JP2009079955A - Depth direction analysis method of sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simply-operable depth direction analysis method of a sample. <P>SOLUTION: Photoelectrons having each different capture angle α are condensed into a visual field restricting diaphragm 15 from the sample 4, while changing the intensity of an electrostatic lens 13 successively, with a sample stage 5 having the sample 4 placed thereon and tilted at an angle θ, and simultaneously an aperture diameter of an angle restricting diaphragm 16 is changed so that electrons having each capture angle pass therethrough, and each spectrum based on photoelectrons detected by a detector 12 is determined for each analysis depth determined from each capture angle α. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

   The present invention relates to a sample depth direction analysis method using an electron spectrometer such as a photoelectron spectrometer.

A photoelectron spectrometer is an apparatus that irradiates a sample surface with X-rays, analyzes photoelectrons emitted from the sample by the irradiation with an electron spectrometer, and obtains an energy spectrum. By analyzing the obtained spectrum, It is possible to know surface elements and chemical states of the elements.
FIG. 1 shows a schematic example of such a photoelectron spectrometer.

  In the figure, reference numeral 1 denotes an analysis chamber, the interior of which is evacuated to a vacuum by an exhaust device 2.

  A sample 4 supported by a sample holder 3 is disposed in the center of the analysis chamber 1, and the sample holder 3 is placed on a sample stage 5. This sample stage is moved in a three-dimensional (X, Y, Z) direction by adjusting a sample stage position adjusting mechanism 6 attached to the side wall of the analysis chamber 1, or tilted with the X axis or Y axis as a rotation axis. It is made to be able to let you.

  Reference numeral 7 denotes an X-ray source for photoelectron excitation, which is attached to the upper wall of the analysis chamber 1 so that the sample 4 can be irradiated with X-rays. Reference numeral 8 denotes a power source of the X-ray source.

  An electron spectrometer 9 is attached to the upper lid of the analysis chamber 1. The electron spectrometer includes an input lens unit 10, an analyzer 11 for energy analysis of photoelectrons from the input lens unit, and a detector 12 for detecting photoelectrons selected by the analyzer.

  The input lens unit 10 includes electrostatic lenses 13 and 14, and a field limiting aperture 15 for limiting a region for taking in photoelectrons generated on the surface of the sample 4 between these lenses, By limiting the taking-in angle of the photoelectrons that have passed through the field limiting aperture, the lens system has an angle limiting aperture 16 that reduces blur due to spherical aberration of the lens system and compensates for the accuracy of the analysis region on the sample surface.

  The electrostatic lens 13 is for converging photoelectrons from the sample 4 in the vicinity of the field-limiting diaphragm 15, and the electrostatic lens 14 decelerates photoelectrons collected by the electrostatic lens 13, For focusing on the entrance slit S of the analyzer 11.

The field limiting diaphragm 16 is arranged so as to partition the cylinder of the input lens unit so that the center of the opening K1 is positioned on the optical axis O of the input lens unit 9. For example, an iris diaphragm is used as the field limiting diaphragm, and the aperture diameter can be changed continuously by adjusting the aperture diameter adjusting mechanism 17.
The angle limiting diaphragm 16 is arranged so as to partition the cylinder of the input lens portion so that the center of the opening K2 is positioned on the optical axis O of the input lens portion 9. For example, an iris diaphragm is used as the angle limiting diaphragm, and the aperture diameter can be continuously changed by adjusting the aperture diameter adjusting mechanism 18.

  A power supply unit 19 controls the voltage to the electrostatic lenses 13 and 14, the voltage to the analyzer 11, and the voltage to the detector 12.

  A control device 20 generates a photoelectron spectrum based on a signal from the detector 12 and displays the photoelectron spectrum on the display device 21, or the power supply unit 19, the sample stage device adjustment mechanism 6, the aperture diameter adjustment mechanisms 17, 18 and so on. It acts as a so-called central control device that sends commands to

  When analyzing a sample in the apparatus having such a configuration, the operator adjusts the aperture diameter adjusting mechanism 17 to set the aperture diameter of the field limiting aperture 15 to a predetermined size optimum for the sample analysis at this time. Further, the aperture diameter adjusting mechanism 18 is adjusted so that the aperture diameter of the angle limiting diaphragm 16 is set to a predetermined size that reduces blurring caused by spherical aberration of the lens system.

