JP2004015069A - Charged particle beam drawing system and drawing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the drawing accuracy of a multi-beam system by eliminating deviation in continuity at the boundary of the drawing area. <P>SOLUTION: An electron beam drawing system of the multi-beam system having a plurality of electron beam optical systems comprises reference mark groups 10 provided respectively on the sample base in accordance with the plurality of electron beam optical systems 13, a moving mechanism for moving the reference mark groups 10 on the sample base, a measuring mechanism for scanning the moved reference marks 10 with an electron beam 7 and measuring the position of each reference mark 10, a storage unit for storing the relation of relative position of each measured reference mark 10, and a correction unit for correcting the position of the drawing area of each electron beam based on the stored relation of relative position of each reference mark 10, and carries out drawing based on the corrected drawing position. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a multi-beam type charged beam writing apparatus and a writing method having a plurality of charged beam optical systems.

電子 Conventionally, electron beam lithography systems have been widely used for developing advanced devices. This electron beam drawing apparatus is to deflect an electron beam electromagnetically or electrostatically and draw a desired figure on a sample. However, when the beam is simply deflected, a deflection distortion as shown in FIG. Therefore, prior to drawing, it is necessary to adjust the drawing position as shown in FIG.

The adjustment of the drawing position is generally performed as follows. That is, the stage is moved by the beam deflection distance, and the voltage or current applied to the deflection electrode or coil is determined so that the mark provided on the stage can be detected. At this time, as a mark used for beam adjustment, there is a mark utilizing a difference in atomic number between the mark and the underlying substrate and a difference in reflected electron rate due to unevenness. The size of the beam deflecting area is usually from 100 μm to several mm, and when writing is performed in a range beyond the deflecting area, the stage is moved into the beam deflecting area to perform writing.

In the figure, reference numeral 201 denotes a deflection region having distortion, and reference numeral 202 denotes a deflection region in which distortion has been corrected.

In addition, in the manufacture of a semiconductor device, it is general that overlay exposure is performed on a base pattern formed on the same substrate. In such a case, it is necessary to detect the position of the mark provided on the base substrate. As the position detection mark, there is a mark that utilizes the difference in the reflected electron ratio due to the difference in the atomic number between the mark and the base substrate, as in the case of the adjustment of the drawing position. The mark position is detected by scanning the mark with an electron beam and measuring the intensity of the reflected electron signal.

In recent years, technology development of electron beam lithography systems aiming at high throughput has been carried out. Among them, a multi-beam system having a plurality of electron beam optical systems is effective. In this multi-beam type electron beam writing apparatus, writing is performed not by one beam but by a plurality of beams, so that the writing throughput is expected to be remarkably improved.

The multi-beam method requires beam adjustment in each optical system, and it takes an enormous amount of time to perform individual beam adjustments sequentially. For this reason, in the above-described adjustment of the drawing position and the overlay exposure, it is necessary to simultaneously detect marks for a plurality of beams. However, if mark detection is performed simultaneously with a plurality of beams, there is a problem that accurate alignment cannot be performed due to the influence of reflected electrons from other marks.

That is, as shown in FIG. 26, one electron optical system includes an electron gun 1, beam blanking systems 3 and 4, beam deflection systems 5a and 5b, beam adjustment lens systems 2a, 2b and 2c, and a reflected electron detector. It consists of six. FIG. 27 shows an overview of the beam adjustment mark. 27A is a plan view, and FIG. 27B is a cross-sectional view. When the mark position is detected, as shown in FIG. 28, the marks 10 are provided in the drawing area 12 corresponding to each electron beam optical system 13, and the beam scanning is performed on the plurality of marks 10 at the same time. And the reflected electron signal corresponding thereto, the mark position is detected. In a conventional electron beam optical system, as shown in FIG. 29, when a mark is detected by a plurality of electron beams 7 at the same time, a reflected electron 8 from another mark and a reflected electron 9 from another mark are simultaneously detected. Enter the detector 6 from the lateral direction, and it is difficult to detect individual mark positions.

As a countermeasure, a method of shifting the position detection timing for each electron beam optical system, and a method of aligning a plurality of chips collectively without performing alignment for each chip have been proposed. However, these methods have problems that the device configuration becomes complicated and that the mark detection takes a longer time than when the mark detection is performed simultaneously by all the electron beam optical systems.

On the other hand, the multi-beam method is not a batch exposure like an optical stepper or an X-ray exposure, and therefore requires beam adjustment in each lens barrel. In the case of a conventional electron beam writing apparatus having only one electron beam source, only one writing position adjustment mark is used. However, in a multi-beam lithography system, many beam adjustments must be performed, so that when one mark is shared, much time is required for beam adjustment. For this reason, in the multi-beam drawing apparatus, it is necessary to adopt a method of having a reference mark corresponding to each electron beam optical system and performing beam adjustment for each lens barrel.

However, the following problems occur in the method of performing beam adjustment for each lens barrel using the above-described reference marks corresponding to each electron beam optical system. That is, the chip size varies depending on the type of device, and one chip does not always correspond to one electron beam source. As shown in FIG. 30, when drawing a pattern 213 larger than the arrangement pitch of the electron beam optical systems 211 (more specifically, the drawing area 212 by one electron beam optical system), a plurality of electron beam optical systems 211 are required. Is used to draw one pattern 213. For example, when the electron beam optical systems are arranged at a pitch of 10 mm, if the chip size exceeds 20 mm square, drawing is performed using four or more electron beam optical systems. Further, when a sample such as a photomask having a side exceeding 150 mm is drawn, drawing is performed with more electron beams.

