JPH01175737A - Charged beam lithography - Google Patents

Abstract

PURPOSE:To suppress the degradation of the pattern accuracy even if the pattern includes an oblique side with an angle other than 45 deg. and improve the pattern accuracy and, moreover, reduce the time for lithography by a method wherein the pattern is divided by a specific process and lithographed by rectangular and triangular beams which can be formed by overlapping apertures. CONSTITUTION:A pattern to be lithographed is divided into basic patterns including rectangles and trapezoids. The basic pattern including an oblique side for an X-direction and a Y-direction is divided into rectangles and right- angled triangles by lines parallel to the X-direction or Y-direction. A right- angled triangle whose X side length and Y side length are different from each other among the right-angled triangles is divided into narrow trapezoids parallel to the longer side by lines parallel to the direction of the longer side of the X-direction or the Y-direction. Each trapezoid 47 is divided into a rectangle and a right-angled triangle. The rectangle and the right-angled triangle are lithographed by making them correspond to lithograph basic patterns of rectangular and triangular beams 46 which can be formed by overlapping at least two beam forming apertures 17 and 18 optoelectronically.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to charged beam drawing for drawing patterns of LSI etc. on samples such as masks and wafers with high speed and high precision. In particular, the present invention relates to a charged beam lithography method that can improve lithography accuracy by improving the lithography method.

(Prior Art) LSI patterns have become increasingly finer and more complex in recent years. A first conventional technique for drawing such a pattern on a sample such as wafer 8 using a charged beam includes, for example, drawing an electron beam using an electron beam having a circular cross section with a diameter of about 172 to 1/4 of the minimum dimension of the pattern. There is a method in which the resist is drawn along the desired pattern. In this method, the pattern to be drawn is sequentially filled with a beam having a minute cross-sectional shape, so the area that can be drawn per unit time is small and the drawing speed is slow.

As a second conventional technique to improve this point, an electron beam drawing method using a variable shaping beam has been developed in recent years. This second prior art, as shown in FIG. By controlling the relative positions of 51 and 52, resist exposure is performed while changing the dimensions of the projection beam image 53 in accordance with the desired pattern shape. In this method, for example, the seventh
In order to expose the pattern shown in Figure 7(a), several dozen exposures were required using a circular beam, but only two exposures were required as shown in Figure 7(b). I'm here.

However, this second conventional technique has a problem in that the exposure time becomes long for patterns including diagonal lines. That is, the diagonal line portion of the pattern as shown in FIG. 8 is divided into sections 54a to 54d154e to 5411 and exposed by rectangular approximation.
A step shape is generated in the diagonal line portion, and the dimensional accuracy of the pattern is reduced.

Therefore, in order to obtain the desired accuracy, it is necessary to increase the number of divisions until the step shape can be ignored, which increases the exposure time.

Therefore, as a third conventional technique, an electron beam lithography method using first and second beam shaping apertures 55 and 56 as shown in FIG.
0-30131).

In this method, the first beam shaping aperture 55 is formed in a rectangular shape, and the second beam shaping aperture 56 is formed on three sides of the rectangular shape parallel to any side of the first beam shaping aperture 55. and four sides of a rhombus shape having an angle of 45° with respect to any of these sides, for a total of seven sides. Then, as shown in FIG. 9(C), a rectangular projection beam image 57 and right triangular projection images 58a to 58d are formed, and as shown at 59.60a to 60d in FIG. It is possible to draw a pattern similar to the above with a small number of exposures and without impairing the dimensional accuracy of the pattern.

However, this drawing method is shown in 60a to 6 in FIG.
As shown by 0d, if the lengths of the X and Y sides that sandwich the right angle of the triangle are approximately equal, that is, the hypotenuse of the triangle is approximately 45@, pattern formation is possible without impairing the dimensional accuracy of the pattern as described above. Although it is possible, it is difficult to obtain a highly accurate pattern in a short drawing time for a pattern that includes a hypotenuse at an angle other than approximately 45°, and the third conventional technique still needs improvement in this respect. .

(Problems to be Solved by the Invention) The first conventional technique had a problem in that the drawing speed was slow because the pattern to be drawn was sequentially filled in with an electron beam having a circular cross section.

In the second conventional technique, drawing is performed using a rectangular projection beam image, and therefore, it is difficult to draw a highly accurate pattern in a short time for a pattern including diagonal lines. Furthermore, the third conventional technique is capable of drawing a pattern having an oblique side of 45° in a short time without impairing the dimensional accuracy of the pattern.
For patterns including hypotenuses other than 5°, it is difficult to obtain highly accurate patterns in a short drawing time, and improvements in this respect have been desired.