  The degree of vacuum in the analysis chamber 1 is constantly monitored by the control device 20. When the degree of vacuum in the analysis chamber 1 enters a predetermined range, the control device 20 performs X-ray irradiation on the sample 4. A radiation irradiation command is sent to the X-ray source power supply 8. Further, the control device sends to the power supply unit 19 a command for applying a predetermined voltage suitable for the sample analysis at this time to the electrostatic lenses 13 and 14, the analyzer 11 and the detector 12 of the electron spectrometer 9.

  In accordance with such a command, a voltage is supplied from the power supply unit 19 to the electrostatic lens 13 so as to focus the photoelectrons from the sample 4 near the opening of the field limiting aperture 15 by the electrostatic lens 13. A voltage is applied to the electrolens 14 to decelerate the photoelectrons focused on the aperture of the field limiting aperture 15 and to focus on the entrance slit S of the analyzer 11.

  In such a state, X-rays are generated from the X-ray source 7 by the operation of the X-ray source power supply 8 in response to a command from the control device 20 and irradiated to the sample 4. Photoelectrons are emitted from the sample by the X-ray irradiation.

  The photoelectrons are focused in the vicinity of the field limiting aperture 15 by the electrostatic lens 13, and the photoelectrons that have passed through the aperture K1 of the field limiting aperture 16 and the aperture K2 of the angle limiting aperture 16 are decelerated and focused by the electrostatic lens 14, and the analyzer 11. Led to.

  The photoelectrons subjected to energy selection by the analyzer are detected by the detector 12. The detector converts the detected photoelectron signal into an electrical signal and outputs it.

The control device 20 generates a photoelectron spectrum based on the output signal and causes the display device 21 to display the photoelectron spectrum.
Japanese Patent Laid-Open No. 01-274050 JP-A-10-104179 Japanese Patent Laid-Open No. 2001-083111 JP 2001-266787 A JP 2003-1887738 A

  In the sample analysis in the photoelectron spectrometer, the depth direction analysis of a semiconductor device having a fine stacked structure may be performed.

  When performing such depth direction analysis, a process of irradiating the sample surface with accelerated ions (for example, Ar ions) to etch the sample surface to expose the inside of the sample from the surface, The depth direction of the sample is analyzed by alternately performing the analysis process and analyzing the exposed surface at each depth.

  However, this method has a problem of destroying the sample.

  As another depth direction analysis method, the process of adjusting the sample stage position adjusting mechanism 6 to tilt the sample stage 5 with the X axis or the Y axis as the rotation axis, and the process of performing the sample analysis at the tilt angle are performed. The sample depth direction analysis is performed by alternately performing the sample analysis at each inclination angle. In detail, as shown in FIG. 2, when the sample tilt angle is 0 ° (FIG. 2A), the analysis depth To is equal to the photoelectron escape depth d, and the inelastic mean free path is obtained. Approximate. At the sample tilt angle θ ((b) in FIG. 2), the analysis depth T is T = dcos θ. Therefore, by changing the sample tilt angle and obtaining the photoelectron spectrum each time, the sample depth direction is obtained. Analysis becomes possible. In this depth direction analysis method, photoelectrons from the sample 4 taken into the input lens unit 10 are fixed along the optical axis O (parallel to the optical axis O).

  However, this method is difficult to operate because the sample stage 5 itself has to be inclined at different angles many times.

  The present invention has been made in view of the above problems, and an object thereof is to provide a novel method for analyzing the depth direction of a sample.

