JP2010278353A - Aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner capable of carrying out exposure at high accuracy, by carrying out a relative alignment between a projection position of an exposure pattern of a projection optical system and a detection position of a position detection optical system, without having to move the position detection optical system on a rear surface side. <P>SOLUTION: The aligner 1 includes a stage 9 for mounting a substrate 7 thereon; the projection optical system 4 disposed at a surface side of the substrate 7 and projecting a pattern on a surface 7a of the substrate 7; a rear surface position detection optical system 6 disposed at the rear surface side of the substrate 7 and detecting an alignment mark formed on a rear surface 7b of the substrate 7; a window member 10 attached to a through-hole 9b penetrating the stage 9 and formed of an optical transmitting member; and a control section 11 detecting the pattern image formed on a surface 10a of the window member 10 by the projection optical system 4 from the rear surface side of the window member 10, by means of the rear surface position detection optical system 6, and calculating a relative relationship between a position of the pattern image formed by the projection optical system 4 and the position of the aligning mark detected by the rear surface position detecting optical system 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exposure apparatus.

  Conventionally, when an electric circuit element is manufactured by applying a photoresist on a substrate and performing exposure, development, and etching processes, some electric circuit elements such as a thyristor have a structure on both sides of the substrate. It was necessary to create an element by performing the above steps. In order to perform processing on both surfaces with high accuracy, an exposure apparatus has been proposed that performs alignment by detecting an alignment mark provided on the back surface of the substrate (see, for example, Patent Document 1). In addition, recently, MEMS (Micro Electro Mechanical Systems) elements and the like have been created using a semiconductor process, and thus the demand for processing from such a back surface is increasing. In this case, more precise processing technology is required, but it is necessary to determine the relative relationship between the position where the projection optical system projects the pattern and the position where the position detection optical system detects the alignment mark. Has been proposed (see, for example, Patent Document 2). The invention described in Patent Document 2 is an exposure method using a reticle (or photomask). For alignment of the substrate before exposure, the projection is first performed with the substrate retracted from the projection optical system. A reticle alignment mark provided on the reticle is projected by an optical system, and the projection position is detected by a position detection optical system on the back side. At this time, the lens of the position detection optical system is moved to remove the influence of the thickness of the substrate.

JP-A-62-254423 Japanese Patent Publication No. 6-50714

  However, the optical axis may be shifted by moving the lens of the position detection optical system, or the movement direction may not completely coincide with the optical axis of the projection optical system. There has been a problem that a shift occurs in the position to be detected.

  The present invention has been made in view of such problems, and the position detection optical system detects the position on the front surface side where the projection optical system projects the exposure pattern without moving the position detection optical system on the back surface side. An object of the present invention is to provide an exposure apparatus that can determine the relative relationship with the position on the back surface side with high accuracy.

  In order to solve the above-described problems, an exposure apparatus according to the present invention includes a stage having a holder for placing a substrate, a projection optical system that is disposed on the surface side of the substrate and projects a pattern onto the surface of the substrate, A rear surface position detection optical system for detecting an alignment mark formed on the rear surface side of the substrate, a window member formed of a member that is attached to a through-hole penetrating the holder and transmits light, and projection The pattern image formed on the front surface of the window member by the optical system is detected from the back surface side of the window member by the back surface position detection optical system, and the position of the pattern image formed by the projection optical system and the back surface position detection optical system And a control unit that calculates a relative relationship with the position of the alignment mark to be detected.

  In such an exposure apparatus, the window member is such that the surface of the window member is substantially flush with the surface of the substrate placed on the holder, and the surface of the window member is projected from the projection optical system. It is preferable that the image of the pattern formed on has a thickness that substantially matches the focal plane of the back surface position detection optical system.

の条件を満足するよう構成されることが好ましい。 At this time, the window member has a refractive index for light from the projection optical system of the medium of the window member as n _EXP , a thickness of the window member as t _w , a thickness of the substrate as t _s , and the projection optical system. When the difference between the focus position and the focus position of the back surface position detection optical system is Δ _EXP and the depth of focus of the back surface position detection optical system is DOF, the following equation

It is preferable to be configured to satisfy the above condition.

