction process when delays occur in the transport of circuit boards during lot processing. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] <First Embodiment> Figure 1 schematically shows the configuration of the exposure apparatus 10 of the first embodiment. The exposure apparatus 10 generally performs an exposure operation in which the substrate 110 is exposed via the projection optical system 107. In the specification and drawings, directions are indicated in an XYZ coordinate system in which the plane parallel to the surface on which the substrate 110 is placed is the XY plane, as shown in Figure 1. The exposure apparatus 10 comprises a light source 102, an illumination optical system 104, a projection optical system 107, a control unit 100, and a temperature control unit 111. In the exposure operation, the illumination optical system 104 illuminates the master plate 106 with light (exposure light) from the light source 102, and the projection optical system 107 projects the pattern of the master plate 106 onto the substrate 110, thereby exposing the substrate 110. The exposure apparatus 10 may be configured as an exposure apparatus that exposes the substrate 110 while the master plate 106 and the substrate 110 are stationary, or it may be configured as an exposure apparatus that exposes the substrate 110 while scanning the master plate 106 and the substrate 110. Generally, the substrate 110 has multiple shot regions, and exposure operations can be performed on each shot region.

[0012] The light source 102 may include, for example, an excimer laser, but may also include other light-emitting devices or an electron gun. The excimer laser can generate light with a wavelength of, for example, 248 nm or 193 nm, but may also generate light with other wavelengths. The projection optical system 107 may include an optical element 109 and a temperature adjustment unit 108 that controls the temperature distribution of the optical element 109. The temperature adjustment unit 108 can change the refractive index distribution and / or the surface shape of the optical element 109 by applying thermal energy to the optical element 109, thereby reducing the change in the optical characteristics of the projection optical system 107. The thermal energy applied by the temperature adjustment unit 108 to the optical element 109 may include positive and negative energies. Applying positive energy to the optical element 109 means heating the optical element 109, and applying negative energy to the optical element 109 means cooling the optical element 109.

[0013] The temperature adjustment unit 108 may be arranged to be in close contact with the optical element 109. In this case, the transfer of thermal energy between the temperature adjustment unit 108 and the optical element 109 is efficient. Alternatively, the temperature adjustment unit 108 may be arranged at a distance from the optical element 109. In this case, it is advantageous in that no mechanical force is applied to the optical element 109 by the temperature adjustment unit 108 and no damage such as scratches is given to the optical element 109 by the temperature adjustment unit 108.

[0014] The temperature adjustment unit 108 is preferably arranged outside the effective diameter (optical path) of the optical element 109 so that the temperature adjustment unit 108 does not interfere with the irradiation of light on the substrate 110. For example, the temperature adjustment unit 108 may be arranged at the flange portion of the lens as the optical element 109, on the front or back surface of the lens. Alternatively, the temperature adjustment unit 108 may be arranged inside the effective diameter within a range that does not affect the optical performance of the projection optical system 107. Examples of such arrangements include, for example, an example of arranging a thin heating wire inside the effective diameter and an example of arranging a heat transfer element with a high light transmittance inside the effective diameter.

[0015] When the temperature adjustment unit 108 is arranged on the outer peripheral side of the optical element 109, the optical element 109 is preferably arranged on or near the pupil plane of the projection optical system 107. However, the temperature adjustment unit 108 may be arranged at a distance from the pupil plane of the projection optical system 107.

[0016] During the period when the exposure operation is being performed and during the period when the exposure operation is not being performed, the temperature adjustment unit 108 can change the thermal energy applied to the optical element 109 in synchronization with the optical characteristics of the projection optical system 107 that change moment by moment. In the present embodiment, the temperature control unit 111 controls the temperature adjustment unit 108. By the temperature control unit 111, the amount and duration of the thermal energy applied to the optical element 109 can be controlled, and thereby the temperature distribution of the optical element 109 can be controlled. Here, the information necessary for controlling the temperature adjustment unit 108 can be generated based on the result of measuring the optical characteristics of the projection optical system 107 on the image plane of the projection optical system 107 (the plane on which the substrate 110 is arranged). Alternatively, the information necessary for controlling the temperature adjustment unit 108 may be determined in advance through measurement or the like. The information necessary for the control in the temperature control unit 111 can be obtained by measuring in advance the amount of aberration generated in the optical element 109 when heat is input under the exposure conditions to be implemented. The control unit 100 determines the thermal energy to be applied to the optical element 109 during exposure based on the information obtained by the measurement, and transmits an instruction including the information to the temperature control unit 111. The temperature control unit 111 applies thermal energy to the temperature adjustment unit 108 with a control value corresponding to the given instruction. The control of the thermal energy applied by the temperature adjustment unit 108 to the optical element 109 can be realized, for example, by controlling the current value applied to the heating wire when the temperature adjustment unit 108 includes a heating wire. Alternatively, the control of the thermal energy applied by the temperature adjustment unit 108 to the optical element 109 may be realized, for example, by controlling the physical distance or the thermal distance between the optical element 109 and the temperature adjustment unit 108.

