Projection exposure device and projection exposure method

Abstract

The projection exposure apparatus (10) comprises: a mask mark illumination light source (21) capable of irradiating a mask mark (MM) with exposure light itself or first alignment light (L1) having substantially the same wavelength as the exposure light; and an alignment unit (30) having a workpiece mark illumination light source (31) capable of irradiating a workpiece mark (WM) with second alignment light (L2) having a different wavelength from the exposure light, an imaging device (32), and an imaging optical system (40). The imaging optical system (40) comprises: a first dichroic prism (41) for synthesizing the first alignment light (L1) and light from the workpiece mark (WM) and emitting the resultant light to the imaging device (32); and an optical path length changing optical system (42) for branching and converging the first alignment light (L1) so that the optical positional relationships of the images (MMI) of the workpiece mark (WM) and the mask mark (MM) relative to the imaging device (32) are equal. Thus, a projection exposure apparatus and a projection exposure method capable of high-precision alignment even in a small-sized exposure area can be provided.

Description

Technical Field

[0001] The present invention relates to a projection exposure device and a projection exposure method, and in particular to a projection exposure device and a projection exposure method that can perform high-precision alignment even for a small-sized exposure area. Background Art

[0002] When semiconductor wafers, printed wiring boards, liquid crystal substrates, and the like are manufactured using photolithography technology, a projection exposure apparatus is used that projects a mask pattern onto a substrate using a projection lens and transfers the pattern to the substrate.

[0003] In printed circuit boards (PCBs), the increasing speed, multifunctionality, and miniaturization of electronic devices are driving the demand for multilayered, high-density, and miniaturized PCBs. Therefore, when transferring a mask pattern to a workpiece, it is crucial to accurately align the next pattern with the previously formed pattern. Furthermore, in projection exposure equipment, the projection lens is designed to minimize aberration relative to the ultraviolet light used for exposure. Therefore, in the TTL (Through The Lens) alignment method, which forms alignment marks for the mask on the workpiece through the projection lens, it is preferred to use exposure light as the alignment light. On the other hand, because ultraviolet light can sensitize the workpiece's resist, research is underway to perform alignment without irradiating the workpiece with alignment light that has passed through the projection lens.

[0004] In the alignment device described in Patent Document 1, an exposure light irradiation device irradiates a mask with exposure light, projecting the mask's alignment marks onto a reflective member located on a workpiece stage, spaced apart from the workpiece securing area. The projected image is then captured and its relative position is stored. Subsequently, the exposure light irradiation is stopped, the workpiece stage holding the workpiece is moved to a position where the mask's alignment marks are projected onto the workpiece, and non-exposure light is irradiated onto the workpiece's alignment marks. The image of the workpiece's alignment marks is captured and their relative position is detected. Furthermore, the mask and workpiece are aligned by moving the workpiece and / or mask so that the positions of the two alignment marks overlap.

[0005] Patent document 2 discloses a projection exposure device comprising: a first illumination system for irradiating exposure illumination light onto a reticle matching mark arranged on the reticle side; and a second illumination system for irradiating a second illumination light having a wavelength wider than the first illumination light onto a chip matching mark arranged on the wafer side, wherein a detection device arranged on the opposite side of the light-receiving surface is used to detect images of the reticle matching mark and the chip matching mark formed on the light-receiving surface, and a signal corresponding to the relative positional relationship between the reticle matching mark and the chip matching mark is output.

[0006] The exposure apparatus described in Patent Document 3 includes an alignment lighting unit that irradiates alignment light using exposure light onto a mask-side alignment mark on a mask; and an alignment imaging unit that directs the alignment light emitted from the alignment lighting unit and passed through the mask and projection lens. Patent Document 3 discloses that the alignment imaging unit includes an imaging optical system that positions the mask relative to the incident alignment light so that an image of the mask-side alignment mark is formed in a dummy workpiece region that is identical to the target workpiece and at a different position from the target workpiece; and an imaging optical system that positions the target workpiece and the dummy workpiece region relative to the imaging device in the same optical position. This allows the alignment imaging unit to achieve extremely high alignment accuracy.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 9-82615

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 11-251233

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2011-253864 Summary of the Invention

[0012] Technical problem that the invention aims to solve

[0013] However, the position alignment device described in Patent Document 1 uses pre-stored mask alignment marks for alignment. Therefore, if interference such as temperature change occurs during the acquisition of the two alignment marks, the error caused by the interference cannot be taken into account, and alignment may not be performed with high precision.