  Further, such an exposure apparatus has a calibration plate having a surface in contact with the surface of the holder and the surface of the window member when placed on the holder, and a calibration mark is formed on each of the surfaces. And the control unit detects each position of the calibration mark with the back surface position detection optical system in a state where the calibration plate is placed on the holder, and controls the pattern formed by the projection optical system. It is preferable to calculate an offset of the relative relationship between the position of the image and the position of the alignment mark detected by the back surface position detection optical system.

  When the exposure apparatus according to the present invention is configured as described above, the position where the projection optical system projects the image of the exposure pattern without moving the position detection optical system on the back side of the substrate and the alignment by the position detection optical system The relative relationship with the detection position of the mark can be calculated, and the alignment can be performed more accurately, and the exposure by the exposure apparatus can be performed with high accuracy.

It is the schematic which shows the structure of the exposure apparatus which concerns on this invention. FIG. 4 is an explanatory diagram showing the relationship between a substrate, a through hole, and a window member in order to explain the alignment between the projection position and the detection position. FIG. The optical system is in a focused state, and (b) shows the relationship between the focus position of the projection optical system and the focus position of the back surface position detection optical system in the window member. It is explanatory drawing for demonstrating generation | occurrence | production of position shift when the window member whose front surface and back surface are not parallel is attached. It is explanatory drawing for demonstrating generation | occurrence | production of position shift when a window member is inclined and attached. It is explanatory drawing for demonstrating the procedure which correct | amends a position shift using the calibration label | marker.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the configuration of the exposure apparatus 1 according to the present embodiment will be described with reference to FIG. The exposure apparatus 1 of the present embodiment is a maskless exposure apparatus that projects an image (exposure pattern) from a DMD element onto a substrate 7, and as shown in FIG. 1, an illumination optical system 2 that irradiates illumination light, and The DMD element 3 as a light modulation unit that spatially modulates the illumination light from the illumination optical system 2 to generate a plurality of images (exposure patterns), and the exposure pattern from the DMD element 3 is projected onto the substrate 7. A projection optical system 4 that is incorporated in the projection optical system 4, an autofocus detection optical system 5 that adjusts the image of the exposure pattern from the DMD element 3 to focus on the surface of the substrate 7, and the substrate 7. Detection from a back surface position detection optical system 6 for detecting the position of the back surface side, a stage 9 provided with a holder 8 for mounting the substrate 7, and detection from the autofocus detection optical system 5 and the back surface position detection optical system 6. DMD depending on the result It is configured to include a control unit 11 for controlling the operation of the child 3 and stage 9, a.

  The DMD element 3 includes a plurality of micromirrors (not shown) that can change the reflection angle. Each micromirror of the DMD element 3 is driven by the control unit 11, and by changing the reflection angle of the reflection surface, it is possible to arbitrarily select whether the reflected light is guided to the projection optical system 4 or not, Various shapes of exposure patterns can be generated.

  The illumination optical system 2 condenses the illumination light from the exposure light source 21 that emits a wavelength for exposing the photoresist coated on the substrate 7 made of a mercury lamp, LED, etc., and irradiates the DMD element 3 with the illumination light from the exposure light source 21. And a condenser lens 22 to be used. The projection optical system 4 also includes a second objective lens 41 that converts an exposure pattern (exposure light) generated by the DMD element 3 into substantially parallel light, and an objective lens 42 that projects the substantially parallel light onto the substrate 7. It consists of and.

  The autofocus detection optical system 5 emits a point light source 51 that emits focus detection light having a wavelength that does not expose the photoresist coated on the substrate 7 (hereinafter, referred to as “focus detection light”), and the point light source 51. A collimator lens 52 for converting the focus detection light from the light into a substantially parallel light, a light-shielding diaphragm 53 for blocking half of the pupil of the focus detection light transmitted through the collimator lens 52, and the substantially parallel focus detection light transmitted. A half mirror 54 that further reflects the reflected light reflected by the substrate 7, and a dichroic mirror 55 that is disposed on the optical path of the projection optical system 4, reflects the focus detection light and the reflected light, and transmits the exposure light; An imaging lens 56 for imaging the reflected light reflected by the dichroic mirror 55 and the half mirror 54, and a linear sensor for receiving the image. And a 57.

