JPS6331721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a surface profile measurement device that detects and measures the roughness of an object's surface, and in particular, a scanning electron microscope that can be used to measure surface roughness with extremely high precision without touching the surface of an object. The present invention relates to a surface shape measuring device using a scanning electron microscope that is capable of detecting and displaying information.

Conventional devices for detecting and measuring surface shape and roughness include stylus type and optical type.
The former method detects surface roughness by mechanically moving an extremely fine stylus, so the detection accuracy is high but the speed is slow, and there are also disadvantages such as damaging the object surface. Although this method can detect surface roughness in a non-contact manner and can increase the detection speed, it has the disadvantage that it cannot achieve the same detection accuracy as the stylus type. In particular, in recent years, the latter optical type has been able to take advantage of its advantages and be combined with electronic computers to enable high-speed and two-dimensional measurement of surface roughness. Because there is an inherent limit to measurement accuracy due to the performance of the optical system based on the wavelength, it is difficult to say that it is suitable for use in evaluating the surface roughness of products manufactured by high-precision machining, which has become popular in recent years. There was a problem.

As an alternative to the above-mentioned stylus type, ie mechanical type, and optical type surface profile measuring devices, an electronic type, ie, one using an electron microscope can be considered. However, since electron microscopes utilize the electromagnetic properties of electron beams to observe the minute structures on the surfaces of objects, they can easily detect surface roughness with high precision. However, in conventional electron microscopes, the surface of an object is generally measured by the impact of electron beam irradiation in order to be able to observe the three-dimensional microstructure of the object with high precision and sensitivity. Since secondary electrons emitted from the layer are captured to form electrical signals corresponding to the surface structure, such secondary electron signals can be used to qualitatively observe the structure of the object surface in correspondence with surface roughness. However, it is not possible to faithfully display the cross-sectional shape of the object surface in the same way as the cross-sectional curve of the object surface is drawn in the optical cutting method, which corresponds to the above-mentioned optical surface shape measuring device. Therefore, in order to detect the cross-sectional shape of an object's surface using a conventional electron microscope, it is necessary to go beyond the viewpoint of surface roughness and rely on the image of the object's surface structure itself displayed by the above-mentioned secondary electron signal. It is necessary to perform extremely complex signal processing to construct a three-dimensional image of the surface of an object and read the cross-sectional shape of the surface from the three-dimensional image, and it is necessary to use an electronic equipment system with a complex configuration to perform such signal processing. Therefore, it was not suitable for practical use in evaluating the surface roughness of products subjected to high-precision machining as described above.

The present inventor has proposed a surface profile measuring device using an electron microscope for practical use as an electronic type that eliminates these drawbacks, in place of the stylus type and optical type, which each have their own inherent drawbacks as described above. Various considerations were made regarding this. As a result, the operating conditions of a scanning electron microscope are significantly different from those of conventional scanning electron microscopes. In contrast, for example, the threshold level for electron capture and amplification can be significantly different to capture and amplify mainly reflected electrons from the object surface to generate image signals. If formed, a signal waveform having a unique relationship with the cross-sectional shape of the object surface can be obtained, as will be described later with reference to the drawings, and it can be easily obtained by performing extremely simple arithmetic processing on the backscattered electron signal having such a signal waveform. It was discovered that surface roughness can be detected, and the present invention was developed based on this completely new knowledge regarding the operation of a scanning electron microscope.

The purpose of the present invention is to solve the above-mentioned conventional problems and eliminate their drawbacks, and to solve the conventional problems by performing complex arithmetic processing on the secondary electron signals of an electron microscope, and yet with regard to surface roughness, the surface roughness is only qualitative or average. Whereas only detection results could be obtained, we developed a surface profile measurement device using a scanning electron microscope that can directly detect surface roughness based on the cross-sectional shape of an object surface by simply performing extremely simple arithmetic processing on the backscattered electron signal. It is about providing.

Another object of the present invention is to put surface roughness detection using a scanning electron microscope into practical use, so that it is easier to change and increase the magnification compared to an optical type, and it is possible to detect fine details on the surface of an object corresponding to an enlarged field of view. An object of the present invention is to provide a surface shape measuring device using a scanning electron microscope that can detect a cross-sectional shape.

Still another object of the present invention is to measure the surface roughness of high-precision machined products non-contact, with high precision, and at high speed, which is difficult to do with optical methods.
It is an object of the present invention to provide a surface shape measuring device using a scanning electron microscope that can indicate or record this as a cross-sectional waveform and is particularly applicable to observing and measuring the cross-sectional shape of the surface of a semiconductor element.