[0014] Furthermore, in the exposure apparatus disclosed in Patent Documents 2 and 3, the light-receiving surface on which the alignment mark images of the mask are formed and the dummy workpiece area are arranged to extend over the workpiece exposure area on the opposite side of the detection device and the imaging device. Therefore, if the alignment marks of multiple workpieces are close together, there is a risk of interference between the multiple light-receiving surfaces and the dummy workpiece area. In recent years, in particular, in printed wiring boards and other applications, the demand for further miniaturization has increased the number of exposure area divisions and the need for high-resolution exposure, and alignment is desired even in small exposure areas.

[0015] The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a projection exposure apparatus and a projection exposure method that can perform high-precision alignment even in a small-sized exposure area.

[0016] Technical means to solve the problem

[0017] The above-mentioned object of the present invention is achieved through the following structure.

[0018] (1) A projection exposure apparatus that irradiates a mask with exposure light, projects a pattern formed on the mask onto a workpiece using a projection lens, and exposes the pattern on the workpiece, the projection exposure apparatus comprising:

[0019] a mask mark illumination light source capable of irradiating the alignment mark of the mask with the exposure light itself or light having substantially the same wavelength as the exposure light, that is, first alignment light;

[0020] a workpiece mark illumination light source capable of irradiating a second alignment light having a wavelength different from that of the exposure light toward the alignment mark of the workpiece; and

[0021] An alignment unit, the alignment unit comprising: an imaging device for acquiring an image of the alignment mark of the workpiece and the alignment mark of the mask based on the first alignment light; and an imaging optical system comprising a synthetic optical element for emitting synthetic light obtained by synthesizing the first alignment light emitted from the mask mark illumination light source and passing through the mask and the projection lens and the light from the alignment mark of the workpiece toward the imaging device, the imaging optical system being used to enable the imaging device to acquire the image of the alignment mark of the mask and the alignment mark of the workpiece as an image,

[0022] The imaging optical system includes an optical path length changing optical system that branches and converges the first alignment light from the first alignment light synthesized by the synthesizing optical element and the light from the alignment mark of the workpiece so that the optical path length of the first alignment light from the synthesizing optical element to the imaging device is longer than the optical path length of the light from the alignment mark of the workpiece from the synthesizing optical element to the imaging device.

[0023] The image of the alignment mark of the mask acquired by the imaging device is formed on the optical path of the optical path length changing optical system.

[0024] The optical positional relationship between the images of the alignment mark of the workpiece and the alignment mark of the mask with respect to the imaging device is equal.

[0025] (2) A projection exposure method,

[0026] A projection exposure method comprising the projection exposure apparatus described in (1),

[0027] The projection exposure method has the following features:

[0028] a step of aligning the mask and the workpiece based on the image of the alignment mark of the mask and the alignment mark of the workpiece acquired by the imaging device; and

[0029] A process of irradiating a mask with exposure light, projecting a pattern formed on the mask onto a workpiece using a projection lens, and exposing the workpiece to the pattern.

[0030] Effects of the Invention

[0031] According to the projection exposure apparatus and the projection exposure method of the present invention, when a plurality of alignment units are used for alignment, even in a small-sized exposure area, the alignment units will not interfere with each other, and high-precision alignment can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an explanatory diagram schematically showing the structure of the projection exposure apparatus of the invention.

[0033] Figure 2 This is a schematic diagram showing a state where alignment adjustment is performed by the TTL method using exposure light.

[0034] Figure 3 (a) is an enlarged view of the first dichroic prism, and (b) is an enlarged view of the second dichroic prism.

[0035] Figure 4 (a) is a schematic diagram showing a state in which the first alignment light emitted from the mask mark illumination light source and passing through the projection lens is incident on the imaging device via the imaging optical system including the optical path length changing optical system, and (b) is a schematic diagram showing a state in which the light from the alignment mark of the workpiece illuminated by the workpiece mark illumination light source is incident on the imaging device via the imaging optical system.

[0036] Figure 5 (a) is a diagram showing the configuration of alignment marks of four workpieces set at the four corners of a large exposure area together with an alignment unit, and (b) is a diagram showing the configuration of alignment marks of four workpieces set at the four corners of a small-sized exposure area formed by dividing the exposure area of ​​(a) into four parts together with an alignment unit.

[0037] Figure 6 It is an enlarged view of a main part showing a modified example in the case of using exposure light as a light source for illuminating a mask mark.

[0038] Figure 7 (a) is an enlarged view of a main part showing another modified example in the case of using exposure light as a light source for illuminating a mask mark, and (b) is a plan view showing a plurality of light shielding plates.

