JP3494785B2 - Electron beam drawing apparatus and drawing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam lithography apparatus used for manufacturing semiconductor devices and the like, and more particularly, to an electron beam lithography apparatus of a variable shaped beam system, and And a method of drawing a figure having an oblique line by using. 2. Description of the Related Art With the miniaturization of LSI pattern dimensions, electron beam exposure technology has been used in place of conventionally used light exposure. Electron beam writing methods are roughly classified into a point beam writing method mainly for ultrafine writing and a variable shaped beam writing method with high versatility. Here, in the variable shaped beam writing method, shaping apertures having first and second rectangular apertures are provided at two positions on an electron beam trajectory, and writing is performed by an electron beam formed by passing through each aperture. The size of the rectangular beam is controlled by an electron beam deflector provided between the first and second shaping apertures. Recently, a method of forming a triangular electron beam has been devised as an application of the variable shaped beam method. The formation of the triangular beam is performed by providing a rectangular stop having a different angle from the rectangular stop of the first forming stop on the second forming stop. By the way, when drawing a figure having a diagonal pattern using only a conventional rectangular electron beam, an extremely thin rectangular electron beam had to be used so that no step was formed on the diagonal line. If a triangular electron beam is formed, and if the angle of the oblique line of the triangle is equal to the angle of the oblique line of the figure, a triangular electron beam with a large area can be exposed as it is. Can be drawn at high speed, and the throughput can be improved. In addition, in the conventional variable shaped beam method, an oblique line pattern which is divided and drawn by a rectangle in the conventional variable shaped beam method is divided by a triangle having the same inclination angle in this method, so that improvement in accuracy is realized. A typical example of the above triangular beam forming method is disclosed in Japanese Patent Application Laid-Open No. 60-30131. In the above representative example, a first forming aperture having a rectangular shape, a second shaping aperture having a shape obtained by combining a rectangular aperture and a rectangular aperture rotated by 45 degrees with respect to the first aperture are provided. After the electron beam is deflected, the beam is irradiated onto the second shaping aperture to form a rectangular beam of an arbitrary size or a right-angled isosceles triangular beam. The sizes of the rectangular beam and the right-angled isosceles triangular beam are changed by changing the deflection amount of the electron beam that has passed through the first shaping diaphragm. . [0005] However, in the above conventional example, sufficient consideration was not given to a method of forming a triangular beam. That is, in the above conventional example, when a triangular beam is formed, the position of each vertex of the formed triangle is determined by the position of the electron beam deflector provided between the first and second shaping apertures on the image plane. It moves by changing the deflection voltage. Therefore, there cannot be a fixed point on the image plane that serves as a reference for the position, which complicates the adjustment of the drawing position, and eventually lowers the drawing position accuracy. Also,
In the above conventional example, the area where the electron beam passing through the first forming aperture is deflected on the second forming aperture becomes asymmetric with respect to the rectangular aperture in the second molding aperture, and changes from a rectangle to another triangle. When changing the shape of the electron beam, the amount of change in the deflection voltage applied to the deflector differs depending on the triangle selected. Therefore, when the deflection distance is longest, the deflection settling time is rate-determined. Is required. Furthermore, in the above-mentioned conventional example, the only triangles that can be formed are right-angled isosceles triangles. Therefore,
Vertical and horizontal rectangular patterns and 45-degree oblique line patterns can be drawn with high accuracy, but oblique line patterns with other angles must be drawn using rectangular beams, and accuracy and the rate-determining factors of throughput Has become. Further, in the conventional example, there is no method other than calibration using the drawing result, such as the rotation and magnification of the electron beam. That is, there is a problem that it takes time to calibrate the optical system. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides an electron beam drawing apparatus and a drawing method capable of drawing a figure having an oblique line at high speed and with high accuracy. The purpose is to: In order to achieve this object, according to the present invention, a variable shaped beam type electron beam lithography system is provided with four shaped apertures around a rectangular aperture. A right-angled triangular diaphragm having the same shape but a different direction is arranged.