Here, there is no problem if the position of the reference mark 214 of each electron beam optical system is ideally arranged as shown in FIG. However, actually, the pattern should be distorted as shown in FIG. 31B, and the pattern drawn based on this reference mark has a distorted shape as shown in FIG. In this case, when one chip is drawn by a plurality of electron beam sources, as shown in FIG. 33, there is a problem in connection accuracy at a drawing area boundary of an adjacent electron beam optical system. Reference numeral 215 denotes one drawing area, 216 denotes a drawing area boundary, and 217 denotes a drawing pattern.

精度 The accuracy of the connection of the deflection regions is important for the drawing accuracy. This is because no matter how small the minimum size of the beam is, if the connection accuracy is poor, it is not possible to draw a figure according to the design data on the sample.

As described above, since the above-described multi-beam method is not a batch exposure like a stepper, it is necessary to adjust a beam in each lens barrel. Since each electron beam source of the multi-beam drawing apparatus has an independent electron optical system, there is a problem in that even if beam adjustment is performed individually, the connection accuracy between different electron beam sources is deteriorated. In addition, the chip size varies depending on the type of device, and it is not always reasonable to use a method in which one chip corresponds to one electron beam source. It is inevitable that one chip is drawn by a plurality of electron beam sources, but at this time, there arises a problem that the connection accuracy in a beam deflection boundary region is deteriorated due to a difference in beam characteristics for each electron beam source.

As described above, in the conventional multi-beam type electron beam writing apparatus, when writing a pattern requiring a writing area larger than the arrangement pitch of each electron beam optical system, the drawn pattern is distorted or adjacent. There is a problem that the connection accuracy in the electron beam drawing area is deteriorated.

Note that these problems are not limited to the electron beam writing apparatus, but can be similarly applied to an ion beam writing apparatus using an ion beam as a charged beam.

The present invention has been made in view of the above circumstances, and an object thereof is to eliminate a displacement at a drawing area boundary and to improve a drawing accuracy by a multi-beam type charged beam. An object of the present invention is to provide a drawing apparatus and a drawing method.

(Constitution)
In order to solve the above problems, the present invention employs the following configuration.

(1) In a multi-beam type charged beam drawing apparatus having a plurality of charged beam optical systems, a reference mark group provided on a sample table corresponding to the plurality of charged beam optical systems, and a movement on the sample table. A means for moving the reference mark group, a means for scanning the moved reference mark with a charged beam to measure the position of each reference mark, and a means for storing the measured relative positional relationship of each reference mark, Means for correcting the position of the drawing area of each charged beam based on the relative positional relationship between the stored reference marks, and means for performing drawing based on the corrected drawing position. I do.

Further, there is provided a multi-beam type charged beam writing apparatus having a plurality of charged beam optical systems, wherein a writing position is corrected using a reference mark group provided on a sample stage in correspondence with each charged beam optical system. Performing a mark position detection using a plurality of charged beam optical systems, performing a mark position detection using reference marks of adjacent charged beam optical systems, and The method includes a step of calculating a positional relationship, a step of correcting a position of a drawing area of each charged beam optical system based on the calculation result, and a step of drawing at the corrected drawing position.

(2) A multi-beam type charged beam writing method for performing writing using a plurality of charged beam sources, wherein writing is performed so that the deflection boundary regions of adjacent charged beam sources overlap with each other. Further, the present invention is characterized in that the dose of the overlapping area is corrected.

(Action)
In the configuration of the above (1), after the mark position is detected by each charged beam optical system, the mark position is detected by using the reference mark of the adjacent charged beam optical system. By measuring the relative positional relationship with the drawing area of the optical system and performing the drawing by correcting the drawing position in the actual drawing, the connection accuracy is improved, and high-precision drawing can be performed.

According to the above configuration (2), the overlapping of the deflection region boundaries of the adjacent charged beam sources is performed, and the irradiation amount of the overlap region is corrected, so that the drawing caused by the difference in the beam characteristics of each charged beam source is performed. It is possible to eliminate the gap between the regions and improve the drawing accuracy.

As described above in detail, according to the present invention, even in the case of pattern writing that requires a writing area larger than the arrangement pitch of each charged beam optical system in a multi-beam type writing apparatus, writing is performed by a plurality of charged beam optical systems. In this case, the accuracy of the connection at the boundary of the drawing area of the charged beam is improved, and high-precision drawing can be performed.

前 Before describing the embodiments of the present invention, a reference example of the present invention will be described.

(Reference example)
FIG. 1 is a diagram showing one electron beam optical system in a multi-beam type electron beam writing apparatus according to a reference example of the present invention. This electron beam optical system includes an electron gun 1, beam blanking systems 3 and 4, beam deflection systems 5a and 5b, beam adjustment lens systems 2a, 2b and 2c, and a reflected electron detector 6.

(4) When performing mark position detection, beam scanning is performed on a mark corresponding to each electron beam. However, in the conventional electron beam optical system, the backscattered electron detector is exposed as shown in FIG. For this reason, when a mark is detected with a plurality of electron beams, the reflected electrons from other marks enter the detector from the lateral direction, making it difficult to detect the position of each mark.

In contrast, in the present embodiment, as shown in FIG. 1, a collimator 11 is attached to the backscattered electron detector 6. For this reason, as shown in FIG. 2, even when the position of the mark 10 is detected simultaneously with a plurality of beams 7, the reflected electrons 8 from the corresponding mark 10 are detected from the other marks 10 while being detected as in the related art. Of the reflected electrons 9 can be prevented. Even when the beam is deflected in a range of several mm as in the correction of the deflection distortion, it is possible to remove only the reflected electrons 9 from other marks 10 by adjusting the aperture angle.

