JP2004341365A - Method for drawing mask and mask drawing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for realizing graded exposure necessary for seam exposure in a simple structure. <P>SOLUTION: In the mask drawing apparatus 100, a slit plate 2 having an opening 2' of a constant width is used. When an irradiation region R1 on a master mask 3 to be irradiated with laser light L2 exiting from the opening 2' reaches the end of a master mask in the scanning direction, laser light L1 is supplied to complete one scanning, and the laser light L1 is stopped at the moment when the irradiation region R1 reaches the other end of the master mask. By this method, as the irradiation region R1 always moves (is scanned) with respect to the master mask 3 while the laser light L1 is supplied, the exposure light quantity is not made constant in the area having the width equal to the width of the irradiation region R2 and from the both ends of a mask 6, which realizes graded exposure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mask drawing method used for drawing one mask by reduction projection and joint exposure using a plurality of master masks, and an apparatus therefor.
[0002]
[Prior art]
Generally, when manufacturing a mask (also referred to as a reticle) used in lithography which is one of the manufacturing processes of a semiconductor integrated circuit, a pattern such as a circuit is drawn on a mask substrate coated with a resist. For this purpose, an electron beam drawing apparatus is generally used. On the other hand, there is a drawing method for drawing a pattern on a mask substrate by using an exposure apparatus used in lithography. In this case, a pattern of the master mask is drawn by reduction projection exposure using a master mask having a large line width of the pattern.
[0003]
In the latter case of drawing a pattern on a mask substrate using an exposure apparatus, the size of an exposure area to which a pattern is generally transferred is smaller than the size of a drawing area of a normal mask. It is necessary to connect a plurality of patterns transferred from the printer. This is called stitching exposure and requires that edges with the same pattern be overlapped. However, adjacent patterns cannot be transferred as designed, and usually a plurality of patterns are transferred with a shift of several tens of nanometers. That is, it depends on the positional accuracy of the stage on which the mask substrate is mounted, and the variation from the target position has a value of about 10 to 30 nm even in the latest stage.
[0004]
Therefore, in the joint exposure portion of two adjacent patterns which are inevitably transferred with a slight shift, the exposure amount of the joint exposure portion is inclined so that the resist pattern generated by development after exposure is as designed as possible. (The exposure amount is reduced as approaching the end of the pattern, and the exposure amount is set to 0 at the end of the pattern). This is hereinafter referred to as tilt exposure. According to this, the width of the overlapped portion (that is, the width for inclining the exposure amount) is set to be sufficiently large with respect to the size of the displacement of the adjacent pattern, so that the exposure amount of the double-exposed portion is made substantially uniform. Because you can.
[0005]
As a specific method for realizing the oblique exposure at the joint portion, a filter having a density distribution as shown in FIG. 7 is conventionally used so that the intensity distribution of square exposure light to be irradiated on the mask decreases in the periphery. (Hereinafter referred to as an ND filter.) Regarding this, for example, Japanese Patent Publication No. 63-49218 (Patent Document 1) or Proceedings of SPIE Vol. 4186, pp. 34-45, 2001 (Non-Patent Document 1).
[0006]
The means for realizing the oblique exposure is intended for an exposure apparatus called a stepper for irradiating the entire surface of a mask with exposure light at a time and transferring patterns at once. On the other hand, in a scanning exposure apparatus that transfers a pattern by synchronously moving a mask and a substrate during exposure, the method of inclining the exposure amount using the ND filter as described above is parallel to the direction of the synchronous movement. It can be applied only to the joint exposure unit, but cannot be applied to the joint unit perpendicular to the direction of the synchronous movement (that is, the start and end of the scan). Therefore, conventionally, the width (more precisely, the width in the scanning direction) of a region (hereinafter, referred to as an irradiation region) which is irradiated with exposure light to be irradiated on a mask (or a master mask) is made variable, and the periphery of the pattern (that is, (A start part and an end part) to reduce the width. This is described in JP-A-2002-353108 (Patent Document 2).
[0007]
[Patent Document 1]
JP-B-63-49218 [0008]
[Patent Document 2]
JP-A-2002-353108
[Non-patent document 1]
Proceedings of SPIE Vol. 4186, pp. 34-45, 2001
[0010]
[Problems to be solved by the invention]
In the above-described conventional method of performing the joint exposure using the scan type exposure apparatus, it is necessary to accurately control the width of the irradiation area in accordance with the scan position, and there has been a problem that this is complicated. For example, in the conventional mask drawing apparatus 200 shown in FIG. 5, the width of the irradiation region R21 of the laser beam to be irradiated on the master mask 23 (and the irradiation region R22 on the mask 26) is changed during the scanning of the master mask 23 and the mask 26. It needs to be changed depending on the position. In the description of the mask or the master mask referred to in the present invention, it is assumed that a region where a pattern is to be drawn exists over the entire surface.
