JP4150547B2 - Multi-beam measurement method and multi-beam apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measurement technique for evaluating beam characteristics in a multi-beam apparatus using a multi-electron beam or the like.
[0002]
[Prior art]
Conventionally, for example, a fuzzy cup having a large opening of about several millimeters provided on a stage has been used for electron beam measurement.
[0003]
Alternatively, in the case of a multi-electron beam apparatus having a plurality of electron beams, as described in JP-A-8-191042, each lens barrel has an optical system independently from a plurality of electron guns and an electron beam column. Measurement was performed using a 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 apparatus, a multi-beam system (multi-electron beam apparatus) that performs drawing or length measurement using a plurality of beams simultaneously is necessary. However, in such a multi-beam system, fine electron beams are densely arranged in a small area, and each electron beam passes through a separate electron optical system. Therefore, it is necessary to perform beam measurement for each beam individually. . When such a multi-beam is measured using one Faraday cup, it takes a lot of time to measure one beam at a time.
[0005]
On the other hand, JP-A-8-191042 discloses a system in which a plurality of lens barrels, marks and Faraday cups opposed to the lens barrel are arranged. And secondary electrons can be measured individually.
[0006]
However, in a high-density array configuration in which the beam spacing of multi-beams is narrowed, it is not possible to separate and measure reflected electrons and secondary electrons generated from adjacent marks even if multiple detectors are prepared. It becomes possible.
[0007]
Furthermore, if the plurality of mark arrays are at the same interval as the multi-beam array, the multi-beams are irradiated onto the marks at the same time during beam scanning, so that reflected electrons and secondary electrons are generated simultaneously from each mark. For this reason, it becomes difficult to obtain individual characteristics of each beam from the signal from each mark. Also, with this method, it is difficult to measure the spacing between the beams.
[0008]
An object of the present invention is to provide a beam measurement technique that realizes beam characteristic measurement of each beam and measurement of an array interval between beams at a high speed in a multi-beam apparatus.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a linear mark perpendicular to the beam scanning direction is prepared as a method for measuring a multi-electron beam having a high-density array, and the multi-electron beam having the high-density array is specified. The beam is measured by selectively irradiating the mark with only the beam in the row.
[0010]
When secondary particles such as reflected electrons or secondary electrons are used as a detection signal, one linear mark perpendicular to the beam scanning direction is prepared. By scanning a beam in a specific row that is selectively turned on on the mark, the characteristics of each beam are separated by a time interval corresponding to the beam interval, and the respective beam signals are separated as reflected electron or secondary electron signals. Measurement is possible 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 the beams. In addition, measurement for all the multi-electron beams having a high-density array can be realized by repeatedly performing the above measurement for each array.
[0012]
Alternatively, in the present invention, as a method for measuring a multi-electron beam with a high-density array, a plurality of linear marks perpendicular to the beam scanning direction are prepared, and only a specific row of the multi-electron beams with the high-density array is prepared. Is selectively irradiated onto the mark to perform beam measurement.
[0013]
When secondary particles such as reflected electrons or secondary electrons are 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 integer multiple thereof. Thus, when a beam of a specific row that is selectively turned on is scanned on this mark, it is possible to measure with one signal detector as a signal in which each beam signal is separated. If the interval between the linear marks is 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 the beams.
[0014]
Alternatively, in the present invention, as a method of 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 the beam is measured by selectively irradiating the mark with only a specific row of the multi-electron beams having the high-density array.
[0015]
In this case, the amount of current absorbed in the Faraday cup as a detection signal is measured. It is possible to measure the amount of current absorbed by the Faraday cup as a signal in which each beam signal is separated when scanning a beam in a specific row that is selectively turned on on the mark. The information obtained at this time is the current amount of each beam, its beam profile, and the arrangement interval between the beams.
[0016]
Alternatively, in the present invention, as a method of measuring a multi-electron beam having a high density array, 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 the high density The beam is measured by selectively irradiating the mark with only a specific row of the multi-electron beam composed of the array.
[0017]
In this case, the amount of current absorbed in the Faraday cup as a detection signal is measured. It is possible to measure the amount of current absorbed by the Faraday cup as a signal in which each beam signal is separated when scanning a beam in a specific row that is selectively turned on on the mark. If the interval between the linear marks is 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 the beams.
[0018]
In each example, the case of a multi-electron beam has been described. However, the present invention can provide the same effect with other charged particle beams 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 arranged two-dimensionally at a predetermined interval; A step of selectively scanning the mark with a plurality of charged particle beams belonging to a desired array, and a step of detecting a secondary particle signal obtained from the mark by scanning using a single detector; And a step of 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 opening mark having a linear shape substantially perpendicular to the scanning direction of a plurality of charged particle beams arranged two-dimensionally at a predetermined interval, and A step of disposing a Faraday cup below the mark corresponding to the opening mark; a step of 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 in the Faraday cup; and measuring the beam characteristics of the charged particle beam based on the detected amount of current; It is characterized in that measurement is performed by selectively shifting sequentially.
