JP3117795B2 - Scanning electron microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope and, more particularly, to a scanning electron microscope which is optimally used for measuring a length based on a secondary electron detection signal.

[0002]

2. Description of the Related Art In a general scanning electron microscope, an electron beam is scanned on a sample, secondary electrons obtained based on the scanning are detected, and a detection signal is guided to a cathode ray tube to form a secondary electron image of the sample. I'm trying to get With such a scanning electron microscope, an electron beam is linearly scanned across a specific pattern on a sample, and the width of the pattern is measured based on a secondary electron signal obtained by the scanning. ing. FIG. 1 shows a cross section of a sample to be measured.
Is provided with a convex pattern 2. Here, the electron beam is scanned across the pattern 2 as shown by the arrow,
Secondary electrons generated by this scanning are detected by the detector 3.

[0003]

When secondary electrons are detected based on the scanning of the electron beam described above, one side 2a of the pattern 2 becomes a shadow when viewed from the detector 3, so that the side 2a of the pattern 2 is shaded. The number of secondary electron detection signals is small, and the number of secondary electron detection signals from the other side 2b facing the detector 3 is large. Accordingly, as shown in FIGS. 2A and 2B, the detection signal has poor symmetry of the signal due to the two sides of the pattern. Even if the pattern width is measured based on such a signal having poor symmetry, sufficiently high accuracy cannot be obtained.
Due to such a problem, it is also performed to provide two detectors and add the signals of the two detectors. However, providing two detectors increases the cost. Further, of the secondary electrons, secondary electrons traveling between the two detectors are not detected by any of the detectors, and a new problem that the signal amount is reduced occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to realize a scanning electron microscope capable of obtaining a secondary electron detection signal with good symmetry using a single detector. It is in.

[0005]

A scanning electron microscope according to the present invention comprises a conical objective lens and a tilted sample stage for tilting a sample placed at the bottom of the conical objective lens about the optical axis. A secondary electron detector disposed obliquely along the wall of the conical objective lens at a position where the sample does not collide with the inclination, and a secondary electron collector provided at the front of the secondary electron detector. It is characterized by comprising a collection electrode to which a voltage is applied, and two arms extending from the collection electrode at the same potential as the collection electrode so as to surround a part of the objective lens wall.

[0006]

The scanning electron microscope according to the present invention has two arms extending from the collecting electrode to surround a part of the objective lens wall at the same potential as the collecting electrode to which the secondary electron collecting voltage is applied. And efficiently detect secondary electrons generated from the sample.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows a main part of a scanning electron microscope according to one embodiment of the present invention. A sample stage 5 is disposed below a conical objective lens 4. A sample 6 is placed on the sample stage 5. Sample stage 5
Is configured to be tiltable about O on the sample surface, and the state at the time of maximum tilt is indicated by a dotted line in the figure.
A secondary electron detector 7 is arranged along the conical wall of the objective lens 4 at a position of the conical objective lens 4 opposite to the tilt direction of the sample 6. A scintillator 8 is provided in the detector 7, and a detection signal is obtained based on light generated by collision of secondary electrons with the scintillator 7.
A secondary electron collecting electrode 9 in a mesh shape is attached to the tip of the detector 7, and a voltage of about 100 V is applied to the collecting electrode 9 from a power supply (not shown). A part of the collection electrode 9 has two arms 1 by soldering.
0 and 11 are attached, and each arm is formed by bending a wire. The arms 10 and 11 are formed of a non-magnetic conductive material and have the same potential as the electrode 9. The arms 10 and 11 extend to the side of the objective lens 4 as shown in the plan view of FIG. The operation of such a configuration will now be described.

First, normal sample observation is performed by appropriately tilting the sample 6, but since the secondary electron detector 7 is disposed at a position facing the tilted sample surface, a signal at the time of sample tilt is provided. It has a very excellent structure for detection. Here, when the electron beam is scanned across a predetermined pattern of the sample 6, secondary electrons are generated with the scanning. The generated secondary electrons are efficiently guided to and detected by the secondary electron detector by a voltage of about 100 V applied to the arms 10 and 11. That is, 2 from the slope not facing the detector 7
Even the secondary electrons are guided toward the detector 7 by the voltage applied to the arms 10 and 11 and collide with the scintillator 8 to which a relatively high positive voltage is applied. As a result, the second
As shown in FIG. 3C, among the secondary electron detection signals based on the pattern, a signal having extremely excellent symmetry of the signal on the side of the pattern is obtained. The length measurement is performed.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, although a wire-shaped arm that is easy to manufacture is used as the arm, it may be a mesh-shaped arm or a plate-shaped arm.

[0010]

As described above, the scanning electron microscope according to the present invention has two arms which have the same potential as the collection electrode and extend from the collection electrode so as to surround a part of the objective lens wall. Therefore, even if a single detector is used, a secondary electron detection signal with good symmetry can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a sample to be measured.

FIG. 2 is a diagram showing a secondary electron detection signal.

FIG. 3 is a diagram showing a main part of a scanning electron microscope according to one embodiment of the present invention.

FIG. 4 is a plan view of the arms 10 and 11;

[Explanation of symbols]

 4 Objective Lens 5 Sample Stage 6 Sample 7 Secondary Electron Detector 8 Scintillator 9 Collection Electrode 10, 11 Arm

Claims (1)

(57) [Claims] 1. A conical objective lens, a tilted sample stage disposed at the bottom of the conical objective lens for tilting a sample about an optical axis, and a conical objective lens at a position where the sample does not collide with the tilt. A secondary electron detector disposed obliquely along the wall of the objective lens, a collection electrode provided in front of the secondary electron detector, to which a secondary electron collection voltage is applied, and a collection electrode And two arms extending from the collection electrode to surround a part of the objective lens wall at the same potential.