JP4524056B2 - Electron beam drawing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam drawing technique, and more particularly to correction of a pattern drawing position in electron beam drawing.
[0002]
[Prior art]
In recent years, an electron beam drawing apparatus is used for creating a resist pattern. The electron beam drawing apparatus places a sample on which a pattern is to be drawn on a stage, and forms a pattern in a predetermined drawing region while deflecting an electron beam from the electron gun by electromagnetic lens deflection. The drawing area is a position where an electron beam can be projected. Usually, a plurality of drawing areas are defined on the sample. A drawing area in which a pattern is to be drawn is selected from a plurality of drawing areas by moving the stage and deflecting by an electromagnetic lens and a deflection plate. The drawing area selected by moving the stage is sometimes called field A, and the drawing area selected by electromagnetic lens deflection is sometimes called field B.
[0003]
Conventionally, the center of the field B is said to be the position with the best drawing accuracy. Therefore, pattern data is usually processed so that the center of the pattern to be drawn is positioned at the center of field B.
[0004]
[Problems to be solved by the invention]
However, the present inventor has found that the center of the field B cannot be said to be the position with the best drawing accuracy.
[0005]
FIG. 1 is a diagram schematically showing one field B10 on the sample. The stage (not shown) is moved to move the field B10 to a position where it can be projected, and the electron beam is deflected by an electromagnetic lens or a deflection plate (not shown) to draw the variable rectangle 12. The voltage applied to the electromagnetic lens or the deflecting plate is controlled to deflect the electron beam in the x-axis direction and the y-axis direction. The symbol o means the origin of coordinates for specifying the position in the field B10. As described above, conventionally, the center of the field B10 has been said to be the position with the highest drawing accuracy. Therefore, the drawing pattern is positioned on this center.
[0006]
However, it was found that there was a position where the variable rectangular shot moved discontinuously near the center of field B. The cause of the discontinuity can be estimated due to problems in the coordinate calculation method (including error accumulation), certain types of charging and problems in the electrical signals of the control system, but the cause cannot be clarified. It was. However, since the failure is reproducible, it is considered to be a problem specific to the drawing system and method.
[0007]
Accordingly, it is an object of the present invention to provide an electron beam drawing apparatus and method capable of solving the above-described problems of the prior art and drawing a pattern with high accuracy.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is an electronic beam drawing method of drawing a pattern in a predetermined region on the specimen with an electron beam, the drawing faulty area of the drawing fields by examining the discontinuous movement of the variable rectangular shot A first step of identifying and acquiring movement information for eliminating the overlap between the drawing defect area and the pattern, and using the movement information, the pattern is arranged in an area excluding the drawing defect area And a second step of moving the drawing field so that the pattern is drawn in the predetermined area . Thereby, a pattern can be drawn with high accuracy.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
First, the principle of the present invention will be described with reference to FIG.
[0010]
FIG. 2A shows a conventional pattern drawing. The protruding portion of the pattern 14 to be drawn on the field B10 covers the drawing defect area 16 located near the center of the field B10. Therefore, there is a possibility that the drawing of the protruding portion becomes defective.
[0011]
On the other hand, in the present invention, as shown in FIG. 2B, the field B10 is moved as shown by the arrow 18 so that the pattern 14 does not reach the drawing defect area 16. This movement is performed by, for example, processing the coordinates of the field B10 and moving the origin O of the field B10 to O1. In this movement, the direction in which the field B10 is moved and the distance are related. By calculating the direction and distance for moving the field B10 (in other words, calculating the offset amount), the pattern 14 can be accurately applied to a specific position in the field B10 that is the drawing area, that is, the area excluding the drawing defect area 16. Can be drawn. FIG. 3 shows a pattern 14 drawn by moving the field B10 in FIG. 2B with respect to the pattern 14 in FIG.
[0012]
The drawing defect area 16 differs from one electron beam drawing apparatus to another due to factors inherent to the deflection method and the electron beam drawing apparatus. Therefore, a test pattern is drawn on the sample in order to detect the drawing defect area 16 unique to the electron beam drawing apparatus. The test pattern may be an arbitrary pattern. For example, it is formed by repeating lines and spaces. After drawing a pattern on the sample, a resist is applied to the sample, and the entire surface is patterned. Then, the drawing defect area 16 is specified by a predetermined inspection method. The defective drawing area 16 is at the center of the field B10, at a position slightly deviated from this, and varies depending on the electron beam drawing apparatus. Also, the size of the drawing defect area 16 is often different for each apparatus. However, when viewing each of the plurality of fields B10 in the same apparatus, it can be said that the drawing defect area 16 is substantially at the same position and the size is also substantially the same. Further, if all the fields B are not moved in the same way, pattern formation may be hindered. Therefore, it is preferable to move all the fields B by the same distance in the same direction. .
[0013]
In this way, it is possible to determine whether or not to move the field B10 by specifying the drawing defect area 16 and examining the positional relationship with the exposure pattern drawn in the field B10. .