[0022]
Furthermore, the multi-beam apparatus according to the present invention independently generates a plurality of charged particle beams arranged two-dimensionally at a predetermined interval, and independently applies each of the plurality of charged particle beams in accordance with pattern data to be drawn. Means for controlling on / off, means for collectively deflecting and scanning the charged particle beams controlled on and off, and at least one linear shape substantially perpendicular to the scanning direction of the plurality of charged particle beams by the deflection scanning means; A detector for detecting a secondary particle signal obtained by scanning the measurement mark, and selectively selecting a plurality of beams belonging to a desired arrangement among the plurality of charged particle beams. The secondary particle signal detected by scanning upward is used to measure beam characteristics of the charged particle beam.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0024]
An embodiment of the present invention will be described with reference to FIGS. In the multi-electron beam drawing system as shown in FIG. 4, the electron beam 202 generated from the electron gun 201 is irradiated to the aperture 204 as a parallel beam by the lens 203 and shaped as a multi-point beam by the lens 205. These beams 206 can be stopped by being passed through the subsequent optical system or absorbed by the diaphragm 208 by independently and selectively controlling the beams by the blanker electrode 207 and the diaphragm 208. The intermediate image 209 of the beam selectively passing through the diaphragm 208 in this way 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 deflected.
[0025]
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, a 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 beam 1 is arranged vertically and horizontally (two-dimensionally) at a predetermined interval on the sample, and can be turned on and off independently.
[0027]
Since these point beams are arranged at a high density with a pitch of about 2 μm, a one-to-one mark is prepared for each beam as described in JP-A-8-191042, as described above. Even if a plurality of backscattered electron detectors are prepared for this beam, since the arrangement of the point beam is high density, electrons reflected from the respective marks cross each other and enter the detector. Therefore, the 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 linear. A sample provided with the mark (for example, tungsten) 2 is prepared, and only four beams in the third row from the top are turned on as shown in FIG. These beams are deflected by the deflectors 211, 212, 213, and 215 so as to be orthogonal to the mark 2 all at once.
[0029]
As a result, the reflected electrons 5 generated when the beams cross the mark 2 are detected by the detectors 6 and 216, and a current waveform 7 as shown in FIG. 3 is obtained. Signals from the four beams appear as four current waveforms 7 in accordance with the beam deflection amounts, and the multi-beam intervals are respectively determined at the peak intervals of the respective waveforms. Further, from the rise and fall of each waveform, the current distribution of each beam, that is, the beam diameter is obtained.
[0030]
In this measurement, the beams in the third row from the top of the multi-beams were measured. However, all the beams can be evaluated by sequentially measuring a desired desired array.
[0031]
In addition, when obtaining the beam interval in the vertical direction, similarly, a tungsten mark in the horizontal direction (on the paper surface) in FIG. 2 is prepared, and a desired array of beams is selectively shown in the vertical direction 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 the present embodiment, a plurality of straight marks are used unlike the above embodiment. As the beam detection means, the reflected electrons from the heavy metal mark are measured by the reflected electron detector in the same manner as in the above embodiment. In this method, a plurality of straight marks 2 as shown in FIG. 9 are used. The structure of each mark is constituted by a linear tungsten mark 2 on which an aluminum thin film 3 which is a light metal is formed on the silicon substrates 4 and 227 in the same manner as the above-described mark. The interval (m) between these marks is set to a value different from the beam interval measurement. In the case of FIG. 9, since the design value of the beam interval is 2 μm, the mark interval (m) is arranged at an interval of 2.1 μm, which is 0.1 μm larger than 2 μm.
[0033]
In the measurement, only four beams in the third row from the top are turned on as shown in FIG. These beams are deflected by the deflectors 211, 212, 213, and 215 so as to be orthogonal to the plurality of marks 2 all at once. As a result, the 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 traverses the mark is the rightmost beam in FIG. 9, and the other beams have not yet reached the mark. Next, when the second beam from the right reaches the mark, the rightmost beam passes through the mark, and the other beams have not yet reached the mark. By making the beam interval and the mark interval not coincide with each other in this way, the reflected electron signals from the respective beams can be temporally separated and measured with one detector.
[0034]
Therefore, as shown in FIG. 10, the signals from the four beams appear as four current waveforms 7 in accordance with the amount of beam deflection, and by adding the mark interval (m) to the peak interval (p) of each waveform, Accurate multi-beam intervals (b) are respectively obtained. Further, from the rise and fall of each waveform, the current distribution of each beam, that is, the beam diameter is obtained.