[0017] The control unit 100 can control the light source 102, the illumination optical system 104, the projection optical system 107, and the temperature control unit 111. The control unit 100 may be composed of, for example, a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), a general-purpose or dedicated computer with a program installed, or a combination of all or part of these. In this embodiment, the control unit 100 and the temperature control unit 111 are configured as separate components, but the control unit 100 may be configured to include the functions of the temperature control unit 111.

[0018] Figure 2 shows an example configuration of the optical element 109 and the temperature control unit 108. Figure 2(a) is a plan view taken from the Z direction, and Figure 2(b) is a cross-sectional view taken along line A-A' in Figure 2(a). The optical element 109 may include a lens 201. The temperature control unit 108 may include a first temperature control unit 203 composed of heating elements 203a and 203b, and a second temperature control unit 204 composed of heating elements 204a and 204b.

[0019] The dashed circle 202 represents the effective ray diameter of lens 201. Outside this effective ray diameter, heating elements 203a and 203b are positioned opposite each other along the Y direction with respect to the center of lens 201, and heating elements 204a and 204b are positioned opposite each other along the X direction with respect to the center of lens 201. Each of the heating elements 203a, 203b, 204a, and 204b may have an arc shape corresponding to one-quarter of the circumference of lens 201. The heating elements 203a, 203b, 204a, and 204b are composed of, for example, flexible cables including heating wires, and generate heat when an electric current is applied to the heating wires, creating a temperature distribution on lens 201.

[0020] The heating elements 203a, 203b, 204a, and 204b may be arranged, for example, at a distance of 10 to 100 μm from the planar portion of the lens 201. The heat generated by the heating elements 203a, 203b, 204a, and 204b may be transferred to the lens 201 via a medium 205 between the heating elements 203a, 203b, 204a, and 204b and the lens 201. The medium 205 may be, for example, a gas such as air or nitrogen. The heating elements 203a, 203b, 204a, and 204b do not need to directly face the lens 201 via the medium 205. The heating elements 203a, 203b, 204a, and 204b may have a structure in which a heating element is sandwiched between metals with high thermal conductivity.

[0021] In the example shown in Figure 2(b), the heating elements 203a, 203b, 204a, and 204b are positioned on the flat surface of the lens 201 (on the side of the illumination optical system 104). However, the heating elements 203a, 203b, 204a, and 204b may also be positioned below the lens 201 (on the side of the substrate 110) or on the edge of the lens 201. The lens 201 may have a heated surface 206 that is heated by the heating elements 203a, 203b, 204a, and 204b. The heated surface 206 may be flat or curved. The heated surface 206 may be, for example, a roughened surface (a frosted glass-like surface).

[0022] Figure 3(a) illustrates the temperature distribution of the lens 201 heated by the second temperature control unit 204. In this case, astigmatism occurs in the positive direction on the surface of the substrate 110. Figure 3(b) illustrates the temperature distribution of the lens 201 heated by the first temperature control unit 203. The temperature distribution in Figure 3(b) is in the opposite phase to the temperature distribution in Figure 3(a). Due to the temperature distribution in Figure 3(b), astigmatism occurs in the negative direction on the surface of the substrate 110. In this way, positive and negative astigmatism can be generated by heating the lens 201 by the first temperature control unit 203 and the second temperature control unit 204. This configuration is advantageous in that it simplifies the configuration of the temperature control unit 108 compared to a configuration that generates positive and negative astigmatism by combining heating and cooling using an element such as a Peltier element.

[0023] Here, we consider the case where the exposure apparatus 10 shown in Figure 1 is a scanning exposure apparatus that scans the original plate 106 and the substrate 110 with a slit-shaped light beam (exposure light) that is long in the X direction. In this case, the intensity distribution of the light beam passing through the projection optical system 107 during exposure operation may be as shown in the shaded area 401 of Figure 4. In this case, the temperature distribution of the lens 201 (optical element 109) caused by the absorption of the light beam will differ in the X direction and the Y direction, which can cause large astigmatism in the projection optical system 107.

