JP7830274B2 - Light irradiation apparatus and exposure apparatus - Google Patents

Description

This invention relates to a technique for exposing a substrate, such as a semiconductor substrate, semiconductor package substrate, printed circuit board, or glass substrate, in order to draw a pattern on it.

One technique for forming patterns such as wiring patterns on various substrates, including semiconductor substrates, printed circuit boards, semiconductor package substrates, and glass substrates, involves irradiating a photosensitive layer formed on the substrate surface with a light beam modulated according to exposure data, thereby exposing the photosensitive layer. For example, Patent Document 1 discloses a drawing apparatus and a light irradiation apparatus used as its light source, which performs drawing on a substrate by modulating a laser light beam (line beam) having a flattened beam spot using a light modulator and irradiating it onto the substrate. In this technique, to generate a high-intensity line beam with a uniform intensity distribution, laser light emitted from multiple laser light sources (laser diodes) is combined to produce a single line beam.

Specifically, multiple laser light sources are arranged so that the direction of the emitted light falls within the same plane. On the optical path of the light emitted towards a single point on that plane, a splitting lens, an optical path length difference generator, a focusing lens, and the like are arranged in sequence. Through the action of these optical systems, a line beam is generated, with the direction parallel to the plane being the longitudinal direction, and the direction perpendicular to it being narrowed. The optical path length difference generator is provided to suppress interference that occurs when the coherent laser light is combined.

Patent No. 6383166

For example, to further increase light intensity, one might consider increasing the number of laser light sources. In such a case, there will be a larger component of light incident at a large angle to the splitting lens. Consequently, the light exiting the splitting lens and entering the optical path length difference generation section will also have various angular components. Light incident at such large angles to the splitting lens and optical path length generation section may be emitted from the sides of these optical elements. This dissipation of light can lead to problems such as insufficient intensity in the final line beam and loss of uniformity.

To avoid this problem, it is necessary to minimize the angle of light divergence incident on the splitting lens. For example, increasing the distance between the light source and the splitting lens is one possible approach. However, doing so would increase the overall length of the optical path, leading to a larger device.

This invention has been made in view of the above-mentioned problems, and aims to provide a technology that can suppress the dissipation of light emitted from multiple laser light sources without increasing the optical path length in a light irradiation device and an exposure device using the same, which combine laser light beams generated using multiple light sources into a single beam and emit it.

The light irradiation device according to this invention comprises a plurality of laser light sources arranged such that the centerlines of the emitted light are contained in the same plane and intersect at a point within the plane, and an illumination optical system that combines the laser light emitted from the plurality of laser light sources to generate a single laser light beam and irradiates the surface to be irradiated. The illumination optical system includes an incident angle conversion unit including a first lens positioned at the incident point of light emitted from each of the plurality of laser light sources, and a second lens positioned in a beam expander relationship with the first lens; a splitting lens unit having a plurality of lenses arranged perpendicular to the optical axis of the incident angle conversion unit and along the plane, which splits the light emitted from the incident angle conversion unit using the plurality of lenses; an optical path length difference generation unit having a plurality of light-transmitting units arranged perpendicular to the optical axis and having different optical path lengths, which causes the light that has passed through the plurality of lenses to be incident on each of the plurality of light-transmitting units; and a focusing lens unit that overlaps the irradiation areas of the light emitted from the plurality of light-transmitting units on the surface to be irradiated.

In this configuration, an incident angle conversion unit is provided between multiple laser light sources, which emit light from various directions within a single plane toward a single point in that plane, and the splitting lens section. In the incident angle conversion unit, the first lens and the second lens are positioned in a beam expander configuration. Generally, beam expanders are used to enlarge or reduce the beam diameter of collimated light by injecting collimated light along their optical axis. However, in the incident angle conversion unit of this invention, since laser light is incident from various directions, light also enters from directions that are inclined with respect to the optical axis.

As will be explained in more detail later, this configuration allows the angle of light divergence entering the splitting lens to be reduced compared to a configuration without an incident angle conversion unit. In other words, the incident angle conversion unit reduces the incident angle when light emitted from each laser light source enters the splitting lens. Thus, the incident angle conversion unit can achieve an effect equivalent to increasing the distance between the laser light source and the splitting lens, without actually increasing the distance.

Therefore, by reducing the incident angle of light entering the splitting lens, it is possible to achieve the effect of suppressing light dissipation from the splitting lens and the optical path length difference generation unit without increasing the optical path length.

Furthermore, since the incident angle conversion unit also functions as a beam expander, it can generate a light beam with a spot size corresponding to the size of the splitting lens from the light beams emitted from each laser light source, and direct this beam into the splitting lens. Therefore, it is possible to uniformly incident light onto the multiple lenses constituting the splitting lens.

As described above, according to the present invention, by providing an incident angle conversion unit combining two lenses in the optical path from multiple laser light sources to the splitting lens, it is possible to prevent light dissipation caused by light incident at a large incident angle on the splitting lens without increasing the optical path length.

This is a schematic front view showing the general configuration of the exposure apparatus according to the present invention. This is a block diagram showing an example of the electrical configuration of the exposure apparatus shown in Figure 1. This is a diagram showing the schematic configuration of the light irradiation section. This diagram schematically shows an example of the detailed configuration of an exposure head. This is a diagram showing the schematic configuration of the laser emission unit. This is a ray diagram showing the overall configuration of the illumination optical system and the optical path of the light beam. This diagram shows a more detailed configuration and operation of the incident angle conversion unit. This is a ray diagram showing the light passing through the split lens and the optical path length difference generation section. This diagram shows the relationship between the incident light entering the angle conversion unit and the incident light entering the splitting lens.

