JP3409942B2 - Film thickness determination method using color measurement - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used in the metal industry, particularly in the fields of automobiles, building materials, cans, etc.
When removing the surface oxide layer of an alloy sheet used for painting after assembly and phosphate conversion treatment, measure the degree of removal, and adhere to rolling oil and rust prevention oil in the metal sheet manufacturing industry. It relates to measurement and the like for controlling the amount. [0002] When a thin film layer is present on the surface of a solid, conventional methods for quantifying the thickness of the thin film layer include X-ray photoelectron spectroscopy and ellipsometry. On the other hand, a photoelectric colorimeter measures tristimulus values defined by the International Commission on Illumination (CIE), and converts them into, for example, L ^* , a ^* , b ^* colorimetric indices to quantify color. Is what you do. Unlike the spectral colorimeter, the photoelectric colorimeter directly obtains tristimulus values with three sensors having the same spectral sensitivity as the tristimulus values without using a spectroscope such as a diffraction grating or a prism.
Therefore, photoelectric colorimeters are smaller, cheaper ,
It has advantages such as high operability and quick measurement, and has been conventionally used for color quality management and the like in industries such as painting, dyeing, and printing. [0003] The conventional method for determining the thickness of a thin film on a solid surface has the following disadvantages. That is, X-ray photoelectron spectroscopy and ellipsometry have disadvantages such as expensive equipment and time-consuming analysis, and X-ray photoelectron spectroscopy has limitations such as measurement atmosphere and sample shape. For example, it is not practical for use in controlling a manufacturing process, and the range of use is limited. Therefore, a simpler method is desired in terms of time and cost. Further, colorimeter although conventionally used for the management of color quality, especially for the following thick film 50nm has not been used for the determination of its thickness. The present invention quantifies the thickness of a thin film on a solid surface more quickly, easily and inexpensively and without cutting out a material as compared with the above-mentioned conventional method .
It is intended to provide a method for doing so. [0004] The present invention SUMMARY OF] The thin-film layer to a solid surface (the solid and the complex refractive index of the wavelength dependency of different ones)
Exists, the lightness index L in the L ^* , a ^* , b ^* color system , which is a uniform perceived color space, of the same solid covered with the same thin film having a known thickness in advance using a photoelectric colorimeter.
^{*, *} Black Manet Genetics indices ^a, by measuring either the colorimetric index b ^*, etc., in advance to create a film thickness correction curve showing the correlation between the film thickness and the color specification indices, then the thickness Is characterized in that the colorimetric index of the same solid surface covered with the unknown thin film is measured by the colorimeter and compared with the correction line to determine the thickness of the unknown thin film. In particular, in the case of a film thickness of 50 nm or less that does not cause interference color, the fact that the film thickness of the thin film uniquely corresponds to any one of values such as L ^* , a ^* , b ^*, etc. is used. Generally, when the thickness of a thin film is 50 nm, an interference color is generated. Thus, for example, ^{for L *,} a *, ^{b *} of each value does not correspond uniquely to the thickness of the thin film, ^L *,
It is difficult to determine the film thickness from only one of a ^* and b ^* . However the thickness of the thin film 5
In the case of 0 nm or less, the film thickness can be determined by measuring any of L ^* , a ^* , and b ^* , for example. In addition, the quantification method of the present invention does not alter the sample at all. EXAMPLE 1 A plurality of samples having different thicknesses of magnesium oxide layers were prepared on the surface of an Al-5 wt% Mg alloy which had been previously polished and flattened by a magnetron sputter deposition apparatus.
The film thickness was measured by a stylus type film thickness meter. Next, the L ^* values of these samples were measured with a photoelectric colorimeter. FIG. 1 shows the relationship between the film thickness and the L ^* value. As is clear from FIG. 1, the thickness of the magnesium oxide layer shows a unique correspondence with the L ^* value. Therefore, it can be seen that FIG. 1 can be used as a correction line for determining the thickness of the magnesium oxide layer. Next, the L ^* value of a sample whose thickness of the magnesium oxide layer was unknown was determined using the same system produced by the magnetron sputter deposition apparatus.
A value of 6.4 was obtained. The measurement results are shown in FIG. Comparing this value with the correction line in FIG. 1 indicates that the thickness of the magnesium oxide layer on the surface of the sample is 10 nm. As a precaution, when the oxide film thickness of the same pickling sample was measured by X-ray photoelectron spectroscopy, it was 10 nm, and it was confirmed that the oxide film thickness could be accurately measured by the method of the present invention. Example 2 An Al-5 wt% Mg alloy plate was 1 mm thick and 900 mm wide.
After cold rolling, the resultant was degreased in a degreasing agent bath at 70 ° C. for about 20 seconds, and the pickling loss was adjusted while gradually changing the pickling time in a 10 wt% sulfuric acid solution at 60 ° C. Next, b ^* of the alloy surface at each pickling stage was measured with a photoelectric colorimeter. Next, the oxide film thickness was determined using X-ray photoelectron spectroscopy. FIG. 2 shows the relationship between the film thickness and the b ^* value. As apparent from FIG. 2, the thickness of the magnesium oxide layer against black Manet Genetics index b ^* value indicates a unique correspondence. Therefore, FIG. 2 can be used as a correction line for obtaining the oxide film thickness. Next, the aluminum alloy was manufactured under the same conditions as when the correction line of FIG. 2 was manufactured,
Pickling was performed for 3 seconds. When the value of b ^* of this sample was determined,
A value of 4.7 was obtained. The measurement results are shown in FIG. By comparing this value with the correction line in FIG. 2, it was determined that the oxide film thickness of the pickled sample surface was 5 nm. As a precaution, when the oxide film thickness of the same pickling sample was measured by X-ray photoelectron spectroscopy, it was 5 nm, and it was confirmed that the oxide film thickness could be accurately measured by the method of the present invention. According to the present invention, the thickness of an oxide film or the like on a solid surface can be quantitatively determined. Moreover, the measurement is quick, inexpensive,
It can be carried out simply and the measurement does not change the sample. Therefore, for example, in the pickling step of an aluminum-magnesium alloy, the line speed, temperature, acid concentration, etc. are adjusted so that any of L ^* , a ^* , b ^* measured according to the present invention falls within a predetermined range. If controlled, the degree of pickling can be controlled on-line with high accuracy and speed, and high-quality can be obtained at low cost, and the yield can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the relationship between the thickness of a magnesium oxide layer sputter-deposited on a mirror-polished aluminum-magnesium alloy plate substrate and a lightness index L ^* . FIG. 4 is a view showing a relationship between an oxide film thickness on a surface of a magnesium alloy plate and a chromonetics index b ^* .

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Kobayashi 4-3-1-18 Nihonbashi Muromachi, Chuo-ku, Tokyo Inside Sky Aluminum Co., Ltd. (72) Inventor Goro Kitayama 4-3-1, Nihonbashi Muromachi, Chuo-ku, Tokyo (56) References JP-A-6-50722 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/06 G01J 3/46

Claims (1)

(57) to the Claims 1 solid surface, and the solid ones having different wavelength dependence of the complex refractive index, 50 nm below its thickness is an area that will not cause interference color In the film thickness quantification method in the case where the thin film layer is present, L ^* , a ^* , b , which is a uniform perceived color space of the same solid covered by the same thin film having a known thickness using a photoelectric colorimeter in advance. ^* By measuring a colorimetric index such as a colorimetric system, a film thickness correction line showing a correlation between the film thickness and the colorimetric index is created, and then the thickness is adjusted to 50 nm.
A color measurement characterized by determining the thickness of the unknown thin film by measuring the colorimetric index of the same solid surface covered by the following unknown thin film with the colorimeter and comparing with the correction line. Film thickness determination method used.