JP2004071691A - Multi-beam measurement method and multi-beam device - Google Patents

Abstract

Provided is a beam measurement technique for realizing, at high speed, beam characteristic measurement and arrangement interval between beams in a multi-beam apparatus.
In a method for measuring the beam characteristics of charged particle beams arranged vertically and horizontally at predetermined intervals, a linear measurement mark (2) perpendicular to the scanning direction of the charged particle beam is provided, and Of the charged particle beams arranged in the vertical and horizontal directions at the predetermined interval, only the beam (1) having a specific arrangement is selectively scanned on the measurement mark (2), and the charged particles are obtained by using the obtained signal. Measure the beam characteristics of the beam.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a measurement technique for evaluating beam characteristics in a multi-beam device using a multi-electron beam or the like.
[0002]
[Prior art]
Conventionally, for example, for electron beam measurement, a Faddy cup provided on a stage and having a large opening of about several millimeters has been used.
[0003]
Alternatively, in the case of a multi-electron beam apparatus having a plurality of electron beams, as described in Japanese Patent Application Laid-Open No. H8-191042, each barrel has an optical system independently from a plurality of electron guns and an electron beam barrel. The measurement has been performed using the mark corresponding to each beam on a one-to-one basis.
[0004]
[Problems to be solved by the invention]
In order to increase the processing speed of the electron beam device, a multi-beam system (multi-electron beam device) for simultaneously performing drawing or length measurement using a plurality of beams is required. However, in such a multi-beam system, fine electron beams are arranged at high density in a small area, and since each passes through an individual electron optical system, beam measurement must be performed individually for each beam. . If such a multi-beam is measured using one Faraday cup, it takes a long time to perform the measurement one by one.
[0005]
On the other hand, JP-A-8-191042 discloses a system in which a plurality of lens barrels and a mark and a Faraday cup facing the lens barrel are arranged. And secondary electrons can be measured individually.
[0006]
However, in a high-density array configuration in which the beam interval between multiple beams is narrow, even if a plurality of detectors are prepared, it is not possible to separate and measure reflected electrons and secondary electrons generated from adjacent marks. It becomes possible.
[0007]
Furthermore, if the plurality of mark arrangements are at the same interval as the multi-beam arrangement, the multi-beams are simultaneously irradiated onto the marks during beam scanning, so that reflected electrons and secondary electrons are simultaneously generated from each mark. This makes it difficult to obtain individual characteristics of each beam from the signal from each mark. Also, with this method, it is difficult to measure the interval between each beam.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a beam measurement technique for realizing a beam characteristic measurement and an arrangement interval between beams at high speed in a multi-beam apparatus.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, as a method of measuring a multi-electron beam having a high-density array, a mark having a linear shape perpendicular to the beam scanning direction is prepared, and a specific one of the multi-electron beams having the high-density array is specified. Beam measurement is performed by selectively irradiating only the beam in the row to the mark.
[0010]
When a secondary particle such as a reflected electron or a secondary electron is used as the detection signal, one linear mark perpendicular to the beam scanning direction is prepared. By scanning a specific row of beams selectively turned on on this mark, the characteristics of each beam are separated by a time interval corresponding to the beam interval, and each beam signal is separated into reflected electron and secondary electron signals. Measurement can be performed with one signal detector.
[0011]
The information obtained at this time is the current amount of each beam, its beam profile, and the arrangement interval between each beam. In addition, measurement of all multi-electron beams composed of high-density arrays can be realized by repeating the above-described measurement for each array.
[0012]
Alternatively, in the present invention, as a method of measuring a multi-electron beam of a high-density array, a plurality of linear marks perpendicular to the beam scanning direction are prepared, and only a beam of a specific column of the multi-electron beam of the high-density array is prepared. Is selectively irradiated on the mark to perform beam measurement.
[0013]
When a secondary particle such as a reflected electron or a secondary electron is used as the detection signal, the mark interval is set to a value different from the arrangement interval (design pitch dimension) of the specific row of the multi-electron beam or an integral multiple thereof. By doing so, when a beam in a specific column selectively turned ON on this mark is scanned, it is possible to measure each beam signal as a separated signal by one signal detector. If the intervals between the linear marks are obtained in advance by a method such as a coordinate measuring machine, the arrangement interval between the beams can be obtained. The information obtained at this time is the current amount of each beam, its beam profile, and the arrangement interval between each beam.
