JPH03211746A - Method and apparatus for measuring ion beam diameter - Google Patents

Abstract

PURPOSE:To accurately measure the diameter of an ion beam by employing samples made of two regions having relatively near values of sputtering ratio and different secondary electron emission ratio, and shifting a scanning position at the diameter or longer of the beam at each scanning of the beam. CONSTITUTION:Samples of two regions having relatively near values of sputtering ratio and different secondary electron emission ratios are employed. For example, Al, Ti or Zr substrate 62 is deposited on an Si substrate 63, scribed, a cleaved wall obtained by cracking is employed as the samples 9 at its surface to be scanned by an ion beam. When the diameter of the beam is measured, a measurement start signal 28 is first sent to a scan signal generator 21 by a microcomputer 24. The generator 21 outputs a normal sawtooth wave in an X direction and a deflection signal varied stepwise in a Y direction. The step interval of the Y direction is so set that the interval 1 of scanning lines 64 becomes the diameter or larger of the beam (e.g. 0.1mum), and the number of scanning N is 100. Then, it is scanned in a range of 10mum of the Y direction.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for determining the diameter of an ion beam, and is particularly useful for correcting defects in patterns of Lsxs optical masks such as photomasks and X411 masks, and for correcting LSI wiring. The present invention relates to a method for measuring the beam diameter of an ion beam in the accompanying S East ion beam processing.

[Conventional Technique #] Conventionally, as a method for correcting defects in LSI optical mask patterns such as photomasks and A method is being taken to remove it. In this case, ultrafine processing using a focused ion beam is required, and the beam diameter of the focused ion beam is d.

One method for measuring the beam diameter of this focused ion beam is to use the ion beam current obtained by scanning the ion beam perpendicularly to the knife etch and receiving the ion beam passing downward with a seven-array cutter. There is also a method described in JP-A-60-171724 that uses a second electron current obtained by scanning an ion beam at right angles to the edge and detecting second electrons generated from a sample. .

[Problem to be solved by the invention]

In the above prior art, l! The method using ion beam current, which is method 1, uses an Au a with a focused ion beam 44 attached to a substrate 42 as shown in Figure 6
A knife edge 41 made of metal such as Pt is scanned perpendicularly to the edge, and the ion beam current that is not cut off by the knife etch 41 and flows into the lower 7A cut 45 provided on the substrate 42 is detected. The beam diameter is measured with a synchroscope 45 based on the scanning speed of the ion beam 44 and the rise time (t) of the ion beam current, but in this method, when the ion beam 44 is scanned multiple times, the edge is processed. In addition, the beam diameter cannot be measured correctly due to the fact that the current path from the ion beam receiver 43 to the synchro scour 145 that measures the ion beam current picks up noise and has a slow response speed. There is.

In addition, in the second method, which uses secondary electron current, the
The method of communication is described. In the method shown in FIG. 6(b), a sample 48t consisting of a single-crystalline region 46 and a polycrystalline region 47 on the substrate 42 at the edge of a knife is used. iL, the ion beam 44 is scanned perpendicularly to the boundary 51 between the single crystal region 46 and the polycrystalline region 47, and the secondary electrons generated from the sample are
It uses the secondary electron current that has been learned by the secondary electron detector 49, and since the secondary electron emission ratio is different between the single crystal region 46 and the polycrystalline region 51, there is no border! p, 510 The beam diameter is determined from the fall time of the secondary electron current and the scanning speed of the ion beam 44. In this method, when the ion beam 44''ta is scanned several times, if there is no difference in sputtering rate between the single crystal region 46 and the polycrystalline region 47, there is no shadow # due to processing at the boundary, but the single crystal region 46 and the polycrystalline region 47 Since the region 47 is processed into a groove shape with approximately the same depth, the detected two-hour current becomes small, giving a shadow to the measured beam diameter.

In the ffi method according to FIG. Utilizing the difference between the secondary electrons generated from the substrate 42 and the secondary electrons generated from the deep hole of the single crystal 50, the falling time of the secondary electron current and the ion beam The purpose is to measure the beam diameter from the scanning speed. In this method, when the single crystal 50 is scanned with the ion beam 44, the generation of secondary electrons becomes large at the edge portion, and when the ion beam 44 is scanned multiple times, the edge portion is likely to be processed, which affects the beam diameter. .

In view of the prior art described above, an object of the present invention is to scan an ion beam over a sample and measure the beam diameter from the rise time of the detection current at the boundary between different materials of the sample and the scanning speed of the ion beam. The object of the present invention is to provide a method for measuring the diameter of an ion beam with high precision, without noise, with a fast response speed, and without processing the sample and the boundary between the samples by the ion beam.

