JP2006132975A - Method and device of thin layer analysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for determining the element composition of a thin-layer measurement layer in an analysis specimen having a thin-layer laminated structure. <P>SOLUTION: This method of thin layer analysis comprises: a process for performing oblique etching or oblique grinding for the analysis specimen having a thin-layer laminated structure to expose the measurement layer; a process for exciting characteristic X rays from the exposed measurement layer by electron beam irradiation; a process for detecting only the characteristic X rays from the measurement layer; and a process for determining the element composition from the detected X rays. A characteristic X-ray analyzer is included which is equipped with an irradiation means; a specimen hold means; an incident X-ray adjustment means; and an X-ray detection means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for analyzing the elemental composition of thin layers. More specifically, the present invention relates to an element by analyzing characteristic X-rays excited by electron beam irradiation from a measurement layer exposed obliquely by processing an analysis sample having a thin layered structure. The present invention relates to a thin layer analysis method and apparatus for determining a composition.

  Conventionally, as a technique for analyzing a micro area of a sample or elemental analysis of a surface, an electron beam probe that irradiates a sample with an electron beam and detects characteristic X-rays excited from the irradiated micro area or surface by an X-ray detector. A micro X-ray analyzer (EPMA) is known. EPMA utilizes the fact that when a sample is irradiated with an electron beam, each element existing in the irradiated region emits characteristic X-rays having specific energy. By analyzing the energy spectrum of characteristic X-rays excited by an electron beam, the composition of the elements present in the irradiated region can be known.

  However, in the conventional EPMA, it has been difficult to analyze, for example, a minute object existing on the sample surface or a thin layer (thickness or less) on the sample surface. This is because the characteristic X-rays emitted from the sample include characteristic X-rays from both the inside of the sample and the minute object or thin layer on the surface of the sample, and the intensity of the characteristic X-ray from the inside of the sample is This is because the characteristic X-rays from the minute object or thin layer on the surface are stronger than the characteristic X-rays, and only the characteristic X-rays from the minute object or thin layer cannot be extracted and analyzed. In this regard, a method of exciting characteristic X-rays only from the vicinity of the sample surface by irradiating a low energy (low acceleration) electron beam to reduce the depth of penetration of the electron beam into the sample can be considered. However, the use of low-energy electron beams limits the elements that can be detected, and is often not appropriate, for example, when the elements to be detected are unknown and all elements need to be detected.

As a solution to this problem, a new EPMA based on oblique emission X-ray measurement (hereinafter referred to as “oblique emission EPMA”) has been proposed. This oblique emission EPMA detects minute X-rays on the sample surface or a thin layer on the sample surface by detecting characteristic X-rays in an angle range (angle range from the surface) in which characteristic X-rays are not emitted from the inside of the sample due to a total reflection phenomenon. Only characteristic X-rays from the above are detected and analyzed (Patent Documents 1 and 2, Non-Patent Document 1).
JP 2001-208708 A JP 2002-286661 A K. Tsuji et al. , Anal. Chem. 71 (1999): 2497-2501

  The oblique emission EPMA enables elemental analysis of the extreme surface or thin layer of the sample, but information on the depth direction of the sample cannot be obtained. This is because, as described above, the characteristic X-rays from the inside reflect all elements existing in the region where the electron beam has entered. Therefore, in order to analyze the elemental composition of each layer of the intermediate layer of a sample having a thin laminated structure (for example, a semiconductor device having a laminated structure), it is necessary to expose the layers to be measured one by one on the surface. . However, it is difficult and time-consuming to uniformly peel the upper layer of the measurement layer, and when there are a plurality of intermediate layers, there is a problem that the peeling-analysis process needs to be repeated many times. In addition, there is a case where the layer interface is altered due to the effect of the layer stack on the upper side, and if the analysis is performed at the layer interface, the elemental composition of the measurement layer cannot be correctly evaluated.

