JP2008057977A - Film analysis method and device by fluorescent x-ray analysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for determining quickly whether an analysis object element is included in either or both of a film and a substrate, in trace constituent inspection or the like of a plating film. <P>SOLUTION: When the film thickness is known, n and m corresponding to the film thickness are determined by a relational expression on the film and the substrate, by using the relational expression showing a relation wherein an intensity ratio n (=Bp/Ap) between two kinds of characteristic X-ray peak intensity measured values generated from the analysis object element included only in the film and an intensity ratio m (=Bb/Ab) of two kinds of characteristic X-ray peak intensity measured values generated from the analysis object element included only in the substrate are changed according to the film thickness of the film, and A and B are determined respectively by being separated into estimated values (Ab, Bb) of measured intensity caused by the substrate and estimated values (Ap, Bp) of measured intensity caused by the film from n and m, and the two kinds of characteristic X-ray peak intensity measured values A (=Ap+Ab) and B (=Bb+Bp). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a film formed on a base and a method for quantitative analysis of trace elements contained in the base using a fluorescent X-ray analyzer.

The X-ray fluorescence analysis method is widely used for material development, product inspection, and the like as an analysis method that can accurately perform quantitative analysis of trace elements at the ppm level. It is also known as a method for easily performing film thickness such as a plating film. For example, in Japanese Patent Application Laid-Open No. 10-221047 of Patent Document 1, a standard sample having a known composition ratio is placed on the back side of a thin film to be measured, and the magnitude of absorption received by the thin film to be measured by fluorescent X-rays generated from the standard sample. Discloses a technique for obtaining the thickness of a thin film to be measured. Further, Japanese Patent Application Laid-Open No. 58-50412 of Patent Document 2 includes a metal film thickness or a metal film based on fluorescent X-ray intensity data obtained by irradiating n types of radiations having different energies. A method for simultaneously determining the contents of n kinds of elements is disclosed.

Japanese Patent Laid-Open No. 10-221047 JP-A-58-50412

  In recent years, environmental regulations (for example, the “RoHS Directive in Europe”) prohibiting the inclusion of a certain amount or more of harmful elements such as lead and cadmium in the plating film have been strengthened. For this reason, there is an increasing need to accurately analyze the contents of these harmful metals in the plating film. FIG. 8 is a diagram schematically showing an example of analyzing lead (hereinafter, may be represented by the element symbol “Pb”) as an analysis target element contained in a plating sample using a fluorescent X-ray analyzer. . In FIG. 8A, since the primary X-ray irradiated to the sample from the X-ray source passes through the plating layer and reaches the base, characteristic X-rays of lead generated from both the plating layer and the base (fluorescent X-rays) ) Is detected by the X-ray detector. The detected X-ray is displayed as a spectrum as shown in FIG. In addition to the Pb-Lα and Pb-Lβ shown in FIG. 8B, there are many Pb-Lγ rays in the characteristic X-rays of lead. Compared to other characteristic X-ray peaks for easy understanding. Only two types of characteristic X-rays with high intensity are shown.

  However, when a characteristic X-ray peak of lead as shown in FIG. 8B is obtained, it is not possible to distinguish whether the characteristic X-ray has the same energy or not from the coating or the base by the conventional analysis method. Therefore, it was not possible to determine whether the analysis target element was contained in the plating film, contained in the underlayer, or contained in both. It is extremely important for quality control to quickly know how much of a sample contains harmful elements such as lead and cadmium. In addition, with the conventional analysis method, accurate analysis is possible for small samples that do not have enough area to irradiate primary X-rays, or for samples where it is difficult to set the analysis height to the normal position, such as lead wires and round bars. There is also the problem that it is difficult.

  An object of the present invention is to provide a method for quickly discriminating whether an analysis target element is included in either or both of a film and a base in a trace component inspection of a plating film.

In order to solve the above problem, the invention of claim 1
A fluorescent X-ray analysis method that irradiates a sample with X-rays and performs elemental analysis using secondary X-rays generated from the sample,
In the analysis of the sample to be analyzed with a film formed on the ground,
Intensity ratio of two kinds of characteristic X-ray peak intensity measurement values generated from the analysis target element contained only in the coating and two kinds of characteristic X-ray peak intensity measurement values generated from the analysis target element contained only in the base In advance, a relationship in which the intensity ratio changes according to the film thickness of the coating,
When the thickness of the coating film of the sample to be analyzed is known, the intensity ratio of the two kinds of characteristic X-ray peak intensity measurement values corresponding to the thickness of the coating film of the sample to be analyzed is determined based on the relationship Obtaining the two types of characteristic X-ray peak intensity measured values from the ground based on the intensity ratio obtained based on the relationship and the two types of characteristic X-ray peak intensity measured values of the sample to be analyzed It is characterized by separately obtaining an estimated value of measured intensity and an estimated value of measured intensity caused by the coating.
Further, in the invention according to claim 2, when the analysis target element is lead, the two kinds of characteristic X-ray peaks are a combination of Pb-Lα and Pb-Lβ, a combination of Pb-Kα and Pb-Kβ, or Pb. -Mα and any combination of Pb-Mβ.
The invention according to claim 3 is characterized in that the coating is nickel plating.
According to a fourth aspect of the present invention, there is provided a base and / or coating film based on X-ray intensities obtained separately from the estimated value of the measured intensity caused by the base and the estimated value of the measured intensity caused by the coating, respectively. It is characterized in that the content of the element for analysis in each is determined separately.
The invention according to claim 5 is a fluorescent X-ray analysis method in which a sample is irradiated with X-rays and elemental analysis is performed using secondary X-rays generated from the sample,
In the analysis of the sample to be analyzed with a film formed on the ground,
Intensity ratio of two kinds of characteristic X-ray peak intensity measurements generated from the analytical element contained only in the coating and / or two characteristic X-ray peak intensities generated from the analytical element contained only in the base In advance, a relationship representing a relationship in which the intensity ratio of the measured values changes according to the thickness of the coating is obtained,
When it is known that the target element for analysis is contained in only one of the film or the base of the sample to be analyzed, the two kinds of characteristic X-ray peak intensity measurement values generated from the film or the base of the sample to be analyzed The film thickness of the coating corresponding to the intensity ratio is obtained from the relationship.
The invention described in claim 6 is an X-ray fluorescence analyzer that irradiates a sample with X-rays and performs elemental analysis using secondary X-rays generated from the sample,
From the intensity ratio of two kinds of characteristic X-ray peak intensity measurements generated from the analysis target element contained only in the coating film of the sample having the coating formed on the ground and / or from the analysis objective element contained only in the groundwork Storage means for storing data representing a relationship in which the intensity ratio of two kinds of generated characteristic X-ray peak intensity measurement values varies depending on the film thickness of the coating;
When the film thickness of the sample to be analyzed with the film formed on the ground is known, the intensity ratio of the two types of characteristic X-ray peak intensity measurement values corresponding to the film thickness of the film of the sample to be analyzed is determined as the film and Using the data stored in the storage means for the ground, the intensity ratio determined using the data and the two types of characteristic X-ray peak intensity measurement values for the sample to be analyzed, the two types The characteristic X-ray peak intensity measurement value is calculated by separately calculating an estimated value of the measured intensity caused by the ground and an estimated value of the measured intensity caused by the coating, respectively.

  According to the first aspect of the present invention, the measured intensity of the characteristic X-ray peak generated from the analysis target element contained in the sample to be analyzed is the estimated value of the measured intensity caused by the ground and the estimated value of the measured intensity caused by the coating. Therefore, it is possible to know whether the element to be analyzed exists in the base or in the coating. In addition, even when both the base and the coating are included, the measured intensity of characteristic X-rays generated from each can be quantitatively known. In addition, by using the measured intensity ratio of characteristic X-rays, it is difficult to set the analysis height at a normal position, such as a shortage of the primary X-ray irradiation area or lead wires or round bars. A decrease in analysis accuracy due to the shape can be avoided.

  According to the invention described in claim 2, when the analysis target element is lead, it is possible to know whether lead is present in the base or in the coating. Also, when lead is contained in both the base and the coating, each can be separated and analyzed.

  According to the third aspect of the present invention, it is possible to know whether the analysis target element is present in the base or in the nickel plating when the sample is a nickel plating sample. Further, even when both the base and nickel plating are included, each can be separated and analyzed.

  According to the invention described in claim 4, the contents of the element for analysis in the base and the coating can be obtained separately.

  Further, according to the invention described in claim 5, even when the film thickness of the analysis target sample is unknown, it is known whether the analysis target element is included only in the coating of the analysis target sample or only in the ground. Then, the film thickness can be obtained.

  According to the sixth aspect of the present invention, the measured intensity of the characteristic X-ray peak generated from the analysis target element contained in the sample to be analyzed is the estimated value of the measured intensity caused by the base and the estimated intensity of the measured intensity caused by the coating. It is possible to provide an X-ray fluorescence analyzer equipped with means that can be obtained separately for each value.

  Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not limited by this illustration.

  FIG. 5 is a diagram showing a schematic configuration example of an X-ray fluorescence analyzer for carrying out the present invention. In FIG. 5, the sample 1 has a plating layer 1a formed on a base 1b. The sample 1 is irradiated with primary X-rays from the X-ray source 2, and the fluorescent X-rays generated from the sample 1 are detected by the X-ray detector 4. A primary X-ray filter 7 and a collimator 9 are disposed between the X-ray source 2 and the sample, and a collimator 10 is disposed between the sample 1 and the X-ray detector 4. A generator power supply 3 for generating X-rays from the X-ray source and a filter control system 8 for controlling the primary X-ray filter are connected to the control system 6. A detection signal from the X-ray detector 4 is sent to the control system 6 via the X-ray counting system 5. The control system 6 is provided with calculation means 11 for performing various calculations necessary for carrying out the present invention, and storage means 12 for storing data such as relationships necessary for carrying out the present invention. Is connected.

  FIG. 1 is a schematic diagram for explaining the basic concept of the present invention. FIGS. 1A and 1B show the spectrum of two types of characteristic X-rays (Pb-Lα and Pb-Lβ) of lead when lead (analysis target element) is not included in the base and only the plating layer is included. It is a figure which shows a method. When two types of characteristic X-rays of lead are generated only from the plating layer, the rate at which the intensity ratio between the Lα line and the Lβ line changes according to the change in the plating thickness is not so large. However, since the Lβ line has a higher energy than the Lα line and has less self-absorption, the Lβ / Lα intensity ratio should increase as the plating thickness increases. The graph of FIG. 3 is a relationship created by measuring changes in the measured intensity ratio (Lβ / Lα) of characteristic X-rays of lead from the plating layer to the plating thickness using several plating samples having different film thicknesses. . As the plating thickness increases, the Lβ / Lα intensity ratio gradually increases so as to approach the measured intensity ratio in the case of infinite thickness.

  Here, when the base component and the plating component are the same as the sample that created the graph of FIG. 3, if it is known that only the plating layer of the sample to be analyzed contains lead and not the base, FIG. 3 shows that the thickness of the plating layer can be obtained only by measuring the measured intensity ratio (Lβ / Lα) of the characteristic X-ray of lead.

  Next, the case where the plating layer does not contain lead but is contained only in the base will be described. (C) and (d) of FIG. 1 are diagrams showing a state where spectra of two types of characteristic X-rays of lead (Pb-Lα and Pb-Lβ) are obtained when the plating layer does not contain lead but is contained only in the base. is there. The characteristic of lead generated only from the base The influence of self-absorption by the base of X-rays is not so great, but since it is absorbed by the plating layer that does not contain lead, the proportion of absorbed Lα and Lβ rays increases as the plating thickness increases. change. The graph of FIG. 4 is a relationship created by measuring changes in the measured intensity ratio (Lβ / Lα) of characteristic X-rays of lead from the base to the plating thickness using several plating samples having different film thicknesses. The film is normalized so that the intensity ratio is 1 when the film thickness is zero. It can be seen that the Lβ / Lα intensity ratio increases rapidly as the plating thickness increases.

  Here, if the base component and the plating component are the same as the sample that created the graph of FIG. 4, if it is known that only the base of the sample to be analyzed contains lead and not the plating layer, FIG. 4 shows that the film thickness of the plating layer can be obtained by simply measuring the measured intensity ratio (Lβ / Lα) of the characteristic X-ray of lead.

  The data shown in FIG. 3 and FIG. 4 are stored in the storage unit 12 of FIG. 1, and are called up by the calculation unit as necessary and used for various calculations. When used for actual calculation, the relationship between the plating thickness and the strength ratio may be expressed by an approximate expression suitable for each graph.

  In the above description, the graphs in FIGS. 3 and 4 show examples in which the relationship between the plating thickness and the measured intensity ratio of characteristic X-rays is obtained by actual measurement. However, if the composition of the plating layer and the base and analysis conditions are determined. This relationship can also be obtained by theoretical calculation.

  Next, a case where lead is contained in both the plating layer and the base as shown in FIGS. When lead is contained in both the plating layer and the base, a spectrum in which (b) and (d) are superimposed is obtained. In addition, the absorption which the Lα ray and the Lβ ray generated from the base receive in the plating layer is slightly different between the case where the plating layer contains lead and the case where the plating layer does not contain lead at all. The difference is almost negligible.

The measured intensity and measured intensity ratio (Lβ / Lα) of Pb-Lα and Pb-Lβ shown in FIG. 1 (f) are the characteristic X-ray strength of the lead generated from the plating layer and the base and the thickness of the plating layer. Varies depending on Therefore, as shown in FIG. 2, the estimated values of the measured intensities of the Lα and Lβ rays generated only from the plating layer are Ap and Bp, respectively, and the estimated values of the measured intensities of the Lα and Lβ rays generated only from the ground are respectively Ab. And Bb, and the measured intensities of the actually observed Lα and Lβ rays as A and B,
A = Ap + Ab
B = Bp + Bb
It is.
Further, if the measurement intensity ratio between the Lα line and the Lβ line generated only from the plating layer is n, and the measurement intensity ratio between the Lα line and the Lβ line generated only from the ground is m,
n = Bp / Ap
m = Bb / Ab
It is.

Here, when the base component and the plating component are the same as the sample that created the graphs of FIGS. 3 and 4, if the thickness of the plating layer is given, n and m can be obtained from the relationship of FIGS. 3 and 4, respectively. it can. Further, since A and B are values obtained by measurement, the above four equations relating to A, B, n, and m can be solved as simultaneous equations of Ap, Bp, Ab, and Bb. That is,
Ap = (B−m × A) / (nm)
Bp = n × (B−m × A) / (n−m)
Ab = (B−n × A) / (mn)
Bb = m × (B−n × A) / (mn)
Is obtained.

  As described above, if the film thickness of the plating layer is known, the measured intensities (A, B) from the sample that can be actually measured are estimated values of the measured intensities of the Lα and Lβ rays generated only from the plating layer. (Ap, Bp) and the estimated values (Ab, Bb) of the measured intensities of the Lα and Lβ rays generated only from the ground.

Conversion from the X-ray intensity of lead obtained by separation to the concentration of lead contained in the plating layer is based on calibration curves created using a plurality of standard samples that contain lead only in the plating layer and not in the ground. You can use it. However, the thickness of the plating layer of the standard sample on which the calibration curve is created is not necessarily the same as the thickness of the plating layer of the analysis target sample. Therefore, it is necessary to convert the X-ray intensity obtained from the film thickness of the sample to be analyzed into an X-ray intensity corresponding to the film thickness of the standard sample for which the calibration curve has been created. For this conversion, the relationship between the plating thickness and the infinite thickness ratio of the X-ray intensity as shown in FIG. 6 is used.
FIG. 6 is a graph showing the relationship between the measured strength of Pb-Lα generated from the nickel plating layer and the plating thickness. For example, when the plating thickness of the sample to be analyzed is 3 μm (3.42 mg / cm ² ) and the plating thickness of the standard sample for which the calibration curve is prepared is 5 μm (5.7 mg / cm ² ), the infinite thickness ratio of Pb intensity Are 6.2 and 8.0 from the graph, respectively. Therefore, the intensity of the Lα line used for the calibration curve for obtaining the concentration of lead contained in the plating layer is Ap × (8.0 / 6.2).

In addition, the conversion from the X-ray intensity of lead obtained separately to the concentration of lead contained in the substrate is made using a plurality of standard samples in which the substrate and the main component have the same composition and contain different concentrations of lead. The calibration curve may be used. However, the separated X-ray intensity obtained from the sample to be analyzed is a value obtained by passing through the plating layer and reducing the intensity. Therefore, the relationship between the plating thickness and the reduction ratio of the X-ray intensity as shown in FIG. 7 is used to convert to the X-ray intensity when there is no plating layer. FIG. 7 is a graph showing the relationship between the measured strength of Pb-Lα generated from the base, the reduction ratio at which the strength is attenuated by being absorbed by the nickel plating layer, and the plating thickness. For example, when the plating thickness is 3 μm (3.42 mg / cm ² ), the reduction ratio is 0.36 from the graph. Therefore, the intensity of the Lα ray used for the calibration curve for obtaining the concentration of lead contained in the base is Ab / 0.36.

  The method for obtaining the converted X-ray intensity using the relationship shown in FIG. 6 and FIG. 7 is based on the assumption that a calibration curve is used when obtaining the content of lead (analytical element) contained in the plating layer and the base. It is said. However, the concentration of the main component elements other than lead is obtained by incorporating an algorithm that obtains the measured intensity ratio of the X-ray intensity of the lead generated from the plating layer and the base into the calculation routine of the thin film FP method (Fundamental parameter method). It is possible to automatically determine the concentration of lead contained in the plating layer and the base in the same manner as described above.

  In the embodiment of the present invention described above, the coating formed on the base is described using a plated layer or nickel plating layer, and the analysis target element is described as an example of lead. However, the present invention is limited to this. There is no need, for example, the analysis target element may be a harmful metal such as cadmium. Furthermore, the coating is not limited to a plating layer.

  In addition, the two types of characteristic X-rays used for the analysis have been described using the combination examples of the Lα ray and the Lβ ray. However, the combination is not limited to this combination. For example, a combination of the Lα ray and the Lγ ray may be used. A combination of a line and a Kβ line, an Mα line and an Mβ line, or a combination of K, L, and M series characteristic X-rays such as an Lα line and an Mα line may be used.

  As described above, according to the present invention, the measurement intensity of the characteristic X-ray peak generated from the lead (analysis target element) contained in the sample to be analyzed is measured based on the estimated value of the measurement intensity caused by the ground and the coating. Since it can be obtained separately for each of the estimated strength values, it can be known whether the lead exists in the base or the plating layer if the film thickness of the coating is known. Moreover, also when it is contained in both the foundation | substrate and a plating layer, content of lead contained in each can be calculated | required from the measurement intensity | strength of the characteristic X-ray of separated lead.

The schematic diagram for demonstrating the basic idea of this invention. The figure for demonstrating the method of isolate | separating the measurement intensity | strength of the characteristic X-ray from a plating layer and a foundation | substrate. The example of the data which shows the relationship of the intensity ratio change of the Pb characteristic X-ray from a plating layer with respect to plating thickness. The example of the data which shows the relationship of the intensity ratio change of the Pb characteristic X-ray from the foundation | substrate with respect to plating thickness. 1 is a block diagram showing a schematic configuration example of a fluorescent X-ray analyzer that implements the present invention. The example of the relationship which shows the relationship between plating thickness and the Pb characteristic X-ray intensity from a plating layer. The example of the relationship which shows the relationship between plating thickness and the Pb characteristic X-ray intensity from a foundation | substrate. The schematic diagram for demonstrating the example which analyzes the harmful metal (lead) contained in a plating sample by a fluorescent X ray analysis method.

Explanation of symbols

(Those that perform the same or similar operations are denoted by a common reference.)
DESCRIPTION OF SYMBOLS 1 Sample 2 X-ray source 3 Generator power supply 4 X-ray detector 5 X-ray counting system 6 Control system 7 Primary X-ray filter 8 Filter control system 9, 10 Collimator 11 Calculation means 12 Storage means

Claims (6)

A fluorescent X-ray analysis method that irradiates a sample with X-rays and performs elemental analysis using secondary X-rays generated from the sample,
In the analysis of the sample to be analyzed with a film formed on the ground,
Intensity ratio of two kinds of characteristic X-ray peak intensity measurement values generated from the analysis target element contained only in the coating and two kinds of characteristic X-ray peak intensity measurement values generated from the analysis target element contained only in the base In advance, a relationship in which the intensity ratio changes according to the film thickness of the coating,
When the thickness of the coating film of the sample to be analyzed is known, the intensity ratio of the two kinds of characteristic X-ray peak intensity measurement values corresponding to the thickness of the coating film of the sample to be analyzed is determined based on the relationship Obtaining the two types of characteristic X-ray peak intensity measured values from the ground based on the intensity ratio obtained based on the relationship and the two types of characteristic X-ray peak intensity measured values of the sample to be analyzed A fluorescent X-ray analysis method characterized by separately obtaining an estimated value of measured intensity and an estimated value of measured intensity caused by a coating. When the analysis target element is lead, the two kinds of characteristic X-ray peaks are a combination of Pb-Lα and Pb-Lβ, a combination of Pb-Kα and Pb-Kβ, or a combination of Pb-Mα and Pb-Mβ. The X-ray fluorescence analysis method according to claim 1, wherein the method is any one. The fluorescent X-ray analysis method according to claim 1, wherein the coating is nickel plating. Based on the X-ray intensity obtained separately for the estimated value of the measurement intensity caused by the base and the estimated value of the measurement intensity caused by the film, the content of the analysis target element in the base and / or the film is determined. 2. The fluorescent X-ray analysis method according to claim 1, wherein each is obtained separately. A fluorescent X-ray analysis method that irradiates a sample with X-rays and performs elemental analysis using secondary X-rays generated from the sample,
In the analysis of the sample to be analyzed with a film formed on the ground,
Intensity ratio of two kinds of characteristic X-ray peak intensity measurements generated from the analytical element contained only in the coating and / or two characteristic X-ray peak intensities generated from the analytical element contained only in the base In advance, a relationship representing a relationship in which the intensity ratio of the measured values changes according to the thickness of the coating is obtained,
When it is known that the target element for analysis is contained in only one of the film or the base of the sample to be analyzed, the two kinds of characteristic X-ray peak intensity measurement values generated from the film or the base of the sample to be analyzed A fluorescent X-ray analysis method characterized in that the film thickness of the coating corresponding to the intensity ratio is determined from the relationship. A fluorescent X-ray analyzer that irradiates a sample with X-rays and performs elemental analysis using secondary X-rays generated from the sample,
From the intensity ratio of two kinds of characteristic X-ray peak intensity measurements generated from the analysis target element contained only in the coating film of the sample having the coating formed on the ground and / or from the analysis objective element contained only in the groundwork Storage means for storing data representing a relationship in which the intensity ratio of two kinds of generated characteristic X-ray peak intensity measurement values varies depending on the film thickness of the coating;
When the film thickness of the sample to be analyzed with the film formed on the ground is known, the intensity ratio of the two types of characteristic X-ray peak intensity measurement values corresponding to the film thickness of the film of the sample to be analyzed is determined as the film and Using the data stored in the storage means for the ground, the intensity ratio determined using the data and the two types of characteristic X-ray peak intensity measurement values for the sample to be analyzed, the two types X-ray fluorescence analysis characterized by comprising: a calculation means for separately obtaining a characteristic X-ray peak intensity measurement value of each of the measured X-ray peak intensity measurement value resulting from the underlayer and a measurement intensity estimation value resulting from the coating. apparatus.

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