[0039] Explanation of symbols

[0040] 10 Projection exposure device

[0041] 18 Projection lens

[0042] 21 Light source for mask mark illumination

[0043] 30 Alignment Unit

[0044] 31 Light source for workpiece marking

[0045] 32 Camera

[0046] 40 Camera Optical System

[0047] 41 First dichroic prism (synthetic optical element)

[0048] 42 Optical system for changing optical path length

[0049] 43, 44 Prism

[0050] 45 joint surface (semi-transparent and semi-reflective mirror)

[0051] 46 lower surface (color separation surface)

[0052] 48 second dichroic prism

[0053] 49 reflective optical elements

[0054] 51, 52 joint surface (color separation surface)

[0055] 53, 54, 55 prisms

[0056] 56 first reflecting surface (reflecting surface)

[0057] 57 second reflecting surface (reflecting surface)

[0058] 60, 60A~60D light shield

[0059] L1 First alignment light

[0060] L2 Second alignment light

[0061] LA Synthetic Light Axis

[0062] M Mask

[0063] MM mask mark (mask alignment mark)

[0064] Image of the alignment marks of the MMI mask

[0065] W workpiece

[0066] WM work mark (alignment mark of workpiece) DETAILED DESCRIPTION

[0067] Hereinafter, an embodiment of the projection exposure apparatus and the projection exposure method according to the present invention will be described in detail based on the accompanying drawings.

[0068] like Figure 1 As shown, the projection exposure apparatus 10 includes a light source 11 , a bandpass filter 12 , an integrator lens 13 , a collimator lens 14 , a plane mirror 15 , a mask stage 16 , a correction optical system 17 , a projection lens 18 , and a work stage 19 .

[0069] The light source unit 11 is constructed, for example, by arranging a plurality of LED light sources in a two-dimensional array, and emits light including ultraviolet rays as exposure light. The bandpass filter 12 cuts off light in wavelengths other than ultraviolet rays (for example, i-line). The light passing through the bandpass filter 12 is incident on the integrator lens 13. The integrator lens 13 is an optical system for offsetting the uneven illumination of the incident light and illuminating the mask M with a uniform illumination distribution. In addition, an aperture stop is arranged on the emission surface of the integrator lens 13. The collimating lens 14 emits the light incident from the integrator lens 13 in the form of parallel light. Then, the exposure light that becomes parallel light is reflected by the plane mirror 15 and emitted toward the mask M held on the mask stage 16. The exposure light that passes through the mask M is incident on the correction optical system 17.

[0070] The mask stage 16 holds the mask M having the pattern formed thereon so that it can move in a direction perpendicular to the optical axis EL of the exposure light by means of a mask driving mechanism (not shown). In addition, four alignment marks MM are formed on the mask M around the pattern, corresponding to the four alignment marks WM of the workpiece W described later (see FIG. Figure 2 ).

[0071] The correction optical system 17 deforms the pattern image of the mask M to be formed on the workpiece W based on the skew of the workpiece W. For example, this correction is performed by juxtaposing multiple glass plates along the optical axis and appropriately bending or rotating each glass plate. Furthermore, in addition to being fixedly disposed between the mask stage 16 and the projection lens 18, the correction optical system 17 may also be fixedly disposed on the projection lens 18, or may be arranged between the projection lens 18 and the workpiece stage 19.

[0072] The projection lens 18 appropriately zooms the image of the pattern formed on the mask M and forms it on the surface of the workpiece W. Furthermore, since the projection lens 18 uses ultraviolet light (i-rays) as exposure light, it is designed to minimize aberration relative to ultraviolet light (i-rays). Thus, the exposure light that has passed through the mask M enters the projection lens 18, and an image of the pattern on the mask M is formed on the workpiece W coated with the photosensitive material.

[0073] Furthermore, as exposure light, in addition to the i-line (wavelength: 365 nm), the h-line (wavelength: 405 nm), the g-line (wavelength: 436 nm), a combination of these lines, or wavelengths between these can be used.

[0074] The workpiece stage 19 holding the workpiece W can also be moved in a direction perpendicular to the optical axis EL of the exposure light by a workpiece drive mechanism (not shown). In particular, in this embodiment, the workpiece W has multiple exposure areas, and stepper exposure is performed while moving the exposure areas. Examples of the workpiece W include silicon wafers, glass substrates, and printed wiring boards.

[0075] Next, refer to Figure 2 When the pattern of the mask M is transferred onto the workpiece W by exposure, the alignment between the mask M and the workpiece W performed before the exposure transfer will be described.