  As described above, the conventional EPMA including the oblique emission EPMA can analyze the elemental composition of the intermediate thin layer of the analysis sample having the thin layered structure with higher accuracy (unit of 1% or less) and the depth. The elemental composition distribution in the direction cannot be easily obtained.

  It is an object of the present invention to provide a method and apparatus for overcoming the above-mentioned problems of the conventional method and analyzing the elemental composition and distribution of a sample having a laminated structure with the accuracy required for the design and quality control of the laminated structure. .

  In order to achieve this purpose, a process is carried out on an analytical sample having a thin layered structure, and the measurement layer is exposed obliquely with respect to the layer interface; characteristics from the measurement layer exposed by electron beam irradiation There is provided a thin layer analysis method comprising: a step of exciting X-rays; a step of detecting only characteristic X-rays from a measurement layer; and a step of determining an elemental composition from the detected characteristic X-rays.

  The outline of the method of the present invention will be described with reference to FIG. First, the analysis sample 2 having a thin layered structure is processed to expose the measurement layer 6 obliquely to the layer interface 8 (for example, at an angle θ with respect to the layer interface). Next, the electron beam 10 is irradiated onto the exposed surface 4 of the measurement layer to excite characteristic X-rays. At this time, the electron beam 10 may reach the lower layer of the measurement layer, and the characteristic X-rays excited and emitted there include information on the element composition of the lower layer as well as the measurement layer. Is not suitable. Therefore, characteristic X-rays that do not include those from the inside (deep part) of the characteristic X-rays emitted outside the sample by the oblique emission X-ray measurement method using the total reflection phenomenon at the interface between the sample and the outside. That is, only characteristic X-rays from the measurement layer are detected by detecting characteristic X-rays 20 having a small emission angle α from the irradiated surface. By determining the elemental composition from the characteristic X-rays thus detected, the elemental composition of the thin measurement layer can be analyzed.

  In the processing, a method known in the art can be used, which can expose the inside of the sample and does not affect the elemental composition of the exposed surface that is processed. For example, polishing and etching can be used. A processing method used for surface analysis with less damage to the processing surface is particularly suitable in the method of the present invention.

  As the etching, among dry etchings known in the art, etching that does not affect the elemental composition of the processed surface is appropriate. For example, ion etching, in particular, low acceleration etching using argon (Ar) gas can be used. Ion etching using Ar gas is known in the art, and can be performed using a commercially available apparatus (for example, a flat milling etching apparatus). The Ar ion gun can be used as an accelerating voltage of 0.5 to 6 kV (preferably 0.5 to 2 kV) and a current of 10 to 30 μA (preferably 20 μA), but a value outside this range can be used if necessary. In order to expose the measurement layer obliquely by ion etching, an ion gun is disposed obliquely with respect to the layer interface of the measurement layer (if necessary, a predetermined angle θ) and irradiated with ions. Alternatively, the ion beam reflects the current density distribution, and has a scallop-like etching rate distribution in which the irradiation center is deeper and the peripheral part is shallower. Therefore, the ion beam is inclined with respect to the layer interface of the measurement layer (if necessary, predetermined The sample may be arranged at a position of a velocity distribution that provides an etching surface having an angle θ).

  Polishing known in the art can be used for polishing. For example, after performing rough polishing with a coarse-grained polishing tool, finish polishing may be performed with a fine-grained polishing tool to finish the processed surface smoothly. As the polishing tool, for example, polishing paper can be used. In order to expose the measurement layer obliquely by polishing, the sample and the polishing tool are arranged and polished so that the polishing surface of the polishing tool is inclined with respect to the layer interface of the measurement layer (if necessary, a predetermined angle θ). To do. If the sample is laminated horizontally with respect to the substrate, for convenience, polishing is performed obliquely with respect to the upper or lower surface of the sample, and as a result, the measurement layer is exposed obliquely with respect to the laminate interface. You may let them.

