JPH0582424A - Electron-beam exposing method - Google Patents

Abstract

PURPOSE:To provide a processing method by which side edges are not drawn in steps, but in smooth lines when a pattern having the side edges which are inclined against the coordinate axes of an orthogonal coordinate system which is parallel to the outer periphery of the square cross section of an electron beam is plotted with the electron beam having the square cross section. CONSTITUTION:A pattern 2 to be formed is irradiated with an electron beam by rotating a substrate so that the linear side edge of the pattern 2 can become parallel to one side of a square shot 1. The deflecting amount of the electron beam which decides the position of the shot 1 is corrected in accordance with the rotation of the substrate and the electron beam irradiating position is set so that the one side of the shot 1 can be aligned with the linear side edge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of selectively irradiating an electron beam in electron beam lithography. In recent years, various types of functional devices have been developed due to advances in submicron fine pattern formation technology and atomic layer unit epitaxial growth technology. In the production of these elements, electron beam lithography is the core of the fine pattern forming technology, but in the drawing process of the electron beam exposure apparatus which is widely used at present, a fixed dose amount is applied to one irradiation point. After irradiating the electron beam, the irradiation aim is changed and the same irradiation is performed on the next irradiation point, and this is repeated to realize a continuous irradiation area. The irradiation point is set so that this continuous irradiation region has a predetermined shape, and this one-time electron beam irradiation process or the irradiation region thereof is called a shot.

The cross-sectional shape of the electron beam used in such processing is often a rectangle (usually a square), which means that the pattern drawn by the above processing has edges parallel to the orthogonal coordinate axes. Is due to the large number. That is, when a pattern in an orthogonal coordinate system is drawn using this type of electron beam, the straight edges of the two are parallel to each other, so that the drawn edges of the pattern have no unnecessary entry and exit.

[0003]

As described above, the conventional electron beam exposure is suitable for drawing a pattern whose outer periphery is parallel to the orthogonal coordinate axes, but the outer periphery of the pattern is inclined with respect to the coordinate axes. If this is the case, inconvenience occurs.
That is, to draw the pattern edge as an inclined line,
The shots are arranged in a diagonal direction, but since the shape of the shots is rectangular, it is not possible to draw such a slanted portion as a smooth line with no entrance or exit. This situation will be described with reference to the drawings.

First, in the case of a pattern parallel to the XY orthogonal coordinate axes, by arranging a square shot 1 as shown in FIG. 4 (a), a smooth linear pattern of the edge can be drawn. However, in the case of the diagonal pattern, the shots are arranged as shown in FIG. 6B, and the drawn pattern becomes a staircase pattern as shown in FIG. The stairs get finer if the distance between the centers of the shots is reduced, but a perfect straight edge cannot be obtained as long as the square shots are arranged diagonally.

The formation of conventional devices did not require that the pattern, even with sloping edges, be perfectly smooth, but in some recently developed functional devices, sloping It is required that the straight line be smooth with an accuracy of about nanometer. Such a tilted line cannot be realized by the conventional electron beam drawing method, and it is necessary to cope with this with a new processing method or apparatus.

As one method of drawing a completely inclined line in electron beam drawing, it is considered that the sectional shape of the electron beam is made into a shape having a side parallel to the inclined line and the inclined line is drawn by using it. .. However, since the inclination angle of the straight line to be drawn is not constant, if this method is used, it is required that the cross-sectional shape of the electron beam can be arbitrarily changed.

A shaped beam exposure apparatus having such a function is also provided, but it is more expensive than a normal type exposure apparatus and the precision of forming a fine pattern is not sufficient. Therefore, if it is possible to draw a pattern having a slanted edge of a smooth line by an ordinary electron beam exposure apparatus that uses a rectangular beam, it will be a great contribution to the practical application of a functional element that requires this.

An object of the present invention is to draw a straight line which is inclined with respect to the coordinate axis by using an electron beam whose outer peripheral line of the cross section is parallel to the orthogonal coordinate axis, and the edge of the straight line can be made a complete straight line. It is to provide an electron beam drawing method.

[0009]

In order to achieve the above object, in the electron beam exposure method of the present invention, a resist applied on the surface of a substrate by irradiating an electron beam having a rectangular cross section perpendicular to the central axis. In the drawing process of exposing, when the exposure area has a linear edge that is not parallel to the side of the rectangle,
The substrate is relatively rotated so that the linear edge of this exposure region is parallel to one side of the square of the electron beam cross section, and the electron beam irradiation position is changed parallel or orthogonal to this linear edge. Perform line exposure.

Deflection data when irradiating an electron beam on a substrate after rotation and data necessary for shifting the electron beam irradiation position in a direction parallel or orthogonal to the linear edge are in the exposure area before the substrate is rotated. It is calculated from the position coordinates and the rotation angle.

[0011]

FIG. 1 is a diagram for explaining the principle of the present invention, and the reason why a pattern having a smooth inclined straight line is formed by the present invention will be described below with reference to this drawing.

