WO2023210181A1

WO2023210181A1 - Interference exposure apparatus and device manufacturing method

Info

Publication number: WO2023210181A1
Application number: PCT/JP2023/009215
Authority: WO
Inventors: 洋平那脇
Original assignee: ウシオ電機株式会社
Priority date: 2022-04-28
Filing date: 2023-03-10
Publication date: 2023-11-02
Also published as: JP2023163737A

Abstract

Provided is an interference exposure apparatus capable of monitoring the state of interference fringes in two-beam interference exposure or adjusting the state of interference fringes to a target state.　An interference exposure apparatus 100A patterns a workpiece W by using exposure interference fringes. An optical system 120 includes an exposure splitting element 122 that splits coherent light emitted from a laser light source 110 into a first beam and a second beam, and the first beam and the second beam are crossed to irradiate an irradiation area. A combining element 210 can be placed in the irradiation area in a calibration process to combine a left beam BMl and a right beam BMr. An image sensor 220 measures the intensity distribution of the combined beam BMl+r combined by the combining element 210 in the calibration process.

Description

Interference exposure apparatus and device manufacturing method

The present disclosure relates to an interference exposure apparatus.

Optical devices such as AR (augmented reality) glasses and smart windows are being developed. These optical devices include a diffraction grating, a polarizing plate, and the like having periodic patterning in the submicron region.

Two-beam interference exposure (holographic exposure) is known as a method for realizing patterning with a submicron period. In two-beam interference exposure (also simply referred to as interference exposure), laser light is split into two light beams (two beams). The two light beams are then adjusted to a beam diameter suitable for exposure and collimated, and then made to intersect on the surface of the object (workpiece) to be patterned. Interference fringes for exposure are formed in the area where the two light waves intersect, and a workpiece whose surface is coated with a photosensitive agent is patterned by these interference fringes. The pitch p of the interference fringes is
p=λ/(2n・sinθ)
It is expressed as λ is the wavelength of the laser beam, and θ is 1/2 of the angle at which the two light beams intersect.

There is a limit to the beam diameter that can be irradiated onto the workpiece. Therefore, when the size of a processing area in which a pattern is to be formed on a workpiece is larger than the beam diameter, it is necessary to relatively scan the workpiece and the beam for exposure. This is called the overlapping scan method.

If the size of the processing area is large in the direction in which the interference fringes extend (vertical direction), it is necessary to scan the workpiece along the longitudinal direction. For this purpose, it is necessary to accurately detect the direction in which the interference fringes extend and to make the feed angle of the stage that supports the work perfectly match the direction of the interference fringes. If this direction is misaligned, the contrast of the interference fringes will decrease, making it impossible to transfer them to the photoresist.

Furthermore, if the size of the processing area is large in the direction (lateral direction) perpendicular to the vertical direction in which the interference fringes extend, the stage that supports the workpiece needs to be moved in the horizontal direction (transverse feed). Specifically, it is necessary that an integral multiple of the period of the interference fringes and the width of the lateral movement of the stage match.

Patent Document 1 discloses a configuration in which a beam splitter and two photodiodes are arranged under a workpiece to detect the phase of interference fringes. During exposure, two photodiodes measure the variation in the phase of the interference fringes, and depending on the phase, a phase shifter (Pockels cell) installed on the arm through which one of the light waves propagates is controlled to stabilize the phase. do.

The technique of Patent Document 2 discloses an interference fringe detector provided directly below the workpiece. The interference fringe detector detects the phase, period, and intensity of the interference fringe. The period information output from the interference fringe detector is used to control the right beam angle with an actuator, thereby controlling the period of the interference fringe. Although Patent Document 2 does not disclose a specific configuration of the interference fringe detector, for example, if a two-dimensional image sensor is used, the resolution in that case is limited by the pixel size of the image sensor. The pixel pitch of currently commercially available CMOS sensors is approximately 2.5 μm at the smallest, and the period of interference fringes can only be measured with an accuracy of 5 μm±2.5 μm. Therefore, it cannot be used to measure fine interference fringes used in submicron patterning.

Special Publication No. 5-502109 Japanese Patent Application Publication No. 2002-162750 Patent No. 4065468

With the conventional technology, it is not possible to accurately detect the direction in which the interference fringes extend, that is, the state of the interference fringes. Therefore, it was necessary to perform an exposure calibration process prior to exposing the product. Specifically, in the calibration process, it is necessary to optimize the period and angle of the interference fringes (or the lateral feed width and feed direction) by trial and error, which poses a problem in that it takes a long time.