[0014]
Alternatively, in the present invention, as a method for measuring a multi-electron beam having a high density array, a single linear opening mark (or knife edge) perpendicular to the beam scanning direction is prepared, and a deep hole is provided immediately below the opening mark. For example, a Faraday cup is installed, and only a beam in a specific column among the multi-electron beams having the high-density arrangement is selectively irradiated on the mark to perform beam measurement.
[0015]
In this case, the amount of current absorbed by the Faraday cup is measured as a detection signal. When a beam in a specific column selectively turned on on this mark is scanned, the amount of current absorbed by the Faraday cup as a separated signal of each beam signal can be measured. The information obtained at this time is the current amount of each beam, its beam profile, and the arrangement interval between each beam.
[0016]
Alternatively, in the present invention, as a method for measuring a multi-electron beam having a high-density arrangement, a plurality of linear opening marks perpendicular to the beam scanning direction are prepared, and a Faraday cup is installed immediately below the opening marks, and Beams are measured by selectively irradiating only the beams in a specific column from the array of multi-electron beams onto the mark.
[0017]
In this case, the amount of current absorbed by the Faraday cup is measured as a detection signal. When a beam in a specific column selectively turned on on this mark is scanned, the amount of current absorbed by the Faraday cup as a separated signal of each beam signal can be measured. If the intervals between the linear marks are obtained in advance by a method such as a coordinate measuring machine, the arrangement interval between the beams can be obtained. The information obtained at this time is the current amount of each beam, its beam profile, and the arrangement interval between each beam.
[0018]
In each of the examples, the case of using a multi-electron beam has been described. However, in the present invention, a similar effect can be obtained with another charged particle beam such as an ion beam.
[0019]
Hereinafter, typical configuration examples of the present invention will be listed.
[0020]
The multi-beam measurement method of the present invention includes a step of preparing at least one measurement mark having a linear shape substantially perpendicular to a scanning direction of a plurality of charged particle beams two-dimensionally arranged at a predetermined interval; Selectively scanning a plurality of beams belonging to a desired arrangement among the charged particle beams on the mark; and detecting a secondary particle signal obtained from the mark by scanning using a single detector. Measuring the beam characteristics of the charged particle beam using the detected signal, wherein the selected desired arrangement is sequentially shifted and measured.
[0021]
Further, the multi-beam measurement method of the present invention provides at least one aperture mark having a linear shape substantially perpendicular to the scanning direction of a plurality of charged particle beams two-dimensionally arranged at a predetermined interval, and Installing a Faraday cup below the opening mark corresponding to the opening mark, selectively irradiating the mark with a plurality of beams belonging to a desired arrangement among the plurality of charged particle beams, and scanning the mark; Scanning the top to measure the amount of current absorbed by the Faraday cup, and measuring the beam characteristics of the charged particle beam by the detected amount of current, the beam of the desired arrangement It is characterized in that measurement is performed by selectively shifting sequentially.
[0022]
Further, the multi-beam device of the present invention is configured to generate a plurality of charged particle beams two-dimensionally arranged at a predetermined interval, and to independently generate each of the plurality of charged particle beams according to pattern data to be drawn. Means for on / off control, means for deflecting and scanning the charged particle beam on / off controlled collectively on the sample, and at least one linear shape substantially perpendicular to the scanning direction of the plurality of charged particle beams by the deflection scanning means. And a detector for detecting a secondary particle signal obtained by scanning over the measurement mark, and selectively marks a plurality of beams belonging to a desired arrangement among the plurality of charged particle beams. The apparatus is characterized in that a beam characteristic of the charged particle beam is measured using the secondary particle signal detected by scanning upward.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0024]
One embodiment of the present invention will be described with reference to FIGS. In the multi-electron beam drawing system as shown in FIG. 4, an electron beam 202 generated from an electron gun 201 is irradiated as a parallel beam by a lens 203 onto an aperture 204, and shaped into a multi-point beam by a lens 205. These beams 206 can be independently and selectively controlled on / off by the blanker electrode 207 and the stop 208 to be passed to an optical system thereafter or absorbed and stopped by the stop 208. The intermediate image 209 of the beam selectively passed through the stop 208 in this manner is irradiated as a point beam narrowed to a desired position on the sample 217 by the lenses 210 and 214 and the deflectors 211, 212, 213 and 215. And be deflected.
