JPH03195012A - Method for charged particle beam drawing - Google Patents

Abstract

PURPOSE:To measure a dislocation both in the continuous movement direction and in the stepwise movement direction of a table by a method wherein a boundary pattern between frame regions is improved. CONSTITUTION:A boundary 17 between adjacent frame regions is set to be a wavy shape in such a way that auxiliary deflection regions 15 at end parts of adjacent frame regions 16 enter alternately. As a table is moved in the Y- direction from a frame 161, the auxiliary deflection regions 15 are drawn sequentially. When a drawing operation of the frame 161 is finished, the table is moved stepwise in the X-direction, and is moved continuously in the opposite direction; a drawing operation of a frame 162 is started. Consequently, it is possible to obtain patterns constituted so as to be adjacent to the auxiliary deflection regions of other frames at the boundary 17 both in parallel with the continuous movement direction of the table and in parallel with the stepwise movement direction of the table. Thereby, a dislocation of the frames in two directions can be evaluated simultaneously.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a charged beam lithography method, and particularly to a charged beam lithography method for writing an evaluation pattern for evaluating positional deviation of a pattern to be drawn. Regarding the method.

(Prior Art) In recent years, with the progress of semiconductor technology, the need for miniaturization of LSI patterns has increased, and patterns with increasingly high precision have been required. Electron beam lithography is attracting attention as the most effective method for forming such minute devices, and methods using variable shaped beams (VSB) are increasingly being adopted to improve throughput. .

The variable shaping beam is 1. Until now, rectangular beams have been the mainstream, but recently triangular beams have begun to be used to draw patterns including diagonal lines at high speed and with high precision. In a writing device using such a variable shaped beam,
Generally, a double deflection system is used in which a main deflection means and a sub deflection means are combined. That is, the LSI chip pattern is divided into frames, which are regions determined by the main deflection width, and this frame region is further divided into sub-deflection regions, which are a plurality of minute regions, and the position of the sub-deflection regions is controlled by the main deflection means. In this method, the process of sequentially drawing a desired pattern with a shaped beam using a sub-deflection means is repeated, thereby drawing a pattern in the entire desired area.

Furthermore, in order to improve throughput, not only the double deflection method but also electron beam lithography systems generally use a method of drawing a pattern while continuously moving a table on which a sample is placed in one predetermined direction (Y direction). is taking. That is, one continuous movement of the table in the Y direction draws a frame-width area on the chip, then the table is moved stepwise in the X direction by the frame width, and then continuously moved in the opposite direction (-Y direction). This method draws adjacent frames while

For this reason, table movement correction is performed to correct the beam position in accordance with table movement.

By the way, in the above-described drawing method, there are two types of positional deviation errors of the drawing pattern: (1) deviation between sub-deflection areas; and (2) deviation between frame areas. In particular, ■ is larger than ■ because it also includes deviations due to table movement correction errors, and the pattern accuracy is approximately determined by ■. Therefore, in order to perform table movement correction, a technique for determining IJ with high accuracy is required.

Conventionally, the method of measuring this shift between frame areas is to draw a main scale in one frame area and a vernier scale in the other frame area, touching the boundary line (line in the Y direction) between adjacent frame areas. A method has been used in which a vernier pattern is formed at the boundary between these two frame areas and the deviation of the vernier pattern is measured.

However, this type of method has the following problems. In other words, since the border of the frame area is a straight line and the vernier pattern is formed linearly along the line in the continuous table movement direction (Y direction), it is possible to measure the deviation in the Y direction, but it is possible to measure the deviation in the Y direction. Displacement in the direction (X direction) cannot be measured. Furthermore, since such a vernier pattern is formed only of rectangles, it is possible to determine the positional deviation of a pattern drawn with a rectangular beam, but it has not been possible to evaluate the positional deviation of a triangular beam whose control is more complicated.

(Problem to be Solved by the Invention) In this way, with the conventional drawing method, even if an evaluation pattern is drawn, it is possible to measure the pattern positional deviation in the direction of continuous table movement, but it is not possible to measure the pattern positional deviation in the direction perpendicular to it. It is difficult to do so, and there are limits to the evaluation of deviations in drawn patterns. Furthermore, the above-mentioned problem is not limited to electron beam lithography, but also applies to ion beam lithography.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to simultaneously measure not only pattern positional deviation in the direction of continuous table movement, but also pattern positional deviation in the direction perpendicular thereto. An object of the present invention is to provide a charged beam drawing method that can improve the accuracy of evaluating deviations in drawn patterns.