  The holder 8 on which the substrate 7 is placed is formed with a through hole 8a and a through hole 8b penetrating in the vertical direction (direction substantially parallel to the optical axes of the projection optical system 4 and the back surface position detection optical system 6). The through hole 8 a is an opening for observing the alignment mark formed on the back surface of the substrate 7. For example, three or more alignment marks such as cross marks are formed on the back surface of the substrate 7, and these alignment marks are passed through a plurality of through holes 8 a formed corresponding to each alignment mark. Then, the back surface position detection optical system 6 detects. A light-transmissive window member 10 is attached to the through hole 8b. As will be described later, the window member 10 is provided for relative alignment between the projection position of the exposure pattern by the projection optical system 4 and the detection position of the alignment mark by the back surface position detection optical system 6. Yes. The through hole 8b (window member 10) is formed at a position where the substrate 7 placed on the holder 8 does not block the through hole 8b. Further, the stage 9 can be moved in the horizontal direction and the vertical direction by an appropriate moving means (not shown) controlled by the control unit 11. An interferometer or a linear encoder is attached to the stage 9, and the position of the holder 8 is monitored by the control unit 11.

  The back surface position detection optical system 6 is disposed on the side facing the projection optical system 4 with the holder 8 interposed therebetween, that is, below the holder 8. The back surface position detection optical system 6 includes a position detection light source 61 that emits position detection light (hereinafter referred to as “position detection light”), and a condenser that collects the position detection light from the position detection light source 61. The lens 62, the half mirror 63 that reflects the position detection light collected by the condenser lens 62 toward the substrate 7, and the position detection light reflected by the half mirror 63 is condensed to illuminate the back surface of the substrate 7. An objective lens 64, an imaging lens 65 that forms an image of reflected light that is reflected from the back surface of the substrate 7, reflected by the objective lens 64, and transmitted through the half mirror 63, and an image sensor 66 that detects this image. It is configured.

  In the exposure apparatus 1 configured as described above, illumination light (exposure light) emitted from the exposure light source 21 of the illumination optical system 2 is applied to the DMD element 3 via the condenser lens 22. At this time, the control unit 11 controls the reflection angles of all the micromirrors corresponding to the pixels of the DMD element 3 in accordance with the signal of the pattern generator built in the control unit 11. With this control, each micromirror of the DMD element 3 can select whether or not to guide the illumination light to the projection optical system 4, and a desired exposure pattern can be generated. The exposure pattern generated by the DMD element 3 is projected onto the substrate 7 by the projection optical system 4. At this time, on the basis of the focus signal from the autofocus detection optical system 5 incorporated in the projection optical system 4, the stage 9 is moved up and down by the control of the control unit 11, and the exposure pattern from the DMD element 3 becomes the surface of the substrate 7. Projected to focus on. Then, exposure of the substrate 7 is performed by projection of the exposure pattern.

  Here, the operation of the autofocus detection optical system 5 will be described. First, focus detection light emitted from the point light source 51 is converted into substantially parallel light by the collimator lens 52. As described above, the substantially parallel focus detection light is narrowed down by blocking about half of the pupil by the light-shielding diaphragm 53, then passes through the half mirror 54, and enters the dichroic mirror 55. The dichroic mirror 55 Is reflected in the direction of the substrate 7 and irradiated onto the substrate 7 through the objective lens 42 of the projection optical system 4. Then, the reflected light reflected by the substrate 7 is condensed again by the objective lens 42 of the projection optical system 4, reflected by the dichroic mirror 55, and guided to the autofocus detection optical system 5. The reflected light is further reflected by the half mirror 54 and imaged on the linear sensor 57 by the imaging lens 56. Thus, the autofocus detection optical system 5 is a so-called pupil half-hidden focus detection optical system. Then, based on the image obtained by the linear sensor 57, a deviation of the height of the substrate 7 from the in-focus position of the projection optical system 4 is detected. Based on the signal, the control unit 11 moves the stage 9 in the optical axis direction. By moving in the (vertical direction), the exposure pattern from the DMD element 3 is focused on the surface of the substrate 7.