[0014]
In this case, as shown in FIG. 4, by moving the pattern 14 so as not to reach the drawing defect area 16, it may be considered that the field B10L adjacent to the field B10 where the pattern 14 originally existed is applied. In such a case, the movement of the field B10 is invalidated. There is a possibility that a step is generated in the pattern 14 at the boundary between the fields B10 and 10L. When invalidated, the calculation is performed again and the pattern 14 is moved within a range that does not cover the adjacent field B10L so that the overlapping portion between the pattern 14 and the drawing defect area 16 is reduced as much as possible. A relatively thick part is overlapped with the drawing defect area 16. Further, the moving distance and direction of the field B10 may be determined by a method other than these methods. In the worst case, the field B10 may not be moved.
[0015]
Next, an embodiment of the present invention will be described.
[0016]
FIG. 5 is a diagram showing an embodiment of the electron beam drawing apparatus and method of the present invention. The electron beam drawing apparatus 100 draws a pattern on a sample according to the database 20 that stores CAD pattern data, the data processing unit 22 that processes the CAD pattern data read from the database 20 to generate exposure pattern data, and the exposure pattern data. And an exposure unit 24.
[0017]
The exposure unit 24 includes a signal conversion unit 26, a stage control unit 28, a deflection coil control unit 30, and the following optical system. The optical system includes an electron gun 32, an electromagnetic deflection coil 36, and a stage 40.
[0018]
The CAD pattern data stored in the database 20 is data obtained by converting all patterns to be drawn using CAD. The data processing unit 22 converts CAD pattern data and generates exposure data to be supplied to the exposure unit 24. In the generation of the exposure data, the data processing unit 22 uses the position information (position coordinates) of the drawing defect area 16 generated in step S12 of the electron beam drawing method described later and the position shift data generated in step S13. Referring to, exposure data generated from CAD pattern data is corrected. The position shift data is data relating to an exposure pattern that overlaps the drawing defect area 16.
[0019]
The signal converter 26 converts exposure data, which is a digital signal, into an apparatus control signal. This apparatus control signal is a first control signal for moving the stage 40 and a second control signal corresponding to a voltage value applied to the electromagnetic deflection coil and the electromagnetic deflection plate 36. The stage control unit 28 converts the first control signal supplied from the signal conversion unit 26 to generate a voltage signal that is directly applied to a mechanism (not shown) that moves the stage 40. The deflection coil control unit 30 converts the second control signal supplied from the signal conversion unit 26 to generate a voltage signal to be applied to the electromagnetic deflection coil and the electromagnetic deflection plate 36. The electron beam 34 output from the electron gun 32 is deflected by an electromagnetic deflection coil and an electromagnetic deflection plate 36 and irradiated to a silicon or compound semiconductor (semi-insulating) semiconductor substrate 38 which is a sample placed on the stage 40. Is done.
[0020]
The electron beam drawing method shown in FIG. 5 includes steps S11 to S15. In step S11, a test pattern is formed. The test pattern stored in the database 20 is read out, converted into exposure data by the data processing unit 22, and then output to the exposure unit 24. Then, a test pattern is formed on the semiconductor substrate 38 in accordance with the test pattern exposure data.
[0021]
In step S12, the test pattern thus formed is inspected. The inspection is for examining the discontinuous movement of the variable rectangular shot as described above. In addition to this characteristic, the drawing defect area 16 may be specified by focusing on another parameter. The positional information related to the defective drawing area 16 specified by the inspection in step S12 is output to the data processing unit 22.
[0022]
In step S13, it is checked whether or not the exposure pattern 14 exists in the drawing defect area 16, and if it exists, the coordinate data related to the exposure pattern 14 is output to the data processing unit 22 as position shift data. The process in step S13 may be performed by the data processing unit 22 or may be performed by another computer connected to the electron beam exposure apparatus 100. The data processing unit 22 uses the position information of the drawing defect area 16 acquired in step S12 and the position shift data acquired in step S13, and is necessary for eliminating the overlap between the exposure pattern 14 and the drawing defect area 16. The moving direction and moving distance of the field B10 are calculated. In this calculation, the occurrence of the situation shown in FIG. 4 is avoided.
[0023]
In step S14, it is checked whether or not the exposure pattern 14 after moving the field B10 exists in the drawing defect area 16. The processing in step S14 may be performed by the data processing unit 22 or may be performed by another computer connected to the electron beam exposure apparatus 100. If it is determined by this check that the exposure pattern 14 after moving the field B10 exists in the drawing defect area 16, the data processing unit 22 recalculates again. In this case, the pattern 14 is moved within a range that does not cover the adjacent field B10L so that the overlapping portion between the pattern 14 and the drawing failure area 16 is minimized, or a relatively thick part of the pattern is changed to the drawing failure area 16. Make sure they overlap. Further, the moving distance and direction of the field B10 may be determined by a method other than these methods. In the worst case, the field B10 may not be moved.
[0024]
If the determination result in step S14 is OK, an exposure start instruction is given to the exposure unit 24 in step S15.
[0025]
In the above description, the movement of the field B10 has been described. In order to eliminate the overlap between the exposure pattern 14 and the defective drawing area 16, not only the field B10 but also a field A50 (including a plurality of matrix-like fields B10) shown in FIG. 6 may be moved. . Alternatively, only the field A50 may be moved to eliminate the overlap between the exposure pattern 14 and the drawing defect area 16.
[0026]
FIG. 7 is a graph showing the relationship between the offset amount of the field B10 and the pattern discontinuity amount. This graph was obtained from an experiment. The discontinuity of the pattern due to the discontinuity of the variable rectangular shot is reduced or substantially reduced by moving the offset amount, that is, the drawing area of the field B10 or the field A50 by the calculated distance in the calculated direction. Can be resolved.
[0027]
Finally, a part of the gist of the present invention is listed below.
[0028]
(Additional remark 1) In the electron beam drawing apparatus which draws a pattern on a sample with an electron beam,
An electron beam drawing apparatus comprising means for moving the drawing area so as to draw a pattern in an area excluding a specific position in a drawing area defined on a sample.
[0029]
(Additional remark 2) The said means moves the stage in which the sample was mounted, The electron beam drawing apparatus of Additional remark 1 characterized by the above-mentioned.
[0030]
(Additional remark 3) The said means moves the said drawing area | region by an electromagnetic lens deflection | deviation and an electromagnetic deflection plate, The electron beam drawing apparatus of Additional remark 1 characterized by the above-mentioned.
[0031]
(Additional remark 4) The said means has a means to judge whether the said pattern to be drawn exists in the said specific position by comparing the pattern to be drawn with the coordinate of the said drawing area | region. The electron beam drawing apparatus according to any one of claims 1 to 3.
[0032]
(Additional remark 5) The said means has a means to verify that the pattern drawn in the area | region except the said specific position is moved across the said drawing area, and does not straddle the adjacent drawing area. The electron beam drawing apparatus as described in any one of thru | or 4.
[0033]
(Supplementary note 6) The electron beam drawing apparatus according to any one of supplementary notes 1 to 5, wherein the specific position is a position where the drawing accuracy is poorer than other positions.
[0034]
(Supplementary note 7) In an electron beam drawing method for drawing a pattern on a sample with an electron beam,
An electron beam drawing method comprising a step of moving the drawing area so as to draw a pattern in an area excluding a specific position in a drawing area defined on a sample.
[0035]
(Supplementary note 8) The electron beam drawing method according to supplementary note 7, wherein in the step, the stage on which the sample is placed is moved.
[0036]
(Supplementary note 9) The electron beam drawing method according to supplementary note 7, wherein in the step, the drawing region is moved by electromagnetic lens deflection and an electromagnetic deflection plate.
[0037]
(Additional remark 10) The said step has a step which judges whether the pattern to be drawn exists in the specific position by comparing the pattern to be drawn with the coordinates of the drawing area. 10. The electron beam drawing method according to any one of 7 to 9.
[0038]
(Supplementary note 11) The supplementary note 7 includes the step of verifying that the pattern drawn in the region excluding the specific position does not straddle adjacent drawing regions by moving the drawing region. The electron beam drawing method as described in any one of thru | or 10.
[0039]
(Supplementary note 12) The electron beam drawing apparatus according to any one of Supplementary notes 7 to 11, wherein the specific position is a position where the drawing accuracy is poorer than other positions.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an electron beam drawing apparatus and method capable of drawing a pattern with high accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram showing a conventional technique and its problems.
FIG. 2 is a diagram illustrating the principle of the present invention in comparison with the prior art.
FIG. 3 is a diagram showing a relationship between a pattern drawn by the present invention and a drawing defect area;
FIG. 4 is a diagram showing a relationship between a pattern that is not preferable in drawing according to the present invention and a drawing defect area;
FIG. 5 is a diagram showing an embodiment of the present invention.
6 is a diagram showing a relationship between a field A and a field B. FIG.
FIG. 7 is a graph showing the relationship between the offset amount and the pattern discontinuity amount showing the effect of the present invention.
[Explanation of symbols]
10 Field B
14 Pattern 16 Drawing discontinuous area 18 Movement of field B

Claims (4)

In an electron beam drawing method for drawing a pattern in a predetermined region on a sample with an electron beam,
A first step of identifying a drawing failure area of a drawing field by examining discontinuous movement of a variable rectangular shot, and acquiring movement information for eliminating overlap between the drawing failure area and the pattern;
A second step of moving the drawing field using the movement information so that the pattern is drawn in the predetermined area in a state where the pattern is arranged in an area excluding the defective drawing area;
Electron beam lithography method, which comprises a. The second step, the electron beam drawing method according to claim 1, characterized in that moving the stage in which the sample is placed. The second step, the electron beam drawing method according to claim 1, characterized in that for moving the drawing area by electromagnetic deflection. After the second step , the method includes a third step of determining whether the pattern to be drawn is in the drawing defect area by comparing the pattern to be drawn with the coordinates of the drawing field. The electron beam drawing method according to any one of claims 1 to 3, characterized in that :

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