[0011]
Therefore, in the blind 22 for performing beam shaping for forming the irradiation region R21 from the laser light L21 that is the exposure light (however, as shown in the drawing, the blind 22 is actually composed of four plates) and has an opening. It was necessary to make the structure adjustable in width. That is, the shaped laser beam L22 emitted from the blind 22 is reflected by the mirrors 21b and 21c and strikes the irradiation region R21 of the master mask 23. This region is reduced and projected by the reduction projection optical system 25 onto the irradiation region R22 of the mask 26. Therefore, as shown in FIG. 6A, it is necessary to adjust the width of the irradiation region R22 (therefore, the width of the irradiation region R21 in the master mask 23) depending on the position of the irradiation region R22 in the mask 26. That is, as the irradiation region R22 approaches the left and right ends (left and right directions in FIG. 6A) of the mask 26, the width is reduced, and the blinds 22 are set so that the width becomes 0 at the moment of contact with the ends. Control. When this is accurately controlled, the oblique exposure as shown in FIG.
[0012]
As described above, in the conventional method, it is necessary to control the width of the opening formed by the blind 22 in accordance with the positions of the master mask 23 and the mask 26 that are scanning left and right, and this control is difficult. In addition, the blind 22 and the like, which is a mechanism for forming an irradiation area in a normal scanning type exposure apparatus used for exposing a chip, must be significantly modified.
[0013]
It is an object of the present invention to simplify a tilt exposure required for a joint exposure in order to perform a joint exposure using a scanning type exposure apparatus when one mask is drawn from a plurality of master masks by pattern exposure. It is an object of the present invention to provide a method which can be realized with a simple structure and an apparatus therefor.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a slit plate having a fixed opening is used to form an irradiation area in a mask, and the entire irradiation area to which the opening is transferred is a pattern transfer area in the mask. The method uses a method of controlling the irradiation of the laser light so that the laser light, which is the exposure light, is irradiated only while the device is located inside.
[0015]
According to this, since the irradiation area is always moving with respect to the mask, the exposure amount is inclined from the both ends of the mask in the scanning direction to the width of the irradiation area. Available. In other words, to put it the other way around, the irradiation area is set to the width equal to the width of the joint part in the joint exposure, and the irradiation with the laser beam is started at the moment when the irradiation area is located at one end of the mask, and the irradiation area is set to the mask. Irradiation may be controlled so that the irradiation with the laser beam is terminated at the moment when the laser beam is located at the other end.
[0016]
As described above, according to the present invention, it is possible to expose both ends of the mask obliquely by only controlling ON / OFF of the irradiation of the mask with the laser beam without changing the width of the opening in the slit plate.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a configuration diagram of a mask drawing apparatus 100 according to the present invention. In the mask drawing apparatus 100, the laser beam L1 as the exposure light is reflected on the mirror 1a and then irradiates the slit plate 2. The slit plate 2 is provided with an elongated opening 2 ′ having a width of 4 mm and a length of 104 mm. The laser beam L2 emitted from the opening 2 'is reflected by the mirrors 1b and 1c to irradiate an irradiation region R1 on the master mask 3. The master mask 3 can be scanned and moved within the master mask stage 4 in the left-right direction as shown by the arrow. The laser beam L3 traveling from the irradiation area R1 of the master mask 3 enters the reduction projection optical system 5 and irradiates the irradiation area R2 of the mask 6. That is, the image of the irradiation area R1 on the master mask 3 is reduced and projected by the reduction projection optical system 5 onto the irradiation area R2 of the mask 6 to a size of 1/4, and the pattern is exposed. That is, the irradiation region R2 has a width of 1 mm and a length of 26 mm in the present embodiment. The mask 6 is also mounted on the mask stage 7, and the mask stage 7 is driven by a driving device (not shown) so as to be able to scan and move in the left-right direction as indicated by the arrow in the figure. In the illustrated example, the master mask 3 and the mask 6 are driven by a driving device such that they can reciprocate in opposite directions. Further, the illustrated mask stage 7 is configured to be movable in the front-rear direction in the figure, that is, in the step direction. In this configuration, the pattern on the entire surface of the master mask 3 is transferred onto the mask 6, the master mask 3 is sequentially replaced, and the mask 6 is moved not only in the scan direction but also in the step direction, so that the pattern of each master mask 3 is changed. Is transferred to the entire surface of the mask 6.
[0019]
In the mask drawing apparatus 100, as shown in FIG. 2A, at the moment when the irradiation region R2 is located at the end of the mask 6 in the scanning direction, the laser beam L1 is supplied and irradiated, and one scan is completed. The laser beam L1 is controlled to stop at the moment when the irradiation area R2 reaches the other end of the mask 6. To stop the laser light L1, the laser oscillation may be stopped by a laser oscillator (not shown), or the laser light L1 may be blocked by using a shutter or the like (not shown).
[0020]
According to this configuration, while the exposure region R2 is irradiated with the exposure light, the mask 6 always moves (scans) with respect to the irradiation region R2, that is, continuously moves at a constant scanning speed. Therefore, as shown in FIG. 2B, in a range equal to the width of the irradiation region R2 from both ends of the mask 6, the exposure amount is not constant, and oblique exposure is realized. In other words, within a range equal to the width of the irradiation region R2 from both ends of the mask 6, the closer to the both ends, the shorter the irradiation time with the exposure light. As a result, the smaller the exposure amount becomes, the smaller the exposure amount becomes. Oblique exposure as shown in b) can be realized.
[0021]
As described above, since the width of the irradiation region R2 is 1 mm here, the width of the inclined portion in the oblique exposure is also 1 mm. Therefore, in the present embodiment, a joint exposure having a width of 1 mm can be realized. In other words, in the present embodiment, the width of the irradiation region R2 is substantially equal to the width of the joint exposure.
[0022]
As described above, according to the present invention, oblique exposure can be realized at both ends in the scanning direction by using the slit plate 2 having a fixed opening 2 ′ (that is, an opening having a width corresponding to the joint exposure width). In addition, the connecting exposure can be performed without significantly modifying the conventional scanning type exposure apparatus.
[0023]
Next, a new effect of the mask drawing method of the present invention will be described with reference to FIG. FIG. 3 is an explanatory view comparing the size of an irradiation area (R2 in FIG. 1) projected onto a mask substrate for pattern exposure and the size of a lens used in a reduction projection optical system (5 in FIG. 1). In the conventional scanning type exposure apparatus, the irradiation area is about 8 mm × 26 mm, and as a result, as shown by a circle in FIG. 3, a lens having an effective diameter of 27.2 mm or more is required.
[0024]
On the other hand, in the present invention, it is necessary to form an irradiation area having a width equal to the inclined portion of the oblique exposure. For example, when the width is 1 mm, when using a lens having an effective diameter of 27.2 mm, The length can be increased to about 27 mm. According to this, pattern exposure can be performed on an area having a length of 27 mm in a direction perpendicular to the scanning direction. Therefore, even if an area 1 mm from the end is used for joint exposure, as shown below, 16 times By joining, a standard size mask can be drawn.
[0025]
More specifically, the size of a pattern area in a mask used in a normal scanning exposure apparatus used for exposing a semiconductor device is 132 mm × 104 mm. When exposing such a pattern area using a 縮小 reduction projection optical system, a pattern of a maximum of 33 mm × 26 mm can be transferred onto a wafer. This size is called a maximum exposure field, and 26 mm is a length in a direction (step direction) perpendicular to the scanning direction. However, it may be 25 mm depending on the exposure apparatus manufacturer.
[0026]
Therefore, when drawing a mask having a pattern area of 132 mm × 104 mm using a conventional scanning type exposure apparatus having an irradiation area of 26 mm in the step direction, if the maximum exposure field is 33 mm × 26 mm, 4 mm in the scanning direction. It is necessary to repeat exposure four times in the step direction and four times, and to perform exposure 16 times in total. In this case, if a width of 1 mm is used for the connecting exposure, the connecting is performed four times in both the horizontal direction (scan direction) and the vertical direction (step direction), but in the direction perpendicular to the scan direction (that is, the step direction), 3 Since a portion overlaps with the location, the length becomes 26 × 4-3 = 101 mm. Therefore, it becomes slightly shorter than the pattern area of the normal mask.
[0027]
On the other hand, as described above, in the present invention, a pattern can be transferred with a length of 27 mm in a direction perpendicular to the scanning direction. Therefore, when the patterns are joined four times, the length becomes 27 × 4-3 = 105 mm, The pattern area of a normal mask can be sufficiently covered.
[0028]
By the way, as described above, in the present invention, the length of the irradiation area on the mask is 27 mm, which can be longer than the normal 26 mm. Therefore, the length in the scan direction (scan stroke) is further increased by about 3 mm from the normal 32 mm. By doing so, it is easy to enlarge the maximum exposure field to 34.7 mm × 26.4 mm.
