JPH0660879B2 - Simultaneous analysis of coating thickness and composition - Google Patents

Description

The present invention mainly relates to a method for simultaneously analyzing the thickness and composition of a coating of a sample having a plurality of plated coatings made of iron and zinc on a steel sheet.

Like Zn-plated steel, the plating film is Fe, which is the base metal.
With respect to samples composed of other components, a method of quantifying the plating film thickness by a fluorescent X-ray analysis method has been put into practical use. That is, the fluorescent X-ray intensity of Zn-Kα generated from the plated coating or Fe-Kα generated from the base metal can be measured, and the thickness of the plated coating can be determined from the calibration curve obtained in advance.

However, in the case of a Fe-Zn alloy-plated steel sheet, since the element Fe, which is the same as the base metal, is contained in the plating film component, it is not possible to measure the plating film thickness and composition by the conventional fluorescent X-ray analysis method. It was said to be impossible.

Therefore, conventionally, fluorescence X-rays from the base are not substantially detected, and fluorescence X-rays are obtained at a small viewing angle (incident angle) and extraction angle.
It is possible to analyze the thickness and composition of the plating film by measuring the intensity of the X-ray and the intensity of the fluorescent X-ray at a large viewing angle and extraction angle at which the fluorescent X-ray from the substrate is detected. An analysis method is known (Japanese Patent Laid-Open No. 58-22 / 1983).
(See Japanese Patent No. 3047).

However, in this prior art, since the prospect angle and the take-off angle are small angles of, for example, about 5 °, it is well known that the incident beam must be thin to obtain sufficient X-ray intensity. This causes problems such as a complicated structure of the device.

In addition, online analysis may be performed when a plated metal plate is analyzed. That is, an analyzer may be installed on a plated metal plate production line, and a continuously moving plated metal plate may be irradiated with a beam for measurement. In this case, flapping occurs on the metal plate. However, if the projected angle and the take-out angle are small, the flapping causes a slight change in the angle, resulting in a large change in the optical path difference passing through the sample.
Therefore, the analysis accuracy is significantly reduced.

Even in the case of non-online measurement, the incident angle and the take-out angle slightly change due to the surface roughness, warpage, and waviness of the sample, which causes the same problem.

On the other hand, the film to be laminated on the silicon wafer is composed of a multilayer film, and each layer may be extremely thin, about 1500 Å to 3000 Å, so in order to prevent the fluorescent X-rays from being detected from the underlying or lower layer film, The projected or extracted angle is extremely small (about 0.1 °). Therefore, due to a slight change in the thickness of the silicon wafer and the like, the accuracy of analysis also deteriorates.

Therefore, the composition is quantified based on the intensity of the L-series fluorescent X-rays of the metal contained in the plating film, while the intensity of the K-series fluorescent X-rays of the metal and the intensity of the L-series fluorescent X-rays are determined. Based on this, a fluorescent X-ray analysis method for quantifying the film thickness has been proposed (Japanese Patent Application No. 59-60357 (Japanese Patent Application Laid-Open No. 60-20233).
No. 9))). In this prior art, the wavelength of the above-mentioned L-series fluorescent X-rays is long, and therefore the L-series fluorescent X-rays are absorbed by the plating film. It focuses on the fact that the composition is uniquely determined. In other words, the fluorescent X-rays of the L series do not substantially detect the fluorescent X-rays from the base. Therefore, in the case of a plating film of ordinary thickness, the composition of the plating film is determined from the intensity of the L-series fluorescent X-rays. You can ask.

However, if the fluorescent X-rays from the base are not substantially detected in this way, only the analysis of the upper layer film can be performed when a large number of layers are provided, and the second layer from the top can be analyzed. Also, no analysis can be performed on the lower layer coating.

In particular, in a plated steel sheet having a plurality of layers of coating, the coating of the upper layer is often extremely thin (for example, about 1 μm), so that fluorescent X-rays are not substantially detected from the base 1 (second layer). As a result, the incident and extraction angles are extremely small (about 1 °) even with the use of L-series fluorescent X-rays.
As described above, various inconveniences occur.

This invention has been made in view of the above conventional problems,
Enables simultaneous analysis of the thickness and composition of multiple layers of coatings and coatings that contain the same element in the underlying layer, and makes the projection angle (incident angle) and extraction angle within an angle range that does not pose a practical problem. By setting, the structure of the device does not become complicated,
Moreover, the purpose is to improve the analysis accuracy.

In order to achieve the above object, in the method of the present invention, first, the same first element is contained in the base, the first layer coating and the second layer coating, and the first layer and second layer coatings are contained. In a fluorescent X-ray analysis of a sample containing the same second element in, the intensity of the fluorescent X-ray for the first and second elements is determined by at least one of energy, extraction angle or prospect angle. Four types of measurements are performed in different manners, and the theoretical X-ray intensity calculation formula based on the principle of generation of fluorescent X-rays is calculated from the coating of at least the first and second layers of the fluorescent X-rays related to the above four types of measurement intensities. The unknown thickness and composition are determined by the successive approximation method using the intensity of the fluorescent X-rays measured above and the theoretical X-ray intensity calculation formula.

According to the method of the present invention, since the theoretical X-ray intensity calculation formula is set such that the fluorescent X-rays are generated from at least both films, the fluorescent X-rays may be generated from the second layer. And the take-off angle can be increased to such an extent that it does not pose a problem in practice. Therefore, the structure of the device is simplified and the optical path difference does not change so much even when the level of the surface of the sample changes and the viewing angle and the take-out angle change slightly. improves.

Further, as described above, since the fluorescent X-rays are generated from both coatings, the composition and the film thickness of these coatings can be measured even if the coating has a plurality of layers.

As an example, in a sample in which a lower layer plating consisting of a large amount of zinc and a small amount of iron and an upper layer plating consisting of a large amount of iron and a small amount of zinc were applied on a steel plate, the upper layer plating amount ...... t ₁ (1 10g / m ² ) Amount of iron in the upper plating …… W _1Fe (50 to 100wt%) Amount of the same zinc _・・ ・ W _1Zn (0 to 50wt%) Lower plating attachment layer …… t ₂ (10 to 50g / m ² ) It will be determined an unknown amount of six of the amount of the underlying plating in the iron ...... W _2Fe (10~30wt%) the amount of the zinc ... W _2Zn (70~90wt%). As described above, since the elements constituting the sample are two kinds of iron and zinc and the unknown amounts are the above-mentioned six kinds, quantitative analysis by the calibration method has heretofore been impossible. However, the measured fluorescent X-ray intensity I _i is
The physical constant such as the mass absorption coefficient determined by the X-ray i used for the measurement is u, the expected angle of the incident X-ray and the fluorescence X.
Let V be a constant determined by the measurement conditions such as the take-out angle of the line, I _i = f (t ₁ , t ₂ , W _1Fe , W _2Fe , W _1Zn , W _2Zn , u, V) (1) Can be expressed as Furthermore, in such a two-layer plated sample, W _1Fe + W _1Zn = 1.0 ...... (2) W _2Fe + W _2Zn = 1.0 ...... (3) holds, so the unknown quantities are t ₁ , t ₂ , W _1Fe , With W _{2 Fe} only, the thickness and composition of each coating can be analyzed by using four independent measurement lines. For example, Zn
-Kα, Zn-Kβ, Fe-Kα, Fe-Kβ, Zn-
Since the physical quantity such as the mass absorption coefficient is different depending on the fluorescent X-rays used for the measurement of Lα, Fe-Lα, etc., and the correlation of the unknown quantity contributing to the generation is different, u in the formula (1) is It will be different. Further, when the incident angle of the primary X-rays, that is, the expected angle ψ ₁ or the extraction angle ψ ₂ is changed, the relationship between the detected fluorescence X-ray intensity and the unknown amount is different.
V in the formula (1) is different.

Therefore, the physical constants determined by the fluorescent X-rays used for measurement are u ₁ , u ₂ , u ₃ , u ₄ , and the device constants determined by the measurement conditions such as the prospect angle are V ₁ , V ₂ , If V ₃ and V ₄ are given, the intensity of the fluorescent X-ray detected in each case I ₁ , I ₂ , I ₃ , I ₄ is I ₁ = f (t ₁ , t ₂ , W _1Fe , W _2Fe , W _1Zn , W _2Zn , u ₁ , V ₁ ) ・ ・ ・ (4) I ₂ = f (t ₁ , t ₂ , W _1Fe , W _2Fe , W _1Zn , W _2Zn , u ₂ , V ₂ ) ・ ・ ・(5) I ₃ = f (t ₁ , t ₂ , W _1Fe , W _2Fe , W _1Zn , W _2Zn , u ₃ , V ₃ ) ・ ・ ・ (6) I ₄ = f (t ₁ , t ₂ , W _1Fe , W _2Fe , W _1Zn , W _2Zn , u ₄ , V ₄ ) ... (7), and from the above 6 formulas (2) to (7), 2
The thickness and composition of each of the layer-plated layers can be determined.
However, since the simultaneous equations of these six equations cannot generally obtain an analytical solution, the desired unknown quantity is usually obtained by the successive approximation calculation method. However, an electronic computer is used as a part of the measuring device. By incorporating it, the measured value can be calculated in a short time.

Next, examples of the present invention will be described. As shown in FIG. 1, the prospective angle ψ of the primary X-ray radiated to the sample 1 having the first and second plating layers having different compositions provided on the surface of the underlying metal plate, and the fluorescent X-ray to be detected The type and the extraction angle are set as shown in Table 1, and the intensities of the respective fluorescent X-rays are simultaneously measured. Figure 1 In the configuration diagram of this measuring device, the source 1 for irradiating the sample 1 with X-rays is installed so as to have an expected angle of 20 °, and the extraction angles of the fluorescent X-rays are 30 °, 80 °, and 20 °, respectively. The X-ray detectors 3 to 6 are provided so as to be at 80 ° and 80 °. The output of each detector is passed through amplifiers 7 to 10 to a pulse height analyzer.
In addition to 11-14, the wave height analysis of the detected X-ray as shown in Table 1 is performed, and the intensity is measured by the counters 15-18. The outputs of the four counters are added to the arithmetic unit 19, and the result of the sequential calculation as described above is displayed on the display unit 20.

As another embodiment, as shown by the arrow in FIG. 2, the source 2 and one fluorescent X-ray detector 21 having variable angles of view φ and extraction are provided opposite to the sample 1. Its detector
The output of 21 is amplified by the amplifier 22, and the pulse height analyzer 23 and the counter 2
4, the arithmetic unit 25 and the display unit 20 are sequentially added, and in such a device, V of the first formula is changed by changing the projected angle and the take-out angle.

Next, the successive approximation calculation by the calculator 19 or 25 in FIGS. 1 and 2 will be described. First measured fluorescence X
The line strength is converted into a theoretical strength scale, and the elements of the apparatus are standardized to perform processing such that the measured strength X _i is represented on the same scale as the theoretical strength, and the standardized strength is defined as Y _i . For this purpose, the ratio of the intensity of the fluorescent X-rays on the plate of pure iron or pure lead to the intensity of the fluorescent X-rays and the method of regressing by the correlation between the fluorescent X-ray intensity of the standard sample and the theoretical X-ray intensity are used. .

For unknown quantities, their initial values ▲ t ^(o) ₁ ▼, ▲ t ^(o) ₂
By setting ▼, ▲ W ^(o) _1Fe ▼, ▲ W ^(o) _2Fe ▼, etc. and calculating the theoretical X-ray intensity from the unknown quantity, the nth successive approximation value ▲ t ⁽ⁿ⁾ ₁ ▼, ▲ t ⁽ⁿ⁾ ₂ ▼, ▲ W ⁽ⁿ⁾ _1Fe ▼,
Obtain ▲ W ⁽ⁿ⁾ _{2 Fe} ▼. Furthermore, the measured quantities Y ₁ , Y ₂ , Y ₃ , Y ₄ standardized for the four types of measurement lines described above are However, ▲ I ⁿ ₁ ▼, ▲ I ⁿ ₂ ▼ ... Are given by the theoretical X-ray intensity based on the n-th order approximation value, and this simultaneous equation is expressed by Δt ₁ , Δt ₂ , Δ.
Solving for W _1Fe and ΔW _2Fe , the approximation is ▲ t ^{(n + 1)} ₁ ▼ ＝ ▲ t ⁽ⁿ⁾ ₁ ▼ ＋ Δt ₁・ ・ ・ (12) ▲ t ^{(n + 1)} ₂ ▼ ＝ ▲ t ^{( n)} ₂ ▼ + Δt ₂・ ・ ・ (13) ▲ W ^{(n + 1)} _1Fe ▼ ＝ ▲ W ⁽ⁿ⁾ _1Fe ▼ ＋ ΔW _1Fe・ ・ ・ (14) ▲ W ^{(n + 1)} _2Fe ▼ ＝ ▲ W ^{( n)} _2Fe ▼ + ΔW _2Fe (15) _Therefore , each unknown quantity of the nth approximation value and the unknown quantity of the (n + 1) th approximation value are compared to judge the convergence condition, and successively. When the approximation is further continued, the calculation is repeated from the equations (8) to (11).

As shown in FIG. 3, the first layer 27 and the second layer are formed on the base 26.
The X-ray with intensity I ₀ was applied to the sample on which 28 coatings were formed.
_When the fluorescence X-rays are detected with an extraction angle of ψ _i from each layer with _β incident, let the intensity of the actually measured fluorescence X-rays be I ₁ , I ₂ , and I _3. , A first layer 27 with a deposit of t ₁ and an iron content of W _1Fe, a second layer 28 with a deposit of t ₂ and an iron content of W _2Fe , and a substrate for which the deposit can be regarded as infinite The theoretical fluorescent X-ray intensities I ₁ ′, I ₂ ′ and I ₃ ′ from 26 are However, ▲ μ ^p ₁ ▼, ▲ μ ^p ₂ ▼, and ▲ μ ^p ₃ ▼ are the total mass absorption coefficients of each layer for incident X-rays ▲ μ ^s ₁ ▼, ▲ μ ^s ₂ ▼, and ▲ μ ^s ₃ ▼ are measurement X-rays. mass absorption coefficient total mass absorption coefficient mu / [rho of each mass absorption coefficient of the analysis element to the incident X-ray ▲ mu ^j _i ▼ is for jX line i substance to Is.

Next, regarding the sample in which two plating layers made of zinc and iron were provided on the steel plate, the expected angle of the primary X-ray was 20 ° and the fluorescent X-ray Zn
When the extraction angle of -Lα is 30 °, the extraction angles of Zn-Kα are 80 ° and 20 °, and the extraction angle of Fe-Kα is 80 °, the measurement is performed by the method of the present invention as described above. As a result, the results shown in the table below were obtained. Na Oh d is when the X-ray analysis value is XA and the chemical analysis value is CA It is a value defined by.

[Brief description of drawings]

1 and 2 are diagrams showing the construction of an apparatus for carrying out the method of the present invention, and FIG. 3 is a schematic diagram for explaining the principle of the present invention. In the figure, 1 is a sample, 2 to 6 are X-ray detectors, 7 to 10 are amplifiers, 11 to 14 are wave height analyzers, 15 to 18 are counters, 19 is a calculator, 20 is a display,
21 is an X-ray detector, 22 is an amplifier, 23 is a wave height analyzer, 24 is a counter, and 25 is a calculator.

Claims (1)

[Claims] 1. An underlayer, a first layer coating and a second layer coating contain the same first element, and a first layer and a second layer coating contain the same second element. , First layer and second
Each of the coatings of the layers, in the fluorescent X-ray analysis of the sample consisting of the first and second elements, shows the intensity of the fluorescent X-rays for the first and second elements,
Energy of incident X-ray to sample, extraction angle φ or projected angle ψ
At least one of which is different from each other, and four types are measured, and the following theoretical X-ray intensity calculation formula based on the principle of generation of fluorescent X-rays is used. The thickness and composition of the coating, which is set to be generated from the coating of the second layer, is used to obtain an unknown thickness and composition by the successive approximation method using the measured fluorescent X-ray intensity and the theoretical X-ray intensity calculation formula. Simultaneous analysis method. Theoretical X-ray intensity calculation formula: When the sum of theoretical X-ray intensities from the first layer coating, the second layer coating and the ground is I ', However, the subscripts 1, 2 and 3 are the first layer coating,
Each of the second layer coating and the base is shown. ▲ μ ^P ₁ ▼, ▲ μ ^P ₂ ▼, ▲ μ ^P ₃ ▼ are the total mass absorption coefficients of each layer for incident X-rays ▲ μ ^S ₁ ▼, ▲ μ ^S ₂ ▼, ▲ μ ^S ₃ ▼ are for the measured X-rays The total mass absorption coefficient μ / ρ of each layer is the mass absorption coefficient of the analytical element for incident X-rays ψ _i is the X-ray angle of view φ _i is the X-ray extraction angle t ₁ , t ₂ of the first layer and the second layer The adhered amounts (thicknesses) W _1a and W _2a represent the contents of the first element in the first layer and the second layer, respectively.