JP7615005B2 - Exposure apparatus, exposure method, and article manufacturing method - Google Patents

Description

The present invention relates to an exposure apparatus, an exposure method, and a method for manufacturing an article.

A scanning exposure apparatus is known as a lithography apparatus used in the manufacturing process of semiconductor devices and the like, which exposes the substrate while scanning the original and the substrate relatively through a projection optical system, thereby transferring the pattern of the original onto the resist on the substrate as a latent image pattern. In recent years, scanning exposure apparatuses have sometimes used substrates coated with thick resist, and multiple exposures can be performed on such substrates to increase the depth of field (DOF). Multiple exposure refers to performing multiple scanning exposures on the same shot area on the substrate.

Incidentally, scanning exposure devices may use a light source that periodically emits pulsed light. In this case, periodic exposure unevenness in the scanning direction may occur on the shot area of the substrate during each scanning exposure. Patent Document 1 describes a method of determining in advance the relationship between the number of pulses irradiated to the substrate while the substrate moves a unit amount in the scanning direction and the exposure unevenness, and setting the number of pulses based on this relationship so as to reduce the exposure unevenness on the substrate. The number of pulses irradiated to the substrate while the substrate moves a unit amount in the scanning direction is expressed in units of, for example, [pulse/mm], and may be referred to below as the number of irradiation pulses.

JP 2010-021211 A

In the method described in Patent Document 1, multiple candidates for the number of irradiation pulses that can reduce exposure unevenness are determined based on the relationship between the number of irradiation pulses and exposure unevenness, and one irradiation pulse number is selected from the multiple candidates. In this method, the greater the number of irradiation pulses selected from the multiple candidates, the smaller the exposure unevenness can be. However, if the number of irradiation pulses is increased, it is necessary to reduce the scanning speed of the substrate stage due to restrictions on the period of the pulsed light that can be emitted from the light source, which can be disadvantageous in terms of throughput. Therefore, in a scanning exposure apparatus, a method is desired that can reduce exposure unevenness even when the number of irradiation pulses is reduced.

Therefore, the present invention aims to provide an exposure device that is advantageous for reducing exposure unevenness that occurs on a substrate.

In order to achieve the above-mentioned object, an exposure apparatus as one aspect of the present invention is an exposure apparatus that performs multiple scanning exposures on the same shot area on a substrate, and is equipped with a projection optical system that projects pulsed light periodically emitted from a light source unit onto the substrate , and a control unit that controls a signal related to the timing when the light source unit starts to emit the pulsed light, and is characterized in that the control unit controls the signal related to the timing in accordance with the period of the exposure unevenness so that exposure unevenness that occurs periodically on the shot area in each of the multiple scanning exposures is reduced by the multiple scanning exposures.

Further objects and other aspects of the present invention will become apparent from the following description of preferred embodiments thereof with reference to the accompanying drawings.

The present invention can provide, for example, an exposure device that is advantageous for reducing exposure unevenness that occurs on a substrate.

FIG. 1 is a diagram showing an example of the configuration of an exposure apparatus. FIG. 1 is a schematic diagram of scanning exposure using a specific pulse intensity distribution shape, and a diagram showing the relationship between the number of irradiation pulses and exposure unevenness. FIG. 13 is a diagram showing the relationship between the position of a shot area in the scanning direction and exposure unevenness. FIG. 13 is a diagram showing the relationship between the position of a shot area in the scanning direction and exposure unevenness. FIG. 13 is a diagram showing an example of the emission start timing for each scanning exposure in the case where the number of scanning exposures in multiple exposure is two; FIG. 13 is a diagram showing an example of first exposure unevenness occurring in each scanning exposure. FIG. 13 is a diagram showing an example in which first exposure unevenness is reduced in the first embodiment; FIG. 11 is a diagram showing an example in which second exposure unevenness is reduced in the second embodiment; FIG. 13 is a diagram showing an example in which the first exposure unevenness and the second exposure unevenness are reduced in the third embodiment;

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

<Example of the configuration of the exposure apparatus>
1 is a diagram showing an example of the configuration of an exposure apparatus 100 according to an embodiment of the present invention. In the following description, the direction parallel to the optical axis of light emitted from the projection optical system 14 and incident on the substrate 16 is defined as the Z-axis direction, and two directions perpendicular to each other in a plane perpendicular to the optical axis are defined as the X-axis direction and the Y-axis direction. Note that in the following description, when the term "X-axis direction" is used, it can be defined as including the +X direction and the -X direction. The same applies to the "Y-axis direction" and the "Z-axis direction". In this embodiment, the Y-axis direction will be described as the scanning direction.

