JPH08162061A - Electron microscope - Google Patents

Abstract

PURPOSE: To detect the inclination or irregular state of a sample surface without rotating the sample, and provide an image observed from a certain specified direction. CONSTITUTION: An electron detecting system 30 has a reflected electron detecting part 31 for detecting a reflected electron and a secondary electron detecting part 32 for detecting a secondary electron, and the reflected electron detecting part 31 is formed of four circumferentially divided electrodes 31a, 31b, 31c, 31d. The reflected electron generated from the surface of a sample 10 is detected by the four divided electrodes 31a, 31b, 31c, 31d, whereby a form observation such as the inclination or irregular state of the surface of the sample 10 can be easily performed without rotating the sample 10. Further, the images by the reflected electron and the secondary electron are mutually superposed, whereby an image with good contrast can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron microscope, and more particularly to an electron microscope capable of detecting the state of inclination and unevenness of a sample surface such as a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, a scanning electron microscope utilizing a low-accelerated electron beam has been used as an apparatus for inspecting particles existing on the surface of a sample and the shape of the surface of the sample.

On the other hand, an electron microscope having a multilayer thin film structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-299049. In the electron microscope disclosed in this publication, a sensor including an electron scanning system that emits electrons and an electron detection system that detects electrons that have entered the surface and outputs a detection signal is manufactured by using a semiconductor process. It is a product of the above.

In a conventional electron microscope, detection of electrons is performed by one detection electrode for detecting secondary electrons or reflected electrons, and secondary electrons or reflected electrons generated when the sample is irradiated with an electron beam are detected. Upon detection, an image having a contrast of light and dark corresponding to the shape and physical properties of the sample surface is displayed on the display unit for observation.

[0005]

However, in the above-mentioned conventional electron microscope, the image by the secondary electron is an image observed from directly above the sample surface, and the image by the reflected electron is in the direction of the detection electrode. However, there is a problem in that the inclination of the sample surface and the state of unevenness cannot be detected.

Further, in order to obtain an image observed from a certain specific direction, it is necessary to rotate the sample, and there is a problem that a rotation mechanism for that is required.

The present invention has been made in view of the above circumstances, and provides an electron microscope which detects an inclination or unevenness of a sample surface and obtains an image observed from a specific direction without rotating the sample. The purpose is to

[0008]

To achieve the above object, the present invention provides a fine electron source, an electronic scanning system for scanning an electron beam emitted from the electron source, and a scanning by this electronic scanning system. In an electron microscope in which a plurality of sensor units each including an electron detection system that detects electrons generated from the sample surface when the sample electron beam is irradiated to the sample surface are arranged, the electron detection system detects reflected electrons. The detector is provided with a detector and a secondary electron detector for detecting secondary electrons, and the backscattered electron detector is composed of a plurality of divided electrodes.

Further, the electron microscope of the present invention is characterized in that the electrodes of the backscattered electron detection section are divided in the circumferential direction.

Further, the electron microscope of the present invention is characterized in that the electrodes of the backscattered electron detector are divided into a circumferential direction and a radial direction.

[0011]

In the electron microscope of the present invention, the electron detection system includes a backscattered electron detection section for detecting backscattered electrons and a secondary electron detection section for detecting secondary electrons, and the backscattered electron detection section is divided into a plurality of sections. Since, for example, the electrodes are divided in the circumferential direction, the backscattered electrons generated from the sample surface are detected by the divided electrodes, the sample surface tilts without rotating the sample. It is easy to observe the shape such as the state of unevenness and unevenness, and an image with good contrast can be obtained by superimposing images of reflected electrons and secondary electrons.

Further, in the electron microscope of the present invention, since the electrodes of the backscattered electron portion are divided in the circumferential direction and the radial direction, the inclination of the sample surface can be accurately detected by accurately detecting the inclination of the sample surface. To be observed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of an electron microscope of the present invention. This electron microscope directs an electron beam toward a sample 10 (see FIG. 2) such as a semiconductor wafer mounted on a mounting table. An electron scanning system 20 for irradiating, and an electron detection system 30 for detecting electrons generated from the surface of the sample 10 when the electron beam scanned by the electron scanning system 1 is irradiated on the sample 1 and outputting a detection signal s. A sensor unit 40 formed by arranging a plurality of
It is composed of an arithmetic control unit 50 that controls the sensor unit 40 and processes the detection signal s output from the sensor unit 40.

The sensor section 40, as shown in FIG.
For example, a plurality of units are formed on a silicon substrate 60 having a diameter of 6 to 8 inches by using a normal thin film process, and one unit of the sensor unit 40 is configured to have a size of 10 μm to 1 mm square, for example, and a matrix is formed on the entire surface of the silicon substrate 60. It is made into a shape.

As shown in FIG. 2B, the electronic scanning system 20 is an emitter electrode which is formed on a silicon substrate 60 in a sharp projection shape (cone shape) and emits electrons 70 described later.
21, a base electrode 22 that draws electrons 70 from the emitter electrode 21, and an electron 70 that is drawn by the base electrode 22.
An anode electrode 23 for accelerating the electron and a deflecting electrode 24 for deflecting the electron 70 in an arbitrary direction are sequentially stacked, and the emitter electrode 21, the base electrode 22, the anode electrode 23, and the deflecting electrode 24 are each formed of an insulating film ( (Not shown) are insulated from each other. In addition, as shown in FIG. 2C, the base electrode 22 and the anode electrode 23 are formed to have substantially concentric circular holes centered on the tip of the emitter electrode 21, and
The deflection electrode 24 is composed of two pairs of positive and negative electrodes divided into four, and the scanning range can be controlled so that the deflection angle of the electron beam can be changed depending on the level of the potential difference between the two electrodes to perform raster scanning. It has become.

The electron detection system 30 is shown in FIGS.
As shown in (c), the electronic scanning system 20 is mounted on the silicon substrate 60.
Is formed in a substantially concentric circle around, the backscattered electron detection unit 31 for detecting backscattered electrons 71 from the surface of the sample 10 described later, and is provided outside the backscattered electron detection unit 31, described later from the surface of the sample 10. And a secondary electron detection unit 32 that detects the secondary electrons 72. The backscattered electron detector 31 comprises a plurality of, for example, four electrodes 31a, 31b, 31c, 31d divided in the circumferential direction, and each of the divided electrodes 31a, 31b, 31c, 31d detects the backscattered electron. The current signals S1, S2, S3, S4 corresponding to 71 are output to the arithmetic control unit 50. In addition, the secondary electron detector 32 is shown in FIG.
As shown in FIG. 3, an electrode 32a that attracts the secondary electrons 72, a scintillator 32b that converts the rushed secondary electrons 72 into photons, a light pipe 32c that allows the photons to pass, and a photomultiplier 32d that multiplies the photons into electrons. And outputs a current signal S5 corresponding to the detected secondary electron 72 to the arithmetic and control unit 50. Further, the four divided electrodes 31a, 31b, 31c, 31d are insulated from each other by an insulating film, and similarly, the backscattered electron detection unit 31 and the secondary electron detection unit 32 are also insulated from each other by an insulating film.

The arithmetic control unit 50 includes a first power source 51 for supplying driving power to the electronic scanning system 20, a second power source 52 for supplying driving power to the electronic detection system 30, a first power source 51 and a second power source. And a voltage control unit 53 for controlling the voltage of the driving power supplied to the electronic scanning system 20 and the electronic detection system 30 by the power source 52, respectively.
And controls the operation of the entire electron microscope and sensor unit
An arithmetic control circuit 54 that arithmetically processes the detection signal s output from the electronic detection system 30 of 40, an input unit 55 including a console that inputs an instruction such as an inspection start by the sensor unit 40,
And C which displays image information and the like obtained by the arithmetic processing based on the detection signal s output from the electronic detection system 30 on the screen.
The display unit 55 includes an RT display and the like. In addition, the detection signal s corresponds to each electrode of the backscattered electron detection unit 31.
Current signals S1, S2, S3, S4 output from 31a, 31b, 31c, 31d
And a current signal S5 output from the photomultiplier 32d of the secondary electron detector 32.

