JPH03165438A - Charged particle beam device - Google Patents

Abstract

PURPOSE:To regulate the spatial effect by composing a pair of reflection electron detecting elements to regulate the position as desired at the position on the same plane almost vertical to a charged particle beam. CONSTITUTION:When an electron beam 1 is radiated on a sample 4 on a sample stage 3, signals of the secondary electrons, the reflecting electrons, and the like are generated from the surface of the sample 4. Of these signals, the reflecting electrons 5a and 5b are in the same directions separated from the scanning area of the incident electron beam 1, and they can be detected by a pair of semiconductor reflection electron detecting elements 6a and 6b which are provided on the same plane almost vertical to the incident electron beam 1. The detected signals include the composition signal and the unevenness signal of the sample 4 surface respectively at the same time, and since the detecting elements 6a and 6b are provided in the same direction to the incident electron beam 1, a stereoscopic picture image including the composition signal and the unevenness signal can be formed by adding and processing the signals detected by the detecting elements 6a and 6b.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention involves two-dimensionally scanning a charged particle beam such as an electron beam over a sample, and converting backscattered electrons generated from the sample during this scanning into a pair of In particular, regarding charged particle beam devices such as scanning electron microscopes that detect with a backscattered electron detection element and display a sample image based on the output signals of this pair of detection elements,
A pair of backscattered electron detection elements is configured so that it can be shifted to one side outside the scanning area of a charged particle beam such as an electron beam, making it possible to display a three-dimensional image of the sample in addition to the composition image and unevenness image of the sample. It relates to a charged particle beam device.

[Conventional technology]

A charged particle beam such as an electron beam is scanned two-dimensionally over a sample using a conventional scanning electron microscope or an electron probe microanalyzer (EPMA), and the backscattered electrons generated from the sample during this scanning are captured by a pair of reflected electrons. In a charged particle beam device in which an electron detection element is used to display a sample image based on the output signals of a pair of detection elements, a semiconductor element is used to detect reflected electrons at a symmetrical position with respect to the incident electron beam. A detection element was placed. Arrange the backscattered electron detection element like this! Then, by processing the backscattered electron signal generated from the sample, it is possible to separate it into a composition signal and an unevenness signal, and form a composition image and an unevenness image, respectively.

To explain this point using the explanatory diagram in Figure 6, (a
), the intensity of the backscattered electrons is approximately proportional to the atomic number. The detection signal from the backscattered electron detecting element A arranged is as shown in the figure, and the detection signal by the backscattered electron detecting element 2 arranged on the right side of the incident electron beam is as shown in the figure B. Therefore, the sum of signals A and B is signal A+B
The difference between them becomes signal A-B.

Since the backscattered electron detection elements A and B are arranged symmetrically with respect to the incident electron beam, the sum signal A + B becomes a composition image representing the composition distribution of the sample, but the difference signal -B becomes zero and there is no It also has no image signal. Furthermore, if the sample has no difference in composition and only a difference in surface roughness as shown in Figure 6(b), the amount of backscattered electrons incident on the left and right backscattered electron detection elements A and B is the amount of incident electrons. This varies depending on the inclination of the surface of the point where the beam strikes, so for example, as shown in the figure, the detection signal from backscattered electron detection element 8 will be as shown in figure A, and the detection signal by backscattered electron detection element 2 will be as shown in figure B. . Therefore, the sum of signals A and B becomes signal A+B, and the difference between them becomes signal A-B. Since the total amount of reflected electrons entering the reflected electron detection element A can be considered to be constant, the sum signal A+B has a constant value and does not include any image signal. On the other hand, the difference signal A-B becomes an uneven image representing the unevenness of the surface as shown in the figure. Therefore, a composition image of the sample can be obtained from the summed signal of the signals from the rain detection elements, and an uneven image of the sample can be obtained from the subtracted signal.

The concave-convex image referred to here is an image viewed from directly above when a sample placed horizontally is illuminated, and it lacks a three-dimensional effect and is useful for observing samples with extremely uneven sample surfaces. is not suitable. In addition, in a backscattered electron detector consisting of a pair of detection elements A and B arranged symmetrically with respect to the incident electron beam, structurally and in principle, the sample is tilted so that the chamber body can be viewed from all directions. Unable to form an image. The reason for this is that such a backscattered electron detector must be placed close to the sample, and if an attempt is made to tilt the sample, there is a risk that the sample will hit either the Δ or B detection element.

On the other hand, a secondary electron detector consisting of a scintillator, a light guide, and a photomultiplier tube placed on one side of the incident electron beam has a three-dimensional In addition to being able to form a wide-angle image, it is also possible to tilt the sample. However, a three-dimensional image formed by a secondary electron detector composed of a scintillator, a light guide, and a photomultiplier tube is a secondary electron image, not a backscattered electron image. Moreover, this image naturally includes both a composition signal and an unevenness signal, and it is not possible to separate these signals and display only the composition image or only the unevenness image. Furthermore, in such a secondary electron detector, a high voltage is applied to the front surface of the scintillator, so if it is placed in a low vacuum, a discharge will occur, so there is a problem that it cannot be used in a low vacuum scanning electron microscope. [Problems to be Solved by the Invention] The present invention was completed in order to solve the problems of the two types of electron detectors as described above. In scanning electron microscopes and other devices that use The object of the present invention is to provide an apparatus that can display only a composition image or only a concavo-convex image by separating the concave-convex signal and the concave-convex signal.