Figure 1 is a schematic front view showing the general configuration of the exposure apparatus according to the present invention, and Figure 2 is a block diagram showing an example of the electrical configuration of the exposure apparatus in Figure 1. In Figure 1 and the following figures, the horizontal direction X, the horizontal direction Y perpendicular to the X direction, the vertical direction Z, and the rotation direction θ around a rotation axis parallel to the Z direction are indicated as appropriate.

The exposure apparatus 1 draws a pattern on a photosensitive material, such as a resist, by irradiating the substrate S (substrate to be exposed), on which a layer of photosensitive material such as a resist is formed, with laser light of a predetermined pattern. Various substrates can be used as the substrate S, such as semiconductor package substrates, printed circuit boards, glass substrates for various display devices, and semiconductor substrates.

The exposure apparatus 1 comprises a main body 11, which consists of a main body frame 111 and a cover panel (not shown) attached to the main body frame 111. Various components of the exposure apparatus 1 are arranged both inside and outside the main body 11.

The interior of the main body 11 of the exposure apparatus 1 is divided into a processing area 112 and a transfer area 113. The processing area 112 mainly houses the stage 2, stage drive mechanism 3, exposure unit 4, and alignment unit 5. An illumination unit 6, which supplies illumination light to the alignment unit 5, is located outside the main body 11. The transfer area 113 houses a transfer device 7, such as a transfer robot, for loading and unloading substrates S from the processing area 112. Furthermore, a control unit 9 is located inside the main body 11. The control unit 9 is electrically connected to each part of the exposure apparatus 1 and controls the operation of these parts.

The transport device 7, located in the transfer area 113 inside the main unit 11, receives unprocessed substrates S from an external transport device or substrate storage device (not shown) and loads them into the processing area 112. It also unloads processed substrates S from the processing area 112 and discharges them externally. The loading of unprocessed substrates S and the unloading of processed substrates S are performed by the transport device 7 in accordance with instructions from the control unit 9.

Stage 2 has a flat, plate-like shape and holds the substrate S placed on its upper surface in a horizontal position. Multiple suction holes (not shown) are formed on the upper surface of Stage 2. By applying negative pressure (suction pressure) to these suction holes, the substrate S placed on Stage 2 is fixed to the upper surface of Stage 2. Stage 2 is driven by a stage drive mechanism 3.

The stage drive mechanism 3 is an X-Y-Z-θ drive mechanism that moves the stage 2 in the Y direction (main scanning direction), X direction (sub-scanning direction), Z direction, and rotational direction θ (yaw direction). The stage drive mechanism 3 includes a Y-axis robot 31, which is a single-axis robot extending in the Y direction; a table 32 driven in the Y direction by the Y-axis robot 31; an X-axis robot 33, which is a single-axis robot extending in the X direction on the upper surface of the table 32; a table 34 driven in the X direction by the X-axis robot 33; and a θ-axis robot 35 that drives the stage 2, supported on the upper surface of the table 34, in the rotational direction θ relative to the table 34.

Therefore, the stage drive mechanism 3 can drive the stage 2 in the Y direction using the Y-axis servo motor of the Y-axis robot 31, drive the stage 2 in the X direction using the X-axis servo motor of the X-axis robot 33, and drive the stage 2 in the rotational direction θ using the θ-axis servo motor of the θ-axis robot 35. These servo motors are not shown in the figures. Furthermore, the stage drive mechanism 3 can drive the stage 2 in the Z direction using the Z-axis robot 37, which is not shown in Figure 1. This stage drive mechanism 3 moves the substrate S placed on the stage 2 by operating the Y-axis robot 31, X-axis robot 33, θ-axis robot 35, and Z-axis robot 37 in response to commands from the control unit 9.

The exposure unit 4 includes an exposure head 41 positioned above the substrate S on the stage 2, and a light irradiation unit 40 that includes a light source drive unit 42, a laser emission unit 43, and an illumination optical system 44, which irradiates the exposure head 41 with laser light. Multiple exposure units 4 may be provided at different positions in the X direction.

The laser light emitted from the laser emission unit 43 by the operation of the light source drive unit 42 is irradiated onto the exposure head 41 via the illumination optical system 44. The exposure head 41 modulates the laser light emitted from the light irradiation unit using a spatial light modulator (hereinafter sometimes simply referred to as "light modulator") 410, and projects it onto the substrate S moving directly beneath it. By exposing the substrate S with the laser light beam in this way, a pattern is drawn on the substrate S (exposure operation).

The alignment unit 5 has an alignment camera 51 positioned above the substrate S on the stage 2. This alignment camera 51 has a lens barrel, an objective lens, and a CCD image sensor, and captures alignment marks provided on the upper surface of the substrate S moving directly below it. The CCD image sensor in the alignment camera 51 is, for example, an area image sensor (two-dimensional image sensor).

The illumination unit 6 is connected to the alignment camera 51 via an optical fiber 61 and supplies illumination light to the alignment camera 51. The illumination light, guided by the optical fiber 61 extending from the illumination unit 6, is directed to the upper surface of the substrate S via the alignment camera 51's lens barrel. The reflected light from the substrate S is then incident on the CCD image sensor via the objective lens. This captures the upper surface of the substrate S, and an image is acquired. The alignment camera 51 is electrically connected to the control unit 9 and acquires the image in response to instructions from the control unit 9, transmitting this image to the control unit 9.

The control unit 9 acquires the position of the alignment marks indicated by the image captured by the alignment camera 51. The control unit 9 also controls the exposure unit 4 based on the position of the alignment marks, adjusting the pattern of the laser light irradiated from the exposure head 41 onto the substrate S during the exposure operation. Then, the control unit 9 irradiates the substrate S with modulated laser light from the exposure head 41 according to the pattern to be drawn, thereby drawing the pattern on the substrate S.

