JP2712194B2 - Optical reflector and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical reflecting mirror and a method for manufacturing the same. [Prior Art] For example, as shown in FIG.
Is a state in which the reflection film 6 made of Al, Au, Cu, or the like is provided on the base material 4 or Al ₂ O
₃ , a protective film 8 made of CaF ₂ or LiF ₂ was provided. In this case, the reflective film 6 is formed by an evaporation method such as ion plating or sputtering, and the protective film 8 is formed by a vapor phase growth method such as a CVD method. [Problems to be Solved by the Invention] However, in the case of the optical reflecting mirror 2 having no protective film 8, the reflecting film 6 is easily oxidized (in the case of Al, Cu, etc.) and is easily scratched. Therefore, there is a problem that the optical characteristics are easily deteriorated. In the case of the optical reflecting mirror 2 provided with the protective film 8, Al ₂ O ₃ , CaF ₂ , and LiF ₂ as the protective film 8 have good transparency to laser light having a wavelength of, for example, about 1 μm. But,
Since the thermal conductivity is poor, there is a problem that when a large power laser beam is reflected, a thermal stress acts due to a local heating effect, and the reflective film 6 is easily peeled off. On the other hand, regarding the manufacturing method, in the deposition method such as ion plating and sputtering, the energy of the particles deposited on the substrate 4 is as small as several tens to several hundreds eV at most, so that the reflection film 6 with respect to the substrate 4 There is a problem that the adhesiveness is poor and therefore the reflection film 6 is easily peeled off from the substrate 4. Further, in the vapor phase growth method such as the CVD method, since the base material 4 needs to be heated to a high temperature (for example, near 1000 ° C.), the material that can be used as the base material 4 is limited, There is also a problem that the reflection film 6 may peel off from the base material 4 due to heat. Therefore, an object of the present invention is to provide an optical reflecting mirror that solves the above problems and a method of manufacturing the same. [Means for Solving the Problems] The optical reflecting mirror of the present invention has a reflective film on a base material and a protective film made of aluminum nitride thereon,
In addition, a mixed layer containing both constituent materials is provided near the interface between the base material and the reflective film. The first manufacturing method of the present invention is to form a reflective film on a substrate by performing deposition of a reflective film material and irradiation of ions having an energy of 5 KeV to 40 KeV on the substrate in a vacuum, and A first step of forming a mixed layer containing both constituents near the interface between the two, and a vacuum evaporation of aluminum and energy of 200 eV to 1 keV with respect to the reflective film formed by the step; And a step of forming a protective film made of aluminum nitride on the reflective film by irradiating with nitrogen ions. In the second production method of the present invention, a substrate in which a reflective film is formed on a substrate is prepared, and 5 KeV to 40
A first step of forming a mixed layer containing both constituents near the interface between the base material and the reflective film by implanting ions having KeV energy, and A second step of forming a protective film made of aluminum nitride on the reflective film by performing aluminum vapor deposition and irradiation with nitrogen ions having an energy of 200 eV to 1 KeV. [Operation] In the optical reflecting mirror of the present invention, aluminum nitride as a protective film is excellent in corrosion resistance, abrasion resistance and the like, so that the underlying reflective film is not easily oxidized and is not easily damaged. In addition, since aluminum nitride has a high light transmittance and a high thermal conductivity, local heating is unlikely to occur even when high-power light is reflected, and therefore, the reflection film is not easily peeled off. In addition, since the mixed layer acts like a wedge, the adhesion of the reflection film to the base material is high, and from this point, the reflection film is not easily peeled off. According to the first manufacturing method of the present invention, in the first step, a reflective film is formed on the base material by vapor deposition, and a substance constituting the reflective film is driven into the base material by irradiation ions, Alternatively, the material constituting the base material is also beaten into the reflection film together therewith, so that a mixed layer containing both constituent materials is formed near the interface between the base material and the reflection film. Further, in the second step, the deposited aluminum and