The present disclosure has been made in such a situation, and one exemplary objective of a certain aspect thereof is to be able to monitor the state of interference fringes in two-beam interference exposure, or to be able to adjust the state of interference fringes to a target state. The purpose of the present invention is to provide an interference exposure device.

A certain aspect of the present disclosure relates to an interference exposure apparatus that patterns a workpiece using interference fringes for exposure. The interference exposure apparatus includes an exposure splitting element that branches coherent light emitted from a laser light source into a first beam and a second beam, and an optical system that crosses the first beam and the second beam and irradiates the irradiation area. In the calibration process, a combining element that can be placed in the irradiation area and combines the first beam and the second beam, and in the calibration process, measuring the intensity distribution of the combined beam combined by the combining element. and an image sensor.

Another aspect of the present disclosure relates to a method for manufacturing a device. The manufacturing method includes the steps of branching coherent light emitted from a laser into a first beam and a second beam, and irradiating the irradiation area with the first and second beams intersecting. a step of multiplexing the first beam and the second beam by the multiplexing element, a step of measuring the intensity distribution of the combined beam multiplexed by the multiplexing element with an image sensor in the calibration process; In the step, the incident angles of the first beam and the second beam with respect to the irradiation area are adjusted based on the intensity distribution measured by the image sensor, and in the exposure process after the calibration process is completed, the workpiece is moved across the irradiation area. moving in a predetermined direction.

Note that arbitrary combinations of the above components, and mutual substitution of components and expressions among methods, devices, systems, etc., are also effective as aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not describe all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. .

According to an aspect of the present disclosure, it is possible to accurately monitor the state of exposure interference fringes in two-beam interference exposure.

1 is a diagram showing an interference exposure apparatus according to Embodiment 1. FIG. It is a figure explaining the interference fringe for exposure formed in the irradiation area. It is a figure which shows the interference fringe for exposure. FIG. 3 is a diagram showing an interference exposure apparatus in a calibration process. It is a figure which shows the measurement beam splitter in a calibration process. It is a figure explaining the multiplexing of the beam by a measurement beam splitter. FIGS. 7A to 7D are diagrams illustrating alignment of the optical system based on interference fringes for monitoring. FIG. 3 is a diagram illustrating measurement of pitch p _x by shifting a measurement beam splitter. FIG. 3 is a diagram showing an interference exposure apparatus according to a second embodiment. FIG. 3 is a diagram showing a diffraction grating in a calibration process. FIG. 3 is a diagram illustrating beam combination using a diffraction grating. It is a figure showing an interference exposure device concerning a modification.

(Summary of embodiment)
1 provides an overview of some example embodiments of the present disclosure. This Summary is intended to provide a simplified description of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments and as a prelude to the more detailed description that is presented later. It does not limit the size. Moreover, this summary is not an exhaustive overview of all possible embodiments, and is not limited to essential components of the embodiments. For convenience, "one embodiment" may be used to refer to one embodiment (example or modification) or multiple embodiments (examples or modifications) disclosed in this specification.

An interference exposure apparatus according to an embodiment patterns a workpiece using interference fringes for exposure. The interference exposure apparatus includes an exposure splitting element that branches coherent light emitted from a laser light source into a first beam and a second beam, and an optical system that crosses the first beam and the second beam and irradiates the irradiation area. In the calibration process, a combining element that can be placed in the irradiation area and combines the first beam and the second beam, and in the calibration process, measuring the intensity distribution of the combined beam combined by the combining element. and an image sensor.

In this configuration, rather than directly measuring interference fringes for exposure, a combining element combines the first and second beams in the same direction, and the interference fringes for monitoring formed by the combined beam are measured. Measure. Since minute changes between the first beam and the second beam are amplified and appear in the monitoring interference fringes, the state of the exposure interference fringes can be indirectly and accurately monitored.

In one embodiment, the interference exposure apparatus may further include a stage capable of moving the workpiece so as to pass through the irradiation area during the exposure process. The multiplexing element may be provided on the stage at a position adjacent to the area where the work is placed. The monitoring interference fringes are formed with the orientation of the multiplexing element as a reference. Therefore, by fixing the multiplexing element on the stage, accurate monitoring becomes possible.

In one embodiment, the multiplexing element may be a measurement beam splitter that can be placed in the irradiation area with its split plane perpendicular to the surface of the workpiece in the calibration process. By using a measurement beam splitter (beam combiner), it is possible to greatly expand the pitch of the monitoring interference fringes in one direction.

In one embodiment, the multiplexing element may be a diffraction grating that can be placed in the irradiation area in the calibration process with its diffraction surface parallel to the surface of the workpiece.

In one embodiment, the diffraction grating may have a period twice the pitch of the interference fringes for exposure.

One embodiment may further include an arithmetic processing device that adjusts the angle of incidence of the first beam onto the irradiation area and the angle of incidence of the second beam onto the irradiation area based on the intensity distribution measured by the image sensor. .

In one embodiment, the processing unit adjusts the angle of incidence of the first beam onto the irradiation area and the angle of incidence of the second beam onto the irradiation area so that the intensity distribution measured by the image sensor becomes uniform. Good too.

In one embodiment, the interference exposure apparatus includes a processing unit that adjusts the angle of incidence of the first beam onto the irradiation area and the angle of incidence of the second beam onto the irradiation area based on the intensity distribution measured by the image sensor. Further provision may be made. When taking a coordinate system in which the surface of the workpiece is the xy plane and the split plane of the measurement beam splitter is the yz plane, the arithmetic processing unit calculates that the pitch in the y direction of the monitoring interference fringes measured by the image sensor becomes large. As such, the deviation angle Δφ _l of the first beam around the z-axis and the deviation angle Δφ _r of the second beam around the z-axis may be changed.

In one embodiment, the arithmetic processing device may change the incident angle θ _l of the first beam and the incident angle θ _r of the second beam so that the pitch of the monitoring interference fringes in the x direction increases.

In one embodiment, the processing unit calculates the pitch of the exposure interference fringes based on the change in intensity of the combined beam measured by the image sensor when the measurement beam splitter is moved in the x direction. It's okay.

In one embodiment, the optical system may further include a first mirror that can control the irradiation direction of the first beam, and a second mirror that can control the irradiation direction of the second beam.

In one embodiment, the interference exposure apparatus further includes a processing unit that calculates at least one of an incident angle deviation of the first beam and an incident angle deviation of the second beam based on the intensity distribution measured by the image sensor. You may prepare.

(Embodiment)
Hereinafter, the present disclosure will be described based on preferred embodiments with reference to the drawings. Identical or equivalent components, members, and processes shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. Further, the embodiments are illustrative rather than limiting the disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.

The dimensions (thickness, length, width, etc.) of each member described in the drawings may be scaled up or down as appropriate for ease of understanding. Furthermore, the dimensions of multiple members do not necessarily represent their size relationship, and even if a member A is drawn thicker than another member B on a drawing, member A may be drawn thicker than member B. It may be thinner than that.

(Embodiment 1)
FIG. 1 is a diagram showing an interference exposure apparatus 100A according to the first embodiment. The interference exposure apparatus 100A patterns the workpiece W using interference fringes for exposure. The workpiece W is a substrate whose surface is coated with a photosensitive agent. The material of the workpiece W is not particularly limited, but examples thereof include a glass substrate, a resin substrate, a semiconductor substrate, and the like.

The interference exposure apparatus 100A includes a laser light source 110, an optical system 120, and an interference fringe monitoring device 200A.

The laser light source 110 emits a coherent light beam BM ₀ having a wavelength λ. A beam can be read as a light wave or a light flux. The optical system 120 includes an exposure splitting element 122 that branches the beam BM ₀ emitted from the laser light source 110 into a first beam BM ₁ and a second beam BM ₂ . Although a beam splitter or a diffraction grating can be used as the exposure splitting element 122, in this embodiment, the beam splitter BS1 is used. In order to distinguish it from a measurement beam splitter which will be described later, the beam splitter BS1 of the exposure demultiplexing element 122 is also referred to as an exposure beam splitter. The optical system 120 makes the branched first beam BM ₁ and second beam BM ₂ intersect and irradiates the irradiation area 132 on the stage 130 . The first beam BM ₁ heading from the optical system 120 toward the irradiation area 132 is called a left beam BM _l , and the second beam BM ₂ heading from the optical system 120 toward the irradiation area 132 is called a right beam BM _r .

For example, the optical system 120 includes mirrors M1, M2, M3, and magnifying

optical systems

124, 126 in addition to the exposure beam splitter BS1. Mirror M3 turns beam _BM0 from laser light source 110 and guides it to exposure beam splitter BS1 at an appropriate angle. Beam BM ₀ is split into two beams BM ₁ and BM ₂ by exposure beam splitter BS1. The exposure beam splitter BS1 may be an intensity beam splitter or a polarizing beam splitter.

The first mirror M1 returns the first beam _BM1 . The second mirror M2 returns the second beam _BM2 . The first mirror M1 and the second mirror M2 can be rotated and translated by a control means such as an actuator.

The magnifying optical system 124 magnifies the beam _BM1 reflected by the first mirror M1. The expanded beam is guided to the irradiation area 132 as a left beam _BM1 . Similarly, the magnifying optical system 126 magnifies the beam BM ₂ reflected by the second mirror M2. The expanded beam is guided to the irradiation area 132 as a right beam _BMr .

In the irradiation area 132, exposure interference fringes are formed by the left beam _BMl and the right beam _BMr . During the exposure process, the workpiece W is supported on the stage 130. The stage 130 moves the workpiece W in the vertical direction in which exposure interference fringes extend within the irradiation area 132 (scan exposure). This makes it possible to form a long pattern. Furthermore, between scan exposures, the stage 130 transports the workpiece W in the lateral direction of the interference fringes for exposure so that the fringes overlap each other in the previous scan exposure and the next scan exposure (overlapping). combination). This makes it possible to form a wide pattern. The combination of vertical scan exposure and horizontal overlapping is called overlapping scan exposure.

A coordinate system will be introduced to facilitate understanding. The surface of the workpiece W on which exposure interference fringes are to be formed is referred to as a reference surface _S0 . The introduced coordinate system has a z-axis in a direction perpendicular to the reference plane _S0 . In other words, the plane parallel to the reference plane _S0 becomes the xy plane. Further, in an ideal state, it is assumed that the left beam BM _l and the right beam BM _r are guided parallel to the xz plane. In other words, the horizontal direction of the page is the x-axis, the height direction of the page is the z-axis, and the depth direction of the page is the y-axis. In the following explanation, it is assumed that the origin of this coordinate system moves as appropriate.

FIG. 2 is a diagram illustrating exposure interference fringes formed in the irradiation area 132. Here, the reference plane S ₀ on which exposure interference fringes are formed is the xy plane of z=0.

D _l and D _r indicate the ideal waveguiding directions of the left beam BM _l and the right beam BM _r , respectively. D _l and D _r are straight lines in the xz plane, and θ represents the ideal angle of incidence of the left beam BM _l and the right beam BM _R.

Δθ _l represents the deviation of the actual angle of incidence of the left beam BM _l from the ideal angle of incidence θ _l . Δθ _r represents the deviation of the actual angle of incidence of the right beam BM _r from the ideal angle of incidence θ _r . That is, the actual angle of incidence θ _l of the left beam BM _l is θ+Δθ _l , and the actual angle of incidence θ _r of the right beam BM _r is θ+Δθ _r .

As mentioned above, the left beam BM _l and the right beam BM _r are guided parallel to the xz plane in the ideal state. In other words, the ideal incident directions D _l and D _r do not include the z component. Δφ _l is the deviation angle of the left beam BM ₁ around the z-axis, and Δφ _r is the deviation angle of the right beam BM _r around the z-axis. In the ideal state, Δφ _l =Δφ _r =0.

The wave number vector k _l of the light wave of the left beam BM _l and the wave number vector k _r of the light wave of the right beam BM _r are expressed by equations (1) and (2).

Here, k _lz represents the z component of k _l and k _rz represents the z component of k _r . Further, Δφ _l ≒0 and Δφ _r ≒0.

The electric fields E _l and E _r at the coordinate r of the left and right beams BM _l and BM _r are respectively expressed by equations (3) and (4).

The intensities of the two beams BM _l and BM _r at the coordinate r are expressed by equation (5).

It is assumed that the reference plane _S0 on which exposure interference fringes are formed is an xy plane with z=0. At this time, the intensity distribution I _EXP (x, y) of the interference fringes for exposure formed on the reference plane S ₀ is expressed by equation (6) by substituting z=0 into equation (5).

FIG. 3 is a diagram showing interference fringes for exposure. The pitch of the interference fringes for exposure in the x direction is expressed by equation (7). Further, the angular deviation α of the exposure interference fringes from the y-axis is expressed by equation (8).

In order to perform overlapping scan exposure, it is necessary to accurately detect p _x ' and α', or to adjust the combination of p _x ' and α', that is, the state of the interference fringes for exposure, to a predetermined target state. , it is necessary to align the optical system 120.

In an ideal state, Δθ _l =Δθ _r =0, Δφ _l =Δφ _r =0. At this time, the ideal pitch p _x and angular shift α of the interference fringes for exposure are as follows:
p _x =λ/(2sinθ)
α=0
It is.

The process of accurately detecting the pitch p _x and the angular deviation α or setting them as target states prior to the exposure process is referred to as a calibration process.

Return to Figure 1. In the calibration process, an interference fringe monitoring device 200A is provided to measure the state of exposure interference fringes. The interference fringe monitoring device 200A does not directly measure the intensity distribution of the exposure interference fringe, but measures the intensity distribution of an interference fringe different from the exposure interference fringe (hereinafter referred to as monitor interference fringe).

The interference fringe monitoring device 200A includes a multiplexing element 210, an image sensor 220, and an arithmetic processing unit 230.

The combining element 210 can be placed in the irradiation area 132 during the calibration process, and combines the left beam BM _l and the right beam BM _r so as to guide them in the same direction.

FIG. 4 is a diagram showing the interference exposure apparatus 100A in the calibration process. In this embodiment, the multiplexing element 210 is a measurement beam splitter (beam combiner) 212. The measurement beam splitter 212 may be an intensity beam splitter or a polarization beam splitter. The measurement beam splitter 212 may be of a flat plate type or a prism type.

The measurement beam splitter 212 is provided on the stage 130 at a position adjacent to the area on which the workpiece W is placed. In the calibration process, the measurement beam splitter 212 is positioned in the irradiation area 132 by the stage 130. At this time, the split surface 214 of the measurement beam splitter 212 is arranged perpendicular to the reference plane _S0 corresponding to the surface of the workpiece W.

FIG. 5 is a diagram showing the measurement beam splitter 212 in the calibration process. The split surface 214 of the measurement beam splitter 212 is arranged parallel to the yz plane. Here, the coordinate system is determined so that the split plane 214 coincides with the yz plane where x=0.

The left beam BM _l is transmitted through the measurement beam splitter 212 , and the right beam BM _r is reflected at the split surface 214 of the measurement beam splitter 212 . The beam (combined beam) BM _l+r multiplexed by the measurement beam splitter 212 is guided to the image sensor 220 . The image sensor 220 measures the intensity distribution of the combined beam BM _l+r . This intensity distribution is the monitoring interference fringe. As the image sensor 220, a CMOS (Complementary Metal Oxide Semiconductor) sensor or a CCD (Charge Coupled Device) camera can be used.

In the calibration process, the intensity distribution observed by the image sensor 220 will be explained.

FIG. 6 is a diagram illustrating beam combination by the measurement beam splitter 212. Here, too, the coordinate system is determined so that the split plane 214 coincides with the yz plane where x=0.

k _l '' represents the wave number vector of the left beam BM _l transmitted through the measurement beam splitter 212, and k _r '' represents the wave number vector of the right beam BM _r reflected by the measurement beam splitter 212. The wave number vectors k _l '' and k _r '' are expressed by equations (9) and (10).

When the measurement plane is placed behind the beam splitter, the intensity distribution I(x,y) of the combined beam BM _l+r to be measured is expressed by equation (11).

As can be seen from equation (11), the measured intensity distribution I(x, y) depends on the deviations Δθ _l , Δθ _r , Δφ _l , Δφ _r of the beams BM _l , BM _r from the ideal waveguiding direction. Change. This intensity distribution I(x,y) is an interference fringe with spatial regularity.

From equation (11), the spatial frequency ν _y in the y direction on the measurement surface is expressed by equation (12).

Note that the relationship ν=2π/p holds between the spatial frequency ν and the pitch p.

Further, the angular shift α' is expressed by equation (13) using the spatial frequency ν _y in the y direction.

Furthermore, the spatial frequency ν _x and pitch p _x in the x direction on the measurement surface are expressed by equations (14) and (15), respectively.

It should be noted that the pitch p _x of the interference fringes for monitoring formed by the combined beam BM _l+r measured by the image sensor 220 is much larger than the pitch p _x of the interference fringes for exposure formed on the reference plane _S0 . This is the point where it gets bigger. This is clear from a comparison of equation (15) and equation (7); in equation (15), the denominator is close to zero, so the pitch _px becomes very large. It should be noted that this pitch p _x is large enough to be measurable by a typical CMOS or CCD sensor.

In this way, the interference fringe monitoring device 200A does not directly monitor the exposure interference fringe, but generates a monitoring interference fringe containing information equivalent to the exposure interference fringe and measures its intensity distribution, thereby controlling the beams BM _l , BM The state of _r can be detected.