[0076] The projection exposure apparatus 10 includes four mask mark lighting units 20 and four alignment units 30 corresponding to the respective mask mark lighting units 20. The four mask mark lighting units 20 are provided in correspondence with the four alignment marks MM (hereinafter, also referred to as mask marks MM) formed on the mask M, and the four alignment units 30 are provided in correspondence with the four alignment marks WM (hereinafter, also referred to as workpiece marks WM) formed on the workpiece W. Here, the mask mark lighting units 20 and the alignment units 30 have the same structure, so in the following description, reference is made to the respective alignment marks WM. Figure 2 One mask mark illumination unit 20 and one alignment unit 30 will be described.

[0077] The mask mark lighting unit 20 is arranged above the mask stage 16. The mask mark lighting unit 20 includes: a light source 21 for mask mark lighting, such as an LED, which emits first alignment light (i-line) L1 as ultraviolet light of the same wavelength as the exposure light; a collimating lens 22; and a reflecting prism 23. The collimating lens 22 emits the incident light as parallel light, and the reflecting prism 23 converts the direction of travel of the ultraviolet light, which has been parallelized by the collimating lens 22, into a direction orthogonal to the mask M. Alternatively, a reflecting mirror may be used instead of the reflecting prism 23. Alternatively, the mask mark lighting unit 20 may be arranged so that its optical axis is orthogonal to the mask M, without using the reflecting prism 23 or the reflecting mirror.

[0078] The mask mark illumination unit 20 is provided to be movable relative to the corresponding mask mark MM and emits first alignment light L1 toward the corresponding mask mark MM when performing alignment adjustment with the workpiece W. The first alignment light L1 passing through the mask M enters the correction optical system 17 and the projection lens 18 .

[0079] An alignment unit 30 is provided between the projection lens 18 and the workpiece W so as to be movable relative to the optical path of the first alignment light L1 from the projection lens 18 to the workpiece W. The alignment unit 30 includes an imaging device 32 , an imaging optical system 40 , and a workpiece mark illuminating light source 31 .

[0080] The imaging device 32 has sensitivity to at least the ultraviolet (i-ray) wavelength band and the visible light wavelength band, serving as the first alignment light L1, and can simultaneously capture an image MMI of the mask mark MM of the mask M and a workpiece mark WM of the workpiece W based on the first alignment light L1. The imaging device 32 may be an optical camera, but preferably includes an imaging element such as a CCD or CMOS sensor, and performs photoelectric conversion of light received by the imaging element and outputs the light as an electrical signal.

[0081] The imaging optical system 40 is used to enable the imaging device 32 to obtain the image MMI of the mask mark MM and the workpiece mark WM as an image, and has, in order of proximity to the imaging device 32, an imaging lens unit 33 with a built-in semi-transparent and semi-reflective mirror 34 and an imaging lens 35, an optical path length changing optical system 42, and a first color separation prism 41 as a synthetic optical element.

[0082] The first dichroic prism 41 is an optical element for emitting the synthesized light obtained by synthesizing the first alignment light L1 emitted from the mask mark illumination light source 21 and passing through the mask M and the projection lens 18, and the light from the workpiece mark WM of the workpiece W, toward the camera device 32. It is arranged below the projection lens 18 at the position where the first alignment light L1 passes.

[0083] Also refer to Figure 3 (a) The first dichroic prism 41 has the following structure: a pair of prisms 43 and 44 are joined by a joining surface 45 that is tilted 45° relative to the optical axis of the first alignment light L1 emitted from the projection lens 18. This joining surface 45 constitutes a so-called half-mirror surface. Furthermore, the prism 44, disposed below the joining surface 45, forms a dichroic surface. Specifically, a lower surface 46 of the prism 44, perpendicular to the optical axis of the first alignment light L1, reflects the first alignment light L1 and transmits the second alignment light L2. This dichroic surface prevents the ultraviolet light from reaching the workpiece W and sensitizing the photosensitive material when alignment is performed using the first alignment light L1, which is ultraviolet light.

[0084] The optical path length changing optical system 42 is an optical system that branches and converges the first alignment light L1, which is combined by the first dichroic prism 41 and the light from the workpiece mark WM, thereby changing the optical path length of the first alignment light L1. The optical path length changing optical system 42 comprises a second dichroic prism 48 positioned on the optical axis LA of the combined light emitted from the joint surface 45 of the first dichroic prism 41; and a pair of reflecting optical elements 49 positioned on a horizontal plane including the optical axis LA of the combined light, spaced from the second dichroic prism 48 and arranged parallel to the optical axis LA.