As described above, in the present embodiment, the backscattered electrons 9 from other marks 10 can be removed by the collimator 11 attached to the backscattered electron detector 6. For this reason, even when the alignment is performed simultaneously by a large number of electron beams 7, the mark position can be detected independently by each electron beam, and the writing time can be greatly reduced.

Next, a more specific example than the reference example will be described.

(Reference Example 1-1)
FIG. 3 is a diagram showing a schematic configuration of a multi-beam type electron beam writing apparatus used in this embodiment. In the figure, 13 is an electron beam optical system, 14 is a sample, 15 is a sample chamber, 16 is a stage, 17 is a reference mark, 18 is a control circuit, 19 is a control computer, and 50 is a stage length measurement system.

加速 The accelerating voltage of this drawing apparatus is 10 kV. The drawable range is 150 mm square, and 15 × 15 pieces of 225 electron beam optical systems are arranged at a pitch of 10 mm. The beam deflection system 13 has a main / sub / two-stage configuration using electrostatic deflection. The size of each deflection area is 500 μm for main deflection and 100 μm for sub deflection. The drawing area of each electron beam optical system 13 is ± 5 mm around the electron gun, and this drawing area is drawn by 400 main deflection areas.

ビ ー ム A beam adjustment mark is provided on the stage 16 as shown in FIG. There are 15 × 15 marks corresponding to each electron beam optical system 13 so as to form a pair, and one mark is provided in the drawing area of each electron beam optical system 13. The mark has a cross shape as shown in FIG. 27, and was formed by excavating a Si substrate by light exposure and plasma etching. The size of the mark is 100 μm on one side, the width is 5 μm, and the depth is 2 μm.

In the present embodiment, the collimator 11 is provided in the backscattered electron detector 6 of each electron beam optical system 13 as shown in FIG. The collimator 11 has a cylindrical shape.

Here, the deflection distortion correction of the multi-beam type electron beam writing apparatus will be described with reference to FIG. The deflection distortion was corrected in the following manner.

{Circle around (1)} First, the 500 μm main deflection area is divided into 50 μm meshes, and the stage is moved so that the reference marks 20 are located on the grid points. The beam is then deflected and scanned over the mark 20. The deflection voltage at the mark center is calculated from the beam deflection amount and the mark position. As shown at 22 in the figure, the reference mark is sequentially moved and the deflection amount is stored. The same operation was performed for a sub-deflection region having a size of 100 μm square. At this time, the mesh size was 5 μm.

偏向 As a result of performing the deflection distortion correction for 15 × 15 beams simultaneously, it was possible to perform the correction for each electron beam optical system without any problem. At this time, the time required for beam adjustment was 1 minute. It took 225 minutes (approximately three and a half hours) when the beam adjustment was performed for each of 15 × 15 beams. In contrast, in the present reference example, the time required for beam adjustment could be reduced by a factor of 225 as a result of performing the measurement on 15 × 15 beams simultaneously. In addition, as a result of performing normal drawing after adjusting the deflection distortion, high-precision drawing could be performed.

(Reference Example 1-2)
In the present embodiment, a collimator 23 is provided in the backscattered electron detector 6 of each electron beam optical system as shown in FIG. The collimator 23 in the present embodiment has a cylindrical shape like the embodiment 1-1, but is provided not to the individual backscattered electron detectors 6 but to surround one electron beam optical system. Here, with this multi-beam type electron beam drawing apparatus, positioning was performed on a base pattern formed on a Si substrate.

複数 As shown in FIG. 6, a plurality of chips 25 are arranged on a wafer 26. The chip size is 10 mm square, and alignment marks 24 are arranged at four corners of each chip 25. These marks 24 are concave marks engraved on a Si substrate by light exposure and plasma etching. The size of each mark 24 is 100 μm on one side, the width is 5 μm, and the depth is 2 μm. At the time of drawing, one chip is simultaneously drawn by each electron beam optical system. Positioning is performed as follows.

(4) The wafer position on the stage is confirmed by a wafer alignment mark 27 provided at a different place from the chip 25. Next, a mark position in each chip 25 is calculated from chip layout information on the wafer 26. Based on the calculated mark position of each chip 25, the stage is moved to detect the mark position. In this way, the four mark positions in the chip 25 are sequentially detected. Here, since the chips are arranged at the same pitch as the electron beam optical system, it is possible to detect the mark position simultaneously with 15 × 15 beams without any special operation.

(4) As a result of the simultaneous detection of the alignment marks 24 for 15 × 15 beams, alignment of each electron beam optical system could be performed without any problem. At this time, the time required for one beam adjustment was one minute, and a total of four minutes was required for one chip. In the case of 15 × 15 beams, it took about 12 hours to perform beam adjustment for each beam. In contrast, in this embodiment, 15 × 15 beams were simultaneously performed for 15 × 15 beams. Was reduced by a factor of 225. In addition, as a result of performing normal drawing after the alignment, high-precision drawing could be performed.

(Reference Example 1-3)
In this embodiment, a shield plate 31 having a hole as shown in FIG. 7 was used as a collimator for the backscattered electron detector of each electron beam optical system. Then, the collimator 31 was installed between the sample and the electron beam optical system as shown in FIG. In FIG. 7, 28 is an electron beam passage hole, 29 is an opening for a reflected electron detector, and 30 is a drawing area of the electron beam optical system.

位置 When the alignment drawing was performed using the collimator 31 in the same manner as in Reference Example 1-2, the alignment could be performed without any problem. In addition, as a result of performing normal drawing after the alignment, high-precision drawing could be performed.

Hereinafter, details of the present invention will be described with reference to the illustrated embodiments.

(1st Embodiment)
Next, a first embodiment of the present invention will be described with reference to the flowchart of FIG. Here, for simplicity of description, an electron beam drawing apparatus in which an electron beam source is an 8 × 8 array of 64 in total, as shown in FIGS. 10 and 11, will be described.

First, the present embodiment is characterized by including the following means.

(1) One electron beam optical system is selected from the plurality of electron beam optical systems (S1).

(2) The beam of the selected electron beam optical system is turned off (S2).

{Circle around (3)} Mark detection is sequentially performed by an electron beam optical system other than the selected one (S3).

(4) Measure interference of reflected particles from other marks in the selected electron beam optical system (S4).

(5) The above operation is repeated for all the electron beam optical systems (S5, S6).

(6) The electron beam optical systems having no interference are grouped together (S7).

(7) One of the grouped electron beam optical systems is selected (S8).

(8) A plurality of mark positions are simultaneously detected using the selected electron beam optical system (S9).

(9) The above operation is repeated for all groups (S10, S11).

{Circle around (4)} In the step S4, interference of reflected electrons from other electron beams is measured. For example, when the selected electron beam optical system is 35 in the figure and the drawing area of the electron beam optical system is 34 in the figure, this beam is blanked. At this time, when the mark detection is performed with the electron beams in the column indicated by 36 in the figure, for example, in the case of the adjacent electron beam corresponding to 37 in the figure, the reflected electrons are detected by the electron beam optical system in FIG. It jumps into the vessel (FIG. 10A). On the other hand, in the other electron beam optical systems indicated by reference numeral 38 in the figure, reflected electrons are not detected, or even if detected, the amount is the same level as noise (FIG. 10B).

Next, an electron beam optical system is sequentially selected from the electron beam optical systems in the 39 columns in the figure, and interference of reflected electrons is measured in the same manner (FIG. 10C). Here, for example, it is assumed that reflected electrons interfere in the adjacent electron beam optical system 40 in the figure, but no reflected electrons are detected in the other electron beam optical systems 41 in the figure (FIG. 11D). . In this way, as shown at 43 in the figure, it is possible to obtain the minimum unit in which reflected electrons interfere. In this case, marks cannot be detected at the same time in the area indicated by 43 in the figure, so that it is set to be a different group (34, 37, 40, 42 in the figure) (FIG. 11E).

In the step S7, as shown in FIG. 12, the minimum unit 43 in the figure is applied to the entire electron beam array. As a result, an electron beam group without mutual interference of reflected electrons can be formed into four groups.

グ ル ー プ In the groups obtained in S1 to S7, even if the mark position is detected at the same time, the mark position can be detected without any problem without interference of reflected electrons. In this case, it takes only four times to perform mark detection in all the electron beam optical systems. As a result, the time required for mark detection can be reduced to one sixteenth compared to the case where mark detection is performed for all 64 electron beam optical systems. As a result, beam adjustment and positioning can be performed simultaneously by a plurality of electron beam optical systems, and the drawing time can be greatly reduced. Here, for simplicity of description, the electron beam optical system is an 8 × 8 array. However, even if the electron beam optical system is a larger array of 10 × 10, mark detection is performed similarly. be able to.

Next, a more specific embodiment of the first embodiment will be described.

(Embodiment 1-1)
The schematic configuration of the multi-beam drawing apparatus used in this embodiment is as shown in FIG. The accelerating voltage of this device is 10 kV. The drawable range is 80 mm square, and 8 × 8 pieces at a pitch of 10 mm, that is, a total of 64 electron beam optical systems are arranged. The beam deflection system has a main / sub / two-stage configuration using electrostatic deflection. The size of each deflection area is 500 μm for main deflection and 100 μm for sub deflection. The drawing area of each electron beam is ± 5 mm around the electron gun, and this drawing area is drawn by 400 main deflection areas.

ビ ー ム A beam adjustment mark is provided on the stage as shown in FIG. There are 8 × 8 marks corresponding to each electron beam optical system so as to form a pair, and one mark is provided in the drawing area of each electron optical system. The shape and size of the mark are the same as those described in FIG.

In the present embodiment, the deflection distortion of the multi-beam type electron beam writing apparatus was corrected. First, before the deflection distortion correction, the electron beam optical systems are grouped. This will be described below with reference to FIGS.

1) Select an electron beam optical system (35 in the figure).

2) Blank the beam of this electron beam optical system.

3) Mark detection is performed by the electron beam optical system in the column indicated by 36 in the figure.

# 4) As a result, in the case of the adjacent electron beam optical system corresponding to 37 in the figure, reflected electrons were detected by the reflected electron detector of the electron beam optical system 35 in the figure.

# 5) On the other hand, in the other electron beam optical systems shown in FIG. 38, reflected electrons were hardly detected.

# 6) Next, an electron beam optical system was sequentially selected from the electron beam optical systems in the 39 row in the figure, and interference of reflected electrons was measured in the same manner. Here, reflected electrons interfered in the adjacent electron beam 40 in the figure, but reflected electrons were not detected in the other electron beam optical systems 41 shown in the figure.

7) As a result, the minimum unit of interference of reflected electrons composed of four electron beam writing areas as shown by 43 in FIG. 11D was obtained.

8) The region indicated by reference numeral 43 in the figure is set to be different groups (34, 37, 40, 42 in the figure).

# 9) The minimum unit of 8) was repeatedly arranged in an 8 × 8 array as shown in FIG.

(4) In the manner described above, four groups having 16 electron beam optical systems were created in each group, and the information was stored in the control computer.

(5) Next, deflection distortion correction was performed as follows.

1) As shown in FIG. 4, the main deflection area of 500 μm is divided into 50 μm meshes, and the stage is moved so that the fiducial marks are located on the grid points.

2) Select 16 beams of the first group.

# 3) The 16 beams are simultaneously deflected and scanned on the mark.

4) The deflection voltage at the mark center is calculated from the beam deflection amount and the mark position.

5) Repeat steps 3) to 4) for the second to fourth groups.

# 6) The reference mark is moved in the same manner as 22 in FIG. 4 and the operations 2) to 5) are repeated.

# 7) The same operation as in 1) to 7) is performed for a sub-deflection region having a size of 100 μm square. At this time, the mesh size was 5 μm.

The above operation was first performed simultaneously for each of the 8 × 8 beams for each of the first to fourth groups with 16 beams. As a result, the deflection distortion could be corrected for each electron beam optical system without any problem. . At this time, the time required for one beam adjustment was one minute, and the time required for performing the deflection distortion correction for the 8 × 8 beams for each of the four groups was four minutes. In the present embodiment, it took about 1 hour to perform beam adjustment for each of 8 × 8 beams, but in the present embodiment, it was necessary to correct deflection distortion as a result of simultaneous execution of 8 × 8 beams. The time could be reduced to about 1/16. Further, as a result of performing normal drawing after correcting the deflection distortion, high-precision drawing could be performed.

(Embodiment 1-2)
In the present embodiment, a multi-beam electron beam lithography system is used to perform positioning with respect to a base pattern formed on a Si substrate.

The chip size is 10 mm square, and alignment marks are arranged at the four corners of the chip as shown in FIG. This mark is a concave mark in which a Si substrate is dug by light exposure and plasma etching. The size of the mark is 100 μm on one side, the width is 5 μm, and the depth is 2 μm. At the time of drawing, one chip is simultaneously drawn by each electron beam optical system. Positioning is performed as follows.

First, the wafer alignment mark provided in an area different from the chip is optically detected, and the wafer position on the stage is confirmed. Next, a mark position in each chip is calculated from chip layout information on the wafer. Based on the calculated mark position of each chip, the stage is first moved to measure the first mark position, and the mark position of each chip is sequentially detected for each of the first to fourth groups. Subsequently, the second to fourth mark position measurements were performed in the same procedure. Here, since the chips are arranged at the same pitch as the electron beam optical system, the stage may be moved four times in accordance with the mark positions in the chips.

(4) As a result of simultaneously detecting the alignment marks for 4 groups of 8.times.8 beams, alignment of each electron beam optical system could be performed without any problem. At this time, the time required for one beam adjustment was 15 seconds, and a total of one minute was required for one chip. As a result, the time required for alignment of 8 × 8 beams was 4 minutes. In the present embodiment, it took about one hour to perform beam adjustment for each 8 × 8 beam, whereas in the present embodiment, the time required for alignment was obtained as a result of simultaneous execution for 8 × 8 beams. Was reduced to about 1/16. In addition, as a result of performing normal drawing after the alignment, high-precision drawing could be performed.

(Embodiment 1-3)
In the present embodiment, the grouping of the electron optical systems is performed by simulation on a computer. In actual device fabrication, a GaAs substrate or a sample on which a heavy metal such as W is formed as a sample can be considered. If the electron beam optical systems are grouped by a computer, it is not necessary to perform grouping for a variety of substrates each time the substrate changes.

First, the multi-beam type electron beam writing apparatus used in the present embodiment was reproduced on a computer program. Here, as shown in FIG. 13, only one-dimensional calculation was performed.

First, when the electrons accelerated to 10 kV are incident on the Si substrate, when the mark detection is sequentially performed by the electron beam optical system in the column shown in FIG. 46, the degree of interference with the electron beam optical system 45 in FIG. Was calculated. Here, the backscattered electrons 9 from the closest mark were detected by the backscattered electron detector 45 of the electron beam optical system in the figure. On the other hand, the reflected electron 9 'from the mark other than the nearest neighbor was hardly detected by the reflected electron detector 45 of the electron beam optical system in the figure. As a result of expanding the calculation result in the one-dimensional space into two dimensions, the same grouping as in FIG. 12 could be performed.

In the case of performing grouping by a computer, even when a GaAs substrate or a heavy metal such as W is assumed as a sample, the range of the backscattered electrons can be obtained from the amount and angle data of the backscattered electrons by Monte Carlo calculation. . Therefore, it is no longer necessary to perform grouping for various types of substrates each time the substrate changes.

(4) When the electron beams were grouped by the above method and the alignment drawing was performed in the same manner as in Embodiment 1-2, the alignment could be performed without any problem. In addition, as a result of performing normal drawing after the alignment, high-precision drawing could be performed.

The present invention does not limit the drawing apparatus and the drawing method. In addition to the embodiments described above, the present invention is also applicable to a drawing apparatus of a type in which one beam is divided into a plurality of beams by an aperture. Further, the present invention does not limit the shape and type of the mark. In addition to the above-described embodiment, for example, a convex mark using a heavy metal can be applied. In addition, various modifications can be made without departing from the scope of the present invention.

(Second embodiment)
Next, a second embodiment of the present invention will be described. Here, for simplicity of explanation, an electron beam writing apparatus in which the electron beam source has a total of nine 3 × 3 arrays will be described. At this time, each electron beam optical system is provided with a reference mark corresponding to each electron beam optical system, as shown in FIG. In the figure, 7 is an electron beam, 10 is a mark, 13 is an electron optical system, and 52 is a drawing area by one electron optical system.

It is difficult to make the reference mark position in an ideal arrangement as shown in FIG. Actually, it is distorted as shown in FIG. When such a reference mark is used, when the position of the reference mark is shifted, when one chip is drawn by a plurality of electron beam optical systems, a pattern position shift occurs at the drawing area boundary of each electron beam optical system. I do.

In the present embodiment, the relative displacement of each reference mark is measured by measuring not only the position of the corresponding reference mark of each electron beam optical system but also the position of the reference mark of the adjacent electron beam optical system. ing. For example, it is assumed that when the reference marks in the first row and first column in the drawing are set as the origin, the respective reference marks are shifted as shown in FIG. Note that, here, for ease of explanation, 100 μm is represented as 1.

First, the mark is moved to the center of each electron beam optical system, and the mark position is detected. Next, as shown in FIG. 15, the mark is moved in the Y direction by the pitch of the electron beam optical system, and the position of the reference mark of the adjacent electron beam optical system is measured. Further, the stage is moved in the opposite direction, and the position of the reference mark of the adjacent electron beam optical system is measured. In this way, the amount of shift in the XY direction of the reference mark position between rows can be obtained for each column. In the figure, reference numeral 47 denotes a fixed electron beam arrangement, and reference numeral 48 denotes a moved stage position.

Here, assuming that each electron beam optical system in the first row is a reference (0, 0), the position of the reference mark in the column direction can be expressed as follows.

1st column 2nd column 3rd column 1st row (0,0) (0,0) (0,0)
Second line (1,0) (-1,0) (0,0)
Third line (0,1) (0,1) (1, -1) (× 100 μm)
Next, as shown in FIG. 16, the stage is moved also in the X direction, and the mark position deviation between columns is measured in the same manner as in the case of rows. Here, it is assumed that the positional shift of the reference mark in the first row is expressed as follows with reference to each electron beam optical system in the first column.

1st column 2nd column 3rd column 1st row (0,0) (1,0) (0, -1) (× 100 μm)
By adding this value to the result of the first measurement, the relative position of each reference mark can be obtained with reference to the reference mark in the first row and first column in the figure.

1st column 2nd column 3rd column 1st row (0,0) (1,0) (0, -1)
2nd line (1,0) (0,0) (0, -1)
3rd line (0,1) (1,1) (1, -2) (× 100 μm)
If the position of the drawing area is corrected based on this result, it is possible to reduce the displacement of the pattern at the boundary of the drawing area due to the difference in the reference mark of each electron beam optical system. In the above example, in order to make the relative displacement of the reference mark zero, the drawing position may be corrected as follows.

1st column 2nd column 3rd column 1st row (0,0) (-1,0) (0,1)
2nd line (-1, 0) (0, 0) (0, 1)
3rd line (0, -1) (-1, -1) (-1,2) (× 100 μm)
The correction of the drawing position is performed by changing the amount of beam deflection in each electron beam optical system. As a result, as shown at 56 in FIG. 17, the corrected drawing position can be adjusted without overlapping the drawing area of the adjacent electron beam optical system. In the drawing, 55 is a drawing position before correction, and 56 is a drawing position after correction.

In this way, it is possible to improve the connection accuracy even at the drawing area boundary of each electron beam optical system. In addition, since adjustment of beam deflection distortion and mark detection of each electron beam optical system may be performed for each electron beam optical system, the drawing throughput of the multi-beam drawing apparatus can be improved. In addition. Here, for the sake of simplicity, the electron beams are arranged in a 3 × 3 array. However, even in an array of 100 × 100 larger electron beams, the drawing area can be similarly corrected. .

Next, a more specific embodiment of the second embodiment will be described.

(Embodiment 2-1)
The schematic configuration of the multi-beam drawing apparatus used in this embodiment is as shown in FIG. The configuration of each electron beam optical system is the same as in FIG.

加速 The accelerating voltage of this drawing apparatus is 10 kV. The drawable range is 80 mm square, and 8 × 8 pieces at a pitch of 10 mm, that is, a total of 64 electron beam optical systems are arranged. The beam deflection system has a main / sub / two-stage configuration using electrostatic deflection. The size of each deflection area is 500 μm for main deflection and 100 μm for sub deflection. The drawing area of each electron beam optical system is ± 5 mm around the electron gun, and this drawing area is drawn by 400 main deflection areas.

When the mark position is detected, the information is sent to the control computer and stored. After the detection of the mark, the displacement of each reference mark is calculated based on the stored mark position information. Thereafter, the position of the drawing area of each electron beam optical system is corrected, and the correction information is sent to the control circuit. At the time of drawing, the drawing data is sent from the control computer to the drawing control circuit of each electron beam optical system. At this time, the drawing position is corrected based on the correction data of the drawing area.

ビ ー ム A beam adjustment mark is provided on the stage as in FIG. FIG. 14 is represented by a 3 × 3 array, and there are 8 × 8 marks corresponding to each electron beam optical system so as to form a pair with each electron beam optical system, and one mark is provided in the drawing area of each electron beam optical system. Provided. The mark has a cross shape as shown in FIG. 27, and was formed by excavating a Si substrate by light exposure and plasma etching. The size of the mark is 100 μm on one side, the width is 5 μm, and the depth is 2 μm.

描画 In the present embodiment, an 80 mm square photomask was drawn. First, in each electron beam optical system, distortion of the main and sub deflection areas was corrected using the respective reference marks. Next, the correction of the drawing area of each electron beam optical system was performed as follows.

1) First, the mark is moved to the vicinity of the center of each electron beam optical system, and the position of the mark is detected.

2) Next, as shown in FIG. 18A, the mark is moved in the Y direction by the pitch of the electron beam optical system (10 mm), and the position of the reference mark of the adjacent electron beam optical system is measured. In the drawing, reference numeral 51 denotes an electron gun, and reference numeral 52 denotes a drawing area by one electron gun.

3) This time, the stage is moved by -10 mm in the direction opposite to that of 2), and the position of the reference mark of the adjacent electron beam optical system is measured. This makes it possible to determine the amount of shift in the X and Y directions of the reference mark position for each column. Here, as shown in FIG. 18B, the position of the reference mark in the column direction was calculated with reference to each electron beam optical system in the first row indicated by 53 in the figure.

4) Next, the stage is returned to the original position, the mark is moved by 10 mm in the X direction as in the Y direction, and the position of the reference mark of the adjacent electron beam optical system is measured.

5) Similarly to 3), the stage is moved by 10 mm in the opposite direction, and the reference mark position of the adjacent electron beam optical system is measured. Here, the position of the reference mark in the row direction was calculated with reference to each electron beam optical system in the first column.

6) By the above operations 1) to 5), the relative positions of the respective reference marks could be obtained.

7) The drawing area position of each electron beam optical system was calculated in the same manner as in FIG. 17 so as to offset the relative displacement of the reference mark.

8) The above calculation results were converted into beam deflection data of each electron beam optical based on the measurement data of the beam deflection distortion of each electron beam optical, and stored in the control circuit.

In actual writing, the drawing data of the photomask is divided in advance in the control computer in accordance with the drawing area of each electron beam optical system.

When drawing data is transferred to each electron beam optical system for each main deflection area, the control circuit moves the stage and performs drawing by adding correction data of a previously stored drawing position to the sent drawing data. . In this way, the stage was moved for each main deflection area, and writing was simultaneously performed by 8.times.8 electron optical systems.

描画 As a result of drawing as described above, the connection accuracy was improved at the drawing region boundary of each electron beam optical system, and high-precision drawing could be performed. In addition, since the adjustment of the beam deflection distortion and the mark detection of each electron beam optical system may be performed for each electron beam optical system, the time required for the beam adjustment of the multi-beam drawing apparatus can be greatly reduced.

In the above embodiment, the electron beams are arranged in an array of 8 × 8, but the present invention does not limit the number of electron beam arrays. In addition to the embodiments described above, the present invention can be used in an electron beam writing apparatus having 100 × 100 electron beam arrays. Further, the present invention does not limit the drawing apparatus and the drawing method. In addition to the above-described embodiment, the present invention is also applicable to a drawing apparatus of a type in which one beam is divided into a plurality of beams by an aperture. Further, the present invention does not limit the shape and type of the mark. In addition to the above-described embodiment, for example, a convex mark using a heavy metal can be applied. In addition, various modifications can be made without departing from the scope of the present invention.

(Third embodiment)
Next, a third embodiment of the present invention will be described. As shown in FIG. 24, each electron beam optical system has a drawing area that overlaps a drawing area of an adjacent electron beam optical system. At this time, the dose correction is performed so that the portion where the two regions overlap is drawn at a dose of 1/2, and the portion where the four regions are overlapped is drawn at a dose of 1/4. These steps make it possible to improve the drawing accuracy.

Next, a more specific embodiment of the third embodiment will be described.

(Embodiment 3-1)
The schematic configuration of the multi-beam drawing apparatus used in this embodiment is as shown in FIG. In this writing apparatus, the reference position is when each electron beam source is at the upper left end of each writing area.

試 料 As shown in FIG. 19A, a beam adjustment mark 103 is provided on the sample 101. The mark has a cross shape as shown in FIG. 19B, and is formed by engraving a Si substrate by light exposure and plasma etching. The size of the mark is 10 μm on one side, the width is 1 μm, and the depth is 2 μm.

描画 The drawing area of this drawing apparatus is 154 mm square, and 3 × 3 units at a pitch of 50 mm, that is, a total of 9 electron beam sources are arranged. The beam has two main and sub-stage deflections. The size of each deflection area is 6 mm for main deflection and 2 mm for sub deflection. The drawing area of each beam is ± 27 mm around the charged beam source. The drawing area is divided into 81 main deflection areas for drawing.

で は In this embodiment, a 150 mm square photomask is drawn. Prior to drawing, mask data was converted so that one mask was drawn by a plurality of electron beam sources. Multiple writing is performed in units of sub-deflection areas. First, mask data is divided into nine areas at the pitch of each electron beam source. As shown in FIG. 20, data having a width corresponding to one sub-deflection region is added to the periphery of the periphery to obtain drawing data for one electron beam source. This data is divided into a main deflection area and further into a sub deflection area, and is converted into bit data. In the figure, 71 is the size of the mask, 72 is the drawing area, 73 is the main deflection area, and 74 is the sub deflection area.

At the time of data conversion, a region to be drawn twice (85, 86, 87, 88 in the figure) separately from a region to be drawn with a normal exposure amount like the portions 81, 82, 83, 84 in FIG. , 89), the data for setting the dose is provided in the areas (810, 811 in the figure) to be drawn four times. That is, the dose correction is performed so that the portion where the two regions overlap is drawn at a half dose and the portion where the two regions overlap is drawn at a dose of one quarter. As a result, even in a region where multiple writing is performed, the irradiation amount is equal to that of a region having no overlap.

Subsequently, the deflection distortion of each charged beam was adjusted. The deflection distortion adjustment was performed as follows.

1) As shown in FIG. 22, the main deflection area of 6 mm is divided into meshes of 500 μm, and the stage is moved so that the reference mark comes on the grid point. In the drawing, reference numeral 121 denotes a main deflection area, and reference numeral 122 denotes a reference mark.

2) For nine beams, the beams are sequentially deflected to detect mark positions.

3) The reference mark is moved and the operations 1) to 2) are repeated.

# 4) The same operation as in 1) to 3) is performed also on the sub-deflection area of 2 mm square. The size of the mesh was 50 μm.

Subsequently, drawing was performed. First, the stage was moved to the reference position, and the first main deflection area of each charged beam source was drawn. First, drawing was performed on the main deflection region as indicated by 91 in FIG. 23, and then the stage was moved rightward by 6 mm, and drawing was performed on the second main deflection region in the same manner. Hereinafter, drawing was performed sequentially according to 92 in the figure.

As a result of the above, a pattern could be formed with high connection accuracy in the deflection boundary region of each charged beam source.

Note that the present invention does not limit the drawing apparatus and the drawing method. In addition to the above-described embodiment, the present invention is also applicable to a drawing apparatus of a type in which one beam is divided into a plurality of beams by an aperture. Further, the present invention does not limit the shape and type of the mark. In addition to the above-described embodiment, for example, a convex mark using a heavy metal can be applied. In addition, various modifications can be made without departing from the scope of the present invention.

FIG. 2 is a diagram illustrating an optical system of an electron beam writing apparatus according to a reference example. FIG. 9 is a diagram illustrating an effect when mark detection is performed using a plurality of beams. The figure which shows the schematic structure of the electron beam drawing apparatus concerning Reference Example 1-1. The figure which shows the shape of the beam adjustment mark in Reference Example 1-1. The figure which shows the schematic structure of the electron beam drawing apparatus concerning Reference Example 1-2. The figure which shows the relationship between the chip in Example 1-2, and an alignment mark. The figure which shows the structure of the collimator in Reference Example 1-3. The figure which shows the arrangement | positioning of the electron beam optical system in Example 1-3, and a collimator. FIG. 3 is a diagram illustrating a procedure of a drawing method according to the first embodiment. FIG. 5 is a diagram showing a procedure for grouping electron beam optical systems according to the embodiment 1-1. FIG. 5 is a diagram showing a procedure for grouping electron beam optical systems according to the embodiment 1-1. FIG. 3 is a diagram illustrating a state of electron beams grouped. The figure which shows the structure of the multi-beam drawing apparatus reproduced on the computer program. FIG. 8 is a diagram illustrating a state of mark detection according to the second embodiment. The figure which shows the position measuring method of a reference mark. The figure which shows the position measuring method of a reference mark. FIG. 9 is a diagram for explaining the effect of drawing position correction. FIG. 9 is a diagram showing a method for measuring the position of a reference mark in the embodiment 2-1. FIG. 4 is a diagram showing a beam adjustment mark on a stage and its position. FIG. 3 is a diagram showing a drawing area per one electron beam source string. FIG. 4 is a diagram showing overlapping of drawing areas of each electron beam source. FIG. 9 is a diagram showing division of a main deflection area when adjusting deflection distortion. FIG. 4 is a diagram illustrating a drawing order in a drawing area. FIG. 3 is a diagram illustrating an example of multiple drawing. FIG. 4 is a diagram illustrating beam deflection distortion. The figure which shows the conventional electron beam optical system. The figure which shows the planar shape and sectional shape of a mark. The figure which shows a mode of mark detection. The figure which shows the problem at the time of performing mark detection with a some beam. FIG. 3 is a diagram illustrating a drawing method of a multi-beam electron beam drawing apparatus. FIG. 7 is a diagram illustrating an ideal arrangement of reference marks and a state of positional deviation of a mark that is actually assumed. FIG. 4 is a diagram illustrating a state of a position shift of a drawing area due to a position shift of a reference mark. FIG. 5 is a diagram illustrating a state of a position shift at a drawing area boundary of the electron beam optical system.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Electron gun 2a, 2b, 2c ... Beam adjustment lens system 3 ... Blanking deflector 4 ... Blanking aperture 5a, 5b ... Beam deflection system 6 ... Reflection electron detector 7 ... Electron beam 8 ... From corresponding mark 9 reflected electrons from other marks 10 reference marks 11 and 23 collimator 13 electron beam optics 14 sample 15 sample chamber 16 stage 17 reference mark 18 control circuit 19 control computer 24 ... Chip alignment mark 25 ... Chip 26 ... Wafer 27 ... Wafer alignment mark 28 ... Electric beam passage hole 29 ... Opening for reflected electrons 30 ... Drawing area 31 ... Shielding plate (collimator)

Claims (4)

In a multi-beam charged beam drawing apparatus having a plurality of charged beam optical systems,
A reference mark group provided on the sample table corresponding to a plurality of charged beam optical systems, means for moving the reference mark group by moving on the sample table, and scanning the charged reference mark with the charged beam, Means for measuring the position of each fiducial mark, means for storing the relative positional relationship of each measured fiducial mark, and the drawing area of each charged beam based on the stored relative positional relationship of each fiducial mark. A charged beam drawing apparatus comprising: means for correcting a position; and means for performing drawing based on the corrected drawing position. A multi-beam type charged beam writing apparatus having a plurality of charged beam optical systems, wherein a writing position is corrected by using a reference mark group provided on a sample table corresponding to each charged beam optical system. In the charged beam drawing method,
A step of performing mark position detection with a plurality of charged beam optical systems, a step of performing mark position detection using a reference mark of an adjacent charged beam optical system, and a step of calculating a relative positional relationship of a reference mark group, A charged beam drawing method, comprising: a step of correcting a position of a drawing area of each charged beam optical system based on the calculation result; and a step of drawing at the corrected drawing position. In a multi-beam type charged beam writing method of writing using a plurality of charged beam sources,
A charged beam drawing method, wherein drawing is performed so that deflection boundary areas of adjacent charged beam sources overlap each other. 4. The charged beam drawing method according to claim 3, wherein the irradiation amount of the overlapping area is corrected.

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