[0024] Therefore, a temperature distribution can be applied to the lens 201 by the temperature control unit 108 so as to reduce this astigmatism. The astigmatism generated by the temperature control unit 108 and the astigmatism generated by the lens 201 absorbing the light beam have opposite signs. Thus, the astigmatism generated by the lens 201 absorbing the light beam can be reduced (corrected) by the astigmatism generated by the temperature control unit 108. In the following, unless otherwise specified, "astigmatism" refers to the astigmatism of the projection optical system 107.

[0025] The change in astigmatism (temporal change characteristics) generated by the temperature control unit 108 may differ from the change in astigmatism (temporal change characteristics) generated by the absorption of light by the lens 201. In this case, the change in astigmatism can be controlled by controlling the current supplied to the heating elements 203a, 203b, 204a, and 204b, thereby canceling out the astigmatism generated by the absorption of light by the lens 201 with greater precision.

[0026] Figure 5 illustrates the temporal characteristics of astigmatism changes. In Figure 5, "exposure" refers to the exposure period during which exposure operations are performed, and "non-exposure" refers to the non-exposure period prior to the exposure period during which no exposure operations are performed. The "exposure period" refers to the period from the start of exposure operations on the first substrate in a lot to the end of exposure operations on the last substrate. In reality, the period between shots during which no exposure occurs and the substrate replacement period within a lot are also included in the "exposure period." The "non-exposure period" may include the period from when the equipment is started up or in an idle state until the start of exposure operations on the first substrate in a lot.

[0027] In Figure 5, curve 501 shows the time-series change of astigmatism generated by the lens 201 absorbing heat from exposure light during the exposure operation period after the non-exposure operation period. Ideally, heating the lens 201 by the temperature control unit 108 would generate astigmatism that changes in a curve with the sign reversed from curve 501, thereby reducing or canceling out the astigmatism generated by the lens 201 absorbing heat from exposure light. However, if the lens 201 is continuously heated at a constant temperature by the temperature control unit 108, the resulting astigmatism often changes with a slower time constant than curve 501, as shown by curve 502. Therefore, it is not possible to completely correct (cancel out) the astigmatism shown by curve 501, and a correction residual as shown by curve 503 may occur.

[0028] To compensate for the inability of the temperature control unit 108 to correct the lens 201 by heating to keep up with changes in aberrations during exposure, it is conceivable to perform additional aberration correction processing when the aberration exceeds the permissible value. However, if the frequency of such additional correction processing increases, productivity will decrease. As an alternative, it is conceivable to predict the amount of aberrations that will occur in the two lots using information from the lot being processed and information from the subsequent lot, and to perform correction based on the results of this prediction. However, such predictions are also difficult to perform with high accuracy due to the problems described below.

[0029] Hereinafter, the exposure operation for each substrate in a substrate lot (a unit of multiple substrates processed under the same conditions) is referred to as "lot processing." In the exposure apparatus 10 or its external device (server, etc.), a processing command containing detailed information about the processes to be performed for each lot is created, and lot processing is started when this processing command is fed into the exposure apparatus 10. Hereinafter, this processing command is referred to as an "exposure job." An exposure job is an instruction to start lot processing and includes information on the exposure operation conditions for each substrate in the lot (e.g., exposure amount, field of view, scanning speed, original plate transmittance, etc.). When the control unit 100 receives an exposure job, it performs aberration correction processing, which will be explained in detail below, according to the exposure operation conditions included in the exposure job, and then starts the exposure operation for the lot.

[0030] Since the start timing of the exposure operation in lot processing is planned and determined by the user, the exact time difference between the timing at which the exposure job for that lot processing is submitted and the corresponding start timing of the exposure operation in that lot processing is unknown. Therefore, the start timing of the exposure operation can be determined by at least one of the following: statistically calculating it from the equipment's past operational performance, or predicting it from the equipment status and lot information at the time the exposure job is received. In the following, the start timing of the exposure operation determined based on the time determined in this way will be referred to as the "expected start timing."

[0031] If a subsequent lot processing exposure job is submitted just before the end of the currently processing lot, the lens 201 may not be sufficiently heated before the start of the subsequent lot processing, potentially increasing the correction residual. Similarly, if the next exposure job is submitted while the exposure apparatus 10 is idle, the system may not be able to keep up with the changes in aberration immediately after the lot processing is completed, potentially increasing the correction residual. For example, in Figure 5, timing 504 indicates the timing when the control unit 100 receives the exposure job. Period 505 indicates the period from timing 504, when the exposure job is received, until the exposure operation on the first substrate in that lot begins. In the example in Figure 5, period 505 is approximately 100 seconds. Even if correction is performed by heating the lens 201 by the temperature control unit 108 based on a prediction of the amount of aberration occurring in that lot during such a period, it is difficult for this to keep up with the changes in astigmatism caused by the lens 201 absorbing the light beam during exposure.