  The sample depth direction analysis method of the present invention comprises an irradiation means for irradiating a sample placed on a sample stage supported by a sample stage in an analysis chamber, a field limit stop, an angle limit stop, and electrons emitted from the sample. A first lens for focusing the light on the field limiting diaphragm, a second lens for decelerating and focusing the focused electrons, an analyzer for sorting the slowed and focused electrons by energy, and detecting the electrons sorted by the analyzer An electron spectrometer equipped with a detector, a sample stage drive mechanism capable of tilting the sample stage around at least an axis perpendicular to the optical axis, and a field limit capable of changing the aperture diameter of the field limit stop Aperture aperture drive mechanism, an angle limit aperture drive mechanism that can change the aperture diameter of the angle limit aperture, and a strength of each lens A depth direction analysis method of a sample by an electron spectrometer equipped with a lens power source capable of taking in from the sample by sequentially changing the intensity of the first lens while the sample stage is inclined at an angle θ A spectrum based on electrons detected by the detector each time an electron having a different angle α is focused on the field-limiting aperture, and at the same time, the aperture diameter of the angle-limiting aperture is changed so that electrons of each capture angle pass. Is obtained for each analysis depth obtained from the capture angle α.

  The depth direction analysis method for a sample according to the present invention includes an irradiation means for irradiating a sample placed on a sample stage supported by a sample stage in an analysis chamber, a field limiting aperture, an angle limiting aperture, and the field limiting aperture. An electron spectrometer having a lens for decelerating and focusing the electrons, an analyzer for selecting the decelerated and focused electrons by energy, and a detector for detecting the electrons selected by the analyzer; An imaging lens that focuses the electrons emitted from the sample onto the field limiting aperture, a sample stage drive mechanism that can tilt the sample stage at least about an axis perpendicular to the optical axis, and the field limiting aperture A field-limiting diaphragm aperture drive mechanism that can change the aperture diameter of the lens, and an angle-limited diaphragm aperture that can change the aperture diameter of the angle-limiting diaphragm A method for analyzing the depth direction of a sample by an electron spectroscopic device including a moving mechanism and a lens power source capable of changing the intensity of each lens, wherein the imaging is performed in a state where the sample stage is inclined at an angle θ. By sequentially changing the intensity of the lens, the electrons having different capture angles α from the sample are focused on the field-limiting aperture, and at the same time, the aperture diameter of the angle-limiting aperture is changed so that electrons of each capture angle pass, A spectrum based on electrons detected by the detector is obtained for each analysis depth obtained from the capture angle α.

  According to the present invention, the depth direction analysis of a sample can be performed extremely easily.

  The present invention is based on the following principle.

  When the sample is tilted and depth direction analysis is performed, when the sample tilt angle is θ (the state shown in FIG. 2B), the analysis depth t is d. It has already been explained that T = d cos θ.

  Now, when the sample is irradiated with X-rays, photoelectrons are emitted from the sample at various angles. At this time, for example, as shown in FIG. 3, when photoelectrons having an angle (taken angle) α are taken into the electron spectrometer, the taken photoelectrons are detected from the depth (= Tα) of dcos (θ−α). It is a thing. Therefore, if this photoelectron uptake angle is changed, photoelectrons at various analysis depths can be detected, and photoelectron spectra at various analysis depths should be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows one schematic example of an electron spectroscopic apparatus that performs the sample depth direction analysis method of the present invention. In the figure, the same reference numerals as those used in FIG. 1 denote the same components.

  The photoelectron spectrometer shown in FIG. 2 differs from the photoelectron spectrometer shown in FIG. 1 in the following configuration.

  In order to change the taking-in angle of the photoelectrons from the sample 4 electro-optically, a taking-in angle control unit 22 is provided, and the unit is operated by a command from the control device 20. Further, a memory 23 for storing the photoelectron spectrum signal generated by the control device 20 is provided.