As shown in FIG. 1A, consider the case where a linear pattern 2 is formed which is inclined with respect to the orthogonal coordinate axes X and Y set on the substrate. The intersection angle between the central axis of the straight line pattern and the X axis is α. The side of the rectangular cross section of the electron beam is X ',
It is parallel to the coordinate axes of the Y'orthogonal coordinates, and the X ', Y'orthogonal coordinates initially match the X, Y orthogonal coordinates.

When the substrate is rotated clockwise by α from this state, the center line of the linear pattern 2 becomes parallel to the X'axis of the X'and Y'orthogonal coordinates, as shown in FIG. Become. That is, one side of the rectangular section of the electron beam is parallel to the long side of the linear pattern, and by arranging the shots as shown in FIG. 7C, a linear pattern inclined with respect to the X axis can be drawn. There are no step-like irregularities at the edges of this straight line pattern.

[0014]

[Embodiment] In an electron beam exposure apparatus currently in practical use, if the electron beam has a rectangular cross section, one side is 0.1 to 1 μm.
Is the range in which the irradiation position can be changed by the deflection electrode.
The (field) is about 3 mm x 3 mm. On the other hand, the size of the chips arranged in a matrix on the substrate is I
In C, the length is 8 to 10 mm on a side, but since the functional element having the inclined pattern as formed according to the present invention is often formed on a smaller chip at present, the pattern formation area of one chip is one field. To fit in
That is, the embodiment will be described assuming that the cycle of step and repeat matches the cycle of chip arrangement. If the chip size is larger than this, move the substrate in parallel and perform drawing for one chip, and treat it as if the field was apparently enlarged, so that the processing according to the following chip cycle is possible. become.

FIG. 2 is a flow chart showing steps of a first embodiment corresponding to claims 2 and 6. Although only the processing steps related to the electron beam exposure processing are shown here,
The other steps are normal semiconductor device manufacturing steps.
The contents of the processing flow shown in this drawing will be described below.

As described above, the range in which the electron beam can be deflected to draw is about 3 mm square. Therefore, in order to draw on the entire substrate, the process of moving the substrate position by the chip arrangement cycle and the drawing process are alternately performed. Need to be repeated.
In addition to this, the process of rotating the substrate is also performed in the present invention, and in this embodiment, the process involving the rotation and restoration of the substrate is executed in the period of parallel movement of the substrate. The direction in which the substrate is moved in parallel by the mechanical structure of the support is parallel to the X axis or Y axis of the orthogonal coordinate system, and each side of the rectangular cross section of the electron beam is also parallel to either of these.

First, similarly to the ordinary electron beam exposure process, the semiconductor substrate coated with the resist is set at a predetermined position of the exposure apparatus. First, a pattern having a side edge parallel to the X axis or the Y axis is drawn. Since this is a normal electron beam exposure process, it is not necessary to process the electron beam deflection data.

When the drawing of this kind of pattern is completed on one chip, the center point of the chip is made to coincide with the center point of the field, and the substrate is rotated by the angle α about this. α is an intersection angle between the straight line edge of the tilt pattern to be drawn and the X axis or the Y axis, and this rotation makes the straight line edge parallel to the X axis or the Y axis.

At this time, since the position coordinates of the pattern also change due to the rotation, the position coordinates after the rotation are obtained, the electron beam is deflected according to the value, and the drawing process is performed. New position coordinates can be obtained by simple calculation from the position coordinates before rotation and the rotation angle. When it is necessary to draw a pattern having edges with different inclination angles, the rotation angle is corrected and the same processing is performed.

When the drawing of the pattern having the inclined edges is completed, the substrate is rotated in the opposite direction to return to the original angular position, and the substrate is moved to the next chip position in parallel with the X-axis or the Y-axis, and the above-mentioned 2 is performed. Perform the street drawing process. After this is repeated and drawing of all the chips on the substrate is completed, this is developed to obtain a predetermined resist pattern.

In this embodiment, since the substrate is rotated and returned to the original for each chip, it looks complicated at first sight.
Since the position of the pattern to be drawn after rotation is close to the center of rotation, it is unlikely to be affected by the angular error during rotation, and the demand for adjustment accuracy is relatively lenient, and the actual throughput is It will never be as long as it is practical.

FIG. 3 is a flow chart showing steps of a second embodiment corresponding to claims 3 and 7. This will be described below, but in this figure as well, the parts common to the normal semiconductor device manufacturing process are omitted.

As in the first embodiment, the process is started from the point where the substrate is set at a predetermined position and a pattern having a side edge parallel to the XY coordinates is drawn on one chip. In the present embodiment, after this drawing is completed, the substrate is moved in parallel in the X direction or the Y direction by the chip period to advance the next chip to the drawing position, and the edge parallel to the XY coordinates is also applied to this chip. Draw a pattern with.

