JP2010109220A - Maskless exposure device and maskless exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a maskless exposure apparatus and a maskless exposure method used for manufacturing a MEMS, a semiconductor and the like, and to accurately project a projection pattern even when the projection magnification is variable according to the size of the projection pattern. The purpose is to form.
A projection optical system that includes a stage that supports a substrate, a spatial light modulation unit that generates a desired projection pattern to be projected on the substrate by inputting an external signal, and an objective lens that projects the projection pattern onto the substrate. And an observation optical system that detects an alignment mark formed on the substrate via the objective lens, wherein the projection optical system is capable of changing a projection magnification. And a mechanism for aligning the alignment mark with a preset index or a predetermined center position of the projection pattern each time the projection magnification is changed.
[Selection] Figure 1

Description

  The present invention relates to a maskless exposure apparatus and a maskless exposure method used for manufacturing MEMS (Micro Electro Mechanical Systems), semiconductors, and the like.

Recently, a maskless exposure apparatus has been developed in which an exposure pattern is generated using a DMD (Digital Micromirror Device), and the exposure pattern is reduced and projected to expose a substrate.
In the conventional maskless exposure apparatus, although the exposure area exposed at one time is very small, the exposure area is simply divided into a plurality of pieces and the screen is exposed while moving the stage. There has been a problem that much time is required for the work, but this problem has been solved by adjusting the objective lens to change the projection magnification of the pattern.
JP 2000-40660 A JP 2006-310446 A JP 2007-25394 A

  However, the alignment of the exposure pattern is a process of moving the stage placed on the exposure object, reading the alignment mark formed on the exposure object with a camera, and correcting the position based on the read position data. Only.

  The present invention has been made in view of such circumstances, and a maskless exposure apparatus and a maskless exposure method capable of forming a projection pattern with high accuracy even when the projection magnification is variable in accordance with the size of the projection pattern. The purpose is to provide.

  The maskless exposure apparatus of the present invention includes a stage that supports a substrate, a spatial light modulator that generates a desired projection pattern to be projected on the substrate by inputting an external signal, and an objective lens. The projection pattern is applied to the substrate. A maskless exposure apparatus having a projection optical system for projecting and an observation optical system for detecting an alignment mark formed on the substrate via the objective lens, wherein the projection optical system can change a projection magnification And a mechanism for aligning the alignment mark with a preset index or a predetermined center position of the projection pattern each time the projection magnification is changed. Features.

  The maskless exposure method of the present invention is a maskless exposure method in which a desired projection pattern generated by inputting an external signal is projected onto a substrate through a projection optical system including an objective lens to expose the substrate. A first objective lens having a first projection magnification is set, and a first observation optical system including the first objective lens is used to observe an alignment mark formed on the substrate and set in advance. And a second step of projecting and exposing the projection pattern onto the substrate via the first objective lens, and a first step of aligning with respect to the index or the center position of the projection pattern specified in advance. , Setting a second objective lens having a second projection magnification different from the first projection magnification, and using the second observation optical system including the second objective lens, A third step of aligning with respect to the index or the center position of the projection pattern, and a fourth step of projecting and exposing the projection pattern onto the substrate via the second objective lens. It is characterized by having.

  In the present invention, the exposure work time can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a first embodiment of the maskless exposure apparatus of the present invention.

  This maskless exposure apparatus has an exposure optical system 11, a stage 13, and an observation optical system 15.

  The exposure optical system 11 includes a projection illumination optical system 17, a DMD element 19, and a projection optical system 20. The projection optical system 20 includes a first projection lens group 21, a dichroic mirror 23, and a second projection lens group 25.

  The projection illumination optical system 17 has an exposure light source 27 and a condenser lens 29. As the exposure light source 27, an LD, an LED, a mercury lamp, or the like is used. More specifically, exposure light such as i-line (365 nm) and g-line (436 nm) is used. The condenser lens 29 condenses the exposure light from the exposure light source 27 and irradiates the DMD element 19 with parallel light. The DMD element (Digital Micromirror Device) 19 has a number of micromirrors whose reflection angles can be changed. By changing the reflection angle by driving the micromirror by the DMD element driving circuit 31, it is possible to generate exposure patterns of various shapes.

