JP3290699B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method for forming a circuit pattern of a semiconductor integrated circuit and other fine elements on a semiconductor wafer or a mask, and more particularly to a pattern forming method using a charged beam.

[0002]

2. Description of the Related Art Conventionally, in order to form a circuit pattern on a semiconductor wafer or a mask, a method of drawing a pattern using an electron beam or a method of transferring a pattern by light has been used. Drawing of a circuit pattern using an electron beam has a higher resolution but requires much longer time than transfer of a circuit pattern by light.

Recently, a character projection method has been proposed as a method for solving this problem. This is a method in which the shape of the figure of the minimum unit of the repetitive pattern is formed in a shaping aperture of the electron optical system, and drawing is performed using the aperture in the area of the repetitive pattern. With this method, the number of shots required for drawing can be significantly reduced.

However, an actual circuit pattern includes an area that does not repeat, and the number of shots does not change in other areas even if the character projection method is applied to the repeat area. For this reason, when drawing by continuous movement of the stage, there is a problem that the stage speed cannot be increased and the drawing time cannot be reduced.

[0005] Although the number of shots can be reduced by increasing the character size, if the size of the figure to be characterized on the sample is not negligible compared to the spread of the backscattering of the charged beam, the number of shots is reduced. Even if the proximity effect is corrected by changing the irradiation amount, the proximity effect inside the characterized figure cannot be corrected. For this reason, there is a problem that a portion drawn with a character does not have a desired pattern size.

[0006]

As described above, in the conventional pattern forming method, there is a problem that the resolution is limited in light exposure, and the drawing time is very long in electron beam drawing even if the character projection system is used. Was. This has been particularly acute in semiconductor devices with small design rules and high integration.

When the character beam size is set to a size that cannot be ignored in comparison with the spread of backscattering on the sample surface, even if the irradiation amount is changed for each shot in order to correct the proximity effect, the figure in the character is not changed. It is impossible to correct the proximity effect with sufficient accuracy, and the size of the character beam on the sample surface was made sufficiently small compared to the spread of backscattering to obtain sufficient correction effect of the proximity effect. In such a case, there is a problem that the throughput is reduced.

The present invention has been made in view of the above circumstances, and aims at maximizing the advantage of the character projection system using a charged beam and shortening the drawing time. It is to provide a pattern forming method.

Another object of the present invention is to reduce the number of shots by increasing the size of the character beam on the sample surface as much as possible without reducing the throughput.
Another object of the present invention is to provide a pattern forming method capable of sufficiently correcting the proximity effect.

[0010]

The gist of the present invention is to divide the entire drawing area into a repetitive pattern area that can be drawn by the character projection method and an area that cannot be drawn by the character projection method. It is to draw by a stage moving method, a stage moving direction, a stage speed, and the like.

That is, according to the present invention, in a pattern forming method for irradiating a charged beam onto a sample while continuously moving a stage on which the sample is mounted to draw a desired pattern, the entire projection area on the sample is subjected to character projection. The area where the repetitive pattern exists and the area where the repetitive pattern does not exist are divided into the area where the repetitive pattern does not exist. This is a method of drawing by a beam or transferring by a light stepper.

More specifically, in drawing by the character projection method, a continuous stage movement method is adopted, and the stage speed is maximized. In writing with a variable shaped beam, the stage is slowed down using a step-and-repeat method or a continuous movement method. As a result, the overall drawing speed is reduced. Further, in a part or all of the area where drawing is not possible by the character projection method, if the design rule of the existing pattern can be resolved by light, the pattern is transferred using an optical stepper.

Further, according to the present invention, at least a figure which is a minimum unit of a repetition pattern is directly formed as one large character in an aperture, and the figure which is the minimum unit is formed of two pieces having a size sufficiently smaller than the spread of backscattering. The small characters are formed in the aperture, and a large character is used at the center of the repetition pattern where the influence of the proximity effect is uniform, and two or more small characters are used at the end of the repetition pattern where the influence of the proximity effect is not uniform. It is characterized by drawing using a character. Further, in the end portion of the repetitive pattern in which the influence of the proximity effect is not uniform, writing is performed using a variable shaped beam having a maximum beam size smaller than the spread of backscattering instead of the small character.