[0032] In this embodiment, aberration correction is performed to address such problems. Figure 6 shows a flowchart illustrating the astigmatism correction process in this embodiment. This process is started when the control unit 100 receives an exposure job. In S601, the control unit 100 acquires the device status and lot information. The device status is status information that includes information such as whether or not exposure operation is currently in progress in lot processing, whether or not lot processing has been interrupted, and whether or not there is a substrate transport delay. The lot information is information contained in the received exposure job and may be information on the exposure operation conditions for each substrate in that lot (e.g., exposure amount, field of view, scanning speed, original plate transmittance, etc.).

[0033] In S602, the control unit 100 predicts the amount of aberration based on the device status and lot information acquired in S601, and calculates the amount of heat to be applied to the lens 201 by the temperature control unit 108 in order to correct the predicted aberration. In calculating the amount of heat, constraints may be set so as not to exceed the upper limit of the settable amount of heat in order to prevent failure of the temperature control unit 108.

[0034] In S603, the control unit 100 determines whether the correction by the temperature adjustment unit 108 can track the change in astigmatism caused by heat absorption by the lens 201 during exposure, when the temperature adjustment unit 108 applies the amount of heat calculated in S602 to the lens 201. In one example, if the time difference between the assumed start timing of the exposure operation and the timing of receiving the exposure job is longer than a predetermined threshold, it is determined that tracking is possible. The predetermined threshold may be determined based on the result of the correction by heating by the temperature adjustment unit 108. Alternatively, the predetermined threshold may be determined based on the result of modeling and simulating the astigmatism caused by heating by the temperature adjustment unit 108. Furthermore, the amount of aberration generated by the input lot processing may be predicted, and the predetermined threshold may be dynamically changed based on the predicted amount of aberration generated. In another example, if the difference between the pre-measured value of astigmatism caused by heat absorption by the lens 201 and the amount of aberration predicted in S602 is smaller than a predetermined threshold, it is determined that tracking is possible.

[0035] If tracking is determined to be possible in S603, the process proceeds to S605. In S605, the control unit 100 controls the temperature adjustment unit 108 via the temperature control unit 111 to immediately apply the amount of heating calculated in S602 to the lens 201. This can achieve the desired corrected residual.

[0036] On the other hand, if it is determined in S603 that tracking is impossible, even if the heating amount calculated in S602 is immediately applied to the temperature control unit 108, the desired corrected residual cannot be achieved. Therefore, in this case, the process proceeds to S604. In S604, forced aberration correction is performed. Forced aberration correction may include at least one of the processes listed below. (a) A process that applies a temperature distribution to the lens 201 by light irradiation (i.e., with zero-order light) without using the original plate, thereby generating an aberration with the opposite sign to the aberration generated in the lens 201 by the exposure light. (b) A process in which heating by the temperature control unit 108 generates an aberration that has the opposite sign to the aberration generated in the lens 201 by the exposure light. (c) The lot processing is stopped until the change in astigmatism caused by heating of the lens 201 by the temperature control unit 108 can keep up with the change in astigmatism caused by heat absorption of the lens 201 during exposure. (d) A process of cooling the lens 201 until the change in astigmatism caused by heating of the lens 201 by the temperature control unit 108 can keep up with the change in astigmatism caused by heat absorption of the lens 201 during exposure.

[0037] Referring to Figure 7, an example of the effect of the correction process shown in Figure 6 will be explained. Figure 7 shows an example of improvement in the correction residual when the reception timing of the exposure job is changed, relative to the temporal characteristics of the change in astigmatism shown in Figure 5.

[0038] In the example in Figure 7(a), the timing 704 at which the exposure job is received is earlier than the timing 504 at which the exposure job is received in Figure 5, and the period 705 from timing 704 to the assumed start timing of the exposure operation is approximately 400 seconds. Here, it is assumed that a predetermined threshold for the time difference between the assumed start timing of the exposure operation and the timing of the exposure job reception is set to 300 seconds, which is used to determine whether the correction by heating the lens 201 by the temperature control unit 108 can keep up with the changes in aberration during exposure. In this case, the period 705 is greater than the threshold. Therefore, in S603, it is determined that the correction by applying the amount of heat calculated in S602 to the lens 201 by the temperature control unit 108 can keep up with the temporal changes in astigmatism caused by heat absorption by the lens 201 during exposure. Accordingly, in this case, in S605, the control unit 100 starts the correction process by heating the lens 201 by the temperature control unit 108 immediately after timing 704. As a result, the astigmatism shown by curve 702, which is generated by heating the lens 201 by the temperature control unit 108, corrects the change in astigmatism shown by curve 701, which is generated by heat absorption by the lens 201 during exposure. The corrected residual shown by curve 703 in Figure 7(a) at this time is reduced by an average of 1.5 nm compared to the corrected residual shown by curve 503 in Figure 5.