[0025]
The control of these electron optical systems is performed by the control circuits 220, 221, 222, and 223, and the positioning of the sample is performed by driving the stage 218 by the control circuit 225. For beam positioning, the reflected electron signal from the mark substrate 217 is detected and calibrated by the detector 216 and the detection circuit 224. These control circuits and detection circuits are collectively managed by the overall control system 226.
[0026]
As shown in FIG. 2, the point beams 1 are arranged vertically and horizontally (two-dimensionally) at predetermined intervals on the sample, and can be turned on and off independently.
[0027]
Since these point beams are arranged at a high density at a pitch of about 2 μm, one-to-one marks are prepared for each beam as described in Japanese Patent Application Laid-Open No. Even if a plurality of backscattered electron detectors are prepared for this beam, since the arrangement of the point beams is high, electrons reflected from each mark enter the detector in this system because of the high density. Therefore, separated beam information cannot be obtained.
[0028]
Therefore, in the present invention, as shown in FIGS. 1, 2 and 4, the aluminum thin film 3, which is a light metal, is formed on the common detectors 6, 216 and the mark (silicon) substrates 4, 227, and then a straight line is formed. A sample provided with the mark (for example, tungsten) 2 is prepared, and only the four beams in the third row from the top in the multi-beam arrangement are turned on as shown in FIG. Then, these beams are simultaneously deflected by the deflectors 211, 212, 213, and 215 so as to be orthogonal to the mark 2.
[0029]
As a result, reflected electrons 5 generated when each beam crosses the mark 2 are detected by the detectors 6 and 216, and a current waveform 7 as shown in FIG. 3 is obtained. The signals from the four beams appear as four current waveforms 7 according to the beam deflection amounts, and the intervals between the multi-beams are obtained at the peak intervals of each waveform. Further, the current distribution of each beam, that is, the beam diameter is obtained from the rise and fall of each waveform.
[0030]
In this measurement, the beam in the third row from the top of the multi-beams was measured. However, all the beams can be evaluated by sequentially measuring the desired arrangement.
[0031]
When the vertical beam interval is to be obtained, a tungsten mark in the horizontal direction (on the paper surface) is prepared in the same manner as in FIG. It can be measured by deflecting in the direction (on the paper).
[0032]
Next, another embodiment of the present invention will be described with reference to FIGS. In this embodiment, a plurality of linear marks are used unlike the above embodiment. As a beam detecting means, the reflected electrons from the heavy metal mark are measured by a reflected electron detector in the same manner as in the above embodiment. In this method, a plurality of linear marks 2 as shown in FIG. 9 are used. The structure of each mark is formed of a linear tungsten mark 2 on which an aluminum thin film 3 as a light metal is formed on silicon substrates 4 and 227 in the same manner as the above mark. The interval (m) between these marks is set to a value different from the beam interval measurement to be measured. In the case of FIG. 9, since the design value of the beam interval is 2 μm, the mark intervals (m) are arranged at 2.1 μm intervals larger than 2 μm by 0.1 μm.
[0033]
In the measurement, only the four beams in the third row from the top are turned ON as shown in FIG. 9 in the multi-beam array. Then, these beams are deflected simultaneously by the deflectors 211, 212, 213, and 215 so as to be orthogonal to the plurality of marks 2. As a result, reflected electrons generated when each beam crosses each mark 2 are detected by the detectors 6 and 216, and a current waveform 7 as shown in FIG. 10 is obtained. At this time, the beam that first crosses the mark is the rightmost beam in FIG. 9, and other beams have not yet reached the mark. Next, when the second beam from the right reaches the mark, the rightmost beam has passed the mark, and the other beams have not yet reached the mark. By keeping the beam interval and the mark interval from being equal in this way, the reflected electron signal from each beam can be temporally separated and measured by one detector.
