JP3238691B2 - Electron beam drawing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI using an electron beam.
Fast a circuit pattern or the like, relates to a sagittal drawing method collector to draw with high accuracy, in particular high-speed periodically repeated pattern, relating to that electron beam exposure method draws a high accuracy.

[0002]

2. Description of the Related Art The electron beam lithography method is indispensable for research and development of the most advanced devices because it has a feature that a fine pattern can be formed without a mask. However, there is a problem that the throughput is low because patterns are sequentially drawn. As a method of greatly improving the throughput, as shown in JP-A-62-260322, a unit figure having a repetitive figure is formed on an aperture of an electron beam lithography apparatus, and an electron beam (hereinafter, “arbitrarily shaped”) formed by this is formed. By repeatedly irradiating electron beams, the number of shots is greatly reduced and throughput is greatly improved as compared with the case of drawing with an electron beam formed by a variable shaping aperture (hereinafter, referred to as a variable shaping electron beam). It is to let.

[0003]

The above prior art does not consider the minimum repetition unit provided in the aperture, that is, the number of unit patterns arranged. The number of sequences is important for maximizing throughput.

Further, the amount of electron beam irradiation cannot be changed within one shot of an electron beam of an arbitrary shape. The inconvenience caused by this occurs, for example, in the peripheral portion of the semiconductor memory cell array as shown in FIG. For example, when a cell pattern of 64 megabits is drawn, as shown in FIG.
One micron-square shot 201 includes eight wiring patterns (corresponding to a 32-bit memory). Since the pattern density greatly changes at the outermost periphery of the memory cell array in FIG. 2B, there is a problem that the irradiation amount of the outermost peripheral pattern 202 is insufficient even within a 7-micron square, and the dimensional accuracy deteriorates.

A first object of the present invention is to provide an electron beam drawing method capable of maximizing the throughput. A second object of the present invention is to provide an electron beam having an arbitrary shape.
At the periphery of the repetitive pattern array that occurs when using
To provide an electron beam writing method that prevents dimensional accuracy deterioration in
It is in.

[0006]

In order to achieve the above-mentioned second object, an electron beam lithography method of the present invention provides an electron beam lithography system for forming a pattern including a region in which unit patterns are regularly arranged repeatedly. A method of drawing using an aperture in which a fixed number of unit pattern figures are arranged in an aperture, and a part of the area is repeated in a fixed number of unit patterns by using the aperture in which the fixed number of unit pattern figures are arranged. At the portion where the number of patterns required to be drawn in the area is smaller than the certain number in the aperture where the fixed number of unit pattern figures are arranged, the shape of the opening is repeated using a variable shaping aperture that can be arbitrarily deformed. The unit pattern figure is drawn such that the irradiation amount increases in the peripheral portion of the arrangement. In order to achieve the first object, the electron beam writing method according to the present invention is directed to forming an array pattern on a substrate by applying an arbitrary-shaped electron beam to a unit pattern provided on an aperture. a method to place the maximum number of unit patterns in said aperture, when the number of repetitions of the unit pattern repeat number of integer multiple and the aforementioned arrangement pattern of unit patterns in the apertures do not match, the sequence The remaining unit pattern in the pattern is drawn with a variable shaped electron beam. In order to achieve the first object, an electron beam writing method according to the present invention is directed to forming an array pattern on a substrate by applying an arbitrary-shaped electron beam to a unit pattern provided on an aperture. In the method, the vertical and horizontal numbers of the unit patterns to be built in the aperture are respectively the vertical and horizontal numbers of the unit patterns in the array pattern.
And next to a integral fraction of the first number, and is obtained by the maximum number that can be arranged in a region uniform electron beam at a position where said aperture is provided is obtained.

[0007]

[0008] An example of the above SL method will be described with reference to FIG. In order to improve the throughput to the maximum, the aperture for shaping an arbitrary shape electron beam array pattern entire 3
A shot 302 is arranged in which the number of repetitions of the unit pattern in 01 and an integral multiple of the unit pattern is arranged. A pattern 303 having no repetition or a pattern having a small number of repetitions even if it has repetition is drawn by a variable shaped electron beam.

Further another example of the above SL method will be described with reference to FIG. As shown in the figure, the central portion 101 of the pattern array is repeatedly drawn using an arbitrary-shaped electron beam, and the peripheral portion 1 is drawn.
02 is drawn using a variable shaped electron beam. Also, the pattern 103 having no regularity is drawn by using a variable shaped electron beam.

[0010] In the above SL manner, not necessarily perform the beginning of step and after the step by each one degree to perform the desired sequence. For example, part of the subsequent steps may be performed first, then the first step may be performed, and finally, the rest of the subsequent steps may be performed. Further, each step may be performed plural times.

[0011]

Although it is difficult to change the irradiation amount of an electron beam within one shot, as shown in FIG. 1, by using a variable shaped electron beam in the periphery of the repetitive pattern array, only the periphery can be finer. Since it becomes possible to use electron beam shots, it is possible to perform fine control of the electron beam irradiation amount, and it is possible to prevent dimensional accuracy deterioration occurring at the periphery of the pattern array.

When the pattern density is small and the effect of the proximity effect is not large, the array pattern can be drawn with an electron beam of an arbitrary shape as shown in FIG. 3, so that the number of shots is minimized and the throughput is improved. Can be.

[0013]

4, 5 and 6 show an embodiment in which the electron beam drawing method of the present invention is applied to an LSI for a MOS random access memory (DRAM). FIG. 4 shows a flow of creating drawing data. First, the LSI design data is CAD (Computer Aided).
(Design) data 401. In general, CAD data is composed of both a non-repeated pattern (random pattern) and a repetitive pattern in which a unit figure is specified to be repeated at specified coordinates and pitch. From among these, in step 402, only the repeated pattern is extracted.
The selection of a pattern to be formed in the aperture to obtain an electron beam of an arbitrary shape among several repetition patterns is determined by the size of the unit figure and the number of repetitions. An arbitrary number of these unit patterns arranged in the vertical and horizontal directions are defined as an arbitrary-shaped electron beam 405, and the number of the arrays must be a number that can provide the maximum throughput in a range where uniform electron beams can be obtained. .

The repetitive portion center region 404 excluding the designated width 403 from the peripheral portion of the repetitive pattern array, and the largest region obtained as an integral multiple of the arbitrary shape electron beam size therein as the arbitrary shape electron beam drawing region It is determined (406). The writing data is output after being divided into two types: an arbitrary-shaped electron beam writing pattern 408 and other data including non-repetitive pattern data. The data of the arbitrary-shaped electron beam pattern has a drawing coordinate, a repetition pitch (X direction, Y direction) and a repetition number (X direction, Y direction). When a plurality of electron beams of arbitrary shape are used, their identification numbers (or symbols) are added.

FIG. 5 shows an arrangement of repetitive unit figures, an arrangement of unit figures in an aperture for an arbitrary-shaped electron beam, and an electron beam irradiation method for a repetitive pattern array. The pattern shown in FIG. 5 shows a wiring pattern 501 (for 4 bits) in a memory cell of a DRAM LSI, and is regularly arranged at a pitch of 0.8 μm in the X direction and 1.6 μm in a Y direction. If these are arranged in a 7-micron square having the maximum size at which a uniform electron beam can be obtained, 4 × 2 are arranged and 5
02 aperture is obtained. That is, one shot of an arbitrary-shaped electron beam corresponds to a memory of 32 bits. In the LSI of this embodiment, 32 kilobits are configured as memory mats having the same pattern repetition.
The interior 503 of the memory mat is determined to be an arbitrary-shaped electron beam drawing area, and 31 × 31 shots are drawn. The pattern 504 in the peripheral portion is drawn by using a variable shaped electron beam.

FIG. 6 shows an electron beam irradiating method in the peripheral portion of the repetitive pattern and an irradiation amount given to each shot.
FIG. 6A shows a drawing area 601 for an electron beam having an arbitrary shape of 6.4 μm square and a drawing area 602 for a variable shaped electron beam in a peripheral portion. The variable shaping section requires 16 shots as shown in the pattern, but the arbitrary shape electron beam drawing section can draw twice the area with one shot. FIG. 6B shows the relative value of the irradiation amount given to each shot at this time. Since the irradiation amount cannot be changed within one shot of the electron beam of an arbitrary shape, a uniform irradiation amount is given as indicated by 603. However, in the peripheral portion of the memory mat, the pattern density is reduced, so that the so-called proximity effect causes a shortage from the optimal dose. In the present embodiment, by drawing the peripheral portion with a variable shaped line, the irradiation amount can be increased toward the periphery as indicated by 604 as the pattern density decreases. In the case of a substrate on which a material having a large influence of the proximity effect such as tungsten is applied, fine control of the irradiation amount as in this embodiment is required.

FIG. 7 shows a different embodiment, in which an electron beam of an arbitrary shape is applied to a contact hole pattern. In this embodiment, an example will be described in which the pattern density in the array pattern is small and the effect of the proximity effect is not so large, and the throughput is maximized.

As shown in FIG. 7, the unit pattern 701 has a pitch in the X direction of 1 micron, a pitch in the Y direction of 1 micron, and the number of repetitions of the array pattern is 64 in the X direction and 64 in the Y direction. Since the maximum electron beam size in the present embodiment is 5 μm square, 5 × 5 unit patterns can be built in the aperture when arranged at the maximum (703). In this case, the number of shots of the electron beam is 144 for the electron beam of an arbitrary shape, and the number of shots of the variable shaped electron beam in the periphery is 992 for a total of 1136 shots. On the other hand, if the number of unit figures to be formed in the aperture is set to 4 × 4, which is an integer fraction of the number of repetitions of the array pattern, (702) becomes 256 shots as a whole, rather than using the maximum electron beam size. Drawing is completed with 1/4 of the number of shots.

In general, a memory mat of an LSI often has a memory mat composed of an array of 2 n (n is an integer), so that the number of unit figures formed in the aperture is also 2 n (n is an integer). ) The largest n that falls within the aperture
It is desirable to select and arrange. However, when the number of repetitions of the unit figure is very large, the relationship of the number of shots described above may be reversed. In this case, the maximum number of unit figures are arranged in the aperture. If the number of repetitions of the unit figures in the array does not match the integral multiple of the number of unit figures in the aperture, the remaining patterns are variably formed. Draw with a line.

[0020]

According to the present invention, the number of shots can be minimized and the throughput can be improved when drawing on a substrate having little proximity effect. Furthermore, even when writing on a substrate having a large proximity effect, such as a substrate coated with tungsten or the like, fine electron beam irradiation amount control can be performed at the periphery of the array pattern array, so that writing with high dimensional accuracy is performed. be able to.

[Brief description of the drawings]

FIG. 1 is a drawing pattern diagram showing a method of drawing an array pattern using a combination of a variable shaped electron beam and an arbitrary shaped electron beam.

FIG. 2 is a diagram for explaining array pattern drawing using an arbitrary-shaped electron beam.

FIG. 3 is a drawing pattern diagram showing a method of drawing an array pattern using only an arbitrary-shaped electron beam.

FIG. 4 is a diagram showing a flow of creating a drawing pattern.

5A and 5B are a pattern diagram and an array diagram showing an irradiation method of a unit figure, an aperture for an arbitrary shape electron beam, and a repetitive pattern array.

FIG. 6 is a diagram for explaining an electron beam irradiating method in a peripheral portion of a repeated pattern and a diagram showing an irradiation amount.

FIG. 7 is a diagram for explaining the size and throughput of an electron beam of an arbitrary shape.

[Explanation of symbols]

Reference Signs List 101 Central portion of repeated pattern array 102 Peripheral portion of repeated pattern array 201 One shot of electron beam of arbitrary shape 202 Outermost pattern of array pattern 301 Whole array pattern 302 One-integral of the number of repetitions of unit pattern in array pattern 1 shot of an arbitrary shape electron beam in which is arranged 303 Non-repeated pattern 401 LSI CAD data 402 Step of extracting a repeated pattern from LSI data 403 Step of specifying a width to be excluded from the repeated pattern as a peripheral area 404 Inside of the repeated pattern Extracting the center region by excluding the peripheral region from 405. Determining the size of an arbitrary-shaped electron beam for writing the center of the repetitive pattern with the minimum number of shots. To Step of determining 407 Step of outputting a pattern to be drawn by a variable shaped electron beam 408 Step of outputting a pattern to be drawn by an arbitrary shaped electron beam 501 Unit pattern of wiring in a memory cell of an LSI 502 One shot of an arbitrary shaped electron beam 503 Central part of a memory mat 504 Peripheral part of a memory mat 601 Drawing area with an arbitrary shaped electron beam 602 Drawing area with a variable shaped electron beam 603 Irradiation amount of an electron beam with an arbitrary shaped electron beam 604 Irradiation amount with a variable shaped electron beam 701 Repeat pattern Unit pattern 702 When the unit pattern is arranged to the maximum in the aperture 703 When the unit pattern is arranged as an integral number of the repetition number in the array pattern

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Konobu Shibata 882 Ma, Katsuta-shi, Ibaraki Pref.Naka Plant, Naka Plant Inside the Device Development Center (56) References JP-A-62-260322 (JP, A) JP-A-2-111012 (JP, A) JP-A-2-122518 (JP, A) JP-A-2-125609 (JP) , A) JP-A-2-114513 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20

Claims (3)

(57) [Claims] An electron beam drawing method for drawing, using an electron beam drawing apparatus, a pattern including a region in which unit patterns are regularly arranged, wherein a predetermined number of unit pattern figures are arranged in an aperture. A part of the area is repeatedly drawn with a fixed number of unit patterns using an aperture on which the fixed number of unit pattern figures are arranged, and the required pattern number in the area is arranged with the fixed number of unit pattern figures. In a portion of the aperture less than the predetermined number, a unit pattern figure is drawn so that the irradiation amount becomes larger toward the periphery of the repetitive arrangement using a variable shaping aperture capable of arbitrarily changing the shape of the opening. Electron beam drawing method. 2. An electron beam drawing method for forming an array pattern on a substrate by applying an electron beam of an arbitrary shape to a unit pattern provided on an aperture, wherein a maximum number of unit patterns are stored in the aperture. When the arrangement is performed and the integral multiple of the number of repetitions of the unit pattern in the aperture does not match the number of repetitions of the unit pattern in the array pattern, the remaining unit patterns in the array pattern are drawn with a variable shaped electron beam. An electron beam drawing method characterized by the above-mentioned. 3. to apply any shape electron beam to a unit pattern provided in aperture, an electron beam drawing method for forming an array pattern on a substrate, the vertical unit patterns give build within the aperture And the number next to it
Each a integral submultiple vertical and horizontal <br/> number of unit patterns of the above arrangement pattern, and then disposed in a region uniform electron beam at a position where said aperture is provided to obtain An electron beam drawing method, wherein the maximum number is obtained.