The control unit 9 performs various processes by controlling the operation of each of the above-described units. For this purpose, the control unit 9 includes a CPU (Central Processing Unit) 91, memory (RAM) 92, storage 93, input unit 94, display unit 95, and interface unit 96. The CPU 91 reads and executes a control program 931 pre-stored in the storage unit 93, and performs various operations described later. The memory 92 is used for calculation processing by the CPU 91, or for short-term storage of data generated as a result of calculation processing. The storage unit 93 stores various data and control programs long-term. Specifically, the storage unit 93 is a non-volatile storage device such as a flash memory device or a hard disk drive device, and in addition to the control program 931 executed by the CPU 91, it stores, for example, CAD (Computer-Aided Design) data 932, which is design data representing the content of the pattern to be drawn.

The input unit 94 receives user input and, for this purpose, has an appropriate input device such as a keyboard, mouse, or touch panel (not shown). The display unit 95 notifies the user by displaying various information and, for this purpose, has an appropriate display device, such as a liquid crystal display panel. The interface unit 96 manages communication with external devices. For example, the interface unit 96 functions when the exposure apparatus 1 receives a control program 931 and CAD data 932 from an external source. For this purpose, the interface unit 96 may also have a function for reading data from an external recording medium.

The CPU 91 executes the control program 931 to implement functional blocks such as the exposure data generation unit 911, exposure control unit 912, focus control unit 913, and stage control unit 914 in software. Note that at least a portion of each of these functional blocks may be implemented by dedicated hardware.

The exposure data generation unit 911 generates exposure data for modulating the light beam according to the pattern, based on the CAD data 932 read from the storage unit 93. If the substrate S is deformed, such as by distortion, the exposure data generation unit 911 modifies the exposure data according to the amount of distortion in the substrate S, enabling drawing that matches the shape of the substrate S. The exposure data is sent to the exposure head 41, which modulates the laser light emitted from the light irradiation unit 40 according to the exposure data. The modulated light beam, thus modulated according to the pattern, is irradiated onto the substrate S, partially exposing the surface of the substrate S and drawing the pattern.

The exposure control unit 912 controls the light irradiation unit 40 to emit a laser beam with predetermined power and spot size. The focus control unit 913 controls the projection optical system (described later) provided on the exposure head 41 to focus the laser beam onto the surface of the substrate S.

The stage control unit 914 controls the stage drive mechanism 3 to realize the movement of stage 2 for alignment adjustment and the movement of stage 2 for scanning during exposure. During alignment adjustment, the position of stage 2 is adjusted in the X, Y, Z, and θ directions so that the relative positional relationship between the substrate S placed on stage 2 and the exposure head 41 at the start of exposure is predetermined. Meanwhile, during scanning, a main scanning movement is performed by moving stage 2 in the Y direction at a constant speed to allow the substrate S to pass below the exposure head 41, and a step-by-step movement in the X direction at a constant pitch (sub-scanning movement) is performed.

Figure 3 shows a schematic configuration of the light irradiation unit. The light irradiation unit 40, in addition to the laser emission unit 43 and spatial light modulator 410 described above, includes optical elements such as an incident angle conversion unit 441, a splitting lens 442, an optical path adjustment difference generation unit 443, a focusing lens 444, and a projection optical system 414. The incident angle conversion unit 441, splitting lens 442, optical path adjustment difference generation unit 443, and focusing lens 444 together constitute the illumination optical system 44.

The laser beam emitted from the laser emission unit 43 enters the splitting lens unit 442 via the incident angle conversion unit 441, and then enters the optical path length difference generation unit 443. As described later, the light emitted from the optical path length difference generation unit 443 is a light beam with a flattened spot shape, with the horizontal direction (X direction) as the long axis. The light beam is further narrowed in the short axis direction by the focusing lens 444 to become a line light beam, which enters the spatial light modulator 410 of the exposure head 41. The light emitted from the spatial light modulator 410 is a light beam modulated by the exposure data, and this is irradiated onto the substrate S on the stage 2 via the projection optical system 411.

The detailed structure of the illumination optical system 44 will be explained later; here, we will first describe the structure of the exposure head 41, which is part of the light irradiation unit 40.

Figure 4 is a schematic diagram illustrating an example of the detailed configuration of an exposure head. As shown in Figure 4, the exposure head 41 is equipped with a spatial light modulator 410 having a diffractive optical element 411. Specifically, the spatial light modulator 410, mounted on the upper part of a support column 400 extending vertically (Z-direction) from the exposure head 41, is supported by the support column 400 via a movable stage 412, with the reflective surface of the diffractive optical element 411 facing downwards.

In the exposure head 41, the diffractive optical element 411 is positioned so that the normal to its reflective surface is inclined with respect to the direction of propagation of the incident light beam L. Light emitted from the illumination optical system 53 passes through the aperture of the support column 400, enters the mirror 413, is reflected by the mirror 413, and then irradiates the diffractive optical element 411. The state of each channel of the diffractive optical element 411 is then switched by the control unit 9 according to the exposure data, thereby modulating the laser light beam L incident on the diffractive optical element 411.

Furthermore, the laser light reflected from the diffractive optical element 411 as zero-order diffracted light enters the lens of the projection optical system 414, while the laser light reflected from the diffractive optical element 411 as first-order or higher diffracted light does not enter the lens of the projection optical system 414. In other words, the system is configured so that basically only the zero-order diffracted light reflected by the diffractive optical element 411 enters the projection optical system 414. The diffractive optical element 411 is positioned so that the zero-order diffracted light is emitted in the (-Z) direction. For example, a GLV (Grating Light Valve; "GLV" is a registered trademark of Silicon Light Machines) element can be suitably applied as the diffractive optical element 411.