[Structure of the Invention (Means for Solving the Problems)] The gist of the present invention is to improve the boundary pattern between frame regions to provide an evaluation device that can measure positional deviation in both the direction of continuous table movement and the direction of step movement. It consists in drawing patterns.

That is, the present invention provides a charged beam drawing method in which a table on which a sample is placed is continuously moved in one direction, and a beam is positioned and controlled by a combination of a main deflection means and a sub-deflection means to draw a desired pattern on a sample. The unit drawing area drawn by the sub-deflection means with the deflection position fixed by the deflection means is called the sub-deflection area, and the area which is a set of sub-deflection areas and drawn by one continuous movement of the table is called the frame area. When drawing an evaluation pattern for measuring the positional deviation of the frame, the boundaries between adjacent frame areas are In this method, a pattern is drawn in each sub-deflection area, in which the pattern is set in a wave shape, and the positional deviation between adjacent sub-deflection areas can be measured.

(Function) In the present invention, since the boundaries of the frame areas are set so that the sub-deflection areas at the ends of the respective frame areas intersect alternately, the sub-deflection areas allow measurement of the positional deviation between adjacent sub-deflection areas. The area unit patterns are adjacent in both the table continuous movement direction and the table step movement direction along the border of the frame area. Therefore, pattern positional deviations in the continuous table movement direction and the table step movement direction can be simultaneously measured from the patterns of the sub-deflection areas adjacent along the border of the frame area. That is, the positional deviation in the step movement direction can be measured from the pattern of the sub-deflection area that is in contact with the boundary of the frame area and adjacent in the table continuous movement direction.

Furthermore, the positional deviation in the continuous movement direction can be measured from the pattern of the sub-deflection area that is in contact with the boundary of the frame area and adjacent in the step movement direction.

In addition, as a pattern in which the positional deviation of the sub-deflection area can be measured, a rectangular pattern group using only rectangular beams and a diagonal line pattern group using only triangular beams are drawn in the same sub-deflection area. It becomes possible to simultaneously evaluate the positional deviation of the pattern drawn with the triangular beam.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 8 is a schematic diagram showing the structure of an electron beam lithography system used in a method according to an embodiment of the present invention. In the figure, 60 is a sample chamber, and a sample stage 62 on which a sample 61 such as a semiconductor wafer is placed is accommodated in this sample chamber 6o. The sample stage 62 is
The sample stage drive circuit 72 receives commands from the computer 71 to move in the X direction (left/right direction on the page) and Y direction (front/back direction on the page).
will be moved to The position of the sample stage 62 is measured by a laser length measurement system 73, and the calculation results are sent to the computer 71 and the deflection control circuit 76.

On the other hand, above the sample chamber 60, an electron gun 81. - An electron optical lens barrel 80 is provided, which includes various lenses 82a to 82e, various deflectors 83 to 86°, first and second molded aperture masks 87, 88, and the like.

Here, the deflector 83 is a blanking deflection plate for turning the beam on and off, and a blanking signal from the blanking control circuit 74 is applied to this deflection plate.

The deflector 84 is a deflector for variably controlling the dimensions of the beam by utilizing the optical overlap between the aperture image of the first shaping aperture mask 87 and the aperture of the second shaping aperture mask 88. A deflection signal is applied to the device from a variable beam size control circuit 75. Further, the main deflector 85 and the sub-deflector 86 are beam scanning deflectors that scan the beam on the sample 61, and these deflectors 85, 86
A deflection signal is applied from a deflection control circuit 76 to.

Next, a method of generating rectangular and triangular beams using the above device will be explained.

FIG. 9 is a diagram showing the shapes of the first forming aperture image and the second forming aperture. Rectangular first molded aperture image 9
1 is deflected by a deflector 84 and irradiated onto a second forming aperture 92 which is a combination of large and small rectangular patterns. By changing the irradiation position, a rectangular beam and a triangular beam are generated. Furthermore, by moving the beam in the direction indicated by the arrow in FIG. 9(a), it is possible to change the dimensions of the beam; and points P1 to P4 are reference positions for generating rectangular beams and triangular beams, respectively, and serve as reference points when simultaneously moving the beams. In this example, FIG. 9(b)
), a rectangular beam 93 and four types of triangular beams 94 to 97 can be generated depending on the positional relationship between the first shaping aperture image 91 and the second shaping aperture 92.

Note that if the beam is irradiated onto the sample as it is, the result shown in Figure 10 (
As shown in a), the triangular beam and the rectangular beam are irradiated at shifted positions. Therefore, the sub-deflector 8
As shown in FIG. 10(b), the reference points P, -P4 of the four types of triangular beams 94 to 97 are set to the reference point P of the rectangular beam 93 on the sample 61. It has been corrected to match. When generating a triangular beam in this way, it is necessary to swing back more precisely than in the case of a rectangular beam.

Next, the shape of the evaluation pattern and the drawing method thereof according to the present invention will be explained.

FIG. 1 is a plan view showing an evaluation pattern used in the method of this embodiment. For example, the main scale 11 and the vernier scale 12 have a line width of 0.
．． 21 scales of 4 μm are arranged in a row. The pitch dimension of the main scale 11 is 1 μm, the pitch dimension of the vernier scale 12 is 1.021 m, and fields A and B
are adjacent to each other at the boundary 13, forming a vernier pattern. Note that the main scale 11 and the vernier scale 12 are drawn using a rectangular beam 14. In a banya pattern with such a configuration, by reading the point where the scales of the main scale 11 and the vernier scale 12 match, a relative positional deviation of 0 to 0.2 μm can be reduced to 0.
．． It can be determined with an accuracy of 0.2 μm.

FIG. 2 shows a pattern for each sub-deflection area.

The sub-deflection area 15 is, for example, a square with one side of 30 μm,
The main scale 11 is placed on one of two sets of opposing sides among the four sides,
A vernier measure 12 is placed on the other side.

By drawing such a pattern for each sub-deflection area within the frame without any gaps, it is possible to simultaneously measure the deviation between the sub-deflection areas in both the X and Y directions, and also determine the distribution of in-plane deviation. be able to.

FIG. 3 shows the shape and drawing method of frame boundaries in this embodiment. As shown in the figure, the adjacent frame area 16
Boundaries 17 between adjacent frame regions are set in a wave shape so that the sub-deflection regions 15 at the ends of each frame region 16 intersect alternately. The figure shows a frame width of 12
This is an example of 0 μm. Note that a mark may be drawn in the sub-deflection area in contact with the boundary 17 together with the evaluation pattern so that the boundary between frames can be easily identified. As marks in Fig. 4, (+) mark 21 and (-) mark 2
2 is used, and FIG. 5 shows an example in which frame number 23 is drawn.

The drawing in this embodiment is the first frame 16. in FIG.
Starting from , as the table moves in the Y direction, the sub-deflection areas 15 are sequentially drawn as shown by the arrows. When the drawing of the first frame 161 is finished, the table is
Then, the table begins to move continuously in the opposite direction, and drawing of the second frame 16□ begins. In this way, drawing is performed while the table is repeatedly and continuously moved in the forward and reverse directions.

By drawing the evaluation pattern as described above,
The vernier pattern formed in contact with the sub-deflection area of another frame at the boundary 17 has both patterns parallel to the table continuous movement direction (Y direction) and parallel to the table step movement direction (X direction). can get. Therefore, it is possible to simultaneously obtain the frame positional deviation in the continuous table movement direction (Y direction) using the vernier pattern of section 18 shown in Figure 3, and the frame positional deviation in the table step movement direction (X direction) using the vernier pattern of section 19. can.

Thus, according to the method of this embodiment, by setting the boundaries 17 of adjacent frame areas 16 in a wave shape as shown in FIG. It becomes possible to simultaneously evaluate the frame positional deviation in two directions (direction). In addition, by drawing an arbitrary mark on the part of the sub-deflection area 15 that is in contact with the boundary 17, the boundary 1 of the frame area 16 can be
It has the advantage of being able to understand 7 at a glance.

Next, as another embodiment of the present invention, an example using a triangular beam will be described.

FIG. 6 shows a configuration diagram of a diagonal vernier pattern drawn using only the triangular beam 24. Similar to the vernier pattern using the rectangular beam 14 in FIG. 1, by shifting the pitch dimension of the main scale 31 and the vernier scale 32, the relative positional deviation between fields A and B can be measured. By arranging such a pattern on each side of the sub-deflection area as shown in FIG. 2, it becomes possible to measure the deviation of the pattern drawn using the triangular beam.