  In the present invention, “oblique” means crossing at an angle θ other than perpendicular to the reference plane. In the laminated structure, the reference surface may be a surface or a layer interface, but when referring to “an oblique” for the intermediate layer, it is the layer interface of the intermediate layer. Therefore, the exposed surface of the exposed measurement layer is a surface other than a vertical surface intersecting the layer interface of the measurement layer, and is preferably a plane (in this case, 0 <θ <90 °). Not.

  In the present invention, the “measuring layer” refers to at least one intermediate layer in an analytical sample having a thin layered structure in which elemental composition analysis should be performed by detecting and measuring characteristic X-rays. The measurement layer is preferably two or more intermediate layers. When there are two or more exposed measurement layers, the steps from the excitation step to the element composition determination step are repeated for each measurement layer.

The method of the present invention is preferably used for an analysis sample in which the thickness d of the measurement layer is smaller than the minimum beam diameter b on the electron beam irradiation surface to be used. In this case, the angle θ formed by the exposed surface with respect to the layer interface is to prevent characteristic X-rays from the lower layer of the measurement layer from being inevitably detected without being eliminated even by the oblique emission X-ray measurement method. It is set so as to satisfy the formula d> a + b * sin θ (a: measurement critical film thickness) (FIG. 1B).
The measurement critical film thickness a in the previous equation is calculated by defining the depth at which the primary X-rays are incident on each composition crystal and the intensity is attenuated to 1 / e. For example, in the AlGaInP crystal, the value of a is 4 nm.

Concavities and convexities generated on the exposed surface by processing may affect the excitation and detection of characteristic X-rays from the measurement layer. Theoretically, the measurable distance m on the exposed surface of the measurement layer is expressed by the equation m = (da) / sin θ−β / tan θ (measurement layer thickness d, measurement critical thickness a, measurement layer exposed surface and Since the angle θ formed by the layer interface and the surface irregularity β) are expressed, when the electron beam focused on the beam diameter b is irradiated on the exposed surface of the measurement layer, the measurement layer must be satisfied unless the relationship b <m is satisfied. In some cases, characteristic X-rays from the upper layer and / or the lower layer are inevitably detected (FIG. 1B). Therefore, it is necessary to employ an etching or polishing method with small surface irregularities and little surface damage.
Here, the evaluation of the surface roughness β can be performed with an atomic force microscope (AFM). Further, the value of β can be controlled by ion acceleration voltage and current in ion etching, and can be controlled by grain size of finishing polishing and finishing method (using mechanochemical polishing, etc.) in polishing.

  For irradiation with an electron beam, an irradiation source (for example, an electron gun) known in the art can be used. The electron beam is generally accelerated so as to have an energy of about 1 to 30 keV, and is focused to a diameter of about 40 nm to 300 nm on the analysis surface of the sample. When the electron beam is irradiated to the measurement layer on the exposed surface, care should be taken not to irradiate the adjacent layer on the exposed surface. This is to avoid that it is impossible to extract and detect only characteristic X-rays from the measurement layer. If necessary, the electron beam irradiation area is confirmed by an electron microscope image.

  In the present invention, the characteristic X-ray to be detected and analyzed is a characteristic X-ray excited substantially only from the measurement layer (that is, substantially free of characteristic X-rays excited from a layer adjacent to the measurement layer). is there. In order to detect only characteristic X-rays from a thin measurement layer, oblique emission X-ray analysis (see, for example, Non-Patent Document 1, Patent Documents 1 and 2) can be used. In the oblique emission X-ray analysis method, the smaller the angle from the measurement surface of the characteristic X-ray incident on the X-ray detection means (oblique emission angle), the deeper the characteristic X-ray incident on the X-ray detection means. Characteristic X-rays from the inside of the sample are not included, and only characteristic X-rays from near the shallower surface are included. However, it should be noted that if the oblique emission angle is too small, the amount of characteristic X-rays that can be detected is too small to be suitable for measurement. The oblique emission angle of the characteristic X-ray to be detected is generally 0 to 5 °, preferably 0 to 4 °, more preferably 0 to 3 °, still more preferably 0 to 2 °, and most preferably 0 to 1 °. Although the upper limit of the oblique emission angle depends on the layer thickness of the measurement layer, it can be used outside this range depending on the layer thickness. The characteristic X-ray to be detected / analyzed substantially does not include the characteristic X-ray from the lower layer of the measurement layer and is substantially the characteristic X-ray from only the measurement layer. Even if the X-ray oblique emission angle is further reduced, the obtained characteristic X-ray energy profile (number of peaks) may be confirmed to be substantially unchanged. As the X-ray detection means, any known X-ray analyzer can be used. Preferably, an energy dispersive X-ray detector (EDS) or a wavelength dispersive X-ray detector (WDS) is used.

  In the case where analysis is difficult due to charge-up caused by electrical resistance between layers, a thin film of a conductive substance other than the elements constituting the sample may be formed on the sample surface before processing the sample. The conductive material is known in the art, and is preferably carbon or metal. The conductive metal is, for example, gold (Au), copper (Cu), silver (Ag), or platinum (Pt), and preferably gold or copper. The thin film of the conductive material is formed on the sample surface by a method known in the art, and is formed by, for example, vacuum evaporation or electron beam evaporation.

  In one embodiment of the present invention, two or more analysis samples are processed in advance to expose the measurement layer, and then the analysis sample is simultaneously held by one holding means, from the excitation step to the element composition determination step. To implement. In this case, preferably, two or more analysis samples are processed so that the angle of the exposed surface with respect to one surface is the same. Such processing makes it easy to hold the exposed measurement layers in parallel with one holding means, and as a result, only characteristic X-rays excited from the measurement layer can be detected during measurement. Since it is not necessary to readjust the positional relationship between the sample once set and the X-ray detection means so that it can be done between samples (that is, it is possible only by fine adjustment), continuous analysis of the sample becomes easy and quick. become.

  In another embodiment of the present invention, the standard sample is simultaneously held in one holding means together with one or more analysis samples, and the process from the excitation process to the element composition determination process is repeated. At this time, the standard sample and the analysis sample are preferably processed so that the angle of the exposed surface with respect to one surface is the same. In this specification, the “standard sample” refers to a sample having a known elemental composition (in the case of a standard sample having a layer structure, an elemental composition for each layer) or a sample having a desired elemental composition.

  The present invention also provides a characteristic X-ray analysis apparatus comprising irradiation means; sample holding means; incident X-ray adjustment means; and X-ray detection means. In this characteristic X-ray analyzer, the irradiating means irradiates a sample held by the sample holding means with an electron beam; the sample holding means can hold the analysis surfaces of two or more samples on the same plane. Yes, and it is possible to move the sample so that one sample is selectively irradiated with the electron beam from the irradiation means; the incident X-ray adjusting means is excited from the analysis surface of the sample by the electron beam The sample holding means or the X-ray detection means is moved or the sample holding means is tilted so that only characteristic X-rays are incident on the X-ray detection means; and the X-ray detection means detects the incident characteristic X-rays. To do.

A known electron gun can be used as the irradiation means. A focusing lens and an objective lens for focusing the electron beam may be provided in a path through which the electron beam passes until reaching the irradiation surface of the sample.
The electron beam is generally accelerated so as to have an energy of about 1 to 30 keV, and is focused to a diameter of about 40 nm to 300 nm on the analysis surface of the sample.

  The sample holding means can hold the analysis surfaces of two or more samples on the same plane. The analysis planes of the samples can be set on the same plane, for example, by bringing a part of the analysis plane of each sample (preferably, the peripheral part of the measurement region) into close contact with one reference plane. The analysis surface is brought into close contact with the reference surface by pressing the sample against the reference surface, and such a mechanism is known in the art. For example, the sample is pressed in the direction of the reference plane by a screw-type fixture or an elastic member. Since the analysis surface is in the same plane, it is possible to detect and analyze characteristic X-rays with almost the same oblique emission angle for all the samples held by simply moving the sample to the irradiation position on the sample holding means. Measurement becomes easy.