This invention was made based on the above circumstances, and approximately 45
It is an object of the present invention to provide a charged beam drawing method that can suppress deterioration in pattern accuracy, improve pattern accuracy, and shorten drawing time even for patterns including oblique sides other than °. do.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention includes a first step of dividing the pattern to be drawn into basic figures including rectangles and trapezoids, A second step of dividing the basic figure including the hatched part in the Y direction by line segments parallel to the X direction or the Y direction to form a collection of rectangles and right triangles; For a right triangle with different side lengths in the Y direction, divide it by a line segment parallel to the larger side in the X direction or BY force direction, and create a vertically elongated trapezoid figure group along the parallel line segment. and a third step of further dividing each of the trapezoidal figures into rectangles and right triangles; The gist is to process the rectangles and right triangles divided in step I3 so as to correspond to drawing unit figures of rectangular and triangular beams that can be formed by electro-optical overlapping of at least two beam shaping apertures.

(Operation) Of the basic figures obtained by dividing the pattern to be drawn, the basic figure including the diagonal line portion is divided by line segments parallel to the X direction or the Y direction to form a collection of rectangles and right triangles. Among these right triangles, a right triangle with different lengths of sides in the X direction and sides in the Y direction is difficult to form with a drawing unit figure obtained by electro-optical overlapping of at least two beam shaping apertures. is divided by line segments parallel to the large side in the X direction or the Y direction to form a group of vertically elongated trapezoidal figures. Next, each of these trapezoidal figures is further divided into rectangles and triangles, and then the above-mentioned drawing unit figure is associated with each of the rectangles and triangles, and drawing processing is performed. As a result, deterioration in pattern accuracy is suppressed, and high-speed and highly accurate pattern formation is possible with a small number of drawing unit figures.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 5. This embodiment is applied to an LSI pattern drawing method using an electron beam.

First, this fruit! To explain from the electron beam drawing apparatus applied to Example II, 1 in FIG. 1 is a sample chamber, and this sample chamber 1 houses a table 3 on which a sample 2 such as a semiconductor wafer is placed. . The table 3 is driven by a table driving circuit 4 in the X direction (left and right directions on the page) and the Y direction (front and back directions on the page). The moving position of the table 3 is measured by a position circuit 5 using a laser length meter or the like.

An electron beam optical system 10 is arranged above the sample chamber 1. This optical system 10 includes an electron gun 6, various lenses 7.8
．． 9.11.12, blanking deflector 13, beam dimension variable deflector 14, beam scanning main deflector 15,
It is composed of a sub-deflector 16 for beam scanning, two beam shaping apertures 17 and 18, and the like. The two beam shaping apertures 17 and 18 are shown in FIG. 9(a).
, a beam-shaping aperture shown in (b), respectively;
They are formed in the same shape.

Then, the main deflector 15 positions a predetermined sub-deflection area (subfield), the sub-deflector 16 positions the figure drawing position within the sub-field, and the beam size variable deflector 14 and beam shaping The beam shape is controlled by the apertures 17 and 18, and the table 3
The process is to draw a subfield while moving continuously in one direction.

When the drawing of one subfield is completed in this way, the drawing of the next subfield is started.

Furthermore, when drawing of a frame, which is a set of multiple subfields, is completed, the table 3 is moved stepwise in a direction perpendicular to the direction of continuous movement, and the above process is repeated to sequentially draw each frame area. . here,
A frame is a rectangular drawing area determined by the deflection width of the main deflector 15, and a subfield is a unit drawing area determined by the deflection width of the sub-deflector 16.

On the other hand, the controller sieve machine 20 has a magnetic disk (storage medium) 2.
1 is connected to the magnetic disk 21, and LSI chip data is stored in this magnetic disk 21.

Chip data read from the magnetic disk 21 is stored in a pattern memory (data buffer) 22 for each frame area.
temporarily stored in . The pattern data for each frame area stored in the data buffer 7 section 22, that is, the frame information consisting of the drawing position, drawing figure data, etc., is analyzed by the pattern data decoder 23 and the drawing decoder 24, which are data analysis sections. ranking circuit 25,
It is sent to a beamformer driver 26, a main deflector driver 27 and a sub deflector driver 28.

That is, the pattern data decoder 23 creates blanking data based on the above data, and sends this data to the blanking circuit 25.

