HU199009B - Method for controlling the thickness of coat-work - Google Patents

Abstract

The essence of the invention is that the energy-homogeneous electron beam energy (e) is varied by the redemption of the acceleration voltage of the source (1) and the detector (4) and the associated measuring device (5), which analyzes the characteristic radiation in the ultra-bed spectrum characteristic of the base plate (3). and the thickness of the coating (2) is determined by the amount of energy (Eq) of the electron beam at which the radiation spectrum of the base plate (3) is displayed. EN 199009 B Scope of the play: 3 solutions, Figure 1 -1-

Description

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling the thickness of coatings which can be used in control and measurement techniques and which enables the thickness of coatings to be smoothly controlled and measured by radiation through the material, in particular electron beam and X-ray.

Methods for measuring the thickness of coatings are known, which in principle consist of irradiating the substance to be measured with an electron beam homogeneous in energy and measuring the reflected electrons of different energies after reflection (see, for example, SU 397 748). The sensitivity obtained by such a process is not high, since the energy intervals are chosen depending on the ratio of the effective atomic numbers of the substrate and the coating, and the energy of the incident electron beam is chosen depending on the thickness of the coating.

From the technical point of view, and closest to the subject matter of the present invention, the solution involves irradiating the base plate and the coating applied thereto with an electron beam homogeneous in energy, measuring the characteristic spectra and determining the thickness of the coating (see, e.g., CA Anderson, Microprobe (Eds. Mekinley, Heinrich, Wittry, Willey, New York, 1966, p. 581).

The disadvantages of the known methods are the low sensitivity, which, in turn, results from methodological problems in performing the measurements, first of all the need to perform parallel measurements and at the same time to compare the radiation intensity of a bulk coating always prepare.

The object of the invention is to increase the sensitivity.

The object of the present invention has been achieved by providing a method for controlling the thickness of coatings by irradiating the substrate and the coating applied thereto with an electron beam homogeneous in energy, measuring the spectrum of characteristic radiation and determining the thickness of the coating. a step of varying the energy homogeneous electron beams and measuring the characteristic radiation in the ultra-soft spectrum characteristic of the substrate and measuring the thickness of the coating according to the magnitude of the electron energy at which the spectral spectrum of the substrate appears.

The process of the present invention will now be described in more detail with reference to an exemplary embodiment, with reference to the accompanying drawings, in which:

Figure 1 illustrates an embodiment of the method of the invention; the

Figure 2 shows an example for determining the effective thickness of a coating.

The example of Figure 1 is a schematic of a control device comprising a source 1 which generates electrically homogeneous electrons and is directed towards the coating 2 to be inspected. The coating 2 is applied to a base plate 3, and an analyzing detector 4 and a measuring device 5 are arranged above the coating 2.

The above equipment works as follows:

The ultra-soft characteristic X-rays generated by the homogeneous energy emitted by the source 1 from the source 1 pass through the coating 2 and into the analyzer detector 4, where they are transformed and applied to the measuring device 5.

This energy of the homogeneous energy delivered by the source 1 is varied and increased until the ultra-soft characteristic X-ray spectrum of the substrate is displayed and the thickness of the coating is calculated as follows:

H = k- ^En (1) aZ where:

k and n are constant coefficients depending on the magnitude of the energy of the electron beam E _o , if the thickness of the coating is in cm, p is the density of the material in g / cm ³ ,

A is the atomic weight of the coating material,

Z is the atomic number of the coating material,

E _{o is} the electron beam energy, which is characterized by the characteristic x-ray radiation of the base plate in uV.

Thus, the test specimen, which is located in a vacuum, is emitted with an electron beam whose energy is determined by the acceleration voltage of the source 1 (e.g., between the filament and the test specimen), cf.

1. When the electrical energy (voltage) is gradually increased from zero, the penetration depth of the electrons in the coating 2 is increased.

At a given value of the energy of the electron beam E _u , the average penetration depth in the coating 2 becomes equal to the thickness of the coating. When this value is exceeded, the electrons begin to penetrate the base plate 3, where this ultra-soft characteristic X-ray radiation excites the atoms in the composition of the base plate 3. Since the characteristic X-ray transmission has a much higher transmittance compared to electrons, it passes through the base plate 3 and generates a signal in the analyzing detector 4 which is fed to the measuring device 5. In this way, determine the electron energy at which a signal corresponding to ultra-soft characteristic X-ray radiation is generated in the measuring device 5. With this energy, the penetration of electrons into the material of the coating 2 corresponds to the thickness of the coating, which is determined by equation (1).

If the coating consists of several components, the A _eff and Z _eff values shall be calculated as follows:

HU 199009 Β

Σ ttj A; Zi

A «ff - -,

Σ 'η; Zi

Σ ü) Aj Zj

Zeff “-En, Aj where n _{i (} Aj and Zj are the number, atomic weight and atomic number of atoms in the coating components, respectively). The A _eff / Z _e ff ratio varies slightly between 2 and 2.6 for any material.

In the case of multilayer coatings, the layers directly below another layer can be considered as a base plate for the layer above, in which case their thickness can be obtained from equation (1) by subtracting the energy of the electron beam, released.

Shown in the definition of E _p electron beam energy values in the case of Figure 2, when the substrate sheet of aluminum coated with an oxide layer of alumina was selected from three samples which have different thickness of the coating. Changes made by such process measurements 03/10 '^ m (10, a linear) vastaságú oxide layer (the measurement results are extrapolated values rounded), 3,8,10' ⁹ m (30 weight straight) and 4.310 ^'9 m (20 labeled linear ).

By this method high sensitivity can be achieved since each material has its own and known characteristic ultra-soft X-ray spectrum, by which the material in question can be recognized.

The coating thickness control performed by the process of the present invention can be performed conveniently from a technological point of view and the energy of the electron beam can be selected so as to be sure to pass through the coating to be checked. By measuring and comparing the intensity values of the coating and the baseplate lines, very small differences in coating thickness can be detected very quickly on different samples.

Claims (1)

A method for controlling the thickness of coatings by irradiating the base plate and the coating applied thereto with a source of electron beam homogeneous in energy, measuring the characteristic spectra and determining the thickness of the coating, characterized in that the energy (e) is varied by changing the source (1) acceleration voltage, and the characteristic radiation characteristic of the base plate (3) ultra soft spectral analysis region of the detector (4) and wherein interconnected measuring device by means of (5) measuring, and (22) the thickness of the coating to an electron beam energy (E _o ), at which the radiation spectrum of the base plate (3) appears.