the irradiated nitrogen ions combine to form a protective film made of aluminum nitride on the reflective film without heating the substrate or the like to a high temperature. According to the second manufacturing method of the present invention, the substance constituting the reflection film provided in advance on the substrate is driven into the substrate by the implanted ions, or the substance constituting the substrate together with the substance is reflected. By being beaten into the film, a mixed layer containing both components is formed near the interface between the base material and the reflective film. Further, in the second step, the deposited aluminum and the irradiated nitrogen ions combine to form a protective film made of aluminum nitride on the reflective film without heating the substrate or the like to a high temperature. Embodiment FIG. 1 is a sectional view showing an example of an optical reflecting mirror according to the present invention. This optical reflecting mirror 12 has a reflecting film 6 on a base material 4 and a protective film 10 made of aluminum nitride (AlN) on the reflecting film 6, and near an interface between the base material 4 and the reflecting film 6, Both have a mixed layer 5 containing the constituent materials of 4 and 6. As the substrate 4, for example, quartz glass, fluorides such as MgF ₂ and CaF ₂ can be used. The reflection film 6 is made of a thin film of, for example, Al, Au, or Cu. In the optical reflecting mirror 12, since the aluminum nitride as the protective film 10 is excellent in corrosion resistance, abrasion resistance, etc., the lower reflecting film 6 is hardly oxidized and is not easily scratched.
Thereby, the deterioration of the optical characteristics can be prevented. Moreover, since aluminum nitride has high light transmittance in the visible to near-infrared region, high thermal conductivity, and good heat dissipation, a wavelength of about 1 μm from a high-output laser such as a dye laser or a glass laser is used. Even when the laser beam of high power is reflected, local heating is unlikely to occur, and therefore, the reflection film 6 is not easily peeled off from the base material 4. In addition, since the mixed layer 5 acts like a wedge, the adhesion of the reflective film 6 to the substrate 4 is high, and the difference in the coefficient of thermal expansion between the substrate 4 and the reflective film 6 is determined by the composition. Since it can be absorbed by the continuously changing mixed layer 5, the base material 4
The generation of thermal stress between the substrate and the reflection film 6 is also suppressed. Therefore, the combination of the point of using aluminum nitride for the protective film 10 and the point of having the mixed layer 5 makes it very difficult for the reflective film 6 to peel off. Therefore, the optical reflecting mirror 12 is used as, for example, a laser mirror or the like. Even when used, it has a long life. Next, an example of a method for manufacturing the above-described optical reflecting mirror 12 will be described with reference to FIG. A holder 18 for holding the base material 4 as described above is placed in the vacuum container 14 by rotating the holder 18 as shown by an arrow A to turn it left and right (left and right on the paper surface; the same applies hereinafter).
It is attached to and stored. A high-energy ion source 26a and a low-energy ion source 26b are attached to the left and right sides of the vacuum container 14 so as to face the base material 4 on the holder 18 turned left and right, respectively. Are provided with two evaporation sources 20a and 20b. The evaporation sources 20a and 20b are both evaporation materials in this example.
An electron beam evaporation source using an electron beam for heating and evaporating 21a and 21b, but other types can also be used. 24a and 24b are film thickness monitors for measuring the film thickness and the like of the film deposited on the base material 4 and the like by the evaporation sources 20a and 20b, respectively. In this example, the ion sources 26a and 26b are both bucket-type ion sources that use a multipolar magnetic field for plasma confinement, and can extract the accelerated ions 28a and 28b over a large area with good uniformity. Large area processing is possible, but other types can also be used. At the time of processing, for example, the above-described base material 4 is mounted on the holder 18 and the inside of the vacuum vessel 14 is evacuated to, for example, about 10 ⁻⁵ to 10 ⁻⁷ Torr. The material 4 is directed toward the high-energy ion source 26a as shown by a solid line in the drawing, and a reflective film material 22a made of any one of, for example, Al, Au, Cu, etc. is evaporated from the evaporation source 20a, and the material 4 is evaporated. Simultaneously with or alternately with the above deposition, Ar, Ne, He, Kr, as ions 28a from the ion source 26a.