  On the other hand, in the back surface position detection optical system 6, the position detection light emitted from the position detection light source 61 is converted into substantially parallel light by the condenser lens 62, enters the half mirror 63, and is reflected by the half mirror 63. The light is condensed by the objective lens 64, and the back surface of the substrate 7 is illuminated through the through hole 8 a provided in the holder 8. As described above, three or more alignment marks are formed on the back surface of the substrate 7. The position detection light reflected by the back surface of the substrate 7 is condensed again by the objective lens 64 to become substantially parallel light, passes through the half mirror 63, and then forms an image on the image sensor 66 by the imaging lens 65. In this image sensor 66, the back image of the substrate 7 is photoelectrically converted, and the alignment mark is recognized by image processing.

  In the back surface position detection optical system 6, a reference point serving as a reference for alignment is stored in advance by the control unit 11. The reference point is a coordinate on the image sensor 66 when the back surface position detection optical system 6 detects the pattern center projected on the window member 10 by the projection optical system 4 described later. The stage 9 is moved under the control of the control unit 11 so that this reference point and the centers of the three or more alignment marks recognized by the image sensor 66 are sequentially matched. And the control part 11 calculates the position in the horizontal surface on the coordinate in the stage 9 of the board | substrate 7, and the rotation amount in a horizontal surface by reading the coordinate of the stage 9 in that case. Based on the position and rotation amount of the substrate 7 calculated in this way, the stage 9 is moved to move the substrate 7 to a predetermined exposure position, and exposure processing is performed. The processing by the back surface position detection optical system 6 is executed, for example, before the substrate 7 is set on the holder 8 and exposure processing is performed.

  By the way, even when the substrate 7 is arranged at an accurate exposure position as described above, the relative position between the projection position of the exposure pattern by the projection optical system 4 and the detection position of the alignment mark by the back surface position detection optical system 6. If the relationship is misaligned, high-precision machining cannot be performed. In order to enable this highly accurate processing, it is necessary to accurately grasp the relative positional relationship between the projection position of the projection optical system 4 and the reference point of the back surface position detection optical system 6, and to correct any deviation. is there. For this reason, in the exposure apparatus 1 of the present embodiment, the above-described window member 10 is used to perform measurement processing of the center position (run-in position) of the alignment mark between the projection optical system 4 and the back surface position detection optical system 6. For example, this processing may be performed once as an initial processing before processing, or may be performed a plurality of times at predetermined time intervals.

First, the positional relationship between the projection position of the projection optical system 4 and the detection position of the back surface position detection optical system 6 will be described with reference to FIG. When projecting an exposure pattern on the substrate 7, as shown in FIG. 2A, the autofocus detection optical system 5 so that the exposure light L _EXP from the DMD element 3 is focused on the surface 7a of the substrate 7. Based on the detection result by the (autofocus mechanism), the control unit 11 is adjusted by moving the stage 9 up and down. At that time, the back surface position detection optical system 6 is configured to be able to focus and observe the back surface 7b of the substrate 7, that is, the contact surface between the holder 8 and the substrate 7 through the through hole 8a. . That is, the projection optical system 4 and the back surface position detection optical system 6 are both in focus on the front surface 7a and the back surface 7b of the substrate 7, respectively.

In FIG. 2B, the stage 9 is moved in the horizontal direction, and on the window member 10, the projection optical system 4 projects the exposure pattern, and the back surface position detection optical system 6 detects the exposure pattern. The state of taking the correspondence is shown. At this time, the DMD element 3 displays an exposure pattern such as a cross pattern, for example, so as to serve as an index of the position where the exposure pattern is projected. Then, the cross pattern from the DMD element 3 is adjusted by the autofocus mechanism so as to be focused on the upper surface 10 a of the window member 10. Further, since the window member 10 is light transmissive, the exposure light L _EXP including the exposure pattern is refracted and transmitted through the window member 10 as shown in FIG. The window member 10 is a parallel plate, and when the thickness is t _w and the refractive index of the exposure light L _EXP at the window member 10 is n _EXP , the image lifting amount u is expressed by the following equation (1). Is represented by

