JPH09147783A - Method and device for measuring configuration of sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quantitatively measure the configuration of a sample by irradiating a sample with electrons, and detecting within a predetermined solid angle backscattered electrons produced from the sample surface for quantitative measurements of the sample configuration and for analysis of its composition. SOLUTION: When a sample is irradiated with S an electron beam EB from an electron gun 10, backscattered electrons BSE, secondary electrons SE, and characteristic X rays XR, emitted from the surface of the sample S, are detected respectively by a backscattered electron detector 1, a secondary electron detector 4, and a characteristic X-ray detector 5. The detector 1 is arranged immediately above the sample S in axial symmetry with respect to the electron beam EB in order to detect the electrons BSE within a predetermined solid angle, and has its detecting part divided into numerous parts. The electrons BSE detected by the detector 1 are amplified by a backscattered electron amplifier 6, are synchronized by an observation-CRT signal synchronizing device 7 with the scanning of the electron beam EB, and displayed on an observation CRT 8 simultaneously with images of the secondary electrons SE and the characteristic X-rays XR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a sample shape by backscattering electrons detected within a predetermined solid angle and simultaneously analyzing the composition.

[0002]

2. Description of the Related Art Conventionally, as a sample shape measuring method using an electron beam, as disclosed in, for example, Japanese Patent Publication No. 1-211849, a method of capturing and analyzing secondary electron images from different angles has been used. Came. However, since this method uses secondary electrons, it is possible to qualitatively obtain a three-dimensional shape, but quantitative analysis such as surface roughness cannot be performed.

As one of means for solving the problem, a method of detecting by a ring-type four-division semiconductor type backscattered electron detector 1 as shown in FIG. 2 has been performed. That is, as shown in the drawing, the sample S is irradiated with the electron beam EB, and the backscattered electrons BSE emitted from the surface of the sample S are transferred to the annular type 4
The unevenness information corresponding to the surface roughness of the sample is obtained by detecting with the detection elements A, B, C, D arranged at axially symmetric positions of the split semiconductor type backscattered electron detector 1. Of.

Now, assuming that the intensities detected by the detecting elements A and B at the symmetrical positions are I _A and I _B , the depth Z of the recess of the sample S can be obtained by the following equation (1). Z = k∫tan θdx = k∫ {(I _A −I _B ) / (I _A + I _B )} dx ……………… (1) where k is a proportional constant, θ is the tilt angle of the sample S. Is.

Similar results can be obtained by using the detection elements C and D. However, since the proportionality constant k in the above equation (1) varies depending on the composition of the sample S, the relationship between the sample tilt angle and the backscattered electron intensity differs depending on the sample composition. An example is shown in FIG. In this figure, □ indicates Al, Δ indicates Fe, and ○ indicates W. FIG. 4 shows the influence of the composition on the difference between the measured value and the calculated value of the Vickers indentation depth of the sample S. From this figure, it can be seen that the Vickers indentation depth is affected by the composition of the sample S. Therefore, as shown in FIG. 5, a standard substance such as Pt-Pd was vapor-deposited in a film on the surface of the sample S and the backscattered electron intensity was normalized to cancel the influence of the composition.

[0006] Next, the acceleration voltage dependence of the specimen rotation angle and the backscattered electron intensity _{E {= (I A -I B} ) / (I A + I B)} electron beam in FIG. In this figure, □ indicates 5k
V and △ are 10kV, and ○ are 15kV. The composition of the sample was Fe. As can be seen from this figure, the relationship between the sample tilt angle and the backscattered electron intensity is influenced by the acceleration voltage of the electron beam.

[0007]

However, if the sample surface is vapor-deposited with a standard substance, the original form of the sample may be impaired, and the characteristic X generated by electron beam irradiation at the same time as the sample shape measurement. There is a problem that the composition analysis by the line cannot be performed. The present invention has been made to solve the above-described problems of the conventional art, and an object of the present invention is to provide a sample shape measuring method and apparatus capable of composition analysis.

[0008]

According to a first aspect of the present invention, there is provided:
The sample is irradiated with an electron beam, the backscattered electrons generated from the sample surface at that time are detected within a predetermined solid angle, this signal is calculated, and then image processing is performed to quantitatively measure the shape of the sample and at the same time. It is a sample shape measuring method characterized by composition analysis.

A second aspect of the present invention is an electron gun for irradiating a sample with an electron beam, a backscattered electron detector for detecting backscattered electrons generated from the sample surface within a predetermined solid angle,
A sample shape measuring apparatus comprising: a backscattered electron image calculation means for calculating a detected backscattered electron image and a composition analysis means for composition analysis.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of the sample shape measuring apparatus of the present invention. In this figure, 1 is a backscattered electron detector, 2 is an electron gun, and 3 is a sample shape measuring apparatus main body control unit. 4 is a secondary electron detector, 5 is a characteristic X-ray detector, 6 is a backscattered electron amplifier, 7 is a signal synchronizer for an observation CRT, 8 is an observation CRT, and 9 is a backscattered electron image calculation means. 10 is a CRT for displaying the sample shape.

