JP2005142235A - Pattern drawing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus wherein a spot is not extended over several nm which is degree of a minimum grid even if a series optical source is used and utilization efficiency of ultraviolet light can be improved in an pattern drawing apparatus. <P>SOLUTION: A pin hole board 106 is made into a rectangle profile, a piezoelectric element 120a is attached on one side of a Y direction, and a piezoelectric element 120b is attached on one side of an X direction. The piezoelectric element can be expanded and contracted instantly with order of microsecond by application of voltage, so that the pin hole board 106 can be fine-vibrated on frequency of thousands of Hz along the Y direction by the piezoelectric element 120a. As a result, a spot and a substrate can be relatively stopped during ON time of a DMD. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention can be used as a mask drawing apparatus used for manufacturing a mask used in an exposure process when manufacturing a semiconductor integrated circuit, and further, a maskless exposure apparatus that directly draws a circuit pattern on a wafer without using a mask. The present invention relates to a pattern drawing apparatus and a drawing method that can be applied to the above. Note that a mask or wafer, which is a pattern drawing target, is referred to as a substrate unless otherwise distinguished.

  In general, in an exposure process at the time of manufacturing a semiconductor integrated circuit, a circuit pattern is drawn on a resist-coated wafer using a mask (also referred to as a reticle) on which a circuit pattern is drawn (called pattern exposure). .) There is a need, and an apparatus for this purpose is called an exposure apparatus or an exposure machine.

  On the other hand, in order to manufacture a mask, it is necessary to provide a light-shielding chromium film or the like on the surface of quartz glass or the like that serves as a mask substrate so that exposure light passes in a pattern corresponding to a target circuit pattern. . The chromium film is formed by pattern exposure, and an apparatus that performs the pattern exposure is called a mask drawing apparatus. As a method of the mask drawing apparatus, an electron beam drawing apparatus using an electron beam (hereinafter referred to as an EB drawing apparatus) is widely used.

  However, in addition to the EB lithography apparatus, the mask lithography apparatus uses a laser beam in the ultraviolet region (hereinafter abbreviated as an ultraviolet laser beam) to perform pattern drawing (that is, pattern exposure on a mask substrate coated with a resist). A laser beam drawing apparatus based on the above has also been commercialized. As a conventional example of such a device, a mirror device (called a spatial light modulator or SLM) in which a number of micro-mirrors are arranged in a two-dimensional array is used, and this is irradiated with a pulsed ultraviolet laser beam. The mask substrate is exposed by irradiating reflected light from the SLM controlled for each micromirror. It is known that this laser beam drawing apparatus has a feature that the drawing speed is faster than that of the EB drawing apparatus. This is described in, for example, Proceedings of SPIE, Vol. 4186, pages 16 to 21 (Non-patent Document 1) or USP 6,428,940 (Patent Document 1).

  On the other hand, unlike the SLM, a pattern drawing apparatus using a digital mirror device (hereinafter referred to as DMD) in which a micromirror digitally performs only ON / OFF operations may be used as a maskless exposure apparatus or the like. is there. Since the main configuration is the same as that of the pattern drawing apparatus 100 of the present invention shown in FIG. 1, the configuration of the conventional apparatus will be described with reference to FIG.

  Ultraviolet light L12 as exposure light is irradiated onto the DMD 101, and only the ultraviolet light used for drawing reflects the DMD 101 as the ultraviolet light L13 and is projected onto the microlens array 105 by the reduction projection optical system 104. The microlens array 105 divides the ultraviolet light L14 into a large number of thin light beams, which are condensed on each pinhole in the pinhole plate 106, respectively. The image of the light on the exit surface of each pinhole of the pinhole plate 106 is pattern-projected on the substrate 109 by the reduction projection optical system 108 (that is, an aggregate of spots).

  However, in the conventional pattern drawing apparatus, the pinhole plate is inclined so that the arrangement of the pinholes is slightly inclined from the X and Y directions, like the pinhole plate 400 shown in FIG. ing. As a result, as shown in FIG. 4, since the substrate 109 is scanned in the Y direction during drawing, the pattern is also projected between adjacent spots in the spot aggregate, which is a pattern projected by the first DMD ON operation. Then, exposure is performed by the subsequent ON operation of the DMD. For example, US Pat. No. 6,473,237 (Patent Document 2) shows the pattern drawing apparatus as described above.

In the laser beam drawing apparatus using the mirror device as described above, the entire surface of the DMD 101 is irradiated with ultraviolet light, so that the laser beam is finely condensed like the conventional laser beam drawing apparatus. Since there is no need to irradiate the light source, a mercury lamp can be used as an exposure light source.
Proceedings of SPIE, Vol.4186, pp. 16-21 USP6,428,940 USP 6,473,237

  It has been found that the conventional pattern drawing apparatus using DMD has the following two problems.

  As a first problem, when a pattern is drawn by forming a spot on a substrate, when a mercury lamp is used as an exposure light source, the mercury lamp emits light continuously, so when the substrate is scanned on the stage, Each projected spot is stretched long. In particular, when used for mask drawing, it is necessary to expose a pattern formed with a small dimension of 4 nm or less (generally called a minimum grid) on the mask. As a result, when the spot projected on the substrate extends about 4 nm or more from a predetermined position, a designed pattern cannot be formed.

  Therefore, the light source is sometimes turned ON / OFF with a chopper or the like. However, since the scanning speed is usually 1 mm / s or more, the ON time is set to 4 nm in order to suppress the extension of the spot shape to 4 nm or less. It was necessary to make it less than microseconds. According to this, since the DMD can operate at several thousand to 10,000 Hz (that is, with a period of 100 microseconds), at 10000 Hz, the ON time ratio must be 4% or less, and the utilization efficiency of ultraviolet light is 4% or less. The problem is that 96% or more of ultraviolet light energy is wasted.

  As a second problem, when pattern drawing is performed using the pinhole plate 400 used in the conventional pattern drawing apparatus as shown in FIG. 3, ultraviolet light hits between discrete spots. A continuously exposed area is formed. However, drawing pattern data such as a mask is usually made up of an array of orthogonal square matrices. Therefore, there is a problem that an algorithm for calculating the order and timing related to ON / OFF control of each micromirror in the DMD becomes complicated when forming a pattern by drawing.

  A first object of the present invention is to provide an apparatus capable of improving the utilization efficiency of ultraviolet light without causing the spot to extend to several nanometers or more of the minimum grid even when a continuous light source is used. That is.

  A second object of the present invention is to provide an apparatus capable of simplifying ON / OFF control of each DMD micromirror in the pattern drawing apparatus.

  In order to achieve the first object, in the present invention, a piezoelectric element is provided on the pinhole plate. It is known that a piezoelectric element can be adjusted to a length of several microns with an accuracy of several nanometers by finely adjusting an applied voltage. Therefore, if the pinhole plate is provided with a piezoelectric element, the pinhole plate itself can be moved several microns with an accuracy of several nanometers so that it can follow the operating speed of the DMD. When the pinhole plate is moved in this way, the spot projected on the substrate also moves. The projected spot can be stopped for several tens of microseconds relative to the substrate (ie, the relative velocity between the projected spot and the substrate is zero).

  In order to achieve the second object, the mirror device is attached so that the perpendicular on the surface of the mirror device is oblique to the optical axis of the reduction projection optical system, and used for drawing on the pinhole plate. The pinholes are arranged in parallel in a direction (X direction) orthogonal to the scanning direction (Y direction) of the substrate. According to this, since the arrangement in the Y direction among the arrangement of the pinholes is slightly shifted, the exposure can be performed so as to fill the space between the pinholes by scanning the substrate as in the past. it can. In addition, since the pinholes are arranged in parallel in the X direction, the algorithm for calculating the order and timing of the ON / OFF control of the micromirrors corresponding to them is extremely simplified.

  Since the pattern drawing apparatus of the present invention has the configuration described above, even when a continuous light source is used, the utilization efficiency of ultraviolet light can be improved from 4% or less to about 25%. Furthermore, the spot projection position can be finely adjusted with an accuracy of several nanometers.

  In addition, the algorithm for DMD ON / OFF control can be greatly simplified.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 4, and FIG. FIG. 1 is a block diagram of a pattern drawing apparatus 100 of the present invention. In the pattern drawing apparatus 100, ultraviolet light L 11 that is exposure light is incident on the mirror 102, and the reflected ultraviolet light L 12 is incident on the surface of the DMD 101. Here, the size of each micromirror in the DMD 101 is 14 microns per side. The ultraviolet light L13 reflected by the DMD 101 (used for drawing) passes through the projection optical system 104 composed of the lenses 103a and 103b, is magnified about 1.43 times, and the microlenses are arranged at a pitch of about 20 microns. Is projected onto the microlens array 105. The projection optical system 104 is simply shown as a two-lens configuration, but it is actually preferable to use a large number of lenses in order to suppress aberrations. For example, for the i-line exposure apparatus It is preferable to use a reduction projection optical system having a magnification of 1/5. By the microlens array 105, the ultraviolet light L14 is divided into a large number of thin light beams, which are condensed on each pinhole in the pinhole plate 106, respectively. However, the pinhole plate 106 may not be a plate that actually has holes, and a light shielding film such as Cr is provided on the glass plate so that the irradiated laser light can be divided into a number of light beams. In the present invention, a large number of holes are provided, and in the present invention, these are simply referred to as pinhole plates. A light image on the exit surface of each pinhole of the pinhole plate 106 is pattern-projected on the substrate 109 by the reduction projection optical system 108 composed of the lenses 107a and 107b.

  The magnification of the reduction projection optical system 108 is 1/5 here. Therefore, the center interval of each spot in the spot aggregate projected onto the substrate 109 is 0.4 microns. As shown in FIG. 4, since the substrate 109 is scanned in the -Y direction at a speed of 1 mm / s, the projection area 121 of the pinhole plate 106 moves on the substrate 109 at 1 mm / s in the Y direction. As a result, the exposed area 122 has been patterned.

  In the present invention, as shown in FIG. 2, the pinhole plate 106 is rectangular, and the piezoelectric element 120a is attached to one side in the Y direction, and the piezoelectric element 120b is attached to one side in the X direction. A piezoelectric element can be expanded and contracted instantaneously in the order of microseconds by applying a voltage. Therefore, the pinhole plate 106 can be slightly vibrated at a frequency of several thousand Hz along the Y direction by the piezoelectric element 120a.

  The operation of the DMD 101 and the pinhole plate 106 in this embodiment is shown in FIG. As shown in FIG. 5A, the pinhole plate 106 is reciprocated at 10000 Hz which is the same as the operating frequency of the DMD 101 with an amplitude of 250 nm. As a result, each spot in the projection region 121 of the pinhole plate 106 on the substrate 109 is reciprocated in the Y direction with an amplitude of 50 nm by the reduction projection optical system 108 having a magnification of 1/5. On the other hand, since the cycle of the reciprocating movement is 100 microseconds which is the same as that of the DMD 101, the substrate 109 moves 50 nm in 50 microseconds of a half cycle.

  On the other hand, as shown in FIG. 5B, in the DMD 101, each change from ON to OFF takes 25 microseconds, so the ON time is 25 microseconds. Therefore, the substrate 109 moves by 25 nm in the meantime. On the other hand, as described above, since each spot moves in one direction for nearly 50 microseconds of the operation of the DMD 101, the spots are not reversed during the ON time of 25 microseconds. Absent.

  As described above, in the present invention, since the pinhole plate is reciprocated at the same frequency as the DMD operating frequency, the substrate and the spot projected onto the substrate are relatively stopped during the DMD ON time. Become. Therefore, exposure can be performed during the ON time of the DMD, and even when continuous light is used as the light source, the utilization efficiency of ultraviolet light is improved to 25%.

  By the way, particularly when used for mask drawing, it is a problem common to laser beam drawing apparatuses. However, in mask drawing, it is necessary to pattern-expose a shape formed with a minimum grid of about 4 nm on the mask. . In an EB lithography apparatus, the position of an electron beam can be instantaneously controlled with a high accuracy of several nanometers by a deflector, whereas in a pattern lithography apparatus that exposes with light, it is difficult to bend the light beam itself. It is necessary to finely move a substrate such as a mask on the stage. However, since the stage is generally heavy, it is difficult to move the spot instantaneously for 1 microsecond or less, which is negligible with respect to the exposure time of the spot. On the other hand, in this embodiment, two piezoelectric elements 120a and 120b are attached to the pinhole plate 106, and can be finely moved in the Y direction and the X direction, respectively. The projection position of the projection area 121 of the pinhole plate 106 on the substrate 109 can also be finely adjusted with an accuracy of several nm in both the X direction and the Y direction. In addition, since the pinhole plate 106 is lighter than the stage, this fine adjustment can be performed instantly in 1 microsecond or less.

  Next, as a second embodiment of the present invention, a configuration obtained by further improving the pattern drawing apparatus 100 shown in FIG. 1 will be described with reference to FIG. 6, FIG. 7, and FIG.

  In the second embodiment, as shown in FIG. 6A, the DMD 201 is attached to be inclined from the horizontal plane (XY plane). That is, the DMD 201 is arranged so that the perpendicular to the device surface is oblique to the optical axis of the optical system. Further, FIG. 6B shows a case where the DMD 201 is viewed from above (Z direction). That is, when tilting from the mounting state in the normal horizontal plane (XY plane), the rotating shaft 215 has a shape when it is horizontally mounted 214 (the shape is a shape surrounded by micromirrors arranged on the outermost side). ) (Which may be either a long side or a short side) at an angle of 45 degrees. As a result, the shape of the DMD 201 at the time of oblique mounting 213 becomes a parallelogram. Therefore, the parallelogram may be mounted so that the long side thereof is parallel to the X axis.

  According to this, when the DMD 201 is projected onto the microlens array 105 by the reduction projection optical system 104 shown in FIG. 1, the arrangement shape of the microlenses (enclosed by the microlenses arranged on the outermost side). The shape is also a parallelogram. Accordingly, the microlens array 105 is different from the microlens array 105 shown in FIG. Furthermore, unlike the pinhole plate 106, the pinhole plate on which the ultraviolet light emitted from each microlens of the microlens array 105 ′ is condensed is different from the pinhole plate 106 in the present embodiment in the pinhole plate 220 shown in FIG. It is like that. That is, the shape surrounded by the pinholes arranged on the outermost side of the pinhole is a parallelogram, and the shape of each pinhole is a rectangular shape in which the direction perpendicular to the scanning direction of the substrate is the long side It has become. Note that each pinhole may have an oval shape in which the direction orthogonal to the scanning direction has a long side.

  Therefore, the projection area of the pinhole plate 220 when the pinhole plate 220 is projected and drawn is as shown in FIG. 8, and the pattern divided on the substrate 109 in the direction orthogonal to the X direction and the Y direction. The DMD 201 may be ON / OFF controlled according to the data.

  The first and second embodiments described above have been described as separate embodiments, but it is possible to combine the two embodiments.

  INDUSTRIAL APPLICABILITY The present invention can improve the accuracy of the spot projection position in a pattern drawing apparatus using a continuous light source, a micromirror, and a pinhole plate, and can easily control the micromirror with a simple algorithm. it can.

It is a block diagram of the pattern drawing apparatus 100 of this invention. 3 is a configuration diagram of a pinhole plate 106. FIG. It is a block diagram of the conventional pinhole board 400. FIG. It is a figure explaining the drawing by the pattern drawing apparatus. It is a figure explaining operation | movement of the pinhole board 106 and DMD101. (A) And (b) is a figure explaining mounting | wearing of DMD201 and its structure. It is a figure which shows the structure of the pinhole board. It is a figure explaining drawing in the case of using the pinhole board 220 shown in FIG.

Explanation of symbols

100 pattern drawing apparatus 101, 201 DMD
102 Mirror 103a, 103b, 107a, 107b Lens 104, 108 Reduction projection optical system 105, 105 ′ Micro lens array 106, 220, 400 Pinhole plate 109 Substrate 120a, 120b Piezoelectric element 121 Projection area 122 of pinhole plate 106 Exposed Area 211 Base 212a, 212b, 212c Micromirror 213 Shape 214 of DMD 210 when mounted diagonally Shape 215 of DMD 210 when mounted horizontally Rotating shaft 221 Projected area 222 of pinhole plate 220 Exposed areas L11, L12, L13, L14 , L15 UV light

Claims (5)

  Ultraviolet light generator, two-dimensional array of micromirrors, microlens array, pinhole plate that can divide irradiated ultraviolet light into many thin rays, and image on pinhole plate are transferred to the drawing target substrate A pattern drawing apparatus including a reduction projection optical system, wherein the pinhole plate includes a piezoelectric element.   Ultraviolet light generator, two-dimensional array of micromirrors, microlens array, pinhole plate that can divide irradiated ultraviolet light into many thin rays, and image on pinhole plate are transferred to the drawing target substrate In the pattern drawing apparatus including the reduction projection optical system, the shape of each pinhole in the pinhole plate is a rectangular shape or an oval shape having a long side in a direction orthogonal to the scanning direction of the substrate. Pattern drawing device.   Ultraviolet light generator, two-dimensional array of micromirrors, microlens array, pinhole plate that can divide irradiated ultraviolet light into many thin rays, and image on pinhole plate are transferred to the drawing target substrate In a pattern drawing apparatus including a reduction projection optical system, the two-dimensional array of micromirrors is arranged such that a perpendicular to the device surface of the two-dimensional array of micromirrors is oblique to the optical axis of the reduction projection optical system And a pinhole array used for drawing on the pinhole plate is arranged in parallel to a direction orthogonal to the scan direction of the substrate.   In a pattern drawing method for transferring an image given via a micromirror device and a pinhole plate while scanning a substrate to be drawn in a predetermined scan direction, the moving speed of the spot from the pinhole plate and the scan in the scan direction Performing drawing with substantially the same speed, and the perpendicular of the device surface of the micromirror device with respect to the optical axis of the optical system disposed between the micromirror device and the pinhole plate A pattern drawing method, wherein drawing is performed using at least one of the steps of drawing using the attached micromirror device so as to be inclined. 5. The pattern drawing method according to claim 4, wherein the pinholes on the pinhole plate are arranged in parallel in a direction orthogonal to the scanning direction of the substrate.

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