The present invention applies relatively simple arithmetic processing to an image signal generated by reflected electrons from a sample surface in a scanning electron microscope to form a signal waveform representing the cross-sectional shape of the sample surface corresponding to one scanning line. This signal waveform for each horizontal scanning line is stacked in the vertical scanning direction so that the three-dimensional shape of the object surface can be displayed like a stereoscopic perspective image, and an electron beam is used to display the surface roughness of the object surface. To provide a completely new surface profile measuring device that is unprecedented in that it can display cross-sectional shapes and that surface roughness can be observed in correspondence with normal microscope images obtained by changing the operating conditions of an electron microscope. Furthermore, the data of the detection results of the cross-sectional shape of the object surface obtained as described above is supplied to an electronic computer and subjected to appropriate arithmetic processing, thereby making it possible to perform a wide variety of analyzes on the three-dimensional shape of the object surface. This is how it was done.

That is, the surface shape measuring device of the present invention obtains a waveform signal representing the cross-sectional shape of the object surface from an image signal formed by backscattered electrons obtained by scanning the surface of the object with an electron beam of a scanning electron microscope. In a surface profile measuring device that extracts and displays or records, a single detection means whose detection sensitivity is set so as to exclude secondary electrons from among the backscattered electrons and detect reflected electrons, and a selection by the detection means. and an integrating means for integrating an image signal formed by the reflected electrons that are detected, and an integrated output signal of the integrating means is a waveform signal representing the cross-sectional shape.

The invention will be explained in detail below by way of example embodiments with reference to the drawings.

First, the basic concept of the present invention will be explained with reference to FIG. 1, which shows a schematic configuration of a surface profile measuring device according to the present invention. In the illustrated schematic configuration, a sample 5 placed on a sample stage 4 is irradiated with a scanning electron beam 3 emitted from an electron gun 1 provided in a vacuum sample chamber A of an electron microscope and focused and deflected by an electric field 2. Then, the surface of the sample 5 is scanned by repeatedly performing line scanning in the X direction while sequentially shifting the position in the Y direction. Electrons obtained from the sample 5 by the irradiation with the scanning electron beam 3 are captured by a collector 6 consisting of a photoelectric conversion and amplification element to generate an image signal of the surface of the sample 5 having a signal waveform corresponding to surface scanning consisting of sequential line scanning. However, if the threshold level of the photoelectric conversion amplifier by the collector 6 is appropriately set, it is possible to capture mainly reflected electrons among the electrons obtained from the surface of the sample 5 in response to the irradiation with the scanning electron beam 3. Can be done. Therefore, since the reflected electrons are simply reflected electrons in the electron beam 3 that irradiated the surface of the sample 5, the output voltage of the collector 6, which is proportional to the amount of electrons obtained from the sample 5, is based on the reflected electrons. is approximately proportional to the angle of inclination of the surface of the sample 5 with respect to the electron beam 3, as shown in FIG. 2a. Therefore, as schematically shown in FIG. 1, for example, if the surface of the sample 5 consists of a series of triangles in the In response, the collector output voltage increases rapidly, and then reaches the apex of the triangle while keeping the high output voltage level constant.The collector output voltage then decreases rapidly in response to the sudden change in the surface tilt angle from positive to negative, and from then on, the collector output voltage decreases rapidly. The triangular valley is reached again while keeping the output voltage level constant. Therefore, the output voltage waveform of the collector 6 obtained for the triangular surface of the sample 5 is
A square waveform is obtained by integrating a triangular cross-sectional shape in a plane including the electron beam 3. Conventionally,
As mentioned above, when observing the surface layer of a sample using an electron microscope, the three-dimensional structure of the sample surface layer can be observed with high precision.
In order to enable observation with high sensitivity, the threshold level for photoelectric conversion amplification in the collector 6 was set so that the collector 6 could capture secondary electrons emitted from within the surface layer of the sample. However, as shown in FIG. 2b, the output voltage of the collector 6 due to the secondary electrons rapidly increases in a substantially quadratic curve with respect to the angle of inclination of the surface of the sample 5 with respect to the electron beam 3. Therefore, the output voltage waveform of the collector 6 due to the secondary electrons from the surface of the sample 5 is:
It is extremely difficult to estimate the cross-sectional shape of the sample surface at first glance depending on the collector output voltage waveform due to secondary electrons, as the waveform is complex and has a complicated relationship with the cross-sectional shape of the sample surface. and
The cross-sectional shape of the sample surface cannot be detected without extremely complicated arithmetic processing.

The present invention is based on the above-mentioned knowledge regarding the collector output voltage waveform due to the reflected electrons and secondary electrons from the sample surface due to electron beam irradiation, and the cross-sectional shape of the sample surface can be determined by integrating the collector output voltage waveform due to the reflected electrons. This is based on a new idea that allows for easy and accurate understanding. Therefore, in the surface profile measuring device of the present invention,
Basically, the cross-sectional shape of the object surface within the plane containing the scanning electron beam is detected by simply integrating the output voltage waveform of the collector that captures the reflected electrons from the object surface due to irradiation with the scanning electron beam. However, there is an advantage that the shape of the object surface can be displayed by simply displaying the integrated output waveform corresponding to the detected cross-sectional shape on the display device. The advantages of the present invention are not limited to this, but the present invention skillfully corresponds to the electron beam scanning of a scanning electron microscope to display the roughness of an object's surface so that it can be grasped at a glance. A significant advantage is that stereoscopic observation or stereoscopic display or recording is possible.