Inert gas ions such as Xe or reflective film material to be deposited 22
The same metal ions as in (a) are continuously or intermittently extracted and irradiated toward the substrate 4. The reason for using such an ion species as the ion 28a is to prevent impurities from being mixed into the film. Incidentally, since inert gas ions are poor in reactivity, they are easily gasified and escape from the film. By the above-described processing, the reflective film material 22a is deposited on the surface of the base material 4 to form the reflective film 6 (see FIG. 1) as described above. When the material 4 is beaten into the material 4 or the material constituting the substrate 4 is beaten into the reflection film 6 together with the material 4, the vicinity of the interface between the substrate 4 and the reflection film 6 is reduced.
A mixed layer 5 as described above comprising the constituents of 6 is formed. In this case, the mixed layer 5 and the reflective film 6 having a desired film thickness may be formed by using both the deposition of the reflective film material 22a and the irradiation of the ions 28a.
After the reflective film 6 having a certain thickness is formed, the thickness of the reflective film 6 may be increased to a desired thickness only by depositing the reflective film material 22a. On the other hand, if the energy of the irradiation ions 28a is too large, the sputtering effect on the reflective film material 22a deposited on the base material 4 cannot be ignored, and if it is too small, the mixed layer 5 is hardly formed. 5KeV ~
It is preferable to be within the range of about 40 KeV. How much energy is set within this range depends on the type of the substrate 4 and the type and thickness of the reflective film material 22a to be deposited,
For example, when the deposition of the reflective film material 22a and the irradiation of the ions 28a are performed alternately, the range of the irradiated ions 28a (average projected range) is set so as to be approximately equal to the thickness of the reflective film material 22a to be deposited before that. Is preferred. The irradiation amount of the ion 28a is that it hardly can mixed layer 5 with too small, liable can Gasuboido like inside the mixed layer 5 such as a too large Conversely, for example, 10 ¹⁶ to 10 ¹⁸
It is preferred to be about ions / cm ² . The angle of incidence θ of the ion 28a with respect to the base material 4 (the angle with respect to a vertical line formed on the surface of the base material 4) θ
For example, from the viewpoint of preventing sputtering of the reflection film 6 due to
It is preferable that the angle be in the range of about {60}. The irradiation of the ions 28a may be performed while heating the substrate 4 by a heating means (not shown) in order to reduce the occurrence of irradiation damage in the reflection film 6 and the mixed layer 5 due to the ions 28a. When irradiating the metal ions as described above as the ions 28a, the bucket-type ion source 26 as described above is used.
Instead of using a, a spot-shaped ion beam extracted from a metal ion source and subjected to mass analysis may be scanned and irradiated over a required area. Next, after the above-described processing, as a second step, the holder 18 and the base material 4 are moved toward the low-energy ion source 26b in the same vacuum vessel 14 as shown by a two-dot chain line in the drawing. At the same time or alternately with evaporating the aluminum 22b from the evaporation source 20b and evaporating it on the surface of the reflective film 6 on the substrate 4, the nitrogen ions 28b are continuously or intermittently extracted from the ion source 26b. Reflective film 6 on base material 4
Irradiate toward At this time, the particle ratio (composition ratio) Al / N of the deposited aluminum (Al) and the irradiated nitrogen ions (N) with respect to the reflection film 6 is set to, for example, about 0.5 to 2.0,
Preferably, it is 1.0 or 1.5. As a result, deposited aluminum 22b and irradiated nitrogen ions 28b
Is formed on the surface of the reflective film 6 to form the above-described protective film 10 made of aluminum nitride (see FIG. 1), whereby the optical reflecting mirror 12 as described above is obtained. At this time, the energy of the nitrogen ions 28b may cause damage (defects) inside the protective film 10 due to the irradiation, thereby deteriorating various physical properties of the film, and roughening the surface of the protective film 10 due to sputtering. From the viewpoint of minimizing the energy, it is preferable to make the energy as low as 1 KeV or less, and more preferably in the range of about 200 eV to 800 eV. This will be described with reference to FIGS. 3 and 4. FIG. 3 shows the energy and the transmittance of the protective film 10 in the visible to near infrared region when the energy of the nitrogen ion 28b is changed. It is a graph showing an example of the relationship with,