That is, a character having a relatively large size is used in a region where the influence of the proximity effect is uniform, and a character having a size sufficiently smaller than the spread of the backscatter or the spread of the backscatter in a region where the influence of the proximity effect is not uniform. It is characterized in that a variable shaped beam having a sufficiently smaller maximum beam size is used.

[0015]

According to the present invention, the entire drawing area is divided into a repetitive pattern area that can be drawn by the character projection method and an area that cannot be drawn by the character projection method. By drawing in the moving direction and the stage speed, the drawing time can be reduced. The reason will be described below.

Assume that there is chip data as shown in FIG. In the hatched portion 1 in the figure, there is a repetitive pattern that can be drawn by the character projection method, and the other places 2 are areas that cannot be drawn by the character projection method. FIG. 2 shows a state where the chip data of FIG. 1 is divided by a frame 3 having a width of 0.5 mm.

The stage moves continuously along the frame 3. In this case, in one frame 3 in the conventional method, there is always a pattern area 2 for which the character projection method cannot be used. It is assumed that a frame in only the area 1 where drawing can be performed by the character projection method can be drawn at a stage speed of 20 mm / s, and a pattern that can be drawn by a variable shaping beam has a pattern that can be drawn at a stage speed of 1 mm / s.

In the continuous stage moving method, it is impossible to change the stage speed in the middle of a frame. Therefore, even in a frame in which an area 1 that can be drawn by the character projection method and an area 2 that cannot be drawn by the character projection method are mixed. , The stage speed must be 1 mm / s. Therefore, in the conventional method, even if a chip as shown in FIG. 1 is drawn by using the character projection method, the stage speed is 1 mm / s in all frames, and as a result, the drawing time required for one chip is (14/0) .5) × (14/1) = 392 sec, which is about 7 minutes.

In the present invention, the chip shown in FIG.
(1) and (3) are drawn by a stage continuous movement method and a stage speed of 1 mm / s, and (2) are drawn by a character projection method at a stage continuous movement method and a stage speed of 20 mm / s. In (4) and (5), drawing is performed in a step-and-repeat method with the next step moving time of 0.1 second, and 0.5 mm × 0.5 mm is separated in one second. Then, the total drawing time is (4 / 0.5) × 14 + (10 / 0.5) × 0.5 + (40 / 0.25) × 1.1 = 298 sec, which is about 5 minutes, and it is possible to draw in a shorter time than the conventional method. Become.

Further, (1) and (3) are drawn by a stage lateral continuous movement method and a stage speed of 1 mm / s, and (2) is a stage lateral continuous movement method and a character projection method by a stage speed of 1 mm / s. Draw, (4), (5)
Is the stage vertical continuous movement method, stage speed 1 mm /
When drawing with s, the total drawing time is (4 / 0.5) × 14 + (10 / 0.5) × 0.5 + (4 / 0.5) × 10 = 202 sec, which is about 3.4 minutes, which is a shorter time than the conventional method. Can be drawn.

If all or a part of the areas (1), (3), (4), and (5) has a pattern size that can be resolved by light, the area is subjected to an optical stepper. Exposure can be performed, in which case the overall drawing time will be shorter.

As described above, according to the present invention, the characteristics of the character projection system can be fully exploited, and the time required for pattern formation can be greatly reduced. Particularly, it is very effective in forming an integrated circuit pattern having a small design rule in which an optical stepper cannot be used.

