JP4876595B2 - Infrared filter and manufacturing method thereof - Google Patents

Description

  The present invention relates to an infrared filter suitable for application to a sensor for detecting an object such as a human body or an animal, and a method for manufacturing the same.

2. Description of the Related Art Conventionally, an infrared filter that transmits only light in the infrared wavelength region by using a light interference phenomenon at each interface of multilayered films is known (see Patent Document 1).
JP 2004-317701 A

  However, since the conventional infrared filter uses ZnS (zinc sulfide) in a part of the multilayer film structure, it is necessary to provide a dedicated film forming chamber in order to avoid a bad odor generated during film formation, Handling at the time of manufacture and disposal was difficult.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an infrared filter that can be easily handled at the time of manufacture and disposal and a method for manufacturing the same.

In order to solve the above-described problems, an infrared filter according to the present invention includes a substrate that transmits infrared rays, and Ge films and HfO ₂ films that are alternately laminated on the substrate surface. The HfO ₂ film is (111). It has a crystal structure oriented in a plane direction mainly having a plane or a (−111) plane. The infrared filter manufacturing method according to the present invention includes a step of alternately stacking Ge films and HfO ₂ films on a substrate surface that transmits infrared rays using an ion beam assisted deposition method, and an HfO ₂ film ( A step of adjusting the ion acceleration voltage so as to have a crystal structure oriented in a plane direction mainly having a (111) plane or a (−111) plane.

According to the infrared filter and the manufacturing method thereof according to the present invention, since ZnS is not used when forming the multilayer structure, the infrared filter can be easily handled at the time of manufacturing and disposal. In addition, according to the infrared filter and the manufacturing method thereof according to the present invention, the HfO ₂ film has a crystal structure oriented in the plane direction mainly having the (111) plane or the (−111) plane, and thus the Ge film and the HfO ₂ film. The adhesion strength of the film is increased, and a high-strength infrared filter can be provided.

  Hereinafter, with reference to the drawings, a configuration of an infrared filter according to an embodiment of the present invention and a manufacturing method thereof will be described in detail.

[Configuration of infrared filter]
As shown in FIG. 1, an infrared filter 1 according to an embodiment of the present invention includes a substrate 2 that transmits infrared rays, a Ge film (germanium film) and an HfO ₂ film (hafnium) that are alternately laminated on the surface of the substrate 2. Oxide film).

[Infrared filter manufacturing method]
The infrared filter 1 is formed by heating a crucible 12 filled with a vapor deposition material while irradiating an ion beam from an RF ion beam gun 11 as shown in FIG. It is manufactured by an ion beam assisted vapor deposition apparatus 13 that forms a film thereon. Specifically, when a Ge film is formed on the surface of the substrate 2, the crucible 12 is heated while irradiating an Ar (argon) ion beam from the RF ion beam gun 11, so that Ge is formed on the surface of the substrate 2. Evaporate. Further, when the HfO ₂ film is formed on the surface of the substrate 2, the crucible 12 is heated while irradiating the O ₂ (oxygen) ion beam from the RF ion beam gun 11, whereby HfO ₂ is formed on the surface of the substrate 2. Evaporate. The film formation rate of each film is detected by the quartz sensor 14 and adjusted to a predetermined size. Then, infrared light is irradiated from the infrared light source 15 toward the back surface of the substrate 2, the infrared light transmitted through the substrate 2 and the multilayer film is detected by the infrared light sensor 16, and the visible light sensor 17 detects the infrared light of the substrate 2. The performance of the manufactured infrared filter 1 is evaluated by the optical sensor 18 that detects the light reflected on the back surface.

The refractive index of light in the multilayer film formed on the surface of the substrate 2 can be controlled by adjusting the irradiation conditions of the ion beam from the RF ion beam gun 11, in other words, the transport ratio. The “transport ratio” indicates a value obtained by dividing the number of ions reaching the surface of the substrate 2 by the number of vapor deposition atoms reaching the surface of the substrate 2. Specifically, when adjusting the refractive index of light in the HfO ₂ film, the transport ratio is changed with the substrate temperature fixed at 300 [° C.] and the vapor deposition rate at 2.0 [Å / sec]. Thus, as shown in FIG. 3, the refractive index of light in the HfO ₂ film can be adjusted in the range of 1.99 to 2.89. When the refractive index of light in the HfO ₂ film is 2.04 or less, the multilayer film is a tape test (a commercially available cello tape (registered trademark) is applied to the film surface and pulled with a constant force in the surface vertical direction. Therefore, by evaluating whether or not the film is peeled off, the test for examining the adhesion between the Ge film and the HfO ₂ film) was not passed, so that the refractive index of light in the HfO ₂ film is 2.06 or more. It is desirable.