  The exposure light having the exposure pattern reflected by the DMD element 19 passes through the first projection lens group 21 and is reflected by the dichroic mirror 23. The reflected exposure light is irradiated onto the substrate W through the second projection lens group 25 which is an objective lens group, and the resist applied to the substrate W is exposed. Each of the first projection lens group 21 and the second projection lens group 25 has an infinite system design in which aberrations are corrected, and the light flux that has exited from one point on the DMD element 19 and passed through the first projection lens group 21. Is a parallel light flux. Then, the light passes through the second projection lens group 25 and is condensed at one point on the focal plane. The second projection lens group 25 is supported by a revolver (not shown), and can be replaced with a plurality of second projection lens groups 25A having different magnifications by rotating the revolver.

  The stage 13 is movable in the horizontal direction and the vertical direction. The stage 13 is driven by a stage controller 33. The substrate W can be adsorbed on the stage 13. A fluorescent member 35 for detecting the position of the exposure pattern of the DMD element 19 is fixed on the stage 13.

  The observation optical system 15 includes an observation illumination optical system 37, a half mirror 39, a dichroic mirror 23, a second projection lens group 25, an imaging lens 41, an image sensor 43, and a monitor 45. The dichroic mirror 23 and the second projection lens group 25 are shared by the exposure optical system 11 and the observation optical system 15.

  The observation illumination optical system 37 has a light source 47 and a collector lens 49. A white light source is used as the light source 47. More specifically, for example, white light having a wavelength of 500 nm or more that does not expose the resist on the substrate W is used. Light from the light source 47 passes through the collector lens 49 and is reflected by the half mirror 39. The reflected light passes through the dichroic mirror 23 and passes through the second projection lens group 25 to illuminate the substrate W. The illumination light reflected by the substrate W is guided to the image sensor 43 through the second projection lens group 25, the dichroic mirror 23, the half mirror 39, and the imaging lens 41. The image sensor 43 photoelectrically converts the obtained image and outputs it to the monitor 45. The acquired enlarged image of the substrate W is displayed on the screen of the monitor 45. In this embodiment, a case where the visual field projected by the DMD element 19 and the visual field of the image sensor 43 are the same will be described in order to simplify the description. However, it is not particularly necessary to match.

  FIG. 2 shows details of the plurality of second projection lens groups 25 and 25A described above. In FIG. 2, the focal length of the first projection lens group 21 is 300 mm.

  FIG. 2A shows the focal length of the second projection lens group that can be changed by the revolver. A second projection lens group having a focal length of 20 mm, 10 mm, 5 mm, and 2 mm can be selected. FIG. 2B shows the projection magnification at that time. FIG. 2C shows the size of the projected area when the size of the DMD element 19 is 16 mm × 12 mm. FIG. 2D shows the size of one pixel of the DMD element 19, that is, the size of the pixel when the size of the micromirror of the DMD element 19 is 10 μm □. FIG. 2E shows the numerical aperture of the second projection lens group. FIG. 2 (f) shows the optical resolution. When the numerical aperture of the second projection lens group is the same as that of the first projection lens group 21, the optical resolution is approximately 4 pixels. The line is formed with a plurality of pixels with a pixel size smaller than the optical resolution, and the electrical wiring breaks even if there is a defective pixel in the DMD element 19 under the assumption that the defective pixel does not occur side by side. Is preventing.

  FIG. 3 shows the substrate W exposed by the maskless exposure apparatus described above. A large number of exposure pattern regions P are formed on the substrate W. The exposure pattern area P is formed at a predetermined interval. An alignment mark A is formed between the exposure pattern areas P.

  FIG. 4 shows an embodiment of a method for exposing the substrate W by the maskless exposure apparatus described above.

  Step S1: An alignment mark A is formed on the substrate W. The alignment mark A is formed between the exposure pattern areas P. The alignment mark A is formed by forming a projection pattern having a shape corresponding to the alignment mark A using the DMD element 19, exposing the projection pattern on the substrate W, and then developing and etching. The alignment mark A is exposed to a predetermined position with high accuracy at predetermined intervals by moving the stage 13. By forming the alignment mark A first, it is possible to maintain the position of the exposure pattern region P with high accuracy even if the substrate W is displaced by a subsequent process. A projection pattern having a shape corresponding to the alignment mark A formed on the DMD element 19 is stored in the apparatus in advance.