Further, when the holder 8 has a hole, the position detection light of the back surface position detection optical system 6 leaks from the hole and is irradiated to the apparatus main body, and as a result, the substrate 7 is irradiated with unexpected stray light. is there. In order to prevent the resist on the substrate 7 from being exposed even when such stray light is irradiated, the back surface position detection optical system 6 generally uses light having a wavelength different from that of the exposure light as the position detection light. However, the focus position shifts due to chromatic aberration between the exposure light and the position detection light due to the difference in wavelength. In the example of FIG. 2B, the case where the focus position of the exposure light L _EXP is lower than the focus position of the back surface position detection optical system 6 by Δ _EXP is shown. In other words, if the sum of the thickness t _{s of the} substrate 7 and the amount of deviation Δ _EXP of the focus position of the exposure light L _EXP and the image floating amount u expressed by the above equation (1) match within the depth of focus. The back surface position detection optical system 6 can detect the position where the projection optical system 4 projects the exposure pattern in a focused state without moving the back surface position detection optical system 6 up and down. This relationship is expressed by the following equation (2), where DOF is the depth of focus of the back surface position detection optical system 6 in the window member 10.

Constituting the window member 10 so as to satisfy the relationship of formula (2), i.e., by the thickness t _w which satisfies the conditional expression (2), the exposure pattern is projected by the projection optical system 4 By detecting the position (the center of the pattern) by the back surface position detection optical system 6 and detecting it as coordinates on the image sensor 66, the relative positional relationship between the projection optical system 4 and the back surface position detection optical system 6 is It can be calculated accurately. The coordinates of the pattern center on the image sensor 66 are the aforementioned reference points. For this reason, the substrate 7 can be placed at the exposure position by alignment using the back surface position detection optical system 6, and the projection optical system 4 can expose the substrate 7 with high accuracy. When quartz (n _exp = 1.46674) is used for the window member 10, the depth of focus DOF is about 2.4 μm when the aperture of the back surface position detection optical system 6 is 0.3 and the exposure light wavelength is 435 nm. When the deviation of the focusing position of the back surface position detection optical system 6 is 10 μm and the thickness of the substrate 7 is 0.7 mm, 2.224 mm <t _w <2.238 mm is the optimum value of the thickness of the window member 10.

  By the way, in the above description, although the case where the window member 10 was a parallel plate was demonstrated, in the actually used window member 10, when the parallel of the surface and a back surface is not perfect, or attachment is incomplete and the surface The back surface may not be perpendicular to the optical axes of the projection optical system 4 and the back surface position detection optical system 6. The alignment process in such a case will be described below with reference to FIGS.

First, as shown in FIG. 3, when the front surface 10a and the back surface 10b of the window member 10 are not completely parallel, for example, when the back surface 10b is inclined by an angle ε with respect to the optical axis, The position of 10a is observed by shifting (lateral deviation) approximately by _Eε calculated by the following equation (3).

In addition, as shown in FIG. 4, when the window member 10 is not completely installed and the front surface 10a and the back surface 10b are inclined with respect to the optical axis by an angle δ, the position of the front surface 10a of the window member 10 is determined. Is observed with a shift (lateral shift) of E _δ approximately calculated by the following equation (4).

Such a lateral shift of the position of the surface 9a is caused by the fact that the main body of the window member 10 and the mounting thereof are not complete, and therefore it is hardly considered that it changes in the apparatus. Therefore, it may be corrected as an offset when performing relative alignment between the projection position and the detection position. For this purpose, a calibration label 12 as shown in FIG. 5 can be used. The calibration label 12 is used by being placed on the holder 8, and the contact surface to the holder 8 is cut off on the window member 10 side by the projection height of the window member 10, thereby providing a step. ing. Further, the calibration marks 12 are formed with calibration marks 12 a and 12 b for observing the back surface 7 b of the substrate 7 when the calibration marks 12 are placed on the holder 8. The calibration mark 12a can be observed from the through hole 8a, and the calibration mark 12b can be observed from the window member 10. Incidentally, a step provided on the calibration target plate 12, i.e., the calibration mark 12a, step between 12b is such that the window member 10 in the thickness t _w is approximately equal to ω amount lifting the lifted from the surface of the holder 8 Is formed. The relative position in the horizontal direction between the calibration marks 12a and 12b is strictly measured with an interferometer or the like.