[Means to solve the problem]

The present invention has been completed to achieve the above object. That is, the charged particle beam device of the present invention, such as a scanning electron microscope, scans a charged particle beam such as an electron beam two-dimensionally over a sample, and collects reflected electrons generated from the sample during this scanning into a pair of reflected electrons. In an apparatus in which a sample image is displayed by selecting one of the signals detected by electron detection elements and the output signals of the pair of detection elements being summed or subtracted, the pair of backscattered electron detection elements are The structure is such that the position can be adjusted from a symmetrical arrangement position with respect to the particle beam to a position in the same direction outside the scanning area of the charged particle beam and on the same plane substantially perpendicular to the charged particle beam. It is characterized by the fact that

In this case, a processing device that obtains a backscattered electron image of the sample by processing signals obtained from the pair of backscattered electron detection elements;
Since the apparatus includes a processing device that performs subtraction processing on the signal to obtain a backscattered electron image of the sample, it is possible to selectively display a three-dimensional image, a composition image, or an uneven image of the sample.

Note that a semiconductor element is typically used as the reflected electron detection element.

[Effect]

A pair of backscattered electron detection elements are placed in the same direction away from the scanning area of the charged particle beam while remaining integrated from a symmetrical arrangement position with respect to the charged particle beam such as an electron beam, and approximately perpendicular to the charged particle beam. Since the position can be adjusted on the same plane, three types of images can be formed: a three-dimensional image, a composition image, and an uneven image.

In addition, in a three-dimensional image, the appearance of shadows caused by irregularities on the sample surface can be controlled by changing the distance between the pair of backscattered electron detection elements and the charged particle beam, or by changing the two positions of the sample stage (not shown). You can also adjust the three-dimensional effect.

Furthermore, when a pair of backscattered electron detection elements are placed in the same direction away from the charged particle beam scanning area, it is possible to tilt the sample stand without bringing the sample or sample stand into contact with the backscattered electron detection elements. Therefore, it is possible to observe a three-dimensional image of the sample surface from all directions.

[In the present invention, a charged particle beam such as an electron beam is scanned two-dimensionally with a scanning electron microscope, an electron beam probe microanalyzer (EPMA), etc. on a sample, and along with this scanning, The present invention relates to a detector for a charged particle beam device that detects electrons generated from a sample and displays an image of the sample based on the signal.

FIG. 1 is a schematic diagram of a fence illustrating the principle of the present invention.

In the above-mentioned apparatus, the sample chamber 2 kept in vacuum is
It is configured such that an incident electron beam 1 irradiated from an electron source (not shown) scans a sample 4 placed on a sample stage 3 placed inside.

When the electron beam l irradiates the sample 4 on the sample stage 3, signals such as secondary electrons and reflected electrons are generated from the surface of the sample 4. The reflected electrons 5a and 5b are arranged in the same direction away from the scanning area of the incident electron beam 1, separated from each other above the sample 4, and on the same plane substantially perpendicular to the incident electron beam 1. a pair of semiconductor backscattered electron detection elements 6a,
6b. The signals detected by the detection elements 6a and 6b simultaneously include a composition signal and an unevenness signal on the surface of the sample 4, and the signals detected by the detection elements 6a and
Since detection elements 6b are arranged in the same direction with respect to the incident electron beam 1, when the signals detected by detection elements 6a and 6b are combined, a three-dimensional image including a composition signal and an unevenness signal can be formed. can. To explain this a little more,
For example, as shown in Figure 2, if there is a protrusion 4' on the sample 4, when the incident electron beam l hits the right (lU) of the protrusion 4' in the figure, it will come from that point and be placed to the left. The reflected electrons 5a should be incident on the detection elements 6a and 6b.

Since a portion of 5b is obscured by this protrusion 4', the signal detected by the detection elements 6a and 6b becomes weaker than its original strength. Therefore, the image synthesized by the above summed signals is as if the sample 4 were illuminated by placing a light source at the positions of the detection elements 6a and 6b and the sample 4 was viewed from the direction of the incident electron beam 1. The image will have shadows depending on the surface shape of 4, resulting in an image rich in three-dimensionality.

In addition, by changing the distance between the pair of backscattered electron detection elements 6a, 6b and the incident electron beam l, or by changing the position of the sample stage (not shown), the amount of shadow of the unevenness on the sample surface is controlled, You can also adjust the three-dimensional effect. As described above, according to the present invention, the pair of backscattered electron detecting elements 6a and 6b are placed in the same direction outside the scanning area of the incident electron beam 1, and are spaced apart from each other above the sample 4 to detect the incident electron beam. A three-dimensional image of the surface of the sample 4 can be obtained by arranging them on the same plane substantially perpendicular to 1.