That is, in the schematic configuration of the apparatus of the present invention shown in FIG. The output voltage signal is guided to the processing circuit 8 in the analog processing unit B, and is subjected to at least integral calculation processing to restore the signal waveform to the cross-sectional shape of the sample surface, and if necessary, further removes high frequency components, etc. Cathode ray It is supplied to the tube controller 7 and added to the vertical deflection waveform, and by applying the output voltage signal of the collector 6, it is superimposed on the sample surface observation image displayed on the cathode ray tube display screen to generate a scanning line corresponding to a desired position on the sample surface. The cross-sectional shape waveform is displayed on the display screen of the cathode ray tube. Therefore, in practical terms, it is more suitable to digitize the collector output voltage signal and perform digital operation processing than to perform analog calculation processing on the collector output voltage signal as described above. , the digital arithmetic processing device C performs such digital arithmetic processing. That is, the collector output image signal from the cathode ray tube controller 7 is supplied to the A-D converter 11 and the sync signal generator 12, and the sync signal generator 12 generates a sync signal based on the sync signal extracted from the collector output image signal. A digital image signal formed by driving the A-D converter 11 with the clock pulse generated by the clock is supplied to the interface 13 along with a clock pulse from the synchronizing signal generator 12, thereby forming a digital image signal containing clock information and performing digital arithmetic processing. supplying the circuit 14;
The processing circuit 8 in the analog arithmetic processing device B performs the same digital arithmetic processing as described above on the input digital image signal. The digital arithmetic processing output waveform signal is taken out via the interface 15, restored to an analog waveform signal by the DA converter 16, and displayed on the cathode ray tube display device 9 in the same manner as described above for the analog arithmetic processing device B. At the same time, the signal extracted via the interface 15 is supplied to the digital Each scanning line of one frame is recorded continuously.

Note that the display of the cross-sectional shape signal waveform of the sample surface through such arithmetic processing is basically performed for one scanning line in the X direction, but if such waveform display is repeated in the Y direction for successive scanning lines, The display screen of the cathode ray tube is similar to the conventional secondary electron image signal of an electron microscope, but also displays a three-dimensional image that faithfully represents the shape of the sample surface.
That is, a three-dimensional surface image is displayed instead of a surface image in the form of a shaded planar photograph that has been conventionally observed using an electron microscope.

On the cathode ray tube display screen in the apparatus of the present invention, the first
FIG. 3a shows the cross-sectional shape waveform superimposed on the surface image in the manner described above for a sample having a relatively simple and uniform surface shape with a series of triangular shapes as schematically shown in the figure, and the surface image signal waveform X
- Figure 3b is plotted using Y plotter.
Furthermore, FIG. 3c shows a plot of the cross-sectional shape signal waveform superimposed on the surface image using an XY plotter. Those Figure 3 a~
If we compare the signal waveforms of c, especially b and c, with the sample surface shape shown in Fig. 1, we can see that the cross-sectional shape signal waveform of Fig. 3c obtained by the present invention almost faithfully restores the sample surface shape. , the surface image signal waveform in FIG. 3b has a macroscopic tendency to be a rectangular wave with respect to the triangular shape of the sample surface, and therefore, as described above, the waveform is obtained by differentiating the sample surface shape. It is clearly seen that this is the case.

One of the features of an electron microscope is that the magnification of the observed image can be changed much more easily and in a variety of ways than an optical microscope, and the one shown in Figure 3a has a magnification of 350. On the other hand, Figure 4a shows the cross-sectional waveform superimposed on the cathode ray tube display image when only the central part including the diagonal scratches is enlarged and displayed at a magnification of 3500, and the surface image signal in that display image is shown. Figure 4b shows the waveform plotted with an X-Y plotter, and the cross-sectional shape signal waveform obtained by integrating the surface image signal waveform is shown in the X-Y plotter.
Figure 4c shows what was plotted using the Y plotter. Although the cross-sectional shape signal waveform shown in Fig. 4c clearly represents the enlarged triangular shape of the sample surface, the original cross-sectional shape is distorted due to the direct current component generated in the process of backscattered electron image formation and arithmetic processing. There is a noticeable slope that is not present in the original. Therefore, in a preferred configuration of the device of the present invention, as will be described later, the DC component is corrected and averaged, and the signal waveform is displayed with the undesired slope due to the DC component distortion corrected and removed. The gain can be increased and the displayed image can be sufficiently enlarged in the vertical direction as shown in FIG. 4d. Figure 4(d) faithfully and accurately displays the fine lines that exist in the middle of the slope on the sample surface and indicate detailed surface roughness, and shows the square waveform surface image signal waveform shown in Figure 4(b). It can respond well to minute level fluctuations in flat areas.