[0085] Also refer to Figure 3(b) The second dichroic prism 48 is formed by joining a plurality (three in the illustrated embodiment) of prisms 53, 54, and 55. The two orthogonal joining surfaces 51 and 52 formed between the prisms 53, 54, and 55 are each inclined 45° relative to the optical axis LA of the combined light emitted from the joining surface 45 of the first dichroic prism 41, constituting dichroic surfaces. Specifically, these joining surfaces 51 and 52 also reflect the first alignment light L1 and transmit the second alignment light L2.

[0086] The pair of reflective optical elements 49 is composed of a pair of prisms 58, 59. These reflective elements have a first reflective surface 56 arranged parallel to the joint surface 51 of the second dichroic prism 48, and a second reflective surface 57 arranged parallel to the joint surface 52 of the second dichroic prism 48. The first reflective surface 56 and the second reflective surface 57 are orthogonal to each other. Furthermore, the first alignment light L1 reflected by the joint surface 51 of the second dichroic prism 48 is reflected by the first reflective surface 56 and the second reflective surface 57 and enters the joint surface 52 of the second dichroic prism 48. This changes the optical path length of the first alignment light L1. Alternatively, the pair of prisms 58, 59 may be a pair of reflective mirrors.

[0087] The workpiece mark illumination light source 31 directs second aiming light L2, such as visible light, having a different wavelength from the exposure light, into the imaging lens unit 33. The light is reflected by a half-mirror 34, which is tilted 45° relative to the optical axis of the second aiming light L2. The light is then emitted coaxially with the optical axis LA of the combined light. The light then passes through the second dichroic prism 48 and the first dichroic prism 41 and illuminates the workpiece mark WM on the workpiece W. In other words, the second aiming light L2 directed from the imaging lens unit 33 constitutes coaxial epi-illumination, pseudo-arranged on the optical axis LA of the combined light.

[0088] The appearance of the workpiece mark WM may differ depending on the type of photosensitive material applied to the workpiece W. Therefore, an optical filter (not shown) that can switch to a wavelength that is easier to observe may be provided in the workpiece mark illumination light source 31 according to the type of photosensitive material.

[0089] In addition, in order to explain the optical path, Figure 2 The workpiece mark illumination light source 31 and the reflective optical element 49 are depicted as protruding upward, but in reality, Figure 2The workpiece mark illumination light source 31, imaging lens unit 33, second dichroic prism 48, and reflective optical element 49, arranged within the dotted line D, are arranged 90° rotated about the optical axis LA of the combined light. Specifically, the workpiece mark illumination light source 31 and reflective optical element 49 are arranged on a horizontal plane containing the optical axis LA of the combined light. Specifically, when viewed from above, the workpiece mark illumination light source 31 is attached to the side of the imaging lens unit 33, and the reflective optical element 49 is positioned to the side of the second dichroic prism 48. This allows the alignment unit 30 to advance and retract within the space between the projection lens 18 and the workpiece W without interfering with the projection lens 18 or the workpiece W.

[0090] In the imaging optical system 40 having such a structure, as shown in FIG. Figure 4 As shown in FIG. 1( a ), the first aiming light L1, after passing through the projection lens 18, is reflected by the lower surface 46 of the first dichroic prism 41, which constitutes the dichroic surface, and then further reflected by the joint surface 45, before entering the second dichroic prism 48. The first aiming light L1 incident on the second dichroic prism 48 is reflected by the joint surface 51 of the second dichroic prism 48, and further reflected by the first reflecting surface 56 and the second reflecting surface 57 of the reflecting optical element 49, before entering the joint surface 52 of the second dichroic prism 48. The first aiming light L1 reflected by the joint surface 52 passes through the half mirror 34 and the imaging lens 35 in the imaging lens unit 33 and reaches the imaging device 32.

[0091] On the other hand, Figure 4 As shown in FIG. 5( b ), the light from the workpiece mark WM illuminated by the second aiming light L2 is reflected by the joint surface 45 of the first dichroic prism 41, passes through the joint surfaces 51 and 52 of the second dichroic prism 48, the half mirror 34 in the imaging lens unit 33, and the imaging lens 35, and reaches the imaging device 32. Therefore, among the light from the second dichroic prism 48 to the imaging device 32, the first aiming light L1 and the light from the workpiece mark WM converge to form a combined light.

[0092] By disposing the optical path length changing optical system 42 (the second dichroic prism 48 and the reflecting optical element 49) between the first dichroic prism 41 and the imaging device 32, the optical path length of the first aiming light L1 from the first dichroic prism 41 to the imaging device 32 can be made longer than the optical path length of the light from the workpiece mark WM from the first dichroic prism 41 to the imaging device 32. Furthermore, an image MMI of the mask mark MM is formed on the optical path of the optical path length changing optical system 42. Thus, the image MMI of the mask mark MM becomes an aerial image on the optical path of the optical path length changing optical system 42, thereby minimizing the risk of foreign matter adhesion and enabling high-precision image capture by the imaging device 32.