FIG. 3 is a schematic diagram when the sample 4 is tilted with respect to the incident electron beam 1 with such an arrangement 2 of the detection elements 6a and 6b, which is suitable for viewing the sample 4 from all directions. This is also effective when attempting to obtain a stereoscopic image using binocular parallax by changing the inclination angle of the sample 4. In this way, in the present invention, the pair of backscattered electron detection elements 6
a and 6b can be arranged in the same direction outside the scanning area of the incident electron beam 1, so even if the sample stage is tilted, the sample or the sample stage can be prevented from coming into contact with the detection elements 6a and 6b. It can be observed tilted.

Moreover, FIG. 4 is a schematic diagram when the semiconductor backscattered electron detection element 6as6b is arranged symmetrically with respect to the incident electron beam 1 across the incident electron beam 1 without changing its relative position. , the sample 4 is irradiated with the incident electron beam 1 through between the detection elements 6a and 6b and scanned. This is exactly the arrangement of the conventional backscattered electron detector shown in FIG. 6, and is a signal obtained by adding up the signal of the detection element 6a that detected the backscattered electrons 5a and the signal of the detection element 6b that detected the backscattered electrons 5b. As described above, when an image is displayed, it becomes a compositional image, and when an image is displayed based on the signals obtained by subtracting these, it becomes a concavo-convex image.

FIG. 5 is a plan view of the output element part of one example of a backscattered electron detector, in which 6a and 6b show semiconductor backscattered electron detection elements, and 7 shows a hole for passing the incident electron beam 1. .

Reference numeral 8 indicates a space between the rain detection elements 6a and 6b. The backscattered electron detection elements 6a and 6b are usually made of a PN junction made of silicon or the like, but are not necessarily limited to this.

In the present invention, the backscattered electron detector consisting of the pair of backscattered electron detection elements 6a and 6b is moved from the position shown in FIG. 1 to the position shown in FIG.
Or, it is possible to form a three-dimensional image that includes a composition signal and an unevenness signal, and only a composition image with the composition signal and unevenness signal separated as necessary. Alternatively, it is possible to configure an apparatus that can form three types of images, including only uneven images.

〔Effect of the invention〕

In a charged particle beam device such as a scanning electron microscope or an electron beam probe microanalyzer according to the present invention, a pair of backscattered electron detection elements are arranged symmetrically with respect to the charged particle beam while remaining integral with the charged particle beam. Since the position can be adjusted to a position in the same direction outside the scanning area of the charged particle beam and on the same plane almost perpendicular to the charged particle beam, three types of images can be obtained: a three-dimensional image, a composition image, and an uneven image. can be formed. In addition, in a three-dimensional image, the amount of shadows caused by unevenness on the sample surface can be controlled by changing the distance between a pair of backscattered electron detection elements and the charged particle beam, or by changing the length of the sample stage (not shown). You can also adjust the three-dimensional appearance of the hair.

Furthermore, when a pair of backscattered electron detection elements are placed in the same direction outside the charged particle beam scanning area, the sample stage can be tilted, allowing three-dimensional images of the sample surface from all directions. can be observed. At this time, the sample stage can have a eucentric structure that allows the sample to be tilted and moved in parallel while keeping the irradiation point of the charged particle beam such as an electron beam on the sample surface. The sample or sample stage can be prevented from coming into contact with the backscattered electron detection element.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the principle of the present invention, Figure 2 is a diagram to explain that the principle of the present invention creates a sample image with a rich three-dimensional effect, and Figure 3 is a diagram showing the sample image. A schematic diagram when tilted with respect to the incident electron beam, Figure 4 is a schematic diagram when the semiconductor backscattered electron detection element is arranged symmetrically with respect to the incident electron beam, and Figure 5 is a schematic diagram of the semiconductor backscattered electron detection element. Figure 6, a plan view of an example of a backscattered electron detector, shows the principle by which a compositional image and a concave-convex image can be separated when a pair of backscattered electron detectors are placed at symmetrical positions with respect to the incident electron beam. This is a diagram for 1 - incident electron beam, 2 - sample chamber, 3 - sample stage, 4 - sample, 4' - protrusion on sample, 5a, 5b - opposing electrons, 6a. 6b-1 semiconductor backscattered electron detection element, 7-hole for incident electron beam passage, 8-m=separation part between pair of backscattered electron detection elements Applicant: Kyoko Technics Co., Ltd.

Claims (1)

[Claims] (1) A charged particle beam such as an electron beam is scanned two-dimensionally on a sample, and a pair of backscattered electron detection elements detect backscattered electrons generated from the sample during this scanning, and the output of this pair of detection elements In a charged particle beam apparatus such as a scanning electron microscope that displays a sample image by selecting one of the signals obtained by adding or subtracting signals, the pair of backscattered electron detection elements are connected to the charged particle beam. It is characterized in that the position can be adjusted from a symmetrical arrangement position to a position in the same direction outside the scanning area of the charged particle beam and on the same plane substantially perpendicular to the charged particle beam. charged particle beam device.