Further, according to the present invention, the area of the repetitive pattern that can be drawn by the character projection method is divided into an area where the influence of the proximity effect is uniform and an area where the influence of the proximity effect is not uniform. In a non-uniform area, draw with a character whose size on the sample surface is sufficiently smaller than the spread of backscatter, or a variable shaped beam with a maximum beam size whose size on the sample surface is sufficiently smaller than the spread of backscatter. Accordingly, the proximity effect can be sufficiently corrected and drawing can be performed using a large-sized character, so that the number of shots required for drawing can be reduced. The reasons are described below.

When the proximity effect is corrected by changing the irradiation amount by changing the irradiation time for each shot, FIG.
As shown in (2), the correction error becomes larger as the shot size for setting the irradiation time is larger than the backscatter. Note that this characteristic is such that an electron beam is applied to an Si substrate at an acceleration voltage of 50.
This is an example in which line and space (L / S) were drawn by irradiating at kV, and the spread σb of backscattering was 10 μm.

To reduce the correction error, the shot size for setting the irradiation time must be sufficiently smaller than the spread of the backscatter. For example, when an electron beam is used, the size of a shot for setting the irradiation amount at an acceleration voltage of 50 kV and a Si substrate needs to be 2 μm or less, which is sufficiently smaller than the spread of backscattering of 10 μm. Therefore, if the size of the character on the sample surface is made larger than this, the correction error inside the character increases.

However, as shown in FIG. 16, when drawing a region of a repetitive pattern sufficiently wider than the backscattering spread, the correction error increases when the shot size is increased at the end of the repetitive region. In a portion sufficiently distant from the edge of, the correction error does not increase even if the shot size is increased. Therefore, FIG.
As shown in the figure, the end portion of the repetition region is drawn with a character beam whose size on the sample surface is sufficiently smaller than the spread of the backscattering, and a large size is formed in the region sufficiently far from the end of the repetition region. Character beam.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a schematic structural view showing an electron beam drawing apparatus used in the method of one embodiment of the present invention. 10 in the figure
Is a sample chamber, 11 is a target (sample), 12 is a sample stage (stage), 20 is an electron optical column, 21 is an electron gun, 2
2a to 22e indicate various lens systems, 23 to 26 indicate various deflection systems, 27a indicates a blanking plate, 27b indicates a first shaping aperture mask, and 27c indicates a second shaping aperture mask. A character pattern as described later is also formed on the second formed aperture mask 27c, and drawing by a character projection method is possible.

In the figure, reference numeral 31 denotes a sample stage drive circuit unit;
Is a laser measuring system, 33 is a deflection control circuit, 34 is a blanking control circuit, 35 is a variable shaped beam size control circuit, 36 is a buffer memory and control circuit, 37 is a control computer, and 38 is a data conversion computer. , 39 indicate a CAD system.

The electron beam emitted from the electron gun 21 is
ON-0FF control is performed by the blanking deflector 23. By adjusting the irradiation time at this time, the present apparatus can change the irradiation amount according to the irradiation position. The beam that has passed through the blanking plate 27a is
The beam shaping deflector 24, the first shaping aperture mask 27b, and the second shaping aperture mask 27c are shaped into a rectangle, a right triangle, and a character, and their dimensions are varied. The shaped beam is deflected and scanned on the target 11 by the scanning deflectors 25 and 26.
Are drawn in a desired pattern.

Next, an electron beam drawing method using the above-described apparatus, particularly a character projection method and a drawing method using a normal variable shaped beam will be described. FIG. 5A shows a variable shaped beam aperture formed in the mask 27c and a rectangular aperture formed in the mask 27b.
(B) shows an aperture for character projection formed on the mask 27c.

FIG. 6 shows an image of the chip 5 occupying the wafer (or mask) 4 and a drawing direction. Chip 5 is divided into frame 3 and frame 3 is divided into subfields 6
Is divided into The stage moves along the frame 3. After drawing the first frame 3, the second frame 3 is drawn by moving the stage in the opposite direction. Drawing is performed while the moving direction of the stage is repeated as a forward direction and a reverse direction as shown in the figure. Conventionally, even if the character projection method is used, the stage speed cannot be increased because of an area that cannot be drawn by a character.