[Means to solve the problem]

In order to achieve the above objects, the present invention provides a method for measuring the diameter of an ion beam in ion beam processing, using a sample consisting of a plurality of regions in which the secondary electron emission ratio is A and is made of solder with relatively similar sputtering rates. , the detection current 't- is generated from each sample as an IE current with two currents, and furthermore, the scanning by the ion beam is performed by changing the scanning position perpendicular to the scanning direction and the beam diameter every time the ion beam scans t-1 times. This is done while shifting.

In addition, scanning by one on-beam is used in conjunction with scanning to obtain a scanned ion perseverance image.

[Effect]

The ion beam diameter of the present invention is measured by scanning the ion beam t-1 times perpendicularly across the boundary of a sample, which is made up of multiple regions with relatively similar sputtering rates and different secondary singleton emission ratios. , by shifting the scanning position rM by more than the beam diameter, scanning fli! By always scanning an unprocessed sample with the beam, two-day electrons can be obtained under the same conditions, eliminating errors in the beam diameter.

In addition, each scan data of the scan ion consultant #JIt is not shifted by more than the beam diameter, but each is a secondary electron current value scanned at the boundary L[angle, and this can be used to obtain the beam diameter. can.

[Metal practice]

Hereinafter, an embodiment of a focused ion beam processing apparatus for implementing the ion beam diameter measuring method of the present invention will be described with reference to FIG.

The focused ion beam processing device in FIG.

A high-intensity liquid metal ion source 1, an extraction electrode 2 for extracting an ion beam from the liquid metal ion source 1, a lens IE pole 5 for focusing an ion beam 10 extracted from the ion source, and an ion beam 10. The blanking pole 4 that turns on and off, the blanking pin 5, the deflection electrode 6 that scans the processing area of the sample 9 or the scanning area to measure the beam diameter, and the sample @ 9 are moved in both the X and Y directions. A sample stage 7 for positioning and a secondary electron detector 8 for detecting secondary electrons generated from the sample 9 are all equipped, and these are installed in a vacuum container (not shown) of about 10 P&.
It is stored in.

Further, the secondary electron detector 8 is connected to an amplifier 23 that amplifies the minute current from the secondary electron detector 8, and the amplifier 23 is further connected to a noise filter 25 that removes noise from the amplified signal. It is connected to a microcomputer 24 which calculates the beam diameter from the data in the memory 27 via A/D converters 26 which digitize the signal after removing the digits and a memory 27 which stores the digitized data. However, in the deflection electrode 6,
A scan signal generator 21 that generates the same voltages for x and y4 is connected according to a command from the -r microcomputer 24. Further, the amplifier 23 is connected to a monitor 22 that displays a scan ion mirror image in synchronization with the scan 1 word generator 21.

Next, the operation of this focused ion beam diameter measuring device will be explained.

The ion beam 10 extracted from the liquid metal ion source 1 by the extraction electrode 2 is focused by the lens IE pole 3 and scanned over the sample 9 by the deflection electric field ff16. Sample 9
The number of secondary electrons generated from is 2? : is converted into minute tfM by the electron detector 8.

A sample 9 for beam diameter measurement and a sample for processing (not shown in the figure) are installed on the sample stage 7. First, the sample stage 7 is used to position the sample 9 for beam diameter measurement. Scanning ion j! by monitor 22 for positioning.
@Do it using a mirror image.

When obtaining a scanning ion microscope Wk mirror image, the deflection gI is
Increase the signal level to enlarge the scanning area.

The sample 9 for beam diameter measurement is shown in Figure 2 (aJ, (b)
As shown in Figure 2, samples are used from two regions with relatively similar sputtering rates but different secondary electron emission ratios. For example, as a sample, a Si substrate 63 is coated with Al, Ti, Ih, or Z.
A sample 9 is used in which the r-substrate 62 and the like are vapor-deposited and scribed, and the cracked surface obtained by cracking is used as the surface on which the ion beam is scanned.

When determining the beam 71 ft+jllJ, the scan signal generator 2 is first set by the microcomputer 24.
1, the measurement start signal 28 is sent. As shown in FIG. 3, the scan signal generator 21 generates a normal sawtooth wave in the X direction and a deflection f! that changes stepwise in the X direction. Output the r number. The step interval in the X direction is set so that the interval jl of each scan 4I64 is equal to or larger than the beam diameter (for example, CL 1 μm) as shown in N2 diagram (a), and the number of scans is N-10.
When set to 0, a range of 10 μm in the X direction is scanned.