Light passing through the lens of the projection optical system 414 is focused by the focusing lens 415 and guided onto the substrate S as a downward exposure beam with the (-Z) direction of travel, at a predetermined magnification. The projection optical system 414 constitutes a reduction optical system. This focusing lens 415 is attached to the focus drive mechanism 416. Then, in response to control commands from the focus control unit 913 of the control unit 9, the focus drive mechanism 416 raises and lowers the focusing lens 415 along the vertical direction (Z-axis direction), thereby adjusting the convergence position of the exposure beam emitted from the focusing lens 415 to the upper surface of the substrate S.

As shown along the optical path of the laser beam L indicated by the dashed line in Figure 4, the laser beam L guided from the light irradiation unit 40 to the exposure head 41 has a beam spot shape that extends uniformly in an elongated shape in the X direction, with the X direction as the long axis and the Z direction as the short axis. On the other hand, the modulated laser beam Lm after modulation by the optical modulator 410 has the X direction as the long axis and the Y direction as the short axis, and the intensity at each position in the X direction is modulated according to the exposure data. Furthermore, the exposure beam Le emitted from the projection optical system 414 toward the substrate S is a reduced version of the modulated laser beam Lm in the X and Y directions. By irradiating the surface of the substrate S with this narrowed exposure beam Le, a fine pattern can be drawn on the surface of the substrate S.

By irradiating the substrate S with an exposure beam Le modulated according to the exposure data, and moving the exposure head 41 and the substrate S relative to each other in the Y direction, a band-shaped region of the substrate S with a width equivalent to the spot size of the exposure beam Le in the X direction and extending in the Y direction can be exposed. By repeatedly performing exposure while sequentially changing the relative position of the exposure head 41 and the substrate S in the X direction, the entire substrate S can eventually be exposed.

In this manner, by combining scanning movements in the Y direction and scanning movements in the X direction between the exposure head 41 and the substrate S, the entire substrate S can be drawn. In this specification, scanning movement in the Y direction is referred to as "main scanning movement," and the Y direction is referred to as "main scanning direction." On the other hand, scanning movement in the X direction is referred to as "sub-scanning movement," and the X direction is referred to as "sub-scanning direction." In this embodiment, these scanning movements are achieved by moving the stage 2, which supports the substrate S, relative to the fixed exposure head 41.

Multiple exposure units 4 having the above configuration can be provided at different positions in the X direction. In this embodiment, five sets of exposure units 4, each having the same configuration, are provided. By emitting the exposure beam Le in parallel and performing drawing, the throughput of the drawing process is improved. Although these exposure units 4 can operate independently of each other, their scanning movement relative to the substrate S is uniform due to their structure.

Next, the structure of the laser emission unit 43 and the illumination optical system 44 within the light irradiation unit 40 will be described.

Figure 5 shows a schematic configuration of the laser emission unit. Several configurations are possible for the laser emission unit 43, as shown in Figures 5(a) and 5(b). In the configuration example shown in Figure 5(a), the laser emission unit 43a is equipped with multiple light source units 430a. Seven sets of light source units 430a are used here, but the number of light source units is not limited to this and can be arbitrary.

Each light source unit 430a includes a laser light source 431 that emits laser light, a collimator lens 432, and a focusing lens 433. The laser light source 431 is, for example, a laser diode that outputs laser light of a predetermined wavelength. The collimator lens 432 converts the laser light emitted from the laser light source 431 into collimated light. The focusing lens 433 focuses the collimated laser light and emits it as a focused beam.

As shown by the dashed-dotted line in the figure, each light source unit 430a is arranged so that its respective output light beams intersect at a single point. Specifically, each light source unit 430a is arranged so that the centerlines of the emitted light, shown by the dashed-dotted line, travel along the same XY plane, and that they intersect at a single point Pa within that XY plane.

On the other hand, in the laser emission unit 43b of the configuration example shown in Figure 5(b), a light source unit 430b is provided, having a laser light source 431, a collimator lens 432, and a focusing lens 433, similar to the configuration example described above. Each laser light source 431 emits laser light in the same direction (Y direction in this example) within the same XY plane. That is, the laser light emitted from each laser light source 431 is parallel to each other.

Wedge prisms 434 (4341-4347) are provided along each optical path. The (+Y) end face of each wedge prism 4341-4347 is tilted relative to the XZ plane so that the emitted light from each prism intersects at a single point Pb on the XY plane. The deviation from parallelism in the laser light emitted from each laser light source 431 can be corrected by adjusting the focusing lens 433 and the wedge prism 434 in the Y direction, thereby eliminating the deviation relative to point Pb on the XY plane.

The laser emission unit 43 can be suitably configured using either of the two configuration examples 43a and 43b described above. Therefore, in the following description, these will not be distinguished and will simply be referred to as "laser emission unit 43." Furthermore, even if the configuration illustrated in the figure corresponds to either configuration example 43a or 43b, the other configuration example can be applied without any problems.

From a parts manufacturing perspective, the configuration shown in Figure 5(b), in which the laser light sources 431 are arranged in a single, linear line, is advantageous. Especially when there are many laser light sources 431, the configuration shown in Figure 5(a), which requires each laser light source 431 to be positioned at an appropriate angle, may make adjustment work complicated. Furthermore, when a water cooling mechanism is provided to cool the light sources, a linear arrangement of the laser light sources 431 is also advantageous. Additionally, it is desirable that the arrangement of each laser light source 431 in the XY plane be symmetrical with respect to the optical axis of the illumination optical system 44.

