JP2004319581A - Pattern writing system and pattern writing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern writing system in which an intermediate quantity of light can be utilized without performing control using the intermediate value of a voltage being applied to each micromirror. <P>SOLUTION: A mirror device projection area 2, i.e. the outline of spots 3 arranged vertically and horizontally, is arranged obiliquely to the moving direction 4 of a substrate 1 and the substrate 1 is moved along the moving direction 4 at the time of pattern exposure. A plurality of spots 3 among spots 3 located in an effective exposure width 5 are superposed at the same places on the substrate 1 as the plurality of spots 3 move. Consequently, light exposure can be controlled in a plurality of stages at each spot position by simply controlling presence/absence of the number of irradiation times of each spot onto the substrate 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pattern writing apparatus and a pattern writing method applicable to a maskless writing apparatus used in an exposure step in manufacturing a semiconductor integrated circuit or a mask writing apparatus used for manufacturing a mask used in an exposure apparatus. .
[0002]
[Prior art]
Generally, 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 (this is called pattern exposure). And an apparatus for that purpose is called an exposure apparatus or an exposure machine. However, there is also an exposure apparatus that directly draws a circuit pattern on a wafer without using a mask, and this is called a maskless exposure apparatus.
[0003]
On the other hand, in order to manufacture a mask, it is necessary to attach a chromium film or the like for light shielding on a surface of a quartz plate or the like serving as a substrate of the mask so as to allow exposure light to pass in a pattern shape corresponding to a target circuit pattern. . This chromium film or the like is formed by pattern exposure, and an apparatus therefor is called a mask drawing apparatus. An electron beam drawing using an electron beam is generally used as a method of a mask drawing apparatus, and an apparatus for that purpose is called an electron beam drawing apparatus (hereinafter, referred to as an EB drawing apparatus).
[0004]
However, in the mask manufacturing apparatus, in addition to the EB drawing apparatus, pattern drawing (that is, pattern exposure on a mask substrate coated with a resist) using ultraviolet laser light (hereinafter abbreviated as ultraviolet laser light) is performed. An apparatus based on such a technique (sometimes called a laser beam drawing apparatus) has also been commercialized. As a conventional example of such an apparatus, a reflective mirror display element (mirror device called a digital micromirror or the like) in which a large number of minute mirrors are arranged in a two-dimensional array is used, and this is irradiated with ultraviolet laser light to reflect reflected light. A pattern is drawn on a mask substrate by controlling the pattern. It is known that this laser beam drawing apparatus has a feature that the processing speed is high because a part of the circuit patterns can be exposed collectively. Regarding this, for example, Proceedings of SPIE, Vol. 4186, PP. 16-21, or alternatively in US Pat. No. 6,428,940.
[0005]
According to this, in a conventional laser beam drawing apparatus using a mirror device, a mirror device using about one million (about 500 × about 2,000) micromirrors is used, and each micromirror has a size of about 16 microns. That's it. This is reduced and projected to a size of 1/160 on the mask substrate by the reduction projection optical system. As a result, the pattern corresponding to one micromirror is a square having a side of 0.1 micron, that is, 100 nm. However, when drawing a mask, the minimum design dimension is generally as small as 1 to 4 nm, which is called a minimum grid. Therefore, in order to realize a pattern shape much smaller than a mirror projection pattern having a side of 100 nm, the amount of light applied to the projected pattern is changed. For example, according to the above document, by changing the light amount in 64 steps (using the intermediate light amount), the minimum grid corresponds to 1.56 nm, which is 1/64 of 100 nm.
[0006]
As described above, in the conventional method of using the intermediate light amount to correspond to the minimum grid having a size smaller than the reduced projection pattern of one micromirror, the deflection angle of each micromirror in the mirror device is controlled, and thereby, the projected image is projected. Laser light intensity. In this regard, if the exposure is performed so as to move the micromirror projected every 1.56 nm which is the minimum grid (that is, scan the mask substrate), the scanning speed is reduced to 1/64, and Since the number of scans also increases 64 times, the drawing time becomes extremely long, 64 × 64 times. That is, it is considered that utilizing the intermediate light amount is indispensable for shortening the writing time in the laser beam writing apparatus.
[0007]
[Non-patent document 1]
Proceedings of SPIE, Vol. 4186, PP. 16-21
[0008]
[Patent Document 1]
US Patent No. 6,428,940
[Problems to be solved by the invention]
As described above, in the conventional method of controlling the deflection angle of the mirror to obtain an intermediate light amount, it is necessary to accurately control the voltage applied to each micro mirror. However, in order to change the intermediate light amount to 64 steps as described above, it is necessary to control the voltage by dividing it into 64 steps, and to control the voltage for a short time of 0.0005 seconds or less corresponding to 2000 Hz of the laser repetition rate. It has been difficult to accurately control the voltages of all of the approximately one million micromirrors in at least a fraction of the time. As a result, the voltage actually applied may not be exactly 64 steps, and there may be a case where the light quantity can be substantially controlled only in several steps.
[0010]
An object of the present invention is to provide a pattern drawing apparatus using a mirror device, which can use an intermediate light amount without controlling using an intermediate value of a voltage applied to each micromirror.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a pattern projection device capable of projecting a pattern composed of an aggregate of a large number of spots by using a two-dimensionally arranged light control element such as a mirror device and a microlens array is provided. In the pattern projected from the apparatus onto the substrate, by moving the substrate obliquely with respect to the arrangement of the large number of spots, some spots in the pattern due to temporally different irradiation are the same on the substrate. Irradiated so as to overlap the point. Here, the substrate is a wafer when configuring a maskless exposure apparatus according to the present invention, and is a mask substrate when configuring a mask drawing apparatus.
[0012]
According to this, since one spot position can be exposed by a plurality of irradiations, an intermediate light amount can be obtained by controlling the number of irradiations to be overlapped. Thereby, the control voltage of each micromirror may be in two stages of ON and OFF, and the voltage control does not become difficult. The reason why the intermediate light amount can be controlled by controlling the number of irradiations to the same spot on the substrate in this manner is that the diameter of the spot can be reduced by the micro lens as compared with the spot interval as described above. This is due to the oblique movement.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
A first embodiment will be described with reference to FIGS. FIG. 1 is an explanatory diagram of drawing by a pattern drawing apparatus 100 as a first embodiment of the present invention, and FIG. 2 is a configuration diagram of a pattern projection apparatus 10 constituting the pattern drawing apparatus 100. As shown in FIG. 2, the pattern projecting apparatus 10 uses a mirror device 6 as a two-dimensionally arranged light control element, which is omitted in FIG. 2, but is here 2048 × 512. (Ie, about one million) micromirrors are arranged in rows and columns at a pitch of about 16 microns. The laser beam L1 traveling from the mirror device 6 is provided to the pinhole plate 8 after being focused on a small spot through the microlens array 7. Further, the laser light L2 emitted through the hole of the pinhole plate 8 passes through the lenses 9a and 9b and is projected on the substrate 1. The lenses 9a and 9b constitute a projection optical system, and project an optical image at the position of the pinhole 8 onto the substrate 1. With this configuration, an aggregate pattern of spots separated from each other is projected onto the substrate 1 on the mirror device projection area 2 on the substrate 1 as shown in FIG.
[0015]
In the present invention, as shown in FIG. 1, the mirror device projection area 2 that defines the outer contour of the aggregate of the spots 3 arranged in the vertical and horizontal matrix forms with respect to the substrate 1, that is, in the moving direction 4 of the substrate 1. It is arranged diagonally with respect to. In other words, the rows or columns of the aggregate pattern of the matrix-like spots 3 are arranged obliquely to the moving direction of the substrate 1. In this state, the substrate 1 is moved along the movement direction 4 during pattern exposure. At this time, a plurality of spots 3 located within the effective exposure width 5 overlap at the same place on the substrate 1. That is, when the substrate 1 is viewed from the moving direction 4, the plurality of spots 3 are located at the same coordinate position in the lateral direction. FIG. 1 illustrates a case where three are at the same position. The aggregate of spots 3 depicted in FIG. 1 is the moment formed by one irradiation (one shot), but every time the substrate 1 is moved by about half the diameter of the spot 3. When irradiation is performed, it becomes possible to fill the entire surface of the substrate 1 with a connected spot.
[0016]
When such irradiation is performed, in the example shown in FIG. 1, when the moving speed of the substrate 1 is adjusted so that three spots hit the same position on the substrate 1 (that is, perform exposure), the substrate 1 In the effective exposure width 5 of, all the spots can be overlapped three times. In the present invention, utilizing this, control of the number of times of irradiation of each spot on the substrate 1 is performed (that is, whether or not the laser light is directed to the substrate 1 by the mirror device 6). By simply performing the above two controls, the exposure amount can be controlled in three stages (four stages when no irradiation is included) at each spot position.
[0017]
However, since the actual mirror device 6 has 2048 × 512 micromirrors, for example, 64 spots can be arranged so as to irradiate the same position. Can control. Using this as the number of gradations, for example, the drawing time of the drawing area of 132 × 100 mm on the substrate is calculated from the formula shown in FIG. The description of the reference numerals in (a) is shown in (b). As a design example, as shown in (c), when the modulation number (frequency) of the mirror device is 2000 Hz and the minimum grid d on the substrate is 1.56 nm, substantially every 1.56 × 64 = 100 nm It is sufficient to move the substrate so that the spot comes to the position, and as a result, the calculation result becomes as shown in (d), and the drawing time is about 12 hours.
[0018]
On the other hand, if the intermediate light amount is not used, it is necessary to move the substrate so that the entire drawing area has a spot for each minimum grid, and 0.132 × 0.100 / (1.56 nm ＾ 2) = 5.42 × 10 ＾ 15 spots are required at different positions. According to this, even if 2048 × 512 micromirrors operate at 2000 Hz, the drawing time is 718 hours, which is about 60 times as long as using the intermediate light amount.
[0019]
As described above, in the pattern drawing apparatus of the present invention, since the intermediate light amount is used, not only can the substrate be drawn at a high speed, but also it is not necessary to control the micromirror with a voltage as in the related art. The simplicity, the erroneous operation and the poor adjustment are less likely to occur, and the gradation can be accurately output.
[0020]
Next, another embodiment of the pattern drawing apparatus of the present invention will be described with reference to FIG. FIG. 4 is an explanatory diagram of pattern drawing by a pattern drawing apparatus 200 having three pattern projection apparatuses (not shown). In the mirror device projection areas 21a, 21b, and 21c projected from the three pattern projection apparatuses onto the substrate 20, by moving the substrate 20, the number of gradations set in the effective exposure areas 22a, 22b, and 22c is increased. An intermediate amount of light can be output, but the number of gradations in other areas is less than the set number of gradations. Therefore, three pattern projection devices are arranged so that the exposure regions having the number of gradations equal to or less than the set number of gradations overlap each other. Accordingly, when the substrate 21 is moved along the movement direction 24, the two mirror device projection regions overlap in the gradation number deficient regions 23a and 23b, so that the spots can be overlapped by the set gradation number. Become.
[0021]
By the way, as a problem in the case of exposing by the pattern projecting apparatus 10 capable of projecting a pattern composed of an aggregate of a large number of spots as described above, if the spots are round, if a large number of spots are exposed in close contact, FIG. Since exposure is not performed between spots as shown in (a), it is necessary to perform exposure so that adjacent spots overlap as shown in (b). However, as a result, even if the entire light is irradiated without emitting the intermediate light amount, the number of times that the spots overlap may vary depending on the position, so that the exposure may be somewhat non-uniform.
[0022]
Therefore, the spot shape may be hexagonal. According to this, as shown in FIG. 6, when the hexagons are closely arranged, it is possible to fill the entire surface with the same number of spots. Further, in the case where the same position is exposed with a plurality of shots to produce an intermediate light amount, the number of shots can be easily controlled. In order to realize a hexagonal spot, for example, the hole of the pinhole plate 8 in the pattern projection device 10 shown in FIG. Although FIG. 6 shows a hexagon, it may be an octagon.
[0023]
Next, an embodiment using a substrate drawn by the pattern drawing apparatus 100 shown in FIG. 2 will be described with reference to FIG. The mask drawing apparatus 300 shown in FIG. 7 is an apparatus that draws a mask for a general exposure apparatus on a mask substrate 31 using the large mask 30 drawn by the pattern drawing apparatus 100. That is, a pattern drawn on a large mask 30 several times as large as a normal mask is transferred onto a mask substrate 31 by a reduction projection optical system 32. Since the large mask 30 is larger than a normal mask, it is fixed vertically so as to suppress bending due to its own weight. Therefore, the 45-degree reflecting mirror 33 is used, and the laser beam L30 irradiated on the large-size mask 30 passes through the large-size mask 30 and is reflected by the 45-degree reflecting mirror 33. 32, and irradiates the mask substrate 31.
[0024]
As in the present embodiment, the pattern writing apparatus of the present invention is used for writing a large mask 30 used for writing a normal mask, and the effect of the pattern writing apparatus of the present invention is as follows. As described above, not only can the pattern be drawn with high precision by utilizing the intermediate light amount, but also the pattern can be drawn very quickly. Therefore, the drawing time does not become enormous even for the large mask 30.
[0025]
Here, the difference in pattern drawing time depending on whether or not the intermediate light amount is used according to the present invention will be described with reference to FIG. When the intermediate light amount is not used, as shown in (a), it is necessary to irradiate an exposure spot for each design minimum grid (d). / D ＾ 2 (times). On the other hand, when the intermediate light amount is used, the spot interval can be widened by the number of gradations (G) of the minimum grid (d), as shown in FIG. As a result, at first glance, the number of spots in the writing area S appears to be S / (G · d) ＾ 2 (pieces). However, since all of these spots overlap at most G times, the total number of spots is , S / (G · d) ＾ 2 × G = S / d ＾ 2 / G. That is, since the number of spots becomes 1 / G of the number of spots shown in (a), the drawing time can be reduced by the number divided by the number of gradations.
[0026]
9 shows an example of a method of manufacturing the pinhole plate 8 in the pattern projection device 100 shown in FIG. Here, a case where a square hole is formed in the pinhole plate 8 by laser light is shown. Laser light L50 from an excimer laser (not shown) impinges on a metal mask 51 having a square hole. The laser beam L51 passing through the hole of the metal mask 51 passes through the condenser lens 52 and strikes the pinhole plate 8. At this time, the condenser lens 52 forms a reduction projection optical system, and reduces and projects the image at the position of the metal mask 51 on the pinhole plate 8. Thereby, the laser beam L52 applied to the pinhole plate 8 becomes a small square, and a square hole is made.
[0027]
Further, the pinhole plate 8 is placed on an XY stage (not shown), whereby it is scanned in the X direction in the figure and steps in the Y direction. Therefore, a large number of square holes are formed in the pinhole plate 8 by the laser beam L50 that performs the repetitive pulse operation.
[0028]
In this embodiment, an excimer laser was used for drilling holes. The reason for this is that the excimer laser has a short wavelength and a low reflectivity on the metal surface, making it easy to process a metal plate, and also has a pulse width. Is as short as about 10 ns, so that even if laser irradiation is performed while the pinhole plate 8 is continuously moved, the distance traveled within the time of the pulse width can be reduced to several nanometers or less. Nothing.
[0029]
The laser that can be used is not limited to an excimer laser, but may be a laser such as a fluorine laser or a femtosecond laser that has good processing performance on metal and that can be repeatedly operated. Further, in the above-described embodiment, the case where the substrate is moved in the moving direction has been described. However, the mirror device projection area may be moved obliquely with respect to the substrate.
[0030]
【The invention's effect】
According to the pattern drawing apparatus of the present invention, gradation can be output without performing delicate voltage control on the mirror device, so that not only high-precision and high-speed drawing can be performed but also an intermediate light amount can be generated accurately and without malfunction.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a pattern projection apparatus 100 according to the first embodiment of the present invention.
FIG. 3 is an explanatory diagram of calculation of a drawing time according to the present invention.
FIG. 4 is an explanatory diagram of a second embodiment of the present invention.
FIG. 5 is an explanatory diagram of pattern drawing.
FIG. 6 is an explanatory diagram of pattern drawing according to the present invention.
FIG. 7 is a configuration diagram of a mask drawing apparatus using a large mask drawn by the pattern drawing apparatus of the present invention.
FIGS. 8A and 8B are diagrams illustrating a case where the intermediate light amount according to the present invention is not used and a case where the intermediate light amount according to the present invention is used, respectively.
FIG. 9 is a diagram illustrating an example of a method of manufacturing a pinhole plate used in the pattern projection apparatus 100 shown in FIG.
[Explanation of symbols]
1, 20 Substrate 2, 21a, 21b, 21c Mirror device projection area 3 Spot 4 Movement direction 5 Effective exposure width 6 Mirror device 7 Micro lens array 8 Pinhole plates 9a, 9b Lens 10 Pattern projector 22a, 22b, 22c Effective exposure Areas 23a and 23b Insufficient gradation number area 30 Large mask 31 Mask substrate 32 Reduction projection optical system 33 45-degree reflecting mirror 100, 200 Pattern drawing apparatus 300 Mask drawing apparatuses L1, L2, L30 Laser light

Claims (6)

A substrate, a pattern projection device that projects a pattern composed of an aggregate of a large number of spots onto the substrate using a two-dimensional array of light control elements and a microlens array, and the substrate relative to the pattern projection device. Means for moving, by moving the substrate obliquely with respect to the arrangement of the large number of spots constituting the projected pattern, a number of spots in the pattern due to temporally different irradiation, A pattern drawing apparatus for causing a pattern to be drawn so as to overlap the same spot. 2. The pattern drawing apparatus according to claim 1, wherein the spot is a polygon. The intensity of the irradiation of the spot is an intermediate gradation in one irradiation, and becomes the necessary intensity when the irradiation is performed a predetermined number of times so as to overlap the same spot on the substrate. Pattern drawing equipment. In a pattern drawing method for projecting the aggregate pattern of spots on the substrate by relatively moving any one of the aggregate pattern of spots arranged in a matrix and the substrate in a predetermined moving direction, A pattern drawing method in which a row or a column of the aggregate pattern is moved in the predetermined moving direction in an oblique state. 5. The pattern drawing method according to claim 4, wherein, during the movement of the substrate in the predetermined moving direction, the spots forming the aggregate pattern of the spots are projected onto the same position of the substrate a plurality of times. 6. The pattern drawing method according to claim 5, wherein an optical control element for giving a spot projected onto the same position on the substrate a plurality of times is on / off controlled.

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