At this time, the detection current obtained by the second electronic detection signal 8 is amplified by the amplifier 25, and noise is removed by the noise filter 25. The secondary electron current obtained at this time is the second
Scanning line 11m shown in figure (a).

As shown in FIG. 5, the falling time and the detection level are different for each of n. Therefore, it can be simply added. Therefore, in the order of scanning, the data are digitized by the A/D conversion processor 26 and stored in the memory 27.

When the scan signal generator 21 outputs N scanning lines, the scan signal generator 21 informs the microcomputer 24 that the measurement has ended.
-Send.

When the microcomputer 24 receives the measurement end signal 29, it calculates the beam diameter using the 2Rt current value for each scanning line stored in the memory 27 in the manner shown in FIG. By the way, the second electron current value of a focused 1-on beam is obtained by integrating the current density distribution of the ion beam in the scanning direction of the ion beam.If the current density distribution is assumed to be a normal distribution, the integrated value is shown in Figure 4. As shown, it agrees with the actually obtained secondary' electron current value. Therefore, for example, for the maximum secondary electron current value of 111I71 and the minimum [72], 1
The product of the time d for which 1 becomes 8% of 10 and the scanning speed of the ion beam is 1/of the maximum value of the current density distribution.
The beam diameter corresponding to e can be found.

In this way, the beam diameter is determined for each scanning line, and finally, the average value and dispersion value of the beam diameter are determined.

In addition, the signal sound in the y14 direction shown in FIG.
I! ! It may also be an I-image memory. At this time, a scanning ion microscope image of the boundary portion of the sample 9 is stored in the memory 27. In this case as well, the beam diameter can be determined by the method described above. however.

If the image input range is 10 μm2, the normal number of scanning lines is 5.
Since there are 12 beams, the beams hit the same spot 2.5 times!
! This is expressed in one scan.

〔Effect of the invention〕

According to the ion beam diameter measuring method and apparatus according to claim 1 or 2, a sample consisting of two regions having relatively similar sputtering rates and different secondary electron emission ratios is used as a sample for measuring the ion beam diameter. In addition, by shifting the scanning position by more than the beam distance each time the ion beam is scanned once, it is possible to obtain a 2-kilometer scan under the same conditions at all times. The ion beam diameter can be defined.

[Brief explanation of drawings]

Figure 1 is a block diagram of an ion beam diameter measuring device that is an embodiment of the present invention, Figures N2 (a) and (b) are explanatory diagrams showing the ion beam scanning method of the present invention, and Figure 5 is a diagram of the present invention. FIG. 4 is an explanatory diagram of the beam diameter of the invention, FIG. 5 is an explanatory diagram of the secondary electron current of the invention, and FIGS. 6(a) to (cJ is an explanatory diagram of a conventional method for measuring the diameter of an ion beam. 1... liquid metal ion source, 2... extraction electrode, 3...
...Lens electrode, 4...Blanking K (i, 5-)
・Blanking aperture, 6... Deflection ta, 7...
sample stage. 8...Secondary electron detector, 9...Beam diameter measurement sample, 10...Ion beam, 21...Scan signal generator, 22...Monitor, 23...-mllaUS
, 24...Microcomputer, 25...Noise filter, 26...A/D pronunciation, 27...Memory.

Claims (1)

[Claims] 1. An ion beam is extracted from an ion source using an ion beam optical system, focused, the ion beam is scanned over a sample using a deflection system, and the rise time of the detection current from the sample and the ion beam are measured. In the ion beam diameter measurement method that measures the beam diameter from the scanning speed, the sample is made up of multiple regions with relatively similar sputtering rates and different secondary electron emission ratios, and a detection current is generated from each sample. A method for measuring an ion beam diameter, characterized in that the current is generated by secondary electrons, and scanning on a sample is performed while shifting at least the beam diameter orthogonally to the scanning direction. 2. The ion beam diameter measuring method according to claim 1, wherein scanning of the sample by the ion beam is used in combination with scanning for obtaining a scanning ion microscope image. 3. Extract and focus the ion beam from the ion source using the ion beam optical system, scan the ion beam on the sample using the deflection system, and calculate the beam diameter from the scanning speed of the ion beam using the rise time of the detection current from the sample. When measuring, 2
a secondary electron detector, an amplifier that amplifies the detection output from the detector, a noise filter that removes noise from the output of the amplifier, and a D/A converter that digitizes the detection output from which the noise has been removed; A memory that stores the digitized detection output, a microcomputer that calculates the beam diameter from the detection output stored in the memory, and an X
, and a monitor that displays a scanning ion microscope image in synchronization with a scan signal from a scan signal generator that generates a Y deflection voltage.