Figure 6 is a ray diagram showing the overall configuration of the illumination optical system and the optical path of the light beam. More specifically, Figure 6 shows the configuration of the illumination optical system 44 in the XY plane and the YZ plane, respectively. Note that in Figure 6 and the following figures, some rays have been omitted from the ray diagrams to improve readability. Specifically, for example, Figure 6 shows only the light emitted from the central laser and the two lasers at both ends of the seven laser light sources 431.

The illumination optical system 44, in addition to the main components described above—namely, the incident angle conversion unit 441, the splitting lens 442, the optical path length difference generation unit 443, and the focusing lens 444—also includes a Z-direction collimator lens 445, a Z-direction diffusion lens 446, a Z-direction focusing lens 447, and the like. These optical elements are arranged so that their optical axes coincide. In Figure 6, the optical axes are represented by dashed lines.

Multiple laser beams emitted from the laser emission unit 43 are incident on an incident angle conversion unit 441 located near their intersection. Specifically, a collimator lens 445 is provided on the side closer to the laser emission unit 43, and the light beams passing through this lens 445 are incident on the incident angle conversion unit 441. The collimator lens 445 is, for example, a cylindrical lens that has no power in the X direction but power in the Z direction. Therefore, the laser beam is collimated in the Z direction.

In the incidence angle conversion unit 441, a concave lens 4411 is positioned in front of the intersection point of the laser beams, and at a position where all laser beams emitted from each laser light source 430 can be incident. The concave lens 4411 has power in the X direction and no power in the Z direction. Furthermore, a convex lens 4412 is positioned behind the concave lens 4411 in the optical path of the laser beam. As will be explained next, the convex lens 4412 is positioned to form a beam expander with respect to the concave lens 4411.

Figure 7 shows a more detailed configuration and operation of the incident angle conversion unit. The incident angle conversion unit 441 of this embodiment has the configuration shown in Figure 7(a). When the focal length of the concave lens 4411 is represented by f1 and the focal length of the convex lens 4412 by f2, the two lenses are positioned in the positional relationship shown in Figure 7(a). That is, the convex lens 4412 is positioned such that its front focal position coincides with the focal position of the concave lens 4411.

This combination of lenses corresponds to a configuration known as a Galilean beam expander. Beam expanders are generally used to expand (or contract) the beam diameter of collimated light incident along the optical axis. However, in this embodiment, as shown in the ray diagram of Figure 7(a), light is incident from multiple directions on the concave lens 4411 from the laser irradiation unit 43, and the direction of incidence is not necessarily aligned with the optical axis.

Under these conditions, light incident on the concave lens 4411 with a relatively large divergence angle is diffused by the concave lens 4411 and then focused by the convex lens 4412, resulting in a smaller divergence angle for the emitted light compared to the incident light. This light with its divergence angle suppressed then enters the split lens 442. In other words, the incident angle conversion unit 441 reduces the magnitude of the incident light's divergence as seen from the split lens 442, and quantitatively reduces the maximum incident angle of the incident light relative to the split lens 442.

Returning to Figure 6, let's continue the explanation of the illumination optical system 44. The configuration of the splitting lens 442 and the optical path length difference generation unit 443 is the same as that described in Patent Document 1. That is, the splitting lens (fly-eye lens) 442 has a plurality of lenses 4421 arranged perpendicular to the optical axis and in the X direction, and splits the light emitted from the incident angle conversion unit 441 using the plurality of lenses 4421. On the other hand, the optical path length difference generation unit 443 has a plurality of light-transmitting sections arranged perpendicular to the optical axis and having different optical path lengths, and causes the light that has passed through the splitting lens 442 to be incident on each of the plurality of light-transmitting sections. The structure and operation of these are described in detail in Patent Document 1 (Japanese Patent No. 6383166), so the explanation is omitted here. In short, these together have the function of splitting the incident beam light into a plurality of beams arranged at a constant pitch in the X direction and adjusting their optical path lengths.

Figure 8 is a ray diagram showing light passing through the splitting lens and the optical path length difference generation unit. In the example shown in Figure 8(a), light incident from the (-Y) side end face of the splitting lens 442 is emitted from the (+Y) side end face of the splitting lens 442 and the (+Y) side end face of the optical path length difference generation unit 442. On the other hand, in the example shown in Figure 8(b), some of the light incident on the optical path length difference generation unit 442 is emitted from its side and dissipates without reaching the (+Y) side end face. Such light dissipation occurs when the maximum incident angle of light incident on the splitting lens 442 is large. This resulting light dissipation reduces the overall light intensity and also reduces the uniformity of light intensity in the X direction.

When increasing the number of laser light sources 431 to increase light intensity, the structural arrangement of arranging them in the X direction inevitably leads to a larger incident angle of light from the laser light sources 431 located at the ends to the splitting lens 442. In other words, the divergence angle of the incident light to the splitting lens 442 increases.

By providing an incident angle conversion unit 441 between the laser emission unit 43 and the splitting lens 442, it is possible to reduce the divergence angle of the incident light with respect to the splitting lens 442 and bring it closer to parallel light. As a result, the dissipation of light caused by the divergence of the incident light described above can be suppressed. For example, when light with a maximum inclination of approximately 9 degrees with respect to the optical axis is incident on the incident angle conversion unit 441, using a concave lens 4411 with f1 = -11 m and a convex lens 4412 with f2 = 100 mm allows light with a maximum inclination of approximately 1 degree to be incident on the splitting lens 443 from the incident angle conversion unit 441.

Furthermore, the incident angle conversion unit 441 not only converts the light from the multiple laser light sources 431 into light that is nearly parallel as a whole, but also adjusts the X-direction spot size of the resulting light beam to match the size of the splitting lens 442. In other words, the incident angle conversion unit 441 ensures that light is incident evenly on each of the multiple lenses 4421 that constitute the splitting lens 442. This can be described as functioning as a beam expander, capable of appropriately expanding or contracting the spot size of the incident light beam.

In terms of suppressing the divergence angle of incident light, a similar effect can be achieved by increasing the distance between the laser emission unit 43 and the splitting lens 442, thereby reducing the incident angle. However, in that case, the optical path length increases, inevitably leading to an increase in the overall size of the illumination optical system 40. The incident angle conversion unit 441 of this embodiment is more preferable because it can reduce the incident angle without extending the optical path length.

In addition to the Galilean type beam expander described above, there is also a Keplerian type beam expander that combines two convex lenses. Such a Keplerian type beam expander can also be applied to the incident angle conversion unit 441. That is, as shown in Figure 7(b), the convex lens 4413 is positioned behind the intersection point of the multiple light beams emitted from the laser emission unit 43, at a position where these light beams can be incident. The convex lens 4413 has power at least in the X direction.

The other convex lens 4414 is positioned such that its front focal point is the rear focal point of the convex lens 4413. The convex lens 4414 has power at least in the X direction. In Figure 7(b), the symbols f1 and f2 indicate the focal lengths of the convex lenses 4413 and 4414, respectively. This is how the Keplerian beam expander is constructed. Even with this configuration, as shown in the ray diagram in Figure 7(b), the light emitted from the laser emission unit 43 with a relatively large divergence angle can be incident on the splitting lens 442 as light with a smaller divergence angle.

Comparing the configurations shown in Figures 7(a) and 7(b), the configuration in Figure 7(a) has the advantage of allowing for a shorter optical path length if the lens magnification is the same, and is less susceptible to the effects of dust and other particles in the optical path because the beam is not focused. On the other hand, the configuration in Figure 7(b) can be realized by combining convex lenses, and has the advantage of being easier to adjust because the beam is focused between the lenses.

Furthermore, in the incident angle conversion unit 441, in order to achieve a desired beam expansion (or contraction) ratio between the incident and outgoing light, the arrangement of the two lenses must be determined so as to satisfy the configuration requirements of a Galilean or Keplerian beam expander, according to their respective focal lengths. On the other hand, for the sole purpose of adjusting the beam divergence angle, some variation in the lens arrangement is permissible. That is, the arrangement of the two lenses does not need to strictly satisfy the requirements of a beam expander.

Furthermore, the objective of adjusting the beam divergence angle can, to some extent, be achieved with a single concave lens. However, as will be explained below, good results are not always obtained with incident angle transformation using a single lens.

By appropriately setting the lens characteristics, it is possible to convert incident light into near-parallel light and suppress the divergence angle even with a single concave lens. However, in reality, when trying to suppress the divergence of light after passing through a concave lens, the curvature of the lens surface cannot be made very large. In that case, the ratio of the spot size of the incident light beam to the spot size of the emitted light beam is not necessarily large, and the individual light beams emitted from the laser emission unit 43 enter the splitting lens 442 without being greatly expanded. In this case, the individual beam spots are generally considerably smaller than the diameters of the individual lenses constituting the splitting lens 442, making it difficult to achieve the objective of uniformly illuminating each lens.

Therefore, in this embodiment, the principle of a beam expander combining two lenses is utilized. This configuration offers excellent effectiveness in angle-of-incident conversion (reduction of divergence angle) and its controllability, and the beam spot size can be easily adjusted by appropriately selecting the lens magnification.

Returning to Figure 6, the light beam emitted from the optical path length difference generation unit 443 enters the Z-direction diffusion lens 446. The Z-direction diffusion lens 446 is a concave lens that has power in the Z direction but no power in the X direction. Therefore, the light beam emitted from the Z-direction diffusion lens 446 diffuses in the Z direction.

This light beam enters the image plane via the focusing lens 444 and the Z-direction focusing lens 447. In this case, the image plane is the light-receiving surface of the diffractive optical element 414. The focusing lens 444 is a convex lens with power in both the X and Z directions, converging the light beam onto the image plane. As a result, multiple light beams, aligned in the X direction and emitted from the splitting lens 442, are superimposed on the image plane. Since these light beams are coherent light, interference can occur during superposition. The optical path length difference generation unit 443 avoids interference by creating a difference in the optical path length of each light beam.

On the other hand, in the Z direction, the light beam, which has been initially spread by the Z-direction diffusion lens 446, is then significantly narrowed by the two focusing lenses 444 and 447. As a result, a line light beam L, which has a flattened and uniform intensity in the X direction and a small spread in the Z direction, is incident on the image plane (diffractive optical element 414). As shown in Figure 4, this line light beam L is modulated by the diffractive optical element 414 of the spatial light modulator 410, and the modulated light beam Lm is reduced by the projection optical system 414 and irradiated onto the substrate S as an exposure beam Le.

Next, the optical characteristics required for the incident angle conversion unit 441 will be explained with reference to Figure 9. Figure 9 shows the relationship between the incident light to the incident angle conversion unit and the incident light to the split lens. As shown in Figure 9, the maximum incident angle allowed for the incident light to the split lens 442 is represented by the symbol θ1. Here, the maximum incident angle θ1 is the maximum incident angle at which the light incident on the split lens 442 is emitted from the optical path length difference generation unit 443 without dissipation. In other words, in order to prevent light dissipation, the incident angle of the light incident on the split lens 442 must be less than or equal to the maximum incident angle θ1. The maximum incident angle θ1 depends on the diameter and length of each lens constituting the split lens 442 and the length of the optical path length difference generation unit 443.

In order to make the incident angle of light incident on the split lens 442 from the incident angle conversion unit 441 less than or equal to the maximum incident angle θ1, the condition that the incident angle θ0 of the light incident on the incident angle conversion unit 441 must satisfy is given by the following equation:
θ1 ≥ 1 / |f2/f1| × θ0 = |f1/f2| × θ0 … (Equation 1)
Or a modified version of this,
θ0≦|f2/f1|×θ1… (Formula 2)
This can be expressed as follows. When the equality holds, the allowable value of the incident angle from the laser irradiation unit 43 to the incident angle conversion unit 441 can be maximized. The focal lengths f1 and f2 of the two lenses 4411 and 4412 should be set such that this condition is met and an appropriate magnification (or reduction) is obtained that results in a beam spot size that allows light to be incident evenly on each lens constituting the split lens 442. In the figure, the symbol F indicates the focal point of the two lenses 4411 and 4412.

As described above, in this embodiment, laser light emitted from multiple laser light sources 431 arranged in the X direction is superimposed by the illumination optical system 44 to generate a line light beam L having a flattened beam spot shape with the X direction as its long axis. An incident angle conversion unit 441 is provided between the multiple laser light sources 431 and the splitting lens 442 to reduce the incident angle to the splitting lens 442.

This allows the incident angle to the splitting lens 442 to be kept small, even when the number of laser light sources 431 is large and the divergence angle of the light emitted from them is large. As a result, in this embodiment, the light beam emitted from the laser light source 431 is reliably guided to the end face of the splitting lens 442 and the output side (+Y side) of the optical path length difference generation unit 443, preventing light dissipation from the sides. Consequently, it is possible to generate a high-intensity line light beam with a uniform intensity distribution.

The incident angle conversion unit 441 can be realized by a combination of a concave lens 4411 and a convex lens 4412, or a combination of a convex lens 4413 and a convex lens 4414, which share a common optical axis. The two lenses are positioned in a manner that satisfies the conditions for forming a beam expander. By using such an optical system under conditions where light is incident from an oblique direction relative to the optical axis, the spread of the emitted light, i.e., the incident angle to the subsequent stage, can be made smaller than the incident angle of the light incident on the optical system.

Furthermore, the incidence angle conversion unit 441 functions as a beam expander, allowing light adjusted to an appropriate spot size to be incident on the subsequent splitting lens 442. Therefore, light can be uniformly incident on each lens 4421 constituting the splitting lens 442, and the light intensity distribution along the long axis of the final line beam, which is generated by the synthesis of the emitted light from them, can be made uniform.

As described above, in the exposure apparatus 1 of this embodiment, the light irradiation unit 40 functions as the "light irradiation unit" of the present invention, the spatial light modulator 410 functions as the "light modulator" of the present invention, the projection optical system 414 functions as the "projection optical system" of the present invention, and the control unit 9 functions as the "control unit" of the present invention. Furthermore, the light irradiation unit 40 corresponds to the "light irradiation device" of the present invention.

Furthermore, in the above embodiment, the illumination optical system 44, which includes the laser light source 431, the incident angle conversion unit 441, the splitting lens 442, the optical path length difference generation unit 443, and the focusing lens 444, functions as the "illumination optical system" of the present invention. Additionally, the collimating lens 445 and the diffusing lens 446 function as the "collimating lens" and "diffusing lens" of the present invention, respectively.

In the incident angle conversion unit 441, the concave lens 4411 and the convex lens 4413 correspond to the "first lens" of the present invention, while the convex lenses 4412 and 4414 correspond to the "second lens" of the present invention. Furthermore, the XY plane in the above embodiment corresponds to the "plane" as defined in the present invention.

Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from its spirit. For example, in the above embodiment, the number of laser light sources 431 arranged in the laser emission unit 43 is 7, but this is not limited to this. When there are a small number of laser light sources, the spread of light can be kept small, so an incident angle conversion unit is not necessarily required. However, the present invention is particularly effective when the number of laser light sources is large.

Furthermore, to further increase the beam light intensity, it is conceivable to arrange multiple laser light sources in the Z direction. An example of such a configuration is to combine the light from multiple laser light sources arranged in the Z direction into a single light beam along the XY plane using an appropriate optical system, and then further combine multiple such light beams within the XY plane. In such a case, by treating each light beam combined in the Z direction in the same manner as the light beams emitted from each laser emission unit 43 in the above embodiment, a configuration for applying the present invention can also be conceived.

Furthermore, while a GLV element, which is a one-dimensional diffractive optical element, can be suitably applied as the "optical modulator" of the present invention in the above embodiment, other types of optical modulators can also be applied. For example, two-dimensional diffractive optical elements or DMD (Digital Micro Mirror Device) elements, which control reflection by arranging a large number of fine mirrors, can be used as optical modulators.

Furthermore, while the exposure apparatus 1 of the above embodiment incorporates a light irradiation unit 40 corresponding to the "light irradiation apparatus" according to the present invention, it is also possible to consider a standalone light irradiation unit 40 as an embodiment of the present invention. For example, the present invention can be implemented by replacing the light irradiation unit in an existing exposure apparatus with that of this embodiment, or by improving it as shown in the light irradiation unit 40 of this embodiment.

As described above with examples of specific embodiments, the incident angle conversion unit of the light irradiation device according to the present invention can be realized using either a concave lens and a convex lens, or a convex lens and a convex lens as the combination of the first and second lenses. The combination of a concave lens and a convex lens allows for the application of a so-called Galilean beam expander configuration, while the combination of a convex lens and a convex lens allows for the application of a so-called Keplerian beam expander configuration. In either case, it is possible to reduce the incident angle of light to the splitting lens unit, thereby suppressing light dissipation from the splitting lens unit and the optical path length difference generation unit.

Furthermore, for example, the first lens may not possess power in the direction perpendicular to the plane. The incident angle conversion unit is provided for the purpose of adjusting the incident angle in the direction along the plane, and may have no effect in the direction perpendicular to the plane. This allows for independent design of the optical system in the direction along the plane and the direction perpendicular to it, increasing design flexibility.

Furthermore, for example, the arrangement of multiple laser light sources can be made symmetrical with respect to the optical axis in a plane. By ensuring that the light entering the first lens at an angle to the optical axis is incident from a direction symmetrical to the optical axis, the uniformity of the light in the plane can be improved.

Furthermore, for example, a collimating lens with power in a direction perpendicular to the plane may be placed between the laser light source and the incident angle conversion unit. This configuration suppresses the diffusion of light in the direction perpendicular to the plane, ensuring that the emitted light from the laser light source is reliably guided to the incident angle conversion unit and the splitting lens unit.

In this case, for example, a diffusing lens with power in a direction perpendicular to the plane may be placed between the optical path length difference generation unit and the focusing lens. With such a configuration, by diffusing the light in a direction perpendicular to the plane before reaching the focusing lens, it becomes possible to ultimately focus the light significantly in a direction perpendicular to the plane.

Furthermore, when θ1 is the divergence angle of the emitted light from multiple laser light sources as seen from the first lens, θ0 is the maximum incident angle of light that can enter the divided lens section and pass through the optical path length difference generation section, f1 is the focal length of the first lens, and f2 is the focal length of the second lens, the following relationship exists:
θ1≧｜f1/f2｜×θ0
If the above equation is satisfied, the light incident from the laser light source can be emitted from the output end of the optical path length difference generation unit without being dissipated. In the above equation, the equality sign indicates the condition under which θ0 is the maximum allowable angle of incidence of light to the first lens. In other words, when the maximum angle of incidence θ0 from multiple laser light sources is predetermined, by selecting the first and second lenses to satisfy the above equation, it is possible to suppress light dissipation in the subsequent stages.

This invention is particularly suitable for technical fields involving the exposure of substrates to form patterns on substrates such as semiconductor substrates, semiconductor package substrates, printed circuit boards, or glass substrates.

1. Exposure apparatus 2. Stage 9. Control unit 40. Light irradiation unit 44. Illumination optical system 410. Spatial light modulator (light modulator)
414 Projection optical system 431 Laser light source 441 Incident angle conversion unit 4411 Concave lens (first lens)
4412 Convex lens (second lens)
4413 Convex lens (first lens)
4414 Convex lens (second lens)
442. Segmented lens (segmented lens section)
443 Optical path length difference generation unit 444 Focusing lens 445 Collimating lens 446 Diffusing lens L Laser light beam Le Exposure beam S Substrate

Claims (9)

Multiple laser light sources are arranged such that the centerlines of the emitted light beams are contained in the same plane and intersect at a point within that plane,
The system includes an illumination optical system that combines laser light emitted from the aforementioned multiple laser light sources to generate a single laser light beam and irradiates the surface to be illuminated,
The illumination optical system is
An incident angle conversion unit including a first lens positioned at the location into which light emitted from each of the plurality of laser light sources is incident, and a second lens positioned in a positional relationship with the first lens to form a beam expander,
A splitting lens section having a plurality of lenses arranged perpendicular to the optical axis of the incident angle conversion section and along the plane, which splits the light emitted from the incident angle conversion section using the plurality of lenses,
An optical path length difference generating unit having a plurality of light-transmitting sections arranged perpendicular to the optical axis and having different optical path lengths, and which causes light that has passed through the plurality of lenses to be incident on each of the plurality of light-transmitting sections,
A light irradiation device having a focusing lens section that overlaps the irradiation areas of light emitted from the plurality of light-transmitting sections on the surface to be irradiated. The light irradiation device according to claim 1, wherein the first lens is a concave lens and the second lens is a convex lens. The light irradiation apparatus according to claim 1, wherein the first lens and the second lens are convex lenses. The light irradiation device according to any one of claims 1 to 3, wherein the first lens does not have power in a direction perpendicular to the plane. The light irradiation device according to any one of claims 1 to 3, wherein the arrangement of the plurality of laser light sources is symmetrical with respect to the optical axis in the plane. The light irradiation device according to any one of claims 1 to 3, wherein a collimating lens having power in a direction perpendicular to the plane is arranged between the laser light source and the incident angle conversion unit. The light irradiation device according to claim 6, wherein a diffusion lens having power in a direction perpendicular to the plane is arranged between the optical path length difference generating unit and the focusing lens. When θ1 is the divergence angle of the emitted light from the plurality of laser light sources as seen from the first lens, θ0 is the maximum incident angle of light that can enter the divided lens portion and pass through the optical path length difference generation portion, f1 is the focal length of the first lens, and f2 is the focal length of the second lens, the following relationship exists:
θ1≧｜f1/f2｜×θ0
A light irradiation device according to any one of claims 1 to 3, wherein the above is true. An exposure apparatus that draws a predetermined pattern by exposing the surface of a substrate,
A light irradiation unit having the same configuration as the light irradiation device described in claim 1,
A light modulator positioned at the location of the surface to be irradiated,
A control unit that controls the optical modulator based on exposure data representing the pattern to be drawn, thereby modulating the laser light beam,
An exposure apparatus comprising a projection optical system for injecting the modulated laser beam onto the substrate.