JPH059808Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention includes a first detector for obtaining a detection signal with emphasis on shadows and a second detector for obtaining a detection signal with good symmetry. The present invention relates to a charged particle beam device equipped with a charged particle beam device.

[Prior art] Figure 3 shows a conventional electron beam length measuring device.
In the figure, 1 is a deflection coil, 2 is an objective lens, 3 is a sample, 4 is a first secondary electron detector, 5 is a first secondary electron detector placed above the objective lens, 4
ps and 5ps are the power supplies of the detectors 4 and 5, respectively, and 6 and 7
is an amplifier, 8 is a switching circuit, 9 is an adder circuit, and 10 is an adder circuit.
11 is a scanning signal generation circuit, 12 is an arithmetic control circuit, and 13 is a cursor position input device.

In such a configuration, first, the power source 4ps is turned on, and the output signal of the detector 5 is guided to the CRT 10 via the switching circuit 8.
Therefore, a scanning signal is generated from the scanning signal generating circuit 11, and the sample is two-dimensionally scanned by the electron beam EB. As a result, the secondary electrons generated from the sample 3 fly toward the detector 4 due to the asymmetrical attractive electric field with respect to the optical axis from the detector 4, as shown by the trajectories e1 and e2, and then are detected by the detector 4. Detected. Therefore, the CRT 10 displays an image with enhanced shadows corresponding to a one-sided illumination image using visible light. The operator observes this image and selects the field of view to be measured. In order to perform high-precision length measurement, in an electron beam length measurement device that does not tilt the sample, the image based on the first detector 4 can emphasize the shadows of the sample, so the sample can be grasped three-dimensionally, and the field of view can be selected. It is convenient. However, after selecting the field of view, when trying to measure the width of the mask M, for example, whose cross section is shown in FIG.
The output signal of the sensor becomes an asymmetrical signal as shown in FIG. 5a or 5b, and even if such a signal is processed, highly accurate length measurement cannot be performed. Therefore, when measuring the desired length within the selected field of view, turn off the power source 4 ps, turn on the power source 5 ps, and select the output signal of the detector 5 by the switching circuit 8. Scan the EB two-dimensionally. As a result, some of the secondary electrons generated from the sample 3 are focused by the magnetic flux from the objective lens 2 and guided to the upper stage of the lens 2, as shown by trajectories e3 and e4, where they are detected by the detector 5. Ru.
Since the focused field by the lens 2 is symmetrical with respect to the optical axis, the detection signal accompanying the scanning of the mask M is the fifth
As shown in Figure c, the signal becomes symmetrical, and although it is difficult to distinguish the unevenness of the sample, it becomes a signal suitable for length measurement. Therefore,
While observing the image of the mask M displayed on the CRT 10, the operator moves a cursor (not shown) to the positions of both edge images of the mask M by operating the cursor position input device 13. Therefore, when a length measurement is commanded, the arithmetic and control unit 12 measures the length of the part sandwiched between the cursors based on the signal from the second detector 4, and adds a display signal of the measured value to the addition circuit 9. The data is sent to the CRT10 via the . Therefore, the length measurement value is displayed on the CRT 10.

[Problems to be solved by the invention] In such a conventional device, when the first detector 4 is used, the power supply is turned off at 5 ps, but some of the secondary electrons generated from the sample are is guided toward the lens 2 side by the magnetic flux of the objective lens 2, so the detection efficiency of the first detector 4 is insufficient, and when using the second detector 5, the power supply 4ps is turned off, but the secondary electrons generated from the sample and flying away from the optical axis cannot be effectively guided to the detector 5 by the magnetic flux of lens 2 alone, so the detection efficiency is also reduced in this case. In both cases, the images displayed on the CRT were of poor quality due to insufficient signals.

The present invention solves such drawbacks and provides a charged particle beam device in which images based on both detectors are switched and displayed by switching between the first and second detectors. The purpose of this invention is to provide a charged particle beam device that can improve the image quality of images displayed on a CRT by sending a signal with an increased signal amount to the CRT even when using a CRT. .

[Means for Solving the Problems] Therefore, the present invention includes an objective lens, a means for scanning a charged particle beam focused by the objective lens on a sample, and a method for obtaining a detection signal with emphasis on shadows. A second detector is provided to obtain a detection signal with good symmetry with the first detector, and the first detector has an attractive electric field that is asymmetric with respect to the optical axis and extends between the sample and the lens. The second detector is a detector for attracting and detecting secondary electrons, and the second detector is a detector for detecting secondary electrons focused by the lens magnetic field and guided to the upper stage of the lens. Or, in an apparatus in which the detector is arranged symmetrically with respect to the optical axis at the lower stage of the lens, and the first and second detectors are used by switching, the lower yoke of the lens also serves as a detector. Alternatively, it is characterized by comprising an electrode attached near the lower yoke, and means for switching and applying a positive or negative voltage to the electrode.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail based on FIG. 1, but the same components as in FIG. 3 will be given the same numbers and their explanation will be omitted.

