JPH01175156A - Local surface analyzer - Google Patents

Abstract

PURPOSE:To start an analysis under the proper state by overlappingly displaying the sample image, frame and marker of the sample image information detected by a channeltron and moving a sample as required. CONSTITUTION:An electron beam 2 outputted from an electron beam polariscope is slantly radiated on the surface of a sample 3 on a sample bed 4 and scattered. Electrons scattered from the sample surface are detected by a channeltron 7 provided above the sample 3. The intensity pattern of electrons from the sample surface is displayed as the image of the sample surface on a monitor device based on the information depending on the intensity of detected electrons and the information via the electron beam 2 scanned by the polariscope 9. A sample bed 4 is moved so that the desired analysis surface exists in the possible analysis area by utilizing a frame and a marker overlappingly displayed on the above displayed image. The polariscope 9 changes the radiation position so as to feed the electron beam 2 to the proper position of the sample 3 and fixes the incident position of the electron beam 2 by an electron gun system. The scattered light of the electron beam 2 is fed to an energy analyzer 6 under this condition, thus the proper state to start an analysis is attained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention irradiates a sample with an electron beam for analysis and measures the energy loss spectrum of inelastically scattered electrons scattered from the sample. This invention relates to a local surface analysis device for obtaining local surface structure information of a sample.

[Prior Art] In recent years, the need for surface analysis has increased. The reason for this is that the influence of the surface on the characteristics of electronic devices has increased with the miniaturization of electronic devices, and surface analysis is essential for analyzing the operational characteristics of functional surfaces (e.g., catalysts, gas detection sensors based on surface reactions). The improvement of the surface protective film requires an understanding of the surface characteristics.

Optical microscopes and electron microscopes have traditionally been used to analyze local surfaces, but in recent years, an electron energy loss spectroscopy method has been proposed in which a sample is irradiated with an electron beam and scattered electrons are detected.

The principle of this electron energy loss spectroscopy is based on the 11th
As shown in the figure, an emitted electron beam 2 from an electron gun 1 is incident on the surface of a sample 3, and the electron energy loss spectrum of the inelastically scattered electrons 5 that is inelastically scattered by atoms near the surface of the sample 3 is measured using an energy analyzer 6, etc. Measure using □, sample 3
This is to obtain analytical information on the surface of the surface. In particular, when the electron beam 2 is obliquely incident on the sample surface at a small angle of about 10 degrees, the obtained electron energy loss spectrum will sensitively reflect the structure and state of the sample 3 surface.

However, in such an analyzer, it is necessary to adjust the irradiation point of the electron beam 2 on the sample so that the direction of the inelastically scattered electrons 5 coincides with the axis of incidence of the energy analyzer 6, or so that the direction of the inelastically scattered electrons 5 is incident very close to the axis of incidence.

Furthermore, there is a requirement in terms of analysis operations that the irradiation point of the electron beam 2 must be accurately aligned with the desired analysis position on the sample 3.

Therefore, in a local analysis device using conventional electron energy loss spectroscopy, the incident position of the electron beam on the sample is determined by operating a manipulator while monitoring an enlarged image obtained with an optical microscope, electron microscope, etc. Then, the sample stage was moved and aligned.

[Problems to be solved by the invention] However, since the scale of recent semiconductor microfabrication has reached the submicron order, the above alignment is extremely difficult when performing electron energy loss spectrum analysis using a semiconductor as a sample. Must be adjusted accurately.

In such cases, conventional local analysis devices have the following problems: (1) poor positioning accuracy of the electron beam irradiation point due to movement of the manipulator and sample stage, and (2) poor alignment of the electron beam irradiation point. It is difficult to align the irradiation point,
The problem that it takes a long time is particularly noticeable.

On the other hand, in order to solve the above problem, it is also possible to operate an electron gun or a combination of this and an electron beam deflector (hereinafter collectively referred to as the electron gun system) to align the irradiation point of the electron beam. However, if the irradiation position of the electron beam differs slightly, the efficiency with which the scattered electrons pass through the energy analyzer deteriorates significantly, and there is a problem that the electron energy loss spectrum becomes noisy.

From the above, the present inventor has realized that it is possible to more precisely and easily align the electron beam irradiation point,
Moreover, the present invention was created with the aim of providing a local analysis device that does not deteriorate the detection sensitivity of electron energy loss spectra.

[Means for Solving the Problems] The above object is to provide a local analysis device according to the present invention, that is, a local surface analysis device using electron energy loss spectroscopy, including (a) a movable sample stage on which a sample is placed; (b) An electron gun system in which the incident position of the electron beam on the sample can be adjusted; (c) State I in which the electron beam is scanned within a wide range set for monitoring; and State I in which the electron beam is scanned within a narrow range that can be analyzed. (d) control means for the electron gun system that is capable of switching the electron beam radiation control of the electron gun system between the fixed state (d) and the fixed state; a sample image information detector that detects image information; (e) an image display that displays a sample image based on the image information obtained by the sample image information detector; a monitor device including a frame display means for superimposing and displaying a sample image on a display device, and a marker display means for displaying a marker indicating a desired analysis position superimposed on the sample image within the frame; an electron gun system positioning device that fixes the incident position of the electron beam by the electron gun system at a position on the sample corresponding to the displayed marker position; an analysis means that receives a secondary electron beam and performs an analysis; This problem can be solved by a local surface analysis apparatus characterized in that it is equipped with an analysis control means for causing the incidence of an electron beam for analysis.

In this specification, the term "electron gun system" refers to an electron gun, as described above, or a combination thereof with an electron beam deflector.

In the present invention, a sample image information detector that detects image information from a sample generated as a result of electron beam radiation from an electron gun system refers to, for example, a secondary electron beam generated as a result of electron beam radiation to a sample. Examples include those that detect the sample current and generate image information, those that similarly detect the sample current and generate image information, and those that similarly detect the fluorescence emitted by the sample and generate image information. Can be done.

Furthermore, the frame display means, marker display means, electron gun system positioning means, and analysis control means in the present invention can be constructed using known electronic circuit technology, for example, using a computer, etc. is explained in detail in the examples below. Any known analytical means can be used.

[Function] According to the local analysis device according to the present invention, a typical example of aligning an electron beam with a desired surface position of a sample will be explained. First, for a preliminary operation to perform alignment with high precision, , set the scanning mode of the electron gun system to the above state I so that the electron beam can be scanned within the above wide range, (a) First, set the sample stage at a predetermined height position, and set it at a low magnification. While monitoring the sample image, the sample stage (e.g. , Move the analysis position of the sample to the center of the monitored sample image (hereinafter referred to as the monitor display image); (B) Next, if necessary, in order to increase the magnification of the monitor display image, After repeating the series of operations in step (a) above to bring the desired sample surface into the monitor display image at the desired magnification, a typical operation when using the apparatus of the present invention is, for example, as follows. It can be done by

(a) displaying a frame indicating a narrow area that can be analyzed superimposed on the monitor display image; (d) moving the sample stage so that the surface of the sample desired for analysis is brought inside the frame display; (a) Display a marker indicating the analysis position superimposed within the frame of the monitor display image; (f) Move the marker inside the frame on the monitor display image to place the marker on the surface of the sample where you wish to analyze. (and) and in this state, the radiation control of the electron gun system is switched to the above-mentioned state II. As a result, the position of incidence of the electron beam on the sample by the electron gun system is aligned in accordance with the displayed position of the fixed marker. By sequentially performing the following steps, accurate alignment can be achieved.

[Example] The present invention will be described in detail below based on an example shown in the drawings.

Example 1 The schematic configuration of the electron optical system of the local surface analysis device of Example 1 is shown in FIG. 1.

The electron gun system in this example includes an electron gun 1 and an electron beam deflector 9.
Consisted of. An electron beam 2 emitted from an electron gun 1 is obliquely irradiated onto the surface of a sample 3 placed on a sample stage 4 through an electron beam deflector 9. The energy of the electron beam 2 is usually between 1 eV and several tens of KeV, particularly preferably I
Selected between KeV and 10KeV.

The electron beam deflector 9 is used to scan the electron beam 2 and change the irradiation position. As this electron beam deflector 9, an electrostatic deflector or an electromagnetic deflector can usually be used.

The scattered electron beam 5 scattered on the surface of the sample 3 passes through an energy analyzer 6, is detected by a channeltron 7', and is amplified by an amplifier 8'. This amplified signal is processed by an analysis means (for example a computer) according to known methods. Note that instead of the channeltron 7', a multichannel plate, an electron multiplier tube, or the like may be used as an electron detector. It is also possible to use these detectors in analog mode, amplified with a lock-in amplifier, or in pulse mode, passing the signal through a pulse height discriminator and then counting the pulses. When using the above analog mode, it is necessary to modulate any one of the energy of the electron gun system, the sample potential, the acceleration/deceleration voltage, and the applied voltage of the energy analyzer, or to modulate a plurality of them at the same time.

Although it is possible to use either a thermionic emission type electron gun or a field emission type electron gun as the electron gun 1 of the electron gun system in this example, the energy distribution width is within several eV, and the energy and electron current are An electron gun with stable strength is preferably employed. Note that the electron gun has a built-in electrostatic lens or electromagnetic lens for converging electrons.

The incident electron beam 2 emitted from the electron gun system and incident on the sample 3 is normally made to have a current of between several tens of nanoamperes and several microamperes.

The beam size of the incident electron beam 2 is usually several microns to several hundred microns with an electrostatic lens, but it can be narrowed down to several tens of nanometers by using an electromagnetic lens.

The energy analyzer 6 that receives the scattered electron beam 5 scattered on the surface of the sample 3 may be an electrostatic energy analyzer such as a coaxial double cylinder type or a concentric double hemisphere type, a uniform magnetic field type, an electromagnetic field type energy analyzer, or the like. Although various types can be used, a concentric double hemispherical energy analyzer that is easy to measure angular dependence and has good convergence is particularly preferably employed. Note that an electrostatic lens (not shown) for focusing, accelerating, and decelerating electrons is provided on the incident side of the energy analyzer as necessary.

The energy spectrum of scattered electrons includes a plasmon loss spectrum, a core electron excitation spectrum, etc., and by analyzing these spectra using known methods, information about the structure, state, etc. of the sample surface can be obtained.

The above outlines the configuration of the electron beam emission, scattered electron beam generation, energy analyzer, etc. of the local surface analysis device.

Next, an image information detector for displaying images on a monitor device will be explained.

The detector for this purpose in this example is constructed as follows. That is, the reference numeral 7 in FIG. 1 is a channeltron placed above the sample 3, which detects scattered electrons or secondary electrons emitted from the sample surface and measures the intensity of the electrons emitted from the sample surface. used for measurement. Then, based on the information that depends on the intensity of the electrons detected by the channeltron 7 and the information that the incident electron beam 2 by the electron gun system scans the sample in the X-axis and y-axis directions, a predetermined After image processing is performed, the intensity pattern of electrons emitted from the sample surface is displayed as an image of the sample surface on a monitor device as shown in FIG.

For example, a cathode ray tube is generally used as such a monitor device, but other devices such as a liquid crystal display device, a discharge display tube, an EL display device, etc. can be exemplified without being limited thereto. Furthermore, a type of display device that can perform brightness modulation or color display can also be employed in combination with image processing. The image displayed by this monitor device reflects the pattern of the surface properties and conditions of the sample.

While observing the image displayed on the monitor device as described above, move the sample stage, such as an A specific position on the surface of the sample at which analytical measurements are desired can be moved to a position suitable for electron beam emission for analysis by a gun system (in this example, in the vicinity of the monitor display image).

The feature of this example is that the frame 16 shown in FIG. 9 displays the operation of moving a specific position on the sample surface where analysis and measurement is desired, superimposed on the monitor display image, as shown below.
This is done using marker 17.

That is, in this example, a predetermined analyzable area (scattered electrons scattered from the sample surface), which is determined based on the lens magnification, acceleration, deceleration, and the entrance aperture of the energy analyzer 6, is placed in the center of the monitor display image. The region where the efficiency of passing through the energy analyzer is approximately constant) is displayed as a round frame 1B in Fig. 9, and within this range there is a specific location 17' on the sample surface where analytical measurement is desired. It can be operated as follows. Note that frame 1 indicates the analyzable area above.
6 is normally displayed as a different size depending on the magnification of the image displayed on the monitor.

Move the marker inside the frame 16 indicating this analyzable area to specify a specific location on the sample surface that you wish to analyze (for example, in the example of FIG. 9, a location 17' that is part of the circuit pattern 15 of the integrated circuit). Match the marker to. Note that the marker 17 is moved by an external operation means (not shown). Note that the marker 17 may be moved within the entire monitor display image, or may be moved only within the frame 16 described above.

The above operations provide a proper state for starting analysis.

``In this state, an analysis operation according to a known local surface analysis method may be started.

Example 2 In this example, the configuration of which is schematically shown in FIG. 2, image information for obtaining a monitor display image is obtained by detecting the sample current flowing between the sample 3 and the sample stage 4. Although this embodiment differs from the first embodiment in this point, other configurations and operating techniques are the same as in the first embodiment.

In this example, the means for detecting the sample current flowing between the sample 3 and the sample stage 4 for detecting image information consists of a sample current detection conductor 1o and an amplifier 11, and sends the detected signal to the image processing circuit. It looks like this.

Example 3 In this example, the configuration of which is schematically shown in FIG. This embodiment differs from the first embodiment in that the second embodiment is different from the first embodiment, but the other configuration and operation method are the same as the first embodiment.

A photomultiplier tube 12, which is a means for detecting fluorescence emitted by the sample 3 for detecting image information in this example, is connected to an amplifier 13 to send a detection signal to an image processing circuit.

Next, specific controls for displaying the frame 16 and marker 17 superimposed on the monitor display image in order to move a specific position on the sample surface where analysis and measurement are desired, as explained in each of the above embodiments. The circuit configuration and the electron beam emission state of the electron gun system will be explained.

FIG. 4 shows an outline of the configuration of the signal processing and control system that constitutes the local surface analysis device of the present invention. In this figure, 21 indicates the direction of the emitted electron beam of the electron gun system in the This is a scanning signal generator for scanning the electron beam of the electron gun system so as to scan the sample surface in the area corresponding to the monitor display image shown in Fig. 9 in the X-axis direction and the y-axis direction. Deflect within a predetermined angular range.

The X-axis scanning signal and the y-axis scanning signal from the scanning signal generator 21 are respectively input to the electron beam deflector 9 shown in FIGS. 1 to 3 to perform the above-mentioned control.

FIG. 5 is a block diagram showing an example of the configuration of such a scanning signal generator, in which a signal from a clock circuit 211 is passed through a first counter 212 and converted into a digital/analog converter 213. Then, the signal from the first counter 212 is passed through the second counter 215 and converted into digital/analog by the digital/analog converter 216 to output the scanning signal of the y-axis component. Output. This provides a series of x, y scanning control in which scanning is performed in the y-axis direction for every scan of one line in the x-axis direction. By stopping the normal lock circuit 211, scanning can be stopped and the electron gun system can be switched to the above state H. In this example, the switching of the electron gun system to the state TI by stopping the clock circuit 211 is given by an AND signal between an external switch 23 by manual scanning and a coincidence signal generator 28, which will be described later.

The output of the scanning signal generator 21 is transmitted to a monitor device 24,
The signals are also input to a frame pattern generator 25 and a marker pattern generator 26, respectively, and the signals from these frame pattern generators 25 and marker pattern generators 26 are input to the monitor device 24 via a superposition circuit 27, as shown in FIG. The signal from the image information detector described in FIG. 3 is processed by an image processing circuit (not shown) to perform image processing for superimposition with an image pattern obtained, and then displayed on a monitor display image.

FIG. 8 is a block diagram showing an example of the structure of the frame pattern generator 25, and shows a scanning signal Xi.

ys is the center coordinate (Xee
ntar+YC@nt@r), the frame pattern brightness modulation circuit is turned on, and the corresponding point on the monitor device 24 shines brightly. Note that d in the figure indicates the radius of the frame to be displayed, and ε indicates a parameter that determines the thickness of the line.

FIG. 7 shows an example of the configuration of the marker pattern generator 26, and includes the same circuit configuration as FIG. 8. In other words, d' is the radius of the marker frame to be displayed (dad'
), and ε′ indicates a parameter that determines the thickness of the line. The center of the marker is at coordinates (X M, Y M). Here, the center coordinates of the marker (X M, Y M)
is arbitrarily given by a marker position designation circuit 27 operated from the outside.

As mentioned above, the marker pattern generator 26 can be moved arbitrarily on the monitor display screen (inside the frame 16 in this example) by human input to the external marker position designation circuit 27. There is.

Next, a configuration for aligning the incident position of the electron beam by the electron gun system with a specific location on the sample surface corresponding to the location designated by the marker pattern 17 on the monitor display screen will be described.

The configuration for this purpose in this example is based on a signal from the marker position specifying circuit 27 (marker center coordinates (XM).

The scanning signal (X s, Y
s), and when these coordinate signals (signals (XM,, YM) from the marker position specifying circuit 27 and scanning signals (X s, Y s) from the scanning signal generator 21) match, two The coincidence signal generator 28 outputs a coincidence signal to the AND circuit 29, and the switch 23 changes to state I! When in the switching mode, the clock circuit of the scanning signal generator 21 is stopped to stop (fix) the scanning of the electron gun system.

FIG. 10 is a flowchart showing the above-mentioned operating procedure, which allows the local surface analysis device of this example to efficiently perform surface analysis.

[Effects of the Invention] According to the local surface analysis device according to the present invention, the sample image, frame, and marker obtained by the sample image information detector are superimposed and displayed on the monitor device, and the sample is moved as necessary. By performing this operation and manually operating the marker from the outside, it is possible to select a location on the sample surface where analysis is desired, and to fix the incidence of the electron beam from the electron gun system at this selected location. (1) It becomes possible to easily align the electron beam irradiation point with the incident axis of the energy analyzer.

(2) Furthermore, it becomes possible to align the electron beam irradiation point with the desired analysis location with submicron positioning accuracy.

(3) Furthermore, it becomes possible to perform electron energy loss spectrum analysis on any part of the sample in a constant and favorable state.

This effect can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic diagram showing an embodiment of the electron optical system of the local surface analysis device according to the present invention, and FIG. 2 is a schematic diagram showing an example of the electron optical system of the local surface analysis device according to the present invention. FIG. 3 is a schematic diagram showing another embodiment of the electron optical system of the local surface analysis device according to the present invention; FIG. 4 is a schematic diagram showing another example of the electron optical system of the local surface analysis device according to the present invention. A schematic diagram showing the processing and control system; FIG. 5 is a diagram showing an example of the electron beam scanning signal generator of the local surface analysis device according to the present invention; FIG. 6 is a diagram showing the coincidence signal of the local surface analysis device according to the present invention. FIG. 7 is a diagram showing an example of a marker pattern generator of a local surface analysis device according to the present invention; FIG. 8 is an example of a frame pattern generator of a local surface analysis device according to the present invention. FIG. 9 is a diagram showing an example of an image displayed on the monitor device of the local surface analysis device according to the present invention, and FIG. 10 is a procedure for a local analysis method using the local surface analysis device according to the present invention. FIG. 11 is a schematic diagram showing an embodiment of an electron optical system of a conventional local surface analysis device. 1... Electron gun 2... Incident electron beam 3...
Sample 4...Sample stage 5...Scattered electron beam
6...Energy analyzer 7.7'...Channeltron 8.8', 11.13...Amplifier 9...Electron beam deflector lO...Sample current detection lead wire 12...Photoelectron Amplification tube 14...Secondary electron beam image 1
5... Fine wiring of semiconductor circuit 16... Frame 17... Marker Figure 1 Figure 2 Figure 6 [hi8' Figure 9

Claims (1)

[Scope of Claims] A local surface analysis device using electron energy loss spectroscopy includes (a) a movable sample stage on which a sample is placed, and (b) an electron gun system in which the incident position of the electron beam on the sample can be adjusted. (c) Electron beam radiation control of the electron gun system between state I, in which the electron beam is scanned within a wide range set for monitoring, and state II, in which the electron beam is fixed within a narrow range that can be analyzed. (d) a sample image information detector that detects image information signals of the sample generated with the electron beam radiation of the electron gun system; and (e) An image display that displays a sample image based on image information obtained by an image information detector, a frame display means that displays the analyzable narrow range limit as a frame superimposed on the sample image of the image display, as desired. a monitor device including a marker display means for superimposing and displaying a marker indicating the analysis position on the sample image within the frame; (f) at a position on the sample corresponding to the displayed marker;
an electron gun system positioning device that fixes the incident position of the electron beam from the electron gun system; (g) an analysis means that receives and analyzes a secondary electron beam obtained as a result of electron beam emission from the electron gun system; and (h) analysis control that causes the electron beam to be incident for analysis after fixing the electron gun system so that the electron beam is incident at a position corresponding to the marker displayed on the sample image. A local surface analysis device comprising: means.