JPH0619267B2 - Thickness measurement method for multi-layer metal sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention provides high-speed and high-accuracy measurement of the thickness of a multilayer plate, which is a combination of thin and thick layers, such as a plated plate, using X-rays. Regarding what to do.

(B) Conventional technology In order to measure the thickness of each layer of a multilayer board, it is possible to use a conventional fluorescent X-ray analyzer, and to excite the sample with X-rays or gamma rays, Fluorescent X-rays may be measured separately, but in the case of a multi-layer plate such as plating that consists of a relatively thick layer and an extremely thin layer, the signal from the thick layer becomes the background when measuring the signal from the thin layer. Greatly influence
It has drawbacks such as poor S / N ratio and time-consuming X-ray pulse measurement. Also when measuring the crystal scattering of X-rays in each layer, the signal from the thick layer influences the background when measuring the thin layer and the S / N ratio is poor, and if the irradiated X-rays are monochromatic for noise removal, the spectrometer Therefore, there is a drawback that the signal amount is weakened because the sample is twice subjected to crystal scattering.

(C) Objective The present invention aims to solve the above problems and provide a method for accurately measuring the thickness of each layer of a multilayer board at high speed.

(D) Structure In order to achieve the above object, in the present invention, the multilayer plate (sample) is irradiated with monochromatic X-rays, and its wavelength λ is before and after the X-ray absorption edge wavelength of the element constituting the thick layer of the sample. The secondary X-ray from the sample is measured, and the thickness of each layer of the sample is calculated from the change in the measured value accompanying the change in the wavelength of the irradiation X-ray.

FIG. 1 shows a schematic diagram of an apparatus for carrying out the present invention. (1) is an X-ray generator, which is composed of an X-ray tube, an X-ray spectrometer, a collimator (slit), etc., and generates X-rays (irradiated X-rays).
(2)) is a thin beam monochromatic X-ray, the wavelength λ of which is variable by driving the spectroscope. (3) is a multilayer board sample,
(4) is the secondary X-ray from the sample (3), and the secondary X-ray includes fluorescent X-rays, crystal scattered X-rays and other scattered X-rays. The detector (5) for measuring the secondary X-rays should be placed at a position not touching the irradiated X-rays (2).
Place it near (3) and detect secondary X-rays directly.

(E) Examples Hereinafter, the present invention will be described in detail with reference to Examples. FIG. 2 illustrates a multilayer plate (sample) and irradiated X-rays (2) and secondary X-rays. The first layer (11) of the sample is a thin silver plating layer and the second layer (12) is copper. If the thickness of each layer is T ₁ and T ₂ , the detection intensity I (λ) is T ₁ ,
Considered as a function of T ₂ , λ, it is expressed by the following equation.

Here, T ₁₀ and T ₂₀ are average thicknesses of T ₁ and T ₂ , and are known. t ₁ and t ₂ are changes in the thickness of the first layer and the second layer with respect to each average thickness.

The X-ray absorption coefficient for the wavelength λ has an absorption edge wavelength peculiar to the element. For copper, for example, λ is about 1.35 Å
It has an absorption edge at (Å) and its absorption coefficient is large at a slightly smaller wavelength λ ₁ , but sharply decreases at a slightly larger wavelength λ ₂ .

Therefore, if the intensity I (λ) of equation (1) is measured at wavelengths λ ₁ and λ ₂ ,
== λ ₁ , the irradiation X-rays are absorbed in the second layer and the amount reaching the opposite surface is small, Can be regarded as Since (1) takes a relatively large value, Becomes On the other hand, at λ = λ ₂ as well as Since both take relatively large values Therefore, in Eqs. (2) and (3), If I (λ ₂ ) −F (T ₁₀ , T ₂₀ , λ ₂ ) = b ₃ and each is measured in advance and known,
Equations (2) and (3) are a ₁ · t ₁ = a ₃ ………………… (4) b ₁ · t ₁ + b ₂ · t ₂ = b ₃ …………… (5) from now on Becomes Here, since a ₁ and b ₂ have relatively large values as described above, equation (6) is meaningful and the thicknesses T ₁ and T ₂ of the _first and second layers are Is calculated as

(F) Effect As described above, the thickness of each layer of a multilayer plate such as a plated plate can be measured by the method of the present invention. Since the measurement does not require pulse measurement, the measurement circuit is simple and the measurement time is at least sufficiently accurate. When detecting the secondary X-rays from the sample, there is no need to disperse the secondary X-rays, and the sample and the detector can be placed very close to each other, so the detection sensitivity is high and therefore the measurement accuracy is good. is there.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an apparatus for carrying out the present invention. FIG. 2 is a diagram showing an example of a sample. (1) …… X-ray generator, (2) …… Irradiated X-ray (3) …… Sample, (4) …… Secondary X-ray (5) …… Detector, (11) …… First layer (12) …… Second layer

Claims (1)

[Claims] 1. A monochromatic X-ray is irradiated on a sample of a multilayer plate composed of a thin layer and a thick layer, and its wavelength is changed before and after the X-ray absorption edge wavelength of an element constituting the thick layer,
2 from the sample by a detector placed in the vicinity of the sample
The next X-ray is directly detected, and the thickness of the multilayer of the sample of the multilayer plate is calculated by the change of the detection output of the secondary X-ray due to the change of the wavelength of the irradiation X-ray. Thickness measurement method.