[0093] The optical path length changing optical system 42 is configured to Figure 4 The optical path length L1L from the image MMI of the mask mark MM formed on the optical path of the first alignment light L1 to the imaging device 32 (strictly speaking, the image receiving surface of the imaging device 32) is Figure 4 The optical path length L2L from the workpiece mark WM to the imaging device 32 shown in (b) is set to the same length, and the optical positional relationship between the workpiece mark WM and the image MMI of the mask mark MM with respect to the imaging device 32 is set to be equal, so that the image MMI of the mask mark MM and the workpiece mark WM provided on the workpiece W can be captured by the imaging device 32 within the same field of view. That is, in the optical path of the first alignment light L1, the image MMI of the mask mark MM and the imaging device are in an optically conjugate positional relationship, and in the optical path of the second alignment light L2, the workpiece mark WM and the imaging device 32 are in an optically conjugate positional relationship.

[0094] Then, based on the positional relationship between the image MMI of the mask mark MM and the workpiece mark WM within the field of view of the camera device 32, the relative positions of the mask M and the workpiece W are moved as needed, and the position and shape of the image MMI of the mask mark MM are corrected by the correction optical system 17 to make the image MMI of the mask mark MM consistent with the workpiece mark WM, thereby aligning the mask M and the workpiece W.

[0095] Since the alignment operation is performed each time one exposure area EA is exposed, the influence of interference between the alignment operation and the exposure operation can be significantly suppressed, and the pattern of the mask M can be transferred with high accuracy.

[0096] like Figure 5 As shown, for each exposure area EA set on the workpiece W, one workpiece mark WM is provided at each of the four corners of the exposure area EA, for a total of four workpiece marks WM. In order to simultaneously capture the four workpiece marks WM using the imaging device 32, four alignment units 30 need to be positioned on each workpiece mark WM.

[0097] In particular, Figure 5 The exposure area EA1 shown in (a) is divided into four parts. Figure 5 In the small exposure area EA2 shown in (b), the intervals between workpiece marks WM are also narrow. In such an exposure area EA2, where workpiece marks WM are closely arranged, the alignment unit 30 lacks an optical system on the side opposite the imaging device 32 relative to the first dichroic prism 41. This allows multiple alignment units 30 to be positioned close to one another. This makes it easy to handle small exposure areas EA, significantly contributing to miniaturization and high-resolution exposure on printed circuit boards, etc.

[0098] As described above, in the projection exposure device 10 of this embodiment, even for a small-sized exposure area EA, alignment can be performed with extremely high precision by utilizing the TTL alignment method of allowing the same ultraviolet light (i line) as the exposure light to pass through the projection lens 18.

[0099] The present invention is not limited to the above-described embodiment, and appropriate modifications and improvements can be made.

[0100] For example, in the above embodiment, an example is described in which four alignment marks are provided on the mask and four alignment marks are provided on the workpiece. However, three alignment marks may be provided on the mask and three alignment marks may be provided on the workpiece to align the mask and the workpiece.

[0101] Furthermore, in the above embodiment, in addition to the light source unit 11, a light source is provided that emits light having substantially the same wavelength as the exposure light, namely, first alignment light L1, as a mask mark illumination light source for illuminating the mask alignment marks during alignment. However, the present invention is not limited to this. For example, the exposure light emitted from the light source unit 11 itself may be used as the first alignment light L1 to illuminate the mask alignment marks. In other words, the light source unit 11 may also function as a mask mark illumination light source.

[0102] When the exposure light is irradiated to the alignment mark MM of the mask M, as shown in FIG. Figure 6 As in the modified example shown in FIG, a light shielding plate 60 is used that can enter the top of the mask M during alignment. For example, if there are four observation locations, four holes 61 are formed on the light shielding plate 60 at positions corresponding to the alignment marks MM of the mask M (in FIG. Figure 6 ( 7 , only two holes are shown in the figure). During alignment, the light shielding plate 60 is positioned above the mask M to shield the exposure light directed to the exposure area, and to irradiate the exposure light to each alignment mark MM through the four holes 61. Furthermore, after alignment is completed, the light shielding plate 60 is retracted from above the mask M during exposure.