[0034]
Therefore, as shown in FIG. 10, the signals from the four beams appear as four current waveforms 7 according to the beam deflection amounts, and by adding the mark interval (m) to the peak interval (p) of each waveform, , An accurate multi-beam interval (b) is obtained. Further, the current distribution of each beam, that is, the beam diameter is obtained from the rise and fall of each waveform.
[0035]
In the measurement of the first embodiment, the amount of beam deflection in one measurement requires the number of beams in a row × the beam interval, whereas the amount of beam deflection required in this measurement can be as large as the beam interval. Therefore, the measurement is completed in a shorter time than in the first embodiment. In this measurement, the beam in the third row from the top among the multiple beams was measured, but all the beams can be evaluated by sequentially measuring the desired arrangement.
[0036]
In the case of obtaining the beam interval in the vertical direction, similarly, in FIG. 9, a tungsten mark in the horizontal direction (on the paper surface) is prepared, and beams having a desired arrangement in the vertical direction are selectively shown in FIG. 9. It can be measured by deflecting in the vertical direction (on the paper). A similar effect can be obtained with a grid-like mark in which these marks are crossed vertically and horizontally.
[0037]
Further, another embodiment of the present invention using a method different from the above will be described with reference to FIGS. Here, a measurement method based on an absorption current using a Faraday cup is used as the beam detection means.
[0038]
In this method, instead of the above-mentioned mark and the backscattered electron detector, deep holes, for example, Faraday cups 8 arranged at intervals equal to or an integral multiple of the multiple beam intervals as shown in FIGS. I do. Each Faraday cup 8 is electrically separated by an oxide film thin film 15 on a silicon substrate 16, and a deep hole 12 is formed in a heavy metal absorbing member 14 such as gold, tungsten, or tantalum. Above the deep hole 12, a thin wire (or knife edge) 11 of a cross-shaped heavy metal such as gold, tungsten, or tantalum is formed on the surface with an insulating film 13 interposed therebetween. The Faraday cup 8 is provided with wirings 9 and 18, respectively, and these wirings are independently connected to an ammeter (not shown).
[0039]
The minimum unit of the Faraday cup interval depends on the accelerating voltage of the electron beam to be measured. When the accelerating voltage is 50 kV or more, the interval of 2 μm or more is required even if a heavy metal material is used. Therefore, in the case of a multi-beam having an acceleration voltage of 50 kV or more and the interval is 2 μm or less, Faraday cups arranged at an integer multiple thereof are prepared, and only the beam facing the Faraday cup is selectively turned on. .
[0040]
In the case of FIG. 5, since the beam of the acceleration voltage of 50 kV is arranged in 4 columns and 4 rows at intervals of 6 μm, the Faraday cups 8 are arranged in opposition to the array of 4 columns and 4 rows at intervals of 6 μm. Then, it was prepared on the mark substrate 227 shown in FIG. The distance between the arrangement of the fine cross line provided on the Faraday cup and the fine cross line provided on the adjacent Faraday cup is determined in advance with a precision of about 1 nm using a coordinate measuring machine equipped with a laser interferometer.
[0041]
In the beam measurement, the multi-electron beam 10 is simultaneously deflected by the sub deflector 215 so that the thin line 11 on the Faraday cup 8 is orthogonal as shown by an arrow in FIG. In this measurement, unlike the first embodiment, the deflection width is not required to be as large as the selected beam arrangement width, and only needs to be the opening of the deep hole 12 of the Faraday cup. Therefore, the beam measurement can be performed only by the sub deflector 215. is there.
[0042]
When the beam is irradiated in this manner, the beam 10 incident on the Faraday cup 14 is absorbed by the deep hole 12 and the reflected electrons 17 are similarly confined in the Faraday cup 14 as shown in FIG. The accurate beam current is measured by the current measurement of the above. Next, when this beam is deflected, the beams 100 and 101 are interrupted by the thin line 11, and the beam current is absorbed by the thin line. At this time, the values measured by the ammeter connected to the wirings 9 and 18 from the Faraday cup were as shown in FIGS. 8A and 8B. As a result, the difference between the beam position X1 of the minimum current value on the wiring 18 as shown in FIG. 8A and the beam position X2 of the minimum current value on the wiring 9 as shown in FIG. The distance between the beams 100 and 101 can be accurately determined by adding the previously determined distance (α in FIG. 5) between the cross hairs provided on the Faraday cup.