[0039] In the example of Figure 7(b), the predetermined threshold is set to 300 seconds, as in the explanation for Figure 7(a) above. In Figure 7(b), the exposure job reception timing 709 is approximately 100 seconds earlier than the exposure job reception timing 504 in Figure 5. In other words, the period 710 from the reception timing 709 to the assumed start timing of the exposure operation is approximately 100 seconds longer than the period 505 shown in Figure 5. However, this period 505 is smaller than the threshold. Therefore, in S603, it is determined that the correction by applying the amount of heat calculated in S602 to the lens 201 by the temperature control unit 108 cannot keep up with the temporal changes in astigmatism caused by the lens 201 absorbing the light beam during exposure. Consequently, in this case, in S604, the control unit 100 performs forced aberration correction.

[0040] Here, we assume that as a forced aberration correction, a temperature distribution is applied to the lens 201 with 0th-order light, and a process is performed to generate an aberration in the opposite sign (negative direction) to the amount of aberration generated in the lens 201 by the exposure light. Through this process, as shown by curve 711, an astigmatism of -2.8 nm can be generated. Subsequently, in S605, at the assumed start timing 712 of the exposure operation, the control unit 100 controls the temperature adjustment unit 108 via the temperature control unit 111 to start correction by applying the amount of heating calculated in S602 to the lens 201. As a result, the astigmatism shown by curve 707, which is generated by heating the lens 201 by the temperature adjustment unit 108, follows the change in astigmatism shown by curve 706, which is generated by heat absorption by the lens 201 during exposure, and corrects (cancels out) the astigmatism. The corrected residual shown by curve 708 in Figure 7(b) is reduced by an average of 1.2 nm compared to the corrected residual shown by curve 503 in Figure 5.

[0041] Figure 8 shows an example of improvement in the corrected residual due to the correction process when the exposure job for the next lot processing is started during the lot processing.

[0042] In Figure 8(a), the period from 0 seconds to 2200 seconds shows the same characteristics as in Figure 7(a). Here, a first lot processing is planned, which includes a series of exposure operations on multiple substrates in the first lot, followed by a second lot processing, which includes a series of exposure operations on multiple substrates in the second lot. However, the timing 804 when the control unit 100 receives the exposure job for the second lot is close to the end of the first lot processing and about 100 seconds before the expected start timing of the exposure operation for the second lot. That is, the period 805 from timing 804 to the expected start timing of the exposure operation for the second lot is about 100 seconds. If a predetermined threshold for the time difference between the expected start timing of the exposure operation and the timing of receiving the exposure job is set to 300 seconds, as explained above regarding Figure 7(a), then the period 805 is smaller than the threshold. In this case, at S603, it is determined that the astigmatism generated by the temperature control unit 108 applying the amount of heat calculated in S602 to the lens 201 cannot keep up with the changes in astigmatism generated by the absorption of the light beam by the lens 201 during exposure. Therefore, at S604, the control unit 100 performs forced aberration correction.

[0043] Figure 8(b) shows the result when the second exposure job is received at the same timing 804 as in Figure 8(a), and the forced aberration correction in S604 is performed. Here, as forced aberration correction, a method is implemented to stop lot processing until the change in astigmatism caused by heating the lens 201 by the temperature control unit 108 can keep up with the change in astigmatism caused by heat absorption by the lens 201 during exposure. With this method, lot processing is stopped for a period of approximately 400 seconds 809. This reduces the aberration caused by the exposure of the first lot by 8 nm. Also, during this stop period, heating of the lens 201 by the temperature control unit 108 in S605 may be performed. In this way, a waiting period is provided before starting the second lot processing so that the aberration of the projection optical system 107 can be reduced. As a result, the astigmatism shown by curve 807, which is caused by heating the lens 201 by the temperature control unit 108, follows the change in astigmatism shown by curve 806, which occurs from the exposure start timing 810 of the second lot, and corrects (cancels out) the astigmatism. At this time, the corrected residual during exposure of the second lot, shown by curve 808 in Figure 8(b), can be reduced by an average of 2.7 nm compared to the corrected residual shown by curve 803 in Figure 8(a).