[0103] In addition, if Figure 7 As in the other modified examples shown, if the number of observation locations is four, four light shielding plates 60A to 60D that can access the top of the mask M may be used simultaneously. Each of the four light shielding plates 60A to 60D has a hole 61 corresponding to each alignment mark MM of the mask M. Thus, even if the position of each alignment mark MM changes depending on the mask M, the position of each light shielding plate 60A to 60D is moved in accordance with the position of each alignment mark MM, thereby enabling the change to be addressed without changing the light shielding plates 60A to 60D.

[0104] In addition, the present invention preferably uses a workpiece mark illumination light source that can suppress the height dimension of the alignment unit as in this embodiment, but other workpiece mark illumination light sources such as ring lighting may also be used if the height dimension allows.

[0105] As described above, this specification discloses the following contents.

[0106] (1) A projection exposure apparatus that irradiates exposure light onto a mask, projects a pattern formed on the mask onto a workpiece using a projection lens, and exposes the pattern to the workpiece, the projection exposure apparatus comprising:

[0107] a mask mark illumination light source capable of irradiating the alignment mark of the mask with the exposure light itself or light having substantially the same wavelength as the exposure light, that is, first alignment light;

[0108] a workpiece mark illumination light source capable of irradiating a second alignment light having a wavelength different from that of the exposure light toward the alignment mark of the workpiece; and

[0109] An alignment unit, the alignment unit comprising: an imaging device, the imaging device acquiring an image of the alignment mark of the mask and the alignment mark of the workpiece based on the first alignment light; and an imaging optical system, the imaging optical system comprising a synthetic optical element, the synthetic optical element emitting synthetic light obtained by synthesizing the first alignment light emitted from the mask mark illumination light source and passing through the mask and the projection lens and the light from the alignment mark of the workpiece toward the imaging device, the imaging optical system being used to enable the imaging device to acquire the image of the alignment mark of the mask and the alignment mark of the workpiece as an image,

[0110] The imaging optical system includes an optical path length changing optical system that branches and converges the first alignment light from the first alignment light synthesized by the synthesizing optical element and the light from the alignment mark of the workpiece so that the optical path length of the first alignment light from the synthesizing optical element to the imaging device is longer than the optical path length of the light from the alignment mark of the workpiece from the synthesizing optical element to the imaging device.

[0111] The image of the alignment mark of the mask acquired by the imaging device is formed on the optical path of the optical path length changing optical system.

[0112] The optical positional relationship between the images of the alignment mark of the workpiece and the alignment mark of the mask with respect to the imaging device is equal.

[0113] According to this configuration, when alignment is performed using a plurality of alignment units, even in a small exposure area, the alignment units do not interfere with each other, and high-precision alignment can be performed.

[0114] (2) The projection exposure apparatus according to (1), wherein the synthetic optical element is a first dichroic prism having a pair of prisms, wherein the bonding surfaces of the pair of prisms, which are inclined at 45° with respect to the optical axis of the first alignment light emitted from the projection lens, constitute a half-mirror surface,

[0115] In the prism facing the workpiece, a surface perpendicular to the optical axis of the first aiming light constitutes a dichroic surface that reflects the first aiming light and transmits the second aiming light.

[0116] According to this configuration, it is possible to prevent the first alignment light having substantially the same wavelength as the exposure light from being irradiated onto the workpiece, and to combine the first alignment light and the second alignment light into combined light.

[0117] (3) The projection exposure apparatus according to (1) or (2), wherein the optical path length changing optical system comprises:

[0118] a second dichroic prism, the second dichroic prism being composed of a plurality of prisms, wherein two joint surfaces of the plurality of prisms are orthogonal to each other, the two joint surfaces being inclined at 45 degrees relative to the optical axis of the synthesized light emitted from the synthesizing optical element and constituting dichroic surfaces that reflect the first alignment light and transmit the second alignment light; and

[0119] A pair of reflecting optical elements, each of which is arranged at a position away from the optical axis of the synthetic light emitted from the synthetic optical element, and whose reflecting surfaces are orthogonal to each other so that the first alignment light reflected by one of the joint surfaces of the second dichroic prism is incident on the other joint surface of the second dichroic prism.

[0120] According to this configuration, the first aiming light can be separated from the combined light emitted from the combining optical element, and the optical path length of the first aiming light can be changed.

[0121] (4) The projection exposure apparatus according to (3), wherein the alignment unit is provided so as to be horizontally movable so as to be able to advance and retreat between the projection lens and the workpiece.

[0122] The workpiece mark illumination light source and the pair of reflecting optical elements are arranged on a horizontal plane including an optical axis of the synthesized light emitted from the synthesizing optical element.