FIG. 7 is an image of the chips 5 arranged on the wafer. The hatched portion 1 is a region to be drawn by character projection, and the other portion 2 is a region to be drawn by a variable shaped beam. FIG. 8A shows one chip 5 taken out, and FIG. 8B shows an image of a repetitive element in the chip 5. The area shown in FIG. 8B is drawn by the aperture shown in FIG.

In the conventional method, the entire chip is drawn at a time. On the other hand, in the present embodiment, when the CAD data is first converted into electron beam drawing data, it is output as three drawing data (I), (II) and (III) as shown in FIG. (I) is a chip that is not drawn by the character and is parallel to the stage moving direction, (II) is a chip that is drawn by the character, and (III) is a chip that is not drawn by the character and is vertical to the stage moving direction. (I) to (III) are arranged as shown in FIG. 7, and (a), (b) and (c) in FIG.
It is.

The layout data (a) to (c) is created by the control computer 37 shown in FIG. 4 and stored in a memory as a drawing file. The drawing file also includes various drawing conditions. For (a), continuous stage movement, stage speed 1 mm / s, for (b), continuous stage movement, stage speed 20 mm / s, (c) For step and repeat, step travel time 0.1
Seconds are set. When one wafer is drawn using the drawing files corresponding to (a), (b) and (c), the drawing is performed as shown in FIG.

When drawing as shown in FIG. 11, the size of the field to be drawn by step and repeat is 0.5 m.
If mx 0.5 mm, the writing time is 1 per wafer
Time, which can be reduced to about half of the conventional two hours.

Next, a description will be given of an embodiment in which light transfer is also used. It is assumed that all the non-drawable areas in the character projection in FIG. 7 can be resolved by the optical stepper. In FIG. 9, among the drawing data (I) to (III) created by the data conversion system, (I) and (I)
(III) creates a mask for optical transfer from this data as data for a mask generator. (II) is directly stored in the drawing system as drawing data. It is assumed that the area to be drawn by the character projection includes a pattern which exceeds the resolution limit of light and needs to be exposed by an electron beam.

FIG. 12 shows an example of a process in the case where both light transfer and electron beam drawing using the character projection method are used. First, as shown in (a), the resist 52 on the substrate 51 is exposed by an optical stepper, and then development is performed as shown in (b). Next, after exposure by electron beam lithography as shown in (c), development is performed as shown in (d). Thereby, all necessary patterns are formed. FIG.
Step 2 can be performed in the order of (a) → (c) → (b) or (d) by optimizing the process conditions.

When light transfer is used, the exposure per wafer is 1
It takes about a minute. Electron beam lithography using only characters is 2.5 minutes per wafer, and the time required for pattern formation can be greatly reduced as compared with the case where only electron beam lithography is used.

The following drawing method can also be used for (a), (b) and (c) of FIG. (A) is a continuous lateral movement of the stage, a stage speed of 1 mm / s,
(B): continuous horizontal movement of the stage, stage speed 20 m
m / s, (c) is the stage vertical continuous movement and the stage speed is 1 mm / s. In this case, writing is performed as shown in FIG. 13, and the writing time per wafer is about 50 minutes. Therefore, the drawing time is reduced to about half of the conventional case.

In the drawing method described above, the drawing data (I) to
Of (III), (I) and (II) can be one drawing data. FIG. 14 shows an image of the drawing data in this case. (A) corresponds to the combination of the drawing data of (I) and (II), and (b) corresponds to the drawing data of (III). Corresponding to (A) is drawn by the horizontal continuous movement method, and (b) is drawn by the step-and-repeat or vertical continuous movement. In this case, the stage speed is 1 mm / s for the frame not drawn with the character (a) and 20 mm / s for the frame drawn with the character, and the drawing time equivalent to the above case can be reduced. By appropriately grouping the drawing data in this way, the number of drawing data can be reduced and confusion can be avoided.

