JP2008158345A - Method for manufacturing optical filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical filter, with which durability of an optical filter is improved. <P>SOLUTION: The method for manufacturing the optical filter has a first process to deposit an optical multilayer film 3 on a front face of a substrate 2 under a first ion beam irradiation condition by using an ion beam assisted vapor deposition method, and a process to deposit the optical multilayer film 3 on a rear face of the substrate 2 under a second ion beam irradiation condition by using the ion beam assisted vapor deposition method after completing the first process, wherein the first and second ion beam irradiation conditions are controlled in such a way that internal stress of the optical multilayer film 3 deposited on the front face of the substrate 2 and that deposited on the rear face of the substrate 2 are balanced with each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical filter having optical multilayer films on both sides of a substrate.

In recent years, the specifications required for optical filters have become stricter year by year, and optical filters are required to have precise optical characteristics. From such a background, there has been proposed an optical filter that realizes precise optical characteristics by forming optical multilayer films on both the front and back surfaces of a substrate (see Patent Documents 1 and 2).
JP 7-209516 A JP 2005-43755 A

  However, in the conventional optical filter, after the optical multilayer film is formed on one surface of the substrate, the optical film is optically formed on the other surface of the substrate under the same film formation conditions as when the optical multilayer film is formed on one surface of the substrate. The optical multilayer film formed on one surface of the substrate is produced by warping the entire substrate when the optical multilayer film is formed on the other surface of the substrate because the multilayer film is manufactured. It becomes easy to peel off. Against this background, according to the conventional method for manufacturing an optical filter, it has been difficult to manufacture a highly durable optical filter.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a method of manufacturing an optical filter capable of improving durability.

  In order to solve the above-described problems, a feature of the method for producing an optical filter according to the present invention is a method for producing an optical filter having an optical multilayer film on both sides of a substrate, which is a first method using an ion beam assisted deposition method. A first step of forming an optical multilayer film on one surface of the substrate under the ion beam irradiation conditions, and after the completion of the first step, the other side of the substrate under the second ion beam irradiation conditions using an ion beam assisted deposition method. An optical multilayer film formed on one surface of the substrate, and an internal stress of the optical multilayer film formed on one surface of the substrate and an internal stress of the optical multilayer film formed on the other surface of the substrate, That is, the first and second ion beam irradiation conditions are controlled to balance each other.

  According to the method for producing an optical filter according to the present invention, the internal stress of the optical multilayer film formed on one surface of the substrate is not formed on both surfaces of the substrate under the same film formation conditions. Film forming conditions on the one surface of the substrate and the optical multilayer film on the other surface of the substrate so that the internal stress of the optical multilayer film formed on the other surface of the substrate is balanced Since the film formation conditions for forming the film are controlled, the optical filter can be manufactured with a high yield.

Hereinafter, the manufacturing method of the optical filter which concerns on this invention is demonstrated in detail based on an Example. In addition, in the manufacturing method of the optical filter of the following Examples and Comparative Examples, the optical filter 1 having the configuration shown in FIG. 1 was manufactured. An optical filter 1 shown in FIG. 1 includes a Si substrate 2 and an optical multilayer film 3 made of a Ge film and an HfO ₂ film formed on both the front and back surfaces of the Si substrate 2. The film thickness is about [μm]. The optical filter 1 is formed on the surface of the substrate 10 by heating a crucible 12 filled with a deposition material while irradiating the surface of the substrate 10 with an ion beam as shown in FIG. The ion beam assisted vapor deposition apparatus 13 was used.

Specifically, the Ge ion and the HfO ₂ filled crucible 12 are heated while irradiating an O ₂ (oxygen) ion beam from the RF ion beam gun 11 to form Ge on the surface of the substrate 10 attached to the rotating dome 14. A film and a HfO ₂ film are deposited. By forming a film with the ion beam assisted vapor deposition apparatus 13, it is possible to form a dense and highly durable film as compared with the PVD (Physical Vapor Deposition) method, and at a high film formation rate. Can be formed. Then, after forming the Ge film and the HfO ₂ film on the surface of the substrate 10, the substrate 10 is turned over and the same process is performed again to form the Ge film and the HfO ₂ film on the back surface of the substrate 10.

The film formation rates of the Ge film and the HfO ₂ film are detected by the quartz sensor 15 through the opening 14a of the rotating dome 14 and adjusted to have a predetermined size. Further, infrared light is irradiated from the infrared light source 16 toward the back surface of the substrate 10a disposed in the vicinity of the opening 14a of the rotating dome, and infrared light transmitted through the substrate 10a, the Ge film and the HfO ₂ film is detected by an infrared light sensor. The optical filter manufactured by detecting the light reflected by the back light of the substrate 10a by the visible light sensor 18 can be evaluated.

[Example 1]
In Example 1, an optical filter was manufactured by forming a Ge film and an HfO ₂ film on both the front and back surfaces of the substrate under the film formation conditions shown in Table 1 and Table 2 below. Specifically, in the first embodiment, as shown in Table 1, the ion energy in forming the HfO ₂ film on the back surface of the substrate than the ion energy in forming the HfO ₂ film on the surface of the substrate An optical filter was manufactured with a larger size.