In this way, the intensity distribution I(x, y) of the interference fringes for monitoring measured by the image sensor 220 contains information regarding the deviations Δθ _l , Δθ _r , Δφ _l , Δφ _r from the ideal state of the beams BM _l , BM _r . Contains. Therefore, various processes can be performed based on the intensity distribution I(x,y) of the monitoring interference fringes.

Note that in the present disclosure, there are no particular limitations on how the measured intensity I(x, y) is used to perform the calibration, but some examples regarding the calibration will be described.

(Proofreading processing example 1)
In one embodiment, the processing unit 230 may calculate the current state of the beams BM _l and BM _r based on the measured intensity distribution I(x,y). This state includes at least one of Δθ _l , Δθ _r , Δφ _l , and Δφ _r .

For example, if the spatial frequency ν _y of the monitor interference fringe in the y direction is calculated from the image data, Δφ _l +Δφ _r can be calculated from equation (12).

Further, by calculating the angular shift α' of the monitor interference fringe and the spatial frequency ν _x in the x direction from the image data, the values of (θ+Δθ l ) and (θ+Δθ _r ₎ can be calculated.

Further, the arithmetic processing unit 230 can calculate the pitch p _x ' of the exposure interference fringes from equation (7) using (θ+Δθ l ) and (θ+Δθ _r ₎ . This makes it possible to accurately determine the width of the lateral feed in the exposure process.

Further, the arithmetic processing unit 230 can calculate the angular deviation α' from the y-axis from equation (8) using (θ+Δθ _l ), (θ+Δθ _r ), and (Δφ _l +Δφ _r ). This makes it possible to accurately determine the scan direction in the exposure process.

(Proofreading processing example 2)
Based on the measured intensity distribution I(x, y), the arithmetic processing unit 230 adjusts the beams BM _l and BM _r to ideal states, that is, Δθ _l , Δθ _r , Δφ _l , and Δφ _r approach zero. The alignment of the optical system 120 may be performed as follows. For example, the processing unit 230 can change Δθ _l and Δφ l by controlling the first mirror M1 of the optical system 120, and can change Δθ r and _Δφ _l by controlling the second mirror M2 of the optical system 120. Δφ _r can be varied.

FIGS. 7(a) to (d) are diagrams illustrating alignment of the optical system 120 based on monitoring interference fringes. FIG. 7(a) shows interference fringes for monitoring in a state where rough alignment has been completed.

As shown in FIG. 7(b), the first mirror M1 and the second mirror M2 are controlled to optimize Δφ _l and Δφ _r so that the spatial frequency ν _y of the monitor interference fringe in the y direction becomes zero. become Thereby, the optical system 120 can be adjusted to a state where Δφ _l +Δφ _r =0. Note that when Δφ is 0.001°, the period of the stripes is approximately 20 mm. Therefore, by using the large image sensor 220, it is possible to measure up to 0.001°.

As shown in FIGS. 7(c) and (d), the incident angle deviation Δθ _l of the left beam BM _l and the deviation of the right beam BM _r so that the spatial frequency ν _x of the monitoring interference fringe in the x direction becomes zero. The angle of incidence deviation Δθ _r is adjusted. When all deviations approach zero, the interference fringes disappear and the intensity distribution becomes uniform.

In other words, the arithmetic processing unit 230 may control the states of the first mirror M1 and the second mirror M2 so that the intensity distribution of the image obtained by the image sensor 220 is uniform. When this alignment is completed, Δφ _l +Δφ _r ≒0 and Δθ _l ≒Δθ _r ≒0. At the time of this alignment, the arithmetic processing unit 230 does not necessarily need to calculate the deviation amounts Δφ _l , Δφ _r , Δθ _l , and Δθ _r .

Furthermore, when alignment is completed, the deviation angle α of the exposure interference fringes from the y-axis becomes zero. That is, in the exposure process, the workpiece W may be scanned in the y-axis direction.

The pitch p _x of the interference fringes for exposure may be calculated from equation (7) as described in the first example of the calibration process, and the amount of lateral movement may be determined. Alternatively, the pitch p _x can be measured by beam splitter shift processing, which will be described below.

FIG. 8 is a diagram illustrating measurement of the pitch p _x by shifting the measurement beam splitter 212. In the calibration process, stage 130 shifts split plane 214 from x=0 to x=d'. This shift causes a path difference between the left beam BM _l and the right beam BM _r , and the distance becomes ΔL=2d'sinθ _r . However, θ _r =θ+Δθ _r . The phase difference ψ(d') at this time is expressed by equation (16).

The intensity of the monitoring interference fringe is expressed by equation (17), and by substituting z=d', equation (18) is obtained.