In the embodiment described in detail above, FIG.
It is also possible to use the three drawing data for three independent pattern forming steps and draw (1), (2), and (3) using different drawing devices. In this case, FIG.
(A), (b), and (c), a pattern can be formed by a drawing apparatus of a drawing method and a drawing condition corresponding to each of the regions. This can prevent an increase in drawing time caused by the above. Further, depending on the pattern design rule, an optical stepper can be further used in a part of the process of not drawing with a character. 14A and 14B may be regarded as two steps.

As described above, according to the method of the present embodiment, it is possible to maximize the speed of electron beam drawing by the character projection system, and it is possible to greatly reduce the time required for pattern formation.

In the case of a pattern having a size that cannot be resolved without using an electron beam, if the pattern is divided into a repetitive area and a non-repeated area, the repetitive area is continuously projected in the horizontal direction of the stage by using character projection. Drawing is performed by movement, and in an area where no repetition is made, a part of the area is drawn by step-and-repeat or by a continuously variable movable beam in the vertical direction, and a part is drawn by continuous horizontal movement of the stage. As a result, the throughput can be greatly improved as compared with the conventional case where the drawing is performed only by the continuous movement of the stage.

If the above-mentioned non-repeated area has a size that can be resolved by light, the time for pattern formation can be reduced by transferring the area using an optical stepper. In other words, conventionally, if the pattern to be formed includes a size that cannot be resolved by light, it has traditionally been drawn with an electron beam. By using electron beam drawing by character projection in a repetitive pattern area with a small design rule in an area with a large rule, it is possible to greatly improve throughput.

Next, another embodiment of the present invention will be described. As the apparatus, an electron beam lithography apparatus having the configuration shown in FIG. 4 was used as in the previous embodiment. However, in the present embodiment, various aperture masks can be selected by the variable shaped beam size control circuit unit 35. Also, the masks 27b, 27
The shape of the aperture mask formed in c was the same as the rectangular aperture shown in FIG. 5A and the character projection aperture shown in FIG. 5B. Here, FIG.
The shape shown in (b) uses a normal variable shaped beam,
As shown in FIG. 18, the shot is divided into 19 shots. Therefore, by using the character aperture as shown in FIG. 5B, a speedup of 19 times can be realized.

Next, a method of calculating the optimum dose in this embodiment will be described. The apparatus used in this embodiment can control the irradiation amount by changing the irradiation time. The accelerating voltage of the device is 50 kV. In this case, the spread of the backscattered electrons (σ value when the backscattering distribution is represented by a Gaussian distribution) is about 10 μm. In the chip 60 of FIG. 19, an area 61 is an area of a repetitive pattern that can be drawn by the character projection method, and an area 62 is an area without repetition of drawing with a normal variable shaped beam. FIG. 2 shows the area 61 of the repeating pattern.
An aperture having a character shape as shown in FIG.

The aperture shape shown in FIG. 20 has a size of 6 μm square on the sample surface (240 μm square on the aperture). The character shape in FIG. 21 is obtained by dividing the character in FIG. 20 into small pieces, and has a size of 1.5 μm on the sample surface.
m □ (60 μm □ on the aperture). The size of the character shape on the sample surface in FIG. 20 is not negligible compared with the spread of the backscatter, but the size of the character shape on the sample surface in FIG. 21 is sufficiently smaller than the spread of the backscatter. . The character shape in FIG. 22 is a shape obtained by appropriately connecting the character shapes in FIG. 20 to 22 indicate the numbers for character selection. Based on this number, the control circuit of the drawing apparatus determines which character shape to use, the positioning is performed on the aperture where the character shape is formed by the shaping deflection circuit, and the beam is deflected to the position by the shaping deflector. .

The drawing data including the shape, position, irradiation time and the like of the character shot is created by the data conversion computer 38. The design data created by the CAD system 39 enters the data conversion computer 38, where it is converted into drawing data. The repetition pattern has the shape of the smallest unit figure smaller than the maximum beam size according to the use of the electron optical system used. That is, the character shape is defined by the character selection number, position, and arrangement information.