[0029]
According to this, (132 / 26.4) × (104 / 34.7) = 5 × 3 = 15 for drawing a 4 × photomask having a pattern area of 132 mm × 104 mm, so that 15 masters are required. If a mask is used, a pattern can be drawn over the entire pattern region of the mask substrate, and one master mask can be saved compared to 16 using the usual method.
[0030]
In the above-described example, the tilt exposure in the scanning direction in the mask drawing apparatus 100 shown in FIG. 1 has been described. In the mask drawing apparatus 100 according to the embodiment of the present invention, oblique exposure in a direction perpendicular to the scanning direction (that is, a step direction) can be realized. In this case, a density filter may be used as in the related art. However, in the present invention, exposure using a blind (ie, a slit plate) 2b having a trapezoidal opening 2b 'as shown in FIG. Suggest. That is, the slit plate 2b is formed with openings 2b 'having inclined angles at both upper and lower ends in a direction (step direction) perpendicular to the scanning direction. The inclination angle in this case is directed toward the center line of the slit plate 2b.
[0031]
When a slit plate 2b having such an opening 2b 'is used, a trapezoidal irradiation region R1' is formed as shown in FIG. 4B, so that when the master mask 3 is scanned left and right, The inclined light amount can be realized at the upper and lower ends in FIG. That is, in the inclined portion of the projecting region R1 'of the master mask 3, the portion closer to the center is exposed for a longer time, and the closer to the edge, the shorter the exposure time. As a result, a density filter becomes unnecessary.
[0032]
Further, when irradiating the slit plate 2 of the mask drawing apparatus 100 shown in FIG. 1 with the laser light L1, the cross-sectional shape of the laser light L1 may be elongated using a pair of cylindrical lenses. According to this, the ratio of the laser beam L1 cut by the slit plate 2 can be reduced, and the laser beam can be efficiently used for exposure. In FIG. 4A, only the slit plate 2b having the trapezoidal opening 2b 'is described, but the shape of the opening 2b' may be rhombic.
[0033]
Next, another embodiment of the present invention will be described with reference to FIGS. 8 (a), 8 (b) and 8 (c). FIG. 8 shows a slit unit used in place of the slit plate 2 in the mask drawing apparatus 100 shown in FIG. The illustrated slit unit includes a slit plate 2c shown in FIG. 8A and a slit plate 2d shown in FIG. 8B, and is used in combination as shown in FIG. 8C. You. As shown in FIG. 8C, the two slit plates 2c and 2d are combined to form a slit-like opening 2b obliquely opened at about 45 degrees at both ends as in the slit plate 2b shown in FIG. It is possible to configure a slit unit having the same function as that of '.
[0034]
More specifically, the slit plate 2c shown in FIG. 8A has a rectangular elongated slit-like opening 2c ′ extending in a direction perpendicular to the scanning direction (ie, the step direction), while the slit plate 2c shown in FIG. The slit plate 2d shown in b) has a large rectangular opening 2d 'that partially overlaps the slit opening 2c' of the slit plate 2c. A slit unit is formed by inclining the two slit plates 2c and 2d at an angle of 45 ° with each other (here, the slit plate 2d is at an angle of 45 °) and superimposing them.
[0035]
By overlapping the slit plates 2c and 2d as shown in FIG. 8C, as shown in FIG. 8C, openings 2e that are obliquely opened at about 45 degrees at both ends are formed. Thereby, oblique exposure is realized at both ends (two sides parallel to the scanning direction) of the master mask 3 and the mask 6 shown in FIG.
[0036]
A feature of the slit plate according to the present embodiment is that the cross-sectional shape of the laser light (laser light L2 in FIG. 1) emitted from the slanted end is particularly sharp. As a result, since the oblique shape of the end portion in the irradiation region R1 of the master mask 3 becomes sharp, when performing the overlap exposure on the mask 6, a uniform exposure amount is obtained up to the end of the overlapped portion.
[0037]
On the other hand, it is actually difficult to sharply form a slit having an oblique end on one slit plate, and it is inevitable that the slit plate has a roundness of about 0.1 mm. That is, as the material of the slit plate, it is necessary to use a metal having light resistance to laser light. However, it is difficult to form a slit sharply by processing the metal plate with an acute angle portion of 0.1 mm or less. It is. As a result, when the portions exposed by the laser light emitted from the rounded corner openings are superimposed, a uniform exposure amount cannot be obtained in a portion on the mask corresponding to the corner.
[0038]
However, as shown in FIG. 8C, the two slit plates 2c and 2d are overlapped to form a laser beam emitted from these openings by using two slit plates having rectangular openings. Has a very sharp corner, and has a practical effect that the exposure of the overlapped portion can be performed extremely uniformly.
[0039]
【The invention's effect】
As described above, according to the present invention, it is possible to tilt-expose both ends in the scanning direction even by using a slit plate having a fixed opening shape, and furthermore, a commonly used scanning exposure apparatus Since the joint exposure can be performed only by replacing the slit, the cost of remodeling the scan type exposure apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a mask drawing apparatus 100 based on a mask drawing method of the present invention.
FIG. 2A is an explanatory diagram of an irradiation area on a mask 6 of the mask drawing apparatus 100.
(B) A graph showing the distribution of the exposure amount on the mask 6.
FIG. 3 is a diagram illustrating an irradiation area according to the related art and the present invention.
FIG. 4A is a configuration diagram of a slit plate 2b according to another embodiment of the present invention.
(B) is an explanatory view showing an irradiation region R1 'formed by the slit plate 2b.
FIG. 5 is a configuration diagram of a conventional mask drawing apparatus 200.
FIG. 6A is an explanatory view showing an irradiation region R22 in a conventional mask drawing apparatus 200.
6B is a graph showing an exposure amount distribution on the mask 26 of the conventional mask drawing apparatus 200.
FIG. 7A is an explanatory diagram of an ND filter which is a conventional technique for implementing oblique exposure.
(B) is a graph showing an exposure amount distribution by an ND filter which is a conventional method.
FIGS. 8A, 8B, and 8C are views showing a slit unit used in another embodiment of the present invention.
[Explanation of symbols]
1a, 1b, 1c, 21a, 21b, 21c Mirror 2, 2b, 2c, 2d Slit plate 2 ', 2b', 2c ', 2d' Opening 3, 23 Master mask 4, 24 Master mask stage 5, 25 Reduction projection optics System 6, 26 Mask 7, 27 Mask stage 22 Blinds L1, L2, L3, L21, L22 Laser light R1, R2, R21, R22 Irradiation area

Claims (9)

In a mask writing method for writing one second mask by reduction projection from a plurality of first masks, while synchronously moving each one of the first masks and the substrate for the second mask, Exposure light is applied to a slit-shaped region having a certain width with respect to the second mask substrate, and the entire region is located in a pattern transfer region on the second mask substrate. A mask writing method, wherein the irradiation of the exposure light is controlled so that the exposure light is irradiated only during the interval. In the mask drawing method of drawing one second mask by reduction projection from a plurality of first masks, of the plurality of first masks, for two first masks having adjacent patterns, On the mask substrate on which the second mask is drawn, when exposing adjacent edge portions by overlapping by a predetermined width, each one of the first masks and the mask substrate for the second mask are exposed. Mask exposure method, wherein the mask substrate is irradiated with exposure light in a slit shape having the predetermined width while synchronously moving. A mask drawing apparatus based on the mask drawing method according to claim 1. In a mask writing method for writing one second mask by reduction projection from a plurality of first masks, while synchronously moving each one of the first masks and the substrate for the second mask, The substrate is passed through a plate having at least two openings, a first plate having a slit-like opening and a second plate having a rectangular opening having at least one pair of parallel sides. A mask writing method, which comprises irradiating the exposure light. In a mask drawing apparatus that draws one second mask by joint exposure by reduction projection from a plurality of first masks, an irradiation area having a width substantially equal to the joint exposure width is used for the second mask. A mask drawing apparatus, comprising: a slit plate having an opening having a constant width formed on a substrate; and moving means for moving the irradiation area within a pattern transfer area of the substrate. 6. The moving device according to claim 5, wherein the moving unit moves the substrate in a predetermined direction, and the opening having the constant width in the slit plate extends in a direction perpendicular to a moving direction of the second mask. A mask drawing apparatus. 7. The mask drawing apparatus according to claim 6, wherein the opening of the slit plate has a trapezoidal shape. 7. The mask drawing apparatus according to claim 6, wherein the opening of the slit plate has a diamond shape. In a mask drawing method in which one second mask is drawn by joint exposure from a plurality of first masks by reduction projection, each of the first masks is formed into a slit having a predetermined width for the joint exposure. The entire area of the sheet is scanned, the slit-shaped irradiation area is sequentially irradiated to the substrate for the second mask, irradiation is started from the end of the first mask, and irradiation is ended at the opposite end. Wherein the width of the slit-shaped irradiation area is substantially constant during the scan.

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