The light intensity when the incident angles of the left and right beams are adjusted to the ideal state (θ _l =θ _r , Δφ _l =Δφ _r =0) is expressed by equation (19).

Therefore, when d' becomes an integer multiple of _px , the intensities I(d') are reinforced by interference. Therefore, after completing the alignment of the optical system 120, the stage 130 scans the measurement beam splitter 212 in the x-axis direction and measures the distance between the peaks of the intensity I(d'), thereby determining the pitch _p It can be measured.

(Embodiment 2)
FIG. 9 is a diagram showing an interference exposure apparatus 100B according to the second embodiment. The basic configuration of the interference exposure apparatus 100B is the same as that in FIG. 1, and the configuration of the interference fringe monitoring device 200B is different.

The interference fringe monitoring device 200B includes a diffraction grating 216 as a multiplexing element 210. Diffraction grating 216 is provided on stage 130 at a position adjacent to the area where workpiece W is placed. In the calibration process, the stage 130 positions the diffraction grating 216 in the illumination area 132 . At this time, the grooves of the diffraction grating 216 are arranged to coincide with the y direction.

FIG. 10 is a diagram showing the diffraction grating 216 during the calibration process. In this example, the diffraction grating 216 is of a reflective type, and reflects and combines the left beam BM _l having an incident angle θ _l and the right beam BM _r having an incident angle θ _r in the same direction. The image sensor 220 measures the intensity distribution of the combined beam BM _l+r combined by the diffraction grating 216 in the calibration process.

Note that the diffraction grating 216 may be of a transmission type, in which case the image sensor 220 is provided below the diffraction grating 216.

FIG. 11 is a diagram illustrating beam combination by the diffraction grating 216. A coordinate system is determined so that the surface 218 of the diffraction grating 216 coincides with the xy plane of z=0, and the grating direction of the diffraction grating 216 is in the y-axis direction. The diffraction grating 216 has a grating interval (period) d that is twice the exposure pitch. The grating vector K is expressed by equation (20).
K=2π/d(1,0,0)...(20)
becomes.

k _l ' represents the wave number vector of the left beam BM _l diffracted by the diffraction grating 216, and k _r ' represents the wave number vector of the right beam BM _r diffracted by the diffraction grating 216. The wave number vectors k _l ′ and k _r ′ are expressed by equations (21) and (22). m is the diffraction order.

Assuming that −1st-order light is used for the left beam BM _l and +1st-order light is used for the right beam BM _r , the wave number vectors k _l ′ and k _r ′ are expressed by equations (23) and (24).

When the measurement surface of the image sensor 220 is placed above the diffraction grating 216, the intensity distribution I(x,y) of the combined beam BM _l+r to be measured is expressed by equation (25).

As can be seen from equation (25), the measured intensity distribution I(x, y) varies depending on the deviations Δθ _l , Δθ _r , Δφ _l , Δφ _r of the beams BM _l , BM _r from the ideal waveguide direction. Change.

The spatial frequency ν _y of the measurement surface in the y direction is expressed by equation (26).

Further, the angular shift α' is expressed by equation (27) using the spatial frequency ν _y in the Y direction. When ν _y =0, α'=0.

The spatial frequency ν _x in the x direction of the measurement surface is expressed by equation (28).

When ν _x =0, by rearranging equation (28) using d=2p _x =λ/sin θ, equation (29) is obtained.

Equation (29) explicitly holds true when Δθ _l =Δθ _r =0. As other solutions, solutions for non-zero Δθ _l and Δθ _r may exist only when the incident angle θ is close to 90 degrees, so the apparatus may be configured to exclude this solution.

Thus, if the optical system 120 is aligned so that the spatial frequency ν _x in the x direction is zero, that is, the intensity measured by the image sensor 220 is uniform, Δθ _l =Δθ _r =0. is guaranteed, and then θ=sin ⁻¹ (λ/d).

The pitch of the interference fringes for monitoring can be calculated from equation (30).

When aligned so that ν _x =0, the pitch is p _x' = d/2.

(Modified example)
FIG. 12 is a diagram showing an interference exposure apparatus 100Aa according to a modification. This modification is a modification of the interference exposure apparatus 100A shown in FIG. 1, and an exposure diffraction grating G1 is used as the exposure demultiplexing element 122 instead of the beam splitter. The rest is the same as in the first embodiment. Similarly, in the interference exposure apparatus 100B of FIG. 9, it is also possible to use the exposure diffraction grating G1 as the exposure demultiplexing element 122.

Although the embodiments of the present disclosure have been described using specific terms, this description is merely an example to aid understanding, and does not limit the scope of the present disclosure or claims. The scope of the present invention is defined by the claims, and therefore embodiments, examples, and modifications not described here are also included within the scope of the present invention.

W Work 100 Interference exposure device 110 Laser light source 120 Optical system 122 Exposure splitting element BS1 Exposure beam splitter G1 Exposure diffraction grating 124 Enlargement optical system 126 Enlargement optical system 130 Stage 200 Interference fringe monitor device 210 Multiplexing element 212 Beam splitter 214 Split surface 216 Diffraction grating 220 Image sensor 230 Arithmetic processing unit

Claims

An interference exposure device that patterns a workpiece using interference fringes for exposure,
an optical system that includes a splitting element that branches coherent light emitted from a laser light source into a first beam and a second beam, and that crosses the first beam and the second beam and irradiates the irradiation area;
In the calibration process, a combining element that can be placed in the irradiation area and combines the first beam and the second beam;
In the calibration process, an image sensor that measures the intensity distribution of the combined beam combined by the multiplexing element;
An interference exposure apparatus comprising:
In the exposure process, further comprising a stage capable of moving the workpiece so as to pass through the irradiation area,
2. The interference exposure apparatus according to claim 1, wherein the multiplexing element is provided on the stage at a position adjacent to an area where the workpiece is placed.
3. The multiplexing element is a measurement beam splitter that can be placed in the irradiation area in the calibration process with its split surface perpendicular to the surface of the workpiece. interference exposure equipment.
The interference exposure according to claim 1 or 2, wherein the multiplexing element is a diffraction grating that can be placed in the irradiation area in the calibration process with its diffraction surface parallel to the surface of the workpiece. Device.
The interference exposure apparatus according to claim 4, wherein the diffraction grating has a period twice the pitch of the exposure interference fringes.
The method further includes a calculation processing device that adjusts the angle of incidence of the first beam onto the irradiation area and the angle of incidence of the second beam onto the irradiation area based on the intensity distribution measured by the image sensor. The interference exposure apparatus according to claim 1 or 2.
The arithmetic processing unit adjusts the angle of incidence of the first beam onto the irradiation area and the angle of incidence of the second beam onto the irradiation area so that the intensity distribution measured by the image sensor becomes uniform. The interference exposure apparatus according to claim 6, characterized in that:
further comprising an arithmetic processing device that adjusts an incident angle of the first beam to the irradiation area and an incident angle of the second beam to the irradiation area based on the intensity distribution measured by the image sensor,
When taking a coordinate system in which the surface of the workpiece is an xy plane and the split surface of the measurement beam splitter is a yz plane, the arithmetic processing unit is configured to calculate the y direction of the monitor interference fringe measured by the image sensor. The interference according to claim 3, characterized in that the deviation angle Δφ l of the first beam around the z-axis and the deviation angle Δφ r of the second beam around the z-axis are changed so that the pitch of the interference beam increases. Exposure equipment.
The arithmetic processing device changes the incident angle θ l of the first beam and the incident angle θ r of the second beam so that the pitch of the monitoring interference fringes in the x direction increases. Item 8. Interference exposure apparatus according to item 8.
The arithmetic processing unit calculates the pitch of the exposure interference fringes based on a change in the intensity of the combined beam measured by the image sensor when the measurement beam splitter is moved in the x direction. The interference exposure apparatus according to claim 8, characterized in that:
The method further comprises an arithmetic processing device that calculates at least one of an incident angle deviation of the first beam and an incident angle deviation of the second beam based on the intensity distribution measured by the image sensor. 3. The interference exposure apparatus according to item 1 or 2.
The optical system is
a first mirror capable of controlling the irradiation direction of the first beam;
a second mirror capable of controlling the irradiation direction of the second beam;
The interference exposure apparatus according to claim 1 or 2, further comprising the following.
A method for manufacturing a device, the method comprising:
branching the coherent light emitted from the laser into a first beam and a second beam, intersecting the first beam and the second beam and irradiating the irradiation area;
In the calibration process, combining the first beam and the second beam by a combining element arranged in the irradiation area;
In the calibration process, measuring the intensity distribution of the combined beam combined by the combining element using an image sensor;
In the calibration process, adjusting the angle of incidence of the first beam and the second beam with respect to the irradiation area based on the intensity distribution measured by the image sensor;
In an exposure process after completion of the calibration process, moving the workpiece in a predetermined direction so as to pass through the irradiation area;
A manufacturing method characterized by comprising: