JPH051584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a charged particle beam length measuring machine, and more specifically to a device capable of having a length measuring function and observation of a three-dimensional scanned image.

[Prior art] Recently, microchannel plates (hereinafter referred to as
MCP) is widely used as a charged particle detector in electron beam length measuring machines, focused ion beam devices, etc. due to its characteristics such as small size, light weight, high gain, excellent time response, and little influence by magnetic fields. .

Figure 4 is a cross-sectional view of the configuration when an MCP with such characteristics is used, for example, in an electron beam length measuring machine, and Figure 5 is a plan view of the MCP4, where 1 is the objective lens and 2 is the sample. 3 is a scanning electron beam, 4 is an MCP, and the MCP 4 is a thin glass tube bundle (channel) 4a that multiplies secondary electrons e generated from a sample as incident electrons, and the channel 4a.
A collector 4b detects the output electrons multiplied by the collector 4b. In addition, in FIG. 4, between the input end and the output end of the channel 4a and between the output end and the collector 4b,
An accelerating voltage is applied to each.

In the electron beam length measuring machine configured in this way,
As shown in Figure 5, the center hole type
An MCP is used, and for example, secondary electrons e from the sample 3 are detected by an MCP 4 placed opposite the sample 3. Therefore, when a sample 3 with unevenness as shown in FIG. 6A is scanned with the electron beam 1, the secondary electron detection signal will show a symmetrical waveform as shown in FIG. 6B due to the so-called edge effect. , which is necessary to improve length measurement accuracy.

[Problems to be solved by the invention] By the way, in the conventional apparatus configured as described above, since the secondary electron detection by MCP4 has a symmetrical waveform as shown in Figure 6 (b), it is difficult to detect the electron beam on the sample. MCP4
If the detection signal obtained from the above is supplied to a display device (not shown) and displayed as a scanned image, the uneven sample 4 will also be displayed as a planar image without a stereoscopic view, which will cause problems in sample image observation.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a charged particle beam length measuring machine capable of measuring the length of a sample and also observing a three-dimensional scanning image using a plurality of MCPs arranged facing the sample. It is an object.

[Means for Solving the Problems] The present invention for achieving the object is to irradiate a sample with a charged particle beam and to collect secondary charged particles generated from the sample, which are placed opposite to the sample. In a device for detecting secondary charged particles using a microchannel plate, the microchannel plate is divided into at least two parts, and the secondary charged particle incident end of each microchannel plate is placed at a potential during length measurement. 2 of one microchannel plate during stereoscopic scanning image observation.
The present invention is characterized in that means is provided for switching the potential of the secondary charged particle entrance end to positive and the potential of the secondary charged particle entrance end of the other microchannel plate to negative.

[Example] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a cross-sectional view of an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the structure of an embodiment of the invention.
FIG. 3 is a plan view of MCP. Components that are the same as those of the conventional device shown in FIG. 4 are given the same numbers and their explanations will be omitted. In FIGS. 1 and 2, an MCP formed from a channel 10a and a collector 10b
10 and an MCP 11 formed from a channel 11a and a collector 11b are arranged facing the sample 3 while being electrically insulated. 12 is MCP1
13 is a power supply for switching and applying a positive and negative voltage (for example, ±10V) to the MCP 11; 14 is a polarity switching circuit, and the polarity of the voltage power applied to the MCP 10 and the MCP 11 is switched by the polarity switching circuit 14.

In the device configured in this way, when a symmetrical waveform is required such as during length measurement, the polarity is switched by the circuit 14.
The polarity of both MCP10 and MCP11 is switched to a positive potential (for example, 10V). In this way, by switching the polarity of both MCPs, MCP10 and MCP11
Since the secondary electron e from sample 3 is detected by both MCPs of , can be used as a length measuring device.

In addition, when it is desired to observe a stereoscopic scanned image, the polarity switching circuit 14 applies a negative voltage (for example, -10V) to the MCP10 from the power supply 12.
1 to apply a positive voltage (for example, 10 V). By this switching, when sample 3 is scanned as shown in Fig. 3A, only MCP11 is
It becomes possible to detect the next electron, and as a result,
Even if the amount of secondary electrons generated from the protrusion 3a of the sample near the MCP 11 and the protrusion 3b of the sample far from the MCP 11 is the same, the protrusion near the MCP 11
More secondary electrons from 3a are detected, and the detection signal waveform of the MCP 11 becomes as shown in FIG. 3B. Therefore, a three-dimensional scanned image can be observed.

The above embodiments are illustrative and can be implemented in other ways. Although the MCP is divided into two in the above embodiment, the MCP is not limited to this, and may be divided into multiple parts. Alternatively, the sample may be irradiated with an ion beam, secondary ions from the sample may be detected, and a secondary ion image may be observed.

[Effects of the Invention] As detailed above, according to the present invention, the MCP placed facing the sample is divided and placed, and
During length measurement, the potential at the secondary charged particle entrance end of each microchannel plate is switched to positive, and during stereoscopic scanning image observation, the potential at the secondary charged particle entrance end of one microchannel plate is switched to positive, and the potential at the secondary charged particle entrance end of one microchannel plate is switched to positive. Since a means is provided to switch the potential of the secondary charged particle incident end of the plate to negative, the secondary charged particle detection signal waveform from the sample can be detected symmetrically or asymmetrically. A particle beam length measuring machine is provided.
Furthermore, when obtaining a three-dimensional scanning image, it is sufficient to simply switch the potential of the secondary charged particle entrance end of one microchannel plate to positive, and the potential of the secondary charged particle entrance end of the other microchannel plate to negative.
There is no need for a subtraction circuit that calculates the difference between detection signals from each microchannel plate. Therefore, it is advantageous in terms of manufacturing cost.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of the present invention, Fig. 2 is a plan view of the MCP used in Fig. 1, Fig. 3 A and B are diagrams for explaining the present invention, and Fig. 4 is a diagram of the conventional device. Schematic configuration diagram, Figure 5 is a plan view of the conventional MCP, Figure 6 is a diagram of the conventional MCP.
Figures A and B are diagrams for explaining a conventional device. 1: Objective lens, 2: Electron beam, 3: Sample, 1
0, 11: MCP, 12, 13: Power supply, 14: Polarity switching circuit.

Claims (1)

[Claims] 1. In a charged particle beam length measuring machine that irradiates a sample with a charged particle beam and detects secondary charged particles generated from the sample using a microchannel plate arranged opposite to the sample, the microchannel plate is connected to at least two When measuring the length, the potential of the secondary charged particle entrance end of each microchannel plate is switched to positive, and when observing a three-dimensional scanning image, the potential of the secondary charged particle entrance end of one microchannel plate is changed to positive. Make the potential positive,
A charged particle beam length measuring device provided with means for switching the potential of the secondary charged particle incident end of the other microchannel plate to negative.