  The sample holding means can also move the sample so that one sample is selectively irradiated with the electron beam from the irradiation means. As the moving mechanism, a mechanism known in the art can be used. As an example, a mechanism (for example, a two-dimensional manipulator) that can be translated independently in two orthogonal directions can be cited.

  The sample holding means may not always have a mechanism for holding two or more samples with the analysis plane parallel and a moving mechanism. For example, the sample stage has a mechanism for holding two or more samples in parallel with the analysis surface, the sample stage has a mechanism for moving the sample stage, and the sample stage is detachable from the sample stage, It may be held on the sample stage during characteristic X-ray measurement, and may be removed from the sample stage when holding the sample.

  All of the two or more samples held in the sample holding means may be analysis samples or may include one or more standard samples. The analysis surfaces of two or more samples are preferably subjected to oblique etching or the same oblique polishing at the same angle θ by the same process.

  The X-ray detection means detects characteristic X-rays excited from the measurement layer of the sample. As the X-ray detection means, a known X-ray detector such as a wavelength dispersive X-ray spectrometer and an energy dispersive X-ray spectrometer can be used, and a wavelength dispersive X-ray spectrometer is preferable. The X-ray detection means may include an aperture limiting member to limit the incident angle of the characteristic X-ray to be detected / measured. The opening limiting member is known in the art, and is, for example, a member having a slit or an aperture (preferably a slit width or an aperture diameter of 0.5 mm or less). By using the aperture limiting member, the oblique emission angle of the characteristic X-ray to be detected / measured can be more easily limited.

  The incident X-ray adjusting means is any means capable of moving the sample holding means or the X-ray detection means or tilting the sample holding means. In order to move the sample holding means or the X-ray detection means, a known linear movement mechanism such as a stepping motor or a manipulator can be used as the incident X-ray adjustment means. When a manipulator is employed as the incident X-ray adjusting means, a three-dimensional manipulator may be used in combination with the moving mechanism of the sample holding means. In order to incline the sample holding means, the incident X-ray adjustment means uses a known mechanism that allows it to be rotated within a certain range (for example, ± 45 ° with respect to the horizontal) with respect to a predetermined axis. For example, a stepping motor is used.

  Since each element emits characteristic X-rays having specific energy by an electron beam, the energy spectrum of the characteristic X-rays from each measurement layer of the analysis sample detected by the X-ray detection means is expressed by each element or standard sample. The elemental composition of each layer can be determined by comparing / analyzing with that of the above. In addition, by comparing and analyzing the energy spectrum of the characteristic X-rays from each measurement layer of the analysis sample with the energy spectrum of the characteristic X-rays of the standard sample, whether or not each layer of the analysis sample has a desired elemental composition is determined. Easy to determine.

  According to the present invention, the elemental composition and distribution of each layer of the laminated structure can be easily analyzed with a relatively high accuracy. In particular, it is possible to analyze the elemental composition and distribution of compound semiconductors with a thin film stack structure with the accuracy required for design and quality control, and thereby design for yield management, improvement and higher performance in semiconductor device production. Is possible on an industrial scale.

  Hereinafter, the apparatus of the present invention will be described by referring to specific embodiments.

  One embodiment of the device of the present invention is shown in FIG. The apparatus of the present invention includes an electron gun 22, a sample stage 24, a stepping motor 26, and an X-ray counter 28.

  The electron gun 22 emits the electron beam 10 and irradiates the analysis surface of the sample 2 or 2 ′ held on the sample stage 50 on the sample stage 24. In a path through which the electron beam 10 passes between the electron gun 22 and the sample 2 or 2 ′, a focusing lens 30 and an objective lens 32 that focus the electron beam 10 are provided.

  The sample stage 50 is movable on the sample stage 24 so that the electron beams 10 from the electron gun 22 are selectively irradiated to the held samples 2 and 2 '.

The sample stage 50 (FIG. 3) has a reference plane member 52 that closely contacts the analysis surface of the sample. The reference plane member 52 has a number (two in this case) of rectangular incisions 54 corresponding to the number of samples that can be held. The analysis surface (periphery of the measurement region) of the sample is brought into close contact with the portion around the notch 54. The close contact surface around the cut 54 is precisely surface-treated so that the analysis surfaces of the samples 2 and 2 ′ that are in close contact with this surface exist in the same plane. Below the reference planar member 52, the planar member 56 is supported by the side wall 58. The flat member 56 is provided with a sample pressing mechanism 60, which closely contacts the analysis surface of the sample with the reference flat member.
When the sample stage 50 is mounted on the sample stage 34, the electron beam 10 is irradiated to the analysis surface of the sample through the cut 54. Among the characteristic X-rays that are stimulated and emitted from the irradiation area of the analysis surface, the characteristic X-rays emitted in the direction in which the flat member 52 that is in close contact does not exist (the direction of the arrow in FIG. 3) are detected and analyzed.

  The stepping motor 26 is controlled by the drive control unit 34 to rotate and tilt the sample stage 24 within a certain range.

  The X-ray counter 28 detects the incident characteristic X-ray. The X-ray counter 28 is electrically connected to the X-ray measurement unit 36, and the X-ray measurement unit 36 receives the signal from the X-ray counter 28 and measures X-rays. A slit 38 is placed in front of the X-ray counter 28. The X-ray measurement unit 36 and the drive control unit 34 are electrically connected to the X-ray measurement value determination / calculation unit 40.

  The electron beam 10 emitted from the electron gun 20 is focused and irradiated on the analysis surface of the sample 2 or 2 ′ by the focusing lens 30 and the objective lens 32. The electron beam 10 stimulates and emits characteristic X-rays from the irradiation site of the analysis layer of the sample 2 or 2 '. The position of the sample stage 24 is adjusted so that characteristic X-rays that are substantially stimulated and emitted only from the analysis layer pass through the slit 40 and enter the X-ray counter 28. That is, based on the characteristic X-ray energy spectrum measured by the X-ray measurement unit 36, the stepping motor 26 controlled by the drive control unit 34 rotates and tilts the sample stage 24. The X-ray counter 28 detects characteristic X-rays that are stimulated and emitted substantially only from the analysis layer of the sample 2 or 2 '. Characteristic X-rays detected by the X-ray counter 28 are measured by the X-ray measurement unit 36 and processed by the X-ray measurement value determination / calculation unit 40.

Example 1
By the method of the present invention, the composition of the laminated layer (1100 nm AlGaInP / 50 nm GaInP / 1100 nm AlGaInP / GaAs substrate) of the compound semiconductor device (GaAlInP-based light emitting element) is analyzed.

  The compound semiconductor device is processed by an Ar ion etching device (flat milling etching device) to expose the measurement layer (50 nm GaInP / 1100 nm AlGaInP). The Ar ion etching conditions are an Ar ion gun acceleration voltage of 1 kV, a current of 20 μA, and an angle (inclination angle θ) of 1 ° with respect to the surface of the compound semiconductor device. Standard samples (GaP, Al and InP individual samples) are processed in the same manner.

  For the analysis, the apparatus of the present invention shown in FIG. 2 is used. A wavelength dispersive X-ray spectrometer (WDS) was used for detection and analysis of characteristic X-rays. The treated compound semiconductor device and the standard sample are placed on the sample stage so that the analysis surface (that is, the exposed surface) is on the same surface. An electron beam is irradiated to the 50 nm GaInP layer. At this time, it is confirmed by a scanning electron microscope (SEM) image that the electron beam irradiation position is in the target GaInP layer. Next, the sample stage is tilted by driving the stepping motor while observing the peak of the characteristic X-ray measured by the X-ray detector. Even if the sample stage is further tilted, the characteristic X-ray profile measured by the X-ray detector is fixed at a position where it does not substantially change, and the characteristic X-ray is detected and analyzed by the X-ray counter. .

  Next, the sample stage is moved on the stage to irradiate the standard sample with an electron beam. Since the analysis surface of the sample is arranged in parallel with the analysis surface of the compound semiconductor device, desired characteristic X-rays are detected by the X-ray counter without changing the tilt of the stage. By comparing the peak intensity of the characteristic X-ray from the standard sample with the peak intensity of the characteristic X-ray from the analytical sample, the ratio of each element contained in the GaInP layer of the analytical sample can be obtained.

  Subsequently, the sample stage was moved on the sample stage so that the 1100 nm AlGaInP layer was irradiated with the electron beam. Also at this time, characteristic X-rays from a single layer can be detected without changing the inclination of the sample stage. The characteristic X-rays obtained from the AlGaInP layer are compared with the characteristic X-rays of the standard sample to determine the ratio of each element. As a result, it was confirmed that the GaInP layer had a predetermined elemental composition.

(Example 2)
The composition of the laminated layer (500 nm AlGaInP / 10 nm GaInP / 1100 nm AlGaInP / GaAs substrate) of the compound semiconductor device (GaAlInP-based light emitting element) is evaluated.

  500 nm AlGaInP / 10 nm GaInP has high resistance, causing charge-up even in the conventional EPMA measurement, and accurate quantification cannot be performed. Therefore, a 500 nm carbon film is formed on the surface of 500 nm AlGaInP by electron beam evaporation. Thereafter, the compound semiconductor device having the carbon thin film formed thereon is processed by an Ar ion etching apparatus (flat milling type etching apparatus) to expose the GaInP layer at an inclination angle of 0.1 °.

  As in Example 1, as a result of detecting and analyzing characteristic X-rays from the GaInP layer, it was confirmed that the GaInP layer had a predetermined elemental composition.

(Example 3)
The composition of the laminated layer (1100 nm AlGaInP / 50 nm GaInP / 1100 nm AlGaInP / GaAs substrate) of the compound semiconductor device (GaAlInP-based light emitting element) was evaluated.

  The sample GaInP layer was exposed at an angle of 1 ° by polishing. FIG. 4 shows a specific polishing apparatus and method. The polishing sample 2 was placed and fixed on the surface of the angle polishing jig 70 provided with a surface (sample mounting surface) 72 having an inclination of θ = 1 ° with respect to the reference surface. The angle polishing jig 70 was fixed to the guide ring 74 so that the reference surface of the angle polishing jig was parallel to the reference bottom surface of the guide ring. The sample was polished with the polishing paper 76 fixed on the wrapping disk until the reference bottom surface of the guide ring 74 was in close contact with the upper surface of the wrapping disk 78.

  In order to make the polished surface suitable for measurement, first, rough polishing is performed with 3 micron polishing paper (model number: RE-3; Sumitomo 3M), and then 0.3 micron polishing paper (model number: RE-03; Sumitomo). Final polishing was performed by 3M).

  After polishing, the characteristic X-rays from the GaInP layer were detected and analyzed in the same manner as in Example 1. As a result, it was confirmed that the GaInP layer had a predetermined elemental composition.

An overview of the method of the present invention is shown. The outline | summary of the apparatus of this invention is shown. The example of the sample stand which can be used for the apparatus of this invention is shown. (A) is a perspective view, (b) is a side sectional view, and (c) is a top view. Detect and measure characteristic X-rays emitted in the direction of the arrow. The polishing apparatus and polishing method used in Example 3 are shown. (A) shows an angle polishing jig and (b) shows a polishing state.

Explanation of symbols

θ Polishing angle α Characteristic X-ray emission angle d Measurement layer thickness a Measurement critical thickness β Surface irregularity m Measurable distance 2 Sample 4 Exposed surface 6 Measurement layer 8 Layer interface 10 Electron beam 20 Characteristic X-ray 22 Electron gun 24 Sample stage 26 Stepping motor 28 X-ray counter 30 Focusing lens 32 Objective lens 34 Drive control unit 36 X-ray measurement unit 38 Slit 40 X-ray measurement value determination / calculation unit 50 Sample stage 52 Reference plane member 54 Cut 56 Plane member 58 Side wall 60 Sample holding elastic member 70 Angle polishing jig 72 Sample mounting surface 74 Guide ring 76 Abrasive paper 78 Lapping disk

Claims (15)

Processing the analytical sample having a thin layered structure to expose the measurement layer obliquely with respect to the layer interface;
Exciting the characteristic X-rays from the exposed measurement layer by electron beam irradiation;
A method for analyzing a thin layer comprising a step of detecting only characteristic X-rays from a measurement layer; and a step of determining an elemental composition from the detected characteristic X-rays.   The thin layer analysis method according to claim 1, wherein the processing is etching or polishing.   The exposed surface of the exposed measurement layer is expressed by the formula d> a + b * sin θ (a: critical thickness of measurement, b: beam diameter of electron beam on the exposed surface, d: measurement layer) The thin-layer analysis method according to claim 1, wherein the thin-layer analysis method is a plane that forms an angle θ satisfying (layer thickness).   The exposed surface of the exposed measurement layer is expressed by the formula b <(da) / sin θ-β / tan θ (a: critical thickness of measurement, b: beam diameter of the electron beam on the exposed surface, d: of the measurement layer The thin layer analysis method according to claim 1, wherein the surface roughness β satisfies a layer thickness, θ: an angle formed by an exposed surface of the measurement layer and a layer interface.   The thin layer analysis method according to claim 2, wherein the etching is ion sputter etching.   The thin layer analysis method according to claim 5, wherein the ion sputter etching is argon sputter etching.   The thin layer analysis method according to claim 6, wherein the argon sputter etching is performed at an acceleration voltage of 0.5 to 2 kV.   The thin layer analysis method according to claim 1, further comprising a step of forming a thin film of a conductive substance other than the constituent elements of the analysis sample on the surface of the analysis sample before the exposing step.   The thin layer analysis method according to claim 8, wherein the conductive substance is carbon or metal.   The thin layer analysis method according to claim 9, wherein the conductive substance is gold or copper.   The thin layer analysis method according to claim 1, wherein the step of detecting characteristic X-rays is performed using an energy dispersive X-ray detector or a wavelength dispersive X-ray detector.   The thin layer analysis method according to claim 1, wherein the steps from exciting the characteristic X-ray to determining the elemental composition are repeated for another exposed layer.   The thin layer analysis method according to claim 1, wherein the step of determining the element composition from the step of exciting the characteristic X-ray is repeated for a standard sample simultaneously held in one holding means together with the analysis sample.   The thin layer analysis method according to claim 13, wherein the standard sample is subjected to the same exposure step as the analysis sample. Irradiation means; sample holding means; incident X-ray adjustment means; and X-ray detection means,
The irradiation means irradiates the sample held by the sample holding means with an electron beam;
The sample holding means can hold the analysis surfaces of two or more samples on the same plane, and move the sample so that the electron beam from the irradiation means is selectively irradiated to one sample. Is possible;
The incident X-ray adjusting means moves the sample holding means or the X-ray detection means so that only characteristic X-rays excited from the analysis surface of the sample by the electron beam enter the X-ray detection means, or the sample holding means And the X-ray detection means detects the incident characteristic X-ray,
Characteristic X-ray analyzer.

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