[0044] Figure 9 shows another example of the result of correction processing when an exposure job for the next lot is received while lot processing is in progress. Figure 9 shows the same characteristics for the first lot as in Figure 8, and, as in the example in Figure 8, it is planned to start lot processing for the second lot immediately after the completion of lot processing for the first lot. In Figure 9, the reception timing 904 of the exposure job for the second lot is approximately 400 seconds before the expected start timing of the exposure operation for the second lot. That is, the period 905 from the reception timing 904 to the expected start timing of the exposure operation for the second lot is approximately 400 seconds. If the predetermined threshold for the time difference between the expected start timing of the exposure operation and the reception timing of the exposure job is set to 300 seconds, as explained above for Figures 7(a) and 8(a), then the period 905 is greater than the threshold. In this case, at S603, the astigmatism generated by applying the amount of heat calculated in S602 to the lens 201 by the temperature control unit 108 is determined to be able to follow the change in astigmatism generated by the absorption of the light beam by the lens 201 during exposure. Therefore, in this case, the forced aberration correction at S604 is not performed, and the lens 201 is heated by the temperature control unit 108 as usual at S605. As a result, the astigmatism shown by curve 902, which is generated by heating the lens 201 by the temperature control unit 108, follows the change in astigmatism shown by curve 901, which is generated by the heat absorption of the lens 201 during the exposure of the second lot, and corrects (cancels out) the astigmatism. At this time, the correction residual during exposure of the second lot, shown by curve 903 in Figure 9, can be reduced by an average of 3.0 nm compared to the correction residual shown by curve 803 in Figure 8(a).

[0045] <Second Embodiment> As mentioned above, the start timing of the exposure operation in lot processing is planned and determined by the user; therefore, the exact time difference between the timing at which the exposure job for that lot processing is submitted and the corresponding start timing in the lot processing is unknown. Accordingly, the start timing of the exposure operation can be determined by at least one of the following: statistically calculating it from the equipment's past operational performance, or predicting it from the equipment status and lot information at the time the exposure job is received.

[0046] However, with these methods, it is difficult to determine the exact time in the event of a sudden anomaly. Therefore, in this embodiment, in order to determine the time more accurately, information on the time when the substrate is transported to the exposure apparatus 10 is obtained from the pre-processing device that performs pre-processing on the substrate, and the assumed start timing is determined based on the obtained information. The pre-processing device may be a coating and developing device (coater / developer) that performs a resist (photosensitive agent) coating process on the substrate as a pre-processing step for the exposure process, and a development process as a post-processing step for the exposure process.

[0047] Figure 10 shows an example of the configuration of a control system related to substrate transport. As shown in Figure 10, the exposure apparatus 10 may include a control unit 100 and a transport control device 1001. The configuration of the exposure apparatus 10 other than the control unit 100 and the transport control device 1001 follows that of Figure 1 and are omitted in Figure 10. The transport control device 1001 periodically queries the preprocessing device 1002 for the planned timing of the arrival of the first substrate of the subsequent lot. In response to this query, the preprocessing device 1002 calculates the timing for transporting the substrate to the exposure apparatus 10 based on the substrate processing status and substrate supply status in the preprocessing device 1002, and notifies the transport control device 1001 of this information. The transport control device 1001 transmits the notified information to the control unit 100. Based on the received information on the timing of substrate transport to the exposure apparatus 10, the control unit 100 determines the assumed start timing.

[0048] In this way, by utilizing the information notified from the preprocessor 1002, the expected start timing can be determined with high accuracy.

[0049] <Third Embodiment> Figure 11 is a flowchart showing the aberration correction process when an error occurs during lot processing and the lot processing is interrupted.

[0050] In S1101, the control unit 100 detects an interruption in the currently running lot processing (a series of exposure operations) as a predetermined event. In S1102, the control unit 100 stops the aberration correction processing performed by the temperature control unit 108 during the lot processing. In S1103, recovery processing is performed for the error that occurred. Recovery processing may be performed manually by an engineer or automatically by the exposure device 10.

[0051] In S1104, the control unit 100 determines whether the recovery process in S1103 has been completed. If the recovery process has not been completed, the process returns to S1103; if the recovery process has been completed, the process proceeds to S1105.

[0052] In S1105, the control unit 100 determines the time until lot processing can be resumed. The time until lot processing can be resumed may be determined by using a preset time, or it may be determined based on the nature of the error that caused the interruption of lot processing, the content of the recovery process that was performed, etc.

[0053] In S1106, the control unit 100 predicts the amount of aberration based on the time and lot information determined in S1105, and calculates the amount of heat to be applied to the lens 201 by the temperature control unit 108 in order to correct the predicted aberration.

[0054] The following steps S1107, S1108, and S1109 are the same as the contents of S603, S604, and S605 in Figure 6, respectively.

[0055] <Fourth Embodiment> Figure 12 is a flowchart showing the aberration correction process when a delay occurs in the transport of substrates during lot processing.

[0056] In S1201, the control unit 100 obtains the scheduled time for substrate delivery, for example, from the preprocessing device 1002. In S1202, the control unit 100 determines whether a substrate transport delay has occurred based on the obtained scheduled delivery time. For example, if there is no substrate in the exposure apparatus 10, and the scheduled time for substrate delivery notified by the preprocessing device 1002 is delayed by a predetermined amount of time from the scheduled time, a transport delay is detected as a predetermined event. If no transport delay has occurred, the process returns to S1201. If a transport delay is detected, the process proceeds to S1203.

[0057] In S1203, the control unit 100 predicts the amount of aberration based on the scheduled delivery time and lot information of the substrate acquired in S1201, and calculates the amount of heat to be applied to the lens 201 by the temperature adjustment unit 108 in order to correct the predicted aberration.

[0058] The following steps S1204, S1205, and S1206 are the same as the contents of S603, S604, and S605 in Figure 6, respectively.

[0059] <Embodiment of Article Manufacturing Method> The article manufacturing method according to an embodiment of the present invention is suitable for manufacturing articles such as microdevices such as semiconductor devices and elements having a microstructure. The article manufacturing method of this embodiment includes a step of forming a latent image pattern on a photosensitive agent coated on a substrate using the above-mentioned exposure apparatus (exposure step of exposing the substrate), and a development step of developing the substrate exposed in the exposure step. Furthermore, such an article manufacturing method includes a processing step of processing the substrate developed in the development step. The processing step includes other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method obtains an article from the substrate processed in the processing step. The article manufacturing method of this embodiment is advantageous compared to conventional methods in at least one of the performance, quality, productivity, and production cost of the article.

[0060] <Summary of Embodiments> In the first embodiment, an aberration correction process that can accommodate changes in the reception timing of exposure jobs was described. In the second embodiment, a method for determining the assumed start timing with high accuracy was described. In the third embodiment, an aberration correction process in the event of detection of an interruption in lot processing (a series of exposure operations) was described. In the fourth embodiment, an aberration correction process in the event of a delay in substrate transport during lot processing was described. Any combination of these embodiments is possible.

[0061] The disclosures herein include at least the following exposure apparatus, exposure method, and article manufacturing method. (Item 1) An exposure apparatus that performs an exposure operation in which a substrate is exposed via a projection optical system, A temperature adjustment unit for adjusting the temperature distribution of the optical elements of the projection optical system, The system includes a control unit that performs a first processing to control the temperature adjustment unit so as to reduce the change in aberration of the projection optical system caused by the exposure operation during the exposure operation period in which the exposure operation is performed, The exposure apparatus is characterized in that, in response to the detection of a predetermined event before the exposure operation period, the control unit performs a second process to reduce the aberration of the projection optical system in a manner different from the first process before performing the first process. (Item 2) The exposure apparatus according to item 1, characterized in that the predetermined event is one of the following: receiving an exposure job; detecting a delay in transporting the substrate to the exposure apparatus; detecting an interruption in a series of exposure operations on multiple substrates in a lot; or detecting the resumption of the interrupted exposure operation. (Item 3) The exposure apparatus according to item 1 or 2, characterized in that the temperature control unit is located outside the effective diameter of the optical element and is configured to partially apply heat to the optical element by the first process. (Item 4) The exposure apparatus according to any one of items 1 to 3, characterized in that the second process includes controlling the temperature distribution applied to the optical element by light irradiation, providing a waiting period before entering the exposure operation period, or cooling the optical element. (Item 5) The aforementioned predetermined event is the receipt of an exposure job. The control unit performs the second process when the time difference between the expected start timing of the exposure operation and the timing of receiving the exposure job is less than a predetermined threshold. An exposure apparatus according to any one of items 1 to 4, characterized by the features described above. (Item 6) The aforementioned predetermined event is the receipt of an exposure job. When a first lot process, which includes a series of exposure operations on multiple substrates in a first lot, and a second lot process, which includes a series of exposure operations on multiple substrates in a second lot, are planned to be performed after the first lot process, the control unit shall, if the time difference between the expected start timing of the second lot process and the timing of receiving the exposure job for the second lot process is smaller than a predetermined threshold, provide a waiting period before starting the second lot process to reduce the aberrations of the projection optical system. An exposure apparatus according to any one of items 1 to 5, characterized by the features described herein. (Item 7) The exposure apparatus according to item 6, characterized in that the control unit acquires information on the time when the substrate is transported from the preprocessing device that performs preprocessing on the substrate to the exposure apparatus, and determines the assumed start timing based on the acquired information. (Item 8) The exposure apparatus according to any one of items 1 to 7, characterized in that the first and second processes are processes for reducing astigmatism as the aberration. (Item 9) An exposure method that performs an exposure operation in which a substrate is exposed via a projection optical system, A first step is to perform a first processing in which a temperature control unit controls the temperature distribution of the optical elements of the projection optical system so as to reduce the change in aberration of the projection optical system caused by the exposure operation during the exposure operation period, A second step is performed before the first step in response to a predetermined event being detected before the exposure operation period, to reduce the aberration of the projection optical system in a manner different from the first step, An exposure method characterized by having the following: (Item 10) A method for manufacturing articles, An exposure step in which the substrate is exposed by the exposure method described in item 9, A developing step for developing the substrate exposed in the exposure step, The process includes processing the substrate developed in the development step, A method for manufacturing an article, characterized by obtaining an article from the substrate processed in the aforementioned processing step.