[Example 2]
In Example 2, an optical filter was manufactured by forming a Ge film and an HfO ₂ film on the front and back surfaces of the substrate under the film forming conditions shown in Tables 1 and 2 below. Specifically, in Embodiment 2, as shown in Table 1, the transport ratio in forming the HfO ₂ film on the back surface of the substrate than the transport ratio in forming the HfO ₂ film on the surface of the substrate An optical filter was manufactured with a larger size. The transport ratio indicates a value obtained by dividing the number of ions reaching the substrate surface by the number of vapor deposition atoms reaching the substrate surface.

[Comparative Example 1]
In Comparative Example 1, an optical filter was manufactured by forming a Ge film and an HfO ₂ film on the front and back surfaces of the substrate under the film forming conditions shown in Tables 1 and 2 below. Specifically, in Comparative Example 1, as shown in Table 1, forming a Ge film and HfO ₂ film on the back surface of the film forming conditions and the substrate at the time of forming the Ge film and HfO ₂ film on the surface of the substrate An optical filter was manufactured under the same film forming conditions.

[Evaluation]
For the optical filters of Examples 1 and 2 and Comparative Example 1, the amount of warpage of the substrate before vapor deposition, after surface vapor deposition, and after attachment on the back surface was evaluated. The evaluation results are shown in FIG. As shown in FIG. 3, for the optical filter of Comparative Example 1, the substrate was greatly warped after vapor deposition of the optical multilayer film on the back surface, but for the optical filters of Examples 1 and 2, the optical multilayer film was formed on the back surface. The substrate was not greatly warped after the deposition. Therefore, by making the ion energy and / or transport ratio when forming the optical multilayer film on the substrate surface different from the ion energy and / or transport cost when forming the optical multilayer film on the back surface of the substrate, It was found that the warp can be suppressed and the optical filter can be manufactured with a high yield.

The inventors of the present invention measured the change in internal stress of the HfO ₂ film accompanying the change in ion energy, and as a result, as shown in FIGS. 4 (a) and 4 (b), the internal stress of the HfO ₂ film was Although it decreased greatly with the increase of ion energy, it was found that precise control was difficult. Further, as a result of measuring the change in the internal stress of the HfO ₂ film accompanying the change in the transport ratio, as shown in FIGS. 5A and 5B, the internal stress of the HfO ₂ film does not change greatly as the transport ratio increases. However, it was found that precise control is possible compared to when ion energy is changed. From the above, increasing the ion energy and / or transport ratio in forming the HfO ₂ film on the back surface of the substrate than ion energy and / or transport ratio in forming the HfO ₂ film on the surface of the substrate Thus, the internal stress of the optical multilayer film formed on the surface of the substrate can be balanced with the internal stress of the optical multilayer film formed on the back surface of the substrate. Further, when strictly balancing the internal stress of the optical multilayer film on the substrate surface side and the internal stress of the optical multilayer film on the substrate back side, it is desirable to control both the ion energy and the transport ratio based on the above knowledge.

As mentioned above, although the embodiment to which the invention made by the present inventors was applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. For example, in the above embodiment, the ion energy and transport ratio when the HfO ₂ film is formed are changed, but the ion energy and transport ratio when the Ge film is formed may be changed. Moreover, although the board | substrate 2 was flat plate shape, it can apply also to the board | substrate with which unevenness | corrugation was provided intentionally, such as a convex lens, a concave lens, and a Fresnel lens. As described above, it is a matter of course that all other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are included in the scope of the present invention.

It is sectional drawing which shows the structure of the optical filter used as embodiment of this invention. It is a schematic diagram which shows the structure of the ion beam assist vapor deposition apparatus used when manufacturing the optical filter shown in FIG. The result of having evaluated the curvature amount of the board | substrate before vapor deposition, after surface state attachment, and after back surface vapor deposition about the optical filter of Examples 1, 2 and Comparative Example 1 is shown. It is a graph showing changes in the internal stress of the HfO ₂ film with changes in ion energy. It is a graph showing changes in the internal stress of the HfO ₂ film with changes in transport ratio.

Explanation of symbols

1: Optical filter 2: Substrate 3: Optical multilayer film

Claims (3)

A method for producing an optical filter having an optical multilayer film on both sides of a substrate,
A first step of forming the optical multilayer film on one surface of the substrate under a first ion beam irradiation condition using an ion beam assisted deposition method;
A second step of forming the optical multilayer film on the other surface of the substrate under the second ion beam irradiation condition using the ion beam assisted deposition method after the completion of the first step;
The first and second ion beam irradiation conditions are set so that the internal stress of the optical multilayer film formed on one surface of the substrate is balanced with the internal stress of the optical multilayer film formed on the other surface of the substrate. A method for producing an optical filter, characterized in that the method is controlled.   The method for manufacturing an optical filter according to claim 1, wherein ion energy when forming the optical multilayer film on one surface of the substrate and ion energy when forming the optical multilayer film on the other surface of the substrate are determined. Producing an optical filter characterized by balancing the internal stress of the optical multilayer film formed on one surface of the substrate with the internal stress of the optical multilayer film formed on the other surface of the substrate Method.   3. The method of manufacturing an optical filter according to claim 1, wherein the ion beam transport ratio when forming the optical multilayer film on one surface of the substrate and the optical multilayer film on the other surface of the substrate. The internal stress of the optical multilayer film formed on one surface of the substrate is balanced with the internal stress of the optical multilayer film formed on the other surface of the substrate by changing the transport ratio of the ion beam of the substrate. An optical filter manufacturing method characterized by the above.

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