JPS59225310A - Surface roughness measuring apparatus by scanning type electronic microscope - Google Patents

Abstract

PURPOSE:To make it possible to impart an accurate barometer to a surface roughness cross-sectional curve obtained by observing an object to be measured, by parallelly arranging a standard roughness test piece and the object to be measured in the specimen chamber of a scanning type electronic microscope. CONSTITUTION:The specimen 15 and a standard roughness test piece 16 placed on a specimen stand 14 are alternately irradiated with the scanning electron beam of a scanning electronic microscope 12 and reflected electrons are collected by a collector electrode 13 to form an image signal of a surface cross-sectional shape while operation is performed on the basis of magnification set by a manification controller in a calculator 22 through an amplifier 17 and an AD conerter 20. Calibration due to the comparison with the cross-sectional curve obtained with respect to the standard roughness test piece 16 is applied to the surface roughness cross-sectional curve obtained with respect to the specimen 15 to input a barometer and plotted by an output apparatus while the surface rougness cross-sectional curve with the barometer is displayed to a cathode ray tube display apparatus 21.

Description

Detailed Description of the Invention Technical Field The present invention relates to a scanning electron beam that measures the cross-sectional shape of the surface of an object to be measured by integrating image signals from reflected electrons obtained by scanning the surface of the object with an electron beam. This invention relates to a surface roughness measuring device using a microscope, and in particular, is capable of calibrating a surface roughness cross-sectional curve of an object to be measured by attaching a scale to the surface roughness cross-sectional curve.

Prior Art This type of surface roughness measuring device using a scanning electron microscope is known from ``Surface shape measuring device using a scanning electron microscope'' described in Japanese Patent Application Laid-Open No. 150303/1983, which was proposed by the present inventor. However, in conventional surface roughness measurement devices using this type of scanning electron microscope, the surface roughness of the object to be measured is determined by integrating image signals that constitute a backscattered electron image obtained by scanning the object to be measured with an electron beam. However, in order to display an image that represents surface roughness in an appropriate format on an image display device, it is necessary to adjust the output level, magnification, etc. The surface roughness cross-sectional curve obtained by integrating the curve itself accurately reproduces the surface shape of the object to be measured, but the amplitude value of the curve is calibrated to measure the surface roughness. It wasn't easy to figure out what to do.

In other words, conventionally, when measuring the surface roughness of an object using a scanning electron microscope, although a cross-sectional curve that accurately represents the surface roughness is obtained, it is difficult to measure the amplitude of the cross-sectional curve. It was believed that it was not easy to determine its absolute value. To put a scale into the surface roughness cross-sectional curve of the object to be measured, a similar surface roughness cross-sectional curve is drawn for a standard roughness test piece with a cross-sectional shape whose absolute value is a known amplitude, for example, a triangular cross-sectional shape. It was thought to use the absolute value of the amplitude of the cross-sectional curve of the object to be measured and compare the two to determine the scale. Each surface roughness cross-sectional curve obtained by separately observing the above-mentioned observation conditions using a type electron microscope has a slight difference in the absolute value of the amplitude due to subtle differences in the adjustment of each observation condition. As a result, the accuracy of the scale used in the surface roughness cross-sectional curve of the object to be measured is low, making it difficult to obtain reliability sufficient for practical use.

SUMMARY OF THE INVENTION The object of the present invention is to overcome the above-mentioned conventional difficulties and eliminate their drawbacks, and to provide a scanning type that allows the scale to be approximated with sufficient reliability to the surface roughness cross-sectional curve obtained for the object to be measured. An object of the present invention is to provide a surface roughness measuring device using an electron microscope.

However, the surface roughness measuring device of the present invention allows the object to be measured to be observed at any desired magnification by placing a standard roughness test piece alongside the object to be measured in the sample chamber of a scanning electron microscope. It is designed to easily give an accurate measure to the obtained surface roughness cross-sectional curve, and integrates the image signal from the reflected electrons obtained by scanning the surface of the object to be measured with an electron beam. In a scanning electron microscope that measures the cross-sectional shape of the surface of the object to be measured, a standard roughness test piece that serves as a reference for the surface roughness cross-sectional curve is placed near the object to be measured. The present invention is characterized in that a means for calibrating the surface roughness cross-sectional curve is provided.

Therefore, in the measuring device of the present invention, the absolute value of the amplitude of various machined surfaces such as cut surfaces and ground surfaces, as well as the shapes of worn surfaces, etched surfaces, etc. It can be easily measured and greatly contributes to improving the capabilities of various mechanical devices related to these various aspects.

EXAMPLE An embodiment of the present invention will be described in detail below with reference to the drawings.

First, Figure 1 shows the schematic configuration of a scanning electron microscope according to the present invention, with a part cut away, and an enlarged view of the interior of the sample chamber.
The frame is shown. In the illustrated scanning electron microscope 1 a-3, the electron beam emitted from the electron gun 2 is transferred to the focusing coil 3.
While converging the electrons and deflecting them by the deflection coil 4, the sample AS on the sample holder 5 impinges on the object S to be measured, captures the reflected electrons, and forms an image signal, as will be described later. A scaled surface roughness cross-sectional curve of the object to be measured can be obtained through arithmetic processing. The object to be measured S and the standard roughness test piece 9.11 placed on the sample holder 5-1 are positioned at appropriate positions within the field of view of the scanning electron beam.

A sample 1
The sample N'3110 @ is placed in the center of the sample table 8, and the sample 1 is placed in the center of the sample table 8.
A standard roughness test piece 9.11 is also placed on the sample stand 5 close to 0. That is, depending on the shape, size, etc. of the sample 110, as shown in the upper part of the figure, the standard roughness test) is placed on the sample stage 8 very close to the sample 10, or As shown in the lower part of the figure, the standard roughness test piece 11 is placed on the edge of the sample pedestal 5 in the partitioned part of the sample pedestal 8, with a slight distance from the sample 3110. In addition, when mounting in this way, the observation sample 10 must be placed under the same conditions.
Specimen 10J5 and standard roughness specimen 9.11 were prepared so that their surfaces were located within the depth of focus of the scanning electron beam in the same condition. ! t=Roughness At least one of the test specimens 9.11 is placed on a stand of an appropriate height, the heights of both surfaces are the same, and the surface roughness of both is sufficiently the same under the same conditions. jT
A: It is necessary to make it easy to understand. In such a state, if the sample 10 and the standard roughness test piece 9.11 are placed close to each other on the sample mount 5, the other adjustment points will not be touched at all, and simply,
The surface roughness of the sample 10 and the standard roughness test piece 9.11 was measured under almost completely the same observation conditions by only slightly adjusting the position adjustment knob 6.7 that slightly moves the position of the sample holder 5. It is possible to easily calibrate the obtained surface roughness cross-sectional curve with high reliability.

Next, FIG. 3 shows an example of the configuration of the signal processing system of the surface roughness measuring apparatus of the present invention, which is capable of calibrating the surface roughness cross-sectional curve as described above. The signal processing system having the illustrated configuration has a surface roughness measuring section shown enclosed by a broken line, and a digital calculating section for processing surface roughness measurement data obtained by the measuring section. However, in the illustrated configuration, the current value of the deflection current supplied from the scanning power supply 25 to the deflection coil 16 of the scanning electron microscope 12 is switched by the magnification adjuster 18, and the sample is placed on the sample holder 14 at an appropriate magnification. The placed sample 15d5 and the standard roughness test piece 16 are alternately irradiated with a scanning electron beam by moving the mount 14 in the direction of the arrow, and the reflected electrons are collected by the collector electrode 13 to form a surface on each surface. An image signal corresponding to a differential waveform of the shape is formed, and the image signal is supplied via an amplifier 17 to a cathode ray tube display device 21 operated by a scanning N source 25 in the same manner as the scanning electron microscope 12. and display it.