When the ion acceleration voltage is changed in the range of 700 to 1000 [V] while the substrate temperature is fixed at 300 [° C.] and the deposition rate is fixed at 2.0 [Å / sec], FIG. ) When the ion acceleration voltage is 900 [V] or higher, the HfO ₂ film has a crystal structure in which the (111) plane and the (−111) plane are mainly oriented in the plane direction. It was found that when the ion acceleration voltage was 900 [V] or less, the HfO ₂ film had a crystal structure oriented in the plane direction mainly composed of the (002) plane. And when the above-mentioned tape test was performed about the infrared filter manufactured by changing the ion acceleration voltage, the infrared filter manufactured with an ion acceleration voltage of 900 [V] or higher passed the tape test, whereas the ion acceleration voltage Infrared filter manufactured with a V value of 900 [V] or less failed the tape test. From this, the ion acceleration voltage is set to about 900 [V] or more, and the HfO ₂ film has a crystal structure oriented in the plane direction mainly composed of the (111) plane and the (−111) plane, whereby Ge It was found that an infrared filter having strong adhesion between the film and the HfO ₂ film can be produced.

As is clear from the above description, the infrared filter 1 according to an embodiment of the present invention includes a substrate 2 that transmits infrared rays, and Ge films and HfO ₂ films that are alternately laminated on the surface of the substrate 2. The HfO ₂ film has a crystal structure in which the (111) plane and the (−111) plane are oriented in the plane direction. And according to such a structure, since ZnS is not used when forming a multilayer film structure, handling of the infrared filter at the time of manufacture or disposal can be facilitated.

In addition, according to the infrared filter 1 according to the embodiment of the present invention, the HfO ₂ film has a crystal structure oriented in the plane direction mainly including the (111) plane and the (−111) plane, and therefore, the Ge film and the HfO ₂ film. It is possible to provide an infrared filter having high adhesion strength and high strength. Further, according to the infrared filter 1 according to the embodiment of the present invention, the Ge film and the HfO ₂ film are formed by the ion beam assisted vapor deposition method. Therefore, a dense multilayer film with good adhesion is formed by the ion collision effect. Can be membrane.

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, when forming a multilayer film, as shown in FIG. 5B, a metal mask such as Ni—Fe having a film thickness of about 50 μm is used as a mesh area R ( Effective diameter φ 90. The size of each mesh constituting the mesh area R may be masked as shown in FIG. According to such a configuration, dicing can be easily performed even with a hard film such as an HfO ₂ film. 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 infrared 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 infrared filter shown in FIG. It is a diagram illustrating a change in refractive index of light in the HfO ₂ film relative to the change in transport ratio. The X-ray diffraction diagram showing the change of the crystal orientation of the HfO ₂ film with respect to changes in the ion acceleration voltage. It is a figure which shows the dicing line masked by the board | substrate at the time of film-forming.

Explanation of symbols

1: Infrared filter 2: Substrate 11: RF ion gun 12: Crucible 13: Ion beam assisted deposition apparatus 14: Crystal sensor 15: Infrared light source 16: Infrared light sensor 17: Visible light sensor 18: Optical monitor 21: Si wafer R: Mesh area

Claims (2)

A substrate that transmits infrared light;
Comprising Ge films and HfO ₂ films alternately stacked on the substrate surface;
_{2. The} infrared filter according to claim 1, wherein the HfO ₂ film has a crystal structure oriented in a plane direction mainly having a (111) plane or a (−111) plane. A step of alternately laminating a Ge film and an HfO ₂ film on a substrate surface that transmits infrared rays using an ion beam assisted deposition method;
Adjusting the ion accelerating voltage so that the HfO ₂ film has a crystal structure oriented in a plane direction mainly having a (111) plane or a (−111) plane.

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