Then, the rectangular electron beam that has passed through the rectangular aperture, which is the first aperture, is deflected by an electron beam deflector provided between the first and second apertures, and the rectangular aperture or the right angle aperture of the second aperture is stopped. By irradiating the light on the triangular stop, a rectangular or right triangular electron beam is formed. This rectangular or right-angled triangular beam size is obtained by changing the size of the cut between the rectangular beam passing through the first aperture and the rectangular or right-angled second aperture by the electron beam deflector. In this case, for the right-angled triangular stop, one of the vertices that is not a right angle is always irradiated with the electron beam. Also, in order to draw a pattern having oblique lines other than a vertical and horizontal rectangular pattern and a 45 ° oblique pattern, five aperture groups of one rectangular aperture and four right-angled triangle apertures are divided into one. As a unit, a plurality of the aperture groups are provided at the position of the second aperture, and right-angled triangular apertures having different angles are arranged in each aperture group. Further, an electron beam calibration aperture group having a calibration aperture for calibrating the electron optical system is provided on the second shaped aperture. In the case of using the above-described electron beam drawing apparatus to draw a pattern having an oblique line, a right-angled triangular diaphragm having an angle equal to the angle of the oblique line is selected from a plurality of aperture groups. Then, drawing is performed by an electron beam shaped into a right triangle by the aperture. At this time, the position coordinates of a non-perpendicular vertex to which the electron beam is always irradiated by the right-angled triangular diaphragm is used as a reference point for positioning at the time of drawing. [Embodiment 1] Embodiments will be described below in detail with reference to the drawings. A first example is a method of forming a variable rectangular beam and a variable triangular beam using one variable shaping deflector. FIG. 1 shows a second forming aperture in the present invention, and FIG. 2 shows a conceptual diagram of an electron beam lithography apparatus using the present invention.
The electron beam accelerated to 50 kV from the electron gun 1 and emitted is formed into a rectangular or right triangular shape using the first shaping diaphragm 2 and the second shaping diaphragm 4, and then the electron beam is reduced by the reduction lens 5 and the objective lens 6. The beam is reduced and projected, and is exposed on the target 7. The formation of the rectangular or triangular electron beam is performed by a deflector 3 provided between the first shaping diaphragm 2 and the second shaping diaphragm 4. The 20-μm-thick silicon material forming aperture is formed by using the SOI process conventionally used for the collective figure irradiation method. By the way, as shown in FIG.
, Four types of right-angled isosceles triangular diaphragms 8 to 11 are formed. When forming a rectangular or triangular electron beam with each aperture, the first shaped aperture 2 having a rectangular aperture
The rectangular beams 23 to 27 that have passed through are moved on the respective apertures on the second shaping aperture 4 as indicated by arrows 13 to 16 and 17 in the figure to obtain a right-angled triangle or rectangular electron beam having a desired size. The size of the electron beam formed by the rectangular aperture 12 in the second shaping aperture 4 is 62.5 μm at maximum, and is reduced to 1/25 by the reduction lens 5 to be a rectangular beam of 2.5 μm at maximum. . The deflector 3 for changing the size of the electron beam has 11 bits and a maximum of 10 V, and enables high-speed deflection. Also,
When forming the triangular beam, one of the non-perpendicular vertices of the right-angled triangular diaphragms 8 to 11 on the second forming diaphragm was always irradiated with the electron beam.
As a result, even if the beam is moved as indicated by arrows 13 to 17 in FIG. 1, the vertices 18 to 22 of the respective apertures become fixed points on the target with respect to the dimensional change, and these are used as reference points for positioning at the time of drawing. Thereby, accurate drawing can be performed. Also, right-angled triangular diaphragms 8 to 11 oriented in four directions are provided.
Are arranged as shown in the figure, the deflection distance when changing the position of the electron beam from the rectangular aperture to the right triangle apertures 8 to 11 is minimized. That is, it is possible to select a rectangular or right triangle electron beam at high speed. In this embodiment, the magnification of the electron beam is calibrated as follows. First, in the case of calibration,
The second forming aperture 4 is mechanically moved so that the calibration aperture group is located on the axis. FIG. 5 shows the calibration diaphragm group 36. The calibration aperture group 36 includes electron beam calibration apertures 37 to 4.