Further, the vernier pattern drawn in the sub-deflection area is not limited to either a rectangular shape or a triangular shape, and both may be drawn. FIG. 7 is an example in which a vernier pattern using only the rectangular beam 14 shown in FIG. 1 and a diagonally shaded vernier pattern using only the triangular beam 24 shown in FIG. 6 are drawn in the same sub-deflection area. . In FIG. 7(a), a vernier pattern using rectangular beams is drawn at the center of the side, and a vernier pattern using triangular beams is drawn at the corners of the side. Furthermore, in FIG. 7(b), a vernier pattern using rectangular beams is drawn at the corner of the side, and a vernier pattern using triangular beams is drawn at the center of the side. With this configuration, it is possible to measure pattern positional deviation using a triangular beam, which has not been possible until now, and at the same time, it is possible to compare pattern positional deviation with a rectangular beam.

Therefore, not only can the same effect as the previous embodiment be obtained, but also the rectangular beam can be drawn by drawing a vernier pattern using only rectangular beams and a vernier pattern using only triangular beams in the same sub-deflection area. This makes it possible to evaluate the difference between the pattern position deviation between the pattern position and the triangular beam, and is extremely promising for testing and evaluation of future electron beam lithography systems.

Note that the present invention is not limited to each of the embodiments described above. The pattern for evaluation is not limited to a vernier pattern, but may be any pattern for each sub-deflection area that allows measurement of positional deviation between adjacent sub-deflection areas. Specifically, it is sufficient that the shapes are arranged at a constant pitch along the boundary of the sub-deflection area, and that adjacent shapes have different pitches. Further, the apparatus used in the present invention is not limited to the same as shown in FIG. 8, but can be modified as appropriate according to specifications. Furthermore, the present invention can be applied not only to electron beam lithography apparatuses but also to ion beam lithography apparatuses. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As explained above, according to the present invention, the boundaries between frame regions are made wave-shaped, and the sub-deflection regions at the ends of the respective frame regions intersect alternately in adjacent frame regions. Therefore, it is possible to simultaneously measure not only the pattern positional deviation in the direction of continuous table movement, but also the pattern positional deviation in the direction perpendicular thereto, and it is possible to improve the evaluation accuracy of the drawing pattern deviation.

[Brief explanation of drawings]

1 to 5 are for explaining a method according to an embodiment of the present invention. FIG. 1 shows a vernier pattern using a rectangular beam, and FIG. 2 shows a vernier pattern arranged in a sub-deflection area. FIG. 3 is a diagram showing the border of the frame area and the drawing method, FIGS. 4 and 5 are diagrams showing marks for boundary identification, and FIGS. 6 and 7 are other examples. This is to explain the method. Fig. 6 shows a diagonal vernier pattern using a triangular beam, and Fig. 7 shows a vernier pattern using a rectangular beam in the sub-deflection area and a vernier pattern using a triangular beam. 8 is a schematic configuration diagram of a charged beam drawing device, FIG. 9 is a diagram showing the positional relationship between the first aperture image and the second aperture, and FIG. 10 is a diagram showing a triangular beam and a rectangular beam. FIG. 3 is a diagram for explaining reference point correction with. 11.31... Main scale, 12.32... Vernier scale, 13... Field boundary, 14... Rectangular beam, 15... Sub-deflection area, 16... Frame area, 17...・Frame boundary, 21.22...mark, 23...number, 24...triangular beam.

Claims (1)

[Scope of Claims] A charged beam drawing method in which a table on which a sample is placed is continuously moved in one direction, and a beam is positioned and controlled by a combination of a main deflection means and a sub-deflection means to draw a desired pattern on a sample, The unit drawing area drawn by the sub-deflection means while the deflection position by the main deflection means is fixed is called the sub-deflection area, and the area which is a set of sub-deflection areas and drawn by one continuous movement of the table is called the frame area. When drawing an evaluation pattern to measure the positional deviation between adjacent frame areas, draw the boundaries between adjacent frame areas so that the sub-deflection areas at the edges of each frame area intersect alternately. A charged beam drawing method characterized by drawing a pattern in each sub-deflection area in a sub-deflection area unit, which is set in a wave shape and in which the positional deviation between adjacent sub-deflection areas can be measured.