JPH08122503A - Formation of thin film - Google Patents

Abstract

PURPOSE: To provide a method for forming an optical thin film consisting of an oxide dielectric whose adhesive power and wear resistance are improved and further in which the occurrence of cracks is prevented and which has good durability. CONSTITUTION: When forming a thin film consisting of an oxide dielectric on the surface of a substrate 31 by vacuum deposition, after an oxide dielectric layer is formed while the substrate 31 is heated to 100-350 deg.C and the surface is irradiated with electron rays by an electron ray irradiating device 35 or after an oxide dielectric layer is formed and successively the surface of the oxide dielectric layer is irradiated with electron rays while the substrate 31 is heated to 100-350 deg.C the layer is subjected to heating oxidation in air or in an oxygen atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film, and more particularly to a method for forming an oxide dielectric used as an optical thin film material.

[0002]

2. Description of the Related Art Conventionally, optical elements mounted in optical systems such as cameras and video projectors are required to have antireflection performance, high reflection performance, wavelength separation performance, and the like.

In order to satisfy these requirements, an optical element is known in which an optical thin film is formed on the surface of an optical substrate by vacuum vapor deposition. An oxide dielectric is often used as a material for forming the optical thin film. ing.

For example, there is one in which a color filter having a film constitution as shown in (Table 1) is formed on the surface of a glass lens. An oxide dielectric is also used for this, and such an optical thin film is used. Is required to have adhesiveness with a substrate material and durability such as abrasion resistance.

[0005]

[Table 1]

Therefore, when forming the color filter on the surface of the glass lens, a method of heating the substrate temperature to about 100 to 350 ° C. and vacuum-depositing the film is used. It is widely known that this gives stronger adhesion than vacuum deposition at room temperature, a hard film is formed, and a film having excellent durability can be obtained.

[0007]

However, even with the above-described forming method, it is rare that the adhesion of the optical thin film to the optical substrate and the durability such as abrasion resistance are sufficiently satisfactory. Furthermore, during the formation of a thin film by vacuum evaporation, the oxide becomes lower, causing absorption in any wavelength range.
There is a problem that the optical characteristics deteriorate.

Therefore, in the present invention, an optical thin film made of an oxide dielectric having improved adhesion, wear resistance, less absorption, and good crack resistance, and an optical film using the same. It is intended to provide an element.

[0009]

In order to solve the above problems, in the method for forming a thin film of the present invention, the surface of the substrate is irradiated with an electron beam when the film is vapor-deposited to a desired thickness by vacuum evaporation. While forming a thin film, or after forming a thin film, the surface of the thin film is irradiated with an electron beam to complete the thin film formation.

After that, the thin film is heated and oxidized in air or oxygen atmosphere. The electron beam density applied at this time is preferably about 100 to 1500 μA.

Further, the temperature of the substrate is 100 to 100 when forming the thin film.
The effect is further enhanced if the heating is performed at 350 ° C.

[0012]

According to the above structure, the thin film forming method of the present invention has the following functions.

The structure of the thin film of the present invention is composed of an oxide dielectric or includes this layer. By irradiating with an electron beam during or after formation of the oxide dielectric layer by vacuum deposition, Improves and improves the adhesion with the substrate,
A durable film with a fine structure and excellent wear resistance is formed. Further, electron beam irradiation relaxes the internal stress in the film and suppresses the generation of cracks.

However, in addition to the above, irradiation with an electron beam during vapor deposition accelerates conversion of the oxide dielectric material into a lower oxide, causing absorption and deteriorating the optical characteristics of the film. Therefore, after forming a film by vacuum vapor deposition, the thin film is subjected to a heat oxidation treatment in air or an oxygen atmosphere to oxidize the oxide dielectric thin film again to remove absorption and prevent deterioration of optical characteristics.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows the structure (cross-sectional view) of an optical thin film (filter) according to the first embodiment of the present invention.
In FIG. 1, 11 is a glass substrate, 12 is a tantalum oxide layer, and 13 is a silicon oxide layer.

FIG. 2 shows how the oxide dielectric optical thin film is formed. The conditions for forming each layer are as follows. First, the glass substrate 21 is set in the substrate holder 23 in the vacuum deposition tank 22, the substrate temperature is reduced to room temperature, and the vacuum pressure is set to 2 * 10 ⁻⁵ torr or less. While introducing 3 to 10 cc of oxygen gas to the target film thickness, while irradiating the surface of the glass substrate 21 with an electron beam from the electron beam irradiation device 25 at a current density of 400 to 600 μA / cm ² , a deposition rate of about 6 to 8 Å / sec. Formed.

Silicon oxide was evaporated from the evaporation source 26 to have an optical film thickness shown in Table 1 and a vacuum pressure of 2 × 10 ⁻⁵ t.
The electron beam irradiation device 25 applies an electron beam to the surface of the glass substrate 21 at a current density of 400 to 600 while keeping the temperature at or less
Deposition rate of about 6-8Å / se while irradiating with μA / cm ²
Formed in c.

After that, it was taken out of the vacuum chamber 22 and heated from room temperature to 400 ° C. in 30 minutes in an electric furnace, and at 400 ° C. for 6 minutes.
It was kept for 0 minutes and allowed to cool to room temperature.

The following items were tested in order to confirm the adhesion and durability of the antireflection film obtained by this method. (A) Peeling test (high temperature of 40 ° C. and relative humidity of 85%
After standing in a high humidity atmosphere for 168 hours, the adhesive tape is adhered to the surface of the optical component and peeled off. ) (B) High temperature test (leave in atmosphere of temperature 80 ° C for 250 hours) (c) Low temperature test (leave in atmosphere of temperature -20 ° C for 250 hours) (d) Moisture resistance test (temperature 60 ° C, High temperature of 90% relative humidity
Leave in a high humidity atmosphere for 168 hours. (E) Thermal shock test (remaining in a low temperature / high temperature atmosphere at temperatures of −30 ° C. and 80 ° C. for 30 minutes alternately for about 24 hours) The results of the above reliability test are shown in (Table 2). As shown.

[0021]

[Table 2]

As can be seen from (Table 2), the thin film of the present invention has excellent adhesion to the substrate and durability.

Further, the average transmittance in the high transmittance wavelength range of 400 to 460 nm of the optical thin film of this example was about 82% before the firing step, but became 90% or more after the firing step.

(Second Embodiment) The structure of the second embodiment is shown in FIG. 1 as in the first embodiment. FIG. 3 shows a state when the optical thin film of the oxide dielectric is formed.

The conditions for forming each layer are as follows. First, the glass substrate 31 is set on the substrate holder 33 in the vacuum vapor deposition tank 32, the vacuum pressure is set to 2 × 10 ⁻⁵ torr or less, and the substrate temperature is stabilized at 300 ° C. by the heater 37. While flowing oxygen gas in an amount of 3 to 10 cc to the optical film thickness shown in 1), an electron beam irradiation device 35 electron beam is applied to the surface of the glass substrate 31 at a current density of 400 to 6
Deposition rate of about 6-8Å / while irradiating with 00 μA / cm ²
It was formed in sec.

An electron beam irradiator is provided on the surface of the glass substrate 31 while maintaining the optical film thickness of silicon oxide from the evaporation source 36 at the substrate temperature of 300 ° C. and the vacuum pressure of 2 × 10 ⁻⁵ torr or less, respectively. 35 electron beam current density 4
Deposition rate of about 6 while irradiating with 0 to 600 μA / cm ²
It was formed at ~ 8Å / sec.

After that, it was taken out of the vacuum chamber 32, and the temperature was raised from room temperature to 400 ° C. in 30 minutes in an electric furnace, and the temperature was raised to 6 ° C. at 400 ° C.
It was kept for 0 minutes and allowed to cool to room temperature.

The following items were tested in order to confirm the adhesion and durability of this example. (A) Peeling test (high temperature of 40 ° C. and relative humidity of 85%
After leaving in a high humidity atmosphere for 500 hours, the adhesive tape is adhered to the surface of the optical component and peeled off. (B) High temperature test (leaving in an atmosphere of temperature 80 ° C for 500 hours) (c) Low temperature test (leaving in an atmosphere of temperature -20 ° C for 500 hours) (d) Moisture resistance test (temperature 60 ° C, High temperature of 90% relative humidity
Leave for 500 hours in a high humidity atmosphere. (E) Thermal shock test (remaining in a low temperature / high temperature atmosphere at temperatures of -30 ° C. and 80 ° C. for 30 minutes each alternately is repeated for about 96 hours.) The results of the reliability test are shown in (Table 3). As shown.

[0029]

[Table 3]

As can be seen from (Table 3), the thin film of the present invention has excellent adhesion to the substrate and durability.

The average transmittance of the optical thin film of this example in the high transmittance wavelength range of 400 to 460 nm was about 85% before the firing step, but became 90% or more after the firing step.

As can be seen from (Table 3), in addition to the forming method of the first embodiment, by heating the substrate temperature to 300 ° C. to form a thin film, the adhesion with the substrate is improved as compared with the first embodiment. did.

[0033]

As described above, according to the present invention, when a thin film made of an oxide dielectric is formed on the surface of a glass substrate by vacuum vapor deposition, the surface of the glass substrate is irradiated with an electron beam while the oxide dielectric layer is being irradiated. After forming the film, it is heated and oxidized in air or an oxygen atmosphere, so that it is possible to realize an optical thin film having excellent adhesion to a substrate and durability and preventing deterioration of optical characteristics.

Although a glass substrate is used as the substrate in the above embodiment, a substrate having heat resistance such as a ceramic substrate can also be used.

Further, although tantalum oxide and silicon dioxide were used as the oxide dielectric in the above-mentioned embodiments, titanium oxide, zirconium dioxide, lead oxide, tantalum oxide, yttrium oxide, zirconium titanate, cerium oxide, silicon oxide and tin oxide are used. Oxide dielectrics such as alumina can also be used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an optical thin film in first and second embodiments of the present invention.

FIG. 2 is a state diagram at the time of forming an optical thin film of an oxide dielectric in the first embodiment of the present invention.

FIG. 3 is a state diagram at the time of forming an optical thin film of an oxide dielectric in the second embodiment of the present invention.

[Explanation of symbols]

 11 Glass Substrate 12 Tantalum Oxide Layer 13 Silicon Oxide Layer 21 Glass Substrate 22 Vacuum Deposition Tank 23 Substrate Holder 24 Evaporation Source A 25 Electron Beam Irradiation Device 26 Evaporation Source B 31 Glass Substrate 32 Vacuum Deposition Tank 33 Substrate Holder 34 Evaporation Source A 35 Electrons Ray irradiation device 36 Evaporation source B 37 Heater

Claims (5)

[Claims] 1. When forming a thin film of an oxide dielectric on the surface of a substrate by vacuum vapor deposition, the oxide dielectric thin film layer is formed on the surface of the substrate while irradiating an electron beam, and then in air or an oxygen atmosphere. A method for forming an optical thin film, wherein the thin film is subjected to a thermal oxidation treatment. 2. When forming a thin film of an oxide dielectric on the surface of a substrate by vacuum deposition, an oxide dielectric thin film layer is formed on the surface of the substrate, and then the surface of this layer is irradiated with an electron beam. A method for forming an optical thin film, which comprises subjecting the thin film to a heat oxidation treatment in air or an oxygen atmosphere. 3. The method for forming a thin film according to claim 1, wherein when forming a thin film on the substrate by vacuum vapor deposition, the glass substrate is heated to 100 to 350 ° C. to form the thin film. 4. The method for forming a thin film according to claim 1, wherein the substrate is a glass substrate or a ceramic substrate. 5. The oxide dielectric material is tantalum oxide, zirconium dioxide, lead oxide, yttrium oxide, zirconium titanate, cerium oxide, silicon oxide, tin oxide, alumina,
5. The method of forming a thin film according to claim 1, wherein the thin film is an oxide of.