Have seven. Calibration of electron beam rotation, magnification, and the like is performed using the main diaphragm group 36. Here, the magnification calibration will be described as an example. For adjusting the magnification, the calibration diaphragms 38 and 42 in the calibration diaphragm group 36 are used. First, the calibration aperture 38 is selected, and the position of the electron beam on the target 7 is detected. Next, the calibration diaphragm 42 is selected, and the position of the electron beam is detected. Then, from each beam position, the calibration aperture 3
The distance between 8, 42 is calculated. Calculated aperture 3 for calibration
The distance between 8, 42 is compared with the distance between design apertures, the magnification error is calculated, and calibration is performed. When the above is expressed by an equation, the magnification error ΔM
Is represented by the following equation. ## EQU1 ## Here, L is the distance between design apertures, L 'is the distance between measurement apertures, and M is the target magnification. When the magnification and the rotation are calibrated using this example and the drawing is performed, the electron beam calibration conventionally confirmed based on the drawing result can be performed at a high speed of about 1 minute. Also, the calibration apertures 38 and 42
Is the maximum distance that can be deflected by using the deflector 3, and therefore, the most accurate calibration is possible. In this example, the calibration method using the calibration apertures 38 and 42 has been described for the purpose of calibration of the magnification. However, even when performing other calibrations such as rotation and astigmatism, the calibration apertures 38 to 42 may be used. 42, and can be performed similarly. Next, using this embodiment, the pattern shown in FIG. 3 was drawn. The figure shows an inclination angle of 45 degrees and a line width of 0.2μ.
m line and space pattern. When the line dimension 28 of this pattern was measured using an SEM, the dimensional accuracy was 3σ and 0.0, as compared with the case where the conventional variable forming method was used.
A significant improvement was obtained from 6 μm to 0.03 μm.
Also, as a result of drawing a device pattern using this example,
Compared to the conventional variable forming method, the number of shots is reduced to about 1/2 and the throughput is reduced from 5 / hour to 9 /
Sheets / hour, compared to the conventional triangle forming method,
High-speed drawing was possible from 7 images / hour to 9 images / hour. Furthermore, as a result of drawing a 5: 1 stepper reticle using the present embodiment, the same dimensional accuracy as in the case of the above-described wafer drawing can be obtained. 256 μmD of 2 μm
When a RAM was created, the dimensional accuracy was improved from 0.04 μm to 0.03 μm, and the yield, which was 65% in the past, was improved to 80%. The arrangement of the right-angled triangular diaphragm on the second shaping diaphragm is not limited to the one shown in FIG. 1, but also the one shown in FIG. 4, and the one obtained by rotating the group of figures in FIGS. ,
Although it is conceivable that the angle of the triangle is other than 45 degrees, the same effect as in the present embodiment can be obtained by using any graphic arrangement. [Embodiment 2] Embodiment 2 is an example in which two sets of electron beam shaping deflectors are used. That is, the system is provided with a deflector for selecting a group of apertures and a deflector for forming a variable shaped beam in one group of apertures. FIG. 6 shows a conceptual diagram of an electron beam lithography apparatus using the second embodiment, and FIG. 7 shows an example of a second forming aperture used here. In FIG. 7, the aperture groups of a rectangular aperture and four right-angled triangle apertures are arranged as one unit, and the aperture groups are arranged in units of three units vertically and horizontally. Right-angled triangular diaphragms having different angles are arranged in each diaphragm group, and an appropriate diaphragm group is selected according to a drawing pattern. 45 degrees, 30 in the aperture group
A group of right-angled triangular diaphragms having degrees, 60 degrees and other angles was prepared. Accordingly, it is possible to cope with oblique line drawing at more angles. The formation of a rectangular or triangular electron beam in one stop group is performed using the first shaping deflector 3 according to the first embodiment. When moving the electron beam from one stop group to another stop group, the second shaping deflector 29 is used. The second shaping deflector 29 deflects the electron beam to the range of all the aperture groups in FIG. The size of the 3 × 3 stop group in FIG. 7 is 675 μm square. Therefore, as the second shaping deflector 29, a two-stage deflector of 12 bits and a maximum of 150V was employed. The second shaping deflector 29 has a wider deflection range than the first shaping deflector 3, but requires a long settling time. When the deflection voltage of the first shaping deflector 3 is 0, the rectangular beam that has passed through the first shaping diaphragm 2 is converted by the second shaping deflector 29 into a group of apertures selected by the second shaping diaphragm. When the lens is placed at the center of the rectangular stop, which is the center of the above, the deflection range of the first shaping deflector 3 becomes symmetrical, and efficient deflection becomes possible. Since there is a rectangle and a right-angled triangle in four directions in one aperture group, drawing with a rectangle and one type of triangle can be performed at the highest speed.
