JP4344162B2 - Pattern drawing apparatus and pattern drawing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pattern drawing apparatus and a pattern drawing method that can be applied to a maskless drawing apparatus used in an exposure process at the time of manufacturing a semiconductor integrated circuit, or a mask drawing apparatus used to manufacture a mask used in an exposure apparatus. .
[0002]
[Prior art]
In general, in an exposure process at the time of manufacturing a semiconductor integrated circuit, a circuit pattern is drawn on a wafer coated with a resist using a mask (also referred to as a reticle) on which a circuit pattern is drawn (called pattern exposure). The apparatus for this purpose is called an exposure apparatus or exposure machine. However, there is also an exposure machine that directly draws a circuit pattern on a wafer without using a mask, and this is called a maskless exposure machine.
[0003]
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 a quartz plate or the like serving as a mask substrate so that exposure light passes in a pattern corresponding to a target circuit pattern. . This chrome film or the like is formed by pattern exposure, and an apparatus therefor is called a mask drawing apparatus. As a mask drawing apparatus technique, electron beam drawing using an electron beam is generally used, 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 is performed using ultraviolet laser light (hereinafter abbreviated as ultraviolet laser light) (that is, pattern exposure is performed on a mask substrate coated with a resist). An apparatus based on this technique (sometimes called a laser beam drawing apparatus) has also been commercialized. As a conventional example of such an apparatus, a reflection mirror display element (mirror device called a digital micromirror) in which a number of micromirrors are arranged in a two-dimensional array is used. Patterns are drawn on the mask substrate under pattern control. This laser beam drawing apparatus is known to have a high processing speed because a part of the circuit pattern can be exposed at a time. This is described in, for example, Proceedings of SPIE, Vol. 4186, PP. 16-21, or USP 6,428,940.
[0005]
According to this, in a conventional laser beam drawing apparatus using a mirror device, a mirror device using about 1 million (about 500 × about 2000) 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 a reduction projection optical system. As a result, the pattern corresponding to one micromirror is a 0.1 micron side, that is, a 100 nm square. 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 far smaller than a mirror projection pattern having a side of 100 nm, the amount of light irradiated on the projected pattern is changed. For example, according to the above document, the minimum grid is made to correspond to 1.56 nm, which is 1/64 of 100 nm, by changing the light amount in 64 steps (using an intermediate light amount).
[0006]
As described above, in the conventional method using the intermediate light quantity and corresponding 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 thus the projection is performed. The intensity of the laser beam is changed. In this regard, if exposure is performed so that the micromirror projected every 1.56 nm which is the minimum grid is moved (that is, scanning of the mask substrate), the scanning speed is reduced to 1/64, and Since the number of scans increases 64 times, the drawing time becomes extremely long as 64 × 64 times. In other words, the use of the intermediate light amount is indispensable for shortening the drawing time in the laser beam drawing apparatus.
[0007]
[Non-Patent Document 1]
Proceedings of SPIE, Vol.4186, PP.16-21
[0008]
[Patent Document 1]
US Pat. No. 6,428,940 [0009]
[Problems to be solved by the invention]
As described above, in the conventional method of controlling the deflection angle of the mirror in order to obtain the intermediate light amount, it is necessary to accurately control the voltage applied to each micromirror. However, in order to change the intermediate light quantity into 64 steps as described above, it is necessary to control the voltage by finely dividing it into 64 steps, and a short time of 0.0005 seconds or less corresponding to the repetition rate of the laser of 2000 Hz. It was difficult to accurately control all the voltages of approximately one million micromirrors within at least a fraction of the time. As a result, there are cases where the actually applied voltage does not have exactly 64 steps, and variation occurs, so that the amount of light can be substantially controlled by only a few steps.
[0010]
An object of the present invention is to provide a pattern drawing apparatus that can use an intermediate amount of light in a pattern drawing apparatus using a mirror device without 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 apparatus capable of projecting a pattern made up of a large number of spots by using a two-dimensional array of light control elements such as a mirror device and a microlens array, In the pattern projected onto the substrate from the apparatus, the substrate is moved obliquely with respect to the array of the multiple spots, so that several spots in the pattern due to temporally different irradiation are the same on the substrate. It was irradiated so as to overlap the spot. Here, the substrate means a wafer when a maskless exposure apparatus is constituted according to the present invention, and a mask substrate when a mask drawing apparatus is constituted.
[0012]
According to this, since one spot position can be exposed by a plurality of irradiations, it becomes possible to emit an intermediate amount of light by controlling the number of irradiations to be overlapped. As a result, the control voltage of each micromirror may be in two stages, ON and OFF, and voltage control is not difficult. In addition, the intermediate light quantity can be controlled by controlling the number of times of irradiation to the same point on the substrate in this way because the diameter of the spot can be made smaller than the spot interval by the microlens as described above. It originates in moving it diagonally.
[0013]
DETAILED DESCRIPTION OF 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 block diagram of a pattern projection apparatus 10 constituting the pattern drawing apparatus 100. As shown in FIG. 2, the pattern projection apparatus 10 uses a mirror device 6 as a two-dimensional array of light control elements, which is omitted in FIG. 2, but here it is 2048 × 512. Individual (ie, about 1 million) micromirrors are arranged vertically and horizontally at a pitch of about 16 microns. The laser light L 1 traveling from the mirror device 6 is focused on a small spot through the microlens array 7 and then applied to the pinhole plate 8. Further, the laser beam L2 emitted through the hole of the pinhole plate 8 passes through the lenses 9a and 9b and is projected onto 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, as shown in FIG. 1, an aggregate pattern of spots separated from each other is projected onto the substrate 1 in the mirror device projection region 2 of the substrate 1.
[0015]
In the present invention, as shown in FIG. 1, the mirror device projection region 2 that defines the outer contour of the aggregate of spots 3 arranged in the form of a vertical and horizontal matrix is relative to the substrate 1, that is, in the moving direction 4 of the substrate 1. It is arranged diagonally. In other words, the rows or columns of the aggregate pattern of the matrix-like spots 3 are arranged obliquely with respect to the movement direction of the substrate 1. In this state, the substrate 1 is moved along the moving 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 direction of the moving direction 4, the plurality of spots 3 are at the same coordinate position in the lateral direction. In FIG. 1, the case where three pieces are at the same position is illustrated. 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 a length that is about half the diameter of the spot 3. When irradiation is performed, it is 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 the three spots hit the same position on the substrate 1 (that is, exposure is performed), the substrate 1 Within the effective exposure width of 5, all spots can be overlapped three times. In the present invention, this is utilized to control the presence / absence of the number of times each spot is irradiated on the substrate 1 (that is, whether the laser light is directed toward the substrate 1 or not by the mirror device 6). The exposure amount can be controlled in three steps (four steps if no irradiation is included) at each spot position simply by performing the above two controls.
[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, and thereby the exposure amount can be increased in 64 steps at each spot. Can be controlled. With this as the number of gradations, for example, the drawing time of a 132 × 100 mm drawing area on the substrate is calculated from the formula shown in FIG. In addition, description of the code | symbol in (a) was 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. The substrate may be moved so that the spot comes to the spot, and the calculation result is as shown in (d), and the drawing time is about 12 hours.
[0018]
On the other hand, if the intermediate light quantity is not used, it is necessary to move the substrate so that a spot is provided for every minimum grid in the entire drawing area. 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 longer than when using an intermediate light quantity.
[0019]
As described above, since the pattern drawing apparatus of the present invention uses the intermediate light amount, not only can the substrate be drawn at a high speed, but there is no need to control the micromirror with a voltage as in the prior art. This simplifies operation, prevents malfunctions and adjustment errors, and makes it possible to accurately produce gradations.
[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 the pattern drawing device 200 having three pattern projection devices (not shown). In the mirror device projection areas 21a, 21b, and 21c projected from the three pattern projection apparatuses onto the substrate 20, the number of gradations set in the effective exposure areas 22a, 22b, and 22c can be increased by moving the substrate 20. An intermediate amount of light can be output, but in other areas, the number of gradations set is not reached. In view of this, three pattern projection apparatuses are arranged so that the exposure areas of the set number of gradations or less overlap each other. As a result, when the substrate 21 is moved along the moving direction 24, the two mirror device projection areas overlap even in the insufficient number of gradation areas 23a and 23b, so that the spots can be overlapped by the set number of gradations. Become.
[0021]
By the way, as a problem in the case of exposure by the pattern projection apparatus 10 capable of projecting a pattern composed of a large number of spots as described above, when a spot is round, when a large number of spots are exposed closely, FIG. As shown to (a), since between spots are not exposed, as shown to (b), it is necessary to expose so that an adjacent spot may overlap. However, as a result, even if all of the light is irradiated without emitting an intermediate amount of light, the number of overlapping spots varies depending on the position, so that the exposure may be somewhat uneven.
[0022]
Therefore, the spot shape may be a hexagon. According to this, as shown in FIG. 6, when the hexagons are closely arranged, the entire surface can be filled with the same number of spots. In addition, when the same position is exposed with a plurality of shots to produce an intermediate amount of light, the number of shots can be easily controlled. Further, in order to realize a hexagonal spot, for example, the hole of the pinhole plate 8 in the pattern projection apparatus 10 shown in FIG. In addition, although the hexagon was shown in FIG. 6, an octagon may be sufficient.
[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. A 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 the size of a normal mask is transferred to 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 in order to suppress bending due to its own weight. Therefore, a 45-degree reflecting mirror 33 is used, so that in the laser light L30 irradiated to the large-sized mask 30, what passes through the large-sized mask 30 is reflected by the 45-degree reflecting mirror 33, and the reduced projection optical system. 32, and the mask substrate 31 is irradiated.
[0024]
As in this embodiment, the pattern drawing device of the present invention is used for drawing a large mask 30 used for drawing a normal mask. As an effect, the pattern drawing device of the present invention is the same as that described above. As described above, not only can the pattern be drawn with high accuracy by using the intermediate light quantity, but also the pattern can be drawn at a very high speed. Therefore, the drawing time for the large mask 30 does not become enormous.
[0025]
Here, a difference in pattern drawing time depending on whether or not the intermediate light amount according to the present invention is used will be described with reference to FIG. When the intermediate light quantity is not used, as shown in (a), it is necessary to irradiate an exposure spot for each designed minimum grid (d). Therefore, when the drawing area is S, the number of spots is S. / D ^ 2 (times). On the other hand, when the intermediate light quantity is used, as shown in (b), the spot interval can be increased by the number of gradations (G) times of the minimum grid (d). As a result, the number of spots in the drawing area S at first glance seems to be S / (G · d) ^ 2 (pieces). However, since all these spots overlap at the maximum G times, the total number of spots is , S / (G · d) ^ 2 × G = S / d ^ 2 / G. That is, since it becomes 1 / G of the number of spots shown in (a), the drawing time can be shortened by the number divided by the number of gradations.
[0026]
An example of a method for manufacturing the pinhole plate 8 in the pattern projection apparatus 100 shown in FIG. 2 is shown in FIG. Here, a case where a square hole is formed in the pinhole plate 8 by laser light is shown. A laser beam L50 from an excimer laser (not shown) hits a metal mask 51 having a square hole. The laser beam L51 that has passed through the hole of the metal mask 51 passes through the condenser lens 52 and strikes the pinhole plate 8. At this time, the condensing lens 52 forms a reduction projection optical system so that the image of the position of the metal mask 51 is reduced and projected onto the pinhole plate 8. As a result, the laser beam L52 applied to the pinhole plate 8 becomes a small square, and a square hole is formed.
[0027]
The pinhole plate 8 is placed on an XY stage (not shown), so that it is scanned in the X direction and steps in the Y direction. Accordingly, 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 example, an excimer laser was used for drilling. The reason for this is that the excimer laser has a short wavelength and low reflectivity on the metal surface, which makes it easy to process a metal plate, as well as a pulse width. Since the distance is as short as 10 ns, the distance traveled within the pulse width time can be reduced to a few nanometers or less even when laser irradiation is performed while moving the pinhole plate 8 continuously, so that the square hole extends long. There is nothing.
[0029]
In addition to the excimer laser, a laser that can be used may be any laser such as a fluorine laser or a femtosecond laser, which has a good processing performance for metal and can be repeatedly operated. In the above-described embodiments, the case where the substrate is moved with respect to the moving direction has been described. However, the mirror device projection region 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 obtained without performing fine voltage control on the mirror device, so that not only high-precision and high-speed drawing can be performed, but also intermediate light quantity 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 respectively showing 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.
9 is a diagram for explaining an example of a method for manufacturing a pinhole plate used in the pattern projection apparatus 100 shown in FIG. 2. 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 plate 9a, 9b Lens 10 Pattern projection device 22a, 22b, 22c Effective exposure Areas 23a, 23b Insufficient number of gradation areas 30 Large mask 31 Mask substrate 32 Reduction projection optical system 33 45 degree reflector 100, 200 Pattern drawing apparatus 300 Mask drawing apparatuses L1, L2, L30 Laser light

Claims (6)

A pattern projection apparatus for projecting a pattern composed of an assembly of a large number of spots onto a substrate using a two-dimensional array of light control elements that modulate laser light at a predetermined modulation number, a microlens array, and a pinhole plate; the substrate and means for relatively moving with respect to the pattern projection device, the repetition frequency of the laser beam Ri Contact is selected to correspond to the number of modulation of the light control element, and was projected shadow pattern constituting the relative number of arrangement the moving direction of the substrate of the spot, is arranged obliquely, and the arrangement of the diagonal of the large number of spots, the spot in the pattern by between distinct irradiation time is, floors a number of times corresponding to the tone number, wherein so as to overlap the same point on the substrate, with a pattern drawing while being set, the shape of the spot of the pinhole plate Pattern writing apparatus characterized by adjustable in the shape. 2. The pattern drawing apparatus according to claim 1, wherein the spot is a hexagon or an octagon . The intensity of irradiation of the spot is an intermediate gradation in one irradiation, and becomes a necessary intensity when irradiated so as to overlap the same spot on the substrate by the number of times corresponding to the number of gradations. The pattern drawing apparatus according to claim 1. Using a two-dimensional array of light control elements that modulate laser light at a predetermined modulation number, a microlens array, and a pattern projection device that projects a pattern composed of an assembly of many spots onto the substrate using a pinhole plate In the pattern drawing method for projecting the spot aggregate pattern onto the substrate by relatively moving either one of the spot aggregate pattern arranged in a matrix and the substrate in a predetermined movement direction, The repetition frequency of the laser light is selected according to the modulation number of the light control element, and the row or column of the aggregate pattern of spots having a shape corresponding to the shape of the hole of the pinhole plate is temporally changed. spot in the pattern with different irradiation, a number of times corresponding to the number of gradations, so as to overlap the same point on the substrate, and oblique By moving in the predetermined direction of movement state, pattern exposure method characterized by performing pattern drawing. The spot constituting the spot aggregate pattern is projected a plurality of times according to the number of gradations at the same position on the substrate during movement of the substrate in the predetermined movement direction. 5. The pattern drawing method according to 4.   6. The pattern drawing method according to claim 5, wherein an optical control element that gives a spot projected on the same position of the substrate a plurality of times is controlled to be turned on and off.

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