Therefore, when the sample S is irradiated with the electron beam EB from the electron gun 2, the backscattered electrons emitted from the surface of the sample S.
The BSE, the secondary electron SE and the characteristic X-ray XR are detected by the backscattered electron detector 1, the secondary electron detector 4 and the characteristic X-ray detector 5, respectively. Backscattered electron detector 1 is a backscattered electron
In order to detect BSE within a predetermined solid angle, the sample is arranged immediately above the sample S in axial symmetry with respect to the electron beam EB, and the detector is divided into a large number. The backscattered electron BSE detected by the backscattered electron detector 1 is amplified by the backscattered electron amplifier 6, and is synchronized with the scanning of the electron beam EB by the signal synchronizer 7 for the observation CRT. It is displayed on the observation CRT 8 simultaneously with the X-ray XR image.

On the other hand, the intensity E _i ^* of the backscattered electron BSE amplified by the backscattered electron amplifier 6 is obtained by the backscattered electron image calculation means 9 by the following equation (2). E _i ^* = I _i / ΣI _i (2) Here, the four backscattered electron detectors 1 have four detection elements A,
Assuming that an annular four-divided semiconductor system including B, C and D is used, the above i is i = A, B, C and D. And
Taking the case of the detector A as an example, its backscattered electron intensity E _A
^{When *} is calculated, it is expressed by the following equation (3).

[0013] ^{_{E A * = I A / (}} I A + I B + I C + I D) .................. (3) then calculates the sample shape Z using supra (1), the sample shape display Display on CRT10 for use. As described above, according to the present invention, since it is not necessary to deposit a standard substance such as Pt-Pd in a film shape on the sample surface, the characteristic X-rays emitted during electron beam irradiation without impairing the original form of the sample. By detecting XR, composition analysis can be performed simultaneously.

Further, according to the present invention, since the backscattered electron intensity is not influenced by the composition and the acceleration voltage, it can be seen that the amount of backscattered electrons detected within a predetermined solid angle is constant.

[0015]

EXAMPLES Three types of shapes of the composition of the sample S, Al, Fe and W, were measured using the sample shape measuring device of the present invention.
At this time, the backscattered electron detector 1 uses an annular four-divided semiconductor system having four detection elements A, B, C, and D, and the backscattered electron intensity E _A ^* of the detection element A is described above. It was calculated by the equation (3). The relationship between the sample tilt angle and the backscattered electron intensity is shown in FIG. As is clear from FIG. 7, the backscattered electron intensity of each sample S is proportional to the sample tilt angle, and it is clear that the composition of sample S has no effect.

FIG. 8 shows the acceleration voltage dependence of the relationship between the sample tilt angle and the backscattered electron intensity obtained by the means of the present invention. The composition of sample S used at this time was Fe
Then, the accelerating voltage was changed in 3 steps of 5 kV, 10 kV and 15 kV. As is clear from a comparison between FIG. 8 and FIG. 6 obtained by means of the conventional method, the backscattered electron intensity fluctuates when the acceleration voltage is increased, whereas it hardly changes in the present invention.

[0017]

As described above, according to the present invention,
Since the divided backscattered electron detectors that are axisymmetric to the electron beam are used and the intensity of one detector is divided by the sum of the intensities detected by all detectors, the sample surface is evaporated with a standard substance. The sample shape can be quantitatively measured without doing so. As a result, the shape measurement that reflects the original shape of the sample can be performed, and at the same time, the composition analysis by the characteristic X-ray can be performed. Furthermore, since it is not necessary to deposit the standard substance on the sample surface, it is possible to contribute to work efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment according to the present invention.

FIG. 2 is a perspective view showing a conventional example.

FIG. 3 is a characteristic diagram showing a relationship between a sample tilt angle and backscattered electron intensity according to a conventional example.

FIG. 4 is a characteristic diagram showing a difference between a measured value and a calculated value of Vickers indentation depth according to a conventional example.

FIG. 5 is an explanatory diagram of Vickers indentation.

FIG. 6 is a characteristic diagram showing the relationship between the sample tilt angle and the backscattered electron intensity when the acceleration voltage is changed in the conventional method.

FIG. 7 is a characteristic diagram showing an example of the relationship between the sample tilt angle and the backscattered electron intensity according to the present invention.

FIG. 8 is a characteristic diagram showing the relationship between the sample tilt angle and the backscattered electron intensity when the acceleration voltage is changed in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Backscattered electron detector 2 Electron gun 3 Sample shape measuring device main body control unit 4 Secondary electron detector 5 Characteristic X-ray detector 6 Backscattered electron amplifier 7 Signal synchronizer 8 Observation CRT 9 Backscattered electron image calculation means 10 Sample shape display CRT EB Electron beam BSE Backscattered electron SE Secondary electron XR Characteristic X-ray S sample

Claims (2)

[Claims] 1. A sample is irradiated with an electron beam, and backscattered electrons generated from the sample surface at that time are detected within a predetermined solid angle,
A method for measuring the shape of a sample, characterized in that the signal is calculated, and then image processing is performed to quantitatively measure the shape of the sample, and at the same time, the composition is analyzed. 2. An electron gun for irradiating a sample with an electron beam, a backscattered electron detector for detecting backscattered electrons generated from the sample surface within a predetermined solid angle, and a detected backscattered electron image is calculated. A sample shape measuring apparatus comprising: a backscattered electron image calculation means and a composition analysis means for composition analysis.