In the present embodiment, the character shape is defined as shown in FIG. 20. When the proximity effect correction is performed, the apparatus of the present embodiment (acceleration voltage 50 kV, spread of backscattering 10 μm: Si) is used. The shape shown in FIG. 20 has a size that cannot be ignored as compared with the spread of backscattering. Therefore, in order to create data subjected to proximity effect correction, that is, data in which the optimum irradiation time is defined for each shot, in the region of the repetitive pattern in FIG. 19 as intermediate data,
Data assumed to be drawn using the character shape of FIG. 21 instead of FIG. 20 is used. An optimum irradiation time is obtained for each shot or each element figure in the chip.

As an algorithm for obtaining the optimum irradiation time, a method using a matrix (M. Parikh, J. Appl. Phys, 19 p437)
1,4378,4389 (1979)), a method using an approximate formula (JMPav
kovich, J. Vac.Sci.Technol.B4 p195 (1986), T. Abe, K.
Koyama, R. Yoshikawa and T. Takigawa, Proceedings of
1st Micro Process Conference (1988) p40) can be used. At this time, as the reference graphic, the original graphic data may be used as it is, or a representative graphic (T.Abe, SY
amasaki, R. Yoshikawa and T. Takigawa, Jpn.J. Appl. 3
0,3B (1991) L528).

FIG. 23 shows the result of obtaining the optimum dose for the area of the repetitive pattern as the intermediate data. The area separated by the solid line indicates the size when the character shape of FIG. 20 is projected on the sample surface, and the area separated by the dotted line indicates the size when the character shape of FIG. 21 is projected on the sample surface. Show. Here, since the set irradiation time is uniform at the center of the repetitive pattern,
The irradiation time set for the character shape of m □ is reset to the irradiation time for the character of 6 μm □. Further, in an area where the irradiation time is uniform even in the peripheral area, the irradiation time is reset by using the character shape of FIG.

FIG. 24 shows the irradiation time as the final drawing data reset for each character shot in the repeated pattern area. The solid line area in FIG. 24 indicates a character shot, a numerical value indicates an irradiation time, and a numerical value surrounded by a circle indicates a character selection number.

The drawing data defining the optimum character shape size and the optimum irradiation amount created as described above are input to the control computer 37 and stored in the buffer memory 36. Then, in accordance with the character selection number and the irradiation time, the shaping deflector 24 in the variable shaping beam size control circuit 35 and the blanking plate 2 in the blanking control circuit 34 are used.
By controlling the deflectors 25 and 26 by the deflection control circuit unit 33 according to the character shape irradiation position by controlling the character 7a, drawing is performed with a desired beam shape, irradiation position, and irradiation time.

By drawing as described above, the character size can be made sufficiently smaller than the spread of the backscattered electrons, or the entire region can be formed with a normal variable shaped beam having a beam size sufficiently smaller than the spread of the backscattered electrons. , And sufficient correction accuracy can be obtained.

Further, in the above embodiment, it may be assumed that in the process of obtaining the optimum irradiation time, the entire area of the repetitive pattern is drawn with the variable shaped beam. At this time, the maximum size of each shot or each elemental figure is sufficiently smaller than the spread of the backscatter. According to the irradiation time set for each shot or each element figure, each shot or each element figure is 1.5 μm □ or 6 μm □.
Reset to character shot. Therefore, in the area of the repetitive pattern, drawing is performed with a variable shaped beam, a character beam having a size of 1.5 μm, and a character beam having a size of 6 μm square according to the distribution of the irradiation time that is set. In this way, sufficient correction accuracy can be obtained even if a character beam having a size that cannot be ignored compared with the spread of backscattering is used.

Also, as shown in FIG. 25, the character shape corresponding to FIGS. 21 and 22 can be projected on the sample surface by superimposing the two shaping apertures, whereby an effect equivalent to that described above is obtained. It is also possible. In this case, the first formed aperture image formed into a rectangle for each shot by the character selection number in FIG.
This can be performed by changing the projection position of the shaping aperture on the character shape shown in FIG. However, in some cases, the character shape as shown in FIGS. 21 and 22 may not be completely created by this method alone. In this case, the character shape is appropriately used in combination with the above embodiment.

The present invention is not limited to the embodiment described above. In the embodiment, the electron beam is used when drawing by the character projection method, but an ion beam may be used instead. Also, when drawing an area that cannot be drawn by the character injection method,
It is also possible to use a charge beam and an optical stepper together. In addition, various modifications can be made without departing from the scope of the present invention.

[0059]

As described above in detail, according to the present invention, the entire drawing area is divided into a repetitive pattern area that can be drawn by the character projection method and an area that cannot be drawn by the character projection method. By drawing separately, the advantage of the character projection method can be maximized and the drawing time can be reduced.

Further, according to the present invention, the smallest unit figure constituting the area of the repetitive pattern is a character having a size that cannot be ignored as compared with the spread of the backscatter of the charged beam, and sufficiently smaller than the spread of the backscatter of the charged beam. By drawing together with a character and a variable shaped beam whose maximum size is sufficiently smaller than the spread of the backscatter of the charged beam, it is possible to sufficiently correct the proximity effect and realize high-speed charged beam drawing Becomes

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of chip data;

FIG. 2 is a schematic diagram showing a state in which chip data is divided into frames;

FIG. 3 is a schematic diagram showing a state in which chip data is divided into blocks;

FIG. 4 is a schematic configuration diagram showing an electron beam drawing apparatus used in the method of one embodiment of the present invention;

FIG. 5 is a plan view showing an aperture shape;

FIG. 6 is a schematic diagram showing a chip image and a drawing direction;

FIG. 7 is a schematic diagram showing an image of chips arranged on a wafer;

FIG. 8 is a schematic diagram showing a configuration of a repeating pattern in a chip;

FIG. 9 is a schematic diagram illustrating an example of conversion of drawing data in the present embodiment;

FIG. 10 is a schematic diagram showing an image of each chip data of FIG. 7 used in the present embodiment;

FIG. 11 is a schematic diagram showing a drawing method procedure in the present embodiment;

FIG. 12 is a schematic view showing steps in a case where optical transfer and EB drawing are used in combination in the present embodiment;

FIG. 13 is a schematic diagram showing a drawing method procedure in the present embodiment;

FIG. 14 is a schematic diagram showing an image of drawing data obtained by modifying FIG. 10 in the present embodiment;

FIG. 15 is a diagram illustrating a relationship between a character shape size on a sample surface and a proximity effect correction error;

FIG. 16 is a diagram showing an energy distribution accumulated in a resist when the size on the sample surface in the region of the repetitive pattern cannot be ignored compared with the spread of backscattering;

FIG. 17 is a diagram showing an area that can be drawn by a large character and an area that can be drawn by a small character.

FIG. 18 is a view showing an image obtained by dividing shots when drawing the shape of FIG. 5B with a variable shaped beam;

FIG. 19 is a diagram showing an overall image of a chip drawn by a method according to another embodiment of the present invention;

FIG. 20 is a diagram showing a character shape of a minimum unit of repetition;

FIG. 21 is a diagram showing a character shape obtained by dividing the minimum unit of repetition such that the size on the sample surface is sufficiently smaller than the spread of backscattering of electrons;

FIG. 22 is a diagram showing a character shape obtained by appropriately combining FIG. 21;

FIG. 23 is a diagram showing an optimum irradiation amount obtained on the assumption that drawing is performed using the character shape of FIG. 20;

FIG. 24 is a diagram showing the optimal dose and the character shape redefined.

FIG. 25 is a diagram showing a state where the projected size of the character shape is changed by two aperture masks.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Repeated pattern area, 2 ... Repeated pattern area, 3 ... Frame, 4 ... Wafer (or mask), 5 ... Chip, 6 ... Subfield, 10 ... Sample chamber, 11 ... Target (sample), 12 ... Sample stand Reference numeral 20: electron optical column, 21: electron gun, 22a to 22e: various lens systems, 23 to 26: various deflection systems, 27: aperture mask, 31: drive circuit unit, 32: laser measurement system, 33: deflection Control circuit part, 34 ... Blanking control circuit part, 35 ... Variable shaping beam size control circuit part, 36 ... Buffer memory and control circuit, 37 ... Control computer, 38 ... Data conversion computer, 39 ... CAD system, 51 ... Substrate , 52 ... resist.

Continuation of front page (72) Inventor Toshio Yamaguchi 1 Toshiba, Komukai Toshiba-cho, Saisaki-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-62-114221 (JP, A) (58) Investigated Field (Int.Cl. ⁷ , DB name) H01L 21/027

Claims (5)

(57) [Claims] When a desired pattern is drawn by irradiating a charged beam onto the sample while continuously moving a stage on which the sample is mounted, a minimum unit or a minimum unit of the repeated pattern is set in a region of the repeated pattern. In a pattern forming method of drawing by a character projection method in which a combination is drawn by one irradiation, and in a non-repetitive pattern area, a pattern is divided into basic unit figures and drawn by a variable shaped beam method in which the pattern is drawn by a basic unit figure, A region where a repetitive pattern in which the entire drawing region on the sample can be drawn by the character projection method is present,
A region in which a repetitive pattern does not exist to be drawn by the variable shaped beam method is divided in advance, and a region of a repetitive pattern is drawn by the character projection method, and a region without a repetitive pattern is drawn by the variable shaped beam method. In some cases, drawing is performed by changing the moving speed of the stage, and the drawable area when drawing an area without a repetitive pattern by the variable shaped beam method does not overlap with an area where the repetitive pattern exists. A pattern forming method comprising controlling a moving direction of a stage. 2. A pattern forming method according to claim 1, wherein a part of a region where no repetitive pattern exists is transferred by an optical stepper, and the rest is drawn by a charged beam. 3. When a desired pattern is drawn by irradiating a charged beam onto the sample while continuously moving a stage on which the sample is mounted, a minimum unit or a minimum unit of the repeated pattern is set in a region of the repeated pattern. In a pattern forming method of drawing by a character projection method in which a combination is drawn by one irradiation, and in a non-repetitive pattern area, a pattern is divided into basic unit figures and drawn by a variable shaped beam method in which the pattern is drawn by a basic unit figure, A region where a repetitive pattern in which the entire drawing region on the sample can be drawn by the character projection method is present,
An area in which a repetitive pattern to be drawn by the variable shaped beam method does not exist is divided in advance, and the divided areas are respectively drawn by a character projection method using only a charged beam,
Separate from the area to be drawn by other than the character projection method, draw each area in an independent process, and draw at different stage movement speeds in each drawing process
And the character projection method
When drawing outside, the drawable area is
Does not include the area to be drawn only by the projection method
Controlling the direction of movement of the stage . 4. The pattern forming method according to claim 3, wherein the same or different drawing apparatus or exposure apparatus is used in the independent steps. 5. A region of a repetitive pattern which can be drawn by the character projection method on the sample is divided into a region where the influence of the proximity effect is uniform and a region where the influence of the proximity effect is not uniform, so that the influence of the proximity effect is uniform. In an area where the pattern is large, a large character beam corresponding to a figure that is at least the minimum unit of the repetitive pattern is used. In an area where the effect of the proximity effect is not uniform, the figure that is the minimum unit is divided into two or more shapes. Correspondingly, writing using a small character beam whose size on the sample surface is smaller than the spread of backscatter, or a variable shaped beam with the maximum beam size whose size on the sample surface is smaller than the spread of backscatter is considered. 4. The pattern forming method according to claim 1, wherein: