JPH03183761A - Vapor deposition method - Google Patents

Abstract

PURPOSE:To stably produce a vapor deposited film having uniform film thickness and free from reduction in F content by vacuum-depositing MgF2 in the presence of O2 gas or a gaseous mixture of O2 and inert gas. CONSTITUTION:The vacuum vapor deposition of MgF2 is carried out in the presence of O2 gas or gaseous mixture of O2 and inert gas, such as Ar. At this time, suitable O2 gas pressure is about 1.0-4X10<-4>mbar. Further, it is preferable to regulate the temp. of the substrate for vapor deposition to about 250-350 deg.C. By this method, the vapor deposited film having uniform film thickness, free from reduction in F content in the film, and excellent in the reproducibility and precision of optical refractive index can be obtained. By cumulatively vacuum-depositing the MgF2 low refractive index layer onto the high refractivity index layer composed essentially of TiO2 or Pr2O3 by the above method, the cumulative vapor deposited layer having uniform and stable optical properties can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for depositing a thin film used in an optical system, and more particularly to stabilizing the composition of a thin film.

(Background of the Invention) In recent years, the need for large-capacity data storage devices has increased, and optical disk devices, magneto-optical disk devices, and the like have come into widespread use. These devices use optical heads to read data. A beam splitter is used in this optical head, and in the Mukuro optical head, for example, a high refractive index electrically shielding material and a low refractive index dielectric material are vacuum-evaporated on one surface of a prism processed into a predetermined shape. A laminated optical film is formed by alternately stacking layers.

The vacuum evaporation method is widely used because there are few contraindications to the evaporation substance, easy control of thin film formation, good workability, and suitability for mass production.

However, on the other hand, the properties of the thin film tend to change depending on the deposition conditions, and when alloys and compounds are deposited, there are often differences between the evaporation source and the deposition process. That is, in general, in the vacuum evaporation method, in order to make the thickness of the evaporated film uniform on the substrate placed in the substrate holder, an inert gas such as argon is introduced into the vacuum chamber and the gas pressure is adjusted. However, often between production batches or within patches,
The properties of the thin film deposited on the substrate vary.

As a notable example, when magnesium fluoride (hereinafter referred to as MgFx, where X≦2) is deposited in the presence of argon (Ar) gas, the fluorine content decreases, and therefore the magnesium (Mg) 11 increases. The primary film composition fluctuates, leading to a change in the refractive index.

Therefore, a high refractive index layer of titanium oxide (TtO, ), praseodymium oxide (Prow), or a mixture thereof, Tie, -Pry, is applied to the surface of optical members such as lenses and prisms, and M
When gFx is repeatedly laminated as a low refractive index layer to form a cumulative N (referred to as coating) having predetermined optical properties, the reproducibility of optical properties such as transmittance, reflectance, or polarization, and the accuracy of performance values are improved. becomes extremely unstable.

(Objective of the Invention) The object of the present invention is to ensure that, in vacuum evaporation involving MgFx, the evaporated film on the substrate placed in the substrate holder is uniform between manufacturing batches and within the batch; 1) the thickness of the evaporated film is uniform; There is no decrease in the fluorine content in the MgFx deposited film, and the reproducibility and accuracy of the optical refractive index are good. 3) The optical properties of the cumulative deposited layer consisting of a high refractive index layer and a low refractive index layer related to MgFx are uniform. , stable.

The purpose of the present invention is to provide a vapor deposition method.

(Structure and Effects of the Invention) The object of the present invention described above is characterized in that MgFx is vacuum evaporated in the presence of oxygen gas or a mixed gas of oxygen and an inert gas such as Ar, N*, etc. Achieved by vapor deposition method.

Furthermore, embodiments of the present invention can be effectively used for cumulative vacuum deposition of high refractive index and MgFx low refractive index layers, and the high refractive index layer may be Ti01, Pr01 or a mixture thereof T.
It is also useful when using ie, -Pry.

Next, FIG. 1 shows an outline of the vacuum evaporation apparatus used for the vacuum evaporation of the present invention.

In the figure, 11 is a vacuum chamber, and 12 is a rotating vapor deposition substrate holder having a curved surface with a diameter of 80 to 150 cm, and the rotation ensures uniformity of vapor deposition.

13 is a crucible containing an evaporation source. In the present invention, MgF x is used as a low refractive index material (referred to as L material), and Tie, Pro, or a mixture thereof TiO, -PrO, is used as a high refractive index material (H material).

The evaporation source is evaporated by heating, but in the present invention, evaporation is preferably performed by an electron beam 15 from an electron gun 14.

16 is a gas introduction pipe, and oxygen (0,) according to the present invention
The gas is 1.0 to 4 when used alone or in combination with Ar gas.
Adjusted to XIO-'+mbar. The Ar gas used in combination is preferably 10 to 3XIO-'mbar.

Also, the deposition rate is 1O~50A/see for both H materials.
controlled by.

When using BK-7 glass as the deposition substrate, the substrate temperature is 2.
The temperature is adjusted to 50-350°C, preferably 300°C.

Under the above requirements, Ar gas alone, O, gas alone and Ar
Table 1 shows relative values of fluorine content in the deposited film when a MgFx layer is deposited by introducing a mixed gas of gas and O gas.As is clear from Table 1, the fluorine content increases due to the presence of O gas. , the optical properties become stable, and the uniformity of the film thickness distribution within and between batches increases.

The fluorine content was measured using Auger electron spectroscopy. Similar problems were also observed when N gas was used instead of Ar gas.

Further, the number of deposited layers to be accumulated can be arbitrarily determined as necessary. The high refractive index layer in the present invention may be a single layer of 101PrOx or a composite high refractive index layer of a Ti0x-PrOx mixture, but all the high refractive index layers are composite high refractive index layers. Preferably, it is a refractive index layer.

In addition, the weight ratio of pro and 'rio in as and ym is 0.5 to 5, preferably 2 to 3.

Further, the mixture may contain metals such as Zr, Ta, Y, La, etc. and/or oxides thereof to the extent that the properties are not impaired.

〔Example〕

Next, the present invention will be specifically explained with reference to Examples.

Example 1 A mixture containing Pro and TiO2 as main components (for example, E
.

Product name “Substance 2H” manufactured by Merck; hereinafter 5ub
−■) is a high refractive index material, stoichiometrically MgF is a low refractive index material, and a right equilateral triangular glass prism (
Seven layers were alternately and cumulatively deposited on the hypotenuse surface of material: BK-7) using vacuum deposition. During vapor deposition, the substrate heating temperature was 300°C. 5ub-II is 0. Gas 2X10-'mbar
, deposition rate 4 A/see%MgF, is 0. gas 3
The deposition was carried out at XlO-'mbar% 10 people/see.

Counting from the hypotenuse surface, the odd numbered layer is a high refractive index layer (5ub-n layer) of 123.6 gtμ, and the even numbered layer is 196.7-μ.
A low refractive index layer (MgFx layer) was used.

After the vapor deposition, the prism was taken out into the atmosphere, and the hypotenuse surface was bonded to a bonded glass prism of the same shape (material: BK-7) using an ultraviolet curing adhesive (No. 61, manufactured by Norland). The optical prism shown in FIG. 2 was produced by irradiating ultraviolet rays with an intensity of 10 mw/cm'' for 5 seconds for temporary fixing and 10 minutes for final curing.

FIG. 3 shows the spectral transmittance of the P-wave component and the S-wave component when light is incident perpendicularly to this prism (the angle of incidence on the laminated film is 45').

780±15m as shown by solid lines A, A, in the figure.
In the wavelength region of μ, P wave component; transmittance 85 ± 1% 1 reflectance 15 ± 1% S wave component; transmittance 4 ± 1% 1 reflectance 96 ± 1%, stoichiometric MgF! Design optical characteristics (curves Cp, Cm
) was changed to a value close to .

In addition, the performance becomes more uniform and the accuracy becomes better. It also has good reproducibility.

Comparative Example (1) The same material and layer configuration as in Example 1 were used, and the introduced gas was 5ub-I.
I; O, gas, 2X10-'mbarMgF1;
A bonded prism was prepared in exactly the same manner except that Ar gas and 3×1 G-'mbar were used and evaluated in the same manner, and the results are also shown in FIG. 3 (curve B□ns).

P wave component: transmittance 90 ± 3%, reflectance lO ± 3% S wave component: transmittance 2 ± 3%, reflectance 98 ± 3% Compared to the example, the P wave component increases in transmittance, The S wave component decreases.

Stoichiometric MgF! There was a large deviation from the design value using , the accuracy of the performance value decreased, and the reproducibility also decreased.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a vacuum evaporation apparatus according to the present invention, FIG. 2 is a cross-sectional view of a bonded prism having high and low refractive index layer coatings according to the present invention, and FIG. 3 is a diagram showing P and S waves of the bonded prism. It is a relationship diagram of the light transmittance of a component - wavelength.

Claims (3)

[Claims] (1) A vapor deposition method characterized in that vacuum vapor deposition of magnesium fluoride is performed in the presence of oxygen gas or a mixed gas of oxygen and an inert gas. (2) A vapor deposition method characterized by forming a magnesium fluoride low refractive index layer in the presence of oxygen gas or a mixed gas of oxygen and an inert gas in the cumulative vacuum deposition of the high refractive index layer and the low refractive index layer. . (3) The vapor deposition method according to claim 2, wherein a material containing titanium oxide, praseodymium oxide, or a mixture of titanium oxide and praseodymium oxide as a main component is used as the high refractive index layer.