The exposure apparatus 100 of this embodiment is a step-and-scan type exposure apparatus that exposes the substrate 16 while scanning the original 12 and the substrate 16 relative to one another, thereby transferring the pattern of the original 12 to the resist on the substrate as a latent image pattern. Such an exposure apparatus 100 is also called a scanning exposure apparatus or a scanner. In this embodiment, the original 12 is, for example, a quartz mask (reticle), and a circuit pattern to be transferred to each of a plurality of shot areas on the substrate 16 is formed. The substrate 16 is a wafer coated with resist (photoresist), and a single crystal silicon substrate, for example, can be used.

The light beam emitted from the light source unit 1 passes through the beam shaping unit 2, is shaped into a predetermined shape, and is incident on the incident surface of the optical integrator 3. The light source unit 1 includes, for example, multiple laser light sources, and periodically emits pulsed light so that multiple pulsed lights are superimposed and irradiated onto the substrate 16 while the substrate 16 is scanned by a unit amount. The optical integrator 3 is also composed of multiple tiny lenses (for example, fly-eye lenses), and a large number of secondary light sources are formed near the light emission surface.

The aperture turret 4 limits (defines) the size of the surface of the secondary light source by a predetermined aperture. The aperture turret 4 is arranged with a numbered aperture (illumination mode number), such as aperture apertures with different circular aperture areas so that multiple types of coherence factor σ values can be set, a ring-shaped aperture for annular illumination, and a quadrupole aperture. The aperture required to change the shape of the incident light source of the illumination light is selected and inserted into the optical path. The light amount detection unit 6 includes, for example, a photoelectric conversion element, detects a portion of the pulsed light reflected by the half mirror 5 as the light amount (light intensity) per pulse, and outputs an electrical signal (detection signal) indicating the detection result to the light amount calculation unit 22.

The condenser lens 7 illuminates the blind 8 with a light beam from a secondary light source near the exit surface of the optical integrator 3 using Kohler illumination. A slit 9 is disposed near the blind 8, and shapes the profile of the light illuminating the blind 8 into a rectangular or arc shape. The light that passes through the blind 8 and the slit 9 (also called slit light) is imaged, via a mirror 10 and a condenser lens 11, on the master 12 on which a pattern is formed, with uniform illuminance and angle of incidence. The master 12 is disposed on a conjugate plane of the blind 8. The opening area of the blind 8 is similar in shape to the light irradiation area of the master 12 in terms of the optical magnification ratio. During scanning exposure, the blind 8 is synchronously scanned with the master stage 13 at the optical magnification ratio while blocking light outside the irradiation area of the master 12.

The original 12 is held by the original stage 13. The light that passes through the original 12 passes through the projection optical system 14 as light (pattern light) reflecting the pattern formed on the original 12, and is imaged in an exposure angle area on a plane optically conjugate with the pattern surface of the original 12. The focus detection system 15 detects the height and inclination of the exposure surface of the substrate 16 held by the substrate stage 18. During scanning exposure, the original stage 13 and the substrate stage 18 are synchronously scanned at a speed ratio according to the projection magnification of the projection optical system 14 while controlling the substrate stage 18 based on information from the focus detection system 15 so that the exposure surface of the substrate 16 is positioned on the imaging plane of the projection optical system 14. As a result, the substrate 16 is exposed, and the pattern of the original 12 can be transferred to the resist on the substrate 16 as a latent image pattern.

The energy measuring unit 17 is provided on the substrate stage 18 and measures the amount of light (light intensity) emitted from the projection optical system 14. The energy measuring unit 17 is composed of, for example, a line sensor aligned along the scanning direction of the substrate 16, or a photosensor movable in the scanning direction of the substrate 16, and is arranged so that its light receiving surface approximately coincides with the image plane of the projection optical system 14. This makes it possible to measure the light intensity distribution per pulse of light on the image plane of the projection optical system 14. The light intensity distribution measured by the energy measuring unit 17 may be understood to represent the light intensity distribution per pulse of light irradiated to the substrate 16.

Next, the configuration of the control system 20 in the exposure apparatus 100 of this embodiment will be described. The control system 20 of this embodiment can include a stage control unit 21, a light intensity calculation unit 22, a light source control unit 23, an information input unit 24, a timing determination unit 25, and a main control unit 26.

The stage control unit 21 controls the driving (Y-axis direction) of the original stage 13 and the substrate stage 18, thereby controlling the synchronous scanning of the original 12 and the substrate 16 in the scanning exposure. The stage control unit 21 may also control the driving (Z-axis direction) of the substrate stage 18 so that the exposure surface of the substrate 16 is positioned on the imaging plane of the projection optical system 14. Furthermore, based on the electrical signal received from the light intensity detection unit 6, the light intensity calculation unit 22 converts the intensity of the pulsed light emitted from the light source unit 1 into a logical value so that it becomes the target intensity, and outputs the converted value to the light source control unit 23.

The light source control unit 23 controls the pulse oscillation frequency and pulse output energy of the light source unit 1 by outputting a trigger signal and/or an applied voltage signal according to the desired pulse light amount. The light source control unit 23 can determine the trigger signal and/or the applied voltage signal based on the light amount output value of the light amount detection unit 6 acquired from the light amount calculation unit 22 and the exposure parameter information (target integrated exposure amount, required integrated exposure amount accuracy, aperture shape, etc.) held by the main control unit 26. The exposure parameter information is input to the main control unit 26 from the information input unit 24 as a man-machine interface or media interface and stored therein.

The timing determination unit 25 acquires a part of the exposure parameter information from the information input unit 24 via the main control unit 26, and based on this information, determines the exposure start timing for the target shot area for scanning exposure among the multiple shot areas on the substrate 16. The exposure start timing may be understood as the timing (emission start timing) at which the light source unit 1 starts emitting periodic pulsed light during scanning exposure, and may be simply referred to as "emission start timing" below. For example, the timing determination unit 25 can control the time interval from detecting the gate signal supplied from the stage control unit 21 to starting to output a trigger signal to the light source unit 1 to instruct the start of emission of periodic pulsed light. The gate signal is a signal indicating that the substrate 16 has been placed at a target position where scanning exposure can be started by controlling the driving of the substrate stage 18, and can be output from the stage control unit 21. The timing determination unit 25 may be configured as a part of the light source control unit 23.

The main control unit 26 is configured by a computer having a processor such as a CPU and a storage device such as a memory, and controls each part of the exposure apparatus 100. For example, the main control unit 26 acquires exposure parameters acquired from the information input unit 24, device-specific parameters, light amount data detected by the light amount detection unit 6, and light amount data measured by the energy measurement unit 17. Then, based on the acquired information and data, it calculates various information necessary for scanning exposure and controls the light source control unit 23 and the stage control unit 21. In this embodiment, the stage control unit 21, the light amount calculation unit 22, the light source control unit 23, and the timing determination unit 25 are configured separately from the main control unit 26, but may be configured as part of the main control unit 26. In other words, the stage control unit 21, the light amount calculation unit 22, the light source control unit 23, the timing determination unit 25, and the main control unit 26 in FIG. 1 may be understood as a whole as a control unit.

<About uneven exposure>
In the exposure apparatus 100, a pattern may be formed on the substrate 16 coated with a thick resist, and in this case, multiple exposures may be performed to expand the depth of field (DOF). Multiple exposures are performed multiple times on the same shot area (target shot area) on the substrate 16. However, when a light source unit 1 that periodically emits pulsed light is used, periodic exposure unevenness in the scanning direction may occur on the target shot area in each of the multiple scanning exposures. Therefore, in the exposure apparatus 100, it is required to reduce the exposure unevenness that occurs periodically on the target shot area. Here, the exposure unevenness is defined as the deviation (deviation) of the integrated exposure amount of the substrate (target shot area) from the target exposure amount, and can be expressed in units of "%".

Figure 2(a) shows a schematic diagram of scanning exposure using a specific pulse intensity distribution shape, and Figure 2(b) shows the relationship between the number of irradiation pulses and exposure unevenness. The number of irradiation pulses is defined as the number of pulsed light beams superimposed and irradiated onto the substrate 16 while the substrate 16 scans a unit amount (unit distance), and can be expressed in units of [pulse/mm], for example. In the example of Figure 2(a), the number of irradiation pulses is "6". The pulse intensity distribution shape is defined as the shape of the intensity distribution of one pulsed light beam output from the light source unit 1 or irradiated onto the substrate, and is a trapezoid in the example of Figure 2(a).

The integrated exposure amount at each position in the scanning direction is the integrated value of the energy of multiple pulsed lights, as shown by hatching in FIG. 2(a), and the amount of exposure unevenness (i.e., the deviation of the integrated exposure amount from the target exposure amount) is determined by the pulse intensity distribution shape and the number of irradiation pulses. Specifically, as shown in FIG. 2(b), the greater the number of irradiation pulses, i.e., the higher the pulse density per unit amount in the scanning direction, the smaller the effect of the sloped portion of the trapezoidal pulse intensity distribution shape, and the more exposure unevenness can be reduced. In the example of FIG. 2(b), it is confirmed that the exposure unevenness is significantly reduced when the number of irradiation pulses is 4, 6, and 8 [pulse/mm].

Figure 3 shows the relationship between the position of the shot area in the scanning direction and the exposure unevenness obtained when one scanning exposure is performed under each condition of the irradiation pulse number of 4, 6, and 8 [pulse/mm]. As shown in Figure 3, the maximum value of the exposure unevenness generated on the shot area by one scanning exposure is 0.05 [%] or more when the irradiation pulse number is 4 [pulse/mm], about 0.03 [%] when it is 6 [pulse/mm], and 0.01 [%] or less when it is 8 [pulse/mm]. In other words, it can be seen that the maximum value of the exposure unevenness decreases as the irradiation pulse number is increased. In addition, the exposure unevenness generated on the shot area by one scanning exposure has a periodicity that depends on the irradiation pulse number, and when the irradiation pulse number is 4 [pulse/mm], it becomes a striped pattern with a period of 250 [μm].

Here, the amount of exposure unevenness (maximum value) can be reduced by increasing the number of irradiation pulses as shown in FIG. 3. However, when the number of irradiation pulses is increased, it is necessary to reduce the scanning speed of the substrate stage 18 due to restrictions on the emission period of the pulsed light that can be emitted from the light source unit 1, which may be disadvantageous in terms of throughput. Therefore, a method that can reduce exposure unevenness even when the number of irradiation pulses is reduced is desired. Therefore, in this embodiment, multiple exposure in which multiple scanning exposures are performed on the same shot area is used to reduce exposure unevenness occurring in the shot area. Specifically, the emission start timing is changed in the multiple scanning exposures according to the period of exposure unevenness so that the exposure unevenness that occurs periodically on the shot area in each of the multiple scanning exposures is at least partially offset by the multiple scanning exposures. This makes it possible to reduce exposure unevenness occurring in the shot area throughout the multiple exposures (multiple scanning exposures). Below, an example for reducing exposure unevenness is described.

Example 1
FIG. 4 shows the relationship between the position of the target shot area in the scanning direction and the exposure unevenness obtained when one scanning exposure is performed with the irradiation pulse light at 4 [pulse/mm]. In the above-mentioned FIG. 3, only the exposure unevenness (first exposure unevenness) occurring according to the light emission period of the pulse light emitted from the light source unit 1 is shown, but in reality, as shown in FIG. 4, the exposure unevenness (second exposure unevenness) occurring at a period shorter than the first exposure unevenness may be superimposed on the first exposure unevenness. The first exposure unevenness occurs according to the light emission period of the pulse light emitted from the light source unit 1, and in the example of FIG. 4, it may occur on the shot area at a period (spatial period) of 250 [μs]. On the other hand, the second exposure unevenness occurs at a period shorter than the first exposure unevenness due to the optical integrator 3, and in the example of FIG. 4, it may occur on the shot area at a period (spatial period) of 35 [μm]. In this embodiment 1, an example of reducing the first exposure unevenness is described, an example of reducing the second exposure unevenness is described in embodiment 2, and an example of reducing both the first exposure unevenness and the second exposure unevenness is described in embodiment 3.

First, the process of the timing determination unit 25 for reducing the first exposure unevenness will be described. The timing determination unit 25 acquires information related to the multiple exposure via the main control unit 26. The information related to the multiple exposure may include, for example, information indicating the number of scanning exposures in the multiple exposure (the number of scanning exposures performed on the same shot area) and information indicating the period (spatial period) of the exposure unevenness to be reduced. The information indicating the number of scanning exposures in the multiple exposure is input by the user via the information input unit 24 and stored in the main control unit 26, and the timing determination unit 25 may acquire the information stored in the main control unit 26 from the main control unit 26. In addition, the information indicating the period of the exposure unevenness to be reduced is obtained from experiments or simulations performed in advance and stored in the main control unit 26, and the timing determination unit 25 may acquire the information stored in the main control unit 26 from the main control unit 26.

Next, the timing determination unit 25 determines the emission start timing for each of the multiple scanning exposures in the multiple exposure based on the acquired information on the multiple exposure. The emission start timing may be understood as the timing at which the light source unit 1 starts emitting periodic pulsed light in response to detection of the gate signal supplied from the stage control unit 21, as described above. In other words, the emission start timing may be understood as the time (period) from detection of the rising edge of the gate signal supplied from the stage control unit 21 to the start of emission of periodic pulsed light in the light source unit 1. The timing determination unit 25 may also determine the amount of time shift of the emission start timing in the multiple scanning exposures in the multiple exposure. As an example, when the number of scanning exposures in the multiple exposure is two, the timing determination unit 25 may determine the amount of time shift of the emission start timing in the second scanning exposure relative to the emission start timing in the first scanning exposure. Information on the emission start timing in each scanning exposure determined by the timing determination unit 25 is supplied to the light source control unit 23. The light source control unit 23 then controls the trigger signal based on the emission start timing information, thereby controlling the emission of pulsed light from the light source unit 1 during each of the multiple scanning exposures.

Figure 5 shows an example of the emission start timing for each scanning exposure when the number of scanning exposures in multiple exposure is two. The emission start timing shown in Figure 5 may be understood as the output timing of a trigger signal supplied from the light source control unit 23 to the light source unit 1. The trigger signal may be a signal (a light emission command to the light source unit 1) supplied to the light source unit 1 to cause the light source unit 1 to emit pulsed light. In the example of Figure 5, the timing determination unit 25 determines the time (emission start timing) from detecting the gate signal to starting output of the trigger signal to the light source unit 1 to be time A for the first scanning exposure, and to be time A plus a time shift amount B for the second scanning exposure.

Next, a method for determining the emission start timing for each of the multiple scanning exposures so as to reduce the first exposure unevenness in the entire multiple exposure will be described. In the case of this embodiment 1, the timing determination unit 25 changes the emission start timing by multiple scanning exposures according to the period of the first exposure unevenness so that the first exposure unevenness is at least partially offset by the multiple scanning exposures. Specifically, when the number of scanning exposures in the multiple exposure is N, the timing determination unit 25 changes the emission start timing by multiple scanning exposures by a time equivalent to 1/N of the period of the first exposure unevenness. Here, as the information indicating the period of the first exposure unevenness, information obtained from an experiment or simulation performed in advance may be used, but information indicating the emission period of the pulsed light emitted from the light source unit 1 may also be used. This is because the period of the first exposure unevenness corresponds to the emission period of the pulsed light emitted from the light source unit 1.

Figure 6 shows an example of the first exposure unevenness that occurs in each scanning exposure when the number of scanning exposures in multiple exposure is two. Figure 6 shows a case where the irradiated pulse light is 4 [pulse/mm] and the light emission period of the pulse light emitted from the light source unit 1 is 250 [μs] (i.e., the pulse oscillation frequency is 4 [kHz]). The first exposure unevenness that occurs in the target shot area due to the first scanning exposure is shown by a solid line, and the first exposure unevenness that occurs in the target shot area due to the second scanning exposure is shown by a dashed line.

In the example of FIG. 6, the timing determination unit 25 determines the emission start timing in the second scanning exposure to be shifted by a time equivalent to half the period of the first exposure unevenness (125 [μm]) with respect to the emission start timing in the first scanning exposure. In other words, the time shift amount B of the emission start timing in the second scanning exposure relative to the emission start timing in the first scanning exposure is determined to be a time equivalent to half the period of the first exposure unevenness (125 [μm]). Here, since the first exposure unevenness occurs according to the emission period of the pulsed light emitted from the light source unit 1, the time shift amount B can be determined based on the emission period of the pulsed light emitted from the light source unit 1 and the number of scanning exposures in the multiple exposure. In other words, the time shift amount B can be determined to be 125 [μs], which is half (1/2) of the emission period of the pulsed light emitted from the light source unit 1.

This allows the phase of the first exposure unevenness (position of peaks and valleys) generated in the second scanning exposure to be shifted by 180 degrees from the phase of the first exposure unevenness (position of peaks and valleys) generated in the first scanning exposure. As a result, the first exposure unevenness generated in the first scanning exposure and the first exposure unevenness generated in the second scanning exposure at least partially cancel each other out, so that the first exposure unevenness can be reduced throughout the multiple scanning exposures in the multiple exposure, as shown in Figure 7. Figure 7 shows the first exposure unevenness generated in the first scanning exposure and the first exposure unevenness generated in the second scanning exposure superimposed on each other.

Here, in the above, the case where the number of scanning exposures in the multiple exposure is two is exemplified, but even if the number of scanning exposures is three or more, the effect of reducing the first exposure unevenness can be obtained in the same way. For example, if the number of scanning exposures in the multiple exposure is N, the time shift amount Sn [μs] of the emission start timing in the multiple scanning exposures can be determined as 1/N of the light emission period Tp [μs] of the pulsed light emitted from the light source unit 1. In addition, if the emission start timing in the first scanning exposure is used as a reference, the time shift amount Sn [μs] of the emission start timing in the nth scanning exposure can be determined as (n-1)/N of the light emission period Tp [μs] of the pulsed light emitted from the light source unit 1. The following is an example of calculating the time shift amount Sn when Tp=250 [μs] and N=3, 4. Note that n is any integer (natural number) from 1 to N, and the time shift amount Sn is the same as the time shift amount B in FIG. 5.
When Tp = 250 and N = 3: n = (2, 3), Sn = (83, 167)
For Tp = 250 and N = 4: n = (2, 3, 4), Sn = (63, 125, 188)

Example 2
In this embodiment 2, an example of reducing the second exposure unevenness will be described. As described above, the second exposure unevenness occurs on the target shot area at a period shorter than the period of the first exposure unevenness due to the optical integrator 3. In this embodiment 2, as in the embodiment 1, the timing determination unit 25 obtains information regarding the multiple exposure and determines the emission start timing for each of the multiple scanning exposures in the multiple exposure based on the information. However, in this embodiment 2, information indicating the period of the second exposure unevenness is used as information indicating the period of the exposure unevenness to be reduced. The information indicating the period of the second exposure unevenness is obtained by an experiment or simulation performed in advance and stored in the main control unit 26, and the timing determination unit 25 can obtain the information stored in the main control unit 26 from the main control unit 26.

In the case of the second embodiment, the timing determination unit 25 changes the injection start timing by multiple scanning exposures according to the period of the second exposure unevenness so that the second exposure unevenness is at least partially offset by multiple scanning exposures. Specifically, when the number of scanning exposures in the multiple exposure is N, the timing determination unit 25 changes the injection start timing by multiple scanning exposures by a time equivalent to 1/N of the period of the second exposure unevenness. For example, assume that the number of scanning exposures N in the multiple exposure is 2, and the period Te of the second exposure unevenness is 35 [μm]. In this case, the timing determination unit 25 determines the injection start timing in the second scanning exposure to be shifted by a time equivalent to half the period of the second exposure unevenness (17.5 [μm]) with respect to the injection start timing in the first scanning exposure. In other words, the time shift amount Sn of the emission start timing in the second scanning exposure relative to the emission start timing in the first scanning exposure is determined to be a time equivalent to half the period of the second exposure unevenness (17.5 μm).

This allows the phase of the second exposure unevenness (position of peaks and valleys) generated in the second scanning exposure to be shifted by 180 degrees from the phase of the second exposure unevenness (position of peaks and valleys) generated in the first scanning exposure. As a result, the second exposure unevenness generated in the first scanning exposure and the second exposure unevenness generated in the second scanning exposure at least partially cancel each other out, so that as shown in Figure 8, the second exposure unevenness can be reduced throughout the multiple scanning exposures in the multiple exposure. Figure 8 shows the second exposure unevenness generated in the first scanning exposure and the second exposure unevenness generated in the second scanning exposure superimposed on each other.

Here, the calculation formula of the time shift amount Sn will be described. The calculation formula of the time shift amount Sn can be generalized in the first and second embodiments, and can be expressed by the following formula (1). In addition, when the emission start timing in the first scanning exposure is used as a reference, the calculation formula of the time shift amount Sn of the emission start timing in the nth scanning exposure (n is any integer from 1 to N) can be expressed by the following formula (2). Each of the following formulas (1) to (2) can be used to calculate the time shift amount Sn for reducing either the first exposure unevenness described in the first embodiment or the second exposure unevenness described in the second embodiment.
Sn={Tp×Te/(1/Pm)}×1/N (1)
Sn={Tp×Te/(1/Pm)}×(n-1)/N...(2)
Tp [μs]: light emission period of pulsed light emitted from the light source unit 1 Pm [pulse/mm]: number of irradiation pulses Te [μm]: period of exposure unevenness to be reduced n [times]: any integer from 1 to N N [times]: number of scanning exposures in multiple exposure Sn [μs]: time shift amount

For example, assume that the number of scanning exposures N in the multiple exposure is two, the irradiation pulse light Pm is 4 [pulse/mm], and the light emission period Tp of the pulse light emitted from the light source unit 1 is 250 [μs]. In this case, as described in the first embodiment, the time shift amount Sn for reducing the first exposure unevenness (period Te: 250 [μm]) is Sn = {Tp x Te/(1/Pm)} x 1/N = {250 x 250/(1/4 x 1000)} x 1/2 = 125 [μs]. Also, as described in the second embodiment, the time shift amount Sn for reducing the second exposure unevenness (period Te: 35 [μm]) is Sn = {Tp x Te/(1/Pm)} x 1/N = {250 x 35/(1/4 x 1000)} x 1/2 = 17.5 [μs].

Example 3
In this embodiment 3, an example in which both the first exposure unevenness and the second exposure unevenness are reduced simultaneously will be described. In this embodiment 3, similarly to the embodiments 1 and 2, the timing determination unit 25 acquires information related to the multiple exposure, and determines the injection start timing for each of the multiple scanning exposures in the multiple exposure based on the information. However, in this embodiment 3, information indicating the period of the first exposure unevenness and information indicating the period of the second exposure unevenness are used as information indicating the period of the exposure unevenness to be reduced. Then, the timing determination unit 25 changes the injection start timing in the multiple scanning exposures according to the period of the first exposure unevenness and the period of the second exposure unevenness so that the first exposure unevenness and the second exposure unevenness are at least partially offset by the multiple scanning exposures.

Specifically, when the number of scanning exposures in the multiple exposure is N, the timing determination unit 25 determines the time shift amount Sn based on a value close to 1/N of the period of the first exposure unevenness (preferably the closest value) among odd multiples of 1/N of the period of the second exposure unevenness. For example, assume that the number of scanning exposures N in the multiple exposure is 2, the period of the first exposure unevenness is 250 [μm], and the period of the second exposure unevenness is 35 [μm]. In this case, the value (119 [μm]) closest to the half value of the period of the first exposure unevenness (250 [μm]) among odd multiples of the half value of the period of the second exposure unevenness (35 [μm]) is set as the period Te of the exposure unevenness to be reduced, and the time shift amount Sn is determined by the above formula (1) or formula (2). As a result, the exposure unevenness (first exposure unevenness, second exposure unevenness) that occurs in each scanning exposure is at least partially offset by the multiple scanning exposures, and as shown in Figure 9, the exposure unevenness can be reduced across the multiple scanning exposures in the multiple exposure.

Here, while the above describes a case where there are two types of periodic components of exposure unevenness, there may be cases where there are M types of periodic components of exposure unevenness (M is an integer of 3 or more). In this case, the timing determination unit 25 selects a value that is closest to an odd multiple of 1/N of each of the second shortest periodic component through the Mth shortest frequency component from among the odd multiples of 1/N of the shortest periodic component among the M types of periodic components. Then, using the selected value as the period Te of the exposure unevenness to be reduced, the time shift amount Sn is determined by the above formula (1) or formula (2). By using the time shift amount Sn determined in this way, it is possible to reduce the exposure unevenness of all periodic components.

As described above, in this embodiment, multiple exposure is performed on the same shot area to reduce the uneven exposure in the shot area. Specifically, the emission start timing is changed in the multiple scanning exposures according to the period of the uneven exposure so that the uneven exposure that occurs periodically on the shot area in each of the multiple scanning exposures is at least partially offset by the multiple scanning exposures. This makes it possible to reduce the uneven exposure in the shot area in the entire multiple exposure (multiple scanning exposures). Note that, as described in Examples 1 to 3, the time shift amount Sn may be determined based on the periodic component of the uneven exposure calculated from the pulse intensity distribution shape, the number of irradiation pulses, and the design information of the optical member (optical integrator, etc.), but is not limited thereto. For example, the time shift amount Sn may be determined based on the result of Fourier analysis of an image obtained by observing the substrate that has been subjected to the first scanning exposure with a scanning electron microscope (SEM).

<Embodiments of a method for manufacturing an article>
The method for manufacturing an article according to an embodiment of the present invention is suitable for manufacturing an article such as a microdevice such as a semiconductor device or an element having a fine structure. The method for manufacturing an article according to the present embodiment includes a step of forming a latent image pattern on a photosensitive agent applied to a substrate using the above-mentioned exposure apparatus (exposure method) (a step of exposing the substrate), and a step of developing (processing) the substrate on which the latent image pattern has been formed in the step. Furthermore, the manufacturing method includes other well-known steps (oxidation, film formation, deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The method for manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article compared to conventional methods.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

1: Light source unit, 12: Original, 14: Illumination optical system, 16: Substrate, 20: Control system, 21: Stage control unit, 22: Light amount calculation unit, 23: Light source control unit, 24: Information input unit, 25: Timing determination unit, 26: Main control unit, 100: Exposure device

Claims (11)

An exposure apparatus that performs scanning exposure multiple times on the same shot area on a substrate,
a projection optical system that projects pulsed light periodically emitted from a light source onto the substrate;
a control unit that controls a signal related to a timing when the light source unit starts emitting the pulsed light;
Equipped with
The control unit controls the timing signal in accordance with a period of the exposure unevenness so that the exposure unevenness that occurs periodically on the shot area in each of the multiple scanning exposures is reduced by the multiple scanning exposures. the exposure unevenness includes a first exposure unevenness that occurs in accordance with a light emission cycle of the pulsed light emitted from the light source unit,
2. The exposure apparatus according to claim 1, wherein the control unit changes the timing in the multiple scanning exposures according to a period of the first exposure unevenness so that the first exposure unevenness is reduced by the multiple scanning exposures. 3. The exposure apparatus according to claim 2, wherein the control unit determines a time shift amount of the timing in the multiple scanning exposures based on an emission period of the pulsed light emitted from the light source unit and a number of scanning exposures for the shot area. the exposure unevenness includes a second exposure unevenness occurring at a period shorter than a period of a first exposure unevenness occurring in accordance with a light emission period of the pulsed light emitted from the light source unit,
4. The exposure apparatus according to claim 1, wherein the control unit changes the timing in the multiple scanning exposures according to a period of the second exposure unevenness so that the second exposure unevenness is reduced by the multiple scanning exposures. The exposure apparatus according to claim 4, wherein the control unit determines a time shift amount of the timing in the multiple scanning exposures based on the emission period of the pulsed light emitted from the light source unit, the period of the second exposure unevenness, the number of pulsed lights irradiated to the substrate while the substrate scans a unit amount, and the number of scanning exposures for the shot area. the exposure unevenness includes a first exposure unevenness occurring in accordance with a light emission period of the pulsed light emitted from the light source unit, and a second exposure unevenness occurring at a period shorter than a period of the first exposure unevenness,
The exposure apparatus according to claim 1, characterized in that, when the number of scanning exposures for the shot area is N, the control unit determines the amount of time shift of the timing in the multiple scanning exposures based on a value closest to 1/N of the period of the first exposure unevenness among odd multiples of 1/N of the period of the second exposure unevenness. The control unit calculates a time shift amount Sn of the timing in the multiple scanning exposures as follows, where Tp is an emission period of the pulsed light emitted from the light source unit, Te is a period of exposure unevenness to be reduced, Pm is the number of the pulsed light irradiated onto the substrate while the substrate is scanned by a unit amount, and N is the number of scanning exposures for the shot area:
Sn={Tp×Te/(1/Pm)}×1/N
7. The exposure apparatus according to claim 1, wherein the exposure is determined by: 8. The exposure apparatus according to claim 1, wherein the control unit changes the timing by controlling the light source unit. 9. The exposure apparatus according to claim 1, wherein the light source unit periodically emits the pulsed light so that the substrate is irradiated with a plurality of superimposed pulsed lights while the substrate is scanned by a unit amount. An exposure method for performing scanning exposure a plurality of times on the same shot area on a substrate using pulsed light periodically emitted from a light source unit, comprising:
an exposure method comprising: controlling a signal related to the timing at which the light source unit starts emitting the pulsed light in accordance with a period of the exposure unevenness , so that the exposure unevenness that occurs periodically on the shot area in each of the multiple scanning exposures is reduced by the multiple scanning exposures. an exposure step of exposing a substrate using the exposure method according to claim 10;
a processing step of processing the substrate exposed in the exposure step,
A method for manufacturing an article, comprising the steps of: manufacturing an article from the substrate processed in the processing step.