JPH0145176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to scanning electron microscopes and similar devices, and in particular to devices for detecting secondary charged particles such as secondary electrons.

There is a secondary electron detection device for a conventional scanning electron microscope, as shown in Figure 1.
A plurality of (two in this example) detectors 1, 1' are arranged axially symmetrically above a focusing lens (objective lens) 3 to detect secondary electrons from a sample 2.

However, in such a conventional secondary electron detection device, although optical axis deviation and astigmatism are less likely to occur, there is a problem in that the central portion of the sample image becomes dark due to the following reason. That is, detectors 1, 1'
When installed axially symmetrically, the equal electric field distributions E and E' caused by the high voltage applied to each detector 1 and 1' become as shown in Figure 1, so the secondary electrons A and C are They are detected by detectors 1 and 1', respectively, but secondary electron B passes between both detectors 1 and 1' and escapes upward without being detected by either detector 1 or 1'. This causes the central part of the sample image to become dark.

The present invention aims to solve such problems by making it possible to detect secondary charged particles that escape upward without being detected by any detector due to the electric field distribution. An object of the present invention is to provide a secondary charged particle detection device for a scanning electron microscope and similar devices, which can obtain a sample image with uniform brightness.

Therefore, in a scanning electron microscope and similar devices, the device of the present invention uses a plurality of devices arranged above a sample to detect secondary charged particles generated from the sample when irradiated with a charged particle beam. 2 above, which is equipped with a detector and passes between these detectors.
In order to return the escaping portion of the secondary charged particles and guide them to the detector, an electric field generating mechanism is provided for changing the traveling direction of the escaping portion of the secondary charged particles. A metal pipe arranged above so that the optical axis of the charged particle beam and the central axis are aligned, and a metal pipe interposed between the pipe and the sample to apply a more negative voltage than the sample to the pipe. It is characterized by being configured with a DC power supply.

Hereinafter, a secondary electron detection device in a scanning electron microscope as an embodiment of the present invention will be explained with reference to the drawings. FIG. 2 is a schematic diagram showing the arrangement state in cross section. The same reference numerals as in the figure indicate substantially similar parts. As shown in Fig. 2, in this device, as in the conventional device, a plurality of (two) detectors 1, 1' are equipped with a focusing lens to detect secondary electrons as secondary charged particles from the sample 2. They are arranged axially symmetrically above 3.

By the way, in order to return the escaping portion B of the secondary electrons that have passed between the detectors 1 and 1' and guiding them to the detector 1 or 1', the progress of the escaping portion B of the secondary electrons is Electric field that causes the direction to change (negative electric field)
An electric field generating mechanism M that generates is provided. That is, slightly above each detector 1, 1',
A metal pipe 4 is provided so that its central axis and optical axis L are aligned, and a voltage (from minus several volts to minus several tens of volts) that is more negative than that of the sample 2 is applied to this pipe 4. A DC power supply 5 is interposed between the pipe 4 and the sample 2.

As a result, an electric field, that is, a negative electric field, is applied to the pipe 4 to change the traveling direction of the escaping portion B of the secondary electrons A, B, and C generated from the sample 2 upon receiving the electron beam 6 as a charged particle beam. It can be applied to the space between the sample 2 and the sample 2. As a result, in particular, 2
Since the secondary electrons B are pulled back to the sample 2 side, the secondary electrons B are detected by the detector 1 or 1' in the same way as the secondary electrons A and C. Therefore, the central part of the sample image does not become dark, and an image with uniform brightness can be obtained.

In this case, the negative applied voltage applied to the pipe 4 is approximately from several volts to several tens of volts (a value of this order is sufficient), so there is no effect on the incident electron beam 7.

Note that the sample 2 is placed near the center point of the focusing lens 3 in order to improve resolution.

Further, the detectors 1, 1' are configured with secondary electron detection surfaces (fluorescent surfaces) 1a, 1'a, light pipes 1b, 1'b, photomultipliers 1c, 1'c, etc. These detectors 1, 1' are connected to a CRT (cathode ray tube) via a signal adder, amplifier, etc. (not shown).

In addition, by electrically insulating the detector installation part from other lens barrel parts and applying a negative voltage to this installation part, it is possible to change the direction of movement of the secondary electron escaping portion B. An electric field may be further generated.

Furthermore, the present invention can be similarly applied when three or more detectors are provided, and these detectors may be arranged axially symmetrically, point symmetrically, or along the circumference. The present invention can be applied in the same way even when the elements are arranged at equal intervals.

Furthermore, the present invention is applicable to scanning electron microscopes as well as
It can be applied to secondary charged particle detection devices for devices similar to this.

As described in detail above, the secondary charged particle detection device in the scanning electron microscope and similar devices of the present invention detects secondary charged particles generated from a sample upon irradiation with a charged particle beam. A plurality of detectors are provided above the sample, and the secondary charged particles that have passed between these detectors are returned and guided to the detector. A metal device, which is provided with an electric field generating mechanism that changes the direction of the progress of the escaping component, and is arranged so that the optical axis of the charged particle beam and the central axis are aligned above the detector. This simple method consists of a pipe and a DC power supply interposed between the pipe and the sample to apply a more negative voltage to the pipe than the sample, and eliminates optical axis misalignment and astigmatism. In addition, secondary charged particles that escape upward without being detected by any of the detectors due to the electric field distribution of the detectors can be efficiently pulled back and detected, resulting in uniform brightness. This method has the advantage of being able to produce a sample image of a large size.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the arrangement of a secondary electron detection device in a conventional scanning electron microscope, and FIG. 2 is a diagram showing secondary electron detection in a scanning electron microscope as an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the arrangement of the device. 1, 1'...Detector, 1a, 1'a...Secondary electron detection surface, 1b, 1'b...Light pipe, 1c, 1'c...
Photomultiplier, 2... Sample, 3... Focusing lens, 4... Metal pipe, 5... DC power supply, 6... Electron beam (charged particle beam), A, B, C... Secondary electron (secondary charged particle), L...Optical axis, M...Electric field generation mechanism.

Claims (1)

[Claims] 1. Scanning electron microscopes and similar devices are equipped with multiple detectors placed above the sample to detect secondary charged particles generated from the sample when irradiated with a charged particle beam. In order to return the escaping portion of the secondary charged particles that have passed between the containers and guiding them to the detector, an electric field generating mechanism is provided for changing the direction of the escaping portion of the secondary charged particles, The electric field generation mechanism includes a metal pipe arranged above the detector so as to align the optical axis of the charged particle beam with the central axis, and a metal pipe arranged to apply a more negative voltage than the sample to the pipe. 1. A secondary charged particle detection device for a scanning electron microscope and similar devices, comprising: and a DC power supply interposed between the sample and the sample.