  The calibration label 12 having the above-described configuration is placed on the holder 8, the mark position of the calibration mark 12a is observed through the through-hole 8a by the back surface position detection optical system 6, and the stage 9 is moved appropriately. The mark position of the calibration mark 12a is aligned with the screen center (reference point) of the image sensor 66, and the coordinates indicated by the stage 9 in this state are stored. Next, the mark position of the calibration mark 12 b is observed by the back surface position detection optical system 6 through the window member 10, and the stage 9 is appropriately moved so that the mark position of the calibration mark 12 b is aligned with the screen center of the image sensor 66. The coordinates indicated by the stage 9 in this state are stored.

  The difference between the coordinates indicated by the stage 9 in the state where the calibration mark 12a is aligned with the image center and the coordinates indicated by the stage 9 when the calibration mark 12b is aligned with the image center is obtained as described above. Compared with the relative position between the calibration marks 12a and 12b measured strictly in advance, the difference is obtained. By using this difference as an offset at the time of alignment and correcting when moving the stage 9 at the time of exposure, alignment can be performed accurately.

  As described above, according to the exposure apparatus 1 of the present embodiment, the position where the projection optical system 4 projects the exposure pattern and the back surface position detection optics without moving a part or the whole of the back surface position detection optical system 6. Since the system 6 can match the position where the projected exposure pattern is detected, stable alignment is possible.

  In the above description, the example in which the alignment mechanism of the projection optical system 4 and the back surface position detection optical system 6 is applied to the so-called maskless exposure apparatus 1 using the DMD element 3 has been described. However, a reticle is used. It can also be applied to an exposure apparatus. In this case, by detecting the reticle alignment mark with the back surface position detection optical system 6, the coordinates of the position where the exposure pattern is projected can be read as the coordinates of the stage 9, and the same procedure as the above-described alignment process is performed. The exposure process can be performed by positioning the projection position and the detection position based on the alignment mark formed on the back surface 7b of the substrate 7. Furthermore, this alignment mechanism can be applied to position adjustment (alignment) in three-dimensional mounting.

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 4 Projection optical system 6 Back surface position detection optical system 7 Substrate 7a Front surface 7b Back surface 8 Holder 8a, 8b Through-hole 9 Stage 10 Window member 11 Control part 12 Calibration standard plate

Claims (4)

A stage having a holder for placing a substrate;
A projection optical system disposed on the surface side of the substrate and projecting a pattern onto the surface of the substrate;
A back surface position detection optical system that is disposed on the back surface side of the substrate and detects an alignment mark formed on the back surface of the substrate;
A window member formed of a member that is attached to a through-hole penetrating the holder and transmits light;
The image of the pattern formed on the surface of the window member by the projection optical system is detected by the back surface position detection optical system from the back surface side of the window member, and the image of the pattern formed by the projection optical system is detected. An exposure apparatus comprising: a controller that calculates a relative relationship between the position and the position of the alignment mark detected by the back surface position detection optical system.   The window member has the surface of the window member positioned substantially on the same plane as the surface of the substrate placed on the holder, and the surface of the window member from the projection optical system. The exposure apparatus according to claim 1, wherein an image of the pattern formed on the substrate has a thickness that substantially matches a focal plane of the back surface position detection optical system. The window member is
The refractive index for the light from the projection optical system of a medium of the window member and n _EXP, the thickness of the window member and t _w, the thickness of the substrate and t _s, the focal position of the projection optical system When the difference between the in-focus position of the back surface position detection optical system is Δ _EXP and the depth of focus of the back surface position detection optical system is DOF,

The exposure apparatus according to claim 2, wherein the exposure apparatus is configured to satisfy the following condition. When mounted on the holder, it has a surface that contacts the surface of the holder and the surface of the window member, and has a calibration label in which a calibration mark is formed on each of the surfaces,
The control unit is formed by the projection optical system by detecting each position of the calibration mark by the back surface position detection optical system in a state where the calibration plate is placed on the holder. The exposure apparatus according to claim 1, wherein an offset of a relative relationship between the position of the pattern image and the position of the alignment mark detected by the back surface position detection optical system is calculated.

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