After this is repeated to draw the same type pattern on all chips, the substrate is rotated by α so that the straight line edges of the inclined pattern are parallel to the X axis or the Y axis. The angle indicated by α is the same as in the first embodiment. At this time, the center of rotation is a reference point set almost at the center of the substrate, and the rotation angle is accurately adjusted to a predetermined value by using the alignment mark provided on the substrate.

In parallel with this, the direction and period of the chip array which changes by rotation are calculated, the rotated substrate is moved according to this calculated value, and the drawing reference point of the first chip is set in the electron beam deflection field. To the specified position of.
Further, according to the position coordinates of the tilt pattern calculated as in the first embodiment, a tilt pattern having a straight edge is drawn. After the drawing of the tilt pattern of one chip is completed, the substrate is moved diagonally according to the calculated value, the drawing reference point of the next chip is aligned with a predetermined position in the deflection field of the electron beam, and the tilt pattern is drawn. ..

By repeating this operation, an inclined pattern is drawn on all the chips, and this is developed to obtain a predetermined resist pattern. In this embodiment, the substrate is rotated only once, but since the parallel movement of the substrate after the rotation is performed based on the data calculated on the assumption that the rotation is correctly performed, there is an error in the angle adjustment. The amount of positional deviation increases as the distance from the center of rotation increases. Therefore, it is desirable to accurately adjust the rotation angle by a method such as using an alignment mark provided at a sufficient distance on the substrate.

[0027]

As described above, according to the present invention, even when an electron beam having a rectangular cross section is used, when drawing a pattern having an edge that is not parallel to the side of the rectangle, It can be formed as a smooth one. This smoothness can be made so dense that it can be identified only by observation using an SEM.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a flowchart showing the steps of the first embodiment.

FIG. 3 is a flowchart showing the steps of the second embodiment.

FIG. 4 is a diagram showing a microscopic shape of a pattern drawn by a square shot.

[Explanation of symbols]

 1 shot 2 pattern

Claims (7)

[Claims] 1. A resist applied to a substrate by selectively irradiating the substrate with an electron beam having a rectangular cross-sectional shape perpendicular to the central axis and each side of the rectangle being parallel to the coordinate axes of an orthogonal coordinate system. In the electron beam exposure process for exposing the substrate, if the drawing area to be formed by electron beam irradiation has a straight side edge which is not parallel to any of the coordinate axes, the substrate is relatively moved with respect to the coordinate axes. The position coordinates of the drawing area shifted by the rotation process are made by rotating the straight line edge of the drawing area parallel to one of the coordinate axes.
The electron beam deflection data for irradiating the drawing area with the electron beam is calculated from the position coordinates before rotation and the rotation angle, and the electron beam is calculated according to the calculated deflection data. An electron beam exposure method comprising a process of irradiating the drawing area with an electron beam while deflecting. 2. An electron beam exposure method including the electron beam exposure process according to claim 1, wherein the same pattern is repeatedly arranged in the coordinate axis direction of the orthogonal coordinate system on the substrate, the repeating cycle. The electron beam exposure process according to claim 1, wherein the substrate is translated in the coordinate axis direction by a predetermined distance in accordance with the above-mentioned steps, and drawing is performed to deflect the electron beam in the coordinate axis direction and the direction orthogonal thereto, and then the substrate is rotated by a predetermined angle. The electron beam exposure method, wherein the substrate is rotated in the opposite direction to the rotation, returned to the original position, and the parallel movement / drawing / rotation / oblique drawing / restoring rotation are repeated. .. 3. The electron beam exposure light method including the electron beam exposure treatment according to claim 1, wherein the same pattern is repeatedly arranged in the coordinate axis direction of the orthogonal coordinate system on the substrate, the orthogonal coordinate system. The electron beam irradiation to the drawing area having an edge inclined with respect to the coordinate axis of the system is performed so that the center of the substrate is almost coincident with the electron beam irradiation position at the time of non-deflection so that the inclined edge becomes one of the coordinate axes. The substrate is rotated so as to be parallel, the position coordinates related to the repeated array after the rotation are calculated from the position coordinates related to the repeated array before the rotation, and the substrate is repeatedly moved diagonally based on the calculated value. And an electron beam exposure method. 4. The electron beam exposure method according to claim 3, wherein the substrate is rotated by a predetermined angle using an alignment mark provided on the substrate. Line exposure method. 5. An electron beam exposure apparatus which performs the process of claim 1, wherein the electron beam exposure device comprises an arithmetic processing device that executes the arithmetic process when the exposure process of claim 1 is performed. 6. An electron beam exposure apparatus that performs the process of claim 2, wherein the electron beam exposure device includes an arithmetic processing device that executes the arithmetic process when performing the exposure process of claim 2. 7. An electron beam exposure apparatus that performs the process of claim 3, wherein the electron beam exposure device comprises an arithmetic processing device that executes the arithmetic process when performing the exposure process of claim 3.