Additionally, desired beam size data is generated and sent to the beamformer driver 26. Then, from the beam shaper driver 26 to the optical system 1
A predetermined deflection signal is applied to the beam size variable deflector 14 of No. 0, thereby controlling the size of the electron beam.

Furthermore, the drawing data decoder 24 creates subfield positioning data based on the above data, and sends this data to the main deflector driver 27. Then, a predetermined signal is applied from the main deflector driver 27 to the main deflector 15 of the electron optical system 20, whereby the electron beam is deflected and scanned to a designated subfield position. moreover,
The drawing data decoder 24 generates a control signal for scanning the sub-deflector, and this signal is sent to the sub-deflector driver 28. Then, a predetermined sub-deflection signal is applied from the sub-deflector driver 28 to the sub-deflector 16, so that drawing is performed for each sub-field.

Next, an explanation will be given of an electron beam drawing method for an LSI pattern, which is a pattern to be drawn, using the electron beam drawing apparatus configured as described above.

FIG. 2 first shows the process of generating data for performing drawing processing. The LSI pattern is designed by a CAD system, and the design pattern data is converted into drawing data by a host computer. Then, this writing data is read out and electron beam writing is performed. Here, the data designed by the CAD system is usually composed of several polygons, and has a data system in which patterns overlap.

In order to make this type of LSI data acceptable for an electron beam lithography system, a host computer performs graphic contouring processing to remove multiple beam exposure areas. Subsequently, a subfield area 30 as shown in FIG.
Furthermore, the polygon included in the subfield region 30 is divided by straight lines parallel to the Y axis (up and down direction in the paper) to form basic figures 31 and 32 composed of rectangles and trapezoids.
．． Divide into 33.34.35.36.

Based on the basic figure obtained in the above steps, cell data as shown in FIG. 4(a) is constructed. That is, the above basic figure is
As shown in Figure (b), the shape of the figure is 41
Beam irradiation m42, figure position l indicating the beam irradiation position!
As a collection of drawing figure information consisting of 43 and figure size 44, cell data representing the drawing pattern and data related to the subfield area is constructed as shown in FIG. 4(a).

Then, frame information is generated as a collection of the drawing figure information, furthermore, LSI chip data is constructed as a collection of frame information, and this chip data is supplied to the magnetic disk 21 via the control computer 20 for drawing processing. will be carried out.

In this drawing process, frame information is temporarily stored in the pattern memory 22 for each frame area, the basic figure is decoded by the pattern data decoder 23, and two 7-bar beam forming beam forming means are used. 1717.
18, the figure is divided into a group of drawing unit figures that can be formed.

At this time, figures 32 and 3 to which the figure type 41 in the drawn figure information does not indicate a rectangle that does not include a hypotenuse and are given an index.
5, the figure is divided as shown in FIG. 5(b) as a collection of rectangular drawing unit figures 45 that can be formed by a combination of two beam forming apertures 17 and 18 as shown in FIG. 5(a). and use it for drawing.

Next, the figure 31 to which an index indicating an oblique rectangle is given among the figures including the oblique side is divided into trapezoids 37 and 38 in a broad sense as shown in FIG. 5(C).・And shapes 33, 34, and 36 with an index indicating a trapezoid
At the same time, the figure is divided into rectangles and right triangles by straight lines parallel to the X-axis (in the left-right direction on the paper) passing through the vertices of the figure, resulting in a figure system as shown in FIG. 5(d). Among this group of figures, the rectangular shapes 33b, 34b and 36b are shown in FIG. 5(b).
In the same manner as above, the rectangle is divided into the drawing unit figures 45, and among the right triangle figures, the figures 37a, 137b, 38a, and 38b, in which the lengths of the X side and the Y side that sandwich the right angle are approximately equal, are Rectangular drawing ψ position figure 45 shown in Figure 5 (a)
and four types of right-angled isosceles triangles 46a to 46 whose hypotenuses have different inclination directions as shown in FIG. 5(e).
D is divided into figures and used for drawing.

Then, right triangles 33a, 33c, 34a, and 36a, which have different lengths on the X and Y sides that sandwich the undrawn right angle, are approximated and drawn using the drawing unit figures 45, 468 to 46d only. In this case, as shown in FIG. 5(f), the figure is divided so that the division width becomes the maximum width of the drawing unit figure by a straight line parallel to the larger side of the X side or the Y side, and the vertically elongated trapezoid 478~ 47e is the figure group. Furthermore, these trapezoids 47a to 47e are divided into rectangles and right triangles, the rectangles are subjected to drawing processing using a rectangular drawing unit figure 45, and the remaining right triangle portions are divided into triangular beams 46a to 46d having four types of directions and the direction of the rectangles. The matched beams are selectively extracted and graphically approximated as shown in FIG. 5(g), and expressed as a collection of drawing unit graphics as shown in FIG. 5(h). Then, by controlling the beam shaper driver 26 to perform a drawing process based on this drawing unit figure, it becomes possible to form a highly accurate LSI pattern.

Thus, according to the method of this embodiment, when drawing a figure that includes an oblique side other than approximately 45°, which cannot be formed by overlapping two beam shaping apertures 17 and 18, the number of drawing unit figures increases. The accuracy of the drawn pattern to be formed can be greatly improved without any problems.

It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.

For example, in the above embodiment, the pattern data decoder performs the step of supplying the basic figure to the magnetic disk and dividing the basic figure into drawing unit figures, but the host computer performs the same process as the above processing step. After dividing into drawing unit figures, the data may be supplied to a magnetic disk for drawing. Furthermore, the configuration of the electron beam lithography apparatus is not limited to that shown in FIG. 1, and can be modified as appropriate.

Further, in the above embodiments, the drawing method using an electron beam has been described as an example, but the charged beam is not limited to the electron beam, and charged beams including ion beams are also applicable. In addition, regarding the writing method, it is possible to use a two-stage deflection method that combines main and sub-deflection, or a single-stage deflection method, and it is also possible to apply a step-and-repeat method in addition to a continuous table movement method. The shape of the aperture is not limited to that of the above embodiment, and can be modified as appropriate.

[Effects of the Invention] As explained above, according to the present invention, among the basic figures obtained by dividing the pattern to be drawn, the basic figure including the diagonal line part is divided by line segments parallel to the X direction or the Y direction. υJ to form a collection of rectangles and right triangles, and among these right triangles, angles other than approximately 45°, which are difficult to form with the drawing unit figure obtained by electro-optical molding of at least two beam shaping apertures, are defined as υJ. For a right triangle that includes a hypotenuse, divide the right triangle by a line segment parallel to the larger side of the two sides sandwiching the right angle to form a group of vertically elongated trapezoids, and each of these trapezoids can be further divided into a rectangle and a right triangle. After dividing into
Since this is approximated by the drawing unit figure, it is possible to suppress a decrease in pattern accuracy and improve pattern accuracy without increasing the number of drawing unit figures, and to shorten the drawing time. There are advantages.

Therefore, the formation of highly accurate LSI patterns, etc. and the LSI
This can significantly contribute to improving productivity.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the charged beam drawing method according to the present invention, FIG. 1 is a configuration diagram showing an example of a drawing apparatus to which it is applied, and FIG. 2 shows a drawing pattern data generation process. FIG. 3 is a schematic diagram showing divided basic figures; FIG. 4 is a schematic diagram for explaining the structure of drawing data; FIG. 5 is a process diagram for explaining the process of dividing figures; FIG. 6 is a schematic diagram showing a rectangular aperture in the second conventional example, FIG. 7 is a diagram showing a drawing pattern according to the second conventional example, and FIG. 8 explains problems in the second conventional example. FIG. 9 is a schematic diagram showing a beam shaping aperture in the third conventional example, and FIG. 10 is a diagram showing a drawing pattern according to the third conventional example. 17.18: Beam forming aperture, 31-36: Basic figure, 45: Rectangular drawing unit figure, 468-46d: Drawing unit figure consisting of four types of right-angled isosceles triangles, 478-47e: Vertically elongated trapezoidal figure.

Claims (2)

[Claims] (1) A first step of dividing the pattern to be drawn into basic figures including rectangles and trapezoids, and dividing the basic figures including hatched parts in the X direction and Y direction by line segments parallel to the X direction or Y direction. The second step is to form a collection of rectangles and right triangles, and for right triangles whose sides in the X direction and the side in the Y direction are different in length, a third step of dividing the trapezoids by line segments parallel to the sides thereof to form a group of vertically elongated trapezoids along the parallel line segments, and further dividing each of the trapezoids into rectangles and right triangles. , the rectangles and right triangles divided in the first to third steps are subjected to drawing processing in correspondence with drawing unit figures of rectangular and triangular beams that can be formed by electro-optical overlapping of at least two beam shaping apertures. A charged beam drawing method characterized by: (2) The triangular beams formed by electro-optical overlapping of the two beam shaping apertures are four types of right-angled isosceles triangles each having a hypotenuse in a different direction of inclination. The charged beam writing method according to scope 1.