[0062] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0063] 10: Exposure apparatus, 100: Control unit, 104: Illumination optical system, 107: Projection optical system, 108: Temperature control unit, 109: Optical element, 111: Temperature control unit

Claims

1. An exposure apparatus that performs an exposure operation to expose a substrate via a projection optical system, a temperature adjusting unit that adjusts the temperature distribution of optical elements of the projection optical system; a control unit that performs a first process to control the temperature adjustment unit during an exposure operation period in which the exposure operation is performed so that a change in aberration of the projection optical system due to the exposure operation is reduced, an exposure apparatus characterized in that the control unit performs a second process for reducing aberrations of the projection optical system by a method different from the first process before performing the first process in response to detection of a predetermined event before the exposure operation period.

2. 2. The exposure apparatus according to claim 1, wherein the specified event is one of: receiving an exposure job; detecting a delay in transporting the substrate to the exposure apparatus; detecting an interruption of a series of exposure operations for multiple substrates in a lot; and detecting a resumption of the interrupted exposure operation.

3. 2. The exposure apparatus according to claim 1, wherein the temperature adjustment unit is arranged outside an effective diameter of the optical element, and is configured to apply heat partially to the optical element by the first process.

4. 4. The exposure apparatus according to claim 3, wherein the second process includes any one of controlling a temperature distribution imparted to the optical element by light irradiation, providing a waiting period before entering the exposure operation period, and cooling the optical element.

5. the predetermined event is receiving an exposure job; the control unit performs the second process when a time difference between the expected start timing of the exposure operation and the reception timing of the exposure job is smaller than a predetermined threshold value.

2. An exposure apparatus according to claim 1.

6. the predetermined event is receiving an exposure job; When it is planned to execute a first lot process including a series of exposure operations on a plurality of substrates in a first lot, and a second lot process including a series of exposure operations on a plurality of substrates in a second lot after the first lot process, the control unit provides a waiting period to reduce aberrations of the projection optical system before starting the second lot process if the time difference between the expected start timing of the second lot process and the reception timing of an exposure job for the second lot process is smaller than a predetermined threshold value.

2. An exposure apparatus according to claim 1.

7. The exposure apparatus according to claim 6, wherein the control unit acquires information about the time at which the substrate is transported from a pre-processing device that performs pre-processing on the substrate to the exposure apparatus, and determines the expected start timing based on the acquired information.

8. 8. The exposure apparatus according to claim 1, wherein the first processing and the second processing are processing for reducing astigmatism as the aberration.

9. An exposure method for performing an exposure operation to expose a substrate via a projection optical system, comprising: a first step of performing a first process of controlling a temperature distribution of an optical element of the projection optical system by a temperature adjustment unit so that a change in aberration of the projection optical system due to the exposure operation is reduced during an exposure operation period in which the exposure operation is performed; a second step of performing a second process before the first step in response to detection of a predetermined event before the exposure operation period, for reducing aberration of the projection optical system by a method different from the first process; An exposure method comprising:

10. 1. A method of manufacturing an article, comprising: an exposure step of exposing a substrate by the exposure method according to claim 9; a developing step of developing the substrate exposed in the exposure step; a processing step of processing the substrate developed in the developing step, A method for manufacturing an article, characterized in that an article is obtained from the substrate processed in the processing step.

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