[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 is about the size of the beam interval. Therefore, the measurement is completed in a shorter time than the first embodiment. 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 a desired desired arrangement.
[0036]
Similarly, when obtaining the beam interval in the vertical direction, a tungsten mark in the horizontal direction (on the paper surface) is prepared in FIG. 9, and a desired array of beams is selectively shown in FIG. 9 in the vertical direction. It can be measured by deflecting in the vertical direction (on the paper). Further, the same 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 which is different from the above will be described with reference to FIGS. Here, a measurement method using an absorption current using a Faraday cup is used as the beam detection means.
[0038]
In this method, instead of the mark and the backscattered electron detector, a deep hole, for example, a Faraday cup 8 is prepared which is arranged at intervals equal to or an integral multiple of the multi-beam interval as shown in FIGS. To do. Each Faraday cup 8 is electrically isolated 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. An insulating film 13 is sandwiched above the deep hole 12, and a heavy metal thin wire (or knife edge) 11 such as a cross-shaped gold, tungsten, or tantalum is formed on the surface thereof. 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 acceleration voltage of the electron beam to be measured. When the acceleration voltage is 50 kV or more, an interval of 2 μm or more is required even if a heavy metal material is used. Therefore, when the multi-beam having an acceleration voltage of 50 kV or more and the interval is 2 μm or less, a Faraday cup arranged at an integer multiple of that interval is prepared, and only the beam facing the Faraday cup is selectively turned on. .
[0040]
In the case of FIG. 5, the beam of acceleration voltage 50 kV is arranged in 4 columns and 4 rows at 6 μm intervals, so that the Faraday cup 8 is arranged in 4 columns and 4 rows at 6 μm intervals. Thus, it was prepared on a mark substrate 227 shown in FIG. In addition, the distance between the arrangement of the cruciform thin line provided on the Faraday cup and the cruciform thin line provided on the adjacent Faraday cup is obtained in advance with an accuracy of about 1 nm by a coordinate measuring machine equipped with a laser interferometer.
[0041]
In the beam measurement, the multi-electron beam 10 is deflected all at once by the sub deflector 215 so that the thin lines 11 on the Faraday cup 8 are orthogonal as shown by arrows in FIG. In this measurement, unlike the first embodiment, the deflection width is not required as much as the selected beam arrangement width, and only the opening of the deep hole 12 of the Faraday cup is sufficient, so that 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 in the deep hole 12 as shown in FIG. 7 and the reflected electrons 17 are similarly confined in the Faraday cup 14. Accurate beam current is measured by measuring the current. Next, when this beam is deflected, the beams 100 and 101 are blocked by the thin wire 11 and the beam current is absorbed by the thin wire. At this time, the measured values with the ammeter connected to the wirings 9 and 18 from the Faraday cup were the results shown in FIGS. As a result, the difference between the minimum current beam position X1 in the wiring 18 as shown in FIG. 8A and the minimum current beam position X2 in the wiring 9 as shown in FIG. 8B. The distance between the beams 100 and 101 can be accurately obtained by adding the distance (α in FIG. 5) between the cruciform thin lines provided on the Faraday cup obtained in advance.
[0043]
At the same time, from the measurement results shown in FIGS. 8A and 8B, the maximum values of the beam current values 19 and 20 are the same, so that these beam current amounts do not change, the minimum value and its surroundings. Since the steepness at the difference in the beam current values 19 and 20 was found, it was found that the amount of blur of the beam 100 was large. Therefore, the blur of the beam 100 can be adjusted to the same value as the beam current value 19 by changing the set value of the lens 205 by the control circuit 220. Similarly, the other beams were measured and adjusted.
[0044]
Compared to measuring each beam with a single Faraday cup in 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 embodiments, two examples have been described. However, in either case, high-speed measurement several times to several tens of times is possible as compared with the case where each beam is sequentially measured according to the conventional method. In addition, the signal obtained by measurement is highly accurate because independent data is obtained for each beam. In each example, the embodiment using the multi-electron beam is described, but the same effect can be obtained by using other charged particle beams such as an ion beam.
[0047]
In the second embodiment, the Faraday cup arrangement density depends on the beam acceleration voltage to be measured, while the first embodiment does not depend on the beam acceleration voltage. Which one can measure at higher speed depends on the arrangement of multi-beams and the acceleration voltage, but it is also possible to prepare both marks and use the two measurement methods together.
[0048]
Examples of configurations included in the present invention are listed below.
[0049]
(1) In a method of measuring the beam characteristics of each charged particle beam arranged vertically and horizontally at regular intervals, linear measurement marks perpendicular to the scanning direction of the charged particle beam are provided and vertically and horizontally at the regular intervals. A beam characteristic of the charged particle beam is measured using a signal obtained by selectively scanning only a beam of a specific arrangement among the charged particle beams arranged on the measurement mark on the measurement mark. Beam measurement method.