In the surface roughness measuring device of the present invention having the configuration shown in the figure,
The image signal representing the differential waveform of the cross-sectional shape of the object surface obtained as described above is extracted from the surface roughness measurement section and supplied to the analog-to-digital converter 20 of the digital processing section, and the electronic signal from the scanning power supply 25 is It is driven by a clock signal synchronized with beam scanning, converted into a digital image signal, and then supplied to the calculation@22. The calculator 22 performs digital calculations based on the magnification set by the magnification adjuster 18 under the control of the terminal device 19.
The surface roughness cross-section curve obtained for the object to be measured (the main sample 15 is calibrated by comparison with a similar cross-section curve obtained for the standard roughness sample 16, and a scale is added to the surface roughness cross-section curve with the scale). The curve data is supplied to the output device 23 for viewing, and is also supplied to the cathode ray tube display device 21 to display the scaled surface roughness cross-sectional curve.

Therefore, when the surface roughness cross-sectional curve obtained by observing the standard roughness test piece 16 at the magnification α is calculated by the computer 22, and the scale S μm/cm is obtained, the sample 10 as the object to be measured is calculated. Regarding the surface roughness cross-sectional curve obtained by observation at magnification β, the scale (α
/β)Sμm, /Crn1 can be easily obtained. Therefore, an absolute value scale can be included in the surface roughness cross-sectional curve of the object to be measured with an accuracy corresponding to the accuracy of the magnification setting of the apparatus.

FIG. 3 shows an example of the structure of the surface roughness measuring apparatus of the present invention in which signal processing similar to that described above is performed by analog calculation. Also in the illustrated configuration example,
Just as in the configuration example shown in Figure 2, the current value of the deflection current supplied from the scanning power supply 35 to the deflection coil 28 of the scanning electron microscope 27 is switched by the magnification adjuster 34, and the sample mount 30 is adjusted to an appropriate magnification. The sample 31 and the standard roughness test piece 32 placed on the top are alternately irradiated with a scanning electron beam by moving the pedestal 30 in the direction of the arrow, and the reflected electrons are collected by the collector electrode 29 to measure the surface of each surface. An image signal corresponding to a differential waveform of the cross-sectional shape is formed, and the image signal is supplied via an amplifier 33 to a cathode ray tube display device 42 operated in synchronization with a scanning electron microscope 27 by a scanning power supply 35 for display. do.

In the surface roughness measuring device of the present invention having the configuration shown in the figure,
The image signal representing the differential waveform of the cross-sectional shape of the object surface obtained as described above is supplied to the multiplier 38 via the integrator 36. On the other hand, for the surface roughness test piece 32 and the sample 31, the divided voltage of the DC voltage E obtained by switching the resistance voltage divider using the switches 41 and 40 is proportional to the magnification α and β set by the magnification adjuster 34, respectively. The magnification ratio (α/
β) is also supplied to the multiplier 38 and multiplied by the integral output of the integrator 36.

By supplying the absolute value scale data obtained by such multiplication to the cathode ray tube display device 42, the surface roughness cross-sectional curve of the object to be measured can be displayed with a scale based on the standard roughness test piece. .

