JPH05126769A - Method and apparatus for analyzing surface - Google Patents

Abstract

PURPOSE:To make it possible to perform the automatic focusing of a probe beam on the surface of a sample and to make the analysis of the surface of a minute area highly accurate by detecting the fluorescence region on the surface of the sample, and automatically adjusting the arrangement of each element of an optical system so that the size of the fluorescence region becomes the minimum size. CONSTITUTION:The fluorescence, which is formed by the application of a probe beam on the surface of a sample 3, is condensed with an optical element 2, which is similar to a condensing optical element. The beam is taken out of the optical axis of the element 2 with a reflecting mirror 9. The expanded image of a fluorescence generating region is formed on a detector 10. The two-dimensional image signal is converted into the numerical-value data with a signal processing device 11, and the data are sent into a control device 12. The device 12 moves a sample stage 4 so that the fluorescence region becomes the minimum size based on the diameter of the fluorescence region computed by using the data and the position data of the sample 3 inputted from a controller 6 of a sample moving mechanism 5 and optimizes the position of the sample 3. Thus, the converging point of the probe beam can be automatically focused on the surface of the sample, and the surface of the minute area can be readily analyzed highly accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface area analyzer for a microscopic area, and more particularly to a surface area analysis apparatus capable of automatically focusing the light in the vacuum ultraviolet to the soft X-ray area onto a sample surface of a focusing optical system. A method and an apparatus thereof.

[0002]

2. Description of the Related Art In recent years, surface analysis techniques for minute areas have become important. For example, in the analysis and identification of residual contaminants on the surface of a semiconductor circuit element, a minute area having a diameter of several μm or less is the analysis target. Further, in the analysis of chemical reaction such as thin film formation on the surface and catalytic reaction, the area of 1 μm diameter or less is the analysis target.

In order to meet these requirements, from vacuum ultraviolet to soft X
A method has been proposed in which light in a line region is focused on a minute region on the sample surface and various particles (electrons, photons, ions) emitted from the sample surface are observed.

[0004]

In the prior art, the focus (focusing point) of the focusing optical system for the light from the vacuum ultraviolet to the soft X-ray region, which is the probe beam, is accurately aligned on the sample surface. There was no easy adjustment. The condensing point of the probe beam may deviate from the design value of the condensing optical system due to the deviation from the ideal shape of the optical system, the deviation of the light source position, or the like.
Unless the converging points of the probe beam are accurately aligned with each other on the sample surface, even if the condensing optical system forms a sufficiently thin microbeam, it does not lead to miniaturization of the analysis region.

An object of the present invention is to provide an analyzer for a micro area which can automatically focus a probe beam on a sample surface.

[0006]

In order to achieve the above object, fluorescence emitted from a condensing region on a sample surface is condensed using an optical element, and the size of the fluorescent region is determined by a two-dimensional detector. Observe. It is convenient to use the same optical element as the condensing optical element for this fluorescence observation because the device configuration becomes simple. From this observation, the size of the light collecting area on the sample surface can be obtained. On the other hand, the position and orientation of the sample table, light source or optical element is variable. Based on this observation value, a means for automatically adjusting the arrangement of each element of the optical system is provided so that the size of the fluorescent region is minimized, whereby the focusing optical system is automatically focused.

[0007]

When various kinds of particles (electrons, photons, ions, neutral particles, etc.) are emitted from the sample surface when light in the vacuum ultraviolet region is irradiated from the soft X-rays. By analyzing the types and energies of these particles, it is possible to identify the elemental species and the chemical bond state in the irradiation region. In particular, when the emitted particles are electrons, photoelectron spectroscopy that analyzes the energy of the emitted electrons is
Suitable for identification of chemical bond state.

In order to analyze the surface of a minute region, light in the vacuum ultraviolet region from the soft X-ray is focused on the sample surface, and the kind and energy of particles emitted from the sample surface are observed. Low-aberration optical elements such as various reflecting mirrors and zone plates are used to collect light from the soft X-rays into the vacuum ultraviolet region. Aspherical mirrors such as elliptical mirrors, Walter mirrors, and Kirkpatrick-Bets mirrors are particularly convenient because they have no chromatic aberration. In surface analysis, the wavelength of incident light may be changed in order to change the surface sensitivity of the sample. Further, as will be described later, when the fluorescence emitted from the sample surface is condensed by the same type of optical element, the device configuration becomes simple. The aspherical mirror is characterized in that its light-condensing characteristics do not change with respect to changes in the wavelength of incident light or fluorescence.