Next, the operation of the embodiment of the present invention will be described with reference to FIG.

When drive power is applied to the electronic scanning system 20 and the electron detection system 30 from the first power source 51 and the second power source 52, respectively, first, the base electrode 22 causes the electron 70 to be extracted from the emitter electrode 21. The extracted electrons 70 are accelerated by the anode electrode 23, further deflected in an arbitrary direction by the deflection electrode 24, and irradiated on the sample 10. The electrons 70 with which the sample 10 is irradiated generate reflected electrons 71 and secondary electrons 72 from the surface of the sample 10.

The backscattered electrons 71 generated from the surface of the sample 10 are detected by the backscattered electron detector 31. That is, backscattered electrons
Since 71 has high kinetic energy, it travels straight without applying drive power to the backscattered electron detector 31 and reaches the four divided electrodes 31a, 31b, 31c, 31d of the backscattered electron detector 31, Current signals S1, S2, S3, S4 are generated respectively, and these current signals are output to the arithmetic and control circuit 54. The direction of generation of the reflected electrons 71 is the angle of incidence of the electrons 70 on the surface of the sample 10, that is, the sample.
Sample 10 depends on the surface shape such as inclination and unevenness of 10
The amount of backscattered electrons 71 reaching the four divided electrodes 31a, 31b, 31c, 31d of the backscattered electron detection unit 31 varies depending on the surface shape of the above. For example, in the case of the surface shape of the sample 10 as shown in FIG. 4, the amount of backscattered electrons 71 reaching the electrode 31d is larger than the amount of backscattered electrons 71 reaching the electrode 31b.

As described above, the current signals S1, generated in the four divided electrodes 31a, 31b, 31c, 31d of the backscattered electron detector 31, are generated.
Since S2, S3, and S4 reflect the surface shape of the sample 10, the arithmetic control circuit 54 compares and analyzes these current signals S1, S2, S3, and S4 to obtain the image information of the surface shape of the sample 10. By displaying this image information on the display unit 55 while being obtained, the surface shape of the sample 10 can be observed.
In addition, the four electrodes 31a, 31b, 31c, 31d of the backscattered electron detector 31
The image information generated by the
Reflecting the information obtained by observing the sample 10, an image obtained by observing the sample 10 from four directions can be obtained without rotating the sample 10.

Further, secondary electrons generated from the surface of the sample 10
72 is detected by the secondary electron detector 32. That is, since the secondary electrons 72 have low kinetic energy, the secondary electron detector
By applying driving power to the electrode 32a of 32, the secondary electrons 72 are attracted to the electrode 32a. The secondary electrons 72 attracted to the electrode 32a are converted into photons by the scintillator 32b and pass through the light pipe 32c, and then the photomultiplier 32
The electrons are multiplied by d, and the photomultiplier 32d outputs the current signal S5 to the arithmetic control circuit 54. The image information by the current signal S5 based on the detected secondary electrons 72 is more effective than the image information by the current signals S1, S2, S3, S4 based on the backscattered electrons 71 as if illuminated by non-directional illumination. Therefore, a soft shaded image of the sample 10 as seen from directly above is obtained, and by displaying this image on the display unit 55, observation is possible.

According to the above embodiment, the electron detection system 30 has the backscattered electron detector 31 for detecting backscattered electrons 71 and the secondary electron detector 32 for detecting the secondary electrons 72. Is composed of four electrodes 31a, 31b, 31c, 31d divided in the circumferential direction.
By detecting the electrodes 31a, 31b, 31c, 31d divided into four pieces, it is possible to easily observe the shape of the surface of the sample 10 such as the inclination and the unevenness of the sample 10 without rotating the sample 10. Further, by superimposing the images of the reflected electrons 71 and the secondary electrons 72, an image with good contrast can be obtained.