As explained above, in the surface roughness measuring apparatus of the present invention, the surface roughness test piece 9.
By arranging them side by side, it is possible to switch from the observation image of standard roughness test piece 9.11 to the observation image of sample 10 while maintaining the observation image in a good adjustment state. While the other adjustment states are held constant, only the magnification can be selected and set to the optimal magnification α and β, respectively. In addition, in the signal processing system having the configuration shown in FIG. 2, when moving the sample stand 14 on which the sample 15 and the standard roughness test piece 16 are placed,
First, the standard roughness test piece 16 is observed at a magnification α, and the resulting electronic image signal is digitized by the analog-to-digital converter 20, and then integrated by the computer 22 to obtain a surface roughness cross-sectional curve. Since the surface roughness of the standard roughness test piece 16 is known, the scale SμIll /mark to be included in the surface roughness cross-sectional curve of the sample 15 can be obtained. Next, while keeping the adjustment of the scanning electron microscope 12 in the same state, the sample mount 14 is moved so that the sample 15 is located within the observation field, and the backscattered electron image signal of the sample 15 observed at the magnification β is obtained. By similarly determining the surface roughness cross-sectional curve from , and performing the calculation (α/β)S, it is possible to insert a scale into the surface roughness cross-sectional curve. Therefore, it is possible to easily obtain a much more reliable and accurate measure than with the conventional Ic apparatus, which observes the standard roughness test piece separately from the sample. Furthermore, in the configuration example shown in Figure 3, in response to changing the sample and the standard roughness test piece and selecting the magnification,
By generating a voltage proportional to the magnification, the magnification ratio (
α/β) and multiplying the integration result of the backscattered electron image signal by the magnification ratio, and referring to the similar integration result for the standard roughness test piece, the configuration example shown in Figure 2 (printed) is performed. Similar scaling can be easily done.

FIG. 4 shows an example of the actual measurement results of the surface roughness cross-sectional curve of the object to be measured using the surface roughness measuring apparatus of the present invention which operates as described in detail above.

Effects As is clear from the above explanation, according to the present invention, the following remarkable effects can be obtained in measuring surface roughness using a scanning electron microscope. In other words, as shown in Figure 4, conventionally it was not easy to insert a scale into the surface roughness cross-sectional curve of the object to be measured, and even if a scale was inserted, the standard roughness test piece could not be easily measured. Because the scanning electron microscope was observed separately from the object, the adjustment state of the scanning electron microscope was different, and the accuracy of scale assignment had to be reduced.However, according to the present invention, As shown in Figure 4, it has become extremely easy to attach accurate unit scales to the vertical axis of the surface roughness cross-sectional curve of the measurement results. However, by adding a scale to the platen convexity appearing in the vertical direction of the display screen, a remarkable effect can be obtained in that the surface roughness can be actually measured.

[Brief explanation of drawings]

Fig. 1 is a perspective view schematically showing the general configuration of a scanning electron microscope in the surface roughness measuring device of the present invention, and Fig. 2 is the same (
Figure 4 is a block diagram showing an example of the configuration of the signal processing system, and Figure 4 is a characteristic curve diagram showing an example of the measurement results. Yes. 1, 12.27...Scanning electron microscope 2...Electron gun 3...Focusing coil 4.26.'28...
Deflection coil 5, 14.30... Sample stand 6.7... Adjustment knob 8... Sample stand 9, 11.1
6.32... Standard roughness test piece 10, 15.31...
Sample 13.29...Collector electrode 17.33...
・Amplifier 18.34...Magnification adjuster 19...
Terminal device 20...analog-digital converter 21, 42...
- Cathode ray tube display device 22, 37... Computer 23... Output device 25
, 35...Scanning power supply 36...Integrator 38...
Multiplier 39.40.41...Switch. Patent applicant Tokyo President

Claims (1)

[Scope of Claims] 1. In a scanning electron microscope that measures the cross-sectional shape of the surface of the object to be measured by integrating an image signal from reflected electrons obtained by scanning the surface of the object to be measured with an electron beam, A scanning electronic device characterized by comprising means for calibrating the surface roughness cross-sectional curve of the object to be measured by placing a standard roughness test piece as a reference for the surface roughness cross-sectional curve in the vicinity of the object to be measured. Surface roughness measuring device using a microscope. 2. In the measuring device according to claim 1, the image signal of the object to be measured is integrated by multiplying the ratio of magnifications when observing the standard roughness test piece and the object to be measured, respectively. 1. A surface roughness measuring device using a scanning electron microscope, comprising a digital calculation unit, and configured and arranged so as to obtain a surface roughness cross-sectional curve with a scale of (=l) for the object to be measured.