In order to carry out the surface analysis of such a minute region with high accuracy, the focus of the condensing optical element for the light from the soft X-ray to the vacuum ultraviolet must be correctly aligned on the sample surface. The method of making the focus on the sample surface will be described below.

When vacuum ultraviolet light is applied to the sample surface from the soft X-rays, light (fluorescence) is generated from the sample surface. The size of this fluorescence generation region is considered to be approximately the same as the diameter of the focused beam of the incident light. Therefore, by measuring the size of this fluorescence generation region, the focused beam of the incident light on the sample surface can be measured. The diameter can be measured. As can be seen by comparing the case where the focus of the focusing optical system is on the sample surface and the case where it is not, the focused beam diameter of the incident light on the sample surface is the smallest when the focus is on the sample surface. Therefore, the position where the focused beam diameter is the minimum is the state where the sample surface has a focus.

A magnifying optical system is used to collect the fluorescence emitted from the sample surface. At this time, if the same optical element as the optical element for condensing incident light is used, the device can be simplified. Fluorescence from the sample surface collected by this condensing optical element is emitted from the photodiode array or CC.
D, detected by a two-dimensionally detectable element represented by a position readout type micro channel plate. Alternatively,
When fluorescence cannot be directly observed using these detection elements, these fluorescences (X-rays) may be applied to the fluorescence plate and the visible light generated from the fluorescence plate may be observed by the detection element. By using such a two-dimensional detector, the intensity distribution of fluorescence in the fluorescence region can be observed at one time. The size of the fluorescent region can be measured by subjecting the signals of the light receiving elements of these two-dimensional detectors to appropriate processing.

Focusing of the optical system on the sample surface is performed by using the information of the size of the fluorescent region measured by the above-mentioned method, the arrangement of the sample stage, the arrangement of the incident light source or the condensing optical system,
And the arrangement of each element of the optical system can be adjusted so that the size of the fluorescence image is minimized.

Such an operation for calculating the size of the fluorescent region from the output of the detector and an operation for adjusting each element of the optical system are automatically performed by using a computer (control device).

[0014]

【Example】

<Embodiment 1> FIG. 1 shows a basic embodiment for automatically focusing an incident light condensing optical system. Light in the vacuum ultraviolet region from the soft X-rays emitted from the light source 1 is condensed on the surface of the sample 3 using the optical element 2. Optical element 2
Is a reflective optical element as described above. Optical element 2
May be composed of a single optical element or may be composed of a plurality of optical elements.

The sample 3 is installed on the sample table 4. The sample table 4 can be moved three-dimensionally by the moving mechanism 5. This minute movement is controlled by the controller 6.

Particles (electrons, photons, ions, neutral particles, etc.) emitted from the surface of the sample 3 by irradiation of the focused beam
Are detected using the analyzer 7. The analyzer 7 is an analyzer having a particle type and particle energy analysis function. Various parameters of the analyzer 7 necessary for analysis are controlled by the controller 8.

Fluorescence that appears when the surface of the sample 3 is irradiated with the probe beam is condensed by the same optical element 2 as the optical element for condensing the probe beam, and is drawn out of the optical axis of the optical element 2 by the reflecting mirror 9. A magnified image of the fluorescence emitting area is created on the detector 10. Although only the case where the reflecting mirror 9 is installed is shown in the drawing, if the detector 10 does not interfere with the incidence of light on the optical element 2, the fluorescence can be directly detected by the detector 10 without installing the reflecting mirror 9. You may receive it. The detector 10 can detect a two-dimensional image of a fluorescence image. The signal about the two-dimensional image of fluorescence obtained by the detector 10 is input to the signal processing device 11 and converted into numerical data to be converted into the control device 1.
Sent to 2. On the other hand, the position data of the sample 3 output from the controller 6 of the sample stage moving mechanism 5 is also controlled by the controller 12.
Entered in.

In the present embodiment, automatic focusing of the optical system is performed as follows, for example. The control device 12 is
The position of the sample table 4 is changed by sending a position control signal to the controller 6. Next, the control device 12 receives the data of the fluorescent image on the surface of the sample 3 at that position from the signal processing device 11, and calculates the diameter of the fluorescent region. The controller 12 also stores the calculated diameter of the fluorescent region and the position of the sample 3. This operation is repeated within the preset range of position coordinate of the sample, and the position of the sample 3 is optimized so that the fluorescence region becomes the smallest. As the position optimization method at this time, various methods other than the method described here can be considered. These other methods can also be performed by using the controller 12 as needed.

In this embodiment, the focal point of the probe beam can be automatically set on the sample surface. As a result,
Surface analysis of a minute area can be performed with high accuracy and easily. <Embodiment 2> The embodiment shown in FIG. 2 is an example in which the arrangement of the optical element 2 can be adjusted by the moving mechanism 14 and the arrangement of the light source 1 can also be adjusted by the moving mechanism 15. The moving mechanism 14 and the moving mechanism 15 are controlled by the controllers 16 and 17, respectively. The data on the positions of the light source 1 and the optical element 2 and the data on the angle with respect to the device reference line are input to the control device 13. As described in the first embodiment, the light source 1, the optical element 2, and the sample stage 4 are adjusted by the control device 13 so that the size of the fluorescence image output from the signal processing device 11 is minimized.

In this embodiment, the focal point of the probe beam can be automatically adjusted on the sample surface. As a result,
Surface analysis of a minute area can be performed with high accuracy and easily. <Embodiment 3> FIG. 3 shows an embodiment in which the probe beam is scanned on the sample surface while performing the automatic focusing as described above. In order to scan the sample surface with the probe beam, the moving mechanism 5 moves the sample 3, or the moving mechanisms 14 and 15 move the optical element 2 and the light source 1. In this way, the particles emitted from the surface of the sample 3 are detected while scanning the sample surface with the probe beam. The position of the sample 3 output from the controller 6 and the signal from the controller 8 are taken into the control processing device 18 and processed. By outputting the processing result to the display device 19, a two-dimensional image of the analysis result of the sample surface can be obtained.

Since automatic focusing is performed simultaneously in this embodiment, the surface of the sample 3 does not need to be a flat surface, and surface analysis can be easily performed on a curved sample or a sample having irregularities.
It is also possible to form an image of the entire sample surface from the fluorescence observation signal output from the signal processing device 11.
The setting of the analysis area on the sample surface can be easily grasped.

<Embodiment 4> This embodiment is an automatic focusing configuration for a multi-stage reduction optical system, which is used to further increase the spatial resolution of surface analysis.

When it is necessary to make a finer light source for performing high-resolution surface analysis, a multi-stage reduction optical system as shown in FIG. 4 may be adopted. Light from the vacuum ultraviolet to the soft X-ray region from the light source 1 is condensed on the aperture 22 using the optical element 20. As a result, a reduced image of the light source 1 is formed on the aperture 22. This reduced image can be further reduced by using the optical element 21, and light can be irradiated to a smaller area.

At this time, the reflecting mirror 9 is placed immediately after the optical element 21 in order to perform automatic focusing by using the fluorescence image emitted from the irradiation region of the incident light. Alternatively, the reflecting mirror 9 may be installed immediately after the optical element 20 in order to obtain a magnified image of higher magnification. The other parts are the same as in the first embodiment. When the optical system of the incident light is composed of a plurality of optical elements as described above, the reflecting mirror 9 or the detector 10 for taking the fluorescence image may be installed at an appropriate position of the optical system. This embodiment also includes combinations with the embodiments of FIGS. 2 to 3.

<Embodiment 5> In the embodiments described so far, a part of the optical element 2 (or the optical element 21) for converging the incident light is installed in order to install the reflecting mirror (or the detector) for obtaining the fluorescence image. It was only used. Therefore, by utilizing the fact that the wavelength of incident light is shorter than the wavelength of fluorescence, a reflecting mirror (for example, a multilayer film reflecting mirror) that transmits light having a short wavelength and reflects light having a long wavelength is installed. An example is shown in FIG. In the figure, the reflecting mirror 23 is a reflecting mirror having such a property. If such a reflecting mirror 23 is used, the entire optical element 2 can be used for collecting light, and the brightness of incident light on the sample surface can be increased. Other parts are the same as those in the first embodiment, and a combination with the embodiments of FIGS. 2 to 4 is also included in the present embodiment.

<Embodiment 6> In the embodiments so far, the condensing optical system for the light of vacuum ultraviolet to soft X-rays and the condensing of the fluorescence emitted from the sample surface are performed using the same optical element. It was
The optical element used to collect these lights may be different. In the embodiment shown in FIG. 6, the optical element 2 collects light of soft X-rays from vacuum ultraviolet, and the optical element 24 different from the optical element 2 collects fluorescence emitted from the sample surface. It is an example. The fluorescence collected by the optical element 24 is the two-dimensional detector 10
Is detected by, and its output signal is converted into numerical data through the signal processing device 11 and sent to the control device 25. The controller 25 calculates the size of the fluorescent region based on the signal from the detector 10. Next, the control device 25 feeds back to the controller 16 that is the moving mechanism of the optical element 2 or the controller 17 of the moving mechanism 15 of the light source 1 so that the size of the fluorescent region is minimized. Adjust the placement of element 2.

As described above, if the incident light and the fluorescent light are collected by using different optical elements, there is an advantage that the reduction and enlargement ratios of the light collecting optical elements can be independently determined. still,
Although the optical axes of the optical element 2 and the optical element 24 do not match in FIG. 6, it is also possible to set the optical axes of these optical elements to match. In combination with the third embodiment, it is possible to scan the sample surface with the probe beam simultaneously with automatic focusing. <Embodiment 7> In the embodiments so far, from vacuum ultraviolet to soft X
The condensing optical system of the light of the line and the condensing of the fluorescence emitted from the sample surface are performed by using the reflection type optical element. Automatic focusing of the incident light on the sample surface can also be performed by using a transmission or diffraction type light condensing element such as a zone plate. The embodiment shown in FIG. 7 is an example in which a transmission / diffraction type light collecting element 26 is used as a light collecting element.

The incident light has a shorter wavelength than the fluorescence emitted from the sample surface. Since the shorter the wavelength of light is, the shorter the focal length of the optical element 26 is, the image of the fluorescent region can be formed behind the light source 1 as in the present embodiment. At this time, automatic focusing is performed by adjusting the sample table 4 as in the first embodiment.

In the surface analysis in which light in the soft X-ray region from vacuum ultraviolet is incident with a fixed wavelength, when the fluorescence emitted from the sample surface cannot be emitted off the axis of the condensing optical system, this embodiment is used. Is valid. In combination with the third embodiment, it is possible to scan the probe surface with the probe beam at the same time as the automatic focusing.

[0030]

According to the present invention, the focusing optical system for collecting light in the vacuum ultraviolet to soft X-ray region can be automatically focused on the sample surface, which facilitates surface analysis of a minute region. ..

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is a block diagram of a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a fifth embodiment of the present invention.

FIG. 6 is a block diagram of a sixth embodiment of the present invention.

FIG. 7 is a block diagram of a seventh embodiment of the present invention.

[Explanation of symbols]

1 ... Light source, 2 ... Optical element, 3 ... Sample, 4 ... Sample stand, 5 ...
Moving mechanism, 6, 8 ... Controller, 7 ... Analyzer, 9 ... Reflector, 10 ... Detector, 11 ... Signal processing device, 12 ... Control device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/66 J 8406-4M

Claims (32)

[Claims] 1. Light in the soft X-ray region is generated from vacuum ultraviolet light,
In the surface analysis method of collecting the light on the sample surface and observing the particles emitted from the surface of the sample by light irradiation, by observing the fluorescence generated by the light irradiation,
A surface analysis method characterized in that the light in the vacuum ultraviolet to the soft X-ray region is automatically focused on the sample surface. 2. The surface analysis method according to claim 1, wherein the automatic focusing is performed by adjusting the sample position so that the size of the fluorescence generation region is minimized. 3. The surface analysis method according to claim 1, wherein the automatic focusing is performed by adjusting the position of the incident light source so that the size of the fluorescence generation region is minimized. 4. The surface analysis method according to claim 1, wherein the automatic focusing is performed by adjusting the position of the condensing optical element so that the size of the fluorescence generation region is minimized. 5. The automatic focusing according to claim 1, wherein the position of the sample, the position of the incident light source, and the position of the condensing optical element are set so that the size of the fluorescence generation region is minimized. A surface analysis method performed by adjusting the above. 6. The surface analysis method according to claim 2, 3, 4 or 5, which uses a two-dimensional fluorescence detector as a method for observing the size of the fluorescence generation region. 7. The surface analysis method according to claim 6, wherein a photodiode array, a CCD, a position readout type microchannel plate, or the like is used as the two-dimensional fluorescence detector. 8. The surface analysis method according to claim 1, 2, 3, 4, 5, 6 or 7, wherein focusing on the sample surface and observation of fluorescence are performed by the same focusing element. 9. The surface analysis method according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the condensing element is a reflective optical element or a transmissive or diffractive optical element. 10. The surface analysis method according to claim 9, wherein the reflective optical element is an aspherical mirror such as an elliptical mirror, a Walter mirror, a Kirkpatrick Betz mirror, or the like. 11. The surface analysis method according to claim 9, wherein the transmission and diffraction type optical element is a zone plate. 12. Claims 1, 2, 3, 4, 5, 6, 7,
8. A surface analysis method according to 8, 9, 10 or 11, wherein a method of scanning an incident probe light on the sample surface is added. 13. The surface analysis method according to claim 12, wherein a sample stage is moved as a method of scanning the incident probe light on the sample surface. 14. The surface analysis method according to claim 12, wherein a light source is moved as a method of scanning the incident probe light on the sample surface. 15. The surface analysis method according to claim 12, wherein an optical element is moved as a method for scanning the incident probe light on the sample surface. 16. The surface analysis method according to claim 12, wherein two or more of a sample stage, a light source, and an optical element are moved as a method of scanning the incident probe light on the sample surface. 17. A surface analysis device comprising means for generating light in the vacuum ultraviolet to soft X-ray region, means for condensing the light on a sample surface, and means for condensing fluorescence generated by light irradiation, wherein the sample A surface analysis apparatus comprising: a light collecting means for collecting light onto a surface and a light collecting means for collecting fluorescence; and an automatic focusing means for collecting light in the vacuum ultraviolet to soft X-ray region onto a sample surface. 18. The surface analyzer according to claim 17, wherein the automatic focusing means includes means for adjusting the sample position so that the size of the fluorescence generation region is minimized. 19. The surface analysis apparatus according to claim 17, wherein the automatic focusing means includes means for adjusting the position of the incident light source so that the size of the fluorescence generation region is minimized. 20. The surface analysis device according to claim 17, further comprising means for adjusting the position of the condensing optical element so that the size of the fluorescence generation region is minimized in the automatic focusing means. 21. The automatic focusing means according to claim 17, wherein the sample position, the position of the incident light source, and the position of the condensing optical element are set so that the size of the fluorescence generation region is minimized. A surface analyzer equipped with means for adjusting the above. 22. The surface analyzer according to claim 18, 19, 20 or 21, wherein a fluorescence two-dimensional detector is used as a means for observing the size of the fluorescence generation region. 23. The surface analysis device according to claim 22, wherein a photodiode array, a CCD, or a position readout type microchannel plate is used as the two-dimensional fluorescence detector. 24. A method according to claim 17, 18, 19, 20, 21,
22. The surface analysis device according to 22 or 23, wherein the means for collecting light on the sample surface and the means for collecting fluorescence are the same. 25. A method according to claim 17, 18, 19, 20, 21,
22. The surface analysis device according to 22, 23 or 24, wherein the light condensing means is a reflection type optical element or a transmission type or diffraction type optical element. 26. The surface analyzer according to claim 25, wherein the reflection type optical element as the light converging means is an aspherical mirror such as an elliptic mirror, a Walter mirror, a Kirkpatrick-Betz mirror. 27. The surface analysis device according to claim 25, wherein the transmission / diffraction optical element as the light converging means is a zone plate. 28. A method according to claim 17, 18, 19, 20, 21,
22, 23, 24, 25, 26, or 27, a surface analyzer equipped with means for scanning the incident probe light on the sample surface. 29. The surface analyzer according to claim 28, wherein the sample stage is moved as a means for scanning the incident probe light on the sample surface. 30. The surface analysis device according to claim 28, wherein a light source is moved as a means for scanning the incident probe light on the sample surface. 31. The surface analysis device according to claim 28, wherein an optical element is moved as a means for scanning the incident probe light on the sample surface. 32. The surface analyzer according to claim 28, wherein two or more of a sample stage, a light source, and an optical element are moved as means for scanning the incident probe light on the sample surface.