The above-mentioned display mode of the surface shape in the surface profile measuring device of the present invention is a continuous square wave-like surface image as schematically shown in FIG. 5a obtained for the continuous trivalent sample surface shown in FIG. The cross-sectional shape signal waveform for one scanning line displaying the surface image signal waveform is superimposed and displayed as schematically shown in FIG. 5b. In order to clearly indicate the position in the image, that is, the part where the cross-sectional shape is displayed in the surface image, as a form of display in the device of the present invention,
As shown in FIG. 5c, markers may be displayed at both ends of the corresponding scanning line position. Further, for each successive scanning line in the vertical direction of the cathode ray tube display screen, a cross-sectional shape signal waveform similar to that shown in FIG.
Once everything has been memorized in the X-Y plotter 1,
0, by sequentially shifting the positions in the vertical direction and plotting as schematically shown in Figure 5d, a three-dimensional image that faithfully corresponds to the surface shape of the sample 5 can be displayed in perspective. . FIG. 6 shows an example of such a three-dimensional image of a continuous triangular sample surface as shown in FIG. 1.

As described above, digitally processing the collector output voltage signal of the electron microscope in the surface profile measuring apparatus of the present invention requires time to take in the detected data into the digital processing circuit 14 and perform the processing. However, on the other hand, it is necessary to take into account the inclination of the sample surface to be observed and the nonlinear distortion of the collector output voltage signal waveform due to the secondary electrons mixed in with the backscattered electrons. It is easy to perform the required integration on the collector output voltage signal waveform after making appropriate corrections in consideration of differences in electron beam reflectivity due to differences in materials and, therefore, differences in collector output voltage. In addition, it becomes easier to perform various analyzes on the three-dimensional images mentioned above, etc.
Digital arithmetic processing has special advantages not available with analog arithmetic processing.

On the other hand, analog arithmetic processing of the collector output voltage signal of an electron microscope is inferior in terms of the wide variety of information processing and analysis that is possible with digital arithmetic processing. There is an advantage that a three-dimensional image that corresponds to the microscope image and more faithfully represents the sample surface shape can be displayed immediately.

In the schematic configuration of the surface profile measuring apparatus of the present invention shown in FIG.
horizontally moved in the X direction and Y direction by a step motor etc. driven according to the control signal from 4.
Alternatively, it is configured to be able to rotate around the horizontal rotation axis ψ or the vertical rotation axis ψ. Therefore, for example, for a flat sample, by moving it in the horizontal direction, the surface image signal waveform and cross-sectional shape signal waveform of the part irradiated with the scanning electron beam 3 can be continuously displayed over the entire surface of the sample. do. For rotating samples, a specific scanning line is set along the generatrix of the rotating cylindrical surface.
By rotating the sample by setting the rotation axis in a vertical plane that includes the specific scanning line position, the surface roughness, that is, the cross-sectional shape of the rotating cylindrical surface of the rotating sample can be detected in the generatrix direction of the rotating cylindrical surface. This is repeated at regular intervals along the circumferential direction of the sample, so that a three-dimensional image of the surface of the rotating sample can be displayed in the same way as for a flat sample. Furthermore, if desired, the sample surface image that superimposes and displays the cross-sectional shape signal waveform of the sample surface can be changed to a conventional surface image based on secondary electrons instead of the surface image based on the above-mentioned backscattered electrons. By appropriately switching the threshold level of the photoelectric conversion amplification in , a superimposed display similar to that shown in FIG. 5b is performed.

An example of the detailed configuration of the surface profile measuring apparatus of the present invention having the above-mentioned general configuration will be described in detail below in comparison with the detailed configuration of this type of apparatus that has been attempted in the past.

First, FIG. 7 shows the detailed configuration of a device of this type that has been attempted to detect surface roughness using a scanning electron microscope. In the illustrated configuration, an acceleration power source 23 is connected to the electron gun 22 of the electron microscope 21.
The electron beam is emitted at high speed by applying an ultra-high voltage from the lens power supply 2 to the focusing coils 24 and 25.
6 to focus the target at the position of the target 30, and the scanning power supply 2 to the X-direction deflection coil 27 and the Y-direction deflection coil 28.
Deflection voltages from 9 are respectively supplied to scan the surface of the target 30 in the XY direction. Electrons emitted from the target 30 by the surface scanning are captured by a collector 31 consisting of a photoelectric conversion and amplification element, for example, a photomultiplier, subjected to photoelectric conversion and amplification, and the output voltage signal is sent to the cathode ray tube via a signal amplifier 32. 33 electron beam intensity control electrode 34 is applied. At the same time, the output voltage signal is also supplied to the adder 36 via the switch 35, and the vertical Add to deflection voltage. Therefore, for example, when a target surface having a continuous triangular surface shape as shown in FIG. Similarly, the surface image signal waveform corresponding to the desired scanning line is displayed superimposed on the surface image of the target 30. However, as mentioned above,
Conventionally, secondary electrons emitted from the target 30 were captured, so nonlinear distortion occurred based on the collector output voltage characteristics as shown in FIG. 2b, and the faithful cross-sectional shape of the target surface was As mentioned above, unless you go through the complicated arithmetic processing process,
I just couldn't get it.