[0050]
(2) The multi-beam measurement method according to (1), wherein the specific array is a linear beam array having 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 row perpendicular to the scanning direction.
[0052]
(4) The multi-beam measurement method according to (1), wherein the specific array is a beam in a horizontal row in the scanning direction.
[0053]
(5) The multi-beam measurement method characterized in that the measurement mark according to (1) is a linear fine opening, a deep hole is provided immediately below, and the amount of current absorbed in the deep hole is measured. .
[0054]
(6) The measurement mark according to the above (1) is a heavy metal pattern having a larger atomic number than a light tantalum on a light element substrate or light element thin film having a smaller atomic number than silicon, and the heavy metal pattern during beam scanning. A multi-beam measuring method comprising measuring by means of detecting reflected electrons or secondary electrons from the beam.
[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 in the deep hole when the charged particle beam is scanned on the knife edge is measured. (5) The multi-beam measurement method according to (5) above.
[0056]
(8) The above-mentioned (1), wherein a plurality of the linear measurement marks are provided at a constant interval, and the mark interval is different from the array interval of the charged particle beam and an integer multiple thereof. ) The multi-beam measurement method described.
[0057]
【The invention's effect】
According to the present invention, high-precision charged particle beam measurement corresponding to multi-beams can be realized at high speed by using a linear mark and specific array beam selection in multi-beam measurement of high-density array.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an embodiment of a charged particle beam measurement according to the present invention.
FIG. 2 is a top view illustrating the relationship between a beam and a mark in an embodiment of the present invention.
FIG. 3 is a diagram showing a measurement result according to an 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.
6 is an enlarged view showing an example of a Faraday cup used in the embodiment of FIG.
7 is a cross-sectional view showing a Faraday cup array for multi-beam measurement used in the embodiment of FIG.
FIG. 8 is a diagram showing a measurement result according to the embodiment of FIG.
FIG. 9 is a top view for explaining the relationship between a beam and a mark in another embodiment of the present invention.
10 is a diagram showing measurement results according to the embodiment of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 10, 100, 101, 202 ... Electron beam, 2 ... Heavy metal mark, 3 ... Aluminum thin film, 4, 16 ... Silicon substrate, 5, 17 ... Scattered electron, 6, 216 ... Detector, 7, 19, 20 ... Current waveform, 8, 14 ... Faraday cup, 9, 18 ... Wiring, 11 ... Metal fine wire, 12 ... Faraday cup deep hole, 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- 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 (4)

At least one measurement mark having a linear shape substantially perpendicular to the scanning direction of a plurality of charged particle beams arranged two-dimensionally at predetermined intervals is set to 2 at intervals equal to or an integral multiple of the intervals between the charged particle beams. Preparing a plurality of arrays arranged in a dimension, and installing a detector group in which a plurality of Faraday cups are arrayed in two dimensions corresponding to the measurement mark; and
When the interval between the plurality of charged particle beams arranged two-dimensionally is smaller than the minimum unit of the interval between the Faraday cups, the plurality of charged particle beams arranged two-dimensionally are arranged between the Faraday cups. A process of selectively turning on and scanning in accordance with the minimum unit of
Scanning the measurement mark and individually measuring the amount of current absorbed by the Faraday cup;
Measuring the beam characteristics of the charged particle beam according to the detected amount of current,
A multi-beam measuring method characterized in that the beam of the desired arrangement is selectively shifted and measured. The multi-beam measurement method according to claim 1, wherein the charged particle beam is an electron beam, and a minimum unit of an interval between the Faraday cups depends on an acceleration voltage of the electron beam . Means for generating a plurality of charged particle beams arranged two-dimensionally at a predetermined interval;
Means for independently controlling on / off of each of the plurality of charged particle beams according to pattern data to be drawn;
Means for collectively deflecting and scanning the charged particle beam controlled on and off onto the sample;
Corresponding to the measurement mark, a plurality of measurement marks having a linear shape substantially perpendicular to the scanning direction of the charged particle beam are arranged two-dimensionally at intervals equal to or an integral multiple of the interval between the charged particle beams. And a detector group in which a plurality of Faraday cups are arranged two-dimensionally at the bottom,
When the interval between the plurality of charged particle beams arranged two-dimensionally is smaller than the minimum unit of the arrangement interval between the Faraday cups, the plurality of charged particle beams arranged two-dimensionally are arranged between the Faraday cups. It is configured to measure the beam characteristics of the charged particle beam using the amount of current obtained by selectively turning on in accordance with the minimum unit of the arrangement interval and scanning by the deflection scanning means. Multi-beam device. The multi-beam apparatus according to claim 3, wherein the charged particle beam is an electron beam, and a minimum unit of an interval between the Faraday cups depends on an acceleration voltage of the electron beam .

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