Also, since a rectangular aperture is provided for each aperture group,
The rectangular diaphragm and the right-angled triangular diaphragm can be selected at high speed without using the second shaping deflector 29 having a slow deflection settling time. In the case where an aperture group is provided outside the deflection range of the second shaping deflector 29 and an aperture group outside the deflection range of the second shaping deflector 29 is selected, the second shaping If the entire diaphragm can be moved mechanically, more types of right triangles can be selected. In addition, when a plurality of aperture groups having the same shape are prepared, and when one aperture group becomes unusable due to contamination or other reasons, another aperture group of the same type is used to effectively use the second forming aperture. Becomes possible. Next, in the second embodiment, the magnification of the electron beam is calibrated as follows. In FIG. 7, aperture groups 49 and 56 are aperture groups for electron beam calibration. That is, the aperture group 49 is provided with electron beam calibration apertures 43 to 48, and the aperture group 56 is provided with calibration apertures 50 to 55. Therefore, in the calibration of the magnification, first, the first and second shaping deflectors 3, 2
9, the calibration aperture 44 is selected, and the position of the electron beam on the target 7 is detected. Next, similarly, the calibration diaphragm 55 is selected, and the position of the electron beam is detected. The reason why the calibration apertures 44 and 55 are used is that the distance between the calibration apertures 44 and 55 is the longest in the apertures in the present example, and accurate calibration can be performed. Also, in the case of detecting the position of each electron beam, the deflected electron beam is not returned. The distance between the apertures for calibration is measured from each electron beam position, and the magnification is calibrated using the same equation as in the first embodiment. As a result of performing the magnification calibration according to the present example, the magnification adjustment accuracy, which was 0.2% in the first embodiment, was improved to 0.1%. In this example, the calibration apertures in the two calibration aperture groups were used as an example for adjusting the magnification. However, when performing other calibrations such as electron beam rotation and astigmatism, two calibration apertures were used. Alternatively, the calibration can be similarly performed by using a plurality of calibration aperture groups or calibration apertures. Further, in this example, the calibration was performed using the calibration apertures 44 and 55. However, when the calibration was performed using the variable-shape rectangular aperture, the present embodiment can be performed without providing a special calibration aperture group. The same effect as described above can be obtained. Next, the pattern shown in FIG. 8 was drawn using the second embodiment. FIG. 8 shows that each of the inclination angles is 60 degrees,
This is a line-and-space pattern of 45 degrees, 30 degrees, and a line width of 0.2 μm. Line dimensions 33, 34, 3 of this pattern
5 was measured using an SEM. The dimensional accuracy was 3 .sigma.
m to 0.03 μm. The dimensional accuracy of the obtained oblique line was exactly the same as that of the patterns of 0 ° and 90 °. Furthermore, compared to the conventional variable forming method, the number of shots is reduced to about 場合 in the case of a pattern having a mixture of rectangular and 45 degrees, and about 1 in the case of a pattern having a mixture of rectangular, 30 degrees, 45 degrees and 60 degrees. And the throughput is reduced from 5 wafers / hour using a conventional variable shaping method for 6-inch wafers to 9 wafers / hour in the case of a rectangular and 45 ° mixed pattern.
In the case of a pattern having a mixture of time, rectangle, and 30 degrees, 45 degrees, and 60 degrees, 10 sheets / hour, and 7 sheets / hour to 9 sheets / hour and 10 sheets / hour as compared with the conventional triangle forming method.
High-speed drawing to sheets / hour was made possible. In this example, a total of nine aperture groups were prepared for each of the three vertical and horizontal aperture groups.
It is also possible to prepare more diaphragm groups within the range that the second shaping deflector 29 can select. Further, in this example, the drawing examples of 30, 45, and 60 degrees are shown. However, in the case of drawing at other angles, the present embodiment can be realized by selecting a stop group having a right-angled triangular stop at a corresponding angle. The same effect as that of No. 2 can be obtained. As described above, the electron beam lithography apparatus and the lithography method according to the present invention are a variable-shaped beam type lithography apparatus and a lithography method. Same shape but different direction around the aperture 4
By providing the right-angled triangular diaphragms, the shape of the electron beam can be switched between a rectangular shape and a right-angled triangle shape at high speed, and a pattern having oblique lines can be drawn at high speed and with high accuracy. At this time, one of the non-right-angle vertices of the right-angled triangular diaphragm is always irradiated with an electron beam, and its position coordinates are used as a reference point for positioning at the time of drawing, thereby enabling high-precision oblique line drawing. The rectangular aperture of the second forming aperture and the four right-angled triangular apertures surrounding it are defined as a single aperture group, and a plurality of the aperture groups are provided on the second molding aperture. A right-angled triangular diaphragm having a different shape is provided for each diaphragm group, and by selecting a particular diaphragm group therein, the electron beam is formed into a right-angled triangle having a particular angle. Line figures can be drawn at high speed and with high precision. Further, by providing a calibration aperture group having a calibration aperture in the second forming aperture, it is possible to perform electron beam calibration in a very short time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an example of a second forming aperture of a variable shaped beam type electron beam writing apparatus according to the present invention. FIG. 2 is a diagram showing a configuration of a variable shaped beam type electron beam writing apparatus according to the present invention. FIG. 3 is a diagram showing a pattern for measuring dimensional accuracy drawn by an electron beam drawing apparatus according to the present invention. FIG. 4 is a view showing another example of the second forming aperture according to the present invention. FIG. 5 is a view showing a group of apertures for electron beam calibration in a second shaped aperture according to the present invention. FIG. 6 is a configuration diagram of an electron beam lithography apparatus according to the present invention having a second shaped aperture having a plurality of aperture groups. FIG. 7 is a diagram showing the arrangement of each stop in a second forming stop having a plurality of stop groups according to the present invention. FIG. 8 is a diagram showing a pattern for measuring dimensional accuracy drawn by the apparatus according to the present invention. [Description of Signs] 1 ... Electron gun 2 ... First forming stop 3 ... First forming deflector 4 ... Second forming stop 5 ... Reducing lens 6 ... Objective lens 7 ... Target 8-11 ... Right triangle stop 12 ... Rectangle stop Reference numerals 13 to 17: Variable dimension directions 18 to 22, Fixed points 23 to 27: Electron beam images 28, 33 to 35 passing through the first forming aperture 29, Dimension measurement points 29, Second shaping deflectors 30, 45-degree aperture group 31 , 32 ... 30 degree, 60 degree diaphragm groups 36, 49, 56 ... E-beam calibration diaphragm groups 37-48, 50-55 ... E-beam calibration diaphragms

──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiro Kawasaki, 882 Ma, Hitachinaka-shi, Ibaraki Pref., Ltd.Measurement Division, Hitachi, Ltd. (56) References JP-A-9-134701 (JP, A) JP-A-9-161714 (JP, A) JP-A-4-246815 (JP, A) JP-A-7-335553 (JP, A) A) JP-A-59-169131 (JP, A) JP-A-60-30131 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37/305

Claims (1)

(57) Claims 1. It has a first shaping diaphragm having a first rectangular diaphragm and a second shaping diaphragm, and deflects the electron beam passing through the first rectangular diaphragm. A variable shaped beam type electron beam writing apparatus for shaping an electron beam by moving over the second shaping aperture using a tool.
Is provided with four right-angled triangular diaphragms having the same shape but different directions around the second rectangular diaphragm, and the electron beam passing through the first rectangular diaphragm is provided on the right-angled triangular diaphragm. The electron beam can be shaped into a right-angled triangular shape by irradiating the aperture. Further, five apertures of the same second rectangular aperture and four right-angled triangle apertures of the same shape but having different directions are combined with one another. A plurality of aperture groups are provided on a second forming aperture, and a plurality of aperture groups are provided on the second forming aperture, and the electron beam is formed into a rectangular shape within one of the plurality of aperture groups provided on the second forming aperture. Alternatively, a first electron beam deflector is used for forming a right triangle, and a second electron beam deflector is used for moving an electron beam from one stop group to another stop group. Electron beam drawing equipment.