FIG. 8 shows an example of the detailed configuration of the surface profile measuring apparatus of the present invention, which eliminates the drawbacks of the conventional apparatus as described above. The illustrated configuration is similar to the conventional device shown in FIG. 7 with respect to the basic configuration and operation essential for a surface profile measuring device constructed using a scanning electron microscope. Therefore, in the device of the present invention shown in FIG. 8, the same components as in the conventional device shown in FIG. The same applies to other configuration examples described later with reference to FIG. Furthermore, although the detailed configurations shown in FIGS. 8 and 10 do not necessarily correspond clearly to the schematic configuration shown in FIG. 1, they are exactly the same in terms of technical ideas regarding the configuration and operation and effects, as described below. It is.

Therefore, in the configuration example of the surface profile measuring apparatus of the present invention shown in FIG. 8, in the same manner as described above with reference to FIG. The electron beam is passed through a collector 31 consisting of a photomultiplier or a scintillation counter.
The output voltage signal is captured and photoelectrically converted and amplified by a signal amplifier 32, and then supplied to an electron beam intensity control electrode 34 of a cathode ray tube 33 to display a surface image of the target 30. do. At the same time, the output voltage signal is guided to the adder 36 via the switch 35, superimposed on the vertical deflection voltage of the cathode ray tube 33, and the signal waveform related to the output voltage signal is arbitrarily changed by closing the switch 35. The selected scanning line is displayed superimposed on the target surface image on the display surface of the cathode ray tube 33, as described above with reference to FIG. However, in the device of the present invention,
The output voltage signal of the signal amplifier 32 is supplied to a low-frequency/high-frequency blocking filter 41 to remove low-frequency distortion components and high-frequency noise components. As described in detail regarding the schematic configuration, the surface image signal waveform is subjected to integral processing to form an integrated output voltage signal with a waveform representing the cross-sectional shape of the target surface, and the DC voltage from the DC component correction circuit 43 is superimposed to display the signal on the screen. An adder 36 is supplied with a display position that can be corrected. In the device of the present invention, as described above, the threshold level of the photoelectric conversion amplifier in the collector 31 is appropriately selected so that the reflected electrons from the target 30 can be mainly captured. As mentioned above, a waveform obtained by differentiating the cross-sectional shape of the target surface is obtained, and a waveform obtained by almost faithfully restoring the cross-sectional shape of the target surface is obtained as the integrated output voltage signal of the integrator 42. be. In addition, if calibration is performed by substituting the sample whose surface roughness is to be detected as the target 30 with a standard test piece having an appropriate known surface roughness under the same conditions, the surface roughness of the sample can be calculated numerically. can be detected.

As an example of the operation of the surface profile measuring device of the present invention having such a configuration, the following describes the case where a standard roughness test piece having a surface profile with triangular ridges arranged in parallel as shown in FIG. 1 is used. This will be explained in more detail.

In the configuration of the surface profile measuring apparatus of the present invention shown in FIG. 8, the signal amplifier 32 operates in substantially the same manner as in a normal scanning electron microscope. Therefore, after photographing an image of the sample surface on the display screen of the cathode ray tube 33 that supplies the amplified output voltage signal of the signal amplifier 32 to the control electrode 34, the switch 35 is closed during the desired line scanning period. If double exposure is performed by superimposing the amplified output signal that has been integrated on the vertical deflection voltage, the backscattered electron image will show a surface cross section at the desired scanning line position, as schematically shown in Figure 5a. A rectangular waveform is recorded in a superimposed manner.

In FIGS. 9a to 9f showing signal waveforms of each part of the device of the present invention having the above-described configuration, FIG.
and b are horizontal and vertical deflection signal waveforms, respectively, common to the scanning electron microscope 21 and the cathode ray tube 33; High-frequency rejection filter 41, integrator 4
The output voltage signal waveforms of the integrator 42 in the case where the DC component correction circuit 43 is not used are shown in FIG. 9f.

Therefore, as shown in FIG. 9c, the amplified output voltage signal waveform of the signal amplifier 32 has a surface scan synchronized with its surface scan, as a characteristic unique to the electron beam focusing and deflecting system of the electron microscope 21. cathode ray tube 3
Corresponding to the fact that the center of the display image 3 becomes brighter than the periphery, the long wavelength component that pushes up the center of the signal waveform during the line scanning period and the extreme Waveform distortion and noise consisting of short wavelength components are often superimposed. However, such waveform distortion and noise can be sufficiently removed by passing the amplified output voltage signal through the low-frequency and high-frequency blocking filters 41, as shown in FIG. 9d. Furthermore, as is clear from a comparison between d and e in FIG. 9, the output voltage signal waveform of the integrator 42 is obtained by integrating the filtered output voltage signal waveform of the filter 41, and approximately corresponds to the cross-sectional shape of the sample surface. It will be faithfully represented.
It goes without saying that such a mutual relationship between the signal waveforms is due to the correlation characteristic between the tilt angle of the sample surface in the backscattered electron image and the collector output voltage as described above with reference to FIG. 2a.

Furthermore, if the DC component correction voltage from the DC component correction circuit 43 is not supplied to the integrator 42, the DC component distortion of the collector output voltage signal will cause the signal waveform to become unreasonable, as shown in FIG. May be tilted. Therefore, especially when the time axis of the surface image signal waveform is expanded to observe only the oblique portion of the surface shape, as shown in Fig. 4c, the DC component correction voltage must be added. By correcting the undesired inclination caused by the DC component distortion of the signal waveform, the net sample surface cross-sectional shape signal waveform is sufficiently amplified and enlarged, and the sample surface cross-section is corrected as shown in Figure 4d. Detects and displays minute shapes in detail.

Furthermore, if the adder 36 adds the above-mentioned sample surface cross-section signal waveform to the vertical deflection signal waveform of the cathode ray tube 33 and performs the above-mentioned double exposure, the third
A display image as shown in FIG. Note that the displayed image shown in FIG. 3a or FIG. 4a is a backscattered electron image superimposed with only the sample surface cross-sectional shape signal waveform corresponding to a single scanning line.
If all cross-sectional shape signal waveforms corresponding to each scanning line in surface scanning are drawn, a three-dimensional shape equivalent to the three-dimensional shape shown in Figure 6, in which the three-dimensional shape of the sample surface is laid out on a plane, can be drawn. As mentioned above, it is possible to display a surface image that is faithful to the shape of the sample surface.

Therefore, when displaying a cross-sectional shape signal waveform corresponding to a single scanning line by superimposing it on a backscattered electron image as shown in FIG. 3a or 4a, The corresponding location on the backscattered electron image on which the cross-sectional shape signal waveform is displayed superimposed can be clearly indicated by increasing the brightness of the electron image. As shown in FIG. 5c, an example of the configuration of the surface profile measuring device of the present invention is shown in FIG. They are shown in m.

Therefore, since the aspect of the superimposed display of the backscattered electron image and the cross-sectional shape signal waveform in the configuration example shown in FIG. 10 is exactly the same as that shown in FIG.
In the following, only the structure and operation of the portion related to the marker display indicating the position of the scanning line on which the cross-sectional shape signal waveform is superimposed and displayed as described above will be described.

In the configuration example of the apparatus of the present invention shown in FIG. 10, the X-direction deflection voltage waveform obtained from the scanning power supply 29 is supplied to the Schmitt trigger circuit 51, and the waveform shown in FIG. A square wave train signal is formed, and the square wave train signal is supplied to a differential shaping circuit 52 for differentiation to form a positive and negative differentiated pulse train signal as shown in FIG. 5e, and further,
The polarity of the differential pulse train signal is inverted and then rectified, as shown in FIG. 11f, which corresponds to the falling position of each square wave in the output square wave train signal of the Schmitt trigger circuit 51 shown in FIG. 5d. Extract a positive pulse train signal like this. A register 5 configured with a down counter receives the positive pulse train signal.
3, the number of pulses in the positive pulse train is sequentially determined for each frame period from the numerical value representing the scanning line signal corresponding to the desired cross-sectional shape signal waveform display position repeatedly designated for each frame period by the scanning line number designation circuit 54. When the result of the subtraction becomes zero, that is, when the scanning line of the designated number mentioned above is reached by counting sequentially from the beginning of each frame, an output signal is supplied to the gate 56. is opened for approximately one period of X-direction deflection.

The scanning line number designation circuit 54 designates, for example, by pressing a button, the number of the scanning line on which the cross-sectional shape signal waveform should be superimposed and displayed in one frame of the screen. It generates a number of pulses corresponding to a designated number in synchronization with a deflection voltage signal.

Therefore, the gate 56 has a time setting circuit 55.
A square wave signal having a high level is constantly supplied between the marker display positions at both ends of the scanning line set by A square wave signal is applied to the gate 5 as shown in FIG. 11g.
As the gate output signal of 6, the switch 35 and the switch 57 are closed. Therefore, by closing the switch 35, the cross-sectional shape signal waveform of the sample surface is displayed in a superimposed manner only during the period between the marker positions at both ends of the scanning line with the designated number, and the switch 57 is closed. Similarly, the sawtooth waveform voltage for X-direction deflection shown in FIG. Therefore, a single sawtooth waveform voltage as shown in FIG. 11h is applied to the Schmitt trigger circuit 58. Although only a single Schmitt trigger circuit 58 and a single differential shaping circuit 59 are shown in FIG. 10, they are actually used as marker generation circuits for the start and end of a specified scanning line. It is assumed that the respective cascade connections of two Schmitt trigger circuits 58 and 58' and differential shaping circuits 59 and 59' are connected in parallel. Therefore, for generating a starting edge marker, the square wave signal from the Schmitt trigger circuit 58 shown in FIG. As shown in Figure 11j, a marker pulse signal corresponding to the rising edge of the input square wave signal is formed, and for generating a termination marker, a Schmitt pulse signal is generated in exactly the same manner as described above.
The trigger circuit 58' and the differential shaping circuit 59' form a marker pulse signal as shown in FIG. 11L, which corresponds to the rise of the square wave signal shown in FIG. 11K. If the start end marker and the end marker of the specified number scanning line are led to the adder 60, added to the reflected electron image signal from the signal amplifier 32, and supplied to the electron beam intensity control electrode 34 of the cathode ray tube 33, the result shown in FIG. As schematically shown in FIG. 1, a backscattered electron image display of the superimposed cross-sectional shape signal waveform is performed, with the corresponding scanning line position clearly indicated by a marker.

The details of the surface profile measuring apparatus of the present invention described above are summarized as follows.

(1) Integration, noise removal,
By performing calculation processing such as averaging, a cross-sectional shape signal representing the surface roughness of the sample is easily and accurately formed.

(2) When displaying the results of the above calculation processing on a cathode ray tube display device, increase the brightness of the relevant scanning line or attach a marker to clearly indicate the position of the relevant scanning line on the microscope image.

(3) A surface cross-sectional shape signal waveform is displayed for each successive scanning line in surface scanning of an electron beam in a scanning electron microscope, and a three-dimensional image of the sample surface shape is displayed.

(4) Perform the arithmetic processing on the sample surface image signal described above in an analog or digital manner.

(5) Absolute calibration of the surface roughness is performed by comparing the above-mentioned arithmetic processing display for the surface roughness detection sample and the standard test piece with known surface roughness.

(6) By moving or rotating the support stand installed in the vacuum sample chamber of the scanning electron microscope using a step motor or the like in conjunction with the digital calculation processing process, the display of the cross-sectional shape signal waveform of the sample surface described above can be performed on the sample. Do this continuously over the entire surface.

As is clear from the above description, according to the present invention, the position of the scanning line is confirmed by comparing it with the microscopic image of the sample surface in a scanning electron microscope, and the cross-sectional shape signal waveform representing the surface roughness is faithfully displayed. Furthermore, by continuously displaying the cross-sectional shape signal waveform for each successive scanning line over the entire area of the microscopic image, faithful three-dimensional display of the sample surface shape can be achieved with a simple configuration. This can be easily done by simple arithmetic processing. Therefore, it is not only possible to dramatically improve the function of measuring the surface shape of an object using a scanning electron microscope and greatly increase it compared to the conventional method, but also to evaluate the characteristics of machined surfaces by cutting, polishing, ultra-precision machining, etc. It is easy to perform and can improve the quality, making it an extremely important contribution to the advancement of machining technology. At the same time, as shown in FIG. 12a showing the surface image signal waveform, and as shown in FIG. It can also be applied to precise inspection of structures, and can also be used to inspect lubricated surfaces,
Applications can be considered not only to all kinds of engineering problems that require the observation of the shape of various surfaces such as corroded surfaces, but also to fields such as medicine and biology. It seems that this could have an impact on the field.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the schematic configuration of the surface profile measuring device of the present invention, and Figures 2a and 2b show the relationship between the inclination of the sample metal surface and the collector output voltage in a scanning electron microscope for reflected electrons and secondary electrons. FIGS. 3a, b, and c are oscilloscope waveform diagrams showing examples of surface metal surface images and image signal waveforms displayed by the apparatus of the present invention, and FIGS. 4a, b, c, and d are characteristic curve diagrams respectively showing Figure 3a
Figures 5a to 5d are oscilloscope waveform diagrams each showing an enlarged view of a part of .
The figure is an electron micrograph showing an example of a sample metal surface image displayed in the manner shown in FIG. 5d, FIG. The figure is a block diagram showing an example of the detailed configuration of a surface profile measuring device using a scanning electron microscope according to the present invention, and FIGS.
0 is a block diagram showing another example of the detailed configuration, FIGS. 11 a to m are waveform diagrams showing signal waveforms of each part, and FIGS. 12 a and b,
c is an electron micrograph diagram and a waveform diagram showing another example of a surface metal surface image and an image signal waveform displayed by the apparatus of the present invention, respectively. A...Scanning electron microscope unit, B...Analog calculation processing unit, C...Digital calculation processing unit, 1...
Electron gun, 2... Electric field, 3... Electron beam, 4...
Sample stage, 5... Sample, 6... Collector, 7... Cathode ray tube controller, 8... Analog signal generation circuit, 9... Cathode ray tube, 10... X-Y plotter,
11...A-D converter, 12...Synchronization signal generator, 13, 15...Interface, 14...
Arithmetic processing circuit, 16...D-A converter, 21...
Scanning electron microscope, 22... Electron gun, 23...
Acceleration power source, 24, 25... Focusing coil, 26...
Lens power supply, 27, 28...Deflection coil, 29...
... Scanning power supply, 30 ... Target, 31 ... Collector, 32 ... Signal amplifier, 33 ... Cathode ray tube, 34 ... Control electrode, 35 ... Switch, 36
...Adder, 37, 38...Deflection coil, 41...
...low-pass/high-pass rejection filter, 42...integrator, 4
3...DC component correction circuit, 51, 58, 58'...
Schmitt trigger circuit, 52, 59, 59'...
... Differential shaping circuit, 53 ... Register, 54 ... Scanning line number designation circuit, 55 ... Time setting circuit, 56
...gate, 57...switch, 60...adder.

Claims (1)

[Scope of Claims] 1. A waveform signal representing the cross-sectional shape of the object surface is extracted from an image signal formed by backscattered electrons obtained by scanning the object surface with an electron beam of a scanning electron microscope and displayed. Alternatively, in a surface profile measuring device for recording, a single detection means whose detection sensitivity is set so as to exclude secondary electrons from the backscattered electrons and detect reflected electrons, and selective detection by the detection means. an integrating means for integrating an image signal formed by the reflected electrons, and an integrated output signal of the integrating means is a waveform signal representing the cross-sectional shape. measuring device. 2. The measuring device according to claim 1, wherein the waveform signal representing the three-dimensional shape of the surface is formed by sequentially performing line scanning and surface scanning with the electron beam. A surface profile measurement device using a scanning electron microscope. 3. A scanning type measuring device according to claim 2, characterized in that the intensity of the electron beam with respect to a desired scanning line is increased to clearly indicate the waveform signal at the position of the scanning line. Surface shape measuring device using an electron microscope. 4. A scanning device according to any one of claims 1 to 3, characterized in that the waveform signal is formed by processing the image signal in the form of an analog signal. Surface shape measuring device using a type electron microscope. 5. A scanning device according to any one of claims 1 to 3, characterized in that the waveform signal is formed by processing the image signal in the form of a digital signal. Surface shape measuring device using a type electron microscope. 6. In the measuring device according to any one of claims 1 to 5, the first waveform signal formed by scanning the surface of the object with the electron beam is measured by measuring the standard surface roughness. A second surface formed by scanning the surface of the test piece with the electron beam
A surface profile measuring device using a scanning electron microscope, characterized in that calibration is performed using the waveform signal of the scanning electron microscope. 7. In the measuring device according to any of claims 1 to 6, the electron beam is A surface shape measuring device using a scanning electron microscope, characterized in that the range of the surface of the object scanned to form the waveform signal is expanded along the desired direction. 8 A scanning electron microscope section A equipped with a backscattered electron collector that captures backscattered electrons generated by scanning an object surface with an electron beam and generates an image signal corresponding to the uneven shape of the object surface; It consists of an analog processing unit B that amplifies, filters, and integrates the image signal to analyze the cross section of the object with high precision and displays it on the cathode ray tube as an analog signal that is superimposed with the image signal or separately, and the image signal of the electron microscope is The scanning according to claim 1, characterized in that one specific scanning line or one frame worth of scanning lines is displayed as an integral waveform on a cathode ray tube, either superimposed on the image signal or separately. Display shape measuring device using a type electron microscope. 9 a scanning electron microscope section A equipped with a backscattered electron collector that captures backscattered electrons generated by scanning an object surface with an electron beam and generates an image signal corresponding to the uneven shape of the object surface; an analog arithmetic processing unit B that amplifies, filters, and integrates an image signal to analyze a cross section of an object with high precision and displays it on a cathode ray tube as an analog signal, superimposed with the image signal or separately; and an image from the backscattered electron collector. A signal or an analog signal obtained by integrating the image signal is input, the image signal or the analog signal is converted into a digital signal, and the cross-sectional waveform component of the object surface is extracted by digital arithmetic processing, and the image signal is displayed on the cathode ray tube. 2. A surface profile measuring device using a scanning electron microscope according to claim 1, comprising a digital arithmetic processing unit C that displays the data overlappingly with or separately from the data or records the data continuously on an XY plotter. 10 A scanning electron microscope section A equipped with a backscattered electron collector that captures backscattered electrons generated by scanning an object surface with an electron beam and generates an image signal corresponding to the uneven shape of the object surface; Digital calculation that converts the image signal into a digital signal, extracts the cross-sectional waveform component of the object surface through digital calculation processing, displays it on a cathode ray tube superimposed with the image signal or separately, and continuously records this cross-sectional waveform. A surface shape measuring device using a scanning electron microscope according to claim 1, comprising a processing section C.