In FIG. 1, 14 is an electrode, and the electrode 14
is the lower yoke Y of the lens 2 via the insulating member 15.
is attached to. The electrode 14 is a switching circuit 16
via negative variable power supply 17 or positive variable power supply 18
It is now possible to connect to. Furthermore, the switching circuit 8, the switching circuit 16, and the power supplies 4 ps and 5 ps are interlocked as follows. That is,
If switching circuit 8 is switched to terminal a side, switching circuit 1
6 is also switched to the terminal a side, and the power supply 4 ps is turned on and the power supply 5 ps is turned off. Conversely, if the switching circuit 8 is switched to the terminal b side, the switching circuit 16 is also switched to the terminal b side, and the power supply 5 ps is turned off. turns on and the power 4ps turns off.

In such a configuration, in order to select the field of view to be measured, if the switching circuit 8 is switched to the terminal a side, the power supply 4ps is turned on, the power supply 5ps is turned off, and the switching circuit 16 is switched to the terminal a side. Can be switched. Therefore, a negative potential is applied to the electrode 14. Therefore, if the sample 3 is scanned by the electron beam EB, some of the secondary electrons generated from the sample 3 will be
A part of the secondary electrons that are focused by the magnetic flux and head toward the lens 2 are repelled by the electrode 14 and head toward the detector 4, so that the detection efficiency of the detector 4 can be improved.

Next, in order to measure the length, switch the switching circuit 8 to the terminal b side, the power supply will be turned on at 5 ps, and the power supply will be turned on at 4 ps.
When the switch is turned off, the switching circuit 16 is switched to the terminal b side, so that a positive potential is applied to the electrode 14. Therefore, if the sample 3 is scanned by the electron beam EB, the secondary electrons generated from the sample 3 will be directed to the upper side of the objective lens 2 more efficiently than before due to the focusing effect of the magnetic flux of the lens 2 and the attraction effect of the electrode 14. and detected by the second detector 5.

In this way, when using the first and second detectors, the detection efficiency of both detectors can be improved simply by switching the switching circuit, thereby sending sufficient signals to the CRT to produce a high-quality image. can be displayed.

In addition, as the second detector for obtaining a symmetrical detection signal, the detector 5 disposed above the objective lens was used in the above-mentioned embodiment, but this second detector
The present invention can be similarly applied to the case where a donut-shaped channel plate 19 as shown in FIG. 2 is used as a detector.

In such a case, the electrode 2 is replaced with the electrode 14.
0 and the voltage applied to this electrode 20 can be switched between positive and negative, the same effect as described above can be achieved.

The present invention is not limited to the embodiments described above, and can be implemented with further modifications.

For example, in the embodiment shown in FIG. 1, the electrode 14 is attached to the lower yoke Y of the lens 2, but the lower yoke Y itself may also be used as the electrode.

Further, although the above-mentioned embodiment is an example in which the present invention is applied to an electron beam length measuring device, the present invention has the above-mentioned first and second embodiments.
The present invention can be similarly applied to other types of charged particle beam devices including a second detector.

[Effects of the invention] As described above, the apparatus based on the invention includes a first detector for obtaining a detection signal with enhanced shadows, and a second detector for obtaining a detection signal with good symmetry. In a device that is equipped with a detector and is used by switching between the two detectors, it is possible to always send a sufficient detection signal to the display means regardless of the switching of the detector, so that the displayed image based on both detectors is Quality can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing main parts of another embodiment of the invention, Fig. 3 is a diagram showing a conventional device, and Fig. 3 is a diagram showing a conventional device. FIG. 4 is a diagram for illustrating an object to be measured, and FIG. 5 is a diagram for comparing output signals of the first and second secondary electron detectors. 1... Deflection coil, 2... Objective lens, 3...
Sample, 4...first secondary electron detector, 5...second
Secondary electron detector, 4ps, 5ps...detector power supply,
8, 16...Switching circuit, 9...Addition circuit, 10...
...CRT, 11...Scanning signal generation circuit, 12...
Arithmetic control circuit, 13...Cursor position input device, 1
4,20...electrode, 15...insulating member, 17,1
8...Variable power supply, 19...Channel plate type second detector, EB...Electron beam, Y...Lower yoke.

Claims (1)

[Scope of utility model registration request] an objective lens; means for scanning a charged particle beam focused by the objective lens over a sample;
A first detector for obtaining a detection signal with emphasis on shadows and a second detector for obtaining a detection signal with good symmetry, the first detector protruding between the sample and the lens. This is a detector for attracting and detecting secondary electrons using an attractive electric field that is asymmetric with respect to the optical axis, and the second detector is a detector for attracting and detecting secondary electrons using an attractive electric field that is asymmetric with respect to the optical axis. A detector for detecting secondary electrons or a detector disposed below the lens symmetrically with respect to the optical axis, and in the apparatus in which the first and second detectors are used by switching, the lens A charged particle beam device comprising: an electrode which is also used by a lower yoke or is attached near the lower yoke; and means for switching and applying a positive or negative voltage to the electrode.