[0043]
At the same time, from the measurement results shown in FIGS. 8A and 8B, since the maximum values of the beam current values 19 and 20 are the same, the beam current amounts do not change. Since the steepness of the beam 100 differs between the beam current values 19 and 20, it was found that the blur amount of the beam 100 was large. Therefore, the blur of the beam 100 could be adjusted to be the same as the beam current value 19 by changing the set value of the lens 205 by the control circuit 220. Similarly, measurements and adjustments were made for the other beams.
[0044]
Compared to measuring each beam with one Faraday cup by the conventional method, the measurement method according to the present invention was capable of 16 times faster measurement.
[0045]
In addition, since several beams to several beams can be measured in one measurement, all the beams can be measured in a short time.
[0046]
In the above-described embodiment, two examples have been described. In any case, high-speed measurement can be performed several times to several tens times as compared with the conventional method of sequentially measuring each beam. In addition, a signal obtained by measurement can obtain independent data for each beam, so that the accuracy is high. Further, in each of the examples, the embodiment using the multi-electron beam has been described. However, the same effect can be obtained with another charged particle beam such as an ion beam.
[0047]
In the second embodiment, the arrangement density of the Faraday cup depends on the acceleration voltage of the beam to be measured in the second embodiment, whereas the first embodiment does not depend on the acceleration voltage of the beam. Which of the two can perform higher-speed measurement depends on the arrangement of the multi-beams and the accelerating voltage, but it is also possible to prepare both marks and use the two measurement methods together.
[0048]
Hereinafter, configuration examples included in the present invention will be listed.
[0049]
(1) In a method for measuring the beam characteristics of charged particle beams arranged vertically and horizontally at regular intervals, a linear measurement mark perpendicular to the scanning direction of the charged particle beams is provided, and the vertical and horizontal directions are arranged at the regular intervals. A beam scanning device configured to selectively scan only the beams of a specific arrangement among the charged particle beams arranged on the measurement mark on the measurement mark, and to measure a beam characteristic of the charged particle beam by using a signal obtained. Beam measurement method.
[0050]
(2) The multi-beam measurement method according to the above (1), wherein the specific array is a beam train on a straight line forming a certain angle in the scanning direction.
[0051]
(3) The multi-beam measurement method according to (1), wherein the specific array is a beam in a column perpendicular to a scanning direction.
[0052]
(4) The multi-beam measurement method according to the above (1), wherein the specific arrangement is a beam in a horizontal row in the scanning direction.
[0053]
(5) The multi-beam measurement method according to (1), wherein the measurement mark according to (1) is a linear minute opening, a deep hole is provided directly below the opening, and the amount of current absorbed by the deep hole is measured. .
[0054]
(6) The measurement mark according to (1) is a heavy metal pattern having an atomic number larger than that of linear tantalum on a light element substrate or a light element thin film having an atomic number smaller than silicon, and the heavy metal pattern during beam scanning. A multi-beam measurement method characterized in that measurement is performed by means for detecting reflected electrons or secondary electrons from the object.
[0055]
(7) The beam characteristic to be measured is a beam profile, and a knife edge is provided on the deep hole, and the amount of current absorbed by the deep hole when the charged particle beam is scanned on the knife edge is measured. (5) The multi-beam measurement method according to the above (5).
[0056]
(8) A plurality of the linear measurement marks at a predetermined interval, and the mark interval is a value different from the arrangement interval of the charged particle beams and an integer multiple thereof. ) Described multi-beam measurement method.
[0057]
【The invention's effect】
According to the present invention, in a high-density array multi-beam measurement, high-speed, high-accuracy charged particle beam measurement corresponding to a multi-beam can be realized by using a linear mark and a specific array beam selection.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the configuration of an embodiment of charged particle beam measurement according to the present invention.
FIG. 2 is a top view illustrating a relationship between a beam and a mark according to the embodiment of the present invention.
FIG. 3 is a diagram showing a measurement result according to the embodiment of the present invention.
FIG. 4 is a schematic diagram illustrating an example of a multi-electron beam drawing system used in the present invention.
FIG. 5 is a top view illustrating a Faraday cup array for multi-beam measurement used in still another embodiment of the present invention.
FIG. 6 is an enlarged view showing an example of a Faraday cup used in the embodiment of FIG.
FIG. 7 is a sectional view showing a Faraday cup array for multi-beam measurement used in the embodiment of FIG. 5;
FIG. 8 is a view showing a measurement result according to the embodiment of FIG. 5;
FIG. 9 is a top view illustrating a relationship between a beam and a mark according to another embodiment of the present invention.
FIG. 10 is a view showing a measurement result according to the embodiment of FIG. 9;
[Explanation of symbols]
1, 10, 100, 101, 202: electron beam, 2: heavy metal mark, 3: aluminum thin film, 4, 16: silicon substrate, 5, 17: scattered electrons, 6, 216: detector, 7, 19, 20 ... Current waveform, 8, 14: Faraday cup, 9, 18, wiring, 11: thin metal wire, 12: deep hole of Faraday cup, 13, 15: insulating film, 201: electron gun, 203: condenser lens, 204: aperture array, 205: lens array, 206: separated electron beam, 207: blanking array, 208: blanking stop, 209: intermediate image, 210: first projection lens, 211: dynamic focus corrector, 212: dynamic non-control Point corrector, 213: main deflector, 214: second projection lens, 215: sub deflector, 217: sample, 218: sample stage, 220: focus control Road, 221 ... dose control circuit, 222 ... lens control circuit, 223 ... deflection control circuit, 224 ... signal processing circuit, 225 ... stage control circuit, 226 ... CPU, 227 ... mark substrate.

Claims (5)

Preparing at least one measurement mark having a linear shape substantially perpendicular to the scanning direction of the plurality of charged particle beams two-dimensionally arranged at predetermined intervals; and providing a desired arrangement among the plurality of charged particle beams. Selectively scanning a plurality of beams belonging to the mark, scanning the secondary particle signal obtained from the mark using a single detector, and using the detected signal. Measuring a beam characteristic of the charged particle beam, wherein the selected desired arrangement is sequentially shifted and measured. 2. The multi-unit according to claim 1, wherein a plurality of the linear measurement marks are arranged at a predetermined interval, and the interval between the marks has a value different from an arrangement pitch of the plurality of charged particle beams. Beam measurement method. At least one opening mark having a linear shape substantially perpendicular to the scanning direction of a plurality of charged particle beams two-dimensionally arranged at predetermined intervals is prepared, and a Faraday cup is provided below the opening mark corresponding to the opening mark. Installing, a step of selectively irradiating a plurality of beams belonging to a desired arrangement of the plurality of charged particle beams onto the mark and scanning, and scanning the mark to be absorbed by the Faraday cup. Measuring a current amount of the charged particle beam based on the detected current amount, and selectively sequentially moving the beam having the desired arrangement to measure the beam. A multi-beam measurement method, characterized in that: A plurality of the opening marks are arranged at predetermined intervals, and the Faraday cups installed corresponding to each of the marks are arranged at an interval equal to or an integral multiple of an arrangement pitch dimension of the plurality of charged particle beams. 4. The multi-beam measurement method according to claim 3, wherein: Means for generating a plurality of charged particle beams two-dimensionally arranged at predetermined intervals; means for independently controlling on / off of each of the plurality of charged particle beams in accordance with pattern data to be drawn; Means for collectively deflecting and scanning the charged particle beam on the sample, and scanning by the deflection scanning means on at least one measurement mark having a linear shape substantially perpendicular to the scanning direction of the plurality of charged particle beams. And a detector for detecting a secondary particle signal, and wherein the plurality of charged particle beams are detected by selectively scanning a plurality of beams belonging to a desired arrangement on the mark. A multi-beam apparatus configured to measure a beam characteristic of the charged particle beam using a secondary particle signal.

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