[0123] According to this configuration, the height dimension of the alignment unit can be suppressed, thereby enabling the alignment unit to move in the space between the projection lens and the workpiece without interfering with the projection lens and the workpiece. Furthermore, the alignment unit can be retracted during exposure transfer.

[0124] (5) A projection exposure method comprising the projection exposure apparatus according to any one of (1) to (4), the projection exposure method comprising:

[0125] a step of aligning the mask and the workpiece based on the image of the alignment mark of the mask and the alignment mark of the workpiece acquired by the imaging device; and

[0126] A process of irradiating a mask with exposure light, projecting a pattern formed on the mask onto a workpiece using a projection lens, and exposing the workpiece to the pattern.

[0127] According to this structure, when multiple alignment units are used for alignment, even in a small-sized exposure area, the alignment units do not interfere with each other, and high-precision alignment can be performed, enabling exposure at high resolution with an increased number of divided exposure areas.

[0128] In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2020-153975) filed on September 14, 2020, the contents of which are incorporated herein by reference.

Claims

1. A projection exposure apparatus, characterized in that: The projection exposure device irradiates exposure light onto a mask, projects a pattern formed on the mask onto a workpiece using a projection lens, and exposes the pattern to the workpiece. The projection exposure device comprises: a mask mark illumination light source capable of irradiating the alignment mark of the mask with the exposure light itself or light having substantially the same wavelength as the exposure light, that is, first alignment light; a workpiece mark illumination light source capable of irradiating a second alignment light having a different wavelength from the exposure light toward the alignment mark of the workpiece; as well as an alignment unit including: an imaging device configured to capture images of the alignment mark of the workpiece and the alignment mark of the mask based on the first alignment light; and an imaging optical system having a synthesis optical element for emitting synthesized light obtained by synthesizing the first alignment light emitted from the mask mark illumination light source and passing through the mask and the projection lens and the light from the alignment mark of the workpiece toward the imaging device, the imaging optical system being configured to enable the imaging device to acquire an image of the alignment mark of the mask and the alignment mark of the workpiece as an image, The imaging optical system includes an optical path length changing optical system that branches and converges the first alignment light from the first alignment light synthesized by the synthesizing optical element and the light from the alignment mark of the workpiece so that the optical path length of the first alignment light from the synthesizing optical element to the imaging device is longer than the optical path length of the light from the alignment mark of the workpiece from the synthesizing optical element to the imaging device. The image of the alignment mark of the mask acquired by the imaging device is formed on the optical path of the optical path length changing optical system. The optical positional relationship between the images of the alignment mark of the workpiece and the alignment mark of the mask with respect to the imaging device is equal.

2. The projection exposure apparatus according to claim 1, wherein The synthetic optical element is a first dichroic prism having a pair of prisms, wherein the bonding surfaces of the pair of prisms, which are tilted 45 degrees with respect to the optical axis of the first collimating light emitted from the projection lens, constitute a half-transmitting and half-reflecting mirror surface. In the prism facing the workpiece, a surface perpendicular to the optical axis of the first aiming light constitutes a dichroic surface that reflects the first aiming light and transmits the second aiming light.

3. The projection exposure apparatus according to claim 1 or 2, characterized in that The optical path length changing optical system comprises: a second dichroic prism, the second dichroic prism being composed of a plurality of prisms, wherein two joint surfaces of the plurality of prisms are orthogonal to each other, the two joint surfaces being inclined at 45 degrees relative to the optical axis of the synthesized light emitted from the synthesizing optical element and constituting dichroic surfaces that reflect the first alignment light and transmit the second alignment light; and A pair of reflecting optical elements, each of which is arranged at a position away from the optical axis of the synthetic light emitted from the synthetic optical element, and the reflecting surfaces of the pair of reflecting optical elements are orthogonal to each other so that the first alignment light reflected by one of the joint surfaces of the second dichroic prism is incident on the other joint surface of the second dichroic prism.

4. The projection exposure apparatus according to claim 3, wherein The alignment unit is arranged to be movable horizontally so as to be able to move forward and backward between the projection lens and the workpiece. The workpiece mark illumination light source and the pair of reflecting optical elements are arranged on a horizontal plane including an optical axis of the synthesized light emitted from the synthesizing optical element.

5. A projection exposure method, characterized in that: A projection exposure method comprising the projection exposure apparatus according to any one of claims 1 to 4, The projection exposure method comprises: a step of aligning the mask and the workpiece based on the image of the alignment mark of the mask and the alignment mark of the workpiece acquired by the imaging device; as well as A process of irradiating a mask with exposure light, projecting a pattern formed on the mask onto a workpiece using a projection lens, and exposing the workpiece to the pattern.

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