  In the apparatus having such a configuration, as an initial state, among the photoelectrons from the sample 4, so-called electrons along the optical axis O (parallel to the optical axis O), that is, so-called capturing angles of 0 ° are opened in the field limiting aperture 15. A voltage that converges in the vicinity decelerates photoelectrons that converge in the vicinity of the aperture of the field limiting aperture, and a voltage that converges on the entrance slit S of the analyzer 11 from the power supply unit 19 to the electrostatic lenses 13 and 14. A command is sent from the control device 20 to the power supply unit 19 so as to be applied to the power supply unit 19 respectively. Further, a command from the control device 20 is sent to the sample stage position adjusting mechanism 6 and the sample stage 5 is tilted at an angle θ with the X axis or the Y axis as the rotation axis.

  In this state, when the sample 4 is irradiated with X-rays from the X-ray source 7, photoelectrons are emitted from the sample, and the photoelectrons are focused by the electrostatic lens 13 in the vicinity of the field limiting aperture 15, and the field limiting is performed. The photoelectrons that have passed through the aperture K1 of the aperture stop and the aperture K2 of the angle limiting aperture 16 are decelerated by the electrostatic lens 14 and focused on the entrance slit S of the analyzer 11 and guided to the analyzer. The photoelectrons guided to the analyzer are photoelectrons captured at an capture angle of 0 °, and are photoelectrons having an analysis depth To (= d cos θ) as described with reference to FIG.

  The photoelectrons subjected to energy selection by the analyzer are detected by the detector 12, converted into electrical signals, and output. The control device 20 generates a photoelectron spectrum based on the output signal and temporarily stores it in the memory 23.

  Next, among the photoelectrons from the sample 4, a voltage at which an opening angle from the optical axis O, that is, an electron having a capture angle α 1 is focused in the vicinity of the opening of the field limiting aperture 15 is near the aperture of the field limiting aperture. The controller 20 decelerates the photoelectrons focused on the light source and applies a voltage to the electrostatic lenses 13 and 14 from the power supply unit 19 so as to focus on the entrance slit S of the analyzer 11. Send a command to. Further, from the control device 20, the opening diameter of the angle limiting diaphragm 16 is set to be an opening diameter D 1 that allows only photoelectrons of the taking-in angle α 1 that converges in the vicinity of 1 of the opening of the field limiting diaphragm 15 to pass. A command is sent to the opening diameter adjusting mechanism 18.

  In this state, when the sample 4 is irradiated with X-rays from the X-ray source 7, the photoelectrons emitted from the sample are captured at the capture angle α1 as indicated by the light ray A in the light ray diagram of FIG. Only the photoelectrons that have been collected are focused in the vicinity of the field limiting aperture 15 by the electrostatic lens 13, and the photoelectrons that have passed through the aperture K 1 of the field limiting aperture 16 and the aperture K 2 of the angle limiting aperture 16 are decelerated by the electrostatic lens 14 and the analyzer 11. The light is focused on the entrance slit S and guided to the analyzer. The photoelectrons guided to the analyzer are photoelectrons taken in at the take-in angle α1 and are photoelectrons having an analysis depth T1 (= dcos (θ−α1)) as described in the above principle.

  The photoelectrons subjected to energy selection by the analyzer are detected by the detector 12, converted into electrical signals, and output. The control device 20 generates a photoelectron spectrum based on the output signal and temporarily stores it in the memory 23.

  Next, among the photoelectrons from the sample 4, a voltage at which an opening angle from the optical axis O, that is, a so-called electron whose capture angle is α <b> 2 is focused in the vicinity of the opening of the field limiting aperture 15 is near the aperture of the field limiting aperture. The controller 20 decelerates the photoelectrons focused on the light source and applies a voltage to the electrostatic lenses 13 and 14 from the power supply unit 19 so as to focus on the entrance slit S of the analyzer 11. Send a command to. Further, from the control device 20, the opening diameter of the angle limiting diaphragm 16 is set to be an opening diameter D2 that allows only photoelectrons of the taking-in angle α2 that converges in the vicinity of 1 of the opening of the field limiting diaphragm 15 to pass. A command is sent to the opening diameter adjusting mechanism 18. Incidentally, the angle control diaphragm whose aperture diameter is changed to D2 is represented by 15 ′ in FIG. 5 and is drawn on the right side of the angle control diaphragm 15 at the aperture diameter D1 so that the change of the aperture diameter can be understood. Actually, they are arranged at the same position.

  In this state, when the sample 4 is irradiated with X-rays from the X-ray source 7, the photoelectrons emitted from the sample are captured at the capture angle α2 as indicated by the light beam B in the light ray diagram of FIG. Only the photoelectrons that have been collected are focused in the vicinity of the field limiting aperture 15 by the electrostatic lens 13, and the photoelectrons that have passed through the aperture K 1 of the field limiting aperture 16 and the aperture K 2 of the angle limiting aperture 16 are decelerated by the electrostatic lens 14 and the analyzer 11. The light is focused on the entrance slit S and guided to the analyzer. The photoelectrons guided to the analyzer are photoelectrons taken in at the take-in angle α2, and are photoelectrons having an analysis depth T2 (= dcos (θ−α2)) as described in the above principle.

  The photoelectrons subjected to energy selection by the analyzer are detected by the detector 12, converted into electrical signals, and output. The control device 20 generates a photoelectron spectrum based on the output signal and temporarily stores it in the memory 23.

  Next, among the photoelectrons from the sample 4, a voltage at which an opening angle from the optical axis O, that is, an electron having a capturing angle α3 is focused near the opening of the field limiting aperture 15 is near the aperture of the field limiting aperture 15. The controller 20 decelerates the photoelectrons focused on the light source and applies a voltage to the electrostatic lenses 13 and 14 from the power supply unit 19 so as to focus on the entrance slit S of the analyzer 11. Send a command to. Further, from the control device 20, the opening diameter of the angle limiting diaphragm 16 is set to be an opening diameter D3 that allows only photoelectrons having a capturing angle α3 that converges in the vicinity of one of the openings of the field limiting diaphragm 15 to pass. A command is sent to the opening diameter adjusting mechanism 18. Incidentally, the angle control diaphragm whose aperture diameter is changed to D3 is indicated by 15 ″ in FIG. 5 and is drawn on the right side of the angle control diaphragm 15 ′ at the aperture diameter D2 so that the change of the aperture diameter can be understood. However, it is actually arranged at the same position as 15.

  In this state, when the sample 4 is irradiated with X-rays from the X-ray source 7, the photoelectrons emitted from the sample are captured at the capture angle α3 as indicated by the light ray C in the light ray diagram of FIG. Only the photoelectrons that have been collected are focused in the vicinity of the field limiting aperture 15 by the electrostatic lens 13, and the photoelectrons that have passed through the aperture K 1 of the field limiting aperture 16 and the aperture K 2 of the angle limiting aperture 16 are decelerated by the electrostatic lens 14 and the analyzer 11. The light is focused on the entrance slit S and guided to the analyzer. The photoelectrons guided to the analyzer are photoelectrons taken in at the take-in angle α3, and are photoelectrons having an analysis depth T3 (= dcos (θ−α3)) as described in the above principle. .

  The photoelectrons subjected to energy selection by the analyzer are detected by the detector 12, converted into electrical signals, and output. The control device 20 generates a photoelectron spectrum based on the output signal and temporarily stores it in the memory 23.

  Thereafter, the series of operations for generating the photoelectron spectrum is repeated by changing the capture angle in this way.

  Thereafter, the control device 20 reads out the analysis depth signal corresponding to each capture angle and the photoelectron spectrum signal corresponding to each analysis depth from the memory 23, and displays the photoelectron spectrum corresponding to each analysis depth on the display device 21. Let

  In the above example, the photoelectrons from the sample 4 are focused by the electrostatic lens 13 in the vicinity of the opening K1 of the field limiting aperture 15. However, a magnetic field type imaging lens is disposed below the sample 4. Instead of using the electrostatic lens 13, the magnetic imaging lens may be used to focus the photoelectrons from the sample 4 in the vicinity of the opening K1 of the field limiting aperture 15, which is wider. Angle photoelectrons can be focused.

  In the above example, the method for analyzing the deep direction of the night sample in the photoelectron spectrometer has been described, but this method can also be applied to other electron spectrometers such as an Auger electron spectrometer.

1 shows a schematic example of a conventional electron spectrometer. This is used for explaining the conventional depth direction analysis. This is used to explain the principle of the present invention. 1 shows a schematic example of an electron spectrometer of the present invention. FIG. 5 is a ray diagram used for explaining the operation of the apparatus of FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Analysis chamber 2 ... Exhaust device 3 ... Sample holder 4 ... Sample 5 ... Sample stage 6 ... Sample stage position adjustment mechanism 7 ... X-ray source for photoelectron excitation 8 ... Power source of X-ray source 9 ... Electron spectrometer 10 ... Input lens DESCRIPTION OF SYMBOLS 11 ... Analyzer 12 ... Detector 13 ... Condensing lens 14 ... Condensing lens 15 ... Field-limiting aperture 16 ... Angle limiting aperture 17 ... Aperture diameter adjusting mechanism 18 ... Aperture diameter adjusting mechanism 19 ... Power supply unit 20 ... Control device 21 ... Display device 22 ... take-in angle control unit 23 ... memory S ... incident slit

Claims (4)

An irradiating means for irradiating an ionizing radiation to a sample that is supported by a sample stage in the analysis chamber; a field limiting aperture; an angle limiting aperture; a first lens that focuses electrons emitted from the sample to the field limiting aperture; A second lens for decelerating and focusing the focused electrons, an analyzer for selecting the decelerated and focused electrons by energy, an electron spectrometer having a detector for detecting the electrons selected by the analyzer, and the sample A sample stage drive mechanism capable of tilting the stage at least about an axis perpendicular to the optical axis, a field limit stop aperture diameter drive mechanism capable of changing the aperture diameter of the field limit stop, and the angle limit stop Provided with an angle limiting aperture opening diameter driving mechanism capable of changing the opening diameter, and a lens power source capable of changing the intensity of each lens. A method of analyzing the depth direction of a sample by a child spectroscope, wherein the electron beam having a different capture angle α from the sample is sequentially changed by changing the intensity of the first lens while the sample stage is inclined at an angle θ. At the same time, the aperture diameter of the angle-limiting aperture is changed so that electrons at each capture angle pass, and a spectrum based on the electrons detected by the detector is obtained from each capture angle α. Depth direction analysis method of the sample that is calculated for each analysis depth.   Irradiation means for irradiating ionizing radiation to a sample arranged supported by a sample stage in the analysis chamber, a field limiting aperture, an angle limiting aperture, a lens for decelerating and focusing electrons focused on the field limiting aperture, the deceleration and An analyzer for selecting focused electrons by energy and a detector for detecting electrons selected by the analyzer; and a field-restricting aperture for electrons emitted from the sample disposed below the sample. An imaging lens for focusing the light source, a sample stage driving mechanism capable of tilting the sample stage at least about an axis perpendicular to the optical axis, and a field-limiting aperture opening capable of changing the aperture diameter of the field-limiting aperture. The aperture driving mechanism, the angle limiting aperture opening diameter driving mechanism capable of changing the aperture diameter of the angle limiting aperture, and the strength of each lens are changed. A depth direction analysis method of a sample by an electron spectrometer equipped with a lens power source capable of performing the above-described process, wherein the intensity of the imaging lens is sequentially changed from the sample while the sample stage is inclined at an angle θ. Based on the electrons detected by the detector, each time the electrons with different capture angles α are focused on the field-limiting aperture, and at the same time, the aperture diameter of the angle-limiting aperture is changed so that electrons of each capture angle pass. A sample depth direction analysis method in which a spectrum is obtained for each analysis depth obtained from the capture angle α.   3. The depth direction analysis method for a sample according to claim 1, wherein the ionizing radiation is X-rays.   3. The depth direction analysis method for a sample according to claim 1 or 2, wherein the analysis depth is obtained based on an equation of dcos (θ-α), where d is the escape depth of electrons emitted from the sample. .

Images