  Step S2: The substrate W on which the alignment mark A is formed is placed on the stage 13.

  Step S3: The revolver is operated to arrange the second projection lens group 25 having the first magnification. When the second projection lens group 25 having the first magnification is already used, it is left as it is.

  Step S4: The center of the projection pattern when the second projection lens group 25 having the first magnification is used is matched with the center of the index M. The stage 13 is moved so that the fluorescent member 35 is positioned on the focal plane of the second projection lens group 25. Then, with the light source 47 of the observation illumination optical system 37 turned off, the light source 27 of the projection illumination optical system 17 is turned on. A cross pattern is formed in advance on the DMD element 19, and the cross pattern is projected onto the fluorescent member 35 via the first projection lens group 21, the dichroic mirror 23, and the second projection lens group 25. When a cross pattern is projected onto the fluorescent member 35, fluorescence is generated from the fluorescent member 35. This fluorescence is condensed by the second projection lens group 25, passes through the dichroic mirror 23 and the half mirror 39, is collected by the imaging lens 41, and forms an image on the image sensor 43. Then, it is displayed on the monitor 45.

  FIG. 5 shows a cross pattern displayed on the monitor 45. The center O of the cross pattern is the center position of the projection pattern. The monitor 45 is provided with four indexes M as shown in FIG. By moving the index M on the monitor 45 and positioning the center of the index M at the center of the cross pattern, the position of the index M is set to the center position of the projection pattern. The interval of the index M is set corresponding to the second projection lens group 25 having the first magnification. The focal length of the second projection lens group 25 having the first magnification is set to 20 mm, for example. The dotted line indicates the field of view F of the monitor 45.

  Step S5: The exposure pattern region P is exposed using the second projection lens group 25 having the first magnification.

  FIG. 7 shows details of the alignment mark A and the exposure pattern region P of the substrate W shown in FIG. The exposure pattern area P is provided at a position spaced apart from the alignment mark A by a predetermined distance. The exposure pattern area P is divided as exposure areas EX11 to EX33 on which the projection pattern of the DMD element 19 is projected. In the exposure pattern area P, exposure areas FX1 to FX3 smaller than the exposure areas EX11 to EX33 are present. In this step S5, only the exposure areas EX11 to EX33 are exposed using the second projection lens group 25 having the first magnification. The positions of the exposure areas EX11 to EX33 are stored as relative coordinates (X, Y) from the alignment mark A in the stage controller 33. The stage controller 33 designates and moves the stage 13 and sends a signal to the DMD driving circuit 31 to sequentially expose the corresponding exposure areas EX11 to EX33.

  Before the exposure to each exposure pattern area P, the position of the alignment mark A and the index M are aligned. This alignment is performed using the monitor 45. For example, as shown in FIG. 8, an image of the alignment mark A provided on the substrate W and an index M indicating the alignment target of the second projection lens group 25 having a focal length of 20 mm are superimposed on the monitor 45. It is displayed. The position of the index M is obtained in step S4, and is set to the center position of the projection pattern. The interval of the index M is set corresponding to the second projection lens group 25 having a focal length of 20 mm.

  The alignment mark A has a cross shape as shown in FIG. The alignment mark A has four line portions S that are orthogonal to each other. Each line part S is formed in the same shape. Each line portion S is formed with a step portion so that the line width becomes narrower toward the center. In FIG. 9, the numerals indicate the dimensions of each part in μm units. The widths 120, 60, 30, and 12 of the line portion S are formed corresponding to the second projection lens group having the focal lengths of 20 mm, 10 mm, 5 mm, and 2 mm shown in FIG.

  As shown in FIG. 8, the index M is composed of a pair of opposed right triangles, and the center of the alignment mark A is aligned on the axis of symmetry. When the alignment mark A and the center of the index M coincide with each other, the intersection of the crosshair end of the alignment mark A and the hypotenuse of the right triangle of the index M becomes the midpoint of the hypotenuse of the right triangle of the index M. . The dotted line indicates the field of view F of the monitor 45.

  As shown in FIG. 10, when the center of the alignment mark A is deviated from the center of the index M, the position where the end of the cross line of the alignment mark A and the hypotenuse of the right triangle of the index M intersects. It will shift. The operator moves the stage 13 so that the end of the cross line and the hypotenuse of the right triangle are as shown in FIG. 8, and aligns the center of the alignment mark A and the center of the index M. At this time, the smaller the inclination of the hypotenuse of the right triangle of the index M, the higher the sensitivity to the misalignment between the center of the alignment mark A and the index M. Since it deviates from the hypotenuse of the right-angled triangle of the index M, it is desirable to make the inclination about 1/8 to 1/2 of the line width of the portion used for alignment of the alignment mark A.

  Step S6: The revolver is operated to arrange the second projection lens group 25A having the second magnification.

  Step S7: The center of the projection pattern when the second projection lens group 25A having the second magnification is used is matched with the center of the index M. The stage 13 is moved so that the fluorescent member 35 is positioned on the focal plane of the second projection lens group 25A having the second magnification. Then, the cross pattern image due to the fluorescence generated from the fluorescent member 35 is displayed on the monitor 45 in the same manner as in step S4 described above. Then, similarly to step S4 described above, the index M is moved on the monitor 45, and the center of the index M is positioned at the center of the cross pattern, so that the position of the index M is set to the center position of the projection pattern. The interval of the index M is set corresponding to the second projection lens group 25A having the second magnification. The focal length of the second projection lens group 25A having the second magnification is, for example, 5 mm.

  Step S8: The exposure pattern region P is exposed using the second projection lens group 25A having the second magnification. In this step, only the exposure areas FX1 to FX3 smaller than the exposure areas EX11 to EX33 shown in FIG. 7 are exposed using the second projection lens group 25A having the second magnification. The positions of the exposure areas FX2 to FX3 are stored in the stage controller 33 as relative coordinates (x, y) from the alignment mark A. Then, the stage controller 33 designates and moves the stage 13 and sends a signal to the DMD drive circuit 31 to sequentially expose the corresponding exposure areas FX2 to FX3.

  Before the exposure to each exposure pattern area P, the position of the alignment mark A and the index M are aligned. This alignment is performed using the monitor 45. For example, as shown in FIG. 11, the monitor 45 includes a part of the image of the alignment mark A provided on the substrate W and an index M indicating the alignment target of the second projection lens group 25A having a focal length of 5 mm. Are overlaid. The position of the index M is obtained in step S7, and is set to the center position of the projection pattern. The interval of the index M is set corresponding to the second projection lens group 25A having a focal length of 5 mm. The operator moves the stage 13 to align the center of the alignment mark A with the center of the index M. In FIG. 11, in reality, only the inside of the dotted line indicating the visual field F can be seen, but the alignment with respect to the index M can be performed using the portion with the narrow line width of the alignment mark A.

  In this way, a series of exposure operations on the substrate W is completed.

  In the maskless exposure apparatus described above, when the magnification of the second projection lens group 25, 25A... Of the projection optical system 20 is variable and the line width of the projection pattern is fine, the projection magnification is increased to project a large numerical aperture. When a narrow area is exposed using the optical system 20 and the line width of the projection pattern is rough, the projection magnification is lowered and the wide area is exposed, so that the exposure work time can be reduced.

  Further, the cross pattern (projection pattern) and the alignment mark A of the substrate W are observed through the second projection lens groups 25, 25A, and are respectively aligned with the index M displayed on the monitor (the centers are matched). Since the observation optical system 15 is provided to perform the above, it is possible to correct and reduce the deviation of the exposure position caused by the optical axis deviation caused when the second projection lens groups 25, 25A. That is, for example, if the second projection lens group is replaced from the second projection lens group 25 to the second projection lens group 25A, the position of the optical axis changes slightly, and the exposure position is shifted even if the position of the stage 13 is the same. However, by observing the position of the projection pattern of the DMD element 19 by the observation optical system 15 using the replaced second projection lens group 25A, and detecting the position of the projection pattern in a state including the optical axis deviation, the optical axis It is possible to correct the deviation of the exposure position caused by the deviation.

In this embodiment, as shown in FIG. 7, the connection portions K of the exposure areas EX11 to EX33 are overlapped and exposed. However, when the exposure is simply overlapped, as shown in FIG. The exposure amount of the portion K increases, which is not desirable. Therefore, in this embodiment, as shown in FIG. 12B, the exposure amount of the connection portion K is changed to another part by sequentially changing the micromirror direction of the DMD element 19 from the peripheral side during exposure. The exposure amount is set to be the same. Then, by changing the light amount ratio stepwise in this way, as shown in FIG. 12C, even if the position of the exposure region is slightly shifted, the change in the light amount of the connection portion K is reduced, and a continuous pattern is formed. It can be reliably formed.
(Second Embodiment)
FIG. 13 shows a second embodiment of the maskless exposure apparatus of the present invention. In this embodiment, the same elements as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, a position detection device 51 that detects the position of the alignment mark A by performing image processing on an image captured by the image sensor 43 is provided. The output of the image sensor 43 is input to the position detection device 51. In addition, the output from the position detection device 51 is input to the device controller 53 including a stage controller.

  As shown in FIG. 14, the position detection device 51 integrates the light intensity signals in the region surrounded by the thick solid line J of the image signal input from the image sensor 43 in the directions of the arrows. As a result, a one-dimensional light intensity signal as depicted around FIG. 14 is obtained. A threshold is set for the light intensity signal, and the center C of two coordinates A and B crossing the threshold is set as the center of one end of the alignment mark A. By measuring this independently in the X direction and the Y direction as shown in FIG. 14, the center of the alignment mark A can be obtained. The reason why the two integration areas are provided in the same direction is to obtain the rotation component of the alignment mark A from the deviation of the center positions.

  In this embodiment, since the position of the alignment mark A is detected by the position detection device 51, it is not necessary for the operator to perform alignment with the index M, and the work time can be shortened. Then, the coordinates of the center of the alignment mark A are obtained by image processing, and the difference from the coordinates of the center position of the projection pattern of the DMD element 19 when the fluorescent member 35 is inserted is calculated as an offset value. By adjusting the amount of movement of the stage 13 from the observed position to the exposure area EX11 that exposes the projection pattern, it is possible to easily correct the exposure position shift caused by the optical axis shift. Accordingly, the working time can be further shortened.

(Supplementary items of the embodiment)
As mentioned above, although this invention was demonstrated by embodiment mentioned above, the technical scope of this invention is not limited to embodiment mentioned above, For example, the following forms may be sufficient.

  (1) In the above-described embodiment, the example in which the exposure pattern is generated by the DMD element 19 has been described. However, for example, a spatial modulator such as a liquid crystal display element that finely divides the screen and controls the transmittance may be used.

  (2) In the above-described embodiment, the example has been described in which the magnification is changed by replacing the second projection lens group 25, 25A... With the revolver, but the magnification is changed using, for example, a zoom lens for the second projection lens group. You may make it do. Even in the case of a zoom lens, the optical axis shift occurs due to a change in magnification.

  (3) In the above-described embodiment, the example in which the projection pattern of the DMD element 19 is detected by the imaging element 43 via the fluorescent member 35 has been described. However, for example, a reflective member such as a mirror is provided instead of the fluorescent member 35 to You may make it detect by arrange | positioning a half mirror in the position of the mirror 23. FIG. When the fluorescent member 35 is used, since there is a wavelength difference between the exposure light and the fluorescent light, it is desirable to perform color misregistration correction processing on the second projection lens groups 25, 25A.

It is explanatory drawing which shows 1st Embodiment of the maskless exposure apparatus of this invention. It is explanatory drawing which shows the detail of the 2nd projection lens group of FIG. It is explanatory drawing which shows the board | substrate exposed with the maskless exposure apparatus of FIG. It is explanatory drawing which shows the exposure process using the maskless exposure apparatus of FIG. It is explanatory drawing which shows the projection pattern displayed on a monitor. It is explanatory drawing which shows the state which positioned the parameter | index to the projection pattern of FIG. It is explanatory drawing which shows the detail of the alignment mark and exposure pattern area | region of FIG. It is explanatory drawing which shows the state which matched the alignment mark with the parameter | index. It is explanatory drawing which shows the detailed shape of the alignment mark. It is explanatory drawing which shows the state from which the alignment mark has shifted | deviated from the parameter | index. It is explanatory drawing which shows the state of a monitor when enlarging the magnification of a 2nd projection lens group. It is explanatory drawing which shows the method of overlapping and exposing the connection part of an exposure area | region. It is explanatory drawing which shows 2nd Embodiment of the maskless exposure apparatus of this invention. It is explanatory drawing which shows the position detection method of the alignment mark by the position detection apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 13 ... Stage, 15 ... Observation optical system, 19 ... DMD element, 20 ... Projection optical system, 25, 25A ... 2nd projection lens group, 35 ... Fluorescent member, 45 ... Monitor, 51 ... Position detection apparatus, A ... Position alignment Mark, M ... index, W ... substrate.

Claims (9)

A stage for supporting the substrate;
A spatial light modulator that generates a desired projection pattern to be projected onto the substrate by inputting an external signal;
A projection optical system that includes an objective lens and projects the projection pattern onto the substrate;
An observation optical system for detecting an alignment mark formed on the substrate through the objective lens;
A maskless exposure apparatus comprising:
In the projection optical system, the objective lens is configured so that the projection magnification can be changed, and each time the projection magnification is changed, the alignment mark is set in advance, or the center position of the projection pattern specified in advance is set. A maskless exposure apparatus having a mechanism for aligning with respect to the mask. The maskless exposure apparatus according to claim 1,
A maskless exposure apparatus, comprising: a reflective member or a fluorescent member for projecting a projection pattern for position detection at a position different from a position on which the substrate is placed on the stage. The maskless exposure apparatus according to claim 1 or 2,
The maskless exposure apparatus, wherein the observation optical system has a monitor that displays the projection pattern, and the monitor has a preset index. The maskless exposure apparatus according to claim 1 or 2,
2. The maskless exposure apparatus according to claim 1, wherein the observation optical system includes a position detection device that detects a position of an alignment mark provided on the substrate by image processing. In a maskless exposure method in which a desired projection pattern generated by inputting an external signal is projected onto a substrate via a projection optical system including an objective lens to expose the substrate.
A first objective lens having a first projection magnification is set, and a first observation optical system including the first objective lens is used to observe an alignment mark formed on the substrate and set in advance. A first step of aligning with respect to the index or the center position of the projection pattern specified in advance,
A second step of projecting and exposing the projection pattern onto the substrate via the first objective lens;
Setting a second objective lens having a second projection magnification different from the first projection magnification, and observing the alignment mark using a second observation optical system including the second objective lens; A third step of performing alignment with respect to the index or the center position of the projection pattern;
A fourth step of projecting and exposing the projection pattern onto the substrate via the second objective lens;
A maskless exposure method comprising: The maskless exposure method according to claim 5.
The first observation optical system and the second observation optical system detect a fluorescence image of the projection pattern irradiated toward the fluorescent member or a reflection image of the projection pattern irradiated toward the reflection member. A maskless exposure method characterized by specifying a center position of the projection pattern. The maskless exposure method according to claim 5.
The first observation optical system and the second observation optical system detect a fluorescence image of the projection pattern irradiated toward the fluorescent member or a reflection image of the projection pattern irradiated toward the reflection member. A maskless exposure method, wherein the index is set with respect to the fluorescent image or the reflected image. The maskless exposure method according to claim 5 or 7,
The alignment mark on the substrate detected via the observation optical system is displayed on the monitor, and the alignment stage is moved by moving the stage on which the substrate is placed with respect to the index displayed on the monitor. A maskless exposure method comprising aligning marks and correcting the position of the stage. The maskless exposure method according to claim 5 or 6,
The position of the alignment mark on the substrate detected through the observation optical system is detected by image processing, the amount of deviation from the center position of the projection pattern is obtained, and the position of the stage is corrected. Maskless exposure method.

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