In the above embodiment, the backscattered electron detector 31 is used.
Is composed of four circumferentially divided electrodes 31a, 31b, 31c, 31d, but the invention is not limited to this, and two or more electrodes of the backscattered electron detection unit 31 can be arranged in the circumferential direction. Can be divided into

Further, the electrodes of the backscattered electron detecting portion 31 may be divided not only in the circumferential direction but also in the concentric circular direction and further in the radial direction as shown in FIG. That is, FIG. 5 is an enlarged front view of a sensor unit 41 according to another embodiment of the present invention. The backscattered electron detection unit 31 is divided into four in the circumferential direction and three in the radial direction, for a total of 12 pieces. Each of the electrodes 31a1, 31a2, 31a3, 31b1, ..., 31d1, 31d2, 31d3 is provided, and a current signal is output to the arithmetic control circuit 54 from each of the divided electrodes. Since the arithmetic control circuit 54 compares and analyzes the current signals subdivided from the above embodiments, the image information of the surface shape of the sample 10 can be obtained finely, so that the inclination of the surface of the sample 10 can be accurately detected. As a result, the surface inclination of the sample 10 can be precisely observed.

In the above embodiment, the secondary electron detector 32
Is provided outside the backscattered electron detection unit 31, but not limited to this, the secondary electron detection unit 32 is inside, the backscattered electron detection unit
31 may be outside.

In the above embodiment, the sensor section 40 is formed on the silicon substrate 60.
However, other materials may be used as long as they can be finely processed.

Further, the electron detection system 30 is not limited to the structure shown in the figure, and it is possible to detect the reflected electrons 71 or the secondary electrons 72 from the surface of the sample 10 and to detect the electron scanning system 20 on the same substrate surface. If it can be finely processed adjacent to
Other structures may be used.

Further, the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made.

[0031]

As described in detail above, according to the electron microscope of the present invention, the electron detection system includes the backscattered electron detection section for detecting backscattered electrons and the secondary electron detection section for detecting secondary electrons. However, since the backscattered electron detection unit is composed of a plurality of divided electrodes, for example, electrodes divided in the circumferential direction, by detecting the backscattered electrons generated from the sample surface with a plurality of divided electrodes, It is possible to easily observe the shape of the sample surface such as inclination and unevenness without rotating the sample, and to obtain a high-contrast image by superimposing the images of backscattered electrons and secondary electrons. You can

Further, in the electron microscope of the present invention, since the electrodes of the backscattered electron section are divided in the circumferential direction and the radial direction, fine image information of the sample surface can be obtained, so that the inclination of the sample surface can be accurately measured. It can be detected and the inclination of the surface of the sample can be precisely observed.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of an electron microscope according to the present invention.

2A and 2B are diagrams showing a configuration of a sensor, FIG. 2A is a diagram showing that a plurality of sensor portions are arranged in a matrix, and FIG. 2B is an enlarged cross-sectional view of the sensor portion. , And FIG. 2C are enlarged front views of the sensor unit.

FIG. 3 is a diagram showing a configuration of a secondary electron detection unit.

FIG. 4 is a diagram showing an operation of a sensor unit.

FIG. 5 is an enlarged front view of a sensor unit according to another embodiment of the present invention.

[Explanation of symbols]

10 ... Sample 21 ... Emitter electrode (electron source) 20 ... Electron scanning system 30 ... Electron detection system 31 ... Reflected electron detection unit 31a, 31b, 31c, 31d, 31a1, 31a2, 31a3, 31b1, ..., 31d1, 31d2, 3
1d3 ... Electrode 32 ... Secondary electron detector 40, 41 ... Sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Akama 33 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture

Claims (3)

[Claims] 1. A fine electron source, an electron scanning system for scanning an electron beam emitted from the electron source, and a sample surface when the electron beam scanned by the electron scanning system is irradiated on the sample surface. In an electron microscope in which a plurality of sensor units including an electron detection system that detects generated electrons are arranged, the electron detection system includes a backscattered electron detection unit that detects backscattered electrons, and a secondary electron detection unit that detects secondary electrons. And an electron microscope, wherein the backscattered electron detection section is composed of a plurality of divided electrodes. 2. The electron microscope according to claim 1, wherein the electrodes of the backscattered electron detector are divided in the circumferential direction. 3. The electron microscope according to claim 1, wherein the electrode of the backscattered electron detection section is divided into a circumferential direction and a radial direction.