FIG. 4 is a graph showing an example of the relationship between the energy of the nitrogen ions 28b and the optical band gap of the protective film 10 at the same time. As can be seen from FIG. 3, when the energy of the nitrogen ions 28b is 1 KeV or less, the obtained protective film 10 has a high light transmittance of about 90% or more. As can be seen from FIG. 4, when the energy of the nitrogen ions 28b is 1 KeV or less, the obtained protective film 10 has an optical band gap close to the theoretical value of 6.2 eV of aluminum nitride. By the way,
It can be said that the closer the optical band gap is to the theoretical value, the more excellent the physical properties such as the thermal conductivity are. On the other hand, when the energy of the nitrogen ions 28b exceeds 1 KeV, both the light transmittance and the optical band gap of the protective film 10 tend to decrease. It is considered that this is due to the increase in the number of defective portions in 10. In this case, for the same reason as in the case of the first step described above, the incident angle θ of the nitrogen ions 28b with respect to the base material 4 is
For example, it is preferable that the angle be in the range of about 0 ° to 60 °. When forming the protective film 10, the base material 4 may be heated by a heating means (not shown) or cooled by a cooling means (not shown), if necessary. The defects can be promoted, and the defects generated in the protective film 10 can be removed during the film production, and if cooled, complete prevention of thermal deformation of the base material 4 can be expected. The features of the above-described manufacturing method are as follows. By forming the mixed layer 5 between the base material 4 and the reflection film 6, the reflection film 6 with high adhesion can be formed. Since neither the reflective film 6 nor the protective film 10 is formed mainly by thermal excitation, it can be processed at a low temperature such as room temperature, so that the range of materials that can be used as the base material 4 is greatly expanded, and In addition, there is no fear that the reflection film 6 is peeled off from the substrate 4 due to heat during the processing. Al / N composition ratio of the protective film 10 is basically nitrogen ion 28
Since it is determined by the beam current b and the deposition amount of the aluminum 22b, the controllability is good, and thus the high-quality protective film 10 can be formed. Since all the processes can be performed in the same vacuum vessel 14, there is no contamination by the air, and therefore, the reflection film 6 and the protection film 10 of good quality can be formed by preventing the contamination of impurities. The high-energy ion source 26a can effectively form the mixed layer 5 for enhancing the adhesion of the reflective film 6, and the low-energy ion source 26b forms the high-quality protective film 10 with less irradiation damage. be able to. In the first step, the mixed layer 5 and the reflective layer 6 on the base material 4 are formed by the combination of the deposition of the reflective film material 22a and the irradiation of the ions 28a. A reflection film 6 having a reflection film 6 formed in advance by a known means on the base material 4 is prepared and attached to the holder 18 in the vacuum container 14, and the reflection film 6 is drawn from the high energy ion source 26a as described above. The other ions 28a may be implanted from the reflection film 6 side. In that case, the evaporation source 20a need not be provided. Even by such a process, the substance constituting the reflective film 6 is driven into the base material 4 by the implanted ions 28a,
Alternatively, the material constituting the base material 4 is also beaten into the reflection film 6 together with the material, and the components 4 and 6 are included near the interface between the base material 4 and the reflection film 6 as described above. The mixed layer 5 is formed. The subsequent second step is the same as described above. In this case, the preferable ranges of the energy of the ion 28a, the incident angle θ, the implantation amount, and the like are substantially the same as those in the case of the above-described first step. Further, in each of the above, the case where the second step of the first step and the second step are performed in the same vacuum vessel 14 is exemplified, but the present invention is not necessarily limited thereto, and both steps are performed in another vacuum vessel. May be. [Effects of the Invention] As described above, according to the optical reflecting mirror of the present invention,
The lower reflective film can be protected by the protective film made of aluminum nitride to prevent deterioration of its optical characteristics.
In addition, since aluminum nitride has high light transmittance and high thermal conductivity, local heating is unlikely to occur even when high power light is reflected. In addition, since the mixed layer acts like a wedge, the adhesion of the reflection film to the base material is high, and the reflection film is not easily peeled off. In addition, the difference in thermal expansion coefficient between the substrate and the reflective film can be absorbed by the mixed layer whose composition is continuously changed, so that the generation of thermal stress between the substrate and the reflective film can be suppressed. Therefore, even if heating occurs, for example, in the case of reflecting high-power light, the reflection film is not easily peeled off. Therefore, the life of the optical reflecting mirror is also improved. Further, according to the manufacturing method of the present invention, it is possible to manufacture an optical reflecting mirror having the above-described mixed layer and a protective film made of high-quality aluminum nitride having excellent light transmittance and thermal conductivity. In addition, since the treatment can be performed at a low temperature such as room temperature, the range of materials that can be used as the base material is greatly expanded, and there is no possibility that the reflection film is peeled off due to heat during the treatment. Moreover, since the energy of the irradiation ions in the first step is set to 5 KeV to 40 KeV,
A mixed layer can be formed well near the interface between the substrate and the reflective film while realizing a high-quality reflective film with a smooth surface by suppressing the sputtering action and irradiation damage to the reflective film by irradiation ions. In addition, since the energy of the irradiated nitrogen ions in the second step is set to 200 eV to 1 KeV, a defect is generated inside the protective film and various physical properties of the film are reduced, and the surface of the protective film is roughened by sputtering. This can be minimized, so that a high-quality protective film having excellent properties such as light transmittance and thermal conductivity can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an example of an optical reflecting mirror according to the present invention. FIG. 2 is a schematic view showing an example of an apparatus for performing the manufacturing method according to the present invention. FIG. 3 is a graph showing an example of the relationship between the energy of a nitrogen ion and the transmittance of the protective film in the visible to near-infrared region when the energy is changed by changing the energy of the nitrogen ion. FIG. 4 is a graph showing an example of the relationship between the energy of the nitrogen ion and the optical band gap of the protective film when the energy is changed. FIG. 5 is a sectional view showing an example of a conventional optical reflecting mirror. 4 ... substrate, 5 ... mixed layer, 6 ... reflective film, 10 ... protective film, 12 ... optical reflecting mirror according to the embodiment, 14 ... vacuum vessel, 20a, 20b ... evaporation source, 22a: Reflective film material, 22b ...
Aluminum, 26a, 26b ... Ion source, 28a ... Ion,
28b …… Nitrogen ion.

Claims (1)

(57) [Claims] A reflective film on the base material, a protective film made of aluminum nitride on the reflective film, and a mixed layer containing both constituent materials near the interface between the base material and the reflective film. Optical reflector. 2. Deposition of reflective film material on substrate in vacuum and 5 KeV ~
Irradiation with ions having an energy of 40 KeV to form a reflection film on the base material and a mixed layer containing both constituent materials near the interface between the two, and Forming a protective film made of aluminum nitride on the reflective film by performing aluminum deposition and irradiation of nitrogen ions having an energy of 200 eV to 1 KeV in vacuum on the formed reflective film; And a method of manufacturing an optical reflecting mirror. 3. Prepare a substrate with a reflective film formed on it and inject ions having an energy of 5 KeV to 40 KeV from the reflective film side in a vacuum to form both components near the interface between the substrate and the reflective film. First forming a mixed layer comprising a substance
Forming a protective film made of aluminum nitride on the reflective film by performing aluminum deposition and irradiation of nitrogen ions having an energy of 200 eV to 1 KeV on the reflective film in a vacuum. 2. A method for manufacturing an optical reflecting mirror, comprising: