JP4498751B2 - Sample evaluation method and sample evaluation apparatus - Google Patents

Description

  The present invention relates to a sample evaluation method and a sample evaluation apparatus using electron beams or X-rays.

  As an apparatus for analyzing the concentration of an element contained in a sample in the sample, an electron probe microanalyzer (hereinafter referred to as EPMA) and a fluorescent X-ray analyzer are known. As an element concentration analysis method in a sample using such an apparatus, a concentration analysis method described in Japanese Patent Laid-Open No. 61-70444 (hereinafter referred to as Patent Document 1) is known. Hereinafter, the concentration analysis method described in Patent Document 1 will be described with reference to the drawings.

  In the concentration analysis method described in Patent Document 1, an analyzer having an EPMA configuration (referred to as an electron beam microanalyzer in Patent Document 1) is used. This analyzer is configured as shown in FIG. 3, and the electron beam 101 is irradiated in a state of being focused on the surface of the sample 102 by an objective lens (condenser lens) (not shown). The sample 102 is placed on a sample stage (not shown). Then, the sample 102 is two-dimensionally scanned by the electron beam 101 by the movement of the sample stage. Note that by stopping the movement of the sample stage and fixing the position of the sample 102 as appropriate, spot irradiation can be performed in a state where the electron beam 101 is fixed at a predetermined position on the sample 102.

  When the electron beam 101 irradiates the sample 102, a characteristic X-ray 104 is generated from an analysis point on the irradiated sample 102, and the characteristic X-ray 104 is spectrally separated by the spectral crystal 103. The characteristic X-ray 104 dispersed by the spectral crystal 103 is detected by the X-ray detector 105.

  The X-ray detector 105 outputs an electrical signal (pulse signal) corresponding to the detected characteristic X-ray intensity of the characteristic X-ray 105. The electric signal is counted as a characteristic X-ray intensity by the X-ray measurement circuit 106 and stored in a storage area corresponding to each analysis point on the sample 102 in the storage device 108 via the arithmetic control device 107. Thereby, the element concentration of each analysis point on the sample 102 can be obtained.

  A display device 109 is connected to the arithmetic and control unit 107, and a concentration map representing the element concentration at each analysis point on the sample 102 is displayed on the display device 109.

  By using such an analyzer, the concentration of elements contained in the sample at a plurality of locations on the sample can be obtained.

  By the way, recently, using the analyzer as described above, after obtaining the element concentration data of a plurality of analysis points on the sample as described above, it was contained in the sample based on the element concentration data. Evaluating the in-plane homogeneity of the sample for elements is under consideration.

JP-A-61-70444

  As described above, it has been studied to evaluate the in-plane homogeneity of an element contained in a sample by using an analyzer such as EPMA. A method that can be performed with reliability has not been established.

  The present invention has been made in view of the above points, and a sample evaluation method and a sample capable of performing in-plane homogeneity evaluation of the element contained in the sample with high reliability. An object is to provide an evaluation device.

The sample evaluation method according to the present invention irradiates a plurality of locations of a sample with an electron beam or X-ray, detects characteristic X-rays generated corresponding to the elements contained in the sample, and thereby the characteristics X at the plurality of locations. A sample evaluation method for obtaining the line intensity and evaluating the in-plane uniformity of the sample for the element , where ε = 1 when the average of the obtained characteristic X-ray intensities Ii is Iave It is characterized in that the homogeneity of the sample is evaluated by comparing a standard deviation σ with a value kε obtained by multiplying a coefficient ε defined by / (√Iave) and a correction coefficient k .

Moreover, the sample evaluation apparatus based on this invention irradiates the electron beam or X-ray to several places of a sample, detects the characteristic X-ray generated according to the element contained in the sample, and, thereby, in the said several places A sample evaluation apparatus that obtains characteristic X-ray intensity and evaluates in-plane homogeneity of the element for the element, and when the average of the obtained plurality of characteristic X-ray intensities Ii is Iave , ε =, characterized in that to evaluate the homogeneity of the sample by comparing 1 / a is the coefficient value kε and the standard deviation multiplied by the correction coefficient k epsilon sigma defined (√Iave).

In the present invention, the homogeneity of the sample is evaluated by comparing a standard deviation σ with a value kε obtained by multiplying a coefficient ε defined by ε = 1 / (√Iave) and a correction coefficient k .

  Accordingly, the homogeneity of the sample is evaluated in consideration of the variation and distribution of the characteristic X-ray intensity, and the sample can be evaluated with high reliability.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an example of a sample evaluation apparatus based on the present invention. This sample evaluation apparatus has an EPMA configuration.

  In the figure, reference numeral 1 denotes an electron gun, from which an electron beam 6 is accelerated and emitted. The electron beam 6 emitted from the electron gun 1 is finely focused on the sample 7 by the focusing lens 2 and the objective lens 4. Thereby, the electron beam 6 becomes an electron probe on the sample 7. At this time, the electron beam 6 is appropriately deflected by the scanning coil 3. Thereby, the electron beam 6 can scan a predetermined area on the sample 7 as an analysis area, or can also perform spot irradiation with one point on the sample 7 fixed as an analysis point.

  From the sample 7 irradiated with the electron beam 6, characteristic X-rays 8 are generated corresponding to the elements contained in the sample 7. The characteristic X-ray 8 is dispersed by the spectral crystal 9, and the characteristic X-ray 8 after the spectroscopy is detected by the X-ray detector 11.

  The X-ray detector 11 outputs a detection signal (pulse signal) corresponding to the detected characteristic X-ray intensity of the characteristic X-ray 8. The detection signal from the X-ray detector 11 is counted in the processing unit 17 and the counted data is sent to the arithmetic control unit 18 as the characteristic X-ray intensity.

  The electron gun 1, the focusing lens 2, the scanning coil 3, and the objective lens 4 are disposed in a lens barrel 12 constituting a sample evaluation apparatus. The sample 7 is placed on the sample stage mechanism 5 disposed in the sample chamber 13 located below the lens barrel 12.

  The interior of the lens barrel 12 and the sample chamber 13 are evacuated and evacuated by an evacuation unit (not shown). When the sample 7 is irradiated with the electron beam 6, the inside of the lens barrel 12 and the sample chamber 13 are each evacuated to a predetermined degree of vacuum.

  An electron optical system 23 is configured by the focusing lens 2, the scanning coil 3, and the objective lens 4 in the lens barrel 12. The electron gun 1 and the electron optical system 23 are driven by the drive unit 14.

  The spectroscopic crystal 9 and the X-ray detector 11 are attached to the drive mechanism 10. The spectroscopic crystal 9 and the X-ray detector 11 are each moved in a predetermined direction by the drive mechanism 10. The drive mechanism 10 is driven by the drive unit 15.

  The sample stage mechanism 5 on which the sample 7 is placed is driven by the drive unit 16. As a result, the sample 7 moves in the horizontal direction, the vertical direction, the tilt direction, and the rotation direction.

  The drive units 14 to 16 and the processing unit 17 are connected to the calculation control unit 18. Further, a storage unit 19 is connected to the arithmetic control unit 18. These drive units 14 to 16, the processing unit 17, the calculation control unit 18, and the storage unit 19 constitute a control system 20.

  Here, the calculation control unit 18 controls each component of the sample evaluation apparatus and performs calculations necessary for executing the control. In addition, the storage unit 19 stores the irradiation conditions of the electron beam 6 required when executing the sample evaluation, the sample evaluation conditions including the measurement time described later, and the like.

  A display unit 21 and an input unit 22 are connected to the arithmetic control unit 18. The display unit 21 includes a display device such as an LCD or a CRT, and displays the sample evaluation conditions read from the storage unit 19, the sample evaluation result after the sample evaluation, and the like as necessary. The input unit 22 includes a pointing device such as a mouse and a joystick, a keyboard, and the like. An operator who evaluates the sample 7 using the sample evaluation apparatus can set the sample evaluation conditions by operating the input unit 22.

  The above is the configuration of the sample evaluation apparatus in the present invention. Next, the sample evaluation method in the present invention will be described. Here, a sample that is an alloy of Ni (nickel) and Fe (iron) and has a composition ratio of Ni = 60% and Fe = 40% is taken as an example.

First, before performing sample evaluation on a sample to be actually evaluated, the sample evaluation conditions for executing the sample evaluation are obtained by the following method.
A reference sample in which it is known in advance that the variation ratio of the concentration distribution in a plane for a predetermined element is within a desired value (for example, 0.1%) is stored in the sample chamber 13 of the sample evaluation apparatus. The sample stage mechanism 5 is mounted. In this embodiment, when the predetermined element is Ni, the reference sample is an alloy of Ni (60%) and Fe (40%), and the concentration distribution variation in the plane of Ni The ratio is 0.1% or less. When the ratio of variation in the concentration distribution in the sample surface is small, it is evaluated that the uniformity in the sample surface is high. Therefore, the evaluation of the homogeneity within the surface of the sample is determined according to the ratio of the variation in the concentration distribution.

  After placing such a reference sample on the sample stage mechanism 5 in the sample chamber 13, the electron beam 6 is used as a reference sample under irradiation conditions of initial setting sample evaluation conditions stored in advance in the storage unit 19. Irradiate. At this time, by controlling the driving mechanism 10, the positions of the spectral crystal 9 and the X-ray detector 11 are set so that the Ni characteristic X-ray 8 can be detected.

  Then, the position of the electron beam 6 is fixed to be in a spot irradiation state, the sample stage mechanism 5 is controlled, and the reference sample is moved stepwise in the horizontal direction (XY direction). That is, the reference sample is repeatedly moved by a predetermined distance L (see FIG. 2 described later) and stopped. Thereby, the characteristic X-ray 8 generated from the analysis point on the reference sample irradiated with the electron beam 6 when the reference sample is stopped is detected by the X-ray detector 11 through the spectral crystal 9. be able to. At this time, the time during which the reference sample is stopped while the electron beam 6 is irradiated to the reference sample corresponds to the measurement time for concentration analysis at the analysis point. The measurement time of the initially set sample evaluation condition stored in advance in the storage unit 19 is also applied to this measurement time.

  Here, an example of the analysis point irradiated with the electron beam 6 on the reference sample will be described with reference to FIG. In the figure, reference numeral 7a denotes a reference sample, and a plurality of analysis points Pi are set at a predetermined interval (distance) L on the upper surface 7b of the reference sample 7a. In this example, 5 analysis points Pi in the vertical direction * 5 horizontal directions = 25 analysis points are set. Then, the electron beam 6 irradiates the upper surface 7b of the reference sample 7a in a direction from top to bottom with respect to the paper surface of FIG.

  At this time, the position of the electron beam 6 is fixed as described above, and initially, the electron beam 6 is applied to the analysis point P1 on the upper surface 7b of the reference sample 7a. Then, after the measurement time has elapsed, the reference sample 7a moves stepwise. Thereby, the irradiation position of the electron beam 6 on the upper surface 7b of the reference sample 7a moves from the analysis point P1 to the analysis point P2, and the movement of the reference sample 7a stops, so that the electron beam 6 moves to the analysis point P2. Irradiate spot position. Further, after the measurement time has elapsed, the reference sample 7a moves again and stops, so that the electron beam 6 spot-irradiates the analysis point P3.

  Thereafter, by repeating such an operation by step movement of the reference sample 7a, the electron beam 6 sequentially irradiates each analysis point Pi (P1 to P25) on the upper surface 7b of the reference sample 7a. As a result, the characteristic X-rays 8 of Ni generated from each analysis point Pi can be detected by the X-ray detector 11.

  The X-ray detector 11 outputs a detection signal corresponding to the characteristic X-ray intensity of the detected characteristic X-ray 8 of Ni. The detection signal is counted in the processing unit 17, and the counted data is sent to the calculation control unit 18 as characteristic X-ray intensity. As a result, the characteristic X-ray intensity of Ni corresponding to each analysis point Pi is sent to the arithmetic control unit 18.

  Next, the calculation executed in the calculation processing unit 18 with the characteristic X-ray intensity corresponding to each analysis point Pi as Ii will be described.

First, an average I _ave of the characteristic X-ray intensity Ii is calculated. This average I _ave is defined by the following equation.

ここで、ｎは分析点の総数であり、本実施例においては、ｎ＝２５となる。

Here, n is the total number of analysis points, and in this embodiment, n = 25.

  Next, a variation coefficient ε relating to the variation in the characteristic X-ray intensity Ii is calculated. This variation coefficient ε is defined by the following equation.

また、特性Ｘ線強度Ｉｉの分布に関する標準偏差σを算出する。この標準偏差σは、次式により定義される。

Also, the standard deviation σ relating to the distribution of the characteristic X-ray intensity Ii is calculated. This standard deviation σ is defined by the following equation.

そして、変動係数εと標準偏差σとの比較を行う。このとき、当該変動係数εに補正係数ｋを掛け合わせた値であるｋεと当該標準偏差σとの大小関係を判断する。

Then, the coefficient of variation ε and the standard deviation σ are compared. At this time, the magnitude relation between kε, which is a value obtained by multiplying the variation coefficient ε by the correction coefficient k, and the standard deviation σ is determined.

That is,
It is determined whether σ <kε (1) or σ ≧ kε (2).

  In addition, as a setting range of the said correction coefficient k, the range of 3-5 is preferable.

  Here, if the above equation (1) holds, the standard deviation σ relating to the distribution of the characteristic X-ray intensity Ii becomes smaller than a constant multiple (k times) of the variation coefficient ε relating to the variation in the characteristic X-ray intensity. Will be.

  Therefore, in this case, if the initially set sample evaluation conditions applied at this time are used, the sample evaluation for the sample to be actually evaluated, which is performed thereafter, is performed with the desired value (the ratio of variation in the concentration distribution is 0. 0). 1%) as an evaluation criterion. In this case, the initially set sample evaluation condition is stored in the storage unit 19 as the sample evaluation condition.

  Further, when the above equation (2) is established, the irradiation condition or measurement time of the electron beam 6 is changed, and similarly to the above, the analysis process by the step movement of the reference sample 7a is performed again, and the above A sample evaluation condition that satisfies the formula (1) is obtained. The sample evaluation conditions thus obtained are stored in the storage unit 19.

  After the sample evaluation conditions are obtained and stored in the storage unit 19 as described above, the reference sample 7a is taken out from the sample chamber 13.

  The above is the method for obtaining the sample evaluation conditions for executing the sample evaluation for the sample to be evaluated. Next, a sample evaluation method for a sample to be evaluated will be described.

  First, the sample 7 to be evaluated is placed on the sample stage mechanism 5 in the sample chamber 13. Here, the sample 7 is an alloy of Ni (60%) and Fe (40%). Here, it is assumed that whether or not the ratio of variation in the concentration distribution in the surface of Ni in the sample 7 is 0.1% or less is evaluated.

  After placing the sample 7 on the sample stage mechanism 5 in the sample chamber 13, the sample 7 is irradiated with the electron beam 6 under the sample evaluation conditions stored in the storage unit 19. At this time, by controlling the drive mechanism 10, the positions of the spectroscopic crystal 9 and the X-ray detector 11 are set so that the characteristic X-rays of Ni can be detected.

  Then, the position of the electron beam 6 is fixed to be in a spot irradiation state, the sample stage mechanism 5 is controlled, and the sample 7 is moved stepwise in the horizontal direction (XY direction) as described above. Thereby, the characteristic X-ray 8 generated from the analysis point on the sample 7 irradiated with the electron beam 6 when the sample 7 is stopped can be detected by the X-ray detector 11 via the spectral crystal 9. it can. In addition, the sample evaluation conditions memorize | stored in the memory | storage part 19 are applied to the measurement time at this time.

  Here, for example, the above-described example shown in FIG. 2 is applied to the analysis point irradiated with the electron beam on the sample 7. However, the present invention is not limited to this, and the position and number of analysis points on the sample 7 are not limited thereto. It is safe to change the Hereinafter, in order to simplify the description, description will be made based on the example shown in FIG.

  The step movement of the sample 7 in FIG. 2 causes the electron beam 6 to sequentially irradiate each analysis point Pi (P1 to P25) on the upper surface 7b of the sample 7. As a result, the characteristic X-rays 8 of Ni generated from each analysis point Pi can be detected by the X-ray detector 11.

  The X-ray detector 11 outputs a detection signal corresponding to the characteristic X-ray intensity of the detected characteristic X-ray 8 of Ni. The detection signal is counted in the processing unit, and the count data is sent to the arithmetic control unit 18 as characteristic X-ray intensity. As a result, the characteristic X-ray intensity of Ni corresponding to each analysis point Pi on the upper surface 7 b of the sample 7 is sent to the arithmetic control unit 18.

  Thereafter, for the characteristic X-ray intensity corresponding to each analysis point Pi, the same calculation as described above is executed in the calculation processing unit 18.

That is, first, an average I _ave of the characteristic X-ray intensity Ii is calculated. Next, a variation coefficient ε related to the variation in the characteristic X-ray intensity Ii is calculated. Then, the standard deviation σ relating to the distribution of the characteristic X-ray intensity Ii is calculated. Here, the average I _ave , the variation coefficient ε, and the standard deviation σ are defined as described above.

  Thereafter, the coefficient of variation ε and the standard deviation σ are compared. At this time, as described above, the magnitude relationship between kε, which is a value obtained by multiplying the variation coefficient ε by the correction coefficient k, and the standard deviation σ is determined. Again, it is determined whether the above formula (1) or the above formula (2) is established.

  When the above equation (1) is established, it is evaluated that the variation ratio of the concentration distribution in the surface of Ni of the sample 7 is within a desired value. Therefore, in this case, it is evaluated that the sample 7 has a desired homogeneity.

  When the above equation (2) is established, it is evaluated that the variation ratio of the concentration distribution in the surface of Ni of the sample 7 is not within a desired value. Therefore, in this case, it is evaluated that the sample 7 does not have the desired homogeneity.

  As described above, in the present invention, the homogeneity of the sample is evaluated based on the variation coefficient ε and the standard deviation σ relating to the obtained variation in the plurality of characteristic X-ray intensities.

  Accordingly, the homogeneity of the sample is evaluated in consideration of the variation and distribution of the characteristic X-ray intensity, and the sample can be evaluated with high reliability.

  In the above example, the sample 7 and the reference sample 7a have been described as samples made of an alloy of Ni (60%) and Fe (40%). However, the present invention is not limited to this, and other compositions are used. Even a sample made of an alloy or the like can be applied.

  In the above-described embodiments, the sample evaluation apparatus has been described using an example of an apparatus having an EPMA configuration, but is not limited to EPMA. As another example, the sample is irradiated with X-rays (primary X-rays), thereby detecting characteristic X-rays (fluorescent X-rays) generated corresponding to the elements contained in the sample. The present invention can also be applied to an apparatus.

It is a schematic block diagram which shows the example of the sample evaluation apparatus based on this invention. It is a top view which shows the analysis point in the upper surface of a sample (reference sample). It is a schematic block diagram of the analyzer which has the structure of EPMA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Focusing lens, 3 ... Scanning coil, 4 ... Objective lens, 5 ... Sample stage mechanism, 6 ... Electron beam, 7 ... Sample, 8 ... Characteristic X-ray, 9 ... Spectral crystal, 10 ... Drive mechanism , 11 ... X-ray detector, 17 ... processing unit, 18 ... calculation control unit, 19 ... storage unit

Claims (4)

Irradiating electron beams or X-rays to a plurality of locations on a sample, detecting characteristic X-rays generated corresponding to the elements contained in the sample, thereby obtaining characteristic X-ray intensities at the plurality of locations, Is a sample evaluation method for evaluating the in-plane homogeneity of a sample, and is defined by ε = 1 / (√Iave) where an average of a plurality of obtained characteristic X-ray intensities Ii is Iave A sample evaluation method characterized by evaluating the homogeneity of a sample by comparing a value kε obtained by multiplying a coefficient ε by a correction coefficient k with a standard deviation σ. The correction coefficient k is a sample evaluation method according to claim 1, wherein the set in the range of 3-5. Electron beam or X-ray is irradiated to a plurality of locations on the sample, and characteristic X-rays generated corresponding to the elements contained in the sample are detected, thereby obtaining the characteristic X-ray intensity at the plurality of locations, Is a sample evaluation apparatus for evaluating the in-plane homogeneity of a sample, and is defined by ε = 1 / (√Iave) where an average of a plurality of obtained characteristic X-ray intensities Ii is Iave A sample evaluation apparatus for evaluating the homogeneity of a sample by comparing a value kε obtained by multiplying a coefficient ε by a correction coefficient k with a standard deviation σ. The sample evaluation apparatus according to claim 3 , wherein the correction